Optical phased array dynamic beam shaping with noise correction

Abstract

To provide a system and a method for noise correction and phase correction in dynamically shaped beams produced by a laser beam phased array.SOLUTION: A laser system comprises: a seed laser which is an optical phased array laser; and a laser beam splitting and combining subsystem receiving laser output from the seed laser and providing a combined laser output. The laser beam splitting and combining subsystem varies the phase of the combined laser output and focuses the combined laser output onto the substrate, and the combined laser output is not focused onto a substrate when there is no phase variation in the combined laser output.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS Israeli Patent Application No. 255496, entitled "OPTICAL PHASED ARRAY DYNAMIC BEAM SHAPING WITH NOISE CORRECTION," filed November 7, 2017; Israeli Patent Application No. 256107, entitled "SEED LASER FAILURE PROTECTION SYSTEM," filed December 4, 2017; U.S. Provisional Patent Application No. 62 / 594,167, entitled "LASER BACK-REFLECTION PROTECTION USING OPTICAL PHASED ARRAY LASER," filed December 4, 2017; and U.S. Provisional Patent Application No. 62 / 594,167, entitled "SCALED PHASE MODIFICATION, PHASE CALIBRATION AND SEED LASER PROTECTION IN OPTICAL PHASED ARRAY LASER," filed April 25, 2018.

[0013] Israel Patent Application No. 258936, entitled "MULTIPLE DETECTORS AND CORRESPONDING MULTIPLE CLOSELY SPACED OPTICAL PATHWAYS IN OPTICAL PHASED ARRAY LASER," filed June 13, 2018; U.S. Provisional Patent Application No. 62 / 684,341, entitled "DETECTOR MASK IN OPTICAL PHASED ARRAY LASER," filed July 28, 2018; and U.S. Provisional Patent Application No. 62 / 702,957, filed July 28, 2018, entitled "DETECTOR MASK IN OPTICAL PHASED ARRAY LASER," the entire disclosures of which are incorporated herein by reference, and the priority of all of which is hereby claimed pursuant to 37 CFR 1.78(a)(4) and (5)(i).

[0002] See also US Pat. No. 9,893,494, the disclosure of which is incorporated herein by reference.

[0003] The present invention relates generally to laser coherent beam combining, and more particularly to optical phased arrays. [Background technology]

[0004] Various types of optical phased arrays are known in the art. Summary of the Invention

[0005] The present invention aims to provide a system and method for noise compensation and phase correction in dynamically shaped beams generated by laser optical phased arrays.

[0006] Therefore, in accordance with a preferred embodiment of the present invention, there is provided a laser system including a seed laser, a laser beam splitting and combining subsystem that receives an output from the seed laser and provides a combined laser output having noise, and a noise cancellation subsystem that operates to provide a noise-canceled phase-corrected output based on accounting for the noise at the intermittent times, wherein the laser beam splitting and combining subsystem modifies the phase of the combined laser output during time intervals between the intermittent times.

[0007] In accordance with another preferred embodiment of the present invention, there is further provided a laser system including: a seed laser; a laser beam splitting and combining subsystem that receives an output from the seed laser and provides a combined laser output having noise; and a noise cancellation subsystem that operates to provide a noise-canceled phase-corrected output based on considering the noise at the noise sampling rate, wherein the laser beam splitting and combining subsystem modifies the phase of the combined laser output at a phase modification rate that exceeds the noise sampling rate.

[0008] Preferably, at least one of the noise sampling rate and the phase modification rate varies over time.

[0009] Preferably, the noise sampling rate is predetermined.

[0010] In accordance with a preferred embodiment of the present invention, the laser beam splitting and combining subsystem alters the phase of the combined laser output to provide spatial modulation of the combined laser output.

[0011] Preferably, spatial modulation of the combined laser output is provided in combination with mechanical spatial modulation of the combined laser output, the spatial modulation combined with the mechanical spatial modulation being faster than the mechanical spatial modulation in the absence of the spatial modulation.

[0012] Additionally or alternatively, spatial modulation of the combined laser output is provided in combination with mechanical spatial modulation of the combined laser output, the spatial modulation combined with the mechanical spatial modulation being more precise than the mechanical spatial modulation in the absence of the spatial modulation.

[0013] Preferably, the spatial modulation includes modulation of at least one of the shape and diameter of the combined laser output.

[0014] Preferably, the laser beam splitting and combining subsystem provides laser beam amplification downstream of the splitting and upstream of the combining.

[0015] According to a further preferred embodiment of the present invention, the noise cancellation phase corrected output is calculated based on sequentially applying at least two phase changes to at least one constituent beam of the combined laser output and identifying one of the at least two phase changes that corresponds to a maximum output intensity of the at least one constituent beam.

[0016] Preferably, the system also includes at least one detector cooperatively coupled with the noise cancellation subsystem for detecting at least a portion of the combined laser output.

[0017] Preferably, at least one detector performs detection continuously.

[0018] In accordance with an additional preferred embodiment of the present invention, the noise-canceling phase-corrected output cancels intensity noise in the combined laser output.

[0019] Preferably, the system also includes at least one intensity modulator for varying the intensity of the combined laser output.

[0020] In accordance with still additional preferred embodiments of the present invention, the noise-canceling phase corrected output cancels position noise in the combined laser output.

[0021] Preferably, the system also includes at least one position modulator for varying the position of the combined laser output.

[0022] Preferably, the laser cutting system comprises the laser system of the present invention.

[0023] Additionally or alternatively, the laser additive manufacturing system includes the laser system of the present invention.

[0024] Also additionally or alternatively, the laser welding system includes the laser system of the present invention.

[0025] Additionally or alternatively, a free space optical communication system includes the laser system of the present invention.

[0026] In accordance with another preferred embodiment of the present invention, there is also provided a method for performing noise correction on a phase-altered laser output, the method including receiving output from a seed laser, splitting and combining the output to provide a combined laser output having noise, applying a noise-canceling phase correction output to the combined laser output based on accounting for noise at the intermittent times, and altering the phase of the combined laser output during time intervals between the intermittent times.

[0027] In accordance with another preferred embodiment of the present invention, there is further provided a method for performing noise correction on a phase-altered laser output, the method including receiving an output from a seed laser, splitting and combining the output to provide a combined laser output having noise, applying a noise-canceling phase correction output to the combined laser output based on accounting for noise at a noise sampling rate, and altering the phase of the combined laser output at a phase alteration rate that exceeds the noise sampling rate.

[0028] Preferably, at least one of the noise sampling rate and the phase modification rate varies over time.

[0029] Preferably, the noise sampling rate is predetermined.

[0030] According to a preferred embodiment of the present invention, the phase modification provides spatial modulation of the combined laser output.

[0031] Preferably, spatial modulation of the combined laser output is provided in combination with mechanical spatial modulation of the combined laser output, wherein the spatial modulation combined with the mechanical spatial modulation is faster than the mechanical spatial modulation in the absence of the spatial modulation.

[0032] Additionally or alternatively, spatial modulation of the combined laser output is provided in combination with mechanical spatial modulation of the combined laser output, where the spatial modulation combined with the mechanical spatial modulation is more precise than the mechanical spatial modulation in the absence of the spatial modulation.

[0033] Preferably, the spatial modulation includes modulation of at least one of the shape and diameter of the combined laser output.

[0034] Preferably, the method also includes amplifying the output downstream of the splitting and upstream of the combining.

[0035] In accordance with another preferred embodiment of the present invention, the method also includes calculating a noise cancellation phase correction output based on sequentially applying at least two phase changes to at least one constituent beam of the combined laser output and identifying one phase change of the at least two phase changes that corresponds to a maximum output intensity of the at least one constituent beam.

[0036] Preferably, the method also includes detecting at least a portion of the combined laser output.

[0037] Preferably, the detection is carried out continuously.

[0038] In accordance with yet another preferred embodiment of the present invention, the noise-canceling phase-corrected output cancels intensity noise in the combined laser output.

[0039] Preferably, the method also includes modulating the intensity of the output downstream of the splitting and upstream of the combining.

[0040] In accordance with yet another preferred embodiment of the present invention, the noise-canceling phase-corrected output cancels position noise in the combined laser output.

[0041] Preferably, the method also includes modulating the position of the output downstream of the split and upstream of the combine.

[0042] Preferably, the method for laser cutting comprises the method of the present invention.

[0043] Additionally or alternatively, methods for additive manufacturing include the methods of the present invention.

[0044] Additionally or alternatively, methods for laser welding include the method of the present invention.

[0045] Still further additionally or alternatively, a method for free space optical communication includes the method of the present invention.

[0046] In accordance with another preferred embodiment of the present invention, there is also provided a laser system including: a seed laser; a laser beam splitting and combining subsystem that receives output from the seed laser(s) and provides a combined laser output, wherein the laser beam splitting and combining subsystem alters a phase of the combined laser output; a plurality of detectors that detect the combined laser output at discrete times while altering the phase of the combined laser output; and a plurality of optical paths between the combined laser output and the plurality of detectors, the plurality of optical paths for providing the combined laser output along the plurality of optical paths to the plurality of detectors, wherein a spatial density of the plurality of optical paths is greater than a spatial density of the plurality of detectors.

[0047] Preferably, the combined laser output has noise, and the laser system also includes a noise cancellation subsystem operative to provide a noise-canceled phase-corrected output based on accounting for noise in the combined laser output detected by the plurality of detectors at intermittent times during the modification of the phase of the combined laser output.

[0048] Preferably, the plurality of optical paths includes a plurality of optical fibers, the ends of the optical fibers being arranged at a spatial density greater than the spatial density of the plurality of detectors.

[0049] Preferably, the plurality of optical paths are spaced apart by a distance of 20 to 1000 microns.

[0050] Preferably, the detectors among the plurality of detectors are spaced apart by a distance of 5 to 50 mm.

[0051] In accordance with another preferred embodiment of the present invention, there is additionally provided a method for detecting laser output, the method including receiving output from a seed laser; splitting and combining the output to provide a combined laser output; altering the phase of the combined laser output; and providing the combined laser output to a plurality of detectors along a plurality of optical paths, wherein the spatial density of the plurality of optical paths is greater than the spatial density of the plurality of detectors.

[0052] Preferably, the combined laser output has noise, and the method also includes providing a noise-canceled phase-corrected output based on taking into account noise in the combined laser output detected by the plurality of detectors during the alteration of the phase of the combined laser output.

[0053] Preferably, the plurality of optical paths includes a plurality of optical fibers, the ends of the optical fibers being arranged at a spatial density greater than the spatial density of the plurality of detectors.

[0054] Preferably, the plurality of optical paths are spaced apart by a distance of 20 to 1000 microns.

[0055] Preferably, the detectors among the plurality of detectors are spaced apart by a distance of 5 to 50 mm.

[0056] In accordance with yet another preferred embodiment of the present invention, there is further provided a laser system including: a seed laser; a laser beam splitting and combining subsystem that receives output from the seed laser(s) and provides a combined laser output, wherein the laser beam splitting and combining subsystem alters a phase of the combined laser output; at least one detector that detects the combined laser output while altering the phase of the combined laser output; and an optical mask including at least one of a transmissive region and a reflective region for providing the combined laser output through and from the at least one of the transmissive region and the reflective region, respectively, to the at least one detector.

[0057] Preferably, at least one of the transmissive and reflective regions is configured according to at least one of the shape and trajectory of the coupled laser output.

[0058] Preferably, the system also includes a focusing subsystem that interfaces the optical mask and the at least one detector for focusing the combined laser output onto the at least one detector.

[0059] Preferably, the focusing subsystem includes at least one focusing lens.

[0060] Preferably, the at least one detector comprises a single detector.

[0061] According to a preferred embodiment of the present invention, the transmissive areas have non-uniform transparency.

[0062] Preferably, the non-uniform transparency of the transmissive region compensates for non-noise related non-uniformities in the intensity of the coupled laser output.

[0063] Preferably, the optical mask comprises an electrically modulated device, and at least one of the transmissive and reflective regions is electronically modifiable.

[0064] Preferably, the optical mask comprises an LCD screen.

[0065] According to another preferred embodiment of the present invention, the reflective area has a non-uniform reflectivity.

[0066] Preferably, the non-uniform reflectivity of the reflective region compensates for non-noise related non-uniformities in the intensity of the coupled laser output.

[0067] Preferably, the reflective area includes a DMM.

[0068] Preferably, the combined laser output has noise, and the laser system also includes a noise cancellation subsystem that operates to provide a noise-canceled phase-corrected output based on taking into account the noise in the combined laser output detected by the at least one detector during the alteration of the phase of the combined laser output.

[0069] In accordance with still further preferred embodiments of the present invention, there is further provided a method for detecting laser output, the method comprising: receiving output from seed lasers; splitting and combining the output to provide a combined laser output; altering a phase of the combined laser output; providing the combined laser output to at least one detector by an optical mask including at least one of transmissive and reflective regions for providing the combined laser output through and from the at least one of the transmissive and reflective regions, respectively, to the at least one detector; and detecting the combined laser output during the alteration of phase by the at least one detector.

[0070] Preferably, at least one of the transmissive and reflective regions is configured according to at least one of the shape and trajectory of the coupled laser output.

[0071] Preferably, the method also includes focusing the combined laser output onto at least one detector.

[0072] Preferably, the method also includes providing a focusing lens interfacing the optical mask and the at least one detector to perform the focusing.

[0073] Preferably, the at least one detector comprises a single detector.

[0074] According to a preferred embodiment of the present invention, the transmissive areas have non-uniform transparency.

[0075] Preferably, the non-uniform transparency of the transmissive region compensates for non-noise related non-uniformities in the intensity of the coupled laser output.

[0076] Preferably, the optical mask comprises an electrically modulated device, and at least one of the transmissive and reflective regions is electronically modifiable.

[0077] Preferably, the optical mask comprises an LCD screen.

[0078] According to another preferred embodiment of the present invention, the reflective area has a non-uniform reflectivity.

[0079] Preferably, the non-uniform reflectivity of the reflective region compensates for non-noise related non-uniformities in the intensity of the coupled laser output.

[0080] Preferably, the reflective area includes a DMM.

[0081] Preferably, the combined laser output has noise, and the method also includes providing a noise-canceled phase-corrected output based on taking into account noise in the combined laser output detected by the at least one detector during the alteration of the phase of the combined laser output.

[0082] In accordance with yet another preferred embodiment of the present invention, there is also provided a laser system including: a seed laser; a laser splitting and combining subsystem that receives output from the seed lasers and combines the output to provide a combined laser output; a phase modulation subsystem for altering the phase of the combined laser output; and a voltage-to-phase correlation subsystem for correlating a voltage applied to the phase modulation subsystem with the phase modulated output produced by the phase modulation subsystem and providing a voltage-to-phase correlation output useful for calibrating the phase modulation subsystem, wherein the correlation is performed periodically while the phase is being changed.

[0083] Preferably, the phase modulation subsystem includes a plurality of phase modulators.

[0084] Preferably, the voltage is applied to the plurality of phase modulators by a phase modulation control module.

[0085] Preferably, the voltages include voltages intended to produce a phase shift of the combined laser outputs of 2π.

[0086] Preferably, the correlation includes measuring a change in intensity of the far-field intensity pattern of the combined laser output after application of a voltage, and deriving a relationship between voltage and a phase shift corresponding to the change in intensity.

[0087] Preferably, the voltage is applied sequentially to the phase modulators of the plurality of phase modulators.

[0088] Preferably, the correlation is performed at a rate slower than the phase change.

[0089] Preferably, the phase changes are performed at a rate of 1 million times per second and the correlation is performed at a rate of 1 time per second.

[0090] In accordance with additionally preferred embodiments of the present invention, there is additionally provided a method for performing phase calibration of a laser system, the method including receiving output from seed lasers; splitting and combining the output to provide a combined laser output; varying the phase of the combined laser output by a phase modulation subsystem; periodically during the phase variation, applying a voltage to the phase modulation subsystem and correlating the voltage with the phase modulated output produced by the phase modulation subsystem; and providing a voltage versus phase correlation output useful for calibrating the phase modulation subsystem.

[0091] Preferably, the phase modulation subsystem includes a plurality of phase modulators.

[0092] Preferably, the application of the voltage is performed by a phase modulation control module.

[0093] Preferably, the voltages include voltages intended to produce a phase shift of the combined laser outputs of 2π.

[0094] Preferably, the correlation includes measuring a change in intensity of the far-field intensity pattern of the combined laser output after application of a voltage, and deriving a relationship between voltage and a phase shift corresponding to the change in intensity.

[0095] Preferably, the method also includes sequentially applying a voltage to a phase modulator of the plurality of phase modulators.

[0096] Preferably, the correlation is performed at a rate slower than the phase change.

[0097] Preferably, the phase changes are performed at a rate of 1 million times per second and the correlation is performed at a rate of 1 time per second.

[0098] In accordance with another preferred embodiment of the present invention, there is also provided a laser system including: a seed laser; a laser beam splitting and combining subsystem that receives output from the seed laser, splits the output into a plurality of sub-beams, and provides a combined laser output including the plurality of sub-beams; and a phase modulation subsystem that groups at least a portion of the plurality of sub-beams into multiple groups of sub-beams, wherein the phase modulation subsystem changes the phase of each sub-beam in each group relative to the phases of the other sub-beams in the group in parallel across the multiple groups of sub-beams to change the phase of each group, and changes the phase of each group relative to the phases of other groups in the multiple groups, thereby changing the phase of the combined laser output.

[0099] Preferably, the phase modulation subsystem includes at least one cylindrical lens for performing the grouping.

[0100] Alternatively, the phase modulation subsystem includes an array of mirrors and corresponding focusing lenses to implement the grouping.

[0101] Preferably, the phase modulation subsystem includes a plurality of phase modulators for modifying the phases of the sub-beams.

[0102] Preferably, the phase modulation subsystem includes at least one electronic control module in operational control of the plurality of phase modulators.

[0103] Preferably, the phase modulation subsystem includes multiple detectors corresponding to the multiple groups for detecting the far-field intensity pattern of each of the multiple groups.

[0104] In accordance with a preferred embodiment of the present invention, the system also includes a number of optical masks masking corresponding detectors of the number of detectors, each optical mask including at least one of a transmissive region and a reflective region, for respectively providing the far-field intensity pattern through and from the at least one of the transmissive region and the reflective region to a corresponding detector of the number of detectors.

[0105] Preferably, the multiple detectors perform detection at least partially simultaneously with each other.

[0106] Preferably, the phase modulation subsystem includes an additional auxiliary detector for detecting the combined far-field intensity patterns of multiple groups.

[0107] Preferably, the phase modulation subsystem includes a number of additional phase modulators, each additional phase modulator common to all sub-beams in each group for modifying the phase of each group relative to the phase of the other groups in the number of groups.

[0108] Preferably, the phase modulation subsystem includes an additional electronic control module in operational control of a number of additional phase modulators.

[0109] In accordance with another preferred embodiment of the present invention, each detector of the multiple detectors includes a plurality of detectors.

[0110] Preferably, the system also includes a plurality of optical paths between each of the far-field intensity patterns of the multiple groups and each of the plurality of detectors, for providing the far-field intensity patterns along the plurality of optical paths to the plurality of detectors, wherein the spatial density of the plurality of optical paths is greater than the spatial density of the plurality of detectors.

[0111] Preferably, modifying the phase of the combined laser output comprises maximizing the intensity of the combined laser output.

[0112] Preferably, altering the phase of the combined laser output provides spatial modulation of the combined laser output without mechanical spatial modulation of the combined laser output.

[0113] Preferably, the laser beam splitting and combining subsystem provides laser beam amplification downstream of the splitting and upstream of the combining.

[0114] In accordance with yet another preferred embodiment of the present invention, there is further provided a method for performing phase modification of a laser output, the method including: receiving laser output from a seed laser; splitting the laser output into a plurality of sub-beams and combining the plurality of sub-beams to provide a combined laser output; grouping at least a portion of the sub-beams of the plurality of sub-beams into multiple groups of sub-beams; modifying the phase of each sub-beam in each group relative to the phases of the other sub-beams in the group in parallel across the multiple groups of sub-beams to modify the phase of each group; and modifying the phase of each group relative to the phases of the other groups of the multiple groups, thereby modifying the phase of the combined laser output.

[0115] Preferably, the grouping is performed by at least one cylindrical lens.

[0116] Alternatively, the grouping is performed by an array of mirrors and corresponding focusing lenses.

[0117] Preferably, the modification of the phases of the sub-beams is performed by a plurality of phase modulators.

[0118] Preferably, the method also includes controlling the plurality of phase modulators by at least one electronic control module.

[0119] Preferably, the method also includes detecting the far field intensity pattern of each of the multiple groups by a corresponding multiple detector.

[0120] According to a preferred embodiment of the present invention, the method includes providing a far-field intensity pattern to a corresponding detector among the multiple detectors by a number of optical masks, each optical mask including at least one of a transmissive region and a reflective region, and for providing the far-field intensity pattern through and from the at least one of the transmissive region and the reflective region to a corresponding detector among the multiple detectors, respectively.

[0121] Preferably, detection is performed for multiple groups at least partially simultaneously with each other.

[0122] Preferably, the method also includes detecting, by an auxiliary detector, the combined far-field intensity patterns of the multiple groups.

[0123] Preferably, the modification of the phase of each group relative to the phase of the other groups of multiple groups is performed by multiple additional phase modulators, each additional phase modulator being common to all sub-beams within each group.

[0124] Preferably, the method also includes controlling a number of additional phase modulators by additional electronic control modules.

[0125] In accordance with another preferred embodiment of the present invention, each detector of the multiple detectors includes a plurality of detectors.

[0126] Preferably, the method also includes providing the far field intensity pattern of each of the multiple groups to a respective one of a plurality of detectors along a plurality of optical paths, the spatial density of the plurality of optical paths being greater than the spatial density of the plurality of detectors.

[0127] Preferably, modifying the phase of the combined laser output comprises maximizing the intensity of the combined laser output.

[0128] Preferably, altering the phase of the combined laser output provides spatial modulation of the combined laser output without mechanical spatial modulation of the combined laser output.

[0129] Preferably, the method also includes amplifying the laser output downstream of the splitting and upstream of the combining.

[0130] In accordance with another preferred embodiment of the present invention, there is also provided a laser system comprising an optical phased array laser including seed lasers and a laser beam splitting and combining subsystem that receives output from the seed lasers and provides a combined laser output, wherein the laser beam splitting and combining subsystem alters a phase of the combined laser output to focus the combined laser output at a substrate, and wherein the combined laser output would not be focused at the substrate in the absence of the phase alteration.

[0131] Preferably, the system also includes an optical element that receives the combined laser output from the laser beam splitting and combining subsystem and focuses the combined laser output to a focal point that is not coincident with the substrate.

[0132] Preferably, the laser beam backscattered from the substrate is not focused into the optical phased array laser.

[0133] In accordance with yet another preferred embodiment of the present invention, there is still further provided a method for focusing a laser beam in a laser system, the method including receiving laser output from a seed laser; splitting and combining the laser output to provide a combined laser output; and altering a phase of the combined laser output to focus the combined laser output at a substrate, wherein the combined laser output would not be focused at the substrate in the absence of the phase alteration.

[0134] Preferably, the method also includes focusing, by an optical element, the combined laser output to a focal point that is not coincident with the substrate.

[0135] Preferably, the laser beam backscattered from the substrate is not focused onto the laser system.

[0136] In accordance with yet additionally preferred embodiments of the present invention, there is additionally provided a laser amplifier system including: a seed laser providing a laser output; an amplification subsystem receiving the laser output from the seed laser along a first optical path and providing an amplified laser output; and a detector subsystem receiving the laser output from the seed laser along a second optical path, the detector subsystem operative to deactivate the amplification subsystem upon detection of at least one fault in the laser output by the detector subsystem, wherein a first time-of-flight of the laser output from the seed laser along the first optical path to the amplification subsystem is greater than a combination of a second time-of-flight of the laser output from the seed laser to the detector subsystem along the second optical path and a time required by the detector subsystem to deactivate the amplification subsystem.

[0137] Preferably, the first optical path includes a coiled optical fiber.

[0138] Preferably, the at least one impairment includes at least one of a reduction in power of the laser output and a degradation in linewidth of the laser output.

[0139] Preferably, the amplification subsystem includes a power amplifier and the laser amplifier system includes a MOPA.

[0140] In accordance with yet additionally preferred embodiments of the present invention, there is still additionally provided a method for preventing damage to an amplification subsystem in a laser system, the method comprising: receiving laser output from a seed laser along a first optical path; amplifying the laser output to provide an amplified laser output; receiving laser output from the seed laser along a second optical path; detecting at least one fault in the laser output received along the second optical path; and upon detection of the at least one fault in the laser output, stopping the amplification, wherein a first time-of-flight of the laser output along the first optical path is greater than a combination of a second time-of-flight of the laser output along the second optical path and a time required for the stopping of amplification to be performed.

[0141] Preferably, the first optical path includes a coiled optical fiber.

[0142] Preferably, the at least one impairment includes at least one of a reduction in power of the laser output and a degradation in linewidth of the laser output.

[0143] Preferably, the amplification subsystem includes a power amplifier and the laser amplifier system includes a MOPA.

[0144] In accordance with yet another preferred embodiment of the present invention, there is also provided a laser amplifier system including: a seed laser providing a laser output; a first amplifier arranged to receive the laser output from the seed laser, the first amplifier providing a first amplified laser output upon receiving the laser output from the seed laser and providing one of amplified spontaneous emission and an additional laser output upon cessation of receiving the laser output from the seed laser; and a second amplifier receiving one of the first amplified laser output, amplified spontaneous emission, and the additional laser output from the first amplifier and providing a second amplified laser output, the amplification provided by the second amplifier being greater than the amplification provided by the first amplifier.

[0145] Preferably, the system also includes a filter structure downstream of the seed laser and upstream of the first amplifier.

[0146] Preferably, the filter structure comprises a laser amplifier system including: a beam splitter that splits the laser output along first and second optical paths, the first optical path being longer than the second optical path; a detector that detects the combined laser output from the first and second optical paths; an electronic control module coupled to the detector for receiving output from the detector; and a phase control module positioned along one of the first and second optical paths, the phase control module operated by the electronic control module to modify the phase of the laser output in response to detection by the detector of interference in the combined laser output.

[0147] In accordance with still further preferred embodiments of the present invention, there is further provided a method for preventing damage to amplifiers in a laser system, the method including: receiving laser output from a seed laser; providing, by a first amplifier, a first amplified laser output upon receiving the laser output from the seed laser; providing, by the first amplifier, one of amplified spontaneous emission and an additional laser output upon cessation of receiving the laser output from the seed laser; and receiving and providing, by a second amplifier, one of the first amplified laser output, the amplified spontaneous emission, and the additional laser output, and providing a second amplified laser output, wherein the second amplified laser output is greater than the first amplified laser output.

[0148] Preferably, the method also includes filtering the laser output downstream of the seed laser and upstream of the first amplifier.

[0149] Preferably, the filtering includes splitting the laser output along first and second optical paths, the first optical path being longer than the second optical path; detecting the combined laser output from the first and second optical paths by a detector; receiving an output from the detector by an electronic control module; and modifying the phase of the laser output along one of the first and second optical paths in response to detection by the detector of interference in the combined laser output.

[0150] There is also provided in accordance with another preferred embodiment of the present invention a laser amplifier system including: a seed laser providing a first laser output having a first power; an amplification subsystem receiving the first laser output from the seed laser and providing an amplified laser output; and an auxiliary laser subsystem providing a second laser output at least upon termination of the first laser output, the second laser output having a second power lower than the first power.

[0151] Preferably, the auxiliary laser subsystem includes an additional seed laser that provides a second laser output to the amplification subsystem at least simultaneously with the provision of the first laser output.

[0152] Alternatively, the amplification subsystem includes an inlet through which the first laser output is received and an outlet through which the amplified laser output is provided, and the laser amplifier system includes a first reflective grating positioned at the inlet and a second reflective grating positioned at the outlet, the first and second reflective gratings being combined with the amplification subsystem including the auxiliary laser subsystem.

[0153] The first and second reflective gratings are reflective in the wavelength range of 1090 nm to 1100 nm.

[0154] Preferably, the second laser output has a different wavelength than the first laser output.

[0155] Preferably, the system also includes a filter downstream of the seed laser and upstream of the amplification subsystem.

[0156] Preferably, the filter includes a beam splitter that splits the first laser output along a first optical path and a second optical path, the first optical path being longer than the second optical path; a detector that detects the combined laser output from the first and second optical paths; an electronic control module coupled to the detector for receiving output from the detector; and a phase control module positioned along one of the first and second optical paths, the phase control module operated by the electronic control module to modify the phase of the first laser output in response to detection by the detector of interference in the combined laser output.

[0157] Preferably, the system also includes a detector subsystem for detecting the first laser output from the seed laser.

[0158] Preferably, the detector subsystem includes a splitter that splits the first laser output into a first portion and a second portion, an additional amplifier that amplifies the second portion and provides an amplified output, and an optical fiber that receives the amplified output, the optical fiber being configured to exhibit nonlinear effects when the linewidth of the first laser output becomes unacceptably narrow.

[0159] Preferably, the optical fiber has a length of 25 m and a core diameter of 6 microns.

[0160] According to another preferred embodiment of the present invention, there is still additionally provided a method for preventing damage to an amplifier in a laser system, the method comprising: providing a first laser output having a first power; amplifying the first laser output with the amplifier to provide an amplified laser output; and providing a second laser output at least upon cessation of providing the first laser output, the second laser output having a second power that is lower than the first power.

[0161] Preferably, the provision of the second laser output is performed at least simultaneously with the provision of the first laser output.

[0162] Preferably, the amplifier includes an inlet at which the first laser output is received and an outlet at which an amplified laser output is provided, and also includes positioning a first reflective grating at the inlet and a second reflective grating at the outlet, the first and second reflective gratings being combined with the amplifier to provide the second laser output.

[0163] Preferably, the first and second reflective gratings are reflective in the wavelength range of 1090 nm to 1100 nm.

[0164] Preferably, the second laser output has a different wavelength than the first laser output.

[0165] Preferably, the method also includes filtering the first laser output upstream of the amplification of the first laser output.

[0166] Preferably, the method includes splitting a first laser output along first and second optical paths, the first optical path being longer than the second optical path; detecting the combined laser output from the first and second optical paths by a detector; receiving, by an electronic control module, an output from the detector; and modifying the phase of the first laser output along one of the first and second optical paths based on the output from the detector and in response to detection by the detector of interference in the combined laser output.

[0167] Preferably, the method also includes detecting the first laser output.

[0168] Preferably, the detecting includes splitting the first laser output into a first portion and a second portion, amplifying the second portion and providing an amplified output, and receiving the amplified output by an optical fiber, the optical fiber configured to exhibit nonlinear effects when the linewidth of the first laser output becomes unacceptably narrow.

[0169] Preferably, the optical fiber has a length of 25 m and a core diameter of 6 microns. [Brief explanation of the drawings]

[0170] The present invention will be more fully understood and appreciated based on the following detailed description taken in conjunction with the drawings. [Figure 1A] FIG. 1 is a simplified schematic diagram of an optical phased array laser system for noise-compensated dynamic beam shaping, constructed and operative in accordance with a preferred embodiment of the present invention; [Figure 1B-1C] 1B is a simplified graphical representation of phase modification and noise correction in a system of the type shown in FIG. 1A. [Figure 2A] FIG. 1 is a simplified schematic diagram of an optical phased array laser system for noise-compensated dynamic beam shaping, constructed and operative in accordance with another preferred embodiment of the present invention; [Figure 2B-2C] 2B is a simplified graphical representation of phase modification and noise correction in a system of the type shown in FIG. 2A. [Figure 3A] FIG. 1 is a simplified schematic diagram of an optical phased array laser system for noise-compensated dynamic beam shaping, constructed and operative in accordance with a further preferred embodiment of the present invention; [Figure 3B-3C] 3B is a simplified graphical representation of phase modification and noise correction in a system of the type shown in FIG. 3A. [Figure 4A] FIG. 1 is a simplified schematic diagram of an optical phased array laser system for noise-compensated dynamic beam shaping, constructed and operative in accordance with a still further preferred embodiment of the present invention; [Figure 4B-4C] 4B is a simplified graphical representation of phase modification and noise correction in a system of the type shown in FIG. 4A. [Figures 5A-5G] FIG. 4D is a simplified schematic diagram of the possible far-field motion of the output of an optical phased array laser system of any of the types shown in FIGS. 1A-4C. [Figure 6] FIG. 1 is a simplified schematic diagram of an optical phased array laser system including a plurality of detectors and a corresponding plurality of closely spaced optical paths, constructed and operative in accordance with yet another preferred embodiment of the present invention; [Figure 7] FIG. 1 is a simplified schematic diagram of an optical phased array laser system including a plurality of detectors and a corresponding plurality of closely spaced optical paths, constructed and operative in accordance with yet another preferred embodiment of the present invention; [Figure 8] FIG. 1 is a simplified schematic diagram of an optical phased array laser system including a plurality of detectors and a corresponding plurality of closely spaced optical paths, constructed and operative in accordance with a still further preferred embodiment of the present invention; [Figure 9] FIG. 1 is a simplified schematic diagram of an optical phased array laser system including a detector mask configured in accordance with an exemplary laser beam trajectory, constructed and operative in accordance with a preferred embodiment of the present invention; [Figure 10] FIG. 10 is a simplified schematic diagram of a detector mask of the type shown in FIG. 9, illustrating its various levels of transparency. [Figure 11] FIG. 1 is a simplified schematic diagram of an optical phased array laser system including a detector mask configured in accordance with an exemplary laser beam shape, constructed and operative in accordance with another preferred embodiment of the present invention; [Figure 12] 12 is a simplified schematic diagram of a detector mask of the type shown in FIG. 11, showing its various levels of transparency. [Figure 13] FIG. 1 is a simplified schematic diagram of an optical phased array laser system including a voltage-phase correlation function, constructed and operative in accordance with a preferred embodiment of the present invention; [Figure 14]14 is a simplified flowchart showing steps for performing voltage-phase correlation in a system of the type shown in FIG. 13. [Figure 15] FIG. 10 is a simplified schematic plan view of an optical phased array laser system including dynamic beam scaled phase modification, constructed and operative in accordance with an additional preferred embodiment of the present invention; [Figure 16] FIG. 10 is a simplified schematic plan view of an optical phased array laser system including dynamic beam scaled phase modification, constructed and operative in accordance with an additional preferred embodiment of the present invention; [Figures 17A-17B] 17A and 17B are simplified top and perspective views of an optical phased array laser system including dynamic beam scaled phase modification of the type shown in FIG. 15 or FIG. 16. [Figure 18] FIG. 1 is a simplified schematic plan view of an optical phased array laser system including dynamic beam scaled phase modification, constructed and operative in accordance with a further preferred embodiment of the present invention; [Figure 19] FIG. 1 is a simplified schematic plan view of an optical phased array laser system including dynamic beam scaled phase modification, constructed and operative in accordance with a further preferred embodiment of the present invention; [Figures 20A-20B] 19A-19C are simplified top and perspective views of an optical phased array laser system including dynamic beam scaled phase modification of the type shown in FIG. 18 or FIG. 19A-19C. [Figure 21] FIG. 1 is a simplified schematic plan view of an optical phased array laser system including dynamic beam scaled phase modification, constructed and operative in accordance with a still further preferred embodiment of the present invention; [Figures 22A-22B] 1A-1C are simplified schematic diagrams of respective first and second focus states of an optical phased array laser system constructed and operative in accordance with a preferred embodiment of the present invention; [Figure 23] FIG. 22C is a simplified representation of backscattering in an optical phased array laser system of the type shown in FIGS. 22A and 22B. [Figure 24] 1 is a simplified schematic diagram of a laser amplification system including a seed laser failure protection system constructed and operative in accordance with a preferred embodiment of the present invention; [Figure 25] FIG. 1 is a simplified schematic diagram of a laser amplification system including a seed laser failure protection system, constructed and operative in accordance with another preferred embodiment of the present invention; [Figure 26] 1 is a simplified schematic diagram of a laser amplifier system including a seed laser failure protection system constructed and operative in accordance with a further preferred embodiment of the present invention; [Figure 27] FIG. 1 is a simplified schematic diagram of a laser amplifier system including a seed laser failure protection system, constructed and operative in accordance with yet another preferred embodiment of the present invention; [Figure 28] 1 is a simplified schematic diagram of a laser amplifier system including a seed laser failure protection system, constructed and operative in accordance with yet another preferred embodiment of the present invention; [Figure 29] FIG. 1 is a simplified schematic diagram of a laser amplifier system including a seed laser failure protection system, constructed and operative in accordance with yet another preferred embodiment of the present invention; [Figure 30] 1 is a simplified schematic diagram of a laser amplifier system including a seed laser failure protection system, constructed and operative in accordance with a still further preferred embodiment of the present invention; [Figure 31] FIG. 1 is a simplified schematic diagram of a laser amplification system including a seed laser failure protection system, constructed and operative in accordance with a still further preferred embodiment of the present invention; [Figure 32] 1 is a simplified schematic diagram of a laser amplification system including a seed laser failure protection system, also constructed and operative in accordance with an additional preferred embodiment of the present invention; [Figure 33] FIG. 33 is a simplified schematic diagram of a sensor useful in a laser amplification system of any of the types shown in FIGS. 24-32. DETAILED DESCRIPTION OF THE INVENTION

[0171] Reference is now made to FIG. 1A, which is a simplified schematic diagram of an optical phased array laser system for noise-compensated dynamic beam shaping, constructed and operative in accordance with a preferred embodiment of the present invention, and to FIGS. 1B and 1C, which are simplified graphical representations of phase modification and noise compensation in a system of the type shown in FIG. 1A.

[0172] 1A , provided is an optical phased array (OPA) laser system 100, shown here by way of example as being used in a laser cutting system 102. The laser cutting system 102 may include the OPA laser system 100 mounted in a spaced-apart relationship to a multi-axis positioning table 104, on which an article, such as an article 106, can be cut using the laser system 100, as described in more detail below. While the laser cutting system 102 is shown herein in the context of the table 104, it is understood that the system 102 may be embodied as any type of laser cutting system, as would be understood by one of ordinary skill in the art.

[0173] As best seen in enlargement 110, OPA laser 100 preferably includes a seed laser 112 and a laser beam splitting and combining subsystem 114. Splitting and combining subsystem 114 preferably receives the output laser beam from seed laser 112 and splits the output laser beam into multiple sub-beams along a corresponding number of channels 116. Here, merely by way of example, the output from seed laser 112 is shown as being split into ten sub-beams along ten channels 116, although it will be understood that splitting and combining subsystem 114 may include a fewer or greater number of channels along which the output of seed laser 112 is split, and may typically include a much greater number of channels, such as 32 or more channels.

[0174] The relative phase of each sub-beam may preferably be individually modulated by a phase modulator 118 positioned along each of channels 116. Each phase-modulated sub-beam produced by splitting and subsequent phase modulation of the output of seed laser 112 preferably propagates toward a collimating lens 119. The individually collimated and phase-modulated sub-beams are then combined, for example, at a focusing lens 120, to form output beam 122.

[0175] Splitting and combining subsystem 114 may also preferably provide laser amplification of the sub-beams after splitting the output beam of seed laser 112 into sub-beams and before combining the sub-beams to form output beam 122. By way of example, splitting and combining subsystem 114 is shown here to include multiple optical amplifiers 124 positioned along corresponding ones of channels 116 for amplifying each sub-beam. However, it will be understood that such amplification is optional and may be omitted depending on the power output requirements of OPA laser 100.

[0176] The phase of output beam 122, and therefore the position and shape of its far-field intensity pattern, is controlled at least in part by the relative phases of the constituent sub-beams that are combined to form output beam 122. In many applications, such as laser cutting as shown in FIG. 1A, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. This may be achieved in laser system 100 by laser splitting and combining subsystem 114 dynamically changing the relative phases of the individual sub-beams, thereby changing the phase of combined laser output 122 to dynamically control the position and shape of its far-field intensity pattern.

[0177] The relative phases of the sub-beams are preferably predetermined according to the desired laser output pattern for cutting the article 106. Most preferably, the varying relative phases are applied by a phase control subsystem 130, which preferably forms part of a control electronics module 132 within the OPA laser 100 and preferably controls each phase modulator 118 to dynamically modulate the relative phases of the sub-beams along the channel 116.

[0178] Output beam 122 is noisy due to noise inherent in OPA system 100. The noise in output beam 122 is typically phase noise generated by thermal or mechanical effects and / or by the amplification process if optical amplifier 124 is present in OPA system 100. A particular feature of preferred embodiments of the present invention is that laser system 100 includes a noise cancellation subsystem 140 that operates to provide a noise-canceling phase-corrected output to cancel noise in output beam 122 in a manner described in more detail below.

[0179] Particularly preferably, noise cancellation subsystem 140 employs an algorithm to detect and correct phase noise in the combined laser output. A noise cancellation phase correction output is preferably provided by noise cancellation subsystem 140 to phase modulator 118 to correct for phase noise in output beam 122, thus avoiding distortions in the shape and position of the far-field intensity pattern of output beam 122 that would otherwise be caused by noise. Noise cancellation subsystem 140 may be included in control electronics module 132.

[0180] It is understood that output beam 122 may additionally or alternatively be affected by types of noise other than phase noise, including intensity noise. In the case of output beam 122 having intensity noise, noise cancellation subsystem 140 may operate to provide a noise-canceling phase-corrected output to cancel the intensity noise of output beam 122. In such cases, OPA laser system 100 may optionally additionally include intensity modulators 142 along channels 116 to modulate the intensity of each of the sub-beams along channels 116.

[0181] It is understood that output beam 122 may additionally or alternatively be affected by mechanical noise, which may affect the relative positions of the sub-beams. In the case of output beam 122 having position noise, noise cancellation subsystem 140 may operate to provide a noise-canceling phase-corrected output to cancel the position noise of output beam 122. In such cases, OPA laser system 100 may optionally additionally include a position modulator 144 along channel 116 to modulate the position of each of the sub-beams along channel 116.

[0182] To facilitate the application of phase modification and noise correction to output beam 122, a portion of the output of OPA laser 100 is preferably sampled and directed toward at least one detector, shown here as a single detector 150. Detector 150 may alternatively be embodied as multiple detectors, as described in more detail below with reference to FIGS. 6-8 and 15-21. The sampled portion of the output beam preferably serves as a reference beam, based on characteristics from which the necessary noise correction and / or phase modification may be calculated. In the embodiment shown in FIG. 1A, the multiple sub-beams along channel 116 are directed toward beam splitter 160. Beam splitter 160 preferably splits each sub-beam into a transmitted portion 162 and a reflected portion 164 according to a predetermined ratio. For example, beam splitter 160 may split each sub-beam with a 99.9% transmission:0.01% reflectance ratio.

[0183] The transmitted portions 162 of the sub-beams preferably propagate towards focusing lens 120, where the sub-beams combine to form output beam 122 having far-field intensity pattern 166 that is incident on the surface of article 106. The reflected portions 164 of the sub-beams preferably reflect towards additional focusing lens 168, where the sub-beams combine to form output reference beam 170 having far-field intensity pattern 172 that is incident on the surface of detector 150.

[0184] It is understood that the particular structures and configurations of the beam splitting and recombining elements shown herein, including beam splitter 160 and focusing lenses 120 and 168, are merely exemplary and are shown in a highly simplified form. It is understood that OPA laser system 100 may include a variety of such elements, as well as additional optical elements, including, by way of example only, additional or alternative lenses, optical fibers, and coherent free-space far-field couplers.

[0185] As described hereinabove, the shape and position of far-field intensity pattern 166 of output beam 122 and the corresponding shape and position of far-field intensity pattern 172 of reference beam 170 are constantly changing due to ongoing modifications of the relative phases of the sub-beams. As a result, far-field intensity pattern 172 is not fixed to detector 150, but rather is constantly moving relative to detector 150 depending on the combined relative phases of the constituent sub-beams. However, in order for detector 150 to provide the necessary noise-canceling, phase-corrected output, far-field intensity pattern 172 must be incident on detector 150 so that the detector can measure the intensity of far-field intensity pattern 172 and therefore apply noise correction accordingly, resulting in a fixed output beam.

[0186] The conflict between the dynamic nature of far-field intensity pattern 172 due to its phase modification and the fixed nature required of far-field intensity pattern 172 in order to derive and apply noise correction is advantageously resolved in the present invention by providing noise cancellation and phase modification at different times and rates from each other.

[0187] The noise cancellation phase corrected output is provided based on taking into account the noise measured at detector 150 at the noise sampling rate. Output beam 122 is controlled in such a way that far-field intensity pattern 172 is incident on detector 150 at a rate equal to or greater than the required noise sampling rate during dynamic changes to the shape and position of output and reference far-field intensity patterns 166, 172. The noise in reference beam 170 is taken into account during these intermittent times when far-field intensity pattern 172 is returned to detector 150.

[0188] During the time intervals between intermittent times when far-field intensity pattern 172 is incident on detector 150, the phase of combined output beams 122 and 170 is altered to dynamically change the shape and position of the far-field intensity pattern as needed to perform laser cutting of article 106. The combined laser output is altered at a phase change rate that exceeds the noise sampling rate to rapidly change the phase, and therefore the shape and position of the far-field intensity pattern. By way of example, the noise sampling rate may be on the order of 10-1000 Hz, while the phase change rate may be greater than 10,000 Hz.

[0189] The different rates and time scales at which noise cancellation and phase modification are preferably implemented in embodiments of the present invention can best be understood with reference to graph 180 seen in FIG. 1A and an expanded version thereof shown in FIG. 1B.

[0190] 1B , graph 180 includes an upper portion 182 that displays the change in intensity over time of far-field intensity pattern 172 measured at detector 150, and a lower portion 184 that displays the change over the same time period in the relative phase of multiple sub-beams that contribute to output beam 122 and reference beam 170. For simplicity, the relative phases of 10 sub-beams are displayed in graph 180, although it will be understood that OPA system 100, and therefore the description provided herein, is applicable to fewer, or more typically, a much larger number of sub-beams.

[0191] As seen in upper portion 182, intensity peaks 186 represent the measured intensity of reference beam 170 as far-field intensity pattern 172 passes over detector 150. As seen in lower portion 184, intensity peaks 186 occur at discrete times T where the relative phase of each sub-beam is zero. i , which means that there is no phase shift between the sub-beams, the position of the combined output beam therefore does not change, and far-field intensity pattern 172 is therefore directly incident on detector 150. It will be appreciated that detector 150 may alternatively be positioned such that the relative phase of the sub-beams thereat is non-zero. Furthermore, as will be described in more detail below with reference to Figures 6-8 and 15-21, multiple detectors may be used to allow far-field intensity pattern 172 to be measured at multiple positions along the detector.

[0192] Between intensity peaks 186, the measured intensity is near zero because far-field intensity pattern 172 is moved to either side of detector 150 and therefore is not directly incident on detector 150. As can be seen from an examination of upper portion 182, the magnitude of intensity peaks 186 is not constant due to the presence of noise in the laser output beam, which degrades far-field intensity pattern 172.

[0193] As can be seen in the lower portion 184, the relative phases of the sub-beams are discontinuous for a time T i The time interval T between betweenIn the phase modification functions shown herein, the relative phases of the sub-beams are shown to be modified in a periodic, regularly repeating pattern with equal phase shifts applied in the positive and negative directions. It will be understood that such simplified patterns are merely exemplary, and that the phase modifications need not necessarily be regularly repeating, nor necessarily symmetrical in the positive and negative directions. Furthermore, the time interval T between is the intermittent time T i It is understood that, while it is preferred, they do not necessarily overlap. Additionally, it is understood that at least one of the phase change rate and the noise sampling rate may be constant or may vary over time.

[0194] The noise cancellation subsystem 140 preferably operates at intermittent times T i It works by considering noise at,intermittent time T i The noise cancellation subsystem 140 preferably uses an algorithm to detect noise and correct the detected noise accordingly.

[0195] According to one exemplary embodiment of the present invention, noise cancellation subsystem 140 uses an algorithm in which, during each cycle of movement of far-field intensity pattern 172 relative to detector 150, the relative phase of one channel is changed in such a way that it is modified by a given phase change Δφ. Following a number of such cycles in which a different phase change Δφ is applied to a selected sub-beam over each cycle, the algorithm checks for the maximum output intensity over all of the cycles and finds the optimal phase change Δφ that produced this maximum intensity. The phase change of the selected sub-beam is then fixed to the optimal phase change Δφ for the subsequent cycle, and the algorithm proceeds to optimize another sub-beam.

[0196] Graph 180 illustrates noise cancellation by this exemplary algorithm in channels A, B, and C for three sub-beams or a total of 10 sub-beams. For simplicity, sub-beams A, B, and C are shown alone in FIG. 1C. It will be appreciated that in FIG. 1C, the line style of the lines representing the phase changes and noise corrections for sub-beams A, B, and C, respectively, has been modified compared to FIGS. 1A and 1B to aid in distinguishing between the various sub-beams for purposes of the remainder of this specification.

[0197] As seen first for channel A, and most clearly understood from consideration of zoom in 190, the dashed line represents the pattern of relative phase modifications of sub-beam A that would be applied by phase control subsystem 130 in the absence of any noise correction. uncorrected The dotted and dashed lines represent the actual relative phase of sub-beam A as modified by the noise correction algorithm to find the optimal phase noise correction. corrected It is sometimes called. A corrected The corrected relative phase of A is uncorrected Δφ for the uncorrected relative phase of A The intensity 186 measured at detector 150 changes over the first five cycles of optimization of sub-beam A due to the intentional change in the relative phase shift.

[0198] After the first five cycles of sub-beam A, the algorithm identifies the maximum intensity and determines the phase change Δφ that produces the maximum intensity. A In this case, the maximum intensity occurs at the second phase shift Δφ A IA generated by max The phase change applied to the relative phase change of sub-beam A is therefore the second phase shift Δφ for the subsequent cycle. A and the algorithm proceeds to optimize sub-beam B.

[0199] It will be appreciated that during successive cycles of optimization of sub-beam A, the relative phases of the remaining portions of the sub-beams are each normally altered at a phase alteration rate that far exceeds the noise sampling rate at which noise in sub-beam A is taken into account.

[0200] As further seen in the case of sub-beam B, and most clearly understood from consideration of zoom-in view 192, the thicker line during the optimization of channel B represents the pattern of relative phase modifications for sub-beam B that would be applied by phase control subsystem 130 in the absence of any noise correction. uncorrected The thin line in the optimization for channel B represents the actual relative phase of sub-beam B as modified by the noise correction algorithm to find the optimal phase noise correction. corrected It is sometimes called B corrected The corrected relative phase of B is calculated over five cycles of the optimization sub-beam B. uncorrected Δφ for the uncorrected relative phase of B The intensity 186 measured at detector 150 changes over these five cycles of optimized sub-beam B due to the intentional change in relative phase shift.

[0201] After these five cycles of sub-beam B, the algorithm identifies the maximum intensity and determines the phase change Δφ that produces the maximum intensity. B In this case, the maximum intensity is found at the fourth phase shift Δφ B Generated by IAB max The phase shift applied to the relative phase shift of sub-beam B is then a fourth phase shift Δφ for the subsequent cycle. B is fixed and the algorithm proceeds to optimize sub-beam C.

[0202] It is understood that during the five cycles of optimization of sub-beam B, the relative phases of the remaining sub-beams are each normally altered at a phase change rate that far exceeds the noise sampling rate at which the noise of sub-beam B is taken into account.

[0203] Preferably, a similar optimization process is performed for sub-beam C, where the phase change Δφ is adjusted over several cycles to optimize the output beam intensity and correct for its intensity degradation due to phase noise in sub-beam C. C applies.

[0204] At least one detector 150 can operate continuously to continuously optimize the relative phases of the sub-beams and correct for phase noise therein. However, due to the finite response time of the detector 150, the detector 150 only considers the noise in the reference beam 170 at intermittent times, at a relatively slow noise sampling rate. The noise sampling rate is preferably, but not necessarily, predetermined. Alternatively, the noise sampling rate may be random.

[0205] Those skilled in the art will appreciate that the specific parameters of the noise correction algorithm shown in graph 180 are merely exemplary and may be readily modified. For example, the phase shift Δφ may be optimized over a greater or lesser number of cycles than shown herein, each sub-beam may be fully optimized each time it passes through detector 150, or some or all of the sub-beams may be optimized during each cycle that the far-field intensity pattern passes through detector 150. Additionally, non-continuous noise correction optimization algorithms may alternatively be implemented, including, but not limited to, stochastic parallel gradient descent optimization algorithms.

[0206] The use of a dynamically shaped, noise-compensated optical phased array output beam for laser cutting is highly advantageous, enabling rapid beam steering, fast power modulation, fast beam focusing, and beam shape adjustment. Compared to conventional laser cutting methods, the use of a dynamically shaped, noise-compensated optical phased array output improves both the speed and quality with which materials can be cut. It is understood that providing noise compensation according to preferred embodiments of the present invention degrades the shape and position of the optical phased array output beam, thereby degrading the quality, speed, and accuracy of the laser cutting process.

[0207] To maintain output beam intensity as the beam's far-field intensity pattern moves, which can be advantageous in certain laser cutting applications, the movement of the output beam can be controlled so that the beam spends more time at lower intensity positions to compensate for reduced power transfer there. Additionally or alternatively, an intensity profile mask, such as a neutral density (ND) filter, may be applied to the output beam to modify its intensity.

[0208] Reference is now made to FIG. 2A, which is a simplified schematic illustration of an optical phased array laser system for noise-compensated dynamic beam shaping, constructed and operative in accordance with another preferred embodiment of the present invention, and FIGS. 2B and 2C, which are simplified graphical representations of phase modification and noise compensation within a system of the type shown in FIG. 2A.

[0209] 2A , provided herein, by way of example, is an optical phased array (OPA) laser system 200, shown for use within additive manufacturing system 202. Additive manufacturing system 202 may include OPA laser system 200 mounted in a spaced apart relationship relative to a scanning mirror 203 and a multi-axis positioning table 204, upon which an article, such as article 206, may be additively manufactured using laser system 200. While additive manufacturing system 202 is shown herein in the context of scanning mirror 203, it is understood that system 202 may be embodied as any type of additive manufacturing system, as would be understood by one of ordinary skill in the art.

[0210] As best seen in close-up view 210, OPA laser 200 preferably comprises a seed laser 212 and a laser beam splitting and combining subsystem 214. Splitting and combining subsystem 214 preferably receives the output laser beam from seed laser 212 and splits the output laser beam into multiple sub-beams along a corresponding number of channels 216. Here, merely by way of example, the output from seed laser 212 is shown as being split into ten sub-beams along ten channels 216, although it will be understood that splitting and combining subsystem 214 may include a fewer or greater number of channels along which the output of seed laser 212 is split, and may typically include a much greater number of channels, such as 32 or more channels.

[0211] The relative phase of each sub-beam may preferably be individually modulated by a phase modulator 218 positioned along each of channels 216. Each phase-modulated sub-beam produced by splitting and subsequent phase modulation of the output of seed laser 212 preferably propagates toward a collimating lens 219. The individually collimated and phase-modulated sub-beams are then combined, for example, at a focusing lens 220, to form output beam 222.

[0212] Splitting and combining subsystem 214 can also preferably provide laser amplification of the sub-beams after splitting the output beam of seed laser 212 into sub-beams and before combining the sub-beams to form output beam 222. Here, by way of example, splitting and combining subsystem 214 is shown to include multiple optical amplifiers 224 positioned along corresponding ones of channels 216 for amplifying each sub-beam. However, it will be understood that such amplification is optional and may be omitted depending on the power output requirements of OPA laser 200.

[0213] The phase of output beam 222, and therefore the position and shape of its far-field intensity pattern, is controlled at least in part by the relative phases of the constituent sub-beams that are combined to form output beam 222. In many applications, such as laser additive manufacturing as shown in FIG. 2A, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. This can be achieved in laser system 200 by laser splitting and combining subsystem 214 dynamically changing the relative phases of the individual sub-beams, thereby changing the phase of combined laser output 222 to dynamically control the position and shape of its far-field intensity pattern.

[0214] The relative phases of the sub-beams are preferably predetermined according to a desired laser output pattern for 3D printing of article 206. Most preferably, the varying relative phases are applied by phase control subsystem 230, which preferably forms part of a control electronics module 232 within OPA laser 200 and preferably controls each phase modulator 218 to dynamically modulate the relative phases of the sub-beams along channel 216.

[0215] Output beam 222 is noisy due to noise inherent in OPA system 200. The noise in output beam 222 is typically phase noise generated by thermal or mechanical effects and / or by the amplification process if optical amplifier 224 is present in OPA system 200. A particular feature of preferred embodiments of the present invention is that laser system 200 includes a noise cancellation subsystem 240 that operates to provide a noise-canceling phase-corrected output to cancel noise in output beam 222 in a manner described in more detail below.

[0216] Particularly preferably, noise cancellation subsystem 240 employs an algorithm to detect and correct phase noise in the combined laser output. A noise cancellation phase correction output is preferably provided by noise cancellation subsystem 240 to phase modulator 218 to correct for phase noise in output beam 222, thus avoiding distortions in the shape and position of the far-field intensity pattern of output beam 222 that would otherwise be caused by noise. Noise cancellation subsystem 240 may be included in control electronics module 232.

[0217] It is understood that output beam 222 may additionally or alternatively be affected by types of noise other than phase noise, including intensity noise. In the case of output beam 222 having intensity noise, noise cancellation subsystem 240 may operate to provide a noise-canceling phase-corrected output to cancel the intensity noise of output beam 222. In such cases, OPA laser system 200 may optionally additionally include intensity modulators 242 along channels 216 to modulate the intensity of each of the sub-beams along channels 216.

[0218] It is understood that output beam 222 may additionally or alternatively be affected by mechanical noise, which may affect the relative positions of the sub-beams. In the case of output beam 222 having position noise, noise cancellation subsystem 240 may operate to provide a noise-canceling phase-corrected output to cancel the position noise of output beam 222. In such cases, OPA laser system 200 may optionally additionally include a position modulator 244 along channel 216 to modulate the position of each of the sub-beams along channel 216.

[0219] To facilitate the application of phase modification and noise correction to output beam 222, a portion of the output of OPA laser 200 is preferably sampled and directed toward at least one detector, shown here as a single detector 250. Detector 250 may alternatively be embodied as multiple detectors, as described in more detail below with reference to FIGS. 6-8 and 15-21. The sampled portion of the output beam preferably serves as a reference beam, based on characteristics from which the required noise correction and / or phase modification may be calculated. In the embodiment shown in FIG. 2A, the multiple sub-beams along channel 216 are directed toward beam splitter 260. Beam splitter 260 preferably splits each sub-beam into a transmitted portion 262 and a reflected portion 264 according to a predetermined ratio. For example, beam splitter 260 may split each sub-beam with a 99.9% transmission:0.01% reflectance ratio.

[0220] The transmitted portions 262 of the sub-beams preferably propagate towards focusing lens 220 where the sub-beams combine to form output beam 222 having far-field intensity pattern 266 that is incident on scanning mirror 203. The reflected portions 264 of the sub-beams preferably reflect towards additional focusing lens 268 where the sub-beams combine to form output reference beam 270 having far-field intensity pattern 272 that is incident on the surface of detector 250.

[0221] It is understood that the particular structures and configurations of the beam splitting and recombining elements shown herein, including beam splitter 260 and focusing lenses 220 and 268, are merely exemplary and are shown in a highly simplified form. It is understood that OPA laser system 200 may include a variety of such elements, as well as additional optical elements, including, by way of example only, additional or alternative lenses, optical fibers, and coherent free-space far-field couplers.

[0222] As described hereinabove, the shape and position of far-field intensity pattern 266 of output beam 222 and the corresponding shape and position of far-field intensity pattern 272 of reference beam 270 are constantly changing due to ongoing modifications of the relative phases of the sub-beams. As a result, far-field intensity pattern 272 is not fixed to detector 250, but rather is constantly moving relative to detector 250 depending on the combined relative phases of the constituent sub-beams. However, in order for detector 250 to provide the necessary noise-canceling, phase-corrected output, far-field intensity pattern 272 must be incident on detector 250 so that the detector can measure the intensity of far-field intensity pattern 272 and therefore apply noise correction accordingly, resulting in a fixed output beam.

[0223] The conflict between the dynamic nature of far-field intensity pattern 272 due to its phase modification and the required fixed nature of far-field intensity pattern 272 in order to derive and apply noise correction is advantageously resolved in the present invention by providing noise cancellation and phase modification at different times and rates.

[0224] The noise cancellation phase corrected output is provided based on accounting for the noise measured at detector 250 at the noise sampling rate. Output beam 222 is controlled in such a way that far-field intensity pattern 272 is incident on detector 250 at a rate equal to or faster than the required noise sampling rate during dynamic changes to the shape and position of output and reference far-field intensity patterns 266, 272. The noise in reference beam 270 is accounted for during these intermittent times when far-field intensity pattern 272 is returned to detector 250.

[0225] During the time intervals between intermittent times when far-field intensity pattern 272 is incident on detector 250, the phase of combined output beams 222, 270 is altered to dynamically change the shape and position of that far-field intensity pattern as needed to perform additive manufacturing of article 206. The combined laser output is altered at a phase change rate that exceeds the noise sampling rate to rapidly change the phase, and therefore the shape and position of the far-field intensity pattern. By way of example, the noise sampling rate may be on the order of 10-1000 Hz, while the phase change rate may be greater than 10,000 Hz.

[0226] The different rates and time scales at which noise cancellation and phase modification are preferably implemented in embodiments of the present invention can best be understood with reference to graph 280 seen in FIG. 2A and an expanded version thereof shown in FIG. 2B.

[0227] 2B , graph 280 includes an upper portion 282 that displays the change in intensity over time of far-field intensity pattern 272 measured at detector 250, and a lower portion 284 that displays the change over the same time period in the relative phase of multiple sub-beams that contribute to output beam 222 and reference beam 270. For simplicity, the relative phases of 10 sub-beams are displayed in graph 280, although it will be understood that OPA system 200, and therefore the description provided herein, is applicable to fewer, or more typically, a much larger number of sub-beams.

[0228] As seen in upper portion 282, intensity peaks 286 represent the measured intensity of reference beam 270 as far-field intensity pattern 272 passes over detector 250. As seen in lower portion 284, intensity peaks 286 occur at discrete times T where the relative phase of each sub-beam is zero. i , which means that there is no phase shift between the sub-beams, the position of the combined output beam therefore does not change, and far-field intensity pattern 272 is therefore directly incident on detector 250. It will be appreciated that detector 250 may alternatively be positioned such that the relative phase of the sub-beams thereat is non-zero. Furthermore, as will be described in more detail below with reference to Figures 6-8 and 15-21, multiple detectors may be used to enable measurement of far-field intensity pattern 272 at multiple positions along the detector.

[0229] Between intensity peaks 286, the measured intensity is near zero because far-field intensity pattern 272 is moved to either side of detector 250 and therefore is not directly incident on detector 250. As can be seen from an examination of upper portion 282, the magnitude of intensity peaks 286 is not constant due to the presence of noise in the laser output beam, which degrades far-field intensity pattern 272.

[0230] As can be seen in the lower portion 284, the relative phases of the sub-beams are discontinuous for a time T i The time interval T between betweenIn the phase modification functions shown herein, the relative phases of the sub-beams are shown to be modified in a periodic, regularly repeating pattern with equal phase shifts applied in the positive and negative directions. It will be understood that such a simplified pattern is merely exemplary, and that the phase modifications need not necessarily be regularly repeating, nor necessarily symmetrical in the positive and negative directions. Furthermore, the time interval T between is the intermittent time T i It is understood that, although preferably, they do not necessarily overlap. Additionally, it is understood that at least one of the phase change rate and the noise sampling rate may be constant or may vary over time.

[0231] The noise cancellation subsystem 240 preferably operates at intermittent times T i It works by considering noise at,intermittent time T i The noise cancellation subsystem 240 preferably uses an algorithm to detect noise and correct the detected noise accordingly.

[0232] According to one exemplary embodiment of the present invention, noise cancellation subsystem 240 uses an algorithm in which, during each cycle of movement of far-field intensity pattern 272 relative to detector 250, the relative phase of one channel is changed in such a way that the relative phase is modified by a given phase change Δφ. Following a number of such cycles in which a different phase change Δφ is applied to a selected sub-beam over each cycle, the algorithm checks for the maximum output intensity over all of the cycles and finds the optimal phase change Δφ that produced this maximum intensity. The phase change of the selected sub-beam is then fixed to the optimal phase change Δφ for the subsequent cycle, and the algorithm proceeds to optimize another sub-beam.

[0233] Graph 280 illustrates noise cancellation by this exemplary algorithm in channels A, B, and C for three sub-beams or a total of 10 sub-beams. For simplicity, sub-beams A, B, and C are shown alone in FIG. 2C. It will be appreciated that in FIG. 2C, the line style of the lines representing the phase changes and noise corrections for sub-beams A, B, and C, respectively, has been modified compared to FIGS. 2A and 2B to aid in distinguishing between the various sub-beams for purposes of discussion later herein.

[0234] As seen first for channel A, and most clearly understood from consideration of zoom 290, the dashed line represents the pattern of relative phase modifications of sub-beam A that would be applied by phase control subsystem 230 in the absence of any noise correction. uncorrected The dotted and dashed lines represent the actual relative phase of sub-beam A as modified by the noise correction algorithm to find the optimal phase noise correction. corrected It is sometimes called. A corrected The corrected relative phase of A is uncorrected Δφ for the uncorrected relative phase of A The intensity 286 measured at detector 250 changes over the first five cycles of optimization of sub-beam A due to the intentional change in the relative phase shift.

[0235] After the first five cycles of sub-beam A, the algorithm identifies the maximum intensity and determines the phase change Δφ that produces the maximum intensity. A In this case, the maximum intensity occurs at the second phase shift Δφ A IA generated by max The phase change applied to the relative phase change of sub-beam A is therefore the second phase shift Δφ for the subsequent cycle. A and the algorithm proceeds to optimize sub-beam B.

[0236] It will be appreciated that during successive cycles of optimization of sub-beam A, the relative phases of the remaining portions of the sub-beams are each normally altered at a phase change rate that far exceeds the noise sampling rate at which noise in sub-beam A is taken into account.

[0237] As further seen in the case of sub-beam B, and most clearly understood from consideration of zoom-in view 292, the thicker line during the optimization of channel B represents the pattern of changes in the relative phase of sub-beam B that would be applied by phase control subsystem 230 in the absence of any noise correction. uncorrected The thin line in the optimization for channel B represents the actual relative phase of sub-beam B as modified by the noise correction algorithm to find the optimal phase noise correction. corrected It is sometimes called B corrected The corrected relative phase of B is calculated over five cycles of the optimization sub-beam B. uncorrected Δφ for the uncorrected relative phase of B The intensity 286 measured at detector 250 changes over these five cycles of optimization sub-beam B due to the intentional change in relative phase shift.

[0238] After these five cycles of sub-beam B, the algorithm identifies the maximum intensity and determines the phase change Δφ that produces the maximum intensity. B In this case, the maximum intensity is found at the fourth phase shift Δφ B Generated by IAB max The phase shift applied to the relative phase shift of sub-beam B is then a fourth phase shift Δφ for the subsequent cycle. B is fixed and the algorithm proceeds to optimize sub-beam C.

[0239] It is understood that during the five cycles of optimization of sub-beam B, the relative phases of the remaining sub-beams are each changed normally at a phase change rate that far exceeds the noise sampling rate at which the noise of sub-beam B is taken into account.

[0240] Preferably, a similar optimization process is performed for sub-beam C, where the phase change Δφ is adjusted over several cycles to optimize the output beam intensity and correct for its intensity degradation due to phase noise in sub-beam C. C applies.

[0241] Detector 250 can operate continuously to continually optimize the relative phases of the sub-beams and correct for phase noise therein. However, due to the finite response time of detector 250, detector 250 only considers noise in reference beam 270 at intermittent times, at a relatively slow noise sampling rate. The noise sampling rate is preferably, but not necessarily, predetermined. Alternatively, the noise sampling rate may be random.

[0242] Those skilled in the art will appreciate that the specific parameters of the noise correction algorithm shown in graph 280 are merely exemplary and may be readily modified. For example, the phase shift Δφ may be optimized over a greater or lesser number of cycles than shown herein, each sub-beam may be fully optimized each time it passes detector 250, or some or all of the sub-beams may be optimized during each cycle that the far-field intensity pattern passes detector 250. Additionally, non-continuous noise correction optimization algorithms may alternatively be implemented, including, but not limited to, stochastic parallel gradient descent optimization algorithms.

[0243] The use of a dynamically shaped, noise-compensated optical phased array output beam in laser additive manufacturing is highly advantageous, enabling rapid beam steering, fast power modulation, fast beam focusing, and beam shape adjustment. Compared to conventional laser 3D printing methods, the use of a dynamically shaped, noise-compensated optical phased array output improves both the speed and quality with which articles can be manufactured. It is understood that without the provision of noise compensation in accordance with preferred embodiments of the present invention, the shape and position of the optical phased array output beam would be degraded, thereby degrading the quality, speed, and accuracy of the laser additive manufacturing process.

[0244] To maintain output beam intensity as the far-field intensity pattern of the beam moves, which can be advantageous in certain additive manufacturing applications, the movement of the output beam can be controlled so that the beam spends more time at lower intensity positions to compensate for reduced power delivery there. Additionally or alternatively, an intensity profile mask, such as a neutral density filter, may be applied to the output beam to modify its intensity.

[0245] Reference is now made to FIG. 3A, which is a simplified schematic illustration of an optical phased array laser system for noise-compensated dynamic beam shaping, constructed and operative in accordance with a further preferred embodiment of the present invention, and to FIGS. 3B and 3C, which are simplified graphical representations of phase modification and noise compensation within a system of the type shown in FIG. 3A.

[0246] As seen in FIG. 3A , an optical phased array (OPA) laser system 300 is provided, shown here by way of example for use within a free-space optical communication system 302. The free-space optical communication system 302 may include an OPA laser system 300 mounted on an outdoor location, such as a building, in a spaced relationship relative to a receiver 303 for receiving optical signals emitted from the OPA laser 300. While the free-space optical communication system 302 is shown herein in the context of communication between two fixed points, it will be understood by one skilled in the art that the free-space optical communication system 302 may be adapted for use in communication between two locations that move relative to one another. While the free-space optical communication system 302 is shown herein in the context of terrestrial communications, it will be further understood by one skilled in the art that the free-space optical communication system 302 may be adapted for use in extraterrestrial communications.

[0247] 3A as including only a single OPA laser 300 and receiver 303 for simplicity's sake, it is understood that free space optical communication system 302 may include a greater number of single OPA lasers 300 and receivers 303 depending on the communication requirements of system 302. It is further understood that receiver 303 may be a type of OPA laser similar to OPA laser 300 and having receiving functionality. Furthermore, OPA laser 300 may include receiving functionality to enable dual operation of OPA lasers 300 and 303 for transmission and reception of optical signals therebetween.

[0248] As best seen in close-up view 310, OPA laser 300 preferably comprises a seed laser 312 and a laser beam splitting and combining subsystem 314. Splitting and combining subsystem 314 preferably receives the output laser beam from seed laser 312 and splits the output laser beam into multiple sub-beams along a corresponding number of channels 316. Here, merely by way of example, the output from seed laser 312 is shown as being split into ten sub-beams along ten channels 316, although it will be understood that splitting and combining subsystem 314 may include a fewer or greater number of channels along which the output of seed laser 312 is split, and may typically include a much greater number of channels, such as 32 or more channels.

[0249] The relative phase of each sub-beam may preferably be individually modulated by a phase modulator 318 positioned along each of channels 316. Each phase-modulated sub-beam produced by splitting and subsequent phase modulation of the output of seed laser 312 preferably propagates toward a collimating lens 319. The individually collimated and phase-modulated sub-beams are then combined, for example, at focusing lens 320, to form output beam 322.

[0250] Splitting and combining subsystem 314 can also preferably provide laser amplification of the sub-beams after splitting the output beam of seed laser 312 into sub-beams and before combining the sub-beams to form output beam 322. Here, by way of example, splitting and combining subsystem 314 is shown to include multiple optical amplifiers 324 positioned along corresponding ones of channels 316 for amplifying each sub-beam. However, it will be understood that such amplification is selectable and may be omitted depending on the power output requirements of OPA laser 300.

[0251] The phase of output beam 322, and therefore the position and shape of its far-field intensity pattern, is controlled at least in part by the relative phases of the constituent sub-beams that are combined to form output beam 322. In many applications, such as free-space optical communications as shown in FIG. 3A, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. This can be achieved in laser system 300 by laser splitting and combining subsystem 314 dynamically changing the relative phases of the individual sub-beams, thereby changing the phase of combined laser output 322 to dynamically control the position and shape of its far-field intensity pattern.

[0252] The relative phases of the sub-beams are preferably predetermined according to a desired laser output pattern for transmission to receiver 303. Most preferably, the varying relative phases are applied by phase control subsystem 330, which preferably forms part of control electronics module 332 within OPA laser 300 and preferably controls each phase modulator 318 to dynamically modulate the relative phases of the sub-beams along channel 316.

[0253] Output beam 322 is noisy due to noise inherent in OPA system 300. The noise in output beam 322 is typically phase noise generated by thermal or mechanical effects and / or by the amplification process if optical amplifier 324 is present in OPA system 300. A particular feature of preferred embodiments of the present invention is that laser system 300 includes a noise cancellation subsystem 340 that operates to provide a noise-canceling phase-corrected output to cancel noise in output beam 322 in a manner described in more detail below.

[0254] Particularly preferably, noise cancellation subsystem 340 employs an algorithm to detect and correct phase noise in the combined laser output. A noise cancellation phase correction output is preferably provided by noise cancellation subsystem 340 to phase modulator 318 to correct for phase noise in output beam 322, thus avoiding distortions in the shape and position of the far-field intensity pattern of output beam 322 that would otherwise be caused by noise. Noise cancellation subsystem 340 may be included in control electronics module 332.

[0255] It is understood that output beam 322 may additionally or alternatively be affected by types of noise other than phase noise, including intensity noise. In the case of output beam 322 having intensity noise, noise cancellation subsystem 340 may operate to provide a noise-canceling phase-corrected output to cancel the intensity noise of output beam 322. In such cases, OPA laser system 300 may optionally additionally include intensity modulators 342 along channels 316 to modulate the intensity of each of the sub-beams along channels 316.

[0256] It is understood that output beam 322 may additionally or alternatively be affected by mechanical noise, which may affect the relative positions of the sub-beams. In the case of output beam 322 having position noise, noise cancellation subsystem 340 may operate to provide a noise-canceling phase-corrected output to cancel the position noise of output beam 322. In such cases, OPA laser system 300 may optionally additionally include a position modulator 344 along channel 316 to modulate the position of each of the sub-beams along channel 316.

[0257] To facilitate the application of phase modification and noise correction to output beam 322, a portion of the output of OPA laser 300 is preferably sampled and directed toward at least one detector, shown here as single detector 350. Detector 350 may alternatively be embodied as multiple detectors, as described in more detail below with reference to FIGS. 6-8 and 15-21. The sampled portion of the output beam preferably serves as a reference beam, based on characteristics from which the required noise correction and / or phase modification may be calculated. In the embodiment shown in FIG. 3A, the multiple sub-beams along channel 316 are directed toward beam splitter 360. Beam splitter 360 preferably splits each sub-beam into a transmitted portion 362 and a reflected portion 364 according to a predetermined ratio. For example, beam splitter 360 may split each sub-beam with a 99.9% transmission:0.01% reflectance ratio.

[0258] The transmitted portions 362 of the sub-beams preferably propagate towards focusing lens 320, where the sub-beams combine to form output beam 322 having far-field intensity pattern 366. The reflected portions 364 of the sub-beams preferably reflect towards additional focusing lens 368, where the sub-beams combine to form output reference beam 370 having far-field intensity pattern 372 that is incident on the surface of detector 350.

[0259] It is understood that the particular structures and configurations of the beam splitting and recombining elements shown herein, including beam splitter 360 and focusing lenses 320 and 368, are merely exemplary and are shown in a highly simplified form. It is understood that OPA laser system 300 may include a variety of such elements, as well as additional optical elements, including, by way of example only, additional or alternative lenses, optical fibers, and coherent free-space far-field couplers.

[0260] As described hereinabove, the shape and position of far-field intensity pattern 366 of output beam 322 and the corresponding shape and position of far-field intensity pattern 372 of reference beam 370 are constantly changing due to ongoing modifications of the relative phases of the sub-beams. As a result, far-field intensity pattern 372 is not fixed to detector 350, but rather is constantly moving relative to detector 350 depending on the combined relative phases of the constituent sub-beams. However, in order for detector 350 to provide the necessary noise-canceling, phase-corrected output, far-field intensity pattern 372 must be incident on detector 350 so that the detector can measure the intensity of far-field intensity pattern 372 and therefore apply noise correction accordingly, resulting in a fixed output beam.

[0261] The conflict between the dynamic nature of far-field intensity pattern 372 due to its phase modification and the fixed nature required of far-field intensity pattern 372 in order to derive and apply noise correction is advantageously resolved in the present invention by providing noise cancellation and phase modification at different times and rates from each other.

[0262] The noise cancellation phase corrected output is provided based on accounting for the noise measured at detector 350 at the noise sampling rate. Output beam 322 is controlled in such a way that far-field intensity pattern 372 is incident on detector 350 at a rate equal to or faster than the required noise sampling rate during dynamic changes to the shape and position of output and reference far-field intensity patterns 366, 372. The noise in reference beam 370 is accounted for during these intermittent times when far-field intensity pattern 372 is returned to detector 350.

[0263] During the time intervals between intermittent times when far-field intensity pattern 372 is incident on detector 350, the phase of combined output beams 322, 370 is altered to dynamically change the shape and position of the far-field intensity pattern as needed to perform additive manufacturing of article 206. The combined laser output is altered at a phase change rate that exceeds the noise sampling rate to rapidly change the phase, and therefore the shape and position of the far-field intensity pattern. By way of example, the noise sampling rate may be on the order of 10-1000 Hz, while the phase change rate may be greater than 10,000 Hz.

[0264] The different rates and time scales at which noise cancellation and phase modification are preferably implemented in embodiments of the present invention can best be understood with reference to graph 380 seen in FIG. 3A and an expanded version thereof shown in FIG. 3B.

[0265] 3B , graph 380 includes an upper portion 382 that displays the change in intensity over time of far-field intensity pattern 372 measured at detector 350, and a lower portion 384 that displays the change over the same time period in the relative phase of multiple sub-beams that contribute to output beam 322 and reference beam 370. For simplicity, the relative phases of 10 sub-beams are displayed in graph 380, although it will be understood that OPA system 300, and therefore the description provided herein, is applicable to a fewer, or more typically, a much greater number of sub-beams.

[0266] As seen in upper portion 382, ​​intensity peaks 386 represent the measured intensity of reference beam 370 as far-field intensity pattern 372 passes over detector 350. As seen in lower portion 384, intensity peaks 386 occur at discrete times T where the relative phase of each sub-beam is zero. i, which means that there is no phase shift between the sub-beams, and therefore the position of the combined output beam does not change, and therefore far-field intensity pattern 372 is incident directly on detector 350. It will be appreciated that detector 350 may alternatively be positioned such that the relative phase of the sub-beams thereat is non-zero. Furthermore, as will be described in more detail below with reference to Figures 6-8 and 15-21, multiple detectors may be used, allowing far-field intensity pattern 372 to be measured at multiple positions along the detector.

[0267] Between intensity peaks 386, the measured intensity is near zero because far-field intensity pattern 372 is moved to either side of detector 350 and therefore is not directly incident on detector 350. As can be seen from an examination of upper portion 382, ​​the magnitude of intensity peaks 386 is not constant due to the presence of noise in the laser output beam, which degrades far-field intensity pattern 372.

[0268] As can be seen in the lower portion 384, the relative phases of the sub-beams are discontinuous for a time T i The time interval T between between In the phase modification functions shown herein, the relative phases of the sub-beams are shown to be modified in a periodic, regularly repeating pattern with equal phase shifts applied in the positive and negative directions. It will be understood that such a simplified pattern is merely illustrative, and that the phase modifications need not necessarily be regularly repeating, nor necessarily symmetrical in the positive and negative directions. Furthermore, the time interval T between is the intermittent time T i It is understood that, although preferably overlapping with, it is not necessary. Additionally, it is understood that at least one of the phase change rate and the noise sampling rate may be constant or may vary over time.

[0269] The noise cancellation subsystem 340 preferably operates at intermittent times T i It works by considering noise at,intermittent time Ti The noise cancellation subsystem 340 preferably uses an algorithm to detect noise and correct the detected noise accordingly.

[0270] According to one exemplary embodiment of the present invention, noise cancellation subsystem 340 uses an algorithm in which, during each cycle of movement of far-field intensity pattern 372 relative to detector 350, the relative phase of one channel is changed in such a way that the relative phase is modified by a given phase change Δφ. Following a number of such cycles in which a different phase change Δφ is applied to a selected sub-beam over each cycle, the algorithm checks for the maximum output intensity over all of the cycles and finds the optimal phase change Δφ that produced this maximum intensity. The phase change of the selected sub-beam is then fixed to the optimal phase change Δφ for the subsequent cycle, and the algorithm proceeds to optimize another sub-beam.

[0271] Graph 380 illustrates noise cancellation by this exemplary algorithm in channels A, B, and C for three sub-beams or a total of 10 sub-beams. For simplicity, sub-beams A, B, and C are shown alone in FIG. 3C. It will be appreciated that in FIG. 3C, the line style of the lines representing the phase changes and noise corrections for sub-beams A, B, and C, respectively, has been modified compared to FIGS. 3A and 3B to aid in distinguishing between the various sub-beams for purposes of discussion later herein.

[0272] As seen first for channel A, and most clearly understood from consideration of zoom 390, the dashed line represents the pattern of relative phase changes for sub-beam A that would be applied by phase control subsystem 330 in the absence of any noise correction. uncorrected The dotted and dashed lines represent the actual relative phase of sub-beam A as modified by the noise correction algorithm to find the optimal phase noise correction.corrected It is sometimes called. A corrected The corrected relative phase of A is uncorrected Δφ for the uncorrected relative phase of A The intensity 386 measured at detector 350 changes over the first five cycles of optimization of sub-beam A due to the intentional change in the relative phase shift.

[0273] After the first five cycles of sub-beam A, the algorithm identifies the maximum intensity and determines the phase change Δφ that produces the maximum intensity. A In this case, the maximum intensity occurs at the second phase shift Δφ A IA generated by max The phase change applied to the relative phase change of sub-beam A is therefore the second phase shift Δφ for the subsequent cycle. A and the algorithm proceeds to optimize sub-beam B.

[0274] It will be appreciated that during successive cycles of optimization of sub-beam A, the relative phases of the remaining portions of the sub-beams are each normally altered at a phase alteration rate that far exceeds the noise sampling rate at which noise in sub-beam A is taken into account.

[0275] As further seen in the case of sub-beam B, and most clearly understood from consideration of zoom 392, the thicker line during the optimization of channel B represents the pattern of relative phase changes for sub-beam B that would be applied by phase control subsystem 330 in the absence of any noise correction. uncorrected The thin line in the optimization for channel B represents the actual relative phase of sub-beam B as modified by the noise correction algorithm to find the optimal phase noise correction. corrected It is sometimes called B corrected The corrected relative phase of B is calculated over five cycles of the optimization sub-beam B. uncorrectedΔφ for the uncorrected relative phase of B The intensity 386 measured at detector 350 changes over these five cycles of optimization sub-beam B due to the intentional change in relative phase shift.

[0276] After these five cycles of sub-beam B, the algorithm identifies the maximum intensity and determines the phase change Δφ that produces the maximum intensity. B In this case, the maximum intensity is found at the fourth phase shift Δφ B Generated by IAB max The phase shift applied to the relative phase shift of sub-beam B is then a fourth phase shift Δφ for the subsequent cycle. B is fixed and the algorithm proceeds to optimize sub-beam C.

[0277] It is understood that during the five cycles of optimization of sub-beam B, the relative phases of the remaining parts of the sub-beam are each changed normally at a phase change rate that far exceeds the noise sampling rate at which noise in sub-beam B is taken into account.

[0278] Preferably, a similar optimization process is performed for sub-beam C, where the phase change Δφ is adjusted over several cycles to optimize the output beam intensity and correct for its intensity degradation due to phase noise in sub-beam C. C applies.

[0279] The detector 350 can operate continuously to continually optimize the relative phases of the sub-beams and correct for phase noise therein. However, due to the finite response time of the detector 350, the detector 350 only considers the noise in the reference beam 370 at intermittent times, at a relatively slow noise sampling rate. The noise sampling rate is preferably, but not necessarily, predetermined. Alternatively, the noise sampling rate may be random.

[0280] Those skilled in the art will appreciate that the specific parameters of the noise correction algorithm shown in graph 380 are merely exemplary and may be readily modified. For example, the phase shift Δφ may be optimized over a greater or lesser number of cycles than shown herein, each sub-beam may be fully optimized each time it passes through detector 350, or some or all of the sub-beams may be optimized during each cycle that the far-field intensity pattern passes through detector 350. Additionally, non-continuous noise correction optimization algorithms may alternatively be implemented, including, but not limited to, stochastic parallel gradient descent optimization algorithms.

[0281] The use of dynamically shaped, noise-compensated optical phased array output beams for free-space optical communications is highly advantageous, enabling rapid beam steering, fast power modulation, fast beam focusing, and beam shape adjustment. Compared to conventional free-space optical communications methods, the use of dynamically shaped, noise-compensated optical phased array outputs improves both the speed and quality of communications. It is understood that without the provision of noise compensation according to preferred embodiments of the present invention, the shape and position of the optical phased array output beam would be degraded, thereby degrading the quality, speed, and accuracy of the transmitted laser output.

[0282] To maintain output beam intensity as the beam's far-field intensity pattern moves, which can be advantageous in certain optical communications applications, the movement of the output beam can be controlled so that the beam spends more time at lower intensity positions to compensate for reduced power delivery there. Additionally or alternatively, an intensity profile mask, such as a neutral density filter, may be applied to the output beam to modify its intensity.

[0283] Reference is now made to FIG. 4A, which is a simplified schematic illustration of an optical phased array laser system for noise-compensated dynamic beam shaping, constructed and operative in accordance with yet another preferred embodiment of the present invention, and to FIGS. 4B and 4C, which are simplified graphical representations of phase modification and noise compensation within a system of the type shown in FIG. 4A.

[0284] 4A , an optical phased array (OPA) laser system 400 is provided, here shown, by way of example, for use within a laser welding system 402. The laser welding system 402 may include the OPA laser system 400 mounted on or within a portion of a laser welding robot 404. Articles, such as article 406, may be welded by the laser welding robot 404, as described in more detail below. While the laser welding system 402 is shown herein in the context of a welding robot 404, it is understood that the system 402 may be adapted for use in any welding setting, as will be understood by one of ordinary skill in the art.

[0285] As best seen in close-up view 410, OPA laser 400 preferably comprises a seed laser 412 and a laser beam splitting and combining subsystem 414. Splitting and combining subsystem 414 preferably receives the output laser beam from seed laser 412 and splits the output laser beam into multiple sub-beams along a corresponding number of channels 416. Here, merely by way of example, the output from seed laser 412 is shown as being split into ten sub-beams along ten channels 416, although it will be understood that splitting and combining subsystem 414 may include a fewer or greater number of channels along which the output of seed laser 412 is split, and may typically include a much greater number of channels, such as 32 or more channels.

[0286] The relative phase of each sub-beam may preferably be individually modulated by a phase modulator 418 positioned along each of the channels 416. Each phase-modulated sub-beam produced by splitting and subsequent phase modulation of the output of the seed laser 412 preferably propagates towards a collimating lens 419. The individually collimated and phase-modulated sub-beams are then combined, for example, at a focusing lens 420, to form an output beam 422.

[0287] The splitting and combining subsystem 414 can also preferably provide laser amplification of the sub-beams after splitting the output beam of the seed laser 412 into sub-beams and before combining the sub-beams to form the output beam 422. Here, by way of example, the splitting and combining subsystem 414 is shown to include multiple optical amplifiers 424 positioned along corresponding ones of the channels 416 for amplifying each sub-beam. However, it will be understood that such amplification is selectable and may be omitted depending on the power output requirements of the OPA laser 400.

[0288] The phase of output beam 422, and therefore the position and shape of its far-field intensity pattern, is controlled at least in part by the relative phases of the constituent sub-beams that are combined to form output beam 422. In many applications, such as laser welding as shown in FIG. 4A, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. This can be achieved in laser system 400 by laser splitting and combining subsystem 414 dynamically changing the relative phases of the individual sub-beams, thereby changing the phase of combined laser output 422 to dynamically control the position and shape of its far-field intensity pattern.

[0289] The relative phases of the sub-beams are preferably predetermined according to a desired laser output pattern for welding of article 406. Most preferably, the varying relative phases are applied by a phase control subsystem 430. Phase control subsystem 430 preferably forms part of a control electronics module 432 within OPA laser 400 and preferably controls each phase modulator 418 to dynamically modulate the relative phases of the sub-beams along channel 416.

[0290] Output beam 422 is noisy due to noise inherent in OPA system 400. The noise in output beam 422 is typically phase noise generated by thermal or mechanical effects and / or by the amplification process if optical amplifier 424 is present in OPA system 400. A particular feature of preferred embodiments of the present invention is that laser system 400 includes a noise cancellation subsystem 440 that operates to provide a noise-canceling phase-corrected output to cancel noise in output beam 422, in a manner described in more detail below.

[0291] Particularly preferably, noise cancellation subsystem 440 employs an algorithm to detect and correct phase noise in the combined laser output. A noise cancellation phase correction output is preferably provided by noise cancellation subsystem 440 to phase modulator 418 to correct for phase noise in output beam 422, thus avoiding distortions in the shape and position of the far-field intensity pattern of output beam 422 that would otherwise be caused by noise. Noise cancellation subsystem 440 may be included in control electronics module 432.

[0292] It is understood that output beam 422 may additionally or alternatively be affected by types of noise other than phase noise, including intensity noise. In the case of output beam 422 having intensity noise, noise cancellation subsystem 440 may operate to provide a noise-canceling phase-corrected output to cancel the intensity noise of output beam 422. In such cases, OPA laser system 400 may optionally additionally include intensity modulators 442 along channel 416 to modulate the intensity of each of the sub-beams along channel 416.

[0293] It is understood that output beam 422 may additionally or alternatively be affected by mechanical noise, which may affect the relative positions of the sub-beams. In the case of output beam 422 having position noise, noise cancellation subsystem 440 may operate to provide a noise-canceling phase-corrected output to cancel the position noise of output beam 422. In such cases, OPA laser system 400 may optionally additionally include a position modulator 444 along channel 416 to modulate the position of each of the sub-beams along channel 416.

[0294] To facilitate the application of phase modification and noise correction to output beam 422, a portion of the output of OPA laser 400 is preferably sampled and directed toward at least one detector, shown here as a single detector 450. Detector 450 may alternatively be embodied as multiple detectors, as described in more detail below with reference to FIGS. 6-8 and 15-21. The sampled portion of the output beam preferably serves as a reference beam, based on characteristics from which the necessary noise correction and / or phase modification may be calculated. In the embodiment shown in FIG. 4A, the multiple sub-beams along channel 416 are directed toward beam splitter 460. Beam splitter 460 preferably splits each sub-beam into a transmitted portion 462 and a reflected portion 464 according to a predetermined ratio. For example, beam splitter 460 may split each sub-beam with a 99.9% transmission:0.01% reflectance ratio.

[0295] The transmitted portions 462 of the sub-beams preferably propagate towards focusing lens 420, where the sub-beams combine to form output beam 422 having far-field intensity pattern 466 that is incident on article 406. The reflected portions 464 of the sub-beams preferably reflect towards additional focusing lens 468, where the sub-beams combine to form output reference beam 470 having far-field intensity pattern 472 that is incident on the surface of detector 450.

[0296] It is understood that the particular structures and configurations of the beam splitting and recombining elements shown herein, including beam splitter 460 and focusing lenses 420 and 468, are merely exemplary and are shown in highly simplified form. It is understood that OPA laser system 400 may include a variety of such elements, as well as additional optical elements, including, by way of example only, additional or alternative lenses, optical fibers, and coherent free-space far-field couplers.

[0297] As described hereinabove, the shape and position of far-field intensity pattern 466 of output beam 422 and the corresponding shape and position of far-field intensity pattern 472 of reference beam 470 are constantly changing due to ongoing modifications of the relative phases of the sub-beams. As a result, far-field intensity pattern 472 is not fixed to detector 450, but rather is constantly moving relative to detector 450 depending on the combined relative phases of the constituent sub-beams. However, in order for detector 450 to provide the necessary noise-canceling, phase-corrected output, far-field intensity pattern 472 must be incident on detector 450 so that the detector can measure the intensity of far-field intensity pattern 472 and therefore apply noise correction accordingly, resulting in a fixed output beam.

[0298] The conflict between the dynamic nature of far-field intensity pattern 472 due to its phase modification and the required fixed nature of far-field intensity pattern 472 in order to derive and apply noise correction is advantageously resolved in the present invention by providing noise cancellation and phase modification at different times and rates.

[0299] The noise cancellation phase corrected output is provided based on accounting for the noise measured at detector 450 at the noise sampling rate. Output beam 422 is controlled in such a way that far-field intensity pattern 472 is incident on detector 450 at a rate equal to or faster than the required noise sampling rate during dynamic changes to the shape and position of output and reference far-field intensity patterns 466, 472. The noise in reference beam 470 is accounted for during these intermittent times when far-field intensity pattern 472 is returned to detector 450.

[0300] During the time intervals between intermittent times when far-field intensity pattern 472 is incident on detector 450, the phase of combined output beams 422, 470 is varied to dynamically change the shape and position of that far-field intensity pattern as needed to perform laser welding of article 406. The combined laser output is varied at a phase change rate that exceeds the noise sampling rate to rapidly change the phase, and therefore the shape and position of the far-field intensity pattern. By way of example, the noise sampling rate may be on the order of 10-1000 Hz, while the phase change rate may be greater than 10,000 Hz.

[0301] The different rates and time scales at which noise cancellation and phase modification are preferably implemented in embodiments of the present invention can best be understood with reference to graph 480 seen in FIG. 4A and an expanded version thereof shown in FIG. 4B.

[0302] 4B , graph 480 includes an upper portion 482 that displays the change in intensity over time of far-field intensity pattern 472 measured by detector 450, and a lower portion 484 that displays the change over the same time period in the relative phase of multiple sub-beams that contribute to output beam 422 and reference beam 470. For simplicity, the relative phases of 10 sub-beams are displayed in graph 480, although it will be understood that OPA system 400, and therefore the description provided herein, is applicable to a fewer, or more typically, a much greater number of sub-beams.

[0303] As seen in upper portion 482, intensity peaks 486 represent the measured intensity of reference beam 470 as far-field intensity pattern 472 passes over detector 450. As seen in lower portion 484, intensity peaks 486 occur at discrete times T where the relative phase of each sub-beam is zero. i , which means that there is no phase shift between the sub-beams, and therefore the position of the combined output beam does not change, and thus far-field intensity pattern 472 is incident directly on detector 450. It will be appreciated that detector 450 may alternatively be positioned such that the relative phase of the sub-beams thereat is non-zero. Furthermore, as will be described in more detail below with reference to Figures 6-8 and 15-21, multiple detectors may be used, allowing far-field intensity pattern 472 to be measured at multiple positions along it.

[0304] Between intensity peaks 486, the measured intensity is near zero because far-field intensity pattern 472 is moved to either side of detector 450 and therefore is not directly incident on detector 450. As can be seen from an examination of upper portion 482, the magnitude of intensity peaks 486 is not constant due to the presence of noise in the laser output beam, which degrades far-field intensity pattern 472.

[0305] As can be seen in the lower portion 484, the relative phases of the sub-beams are discontinuous for a time T i The time interval T between betweenIn the phase modification functions shown herein, the relative phases of the sub-beams are shown to be modified in a periodic, regularly repeating pattern with equal phase shifts applied in the positive and negative directions. It will be understood that such a simplified pattern is merely illustrative, and that the phase modifications need not necessarily be regularly repeating, nor necessarily symmetrical in the positive and negative directions. Furthermore, the time interval T between is the intermittent time T i It is understood that, although preferably overlapping with, it is not necessary. Additionally, it is understood that at least one of the phase change rate and the noise sampling rate may be constant or may vary over time.

[0306] The noise cancellation subsystem 440 preferably operates at intervals T i It works by considering noise at,intermittent time T i The noise cancellation subsystem 440 preferably uses an algorithm to detect noise and correct the detected noise accordingly.

[0307] According to one exemplary embodiment of the present invention, noise cancellation subsystem 440 uses an algorithm in which, during each cycle of movement of far-field intensity pattern 472 relative to detector 150, the relative phase of one channel is changed in such a way that the relative phase is modified by a given phase change Δφ. Following a number of such cycles in which a different phase change Δφ is applied to a selected sub-beam over each cycle, the algorithm checks for the maximum output intensity over all of the cycles and finds the optimal phase change Δφ that produced this maximum intensity. The phase change of the selected sub-beam is then fixed to the optimal phase change Δφ for the subsequent cycle, and the algorithm proceeds to optimize another sub-beam.

[0308] Graph 480 illustrates noise cancellation by this exemplary algorithm in channels A, B, and C for three sub-beams or a total of 10 sub-beams. For simplicity, sub-beams A, B, and C are shown alone in FIG. 4C. It will be appreciated that in FIG. 4C, the line style of the lines representing the phase changes and noise corrections for sub-beams A, B, and C, respectively, has been modified compared to FIGS. 4A and 4B to aid in distinguishing between the various sub-beams for purposes of discussion later herein.

[0309] As seen first for channel A, and most clearly understood from consideration of zoom in 490, the dashed line represents the pattern of relative phase changes for sub-beam A that would be applied by phase control subsystem 430 in the absence of any noise correction. uncorrected The dotted and dashed lines represent the actual relative phase of sub-beam A as modified by the noise correction algorithm to find the optimal phase noise correction. corrected It is sometimes called. A corrected The corrected relative phase of A is uncorrected Δφ for the uncorrected relative phase of A The intensity 486 measured at detector 450 changes over the first five cycles of optimization of sub-beam A due to the intentional change in the relative phase shift.

[0310] After the first five cycles of sub-beam A, the algorithm identifies the maximum intensity and determines the phase change Δφ that produces the maximum intensity. A In this case, the maximum intensity occurs at the second phase shift Δφ A IA generated by max The phase change applied to the relative phase change of sub-beam A is therefore the second phase shift Δφ for the subsequent cycle. A and the algorithm proceeds to optimize sub-beam B.

[0311] It will be appreciated that during successive cycles of optimization of sub-beam A, the relative phases of the remaining portions of the sub-beams are each normally altered at a phase alteration rate that far exceeds the noise sampling rate at which noise in sub-beam A is taken into account.

[0312] As further seen in the case of sub-beam B, and most clearly understood from consideration of zoom-in view 492, the thicker line during the optimization of channel B represents the pattern of relative phase changes for sub-beam B that would be applied by phase control subsystem 430 in the absence of any noise correction. uncorrected The thin line in the optimization for channel B represents the actual relative phase of sub-beam B as modified by the noise correction algorithm to find the optimal phase noise correction. corrected It is sometimes called B corrected The corrected relative phase of B is calculated over five cycles of the optimization sub-beam B. uncorrected Δφ for the uncorrected relative phase of B The intensity 486 measured at detector 450 changes over these five cycles of optimized sub-beam B due to the intentional change in relative phase shift.

[0313] After these five cycles of sub-beam B, the algorithm identifies the maximum intensity and determines the phase change Δφ that produces the maximum intensity. B In this case, the maximum intensity is found at the fourth phase shift Δφ B Generated by IAB max The phase change applied to the relative phase change of sub-beam B is then a fourth phase shift Δφ for the subsequent cycle. B is fixed and the algorithm proceeds to optimize sub-beam C.

[0314] It is understood that during the five cycles of optimization of sub-beam B, the relative phases of the remaining sub-beams are each changed normally at a phase change rate that far exceeds the noise sampling rate at which the noise of sub-beam B is taken into account.

[0315] Preferably, a similar optimization process is performed for sub-beam C, where the phase change Δφ is adjusted over several cycles to optimize the output beam intensity and correct for its intensity degradation due to phase noise in sub-beam C. C applies.

[0316] Detector 450 can operate continuously to continually optimize the relative phases of the sub-beams and correct for phase noise therein. However, due to the finite response time of detector 450, detector 450 only considers noise in reference beam 470 at intermittent times, at a relatively slow noise sampling rate. The noise sampling rate is preferably, but not necessarily, predetermined. Alternatively, the noise sampling rate may be random.

[0317] Those skilled in the art will appreciate that the specific parameters of the noise correction algorithm shown in graph 480 are merely exemplary and may be readily modified. For example, the phase shift Δφ may be optimized over a greater or lesser number of cycles than shown herein, each sub-beam may be fully optimized each time it passes through detector 450, or some or all of the sub-beams may be optimized during each cycle that the far-field intensity pattern passes through detector 450. Additionally, non-continuous noise correction optimization algorithms may alternatively be implemented, including, but not limited to, stochastic parallel gradient descent optimization algorithms.

[0318] The use of a dynamically shaped, noise-compensated optical phased array output beam for laser welding is highly advantageous, enabling rapid beam steering, fast power modulation, fast beam focusing, and beam shape adjustment. Compared to conventional laser cutting methods, the use of a dynamically shaped, noise-compensated optical phased array output improves both the speed and quality with which materials can be cut. It is understood that without the provision of noise compensation in accordance with preferred embodiments of the present invention, the shape and position of the optical phased array output beam would be degraded, thereby degrading the quality, speed, and accuracy of the laser cutting process.

[0319] To maintain output beam intensity as the far-field intensity pattern of the beam moves, which can be advantageous in certain laser cutting applications, the movement of the output beam can be controlled so that the beam spends more time at lower intensity positions to compensate for reduced power delivery there. Additionally or alternatively, an intensity profile mask, such as a neutral density filter, may be applied to the output beam to modify its intensity.

[0320] Referring now to Figures 5A-5G, Figures 5A-5G are simplified schematic diagrams of possible far-field motion of the output of an optical phased array laser system of the type shown in Figures 1A-4C.

[0321] As detailed above, the use of dynamically shaped, noise-compensated optical phased array output beams in various laser applications, including but not limited to laser cutting, laser additive manufacturing, laser welding, and laser free-space optics, is highly advantageous, enabling rapid beam steering, fast power modulation, fast beam focusing, and beam shape adjustment. Exemplary far-field patterns illustrating rapid beam steering according to embodiments of the present invention are shown in FIGS. 5A and 5B. These beam steering patterns may be provided in combination to complement mechanical spatial modulation of the beam, such as mechanical beam steering. The mechanical beam steering may result from motion provided by the positioning table 104 shown in FIG. 1A, from mirror scanning such as in an additive manufacturing system of the type shown in FIG. 2A, from mechanical motion between the laser system 300 and the receiver 303 shown in FIG. 3A, from motion provided by a robot 404 shown in FIG. 4A, or from any other source of mechanical motion.

[0322] The mechanical motion may be desired or undesired. Preferably, the far-field rapid beam steering provided by embodiments of the present invention complements the mechanical motion to achieve the desired combined beam motion. The desired combined motion may be faster and / or more accurate than would be produced as a result of mechanical beam modulation alone.

[0323] As can be seen in FIG. 5A, the dynamically shaped, noise-compensated optical phased array output beam may exhibit rapid multi-point jumps, as shown by the first beam path 502, which complement the beam motion due to mechanical scanning, as represented by the second beam path 504.

[0324] By way of example, such multi-point jumps may be advantageous in material processing, where it takes time for energy to be absorbed at each point in the processed material. Multi-point jumps allow the beam to jump between points and return to each point multiple times, thus facilitating parallel processing of many points. Further by way of example, such multi-point jumps may be advantageous in communication systems, where transmission to multiple locations can occur in parallel.

[0325] As seen in FIG. 5B, the use of a dynamically shaped, noise-compensated optical phased array output beam also facilitates rapid scanning, as shown by the third beam path 506, which complements the beam motion due to mechanical scanning, represented by the fourth beam path 508. Such rapid scanning facilitates continuous, smooth mechanical beam motion, the fine features of which can be provided by far-field dynamic shaping according to embodiments of the present invention. Furthermore, dynamically noise-compensated far-field modulation can be provided in combination with mechanical beam motion to correct for inaccuracies that may exist in the mechanically modulated beam pattern.

[0326] An exemplary far-field beam pattern exhibiting electro-optic beam wobble according to a preferred embodiment of the present invention is shown in Figure 5C. As can be seen in Figure 5C, the dynamically shaped, noise-compensated optical phased array output beam is controlled to exhibit a rapid beam wobble 510 along the direction of beam motion 512, which is particularly useful in laser welding systems such as that shown in Figure 4A.

[0327] Exemplary far-field beam patterns illustrating dynamic modification of depth of focus according to preferred embodiments of the present invention are shown in Figures 5D-5F. As can be seen in Figures 5D-5F, the depth of the beam focus may be dynamically varied by the system of the present invention, enabling variable beam focal lengths for scanning (Figure 5E) and deep cutting (Figures 5D and 5F), and is particularly useful in cutting, additive manufacturing, and welding systems of the type shown in Figures 1A, 2A, and 4A, for example.

[0328] An exemplary far-field beam pattern illustrating dynamic beam shaping according to a preferred embodiment of the present invention is shown in FIG. 5G. As seen in FIG. 5G, the shape of the beam may be dynamically changed to produce a desired beam shape output. This may be particularly useful in cutting, additive manufacturing, and welding systems of the type shown in FIGS. 1A, 2A, and 4A, for example, as well as in other contexts. As is well known in the art, the quality and speed of laser cutting, welding, and 3D printing are typically affected by the size and shape of the beam. The present invention allows for the beam to be dynamically adapted to an optimal shape at any point.

[0329] It will be appreciated that the various far-field beam motion patterns shown in Figures 5A-5G are all preferably generated by the system of the present invention using digital electronic control and without the need for any moving parts.

[0330] Reference is now made to FIG. 6, which is a simplified schematic diagram of an optical phased array laser system including multiple detectors and corresponding multiple closely spaced optical paths, constructed and operative in accordance with a preferred embodiment of the present invention.

[0331] As seen in FIG. 6 , an optical phased array (OPA) laser 600 is provided. The OPA laser 600 may generally be of the type shown in any of FIGS. 1A-4C and preferably includes a seed laser 612 and a laser beam splitting and combining subsystem 614. The splitting and combining subsystem 614 preferably receives the output laser beam from the seed laser 612 and splits the output laser beam into multiple sub-beams along a corresponding number of channels 616. Here, merely by way of example, the output from the seed laser 612 is shown as being split into four sub-beams along four channels 616, although it will be understood that the splitting and combining subsystem 614 may include a fewer or greater number of channels along which the output of the seed laser 612 is split, and may typically include a much greater number of channels, such as 32 or more channels.

[0332] The relative phase of each sub-beam may preferably be individually modulated by a phase modulator 618 positioned along each of channels 616. Each phase-modulated sub-beam produced by splitting and subsequent phase modulation of the output of seed laser 612 preferably propagates toward a collimating lens 619. The individually collimated and phase-modulated sub-beams are then combined, for example, at a focusing lens 620, to form output beam 622.

[0333] Splitting and combining subsystem 614 can also preferably provide laser amplification of the sub-beams after splitting the output beam of seed laser 612 into sub-beams and before combining the sub-beams to form output beam 622. Here, by way of example, splitting and combining subsystem 614 is shown to include multiple optical amplifiers 624 positioned along corresponding ones of channels 616 for amplifying each sub-beam. However, it will be understood that such amplification is selectable and may be omitted depending on the power output specifications of OPA laser 600.

[0334] The phase of output beam 622, and therefore the position and shape of its far-field intensity pattern, is controlled at least in part by the relative phases of the constituent sub-beams that are combined to form output beam 622. As described herein above with reference to Figures 1A-5G, in many applications, such as laser cutting, laser welding, laser additive manufacturing, and optical free-space communications, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. This can be achieved in laser system 600 by laser splitting and combining subsystem 614 dynamically changing the relative phases of the individual sub-beams, thereby changing the phase of combined laser output 622 to dynamically control the position and shape of its far-field intensity pattern.

[0335] The relative phases of the sub-beams are preferably predetermined according to a desired laser output pattern. Particularly preferably, the varying relative phases are applied by a phase control subsystem 630. The phase control subsystem 630 preferably forms part of a control electronics module 632 within the OPA laser 600 and preferably controls each phase modulator 618 to dynamically modulate the relative phases of the sub-beams along the channel 616, as described herein above with reference to the phase control subsystems 130, 230, 330, and 430 of FIGS. 1A, 2A, 3A, and 4A, respectively.

[0336] Output beam 622 is noisy due to noise inherent in OPA system 600. The noise in output beam 622 is typically phase noise generated by thermal or mechanical effects and / or by the amplification process if optical amplifier 624 is present in OPA system 600. OPA system 600 preferably includes a noise cancellation subsystem 640 that operates to provide a noise-canceling phase-corrected output to cancel the noise in output beam 622, in a manner described in more detail below.

[0337] Particularly preferably, noise cancellation subsystem 640 employs an algorithm to detect and correct phase noise in the combined laser output, preferably, but not necessarily, of the type described herein above with reference to Figures 1A-4C. A noise cancellation phase correction output is preferably provided by noise cancellation subsystem 640 to phase modulator 618 to correct for phase noise in output beam 622, thus avoiding distortions in the shape and position of the far-field intensity pattern of output beam 622 that would otherwise be caused by noise. Noise cancellation subsystem 640 may be included in control electronics module 632.

[0338] To facilitate the application of phase modifications and noise corrections to output beam 622, a portion of the output of OPA laser 600 is preferably sampled and directed towards multiple detectors 650. The sampled portion of the output beam preferably serves as a reference beam based on characteristics from which the necessary noise corrections and / or phase modifications can be calculated.

[0339] In accordance with a preferred embodiment of the present invention, the multiple sub-beams along channel 616 are directed toward beam splitter 660. Beam splitter 660 preferably splits each sub-beam into a transmitted portion 662 and a reflected portion 664 according to a predetermined ratio. For example, beam splitter 660 may split each sub-beam with a 99.9% transmittance:0.01% reflectance ratio.

[0340] The transmitted portions 662 of the sub-beams preferably propagate towards a focusing lens 620 where the sub-beams combine to form an output beam 622 having a far-field intensity pattern 666. The reflected portions 664 of the sub-beams preferably reflect towards an additional focusing lens 668 where the sub-beams combine to form an output reference beam 670 having a far-field intensity pattern 672 that is incident on the surface of one or more of the plurality of detectors 650.

[0341] 1A-4C, the noise cancellation phase correction output is preferably provided based on taking into account the noise measured at detector 650 at the noise sampling rate. Output beam 622 is controlled in such a way that far-field intensity pattern 672 is incident on detector 650 at a rate equal to or faster than the required noise sampling rate during dynamic changes to the shape and position of output and reference far-field intensity patterns 666, 672. The noise in reference beam 670 is taken into account during these intermittent times when far-field intensity pattern 672 is returned to detector 650.

[0342] During the time intervals between intermittent times when far-field intensity pattern 672 is incident on detector 650, the phase of combined output beams 622, 670 is altered to dynamically change the shape and position of that far-field intensity pattern. The combined laser outputs are altered at a rate of phase change that exceeds the noise sampling rate to rapidly change the phase, and therefore the shape and position of the far-field intensity pattern. Thus, noise cancellation and phase alteration are preferably provided at different times and rates from one another.

[0343] The use of multiple detectors 650, rather than a single detector, has been found to be highly advantageous in certain embodiments of the present invention, providing various benefits detailed below. However, if the focal length of the additional focusing lens 668 is relatively short, as is desirable to make the system 600 compact, the detectors of the multiple detectors 650 preferably need to be positioned very closely together. The desired inter-detector spacing may be on the order of several microns. Such a high spatial density arrangement of detectors 650 is typically impractical, especially for conventional detectors that have dimensions much larger than the preferred inter-detector spacing.

[0344] To enable high spatial density sampling of far-field intensity pattern 672 by multiple detectors 650, OPA system 600 preferably includes multiple optical paths, here illustratively embodied as multiple optical fibers 680, that are correspondingly coupled to multiple detectors 650. Reference beam 670 preferably enters one or more of multiple open ends 682 of optical fibers 680 and travels along them to corresponding detectors among detectors 650. Multiple ends 682 of multiple optical fibers 680 are preferably arranged to have a spatial density that is greater than the spatial density of multiple detectors 650, meaning that the spacing between open ends 682 of adjacent optical fibers of optical fibers 680 is less than the spacing between corresponding adjacent detectors of detector 650. This enables detector 650 to detect closely spaced far-field intensity pattern 672 along them without the detectors themselves having to be physically positioned at the closely spaced locations of detector 650 where far-field intensity pattern 672 is sampled.

[0345] By way of example, ends 682 of optical fibers 680 may be spaced apart by a distance of a few microns, while detectors 650 coupled to corresponding ones of optical fibers 680 may be spaced apart by a distance of a few millimeters. It will be appreciated that such an arrangement allows for the use of conventional detectors in system 600, obviating the need for expensive and complex miniaturized detection systems.

[0346] The inclusion of multiple detectors 650, effectively closely spaced as facilitated by the actual close physical spacing of ends 682 of optical fibers 680, has been found to be highly advantageous in preferred embodiments of the present invention. In particular, as shown in Figures 1A, 2A, 3A, and 4A, the use of multiple detectors 650 rather than just a single detector 150 allows far-field intensity pattern 672 to be sampled at multiple locations rather than just a single location. This facilitates more efficient and / or more frequent noise correction during dynamic changes of output beam 622.

[0347] It will be appreciated that the closely spaced multiple optical paths are not limited to being embodied as multiple optical fibers 680 whose ends 682 are spaced very closely together and have an end-to-end spacing between the fibers that is less than the inter-detector spacing of detector 650. Rather, the scope of the present invention extends to include any suitable multiple optical paths along which the far-field intensity reference pattern 672 can be delivered to multiple detectors 650 and which can be arranged at a sufficiently large spatial density.

[0348] 7, the closely spaced optical paths may be embodied as lenses 780. The lenses 780 may be very closely spaced to focus portions of the far-field intensity reference pattern 672 toward the more closely spaced detectors 650. By way of further example, as shown in FIG. 8, the closely spaced optical paths may be embodied as mirrors 880 operating in cooperation with corresponding lenses 882. The mirrors 880 may be very closely spaced to reflect portions of the far-field intensity reference pattern 672 toward the more closely spaced detectors 650.

[0349] It will be understood that an OPA laser system of the type shown in any of Figures 6-8 including multiple detectors can be incorporated into an OPA laser system of the type shown in any of Figures 1A, 2A, 3A, and 4A to provide more efficient and / or more frequent noise correction to its phase-altered output.

[0350] Reference is now made to FIG. 9, which is a simplified schematic diagram of an optical phased array laser system including a detector mask configured in accordance with an exemplary laser beam trajectory, constructed and operative in accordance with a preferred embodiment of the present invention.

[0351] As seen in Figure 9, an optical phased array (OPA) laser 900 is provided. OPA laser 900 may be generally similar in its relevant aspects to OPA laser 600 of Figure 6, except for the detector arrangement used therein. OPA laser 600 preferably employs multiple detectors that receive the output beam via corresponding closely spaced optical paths, although OPA laser 900 does not necessarily employ multiple detectors.

[0352] 9 is that the OPA laser 900 preferably includes an optical mask 980 having at least one transmissive region 982 for providing the output reference beam 670 through the transmissive region 982 to at least one detector 650; the OPA laser 900 is shown here with a single detector 650. The optical mask 980 is preferably an optically opaque element that is transmissive to the beam 670 only in the transmissive region 982. Here, by way of example, the transmissive region 982 is shown formed as a star-shaped transmission path configured according to the star-shaped trajectory of the output and reference far-field intensity patterns 666, 672.

[0353] Output reference beam 670 preferably passes through transparent region 982 and is focused onto detector 650 by a focusing subsystem, here illustratively embodied as focusing lens 990. A noise cancellation phase corrected output is preferably provided by noise cancellation subsystem 630 based on considering the intensity of far-field intensity pattern 672 focused onto and incident on detector 650.

[0354] More specifically, the phases of output and reference beams 622, 670 are preferably dynamically varied by phase control subsystem 630 so that output and reference beams 622, 670 traverse predetermined trajectories, such as star-shaped trajectories, corresponding to the shape of star-shaped transmission region 982. In the absence of noise in OPA laser 900, the trajectories traversed by output and reference beams 622, 670 will at least approximately exactly correspond to the shape of transmission region 982, resulting in the intensity of far-field intensity pattern 672 detected by detector 650 being at its maximum, undegraded intensity. However, due to the presence of noise in output and reference beams 622, 670, the trajectory and shape of far-field intensity pattern 672 will deviate somewhat from the shape of transmission region 982, resulting in a portion of reference beam 670 impinging on an opaque region of mask 980 rather than on transmission region 982 and therefore not being transmitted through transmission region 982 to detector 650. In such a case, the intensity of the far-field intensity pattern 672 detected by the detector 650 is less than the maximum intensity that would be detected in the absence of noise.

[0355] Therefore, degradation in the intensity of the far-field intensity pattern 672 measured by the detector 650 preferably indicates noise-combined distortions in the trajectories of the output and reference beams 622, 670, and may thereby be used to derive the required noise cancellation phase correction output to be applied by the noise cancellation subsystem 640.

[0356] It will be appreciated that the above-described arrangement of detectors 650 positioned behind mask 980 allows for the use of only a single detector 650 to sense the output intensity of reference beam 670 along its beam trajectory, and to apply noise cancellation phase correction output based thereon. This is in contrast to alternative detector arrangements that do not include mask 980, such as those described herein above with reference to Figures 6-8, in which multiple detectors may be used to provide sufficiently efficient and / or frequent noise correction during dynamic changes of output beam 622.

[0357] In addition to changes in the intensity of reference beam 670 measured by detector 650 due to noise-induced distortions in the beam trajectory, the intensity of reference beam 670 may also change along the trajectory of reference beam 670, typically due to intrinsic intensity changes in far-field intensity pattern 672. This can complicate the noise correction feedback provided by detector 650, as changes in the intensity of reference beam 670 may be due to noise or intrinsic intensity changes unrelated to noise.

[0358] To improve the reliability of the noise correction feedback provided by detector 650, the transparent region 982 of mask 980 may be provided with regions of varying transparency, the transparency levels of which are set to compensate for inherent intensity variations in reference beam 670 along its trajectory.

[0359] A highly simplified representation of a transparent region 982 of a mask 980 having non-uniform transparency is shown in FIG. 10. As seen in FIG. 10, a first portion of the transparent region 982 defined between a first point P1 and a second point P2 of the transparent region 982 may have a first transparency T1. A second portion of the transparent region 982 defined between a second point P2 and a third point P3 may have a second transparency T2 that is different from the first transparency T1. A third portion of the transparent region 982 defined between a third point P3 and a fourth point P4 may have a first transparency T1. A fourth portion of the transparent region 982 defined between a fourth point P4 and a fifth point P5 may have a third transparency T3 that is different from the first and second transparency T1 and T2. A fifth point of the transmissive region 982 defined between the fifth point P5 and the first point P1 may have a second transparency T2.

[0360] It will be appreciated that various portions of the transmissive region 982 may have discretely different transparency values, or the transparency of the transmissive region 982 may vary gradually across its various portions in accordance with the intensity compensation requirements of the far field intensity pattern 672.

[0361] Preferably, but not necessarily, mask 980 is an electronically modulated device such as an LCD screen or similar device, so that the characteristics of transmission region 982 may be easily electronically modified according to the output characteristics of reference beam 670.

[0362] 9 and 10 are merely exemplary, and it will be understood that the transmission region 982 may be configured according to any locus of the output and reference far-field intensity patterns 666 and 672. Additionally, it will be understood that the transmission region 982 may include multiple transmission regions. In such cases, a single detector 650 may be used to receive light from all of the transmission regions, or a corresponding number of detectors may be positioned for each transmission region.

[0363] Furthermore, as will be described in more detail with reference to Figures 11 and 12, it will be appreciated that the transmission region 982 may additionally or alternatively be configured according to the shape of the output and reference far-field intensity patterns 666 and 672 rather than their trajectories.

[0364] Reference is now made to FIG. 11, which is a simplified schematic diagram of an optical phased array laser system including a detector mask configured in accordance with an exemplary laser beam shape, constructed and operative in accordance with another preferred embodiment of the present invention.

[0365] 11, system 1100, which is generally similar in relevant respects to system 900, may include an optical mask 1180 having at least one transmissive region 1182 that replaces optical mask 980 of FIGS. 9 and 10. Optical mask 1180 may be similar in all relevant respects to optical mask 980, except that transmissive region 1182 is configured according to the shape of reference beam 670 rather than its trajectory. Here, by way of example, transmissive region 1182 is shown to be a bowtie-shaped transmissive region configured according to bowtie-shaped output and reference far-field intensity patterns 666 and 672.

[0366] Transmissive region 1182 may have a non-uniform transparency, a highly simplified representation of which is shown in FIG. 12. As seen in FIG. 12, a first portion of transmissive region 1182 may have a first transparency T1, and a second portion of transmissive region 1182 may have a second transparency T2 that is different from the first transparency T1. As detailed herein with reference to FIG. 10, varying levels of transparency of transmissive region 1182 may be used to compensate for inherent intensity modifications of output beam 670 and thus improve the noise-corrected output provided based on the intensity detected at detector 650.

[0367] It will be appreciated that the transmissive regions 982 and 1182 of the masks 980 and 1180, respectively, may additionally or alternatively be embodied as reflective regions that reflect the output reference beam 670 therefrom toward the detector 650. Such an arrangement would require appropriate modifications and / or additions to a focusing subsystem, here embodied, by way of example, as a focusing lens 990, to direct the output reference beam 670 from the reflective regions 982, 1182 to the surface of the detector 650. The reflective regions of the masks 980 and 1180 may have a uniform reflectivity. Alternatively, as described herein above, the reflective regions of the masks 980 and 1180 may have a non-uniform reflectivity to compensate for inherent intensity variations in the output reference beam 670.

[0368] If masks 980 and 1180 include reflective regions, masks 980 and 1180 may be embodied as electrically modulated devices such as digital micromirror devices (DMDs) or other similar devices.

[0369] It will be understood that an OPA laser system of the type shown in any of Figures 9-12, which includes at least one detector receiving an output reference beam through a transmissive or reflective optical mask, can be incorporated into an OPA laser system of the type shown in any of Figures 1A, 2A, 3A, and 4A to provide more efficient noise correction to its phase-altered output.

[0370] Reference is now made to FIG. 13, which is a simplified schematic diagram of an optical phased array laser system including voltage phase correlation functionality, constructed and operative in accordance with a preferred embodiment of the present invention.

[0371] As seen in Figure 13, an OPA laser system 1300 is provided. The OPA laser 1300 may have a type generally similar to the OPA lasers 100, 200, 300, and 400 described herein above with reference to Figures 1A-4C. The OPA laser 1300 preferably includes a seed laser 1312 and a laser beam splitting and combining subsystem 1314. The splitting and combining subsystem 1314 preferably receives the output laser beam from the seed laser 1312 and splits the output laser beam into multiple sub-beams along a corresponding plurality of channels 1316.

[0372] The relative phase of each sub-beam may preferably be individually modulated by a phase modulator 1318 positioned along each of the channels 1316. Each phase-modulated sub-beam produced by splitting and subsequent phase modulation of the output of the seed laser 1312 preferably propagates toward a collimating lens 1319. The individually collimated, phase-modulated sub-beams are then combined, for example, at the focal plane of lens 1320, to form output beam 1322.

[0373] Splitting and combining subsystem 1314 can also preferably provide laser amplification of the sub-beams after splitting the output beam of seed laser 1312 into sub-beams and before combining the sub-beams to form output beam 1322. Here, by way of example, splitting and combining subsystem 1314 is shown to include multiple optical amplifiers 1324 positioned along corresponding ones of channels 1316 for amplifying each sub-beam. However, it will be understood that such amplification is selectable and may be omitted depending on the power output specifications of OPA laser 1300.

[0374] The phase of output beam 1322, and therefore the position and shape of its far-field intensity pattern, is controlled at least in part by the relative phases of the constituent sub-beams that are combined to form output beam 1322. In many applications, such as laser cutting, laser welding, free-space optics, and laser additive manufacturing, as described hereinabove, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. As described hereinabove with reference to FIGS. 1A-4C , dynamic variation of the parameters of the output beam can be achieved by dynamically varying the relative phases of the individual sub-beams along channel 1316, thereby varying the phase of combined laser output 1322 to dynamically control the position and shape of its far-field intensity pattern.

[0375] The relative phases of the sub-beams are preferably predetermined according to the desired laser output pattern. Particularly preferably, the varying relative phases are applied by a phase modulation control module 1330. The phase modulation control module 1330 preferably provides a voltage to the phase modulator 1318 so that the phase modulator 1318 generates the desired phase modulation of the sub-beams along the channel 1316. It will be appreciated that the phase modulation control module 1330, in combination with the phase modulator 1318, forms a particularly preferred embodiment of a phase modulation subsystem 1332, which preferably operates to vary the phase of the combined laser output 1322.

[0376] To facilitate application of a phase modification to output beam 1322, a portion of the output of OPA laser 1300 is preferably sampled and directed toward at least one detector 1350. The sampled portion of the output beam preferably serves as a reference beam based on characteristics from which the necessary phase modification can be calculated. In the embodiment shown in FIG. 13, the multiple sub-beams along channel 1316 are directed toward beam splitter 1360. Beam splitter 1360 preferably splits each sub-beam into a transmitted portion 1362 and a reflected portion 1364 according to a predetermined ratio. For example, beam splitter 1360 may split each sub-beam with a 99.9% transmission:0.01% reflectance ratio.

[0377] The transmitted portions 1362 of the sub-beams preferably propagate towards a focusing lens 1320 where the sub-beams combine to form an output beam 1322 having a far-field intensity pattern 1366. The reflected portions 1364 of the sub-beams preferably propagate towards an additional focusing lens 1368 where the sub-beams combine to form an additional reference beam 1370 having a far-field intensity pattern 1372 that is incident on the surface of detector 1350.

[0378] Detector 1350 preferably samples far-field intensity pattern 1372 incident thereon. Although detector 1350 is shown in Figure 13 as embodied as a single detector that directly receives far-field intensity pattern 1372, it will be understood that multiple detectors may alternatively be used according to any of the multiple detector arrangements shown in any of Figures 6-8. Alternatively, a single detector such as detector 1350 may be used in conjunction with an optical mask according to any of the arrangements shown in any of Figures 9-12.

[0379] Detector 1350 cooperates with phase modulation subsystem 1332, which then preferably optimizes the relative phases of the sub-beams to achieve desired far-field intensity pattern 1372 and corresponding far-field intensity pattern 1366. Various algorithms suitable for phase optimization include iterative or non-iterative optimization algorithms, including the phase optimization regimes described herein above with reference to Figures 1A-4C.

[0380] In operation of phase modulation subsystem 1332, phase modulation control module 1330 preferably applies voltages to each of phase modulators 1318 and 1318, resulting in a phase modulated output corresponding to the applied voltages. It will be appreciated that in order for phase modulators 1318 to generate the phase shifts necessary to dynamically shape far-field intensity pattern 1366 according to a predetermined pattern, phase modulation control module 1330 must apply to each phase modulator 1318 precisely the voltages that correspond to the particular phase modulated output required to be generated by each phase modulator 1318.

[0381] To ensure that the voltage applied to phase modulator 1318 by phase modulation control module 1330 produces the phase modulated output required and intended by phase modulator 1318, OPA laser 1300 preferably includes a voltage-to-phase correlation subsystem 1380. Voltage-to-phase correlation subsystem 1380 preferably operates to correlate the voltage applied to phase modulation subsystem 1332 with the phase modulated output produced by phase modulation subsystem 1332, and more specifically, by its phase modulator 1318.

[0382] Additionally, the voltage to phase correlation subsystem 1380 preferably operates to provide a voltage to phase correlation output useful in calibrating the phase modulation subsystem 1332. Preferably, the voltage to phase correlation subsystem periodically performs a correlation between the voltage and the phase modulation output during the course of changing the phase of the combined laser output 1322.

[0383] It will be appreciated that the inclusion of a correlation and calibration subsystem, such as voltage-to-phase correlation subsystem 1380, in OPA laser 1300 is highly advantageous, as it ensures that the voltage applied to phase modulator 1318 is the voltage necessary to produce the desired phase shift in output beam 1322 and, therefore, the shape of far-field intensity pattern 1366. This is particularly important given that phase modulators suitable for use in preferred embodiments of the present invention are typically highly sensitive devices, and different ones typically exhibit different voltage-phase relationships. Furthermore, the voltage-phase relationship of an individual phase modulator is not constant but can change over time and depending on operating conditions.

[0384] It will be understood that the phase modulation and calibration provided by phase modulation control module 1330 and voltage-phase correlation control module 1380, respectively, are preferably, but not necessarily, performed in conjunction with application of noise correction to the output of OPA laser 1300 when the output of laser 1300 is noisy. In this case, phase modulation control module 1330 and voltage-phase correlation control module 1380 can be considered to combine to form particularly preferred embodiments of phase control subsystems such as phase control subsystems 130 (FIG. 1A), 230 (FIG. 2A), 330 (FIG. 3A), and 430 (FIG. 4A).

[0385] An exemplary voltage-phase correlation and calibration regime suitable for use in the present invention is shown in flowchart 1400 of Figure 14. However, it is understood that the particular steps of flowchart 1400 are merely exemplary, and that voltage-phase correlation subsystem 1380 can be implemented as any suitable subsystem within OPA laser 1300 that is capable of calibrating phase modulation subsystem 1332 periodically during phase changes of output beam 1322. Furthermore, it is understood that the various steps shown in flowchart 1400 do not necessarily have to be performed in the order shown and described, and that various of the steps may be omitted or supplemented by additional or alternative steps, as would be apparent to one of ordinary skill in the art.

[0386] As seen in a first step 1402, the phase modulation control module 1330 preferably applies a voltage to the phase modulator 1318 to generate a desired phase shift of the sub-beam along the channel 1316. The far-field intensity pattern of the reference output beam 1372 is then measured with the detector 1350, as seen in a second step 1404. The required phase shift of the sub-beam is then confirmed, and a voltage is again applied to the phase modulator 1318. The application of a voltage in the first step 1402 and the measurement of the reference output beam 1372 in the second step 1404 may be repeated periodically multiple times at a given repetition rate. By way of example only, the first and second steps may be repeated 20 times at a rate of 1 million times per second.

[0387] Following a predetermined number of repetitions, e.g., 20 repetitions, of the first and second steps 1402, 1404, the voltage-to-phase correlation subsystem 1380 may be activated. As seen in a third step 1406, a voltage intended to generate a 2π phase shift is preferably applied to one phase modulator 1318. As seen in a fourth step 1408, the intensity of the far-field intensity pattern 1372 is then preferably measured with a detector 1350.

[0388] Then, in a fifth step 1410, the phase shift of far-field intensity pattern 1372 is checked to see if it is zero. It is understood that if the voltage applied in third step 1406 is indeed a voltage that produces a 2π phase shift, then the phase shift of beam 1322 will be zero, and therefore the intensity of far-field intensity pattern 1372 will not change with the applied voltage. In this case, the phase modulator 1318 to which the 2π phase shift was applied in third step 1406 is known to be correctly calibrated, and no further calibration of that particular phase modulator 1318 is necessary.

[0389] It is further understood that if the voltage applied in third step 1406 does not produce a phase shift of 2π, then the phase shift of beam 1322 will be non-zero and, therefore, the intensity of far field intensity pattern 1372 will vary in response to the applied voltage, as found to be the case in seventh step 1414. In this case, a relationship between the applied voltage and the resulting phase shift is preferably derived in seventh step 1414. Phase modulator 1318 is then preferably calibrated according to the voltage-phase relationship derived in seventh step 1414, as seen in eighth step 1416.

[0390] Following calibration of a particular phase modulator 1318 in eighth calibration step 1416 or confirmation of proper calibration of a particular phase modulator 1318 in fifth step 1410, as seen in query 1418, the voltage-to-phase correlation subsystem 1380 preferably checks whether a predetermined number of phase modulators 1318 have been calibrated, as seen in a predetermined ninth step 1420, and proceeds to calibrate the next phase modulator if necessary. The voltage-to-phase correlation subsystem 1380 may sequentially calibrate all phase modulators 1318 included in the system 1300, or may sequentially calibrate a predetermined number of phase modulators 1318, such as N phase modulators 1318. Once the predetermined number of phase modulators 1318 have been calibrated, the subsystem 1380 is preferably deactivated, and phase modification of the output beam 1322 resumes at step 1402.

[0391] It is understood that the frequency at which the voltage to phase correlation subsystem 1380 is activated is preferably significantly lower than the frequency at which the phase changes of the output beam 1322 are performed. By way of example, the phase changes of the output beam 1322 may be performed one million times per second, and the voltage to phase correlation may be activated once per second.

[0392] Furthermore, although flowchart 1400 does not include steps for noise correction, it will be understood that such noise correction may be applied in the process of phase shifting the sub-beams contributing to output beam 1322, as described herein above with reference to Figures 1A-4C.

[0393] Reference is now made to FIG. 15, which is a simplified schematic plan view of an optical phased array laser system including dynamic beam scaled phase modification, constructed and operative in accordance with an additional preferred embodiment of the present invention.

[0394] As seen in FIG. 15 , an optical phased array (OPA) laser system 1500 is provided, which may be of the type outlined herein with reference to FIGS. 1A-4C . The OPA laser 1500 preferably includes a seed laser 1512 and a laser beam splitting and combining subsystem 1514. The splitting and combining subsystem 1514 preferably receives the output laser beam from the seed laser 1512 and splits the output laser beam into a plurality of sub-beams along a corresponding plurality of channels 1516. Here, by way of example only, the output from the seed laser 1512 may be split into a 4×4 matrix of 16 sub-beams along 16 corresponding channels 1516, four of which sub-beams and channels 1516 are shown in the top view of the OPA laser 1500 in FIG. 15 . However, it will be understood that the splitting and combining subsystem 1514 may include a fewer or greater number of channels into which the output of the seed laser 1512 is split, and may typically include a much larger number of channels, such as 32 or more channels.

[0395] The relative phase of each sub-beam may preferably be individually modulated by a phase modulator 1518 positioned along each of the channels 1516. Each phase-modulated sub-beam produced by splitting and subsequent phase modulation of the output of the seed laser 1512 preferably propagates toward a collimating lens 1519. The individually collimated, phase-modulated sub-beams are then combined, for example, at the focal plane of lens 1520, to form output beam 1522.

[0396] Splitting and combining subsystem 1514 can also preferably provide laser amplification of the sub-beams after splitting the output beam of seed laser 1512 into sub-beams and before combining the sub-beams to form output beam 1522. Here, by way of example, splitting and combining subsystem 1514 is shown to include multiple optical amplifiers 1524 positioned along corresponding ones of channels 1516 for amplifying each sub-beam. However, it will be understood that such amplification is selectable and may be omitted depending on the power output specifications of OPA laser 1500.

[0397] The phase of output beam 1522, and therefore the position and shape of its far-field intensity pattern, is controlled at least in part by the relative phases of the constituent sub-beams that are combined to form output beam 1522. As described hereinabove, in many applications, such as laser cutting, laser welding, free-space optical communications, and laser additive manufacturing, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. As described hereinabove with reference to FIGS. 1A-4C , dynamic variation of the parameters of the output beam can be achieved by dynamically varying the relative phases of the individual sub-beams along channel 1516, thereby varying the phase of combined laser output 1522 to dynamically control the position and shape of its far-field intensity pattern.

[0398] For an OPA laser 1500 that includes a large number of individual sub-beams, measuring and corresponding phase correction of each sub-beam relative to the phase of all other sub-beams of the sub-beam may be difficult due to the large number of individual sub-beams involved. Specifically, due to the large number of individual sub-beams contributing to the combined output 1522, the time it takes to measure and correct the phase of each individual sub-beam relative to the other sub-beams in order to dynamically control the phase of the combined laser output 1522 may be unacceptably long. Furthermore, the signal-to-noise ratio may be unacceptably low.

[0399] A particular feature of preferred embodiments of the present invention is that the OPA laser 1500 includes a phase modulation subsystem 1530 for performing phase modulation of the combined laser output in an enhanced manner. More specifically, the phase modulation subsystem 1530 preferably groups at least a portion of the sub-beams provided by the laser splitting and combining subsystem 1514 into groups and then performs phase modulation within each group of sub-beams only on other sub-beams within the group. Such group phase modulation is preferably performed in parallel across various individual groups of sub-beams. The phase modulation subsystem 1530 then preferably optimizes the phase of each group of sub-beams relative to the phase of other groups of sub-beams to alter the phase of the combined laser output 1522 in a manner described in more detail below.

[0400] The phase modulation subsystem 1530 preferably includes a phase control electronics module 1532 in operational control of the phase modulators 1518. The phase control electronics module 1532 preferably controls each phase modulator 1518 to dynamically modulate the relative phase of the sub-beams along the channel 1516 according to the desired far-field intensity pattern of the output beam 1522 as seen by the phase modulation subsystem 1530.

[0401] To facilitate application of a phase modification to output beam 1522, a portion of the output of OPA laser 1500 is preferably sampled and directed toward multiple detectors 1550. The sampled portion of the output beam preferably serves as a reference beam based on characteristics from which the required phase modification can be calculated. In the embodiment shown in FIG. 15, the multiple sub-beams along channel 1516 are directed toward beam splitter 1560. Beam splitter 1560 preferably splits each sub-beam into a transmitted portion 1562 and a reflected portion 1564 according to a predetermined ratio. For example, beam splitter 1560 may split each sub-beam with a 99.9% transmittance:0.01% reflectance ratio.

[0402] The transmitted portions 1562 of the sub-beams preferably propagate toward a focusing lens 1520 where the sub-beams combine to form an output beam 1522 having a far-field intensity pattern 1566. The reflected portions 1564 of the sub-beams preferably propagate toward a cylindrical lens 1568. The cylindrical lens 1568 preferably operates to receive the reflected portions 1564 of the sub-beams and group the sub-beams into multiple groups by focusing the sub-beams along the direction of curvature of the lens 1568. Here, by way of example, the sub-beams are shown as being focused into four groups 1570, with each group 1570 consisting of four sub-beams.

[0403] Preferably, each group 1570 of sub-beams grouped by cylindrical lens 1568 forms a beam having a far-field intensity pattern 1572 incident on a surface of a corresponding one of the plurality of detectors 1550. Each detector 1550 preferably samples the group far-field intensity pattern 1572 incident thereon. Each detector 1550, in cooperation with a corresponding control electronics sub-module 1574 included in control module 1532, then preferably optimizes the relative phase of the sub-beams within the group of sub-beams 1570 sampled thereby relative to the phases of the other sub-beams within the group 1570. Such sampling and optimization is preferably performed in parallel, preferably simultaneously, for the far-field intensity patterns 1572 across all detectors 1550. Various algorithms suitable for phase optimization include sequential or non-sequential optimization algorithms, including noise correction algorithms, as described above with reference to FIGS. 1A-4C.

[0404] To optimize the relative phase of each of the groups 1570 with respect to the other groups of groups 1570, a portion of the groups 1570 is preferably directed by an auxiliary beam splitter 1580 to an auxiliary cylindrical lens 1582. It will be appreciated that, in order to focus the sub-beams, the curvature of the auxiliary cylindrical lens 1582 is preferably orthogonal to the curvature of the cylindrical lens 1568. The auxiliary cylindrical lens 1582 preferably focuses the group of sub-beams 1570 into a single beam 1584 having a far-field intensity pattern 1586 that is incident on an auxiliary detector 1588. The auxiliary detector 1588 preferably receives therein the single beam having the far-field intensity pattern 1586 that corresponds to the combined pattern of all groups of sub-beams 1570. The auxiliary detector 1588 preferably cooperates with an additional phase control electronics sub-module 1590 included in the electronic control module 1532 to sample and optimize the phases of the groups 1570 with respect to one another. Particularly preferably, one function of the phase control electronics module 1532 is to control each phase modulator 1518 to apply a phase shift that maximizes the total power of the auxiliary detectors 1588 .

[0405] It will be appreciated that performing phase modulation in the expanded manner described above, in which the phase of each sub-beam is optimized with respect to the phases of the other sub-beam members of its group 1570, and the phases of the groups 1570 are optimized with respect to each other to change the phase of the combined laser output 1522, is much quicker and less complicated than optimizing the phase of each individual sub-beam with respect to the phases of all other sub-beams in the OPA 1500. Furthermore, this allows phase optimization to be performed by individual sets of control electronics in each control electronics sub-module 1574 respectively coupled to each detector 1550, rather than requiring a single set of control electronics, improving the signal-to-noise ratio.

[0406] It will be appreciated that the function of optimizing the relative phase of each of the groups 1570 with respect to the other groups of the group 1570 may alternatively be performed by an additional group phase modulator operative to modulate the collective phase of each of the groups 1570, rather than by an individual phase modulator 1518 operative to modulate the individual phase of each sub-beam member of each of the groups 1570. An exemplary implementation of such an arrangement is shown in FIG. 16 and may be generally similar to the phase modulation configuration described in U.S. Pat. No. 9,893,494, the disclosure of which is incorporated herein by reference.

[0407] As seen in Figure 16, system 1500 may be modified by adding a series of group phase modulators corresponding to the number of groups 1570. Here, by way of example, as seen in Figure 16, system 1500 may include 16 sub-beams, four of which are included in each of four groups 1570, resulting in a total of four additional group phase modulators 1618 being included in system 1500. Each group phase modulator 1618 is preferably common to the four channels 1516 that form part of each group 1570 and provides a phase shift that optimizes the collective group phase of the sub-beams along the four channels 1516 connected to it.

[0408] Preferably, the group phase modulators of the group phase modulators 1618 are controlled by an additional control sub-module 1690, which is preferably included in the control module 1532. The auxiliary detector 1588 is preferably coupled to the additional control sub-module 1690. It will be appreciated that comparing and optimizing the relative phases of the groups 1570 with each other by the group phase modulator 1618, rather than by the individual sub-beam phase modulators 1518, may be more efficient and simplify the phase modulation process, but requires the use of additional phase modulators and circuit elements, thus increasing the cost and complexity of the system 1500.

[0409] The alteration of the phase of the combined laser output 1522 preferably provides spatial modulation of the output 1522. It is understood that due to the extended nature of the phase modulation performed by the phase modulation subsystem 1530, the phase of the combined laser output 1522 may be altered very rapidly, at a rate faster than that achievable by a mechanical spatial modulation mechanism. The spatial modulation provided by the OPA laser 1500 may optionally be augmented by additional mechanical spatial modulation mechanisms, as known in the art, or may not include mechanical spatial modulation.

[0410] It is understood that the particular structures and arrangements of optical elements shown herein, including beam splitter 1560, focusing lens 1520, cylindrical lens 1568, auxiliary beam splitter 1580, and auxiliary cylindrical lens 1582, are merely exemplary and are shown in highly simplified form. It is understood that OPA laser system 1500 may include a variety of such elements, as well as additional optical elements, including, by way of example only, additional or alternative lenses, optical fibers, and coherent free-space far-field couplers.

[0411] It will further be appreciated that cylindrical lens 1568 may have optical properties that group the individual sub-beams into similar or identical groups containing an equal number of sub-beams, or alternatively, cylindrical lens 1568 may have optical properties that group the individual sub-beams into different groups containing different numbers of sub-beams.

[0412] An exemplary implementation of an OPA laser system of the type shown in FIG. 15 or 16 is shown in FIGS. 17A and 17B. Referring now to FIGS. 17A and 17B, an OPA laser system 1700 is provided in which an output laser beam from a seed laser (not shown), such as seed laser 1512, is split into multiple sub-beams along corresponding channels 1716. By way of example, the laser output may be split into a 10×10 matrix of 100 sub-beams along 100 corresponding channels 1716. It will be understood that for clarity of presentation, only selected ones of the sub-beams are shown in FIG. 17B. The sub-beams along channels 1716 may then be collimated and focused by collimating and focusing elements (not shown), such as collimating and focusing lenses 1519, 1520, to generate a combined output beam.

[0413] To facilitate application of phase modifications to the output beam, a portion of the output of the OPA laser 1700 is preferably sampled and directed toward a plurality of detectors 1750. The sampled portion of the output beam preferably serves as a reference beam based on characteristics from which the required phase modification can be calculated. In the embodiment shown in Figures 17A and 17B, the multiple sub-beams along the channel 1716 are directed toward a beam splitter 1760. The beam splitter 1760 preferably splits each sub-beam into a transmitted portion 1762 and a reflected portion 1764 according to a predetermined ratio.

[0414] The transmitted portions 1762 of the sub-beams are preferably combined to form an output beam. The reflected portions 1764 of the sub-beams are preferably reflected towards a cylindrical lens 1768, which is a particularly preferred embodiment of cylindrical lens 1568. The cylindrical lens 1768 preferably operates to receive the reflected portions 1764 of the sub-beams and focus the sub-beams into multiple groups along the direction of curvature of the cylindrical lens 1768. As an example, for 100 sub-beams, the cylindrical lens 1768 may focus the sub-beams into 10 groups 1770 of 10 sub-beams.

[0415] Preferably, each group 1770 of sub-beams grouped by cylindrical lens 1768 forms a beam having a far-field intensity pattern that is incident on a surface of a corresponding one of the plurality of detectors 1750. By way of example, the plurality of detectors 1750 may include ten detectors 1750, each sampling a group beam that includes ten individual sub-beams. Each detector 1750 cooperates with a corresponding control electronics module (not shown), such as control module 1532, which then preferably optimizes the phase of the sub-beams included in the group 1770 of sub-beams sampled by it. Such sampling and optimization is preferably performed in parallel across all of the detectors 1750, preferably simultaneously.

[0416] To optimize the relative phase of each of the groups 1770 with respect to the phase of the other groups of the group 1770, a portion of the group 1770 is preferably directed by the auxiliary beam splitter 1780 to the auxiliary cylindrical lens 1782. It will be appreciated that the auxiliary cylindrical lens 1782 is a particularly preferred embodiment of the auxiliary cylindrical lens 1582. It will be appreciated that in order to focus the sub-beams, the curvature of the auxiliary cylindrical lens 1782 is preferably orthogonal to the curvature of the cylindrical lens 1768. The auxiliary cylindrical lens 1782 preferably focuses the group of sub-beams 1770 into one combined beam 1784 that is incident on the auxiliary detector 1788.

[0417] Auxiliary detector 1788 preferably receives a far-field intensity pattern corresponding to the combined pattern of all groups of sub-beams 1770 and cooperates with phase control electronics (not shown) to sample and optimize the phases of groups 1770 relative to one another. It will be appreciated that optimization of the phases of groups 1770 relative to one another may be by phase modulation of the phases of individual sub-beams by phase modulator 1518, as described herein above with reference to FIG. 15, or by phase modulation of the phases of groups of sub-beams by group phase modulator 1618, as described herein above with reference to FIG. 16.

[0418] Reference is now made to FIG. 18, which is a simplified schematic plan view of an optical phased array laser system including dynamic beam scaled phase modification, constructed and operative in accordance with another preferred embodiment of the present invention.

[0419] As seen in FIG. 18 , an optical phased array (OPA) laser system 1800 is provided, which may be of the type outlined herein with reference to FIGS. 1A-4C . The OPA laser 1800 preferably includes a seed laser 1812 and a laser beam splitting and combining subsystem 1814. The splitting and combining subsystem 1814 preferably receives an output laser beam from the seed laser 1812 and splits the output laser beam into a plurality of sub-beams along a corresponding plurality of channels 1816. Here, by way of example only, the output from the seed laser 1812 may be split into a 4×4 matrix of 16 sub-beams along 16 corresponding channels 1816, four of which sub-beams and channels 1816 are shown in the top view of the OPA laser 1800 in FIG. 18 . However, it will be understood that the splitting and combining subsystem 1814 may include a fewer or greater number of channels into which the output of the seed laser 1812 is split, and may typically include a much larger number of channels, such as 32 or more channels.

[0420] The relative phase of each sub-beam may preferably be individually modulated by a phase modulator 1818 positioned along each of channels 1816. Each phase-modulated sub-beam produced by splitting and subsequent phase modulation of the output of seed laser 402 preferably propagates toward a collimating lens 1819. The individually collimated and phase-modulated sub-beams are then combined, for example, at the focal plane of lens 1820, to form output beam 1822.

[0421] Splitting and combining subsystem 1814 can also preferably provide laser amplification of the sub-beams after splitting the output beam of seed laser 1812 into sub-beams and before combining the sub-beams to form output beam 1822. Here, by way of example, splitting and combining subsystem 1814 is shown to include multiple optical amplifiers 1824 positioned along corresponding ones of channels 1816 for amplifying each sub-beam. However, it will be understood that such amplification is selectable and may be omitted depending on the power output requirements of OPA laser 1800.

[0422] The phase of output beam 1822, and therefore the position and shape of its far-field intensity pattern, is controlled at least in part by the relative phases of the constituent sub-beams that are combined to form output beam 1822. As described hereinabove, in many applications, such as laser cutting, laser welding, free-space optical communications, and laser additive manufacturing, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. As described hereinabove with reference to FIGS. 1A-4C , dynamic variation of the parameters of the output beam can be achieved by dynamically varying the relative phases of the individual sub-beams along channel 1816, thereby varying the phase of combined laser output 1822 to dynamically control the position and shape of its far-field intensity pattern.

[0423] For an OPA laser 1800 that includes a large number of individual sub-beams, measuring and corresponding phase correction of each sub-beam relative to the phase of all other sub-beams of the sub-beam may be difficult due to the large number of individual sub-beams involved. Specifically, due to the large number of individual sub-beams contributing to the combined output 1822, the time it takes to measure and correct the phase of each individual sub-beam relative to the other sub-beams in order to dynamically control the phase of the combined laser output 1822 may be unacceptably long. Furthermore, the signal-to-noise ratio may be unacceptably low.

[0424] It is a particular feature of preferred embodiments of the present invention that the OPA laser 1800 includes a phase modulation subsystem 1830 for performing phase modulation of the combined laser output in an enhanced manner. More specifically, the phase modulation subsystem 1830 preferably groups at least a portion of the sub-beams provided by the laser splitting and combining subsystem into groups and then performs phase modulation within each group of sub-beams only relative to the phase of the other sub-beams in the group. Such group phase modulation is preferably performed in parallel across the various individual groups. The phase modulation subsystem 1830 then preferably optimizes the phase of each group of sub-beams relative to the phase of the other groups of sub-beams to alter the phase of the combined laser output 1822 in a manner described in more detail below.

[0425] Phase modulation subsystem 1830 preferably includes a phase control electronics module 1832 in operational control of phase modulators 1818. Phase control electronics module 1832 preferably controls each phase modulator 1818 to dynamically modulate the relative phase of the sub-beams along channel 1816 according to the desired far-field intensity pattern of output beam 1822 as seen by phase modulation subsystem 1830.

[0426] To facilitate application of phase modifications to output beam 1822, a portion of the output of OPA laser 1800 is preferably sampled and directed toward multiple detectors 1850. The sampled portion of the output beam preferably serves as a reference beam based on characteristics from which the necessary phase modifications can be calculated. In the embodiment shown in FIG. 18 , the multiple sub-beams along channel 1816 are directed toward beam splitter 1860. Beam splitter 1860 preferably splits each sub-beam into a transmitted portion 1862 and a reflected portion 1864 according to a predetermined ratio. For example, beam splitter 1860 may split each sub-beam with a 99.9% transmission:0.01% reflectance ratio.

[0427] The transmitted portions 1862 of the sub-beams preferably propagate toward a focusing lens 1820 where the sub-beams combine to form an output beam 1822 having a far-field intensity pattern 1866. The reflected portions 1864 of the sub-beams preferably reflect toward an array of mirrors 1868, each mirror 1868 positioned in spaced relationship to a corresponding focusing lens 1869. By way of example, the mirror array 1868 may comprise four mirrors 1868 positioned in spaced relationship to four focusing lenses 1869, two of which are visible in the top view of system 1800 in FIG.

[0428] Mirror 1868 is preferably angled to reflect the sub-beams incident thereon toward corresponding focusing lenses 1869, thereby operating to group the reflected portions 1864 of the sub-beams into a number of groups, here embodied by way of example as four groups 1870, each group 1870 containing four sub-beams, two of which are seen in the top view of system 18100 in FIG. 18.

[0429] Preferably, each group of sub-beams reflected from each of mirrors 1868 is focused by a corresponding focusing lens 1869 to form a single beam 1870 comprising the group of sub-beams and having a far-field intensity pattern 1872 that is incident on a surface of a corresponding detector of the plurality of detectors 1850. Each detector 1850, in cooperation with a corresponding control electronics sub-module 1874 included in control module 1832, then preferably optimizes the relative phase of the sub-beams within the group of sub-beams 1870 sampled thereby relative to the phases of the other sub-beams within group 1870. Such sampling and optimization is preferably performed in parallel, preferably simultaneously, for the far-field intensity patterns of far-field intensity patterns 1872 across all detectors 1850. Various algorithms suitable for phase optimization include sequential or non-sequential optimization algorithms, including noise correction algorithms, described herein above with reference to FIGS. 1A-4C.

[0430] To optimize the relative phase of each of the groups 1870 with respect to the other groups of groups 1870, a portion of the reflected portion 1864 is preferably directed to an auxiliary lens 1882, preferably via an auxiliary beam splitter 1880. The auxiliary lens 1882 preferably focuses the sub-beams incident thereon into a single beam 1884 having a far-field intensity pattern 1886 that is incident on an auxiliary detector 1888. The auxiliary detector 1888 preferably receives therefrom the single beam having the far-field intensity pattern 1886 that corresponds to the combined pattern of all groups of sub-beams 1870. The auxiliary detector 1888 preferably cooperates with a phase control electronics sub-module 1890 included in the electronic control module 1832 to sample and optimize the phases of the groups 1870 with respect to each other. Particularly preferably, one function of the phase control electronics module 1832 is to control each phase modulator 1818 to apply a phase shift that maximizes the total power of the auxiliary detector 1888.

[0431] It will be appreciated that performing phase modulation in the expanded manner described above, in which the phase of each sub-beam is optimized relative to the phase of the other sub-beam members of its group 1870, and the phases of the group 1870 are optimized relative to each other to change the phase of the combined laser output 1822, is much quicker and less complicated than optimizing the phase of each individual sub-beam relative to the phase of all other sub-beams in OP 1800. Furthermore, this allows phase optimization to be performed by individual sets of control electronics in each control electronics sub-module 1874 coupled to each detector 1850, rather than requiring a single set of control electronics, improving the signal-to-noise ratio.

[0432] It will be appreciated that the function of optimizing the relative phase of each of the groups 1870 with respect to the other groups of the group 1870 may alternatively be performed by an additional group phase modulator operative to modulate the collective phase of each of the groups 1870, rather than by an individual phase modulator 1818 operative to modulate the individual phase of each sub-beam member of each of the groups 1870. An exemplary implementation of such an arrangement is shown in FIG. 19, which in some aspects may be generally similar to the phase modulation configuration described in U.S. Pat. No. 9,893,494.

[0433] As seen in Figure 19, system 1800 may be modified by adding a series of group phase modulators corresponding to the number of groups 1870. Here, by way of example, as seen in Figure 19, system 1800 may comprise 16 sub-beams, four of which are included in each of four groups 1870, resulting in a total of four additional group phase modulators 1918 being included in system 1800. Each group phase modulator 1918 is preferably common to the four channels 1816 that form part of each group 1870 and provides a phase shift that optimizes the collective group phase of the sub-beams along the four channels 1816.

[0434] Preferably, the group phase modulators of group phase modulators 1918 are controlled by an additional control sub-module 1990, which is preferably included in control module 1832. Auxiliary detector 1888 is preferably coupled to the additional control sub-module 1990. It will be appreciated that comparing and optimizing the relative phases of groups 1870 with one another by group phase modulator 1918, rather than by individual sub-beam phase modulators 1818, may be more efficient and simplify the phase modulation process, but requires the use of additional phase modulators and circuit elements, thus increasing the cost and complexity of system 1800.

[0435] The alteration of the phase of the combined laser output 1822 preferably provides spatial modulation of the output 1822. It is understood that due to the extended nature of the phase modulation performed by the phase modulation subsystem 1830, the phase of the combined laser output 1822 may be altered very rapidly, at a rate faster than that achievable by a mechanical spatial modulation mechanism. The spatial modulation provided by the OPA laser 1800 may optionally be augmented by additional mechanical spatial modulation mechanisms, as known in the art, or may not include mechanical spatial modulation.

[0436] It is understood that the particular structure and arrangement of optical elements shown herein, including beam splitter 1860, focusing lens 1820, mirror array 1868, and corresponding focusing lens 1869, are merely exemplary and are shown in highly simplified form. It is understood that OPA laser system 1800 may include a variety of such elements, as well as additional optical elements, including, by way of example only, additional or alternative lenses, optical fibers, and coherent free-space far-field couplers.

[0437] It will further be understood that the mirrors 1868 and corresponding focusing lenses 1869 may have similar or identical optical properties to group the individual sub-beams into similar or identical groups containing equal numbers of sub-beams. Alternatively, the mirrors 1868 and corresponding focusing lenses 1869 may have different optical properties to group the individual sub-beams into different groups containing different numbers of sub-beams.

[0438] An exemplary implementation of an OPA laser system of the type shown in Figures 18 or 19 is shown in Figures 20A and 20B. Referring now to Figures 20A and 20B, an OPA laser system 2000 is provided in which an output laser beam from a seed laser (not shown), such as seed laser 1812, is split into multiple sub-beams along corresponding multiple channels 2016. Here, by way of example only, the laser output may be split into a 10 x 10 matrix of 100 sub-beams along corresponding 100 channels 2016, with only selected ones of the sub-beams shown in Figure 20B for clarity of presentation. The sub-beams along channels 2016 can then be collimated and focused by collimating and focusing elements (not shown), such as collimating and focusing lenses 1819, 1820, to generate a combined output beam.

[0439] To facilitate application of phase modifications to the output beam, a portion of the output of OPA laser 2000 is preferably sampled and directed toward a plurality of detectors 2050. The sampled portion of the output beam preferably serves as a reference beam based on characteristics from which the required phase modification can be calculated. In the embodiment shown in Figures 20A and 20B, the multiple sub-beams along channel 2016 are directed toward beam splitter 2060. Beam splitter 2060 preferably splits each sub-beam into a transmitted portion 2062 and a reflected portion 2064 according to a predetermined ratio.

[0440] The transmitted portions 2062 of the sub-beams are preferably combined to form an output beam. The reflected portions 2064 of the sub-beams are preferably reflected towards an array of mirrors 2068, each mirror 2068 positioned in spaced relation to a corresponding focusing lens 2069. It will be appreciated that the array of mirrors 2068 and lens 2069 are particularly preferred embodiments of the array of mirrors 1868 and focusing lens 1869.

[0441] Mirrors 2068 are preferably angled to reflect the sub-beams incident thereon toward corresponding focusing lenses 2069, thereby operative to group reflected portions 2064 of the sub-beams into multiple groups, here embodied as four groups by way of example, with each group 2070 including 25 sub-beams. Preferably, each set of sub-beams reflected by each of mirrors 2068 is focused by a corresponding focusing lens 2069 to form a single beam including a group of 25 sub-beams 2070. Each group of sub-beams 2070 is incident on a surface of a corresponding one of multiple detectors 2050. Each detector 2050 preferably samples the far-field intensity pattern incident thereon. Each detector 2050 cooperates with a corresponding control electronics sub-module (not shown), such as control electronics sub-module 1874 included in control module 1832, which then preferably optimizes the phase of the sub-beams included in the group of sub-beams 2070 sampled thereby so that the combined phases produce the desired group far-field intensity pattern. Such sampling and optimization is preferably performed in parallel, preferably simultaneously, for the far-field intensity patterns of the far-field intensity patterns across all detectors 2050 .

[0442] To optimize the relative phase of each of the groups 2070 with respect to the other groups of the groups 2070, a portion of the reflected portion 2064 is preferably directed by an auxiliary beam splitter 2080 to an auxiliary lens 2082. The auxiliary lens 2082 preferably focuses the portion of the reflected portion 2064 into a single beam 2084 that is incident on an auxiliary detector 2088. The auxiliary detector 2088 preferably receives therein a single beam having a far-field intensity pattern that corresponds to the pattern of all of the combined sub-beams. The auxiliary detector 2088 preferably cooperates with phase control electronics included in the electronic control module 1832 to sample and optimize the phases of the groups 2070 with respect to one another.

[0443] It will be appreciated that optimization of the phase of the groups 2070 relative to each other may be by phase modulation of the phase of individual sub-beams by a phase modulator 1818, as described herein above with reference to FIG. 18, or by phase modulation of the phase of a group of sub-beams by a group phase modulator 1918, as described herein above with reference to FIG. 19.

[0444] In the above-described embodiments of OPA lasers 1500, 1700, 1800, and 2000 of Figures 15-20B, it will be understood that phase modulation is preferably performed in an enhanced manner using multiple detectors, such as detectors 1550, 1750, 1850, 2050, used to simultaneously perform phase measurements on sub-beams in multiple groups, and a single detector, such as auxiliary detectors 1586, 1786, 1886, 2086, used to perform phase measurements on a single beam comprising multiple groups.

[0445] However, it will be appreciated that a system constructed and operated in accordance with a preferred embodiment of the present invention may be further expandable to include additional layers of detectors and corresponding optical elements, depending on the number of sub-beams involved.

[0446] 21, the OPA laser system 1500 may be modified to further include an additional focusing lens 2102 for focusing the group 1570 of sub-beams into an intermediate group 2104, where the intermediate group is incident on an intermediate detector 2106. The intermediate groups 2104 are then further combined and incident on a single detector 2108, where the single detector 2108 intermediate groups 2104 are preferably phase corrected relative to each other.

[0447] It is additionally understood that any of the OPA laser systems described herein above with reference to Figures 15-21 may be modified by replacing one or more of the individual detectors in the OPA laser system with multiple detectors and corresponding multiple closely spaced optical paths to improve sampling of the output beam in accordance with the embodiments of the present invention described herein above with reference to Figures 6-8. Furthermore, any of the OPA laser systems described herein above with reference to Figures 15-21 may alternatively be modified to include a transmissive or reflective detector mask that masks one or more of the multiple detectors used in the OPA laser system in accordance with the embodiments of the present invention described herein above with reference to Figures 9-12 to further improve sampling of the output beam.

[0448] It is further understood that any of the OPA laser systems described herein above with reference to Figures 15-21 may be modified to include a voltage-phase calibration function in accordance with the preferred embodiment of the present invention described herein above with reference to Figures 13 and 14 to ensure proper calibration of the phase modulators used therein.

[0449] Reference is now made to FIGS. 22A and 22B, which are simplified schematic diagrams of first and second focal states, respectively, of an optical phased array laser system constructed and operative in accordance with a preferred embodiment of the present invention.

[0450] As seen in Figures 22A and 22B, a laser system 2200 is provided that preferably includes an optical phased array (OPA) laser 2202. The OPA laser system 2200 may be of the type outlined in commonly assigned U.S. Patent No. 9,584,224 or U.S. patent application Ser. No. 15 / 406,032, the contents of which are incorporated herein by reference. Alternatively, the OPA laser system 2200 may be of the type described with reference to any one or combination of Figures 1A-21 herein above.

[0451] As best seen in close-up view 2210, OPA laser 2202 preferably includes a seed laser 2212 and a laser beam splitting and combining subsystem 2214 that receives the laser output from seed laser 2212 and provides a combined laser output. Laser beam splitting and combining subsystem 2214 preferably includes a plurality of phase modulators 2218 for altering the phase of the combined laser output following splitting of the laser output from seed laser 2212 and prior to the combining performed by splitting and combining subsystem 2214.

[0452] Each phase-modulated sub-beam produced by splitting and subsequent phase modulation of the output of seed laser 2212 preferably propagates towards collimating lens 2219. The individually collimated and phase-modulated sub-beams are then combined, for example, at focusing lens 2220, to form output beam 2222.

[0453] Splitting and combining subsystem 2214 can also preferably provide laser amplification of the sub-beams after splitting the output beam of seed laser 2212 into sub-beams and before combining the sub-beams to form output beam 2222. Here, by way of example, splitting and combining subsystem 2214 is shown to include multiple optical amplifiers 2224 for amplifying each sub-beam. However, it will be understood that such amplification is selectable and may be omitted depending on the power output specifications of OPA laser 2200.

[0454] The phase of output beam 2222, and therefore the position and shape of its far-field intensity pattern, is controlled at least in part by the relative phases of the constituent sub-beams that are combined to form output beam 2222. As described herein above with reference to Figures 1A-5G, in many applications such as laser cutting, laser welding, laser additive manufacturing, and optical free-space communications, it is desirable to dynamically move and shape the far-field intensity pattern of output beam 2222. This can be achieved in laser system 2200 by laser splitting and combining subsystem 2214 dynamically changing the relative phases of the individual sub-beams, thereby changing the phase of combined laser output 2222 to dynamically control the position and shape of its far-field intensity pattern.

[0455] The relative phases of the sub-beams are preferably predetermined according to the desired laser output pattern. Particularly preferably, the varying relative phases are applied by phase control subsystem 2230. Phase control subsystem 2230 preferably forms part of control electronics module 2232 within OPA laser system 2200 and preferably controls each phase modulator 2218 to dynamically modulate the relative phases of the sub-beams, as described herein above with reference to phase control subsystems 130, 230, 330, 430 of FIGS. 1A, 2A, 3A, and preferably 4A, respectively.

[0456] Output beam 2222 may have noise due to noise inherent in OPA system 2200. The noise in output beam 2222 is typically phase noise generated by thermal or mechanical effects and / or by the amplification process if optical amplifier 2224 is present in OPA system 2200. If output beam 2222 has noise, OPA system 2200 may include a noise cancellation subsystem 2240 that operates to provide a noise-canceled phase-corrected output to cancel the noise in output beam 2222, in a manner described in more detail below.

[0457] Particularly preferably, noise cancellation subsystem 2240 employs an algorithm to detect and correct phase noise in the combined laser output, preferably, but not necessarily, of the type described herein above with reference to Figures 1A-4C. A noise cancellation phase correction output is preferably provided by noise cancellation subsystem 2240 to phase modulator 2218 to correct for phase noise in output beam 2222, thus avoiding distortions in the shape and position of the far-field intensity pattern of output beam 2222 that would otherwise be caused by noise. Noise cancellation subsystem 2240 may be included in control electronics module 2232.

[0458] Alternatively, if the noise in output beam 2222 is not severe, noise cancellation subsystem 2240 may be removed from OPA system 2200, for which no noise correction is performed.

[0459] To facilitate application of phase modifications and noise corrections relative to output beam 2222, a portion of the output of OPA laser 2202 is preferably extracted and directed toward at least one detector 2250. Here, by way of example, at least one detector 2250 is shown embodied as a single detector 2250. However, it will be understood that at least one detector 2250 may be embodied as multiple detectors receiving portions of the output of OPA laser 2202 via closely spaced optical paths, as described herein above with reference to FIGS. 6-8, or as at least one detector receiving portions of the output of OPA laser 2202 via a transmissive or reflective optical mask, as described herein above with reference to FIGS. 9-12. The extracted portion of the output beam preferably serves as a reference beam based on characteristics from which the necessary noise corrections and / or phase modifications may be calculated.

[0460] In accordance with a preferred embodiment of the present invention, the multiple sub-beams along channel 2216 are directed towards beam splitter 2260. Beam splitter 2260 preferably splits each sub-beam into a transmitted portion 2262 and a reflected portion 2264 according to a predetermined ratio. For example, beam splitter 2260 may split each sub-beam with a 99.9% transmittance:0.01% reflectance ratio.

[0461] The transmitted portions 2262 of the sub-beams preferably propagate towards focusing lens 2220, where the sub-beams combine to form output beam 2222 having far-field intensity pattern 2266. The reflected portions 2264 of the sub-beams preferably reflect towards additional focusing lens 2268, where the sub-beams combine to form output reference beam 2270 having far-field intensity pattern 2272 that is incident on the surface of one or more of the plurality of detectors 2250.

[0462] In certain applications, output beam 2222 is preferably directed towards substrate 2280 where far-field intensity pattern 2266 of substrate 2280 is preferably incident. Substrate 2280 may be a workpiece being processed by OPA laser 2202. For example, OPA laser 2202 may operate to additively manufacture, cut, weld, sinter, or otherwise process workpiece 2280. Phase control subsystem 2230 preferably alters the phase of output beam 2222 to focus output beam 2222 at substrate 2280. It will be understood that without the application of such phase alteration by phase control subsystem 2230, output beam 2222 would not be focused at substrate 2280.

[0463] A particular feature of preferred embodiments of the present invention is that focusing lens 2220 is designed such that output beam 2222 of OPA laser 2202, when no phase modification is applied, is not focused by lens 2220 onto the surface of substrate 2280. By way of example, as can be seen from an examination of FIG. 22A , which illustrates the configuration of output beam 2222 with no phase modification applied, focusing lens 2220 may be optically designed to focus unphase-modified collimated wavefront 2282 comprising output beam 2222 to focal point 2284 on the surface of substrate 2280.

[0464] 22B, which shows the configuration of output beam 2222 when a phase change is applied to output beam 2222, the phase change of output beam 2222 preferably serves to modify the shape, and therefore the focus, of wavefront 2282, as seen in the case of representative phase-modified wavefront 2286, which is preferably focused onto substrate 2280 via focusing lens 2220. It will thus be appreciated that the focusing of output beam 2222 on substrate 2280 is achieved not solely by focusing lens 2220, but by its phase change in combination with focusing lens 2220, as shown in FIG.

[0465] As a result of the focusing of output beam 2222 on substrate 2280 being achieved by its phase change, backscattering originating from substrate 2280 is correspondingly not focused by focusing lens 2220 onto OPA laser 2202. As is well known in the art, backscattering from a surface treated by a laser beam typically returns to the laser and can damage the laser, particularly in laser amplification systems. In the present invention, focusing lens 2220 does not focus the backscattering toward OPA laser 2202, and therefore the backscattering does not reach and damage OPA laser 2202, thereby avoiding such damage.

[0466] An exemplary return path of backscatter from substrate 2280 toward OPA laser 2202 is shown in FIG. 23. As seen in FIG. 23, backscattered laser beam 2300 emanating from substrate 2280 preferably reaches focusing lens 2220. However, backscattered laser beam 2300 is preferably not focused by focusing lens 2220 onto OPA laser 2202, thereby preventing damage thereto. It will be appreciated that if focusing lens 2220 were designed to focus unphase-corrected laser output from OPA laser 2202 onto substrate 2280, as is typically the case in conventional laser systems, the path of backscattered beam 2300 would accordingly be focused by focusing lens 2220 onto OPA laser 2202, thus potentially causing damage to focusing lens 2220.

[0467] It will be appreciated that in certain embodiments of the present invention, focusing of the output of OPA laser 2202 onto substrate 2280 can be achieved solely by appropriate phase modification of output beam 2222, such that focusing lens 2220 is not required.

[0468] As described hereinabove with reference to FIGS. 1A-23, output from a seed laser may be directed to an amplifier system for amplification thereof. As is well known to those skilled in the art, imperfections in the laser output from a seed laser powering an amplifier system can result in damage to the amplifier system. Typical imperfections in the laser output from a seed laser that can cause damage to an amplifier system connected to the seed laser include a reduction in the power of the seed laser output and degradation of the laser linewidth. The resulting damage to the amplifier system can occur very rapidly, on the order of a few nanoseconds, before the response time of any internal detection mechanisms that may be included in the amplifier system.

[0469] A preferred embodiment of the present invention for preventing damage to an amplifier system in the event of a fault in a connected seed laser will now be described with reference to Figures 24-33. It will be understood that the seed laser fault protection system described below can be incorporated into any OPA laser of the type described hereinabove with reference to Figures 1A-23, and can be incorporated into any other laser system that includes a seed laser and an amplifier connected thereto.

[0470] 24, there is provided a laser system 2400 that preferably includes a seed laser 2402 that provides a laser output, and an amplification subsystem, here, by way of example, the amplification subsystem is embodied as a power amplifier 2404, which receives the laser output from the seed laser 2402 and amplifies the laser output to provide an amplified laser output 2406. The laser system 2400 may, by way of example, be embodied as a master oscillator power amplifier (MOPA) laser or any other laser system that includes a seed laser and a power amplifier. The laser output from the seed laser 2402 preferably reaches the power amplifier 2404 via a first optical path 2408, here, by way of example, the first optical path 2408 is embodied as including a coiled optical fiber 2410.

[0471] To detect possible defects in the laser output of seed laser 2402, system 2400 preferably further includes a detector subsystem, preferably embodied as seed sensor 2420, that receives output from seed sensor 2402. The laser output from seed laser 2402 preferably reaches detector subsystem 2420 via a second optical path 2422. Detector subsystem 2420 may include one or more sensors for sensing characteristics in the laser output, and more specifically, for detecting possible faults in the laser output. Sensor subsystem 2420 is preferably operably coupled to power amplifier 2404. Sensor subsystem 2420 is preferably configured to deactivate power amplifier 2404 upon detecting a fault in the laser output from seed laser 2402.

[0472] A particular feature of preferred embodiments of the present invention is that the first time of flight (TOF=T1) of the laser output along the first optical path 2408 from the seed laser 2402 to the power amplifier 2404 is greater than the combination of the second time of flight (TOF=T2) of the laser output along the second optical path 2422 from the seed laser 2402 to the sensor subsystem 2420 and the time it takes for the sensor subsystem 2420 to deactivate the power amplifier 2404.

[0473] As a result of the relatively long time of flight of the laser output from the seed laser 2402 to the power amplifier 2404, the sensor subsystem 2420 detects a fault in the received laser output and deactivates the power amplifier 2404 before the power amplifier 2404 receives the defective laser output, thereby preventing damage to the power amplifier 2404.

[0474] Extending the time-of-flight of the laser output from the seed laser 2402 to the power amplifier 2404 is achieved in the embodiment of the invention shown in FIG. 24 by including a fiber coil 2410 along the first optical path to allow time for the sensor 2420 to detect a fault in the laser output and deactivate the power amplifier 2404, if necessary, before the faulty laser output is received by the power amplifier 2404. By way of example, the fiber coil 2410 may have a physical length of 10 km, and the time-of-flight of the laser output along it may be approximately 50 microseconds. Thus, if a fault occurs in the output from the seed laser 2402, the power amplifier 2404 continues to receive a fault-free input signal for 50 microseconds after the onset of the faulty output signal from the seed laser 2402.

[0475] The optical path between the seed laser 2402 and the sensor subsystem 2420 does not include the coil 2410 and can be direct and therefore much shorter. Therefore, the time-of-flight of the laser output from the seed laser 2402 to the sensor subsystem 2420 is preferably much shorter than 50 microseconds, for example, on the order of 30 microseconds or less. Therefore, after a fault occurs in the output from the seed laser 2402, the sensor subsystem 2420 can quickly receive the laser output, detect the fault therein, and turn off the power amplifier 2404 before the time delay between the seed laser 2402 and the power amplifier 2404 expires. As a result, the power amplifier 2404 is preferably switched off by the sensor subsystem 2420 before the power amplifier 2404 receives the fault signal detected by the sensor subsystem 2420, thereby preventing damage to the power amplifier 2404.

[0476] It will be understood that the lengthening of the optical path between the seed laser 2402 and the power amplifier 2404, and therefore the increase in the time of flight there along, compared to the time and length of the optical path between the seed laser 2402 and the sensor subsystem 2420, is not limited to being achieved by the inclusion of a fiber coil along the optical path between the seed laser 2402 and the power amplifier 2404. Rather, the optical path between the seed laser 2402 and the power amplifier 2404 may be lengthened by any suitable means, including, for example, the inclusion of an optical delay line 2500 there along, as shown in FIG. 25. Furthermore, as shown in FIG. 26, the optical path between the seed laser 2402 and the power amplifier 2404 may be a free-space optical path 2600, in which case the time of flight there along may be lengthened by the use of optical elements such as reflective mirrors. However, it will be understood that the inclusion of the coiled fiber 2410 in the first optical path 2408 may be particularly advantageous due to its compact configuration and due to the preservation of the optical mode of the seed laser output by the coiled fiber 2410.

[0477] It will be understood that the particular configuration of coiled fiber 2410 shown in Figure 24 is merely representative and illustrative. Coiled fiber 2410 may be embodied in any suitable form and may be adapted to move the laser output in one direction or back and forth along the optical path to further increase the effective length of the optical path provided by coiled fiber 2410.

[0478] Reference is now made to FIG. 27, which is a simplified schematic diagram of a laser amplifier system including a seed laser failure protection system, constructed and operative in accordance with yet another preferred embodiment of the present invention.

[0479] 27, a laser system 2700 is provided that preferably includes a seed laser 2702 that provides a laser output. The seed laser 2702 is preferably connected to a first amplifier 2703, which is preferably connected to a second amplifier 2704, here embodied, by way of example, as a power amplifier 2704, to provide an amplified laser output 2706. The laser system 2700 may, by way of example, be embodied as a master oscillator power amplifier (MOPA) laser, or may be any other laser system that includes a seed laser and a power amplifier.

[0480] As is well known to those skilled in the art, and as described in detail herein above, imperfections in the laser output by the seed laser 2702 can result in damage to the power amplifier 2704. Typical imperfections in the laser output by the seed laser 2702 that cause damage to the power amplifier 2704 can include an cessation or reduction in the power of the seed laser output and degradation of the laser linewidth. Such damage to the power amplifier can occur very rapidly, on the order of a few nanoseconds, before the response time of internal detection mechanisms that may be included in the power amplifier 2704.

[0481] It is a particular feature of preferred embodiments of the present invention that laser system 2700 includes an additional amplifier 2703 to prevent damage to power amplifier 2704 as a result of imperfections in the output of seed laser 2702. Preferably, additional amplifier 2703 provides much lower amplification than that provided by power amplifier 2704, and is included in system 2700 for the purpose of preventing damage to power amplifier 2704 upon degradation of laser output from seed laser 2702, rather than for the purpose of amplifying the laser output from seed laser 2702 itself.

[0482] In operation of system 2700, laser output from seed laser 2702 is preferably received by first amplifier 2703. First amplifier 2703 preferably provides a first amplified laser output, which is preferably received and amplified by second amplifier 2704.

[0483] When the laser output of seed laser 2702 is stopped, due to a malfunction of seed laser 2702, first amplifier 2703 no longer receives laser output from seed laser 2702. In this case, first amplifier 2703 generates amplified spontaneous emission, which is received by second amplifier 2704. Alternatively, first amplifier 2703 may be configured such that when the laser output from seed laser 2702 is stopped, first amplifier 2703 begins operating as a laser and generates additional laser output.

[0484] It is understood, therefore, that even if seed laser 2702 stops providing laser output, second amplifier 2704 continues to receive an input signal in the form of amplified spontaneous emission or additional laser output from first amplifier 2703. The amplified spontaneous emission provided to second amplifier 2704 by first amplifier 2703 is sufficient to prevent damage to second amplifier 2704 that could otherwise occur due to cessation of providing a signal to second amplifier 2704. It is understood that system 2700 may additionally include a sensor coupled to seed laser 2702 to detect a failure in the laser output from seed laser 2702 and deactivate second amplifier 2704 accordingly.

[0485] It is understood that during proper operation of the seed laser 2702, the first amplification provided by the first amplifier 2703 is preferably negligible compared to the second primary amplification provided by the second amplifier 2704.

[0486] As seen in Figure 27, the laser output from the seed laser 2702 may be fed directly to the first amplifier 2703. Alternatively, as shown in Figure 28, additional elements can be inserted to interface the seed laser 2702 and the first amplifier 2703. In particular, a filter can be inserted between the seed laser 2702 and the first amplifier 2703 to filter out laser beams with unacceptably narrow linewidths to prevent such laser beams from reaching and damaging the second amplifier 2704.

[0487] A particularly preferred embodiment of a linewidth filter 2800 suitable for use in the present invention is shown in FIG.

[0488] 28, filter structure 2800 is seen to be implemented downstream of seed laser 2702 and upstream of first amplifier 2703. The laser output from seed laser 2702 is preferably split into two portions by splitter 2805 at the entrance to filter 2800 and recombined by recombiner 2806 before exiting filter 2800. A first portion of the split laser output from seed laser 2702 preferably travels along a first arm 2807 of filter 2800 between splitter 2805 and recombiner 2806. A second portion of the split laser output from seed laser 2702 preferably travels along a second arm 2808 of filter 2800 between splitter 2805 and recombiner 2806. As can be seen from a comparison of the first and second arms 2807 and 2808, the first arm 2807 preferably includes an additional portion 2809 compared to the second arm 2808 and is therefore longer than the second arm 2808.

[0489] If the laser output from seed laser 2702 has an unacceptably narrow linewidth, the laser outputs from first and second arms 2807 and 2808 will interfere with each other due to their relatively high coherence when recombined at recombiner 2806. The recombined beam is preferably detected by detector 2810, which is preferably connected to electronic control module 2811. Electronic control module 2811 is preferably a coherent beam combining (CBC) card in controlling the operation of phase modulator 2812 positioned along second arm 2808. Phase modulator 2812 is preferably operated by electronic control card 2811 to change the phase of the beam along second arm 2808 so that substantially all of the recombined beam at recombiner 2806 is directed towards detector 2810. Thus, the recombined beam does not travel towards the first amplifier 2703 and therefore does not reach and cause damage to the second amplifier 2704. Reception of laser output from the seed laser 2702 by the first amplifier 2703 is thereby stopped and the first amplifier 2703 generates one of amplified spontaneous emission or additional laser output as described in detail herein above.

[0490] If seed laser 2702 is operating properly and the laser output from seed laser 2702 has an acceptably wide linewidth, the laser outputs from first and second arms 2807 and 2808 will not interfere with each other when recombined at recombiner 2806. This is because the coherence is relatively low and therefore the linewidth is wide enough that little or no mutual interference occurs. In this case, a portion of the laser output at recombiner 2806 travels towards first amplifier 2703, and a portion of the laser output at recombiner 2806 is delivered to detector 2810. As outlined above with reference to system 2700, the laser output received by first amplifier 2703 is preferably subsequently provided by first amplifier 2703 to second amplifier 2704.

[0491] It will be appreciated that the damage protection system shown in Figures 27 and 28, including the additional amplifier 2703 and filter structure 2800, may be used alone or in combination with any one of the protection systems shown in Figures 24-26.

[0492] Reference is now made to FIG. 29, which is a simplified schematic diagram of a laser amplifier system including a seed laser failure protection system, constructed and operative in accordance with a still further preferred embodiment of the present invention.

[0493] 29, a laser system 2900 is preferably provided that includes a seed laser 2902 that provides a first laser output 2903, and an amplification subsystem, here by way of example embodied as a power amplifier 2904, that receives the first laser output 2903 from the seed laser 2902 and amplifies the laser output to provide an amplified laser output 2906. Laser system 2900 may, by way of example, be embodied as a master oscillator power amplifier (MOPA) laser, or may be any other laser system that includes a seed laser and a power amplifier.

[0494] To detect possible defects in the laser output of seed laser 2902, system 2900 preferably further includes a detector subsystem, preferably embodied as a seed sensor 2920, that receives output from seed laser 2902. Sensor subsystem 2920 may include one or more sensors for sensing characteristics in the laser output, and more specifically, for detecting possible faults in the laser output. Sensor subsystem 2920 is preferably operably coupled to power amplifier 2904. Sensor subsystem 2920 is preferably configured to deactivate power amplifier 2904 upon detecting a fault in the laser output from seed laser 2902.

[0495] A particular feature of preferred embodiments of the present invention is that laser system 2900 preferably includes an auxiliary laser subsystem, preferably embodied as an auxiliary seed laser 2930. Auxiliary seed laser 2930 preferably provides a second laser output 2932 to amplifier 2904, with second laser output 2932 preferably having a power significantly lower than the power of first laser output 2903. By way of example only, first laser output 2903 may have a first power in the range of 80-100 milliwatts, while second laser output 2932 may have a second power in the range of 50-70 milliwatts.

[0496] Auxiliary seed laser 2930 preferably provides second laser output 2932 at least when seed laser 2902 is shut off, and provides first laser output 2903 to amplifier 2904. Particularly preferably, auxiliary seed laser 2930 operates continuously to provide second laser output 2932 to amplifier 2904, preferably at the same time as seed laser 2902 provides first laser output 2903 to amplifier 2904, and also at the same time as seed laser 2902 stops providing first laser output 2903.

[0497] During proper operation of seed laser 2902, amplifier 2904 preferably receives both first laser output 2903 from seed laser 2902 and second laser output 2932 from auxiliary seed laser 2930. Because the power of second laser output 2932 is significantly lower than the power of first laser output 2903, the contribution of second laser output 2903 to amplified laser output 2906 is preferably negligible. Preferably, but not necessarily, second laser output 2932 has a different wavelength than first laser output 2903 to further reduce the impact of second laser output 2932 on amplified laser output 2906. By way of example only, first laser output 2903 may have a first wavelength in the range of 1060-1070 nm, while second laser output 2932 may have a second wavelength in the range of 1070-1080 nm.

[0498] When laser output from seed laser 2902 ceases, due to a malfunction of seed laser 2902 detected by sensor subsystem 2920, sensor subsystem 2920 preferably operates to deactivate amplifier 2904. Due to the finite response time of amplifier 2904 and detector subsystem 2920, amplifier 2904 is not instantaneously deactivated, but rather continues to operate for a limited period of time after cessation of laser output from seed laser 2902. It will be appreciated that during this time, amplifier 2904 no longer receives first laser output 2903 from seed laser 2902. However, auxiliary seed laser 2930 preferably continues to provide second laser output 2932 to amplifier 2904. Thus, it will be appreciated that amplifier 2904 continues to receive an input signal in the form of second laser output 2932, even when seed laser 2902 ceases to provide laser output. The second laser output 2932 provided to the amplifier 2904 by the auxiliary seed laser 2930 is sufficient to prevent damage to the amplifier 2904, which would likely occur due to the cessation of signal supply, before the amplifier 2904 is deactivated by the sensor 2920.

[0499] Reference is now made to FIG. 30, which is a simplified schematic diagram of a laser amplifier system including a seed laser failure protection system, constructed and operative in accordance with an even more preferred embodiment of the present invention.

[0500] 30, a laser system 3000 is preferably provided that includes a seed laser 3002 that provides a first laser output 3003, and an amplification subsystem, here embodied by way of example as a power amplifier 3004, that receives the first laser output 3003 from the seed laser 3002 and amplifies the laser output to provide an amplified laser output 3006. Laser system 3000 may be embodied by way of example as a master oscillator power amplifier (MOPA) laser, or may be any other laser system that includes a seed laser and a power amplifier.

[0501] To detect possible defects in the laser output of the seed laser 3002, the system 3000 preferably further includes a detector subsystem 3020 that receives the output from the seed laser 3002. The detector subsystem 3020 may include one or more sensors for sensing characteristics in the laser output, and more specifically, for detecting possible faults in the laser output. The sensor subsystem 3020 is preferably operably coupled to the power amplifier 3004. The sensor subsystem 3020 is preferably configured to deactivate the power amplifier 3004 upon detecting a fault in the laser output from the seed laser 3002.

[0502] A particular feature of preferred embodiments of the present invention is that laser system 3000 preferably includes a pair of gratings 3030. The pair of gratings 3030 preferably includes a first reflective grating 3032 positioned at the entrance 3034 of amplifier 3004 and a second reflective grating 3036 preferably positioned at the exit 3038 of amplifier 3004. The pair of gratings 3030 in combination with amplifier 3004 preferably form a preferred embodiment of auxiliary laser subsystem 3040.

[0503] During proper operation of seed laser 3002 , amplifier 3004 preferably receives first laser output 3003 from seed laser 3002 and amplifies first laser output 3003 to provide amplified laser output 3006 .

[0504] When the laser output from seed laser 3002 ceases, due to a malfunction of seed laser 3002 detected by sensor subsystem 3020, sensor subsystem 3020 preferably operates to deactivate amplifier 3004. Due to the finite response time of amplifier 3004 and sensor subsystem 3020, amplifier 3004 is not instantaneously deactivated, but rather typically continues to operate for a limited period of time after cessation of laser output from seed laser 3002. It is understood that during this time, amplifier 3004 no longer receives laser output from seed laser 3002. In this case, reflective grating 3030 preferably provides signal feedback to amplifier 3004, such that amplifier 3004, in combination with paired gratings 3030, preferably begins to operate as a laser. Refractory grating 3030 preferably has a relatively low reflectivity such that the signal feedback provided by reflective grating 3030 has a lower power than the power of laser output 3003 of seed laser 3002.

[0505] Particularly preferably, but not necessarily, the pair of gratings 3030 are reflective at a wavelength different from the wavelength of the first laser output 3003 of the seed laser 3002, such that during proper operation of the seed laser 3002, the grating 3030 has a negligible effect on the amplified output 3006. By way of example only, the first laser output 3003 may have a wavelength in the range of 1060-1070 nm, while the grating 3030 may be reflective at wavelengths in the range of 1090-1100 nm.

[0506] It will thus be appreciated that even when seed laser 3002 ceases to provide laser output, amplifier 3004 continues to receive an input signal in the form of signal feedback from grating 3030. As a result, amplifier 3004 in combination with grating 3030 begins to operate as a laser upon cessation of operation of seed laser 3002, thereby preventing damage to amplifier 3004 that might otherwise occur due to cessation of the provision of a signal to the amplifier.

[0507] As seen in Figures 29 and 30, the laser output from the seed lasers 2902, 3002 may be fed directly to the amplifiers 2904, 3004, respectively. Alternatively, additional elements can be inserted to interface the seed lasers with the amplifiers, as shown in Figures 31 and 32. In particular, a linewidth filter, such as filter 2800 or any other suitable filter, may be inserted between the seed lasers 2902, 3002 and the amplifiers 2904, 3004, respectively, to filter laser beams with unacceptably narrow linewidths and prevent such laser beams from reaching and thus damaging the amplifiers 2904, 3004.

[0508] As detailed hereinabove, each of the laser systems described with reference to Figures 24-32 can include a detector subsystem, such as detector subsystems 2420, 2920, and 3020. The detector subsystem is preferably embodied as at least one sensor for sensing output from a seed laser. A particularly preferred embodiment of a sensor forming part of a detector subsystem, such as detector subsystems 2420, 2920, and 3020, is shown in Figure 33. However, it will be understood that the sensor shown in Figure 33 is not limited to use in systems of the type described herein, but may be incorporated as a laser output sensor in any laser system that would benefit from its use.

[0509] As seen in FIG. 33, a detector subsystem 3320 is provided. Laser output from a seed laser preferably enters the sensor subsystem 3320 at an input point 3330 and proceeds towards a splitter 3334. At the splitter 3334, a small portion, such as 1%, of the laser power is directed towards a detector 3336, and the remaining portion of the laser power proceeds towards a sensor amplifier 3340. The sensor amplifier 3340 is preferably a lower power amplifier than the power amplifiers 2404, 2704, 2904, or 3004. The sensor amplifier 3340 preferably outputs an amplified laser output that is preferably delivered to an additional detector 3342 via an elongated optical fiber 3344.

[0510] In operation of detector subsystem 3320, if the output from the seed laser is stopped, the intensity of the amplified laser output detected by additional detector 3342 will decrease. In this case, a control module (not shown) connected to additional detector 3342 and a power amplifier, such as power amplifier 2404, 2704, 2904, or 3004, can deactivate the power amplifier to prevent damage to the power amplifier.

[0511] If the output from the seed laser degrades to an unacceptably narrow linewidth, nonlinear effects will be initiated in fiber 3344. It will be appreciated that fiber 3344 is advantageously configured to be as sensitive as possible to such nonlinear effects. To this end, to increase the sensitivity of fiber 3344 to the linewidth of the laser output from the seed laser, fiber 3344 is preferably of considerable length and preferably has a small core diameter. By way of example only, fiber 3344 may have a length of about 25 m and a core diameter of about 6 microns.

[0512] As the linewidth of the output from the seed laser is narrowed, due to nonlinear effects initiated in fiber 3344, fiber 3344 begins to act as a mirror, reflecting light back towards amplifier 3340. As the reflected light returns to amplifier 3340, an increased signal reaches splitter 3334 and is detected by detector 3336. Once an increased signal is detected at detector 3336, the power amplifier is preferably deactivated to prevent damage to the power amplifier.

[0513] Those skilled in the art will appreciate that the present invention is not limited by what is specifically claimed below. Rather, the scope of the present invention includes various combinations and subcombinations of the features described hereinabove, and modifications and variations thereof, which would occur to one skilled in the art upon reading the foregoing description in conjunction with the drawings, and which are not present in the prior art.

Claims

1. 1. A laser system comprising: a seed laser; a laser beam splitting and combining subsystem that receives outputs from the seed lasers and provides a combined laser output, the laser beam splitting and combining subsystem modifying the phase of the combined laser output; a plurality of detectors that detect the combined laser output at discrete times during the changing of the phase of the combined laser output; a plurality of optical paths between the combined laser output and the plurality of detectors, the plurality of optical paths being for providing the combined laser output to the plurality of detectors along the plurality of optical paths, the spatial density of the plurality of optical paths being greater than the spatial density of the plurality of detectors; A laser system comprising:

2. 10. The laser system of claim 1, wherein the combined laser output has noise, and wherein the laser system also includes a noise cancellation subsystem operative to provide a noise-canceled phase-corrected output based on accounting for the noise in the combined laser output detected by the plurality of detectors at the intermittent times during the changing of the phase of the combined laser output.

3. 3. The laser system of claim 1, wherein the laser beam splitting and combining subsystem changes the phase of the combined laser output during time intervals between the intermittent times.

4. 3. The laser system of claim 1, wherein the combined laser output has noise, and the laser beam splitting and combining subsystem changes the phase of the combined laser output at a rate that exceeds a rate that accounts for the noise of the combined laser output, the noise being detected by the plurality of detectors at the intermittent times.

5. 5. The laser system of claim 1, wherein the plurality of optical paths include a plurality of optical fibers, and the ends of the optical fibers are arranged at a spatial density greater than the spatial density of the plurality of detectors.

6. 6. The laser system of claim 11, wherein some of the optical paths are spaced apart by a distance of 20 to 1000 microns.

7. 7. The laser system of claim 6, wherein some of the plurality of detectors are spaced apart by a distance of 5 to 50 mm.

8. 1. A method for detecting laser output, comprising: receiving output from a seed laser; splitting and combining the outputs to provide a combined laser output; changing the phase of the combined laser output; providing the combined laser output along a plurality of optical paths to a plurality of detectors, wherein a spatial density of the plurality of optical paths is greater than a spatial density of the plurality of detectors.

9. 9. The method of claim 8, wherein the combined laser output has noise, the method comprising providing a noise-canceled phase-corrected output based on accounting for the noise in the combined laser output detected by the plurality of detectors at discrete times during the changing of the phase of the combined laser output.

10. The method of claim 9 , wherein the phase changes are performed during time intervals between the intermittent times.

11. 11. The method of claim 9 or 10, wherein the phase of the combined laser output is changed at a phase change rate that exceeds a rate that accounts for the noise of the combined laser output at which the noise is detected by the plurality of detectors during the intermittent times.

12. 12. The method of claim 8, wherein the plurality of optical paths comprises a plurality of optical fibers, the ends of the optical fibers being arranged at a spatial density greater than a spatial density of the plurality of detectors.

13. A method according to any one of claims 8 to 12, wherein the optical paths are spaced apart by a distance of between 20 and 1000 microns.

14. The method of claim 12, wherein the plurality of detectors are spaced apart by a distance of 5 to 50 nm.

15. 10. The laser system of claim 1, the laser beam splitting and combining subsystem splits the output from the seed laser into a plurality of sub-beams and provides a combined laser output comprising the plurality of sub-beams; the laser system including a phase modulation subsystem that groups at least a portion of the sub-beams of the plurality of sub-beams into multiple sub-beam groups; the phase modulation subsystem: Varying the phase of each sub-beam in each group relative to the phases of other sub-beams in the group in parallel across the multiple sub-beams to vary the phase of each group; and Varying the phase of each group relative to other groups of the multiple groups of sub-beams, thereby varying the phase of the combined laser output. Laser system.

16. the phase modulation subsystem includes a number of detectors corresponding to the number of groups for detecting the far-field intensity pattern of each of the number of groups; 16. The laser system of claim 15.

17. 17. The laser system of claim 16, wherein each of said multiple detectors comprises said plurality of detectors.

18. 18. The laser system of claim 17, wherein a plurality of optical paths are provided between the far field intensity pattern of each of the multiple groups and a respective plurality of detectors for providing the far field intensity pattern along the plurality of optical paths to the plurality of detectors, and wherein the spatial density of the plurality of optical paths is greater than the spatial density of the plurality of detectors.

19. 10. The laser system of claim 1, wherein the alteration of the phase of the combined laser output provides a spatial modulation of the combined laser output.

20. 20. The laser system of claim 19, wherein the spatial modulation by the change of the phase is provided in combination with mechanical spatial modulation, and the spatial modulation combined with the mechanical spatial modulation is faster than the mechanical spatial modulation in the absence of the spatial modulation by the change of the phase.

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