Dynamic Beam Shaping of an Optical Phased Array 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 The Israeli Patent Application No. 255496 entitled "OPTICAL PHASED ARRAY DYNAMIC BEAM SHAPING WITH NOISE CORRECTION" filed on November 7, 2017, the Israeli Patent Application No. 256107 entitled "SEED LASER FAILURE PROTECTION SYSTEM" filed on December 4, 2017, the US Provisional Patent Application No. 62 / 594,167 entitled "LASER BACK - REFLECTION PROTECTION USING OPTICAL PHASED ARRAY LASER" filed on December 4, 2017, the Israeli Patent Application No. 258936 entitled "SCALED PHASE MODIFICATION, PHASE CALIBRATION AND SEED LASER PROTECTION IN OPTICAL PHASED ARRAY" filed on April 25, 2018, the US Provisional Patent Application No. 62 / 684,341 entitled "MULTIPLE DETECTORS AND CORRESPONDING MULTIPLE CLOSELY SPACED OPTICAL PATHWAYS IN OPTICAL PHASED ARRAY LASER" filed on June 13, 2018, and the US Provisional Patent Application No. 62 / 702,957 entitled "DETECTOR MASK IN OPTICAL PHASED ARRAY LASER" filed on July 28, 2018 are hereby incorporated by reference in their entirety, and all of their disclosures are incorporated herein by reference, and all of their priorities are claimed herein in accordance with 37 CFR 1.78(a)(4) and (5)(i).

[0002] U.S. Patent No. 9,893,494 is also incorporated by reference, and its disclosure is incorporated herein by reference.

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

[0004] In the art, various types of optical phased arrays are known. **Summary of the Invention**

[0005] It is an object of the present invention to provide a system and method for noise correction and phase correction in a dynamically shaped beam generated by a laser optical phased array.

[0006] Accordingly, according to 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 the output from the seed laser and provides a combined laser output having noise, and a noise cancellation subsystem that operates to provide a noise cancellation phase correction output based on considering noise at intermittent times, wherein the laser beam splitting and combining subsystem changes the phase of the combined laser output during a time interval during intermittent times.

[0007] According to another 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 the output from the seed laser and provides a combined laser output having noise, and a noise cancellation subsystem that operates to provide a noise cancellation phase correction output based on considering noise at a noise sampling rate, wherein the laser beam splitting and combining subsystem changes the phase of the combined laser output at a phase change rate exceeding the sampling rate.

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

[0009] Preferably, the noise sampling rate is pre-determined.

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

[0011] Preferably, the spatial modulation of the combined laser output is provided in combination with the mechanical spatial modulation of the combined laser output, and the spatial modulation combined with the mechanical spatial modulation is faster than the mechanical spatial modulation without spatial modulation.

[0012] Additionally or alternatively, the spatial modulation of the combined laser output is provided in combination with the mechanical spatial modulation of the combined laser output, and the spatial modulation combined with the mechanical spatial modulation is more accurate than the mechanical spatial modulation without 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 splitting and upstream of combining.

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

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

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

[0018] According to an additionally preferred embodiment of the present invention, the noise cancellation phase correction output cancels intensity noise in the combined laser output.

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

[0020] According to still another additionally preferred embodiment of the present invention, the noise cancellation phase correction output cancels position noise in the combined laser output.

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

[0022] Preferably, the laser cutting system includes 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] Still additionally or alternatively, the laser welding system includes the laser system of the present invention.

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

[0026] According to another preferred embodiment of the present invention, there is provided a method for performing noise correction on a laser output with a changed phase, including receiving an output from a seed laser, splitting and combining the output to provide a combined laser output having noise, applying a noise cancellation phase correction output to the combined laser output based on taking into account noise at intermittent times, and changing the phase of the combined laser output during a time interval between intermittent times.

[0027] According to another preferred embodiment of the present invention, there is provided a method for performing noise correction on a laser output with a changed phase, comprising receiving an output from a seed laser, splitting and combining the output to provide a combined laser output with noise, applying a noise cancellation phase correction output to the combined laser output based on taking into account the noise at a noise sampling rate, and changing the phase of the combined laser output at a phase change rate exceeding the noise sampling rate.

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

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

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

[0031] Preferably, the spatial modulation of the combined laser output is provided in combination with a mechanical spatial modulation of the combined laser output, and the spatial modulation combined with the mechanical spatial modulation is faster than the mechanical spatial modulation without spatial modulation.

[0032] Additionally or alternatively, the spatial modulation of the combined laser output is provided in combination with a mechanical spatial modulation of the combined laser output, and the spatial modulation combined with the mechanical spatial modulation is more accurate than the mechanical spatial modulation without 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] According to another preferred embodiment of the present invention, the method also includes calculating a noise cancellation phase correction output based on continuously applying at least two phase changes to at least one component beam of the combined laser output and identifying one of the at least two phase changes corresponding to the maximum output intensity of the at least one component beam.

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

[0037] Preferably, the detection is performed continuously.

[0038] According to still another preferred embodiment of the present invention, the noise cancellation phase correction 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] According to yet another preferred embodiment of the present invention, the noise cancellation phase correction output cancels position noise in the combined laser output.

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

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

[0043] Additionally or alternatively, the method for additive manufacturing includes the method of the present invention.

[0044] Still additionally or alternatively, the method for laser welding includes the method of the present invention.

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

[0046] According to another preferred embodiment of the present invention, there is provided a laser system, comprising a seed laser, and a laser beam splitting and combining subsystem that receives the output from the seed laser and provides a combined laser output, wherein the laser beam splitting and combining subsystem changes the phase of the combined laser output, a plurality of detectors that detect the combined laser output at intermittent times during the change of the phase of the combined laser output, and a plurality of optical paths between the combined laser output and the plurality of detectors, wherein the plurality of optical paths are for providing the combined laser output along the plurality of optical paths to the plurality of detectors, and the spatial density of the plurality of optical paths is greater than the spatial density of the plurality of detectors.

[0047] Preferably, the combined laser output has noise, and the laser system further includes a noise cancellation subsystem that operates to provide a noise cancellation phase correction output based on taking into account the noise of the combined laser output detected by the plurality of detectors at intermittent times during the change of the phase of the combined laser output.

[0048] Preferably, 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.

[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] According to another preferred embodiment of the present invention, there is provided a method for detecting a laser output, comprising receiving an output from a seed laser, splitting and combining the output to provide a combined laser output, changing a phase of the combined laser output, and providing the combined laser output to a plurality of detectors along a plurality of optical paths, wherein a spatial density of the plurality of optical paths is greater than a spatial density of the plurality of detectors.

[0052] Preferably, the combined laser output has noise, and the method further includes providing a noise cancellation phase correction output based on taking into account the noise of the combined laser output detected by the plurality of detectors during the change of the phase of the combined laser output.

[0053] Preferably, the plurality of optical paths include a plurality of optical fibers, and ends of the optical fibers are arranged with a spatial density greater than a 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, detectors among the plurality of detectors are spaced apart by a distance of 5 to 50 mm.

[0056] According to still another preferred embodiment of the present invention, there is provided a laser system comprising a seed laser, a laser beam splitting and combining subsystem that receives the output from the seed laser and provides a combined laser output, wherein the laser beam splitting and combining subsystem changes the phase of the combined laser output, at least one detector that detects the combined laser output during the change of the phase of the combined laser output, and an optical mask that includes at least one of a transmission region and a reflection region and is configured to provide the combined laser output to the at least one detector through and from at least one of the transmission region and the reflection region.

[0057] Preferably, at least one of the transmission region and the reflection region is configured according to at least one of the shape and the trajectory of the combined laser output.

[0058] Preferably, the system further includes a focusing subsystem that interfaces the optical mask and the at least one detector to focus 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 includes a single detector.

[0061] According to a preferred embodiment of the present invention, the transmission region has a non-uniform transparency.

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

[0063] Preferably, the optical mask includes an electrically modulated device, and at least one of the transmission region and the reflection region is electronically modifiable.

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

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

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

[0067] Preferably, the reflection region includes a DMM.

[0068] Preferably, the combined laser output has noise, and the laser system operates based on taking into account the noise of the combined laser output detected by at least one detector during the change of the phase of the combined laser output, and also includes a noise cancellation subsystem that provides a noise cancellation phase correction output.

[0069] According to still a more preferred embodiment of the present invention, a method for detecting a laser output, comprising receiving an output from a seed laser, splitting and combining the output to provide a combined laser output, changing the phase of the combined laser output, and providing the combined laser output to at least one detector by an optical mask, wherein the optical mask includes at least one of a transmission region and a reflection region, and is for providing the combined laser output to at least one detector respectively through and from at least one of the transmission region and the reflection region, and further comprising detecting the combined laser output during the change of the phase by at least one detector, is further provided.

[0070] Preferably, at least one of the transmission region and the reflection region is configured according to at least one of the shape and trajectory of the combined 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 that interfaces an optical mask and at least one detector to perform the focusing.

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

[0074] According to a preferred embodiment of the present invention, the transmission region has non-uniform transparency.

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

[0076] Preferably, the optical mask includes an electrically modulated device, and at least one of the transmission region and the reflection region is electronically modifiable.

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

[0078] According to another preferred embodiment of the present invention, the reflection region has non-uniform reflectivity.

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

[0080] Preferably, the reflection region includes a DMM.

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

[0082] According to yet another preferred embodiment of the present invention, there is provided a laser system including a seed laser, a laser splitting and combining subsystem that receives the output from the seed laser and combines the outputs to provide a combined laser output, a phase modulation subsystem for changing the phase of the combined laser output, a voltage applied to the phase modulation subsystem, and a voltage-phase correlation subsystem for correlating the voltage applied to the phase modulation subsystem with the phase modulation output generated by the phase modulation subsystem and providing a voltage-phase correlation output useful for calibrating the phase modulation subsystem, wherein the correlation is performed periodically during the change of the phase.

[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 voltage includes a voltage intended to generate a phase shift of 2π of the combined laser output.

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

[0087] Preferably, the voltage is continuously applied to the phase modulator among the plurality of phase modulators.

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

[0089] Preferably, the change in the phase is performed at a rate of one million times per second, and the correlation is performed at a rate of once per second.

[0090] According to an additionally preferred embodiment of the present invention, a method for performing phase calibration of a laser system, comprising receiving an output from a seed laser, splitting and combining the output to provide a combined laser output, changing the phase of the combined laser output by a phase modulation subsystem, periodically applying a voltage to the phase modulation subsystem during the phase change, and correlating the voltage with the phase modulation output generated by the phase modulation subsystem to provide a voltage-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 voltage includes a voltage intended to generate a phase shift of 2π of the combined laser output.

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

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

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

[0097] Preferably, the phase change is performed at a rate of one million times per second, and the correlation is performed at a rate of once per second.

[0098] According to another preferred embodiment of the present invention, there is provided a laser system, comprising: a seed laser; a laser beam splitting and combining subsystem that receives the 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 sub-beams among the plurality of sub-beams into a group of a plurality of sub-beams, wherein the phase modulation subsystem changes the phase of each sub-beam within each group relative to the phase of other sub-beams within the group and changes the phase of each group relative to the phase of other groups of the plurality of groups in parallel across the group of a plurality of sub-beams to change 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 for performing the grouping.

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

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

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

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

[0105] Preferably, the number of detectors at least partially perform detections simultaneously with each other.

[0106] Preferably, the phase modulation subsystem includes additional auxiliary detectors for detecting a number of combined far-field intensity patterns.

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

[0108] Preferably, the phase modulation subsystem includes an additional electronic control module for controlling the operation of the number of additional phase modulators.

[0109] According to another preferred embodiment of the present invention, each detector of the number of detectors includes a plurality of detectors.

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

[0111] Preferably, changing the phase of the combined laser output includes maximizing the intensity of the combined laser output.

[0112] Preferably, the change in the phase of the combined laser output provides a spatial modulation of the combined laser output without involving a mechanical spatial modulation of the combined laser output.

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

[0114] According to yet another preferred embodiment of the present invention, a method for implementing a phase change of a laser output, comprising receiving a 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 among the plurality of sub-beams into a group of a plurality of sub-beams, and for changing the phase of each group, in parallel across the group of a plurality of sub-beams, changing the phase of each sub-beam within each group relative to the phase of the other sub-beams within the group, and changing the phase of each group relative to the phase of the other groups of the plurality of groups, thereby changing the phase of the combined laser output, is further provided.

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

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

[0117] Preferably, the change in the phase of the sub-beams is implemented 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 plurality of groups by a corresponding plurality of detectors.

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

[0121] Preferably, the detections are performed at least partially simultaneously with respect to each other for a plurality of groups.

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

[0123] Preferably, a change in the phase of each group with respect to the phase of other groups of a plurality of groups of phases is performed by a plurality of additional phase modulators, each additional phase modulator being common to all sub-beams within each group.

[0124] Preferably, the method also includes controlling a plurality of additional phase modulators by an additional electronic control module.

[0125] According to another preferred embodiment of the present invention, each detector of a plurality of detectors includes a plurality of detectors.

[0126] Preferably, the method also includes providing the far-field intensity pattern of each of a plurality of groups to each of the 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, changing the phase of the combined laser output includes maximizing the intensity of the combined laser output.

[0128] Preferably, changing 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, this method also includes amplifying the laser output downstream of the splitting and upstream of the combining.

[0130] According to another preferred embodiment of the present invention, there is provided a laser system including an optical phased array laser, the optical phased array laser including a seed laser and a laser beam splitting and combining subsystem that receives the output from the seed laser and provides a combined laser output, the laser beam splitting and combining subsystem changing the phase of the combined laser output to focus the combined laser output on a substrate, and the combined laser output not being focused on the substrate in the absence of the phase change.

[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 at a focus that does not coincide with the substrate.

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

[0133] According to still another preferred embodiment of the present invention, there is provided a method for focusing a laser beam in a laser system, the method including receiving the laser output from a seed laser, splitting and combining the laser output to provide a combined laser output, and changing the phase of the combined laser output to focus the combined laser output on a substrate, the combined laser output not being focused on the substrate in the absence of the phase change.

[0134] Preferably, the method also includes focusing the combined laser output at a focus that does not coincide with the substrate by an optical element.

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

[0136] According to an additionally preferred embodiment of the present invention, there is provided a laser amplifier system including a seed laser that provides a laser output, an amplification subsystem that receives the laser output from the seed laser along a first optical path and provides an amplified laser output, and a detector subsystem that receives the laser output from the seed laser along a second optical path and operates to deactivate the amplification subsystem when at least one fault in the laser output is detected by the detector subsystem, wherein a first flight time of the laser output from the seed laser to the amplification subsystem along the first optical path is greater than a combination of a second flight time of the laser output from the seed laser to the detector subsystem along the second optical path and the time required for 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 fault includes at least one of a decrease in the power of the laser output and a deterioration in the linewidth of the laser output.

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

[0140] According to still another preferred embodiment of the present invention, there is provided a method for preventing damage to an amplification subsystem in a laser system, the method comprising receiving a laser output from a seed laser along a first optical path, amplifying the laser output to provide an amplified laser output, receiving a 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 stopping amplification upon detection of at least one fault in the laser output, wherein the stopping is performed when a first flight time of the laser output along the first optical path is greater than a combination of a second flight time of the laser output along the second optical path and a time required for the amplification to be stopped.

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

[0142] Preferably, the at least one fault includes at least one of a decrease 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] According to yet another preferred embodiment of the present invention, there is provided a laser amplifier system including a seed laser that provides 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 additional laser output upon stopping reception of the laser output from the seed laser, and a second amplifier that receives one of the first amplified laser output, the amplified spontaneous emission, and the additional laser output from the first amplifier and provides a second amplified laser output, wherein the amplification provided by the second amplifier is 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 includes a beam splitter that splits the laser output along first and second optical paths, where the first optical path is 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 the output from the detector, and a phase control module positioned along one of the first and second optical paths, the phase control module being operated by the electronic control module to correct the phase of the laser output in response to detection by the detector of interference in the combined laser output, and includes a laser amplifier system.

[0147] According to an even more preferred embodiment of the present invention, there is provided a method for preventing damage to an amplifier within a laser system, the method comprising receiving a laser output from a seed laser, providing a first amplified laser output by a first amplifier upon receiving the laser output from the seed laser, providing one of amplified spontaneous emission and additional laser output by the first amplifier upon cessation of receiving the laser output from the seed laser, receiving by a second amplifier one of the first amplified laser output, amplified spontaneous emission, and additional laser output and providing a second amplified laser output, the second amplified laser output being 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, filtering comprises splitting the laser output along first and second optical paths, wherein the first optical path is longer than the second optical path, splitting, detecting, by a detector, the combined laser output from the first and second optical paths, receiving, by an electronic control module, the output from the detector, and modifying, by the electronic control module, the phase of the laser output along one of the first and second optical paths in response to detection of interference in the combined laser output by the detector.

[0150] According to another preferred embodiment of the present invention, there is also provided a laser amplifier system comprising 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 when the first laser output stops, wherein the second laser output has a second power lower than the first power.

[0151] Preferably, the auxiliary laser subsystem includes an additional seed laser that provides the 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 where the first laser output is received and an outlet where the amplified laser output is provided, and the laser amplifier system includes a first reflection grating positioned at the inlet and a second reflection grating positioned at the outlet, and the first and second reflection gratings are combined with the amplification subsystem including the auxiliary laser subsystem.

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

[0154] Preferably, the second laser output has a wavelength different from that of 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 is a beam splitter that splits a first laser output along a first optical path and a second optical path, where the first optical path is 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 the output from the detector, and a phase control module positioned along one of the first and second optical paths, the phase control module being operated by the electronic control module to correct the phase of the first laser output in response to detection of interference in the combined laser output by the detector.

[0157] Preferably, the system also includes a detector subsystem for detecting a 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 non-linear 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, including providing a first laser output having a first power, amplifying the first laser output by the amplifier to provide an amplified laser output, and providing a second laser output at least when the provision of the first laser output is stopped, the second laser output having a second power lower than the first power.

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

[0162] Preferably, the amplifier includes an inlet where the first laser output is received and an outlet where the amplified laser output is provided, and also includes positioning a first reflection grating at the inlet and a second reflection grating at the outlet, and the first and second reflection gratings are combined with an amplifier that provides the second laser output.

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

[0164] Preferably, the second laser output has a wavelength different from that of 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 is to split the first laser output along the first and second optical paths, where the first optical path is longer than the second optical path, splitting, detecting the combined laser output from the first and second optical paths by a detector, receiving the output from the detector by an electronic control module, and based on the output from the detector and in response to the detection of interference in the combined laser output by the detector, correcting the phase of the first laser output along one of the first and second optical paths.

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

[0168] Preferably, the detection 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 being configured to exhibit a non-linear effect 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 Description of the Drawings

[0170] The present invention will be more fully understood and recognized based on the following detailed description in conjunction with the drawings.

Figure 1A

Figure 1B-1C

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Figure 17A-17B

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Figure 20A-20B

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Figure 22A-22B

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BEST MODE FOR CARRYING OUT THE INVENTION

[0171] Next, refer to FIG. 1A, which is a simplified schematic diagram of an optical phased array laser system for noise-corrected dynamic beam shaping constructed and operating in accordance with a preferred embodiment of the present invention, and FIGS. 1B and 1C, which are simplified graphical representations of phase change and noise correction in a system of the type shown in FIG. 1A.

[0172] As seen in FIG. 1A, by way of example, there is provided an optical phased array (OPA) laser system 100 as shown for use within a laser cutting system 102. The laser cutting system 102 may include an OPA laser system 100 attached in a spaced relationship to a multi-axis positioning table 104, on which an article 106 or the like can be cut using the laser system 100 as detailed below. Although the laser cutting system 102 is shown herein in the context of the table 104, it is understood that the system 102 can 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 the enlargement 110, the OPA laser 100 preferably comprises a seed laser 112 and a laser beam splitting and combining subsystem 114. The splitting and combining subsystem 114 preferably receives the output laser beam from the seed laser 112 and splits the output laser beam into a plurality of sub-beams along corresponding plurality of channels 116. Here, by way of example only, the output from the seed laser 112 is shown as being split into 10 sub-beams along 10 channels 116, but the splitting and combining subsystem 114 may include fewer or greater number of channels along which the output of the seed laser 112 is split, and typically may 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 the channels 116. Each phase-modulated sub-beam generated by splitting the output of the seed laser 112 and subsequent phase modulation preferably propagates towards the collimating lens 119. The individually collimated and phase-modulated sub-beams are then combined, for example, at the focusing lens 120 to form the output beam 122.

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

[0176] The phase of the output beam 122, and thus the position and shape of its far-field intensity pattern, are at least partially controlled by the relative phases of the constituent sub-beams combined to form the 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 the laser system 100 by the laser splitting and combining subsystem 114 dynamically changing the relative phases of the individual sub-beams, thereby changing the phase of the combined laser output 122 and dynamically controlling the position and shape of its far-field intensity pattern.

[0177] The relative phase of the sub-beams is preferably pre-determined according to a desired laser output pattern for cutting the article 106. Particularly preferably, the relative phase to be changed is applied by the phase control subsystem 130. The phase control subsystem 130 preferably forms part of the control electronic module 132 within the OPA laser 100 and preferably controls each phase modulator 118 to dynamically modulate the relative phase of the sub-beams along the channel 116.

[0178] Due to the noise inherent in the OPA system 100, the output beam 122 has noise. The noise of the output beam 122 is typically phase noise generated by thermal or mechanical effects and / or by the amplification process when the optical amplifier 124 is within the OPA system 100. A particular feature of the preferred embodiment of the present invention is that the laser system 100 includes a noise cancellation subsystem 140 that operates to provide a noise cancellation phase correction output to cancel the noise in the output beam 122 in the manner detailed below.

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

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

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

[0182] To facilitate the application of phase changes and noise corrections to the output beam 122, a portion of the output of the OPA laser 100 is preferably extracted and directed towards at least one detector, shown here as a single detector 150. The detector 150 may alternatively be embodied as a plurality of detectors, as will be detailed below with reference to FIGS. 6 - 8 and FIGS. 15 - 21. The extracted portion of the output beam preferably functions as a reference beam based on characteristics from which the necessary noise corrections and / or phase changes can be calculated. In the embodiment shown in FIG. 1A, a plurality of sub-beams along the channel 116 are directed towards a beam splitter 160. The 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, the beam splitter 160 may split each sub-beam with a transmittance of 99.9%: a reflectance of 0.01%.

[0183] The transmission portion 162 of the sub-beam preferably propagates towards the focusing lens 120, where the sub-beams are combined at the focusing lens 120 to form an output beam 122 having a far-field intensity pattern 166 that impinges on the surface of the article 106. The reflected portion 164 of the sub-beam is preferably reflected towards an additional focusing lens 168, where the sub-beams are combined at the additional focusing lens 168 to form an output reference beam 170 having a far-field intensity pattern 172 that impinges on the surface of the detector 150.

[0184] The specific structure and configuration of the beam splitting and recombining elements shown herein, including the beam splitter 160 and the focusing lenses 120 and 168, are merely illustrative and are shown in a highly simplified form. It is understood that the OPA laser system 100 can include various 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 combiners.

[0185] As described above herein, the shape and position of the far-field intensity pattern 166 of the output beam 122, as well as the corresponding shape and position of the far-field intensity pattern 172 of the reference beam 170, are constantly changing due to the ongoing change in the relative phase of the sub-beams. As a result, the far-field intensity pattern 172 is not fixed relative to the detector 150, but rather is constantly moving relative to the detector 150 in response to the combined relative phase of the constituent sub-beams. However, for the detector 150 to provide the necessary noise cancellation phase correction output, the far-field intensity pattern 172 must impinge on the detector 150 so that the detector measures the intensity of the far-field intensity pattern 172 and, consequently, applies noise correction accordingly, resulting in a fixed output beam.

[0186] The contradiction between the dynamic nature resulting from the phase change of the far-field intensity pattern 172 and the fixed nature required for the far-field intensity pattern 172 to derive and apply noise correction is advantageously resolved in the present invention by providing noise cancellation and phase change at different times and rates.

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

[0188] During the time intervals between the intermittent times when the far-field intensity pattern 172 impinges on the detector 150, the phase of the combined output beams 122 and 170 is changed to dynamically change the shape and position of the far-field intensity pattern of that phase as required to perform laser cutting of the article 106. The combined laser output is changed at a phase change rate exceeding the noise sampling rate to rapidly change the phase and thus the shape and position of the far-field intensity pattern. As an example, the noise sampling rate may be on the order of 10 to 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 change are preferably implemented in embodiments of the present invention can be best understood with reference to the graph 180 seen in FIG. 1A and its enlarged version shown in FIG. 1B.

[0190] As most clearly seen in FIG. 1B, graph 180 includes an upper portion 182 that displays the change in intensity over time of the far-field intensity pattern 172 measured by detector 150, and a lower portion 184 that displays the change over the same time period of the relative phase of a number of sub-beams contributing to output beam 122 and reference beam 170. For simplicity, the relative phases of 10 sub-beams are shown in graph 180, but it is understood that OPA system 100, and thus the description provided herein, is applicable to fewer, or more typically, far greater numbers of sub-beams.

[0191] As seen in the upper portion 182, intensity peak 186 represents the measured intensity of reference beam 170 when the far-field intensity pattern 172 passes over detector 150. As seen in the lower portion 184, intensity peak 186 occurs at intermittent times T i when the relative phase of each sub-beam is zero, which means there is no phase shift between the sub-beams, and thus the position of the combined output beam does not change and the far-field intensity pattern 172 is thus incident directly on detector 150. It is understood that detector 150 may alternatively be positioned such that the relative phase of the sub-beams there is non-zero. Further, as detailed below with reference to FIGS. 6-8 and FIGS. 15-21, multiple detectors may be used to enable measurement of the far-field intensity pattern 172 at multiple positions along them.

[0192] Since the far-field intensity pattern 172 is moved to either side of detector 150 and thus does not impinge directly on detector 150, between intensity peaks 186 the measured intensity is near zero. As understood from consideration of the upper portion 182, the magnitude of intensity peak 186 is not constant due to the presence of noise in the laser output beam, and that noise degrades the far-field intensity pattern 172.

[0193] As seen in the lower portion 184, the time interval T i during which the relative phase of the sub-beams is intermittent betweenis changed. In the phase change functions shown herein, the relative phase of the sub-beams is shown to change in a periodic and regular repeating pattern with equal phase shifts applied in the positive and negative directions. Such a simplified pattern is merely exemplary, and it is understood that the phase change need not necessarily be regularly repeated and need not be symmetric in the positive and negative directions. Further, the time interval T between is preferably an intermittent time T i but it is understood that it need not necessarily be so. Additionally, it is understood that at least one of the phase change rate and the noise sampling rate can be constant or can change over time.

[0194] The noise cancellation subsystem 140 preferably operates by considering the noise at the intermittent time T i and provides a noise cancellation phase correction output based on the noise detected at the intermittent time T i The noise cancellation subsystem 140 preferably uses an algorithm to detect the noise and correct the detected noise accordingly.

[0195] According to one exemplary embodiment of the present invention, the noise cancellation subsystem 140 uses an algorithm in which the relative phase of one channel is changed such that it is modified by a given phase change Δφ during each cycle of the movement of the far-field intensity pattern 172 with respect to the detector 150. Following such a number of cycles in which different phase changes Δφ are applied to the selected sub-beams over each cycle, the algorithm checks 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 in subsequent cycles, and the algorithm proceeds to optimize another sub-beam.

[0196] Graph 180 shows noise cancellation by this exemplary algorithm in channels A, B, and C of three sub-beams or a total of ten sub-beams. For simplicity, sub-beams A, B, and C are shown separately in FIG. 1C. In FIG. 1C, for the purposes described later in this specification, and to assist in distinguishing between the various sub-beams, the line styles of the lines representing the phase changes and noise corrections of sub-beams A, B, and C are modified compared to FIGS. 1A and 1B, respectively, as will be understood.

[0197] First seen in the case of channel A and most clearly understood from consideration of the enlarged view 190, the dashed line represents the pattern of change in the relative phase of sub-beam A that would be applied by the phase control subsystem 130 in the absence of any noise correction. This line is sometimes referred to as A uncorrected The dotted and dashed lines represent the actual relative phase of sub-beam A that has been corrected by the noise correction algorithm in order to find the optimal phase noise correction. This line is sometimes referred to as A corrected The corrected relative phase of A is shifted by a different Δφ corrected relative to the uncorrected relative phase of sub-beam A over the first five cycles of sub-beam A. The intensity 186 measured by detector 150 changes over the first five cycles of optimization of sub-beam A due to the intentional change in the relative phase shift. uncorrected A A After the first five cycles of sub-beam A, the algorithm checks for the maximum intensity and finds the phase change Δφ

[0198] that generates the maximum intensity. In this case, the maximum intensity is seen to be IA A generated by the second phase shift Δφ A The phase change applied to the relative phase change of sub-beam A is thus fixed at the second phase shift Δφ max for subsequent cycles, and the algorithm proceeds to optimize sub-beam B. A for subsequent cycles, and the algorithm proceeds to optimize sub-beam B.

[0199] During successive cycles of optimization of sub-beam A, the relative phases of the remaining portions of the sub-beams are each changed as normal at a rate of phase change far exceeding the noise sampling rate at which noise in sub-beam A is considered.

[0200] As can be further seen in the case of sub-beam B, and most clearly understood from consideration of the enlarged view 192, the thicker line during optimization of channel B represents the pattern of change in the relative phase of sub-beam B that would be applied by the phase control subsystem 130 in the absence of any noise correction. This line is sometimes referred to as B uncorrected The thin line during optimization of channel B represents the actual relative phase of sub-beam B that has been corrected by the noise correction algorithm in order to find the optimal phase noise correction. This line is sometimes referred to as B corrected The corrected relative phase of B is shifted by a different Δφ corrected from the uncorrected relative phase of B over 5 cycles of optimizing sub-beam B. The intensity 186 measured by the detector 150 changes over these 5 cycles of optimizing sub-beam B due to the intentional change in the relative phase shift. uncorrected B After these 5 cycles of sub-beam B, the algorithm checks for the maximum intensity and finds the phase change Δφ

[0201] that produces the maximum intensity. In this case, the maximum intensity is seen to be IAB B produced by the 4th phase shift Δφ B . The phase change applied to the relative phase change of sub-beam B is then fixed at the 4th phase shift Δφ max for subsequent cycles, and the algorithm proceeds to optimize sub-beam C. B

[0202] ​​During the five cycles of optimization of sub-beam B, it is understood that the relative phases of the remaining portions of the sub-beams are each changed as normal at a rate of phase change far exceeding the noise sampling rate at which the noise of sub-beam B is considered.

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

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

[0205] As will be understood by those skilled in the art, the specific parameters of the noise correction algorithm shown in graph 180 are merely illustrative and can be easily modified. For example, the phase shift Δφ may be optimized over a greater or fewer number of cycles than shown herein, each sub-beam may be fully optimized each time the sub-beam passes through detector 150, or some or all of the sub-beams may be optimized during each cycle in which the far-field intensity pattern passes through detector 150. Further, a discontinuous noise correction optimization algorithm, including but not limited to the stochastic parallel gradient descent optimization algorithm, may be alternatively implemented.

[0206] Using a dynamically shaped and noise-corrected optical phased array output beam for laser cutting is highly advantageous, enabling rapid beam steering, high-speed power modulation, high-speed beam focusing, and beam shaping. Compared to conventional laser cutting methods, using a dynamically shaped and noise-corrected optical phased array output improves both the speed and quality at which materials can be cut. It is understood that if noise correction according to a preferred embodiment of the present invention is provided, the shape and position of the optical phased array output beam deteriorate, thereby degrading the quality, speed, and accuracy of the laser cutting process.

[0207] To maintain the output beam intensity as the far-field intensity pattern of the beam moves, the movement of the output beam can be controlled so that, for certain laser cutting applications, the beam spends more time at lower intensity positions, thereby compensating for the 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] Next, refer to FIG. 2A, which is a simplified schematic diagram of an optical phased array laser system for noise-corrected dynamic beam shaping configured and operating in accordance with another preferred embodiment of the present invention, and FIGS. 2B and 2C, which are simplified graphical representations of phase change and noise correction within a system of the type shown in FIG. 2A.

[0209] As shown in FIG. 2A, by way of example, there is provided an optical phased array (OPA) laser system 200 as shown for use within an additive manufacturing system 202. The additive manufacturing system 202 may include an OPA laser system 200 mounted in a spaced relationship to a scanning mirror 203 and a multi-axis positioning table 204, and on the table 204, an article such as article 206 may be additively manufactured using the laser system 200. The additive manufacturing system 202 is shown herein in the context of the scanning mirror 203, but it is understood that the 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 the enlarged view 210, the OPA laser 200 preferably comprises a seed laser 212 and a laser beam splitting and combining subsystem 214. The splitting and combining subsystem 214 preferably receives the output laser beam from the seed laser 212 and splits the output laser beam into a plurality of sub-beams along a corresponding plurality of channels 216. Here, by way of example only, the output from the seed laser 212 is shown as being split into 10 sub-beams along 10 channels 216, but it is understood that the splitting and combining subsystem 214 may include fewer or greater numbers of channels along which the output of the seed laser 212 is split, and typically may 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 the channels 216. Each phase-modulated sub-beam generated by the splitting of the output of the seed laser 212 and subsequent phase modulation preferably propagates towards a collimating lens 219. The individually collimated and phase-modulated sub-beams are then combined, for example at a focusing lens 220, to form an output beam 222.

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

[0213] The phase of the output beam 222, and thus the position and shape of its far-field intensity pattern, are at least partially controlled by the relative phases of the constituent sub-beams combined to form the 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 the laser system 200 by having the laser splitting and combining subsystem 214 dynamically change the relative phases of the individual sub-beams, thereby changing the phase of the combined laser output 222 and dynamically controlling the position and shape of its far-field intensity pattern.

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

[0215] Due to the noise inherent in the OPA system 200, the output beam 222 has noise. The noise in the output beam 222 is typically phase noise generated by thermal or mechanical effects and / or by the amplification process when the optical amplifier 224 is within the OPA system 200. A particular feature of the preferred embodiment of the present invention is that the laser system 200 includes a noise cancellation subsystem 240 that operates to provide a noise cancellation phase correction output to cancel the noise in the output beam 222 in the manner detailed below.

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

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

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

[0219] To facilitate the application of phase changes and noise corrections to the output beam 222, a portion of the output of the OPA laser 200 is preferably extracted and directed towards at least one detector, shown here as a single detector 250. The detector 250 may alternatively be embodied as a plurality of detectors, as detailed below with reference to FIGS. 6 - 8 and FIGS. 15 - 21. The extracted portion of the output beam preferably functions as a reference beam based on characteristics from which the required noise corrections and / or phase changes can be calculated. In the embodiment shown in FIG. 2A, a plurality of sub - beams along the channel 216 are directed towards a beam splitter 260. The beam splitter 260 preferably splits each sub - beam into a transmitted portion 262 and a reflected portion 264 according to a pre - determined ratio. For example, the beam splitter 260 may split each sub - beam with a transmission rate of 99.9%: a reflectance rate of 0.01%.

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

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

[0222] As described above herein, the shape and position of the far-field intensity pattern 266 of output beam 222, and the corresponding shape and position of the far-field intensity pattern 272 of reference beam 270, are constantly changing due to the ongoing change in the relative phase of the sub-beams. As a result, the far-field intensity pattern 272 is not fixed relative to detector 250, but rather is constantly moving relative to detector 250 in response to the combined relative phase of the constituent sub-beams. However, in order for detector 250 to provide the necessary noise cancellation phase correction output, the far-field intensity pattern 272 must impinge on detector 250 in order for the detector to measure the intensity of far-field intensity pattern 272 and thus apply noise correction accordingly, resulting in a fixed output beam.

[0223] The contradiction between the dynamic nature of far-field intensity pattern 272 due to phase changes and the fixed nature required of far-field intensity pattern 272 for deriving and applying noise correction is advantageously resolved in the present invention by providing noise cancellation and phase changes at different times and rates relative to each other.

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

[0225] During the time intervals between the intermittent times when far-field intensity pattern 272 impinges on detector 250, the phase of the combined output beams 222, 270 is changed to dynamically change the shape and position of that far-field intensity pattern as required for performing additive manufacturing of article 206. The combined laser output is changed at a phase change rate that exceeds the noise sampling rate in order to rapidly change the phase and thus rapidly change the shape and position of the far-field intensity pattern. As an example, the noise sampling rate may be on the order of 10 to 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 change are preferably implemented in embodiments of the present invention can be best understood with reference to graph 280 seen in FIG. 2A and its enlarged version shown in FIG. 2B.

[0227] As most clearly seen in FIG. 2B, graph 280 includes an upper portion 282 that displays the change in intensity over time of the far-field intensity pattern 272 measured by detector 250, and a lower portion 284 that displays the change over the same time period of the relative phase of a number of sub-beams contributing to output beam 222 and reference beam 270. For simplicity, the relative phases of 10 sub-beams are shown in graph 280, but it is understood that OPA system 200, and thus the description provided herein, is applicable to fewer, or more typically, far more numerous sub-beams.

[0228] As seen in the upper portion 282, intensity peak 286 represents the measured intensity of reference beam 270 when the far-field intensity pattern 272 passes over detector 250. As seen in the lower portion 284, intensity peak 286 occurs at intermittent time T i when the relative phase of each sub-beam is zero, which means there is no phase shift between the sub-beams, and thus the position of the combined output beam does not change and the far-field intensity pattern 272 thus impinges directly on detector 250. It is understood that detector 250 may alternatively be positioned such that the relative phase of the sub-beams there is non-zero. Further, as detailed below with reference to FIGS. 6-8 and FIGS. 15-21, multiple detectors may be used to enable measurement of the far-field intensity pattern 272 at multiple positions along them.

[0229] Since the far-field intensity pattern 272 is moved to either side of detector 250 and thus does not impinge directly on detector 250, between intensity peaks 286, the measured intensity is near zero. As understood from the consideration of the upper portion 282, the magnitude of intensity peak 286 is not constant due to the presence of noise in the laser output beam, and that noise degrades the far-field intensity pattern 272.

[0230] As seen in the lower portion 284, the time interval T i between intermittent times T betweenIt is changed. In the phase change function shown in this specification, the relative phase of the sub-beams is shown to change in a periodic and regular repeating pattern with equal phase shifts applied in both the positive and negative directions. Such a simplified pattern is merely illustrative, and it is understood that the phase change does not necessarily have to be regularly repeated, nor does it necessarily have to be symmetric in the positive and negative directions. Further, the time interval T between is preferably overlapping with the intermittent time T i but it is understood that it does not necessarily have to overlap. Additionally, it is understood that at least one of the phase change rate and the noise sampling rate can be constant or can change over time.

[0231] The noise cancellation subsystem 240 preferably operates by considering the noise at the intermittent time T i and provides a noise cancellation phase correction output based on the noise detected at the intermittent time T i The noise cancellation subsystem 240 preferably uses an algorithm for detecting the noise and correcting the detected noise accordingly.

[0232] According to one exemplary embodiment of the present invention, the noise cancellation subsystem 240 uses an algorithm in which, during each cycle of the movement of the far-field intensity pattern 272 with respect to the detector 250, the relative phase of one channel is changed in such a way that the relative phase is corrected by a given phase change Δφ. Following such a number of cycles in which different phase changes Δφ are applied to the selected sub-beams over each cycle, the algorithm checks 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 in subsequent cycles, and the algorithm proceeds to optimize another sub-beam.

[0233] Graph 280 shows noise cancellation by this exemplary algorithm in channels A, B, and C of three sub-beams or a total of ten sub-beams. For simplicity, sub-beams A, B, and C are shown separately in FIG. 2C. In FIG. 2C, for the purpose of the following description in this specification, to assist in distinguishing between the various sub-beams, the line styles of the lines representing the phase change and noise correction of sub-beams A, B, and C are modified compared to FIGS. 2A and 2B, respectively, as will be understood.

[0234] First seen in the case of channel A and most clearly understood from consideration of the enlarged view 290, the dashed line represents the pattern of change in the relative phase of sub-beam A that would be applied by the phase control subsystem 230 in the absence of any noise correction. This line is sometimes referred to as A uncorrected The dotted line and the dashed line represent the actual relative phase of sub-beam A that has been corrected by the noise correction algorithm in order to find the optimal phase noise correction. This line is sometimes referred to as A corrected The corrected relative phase of A is shifted by a different Δφ corrected only relative to the uncorrected relative phase of A over the first five cycles of sub-beam A. The intensity 286 measured by detector 250 changes over the first five cycles of optimization of sub-beam A due to the intentional change in the relative phase shift. uncorrected A A After the first five cycles of sub-beam A, the algorithm checks for the maximum intensity and finds the phase change Δφ

[0235] that produces the maximum intensity. In this case, the maximum intensity is seen to be IA A produced by the second phase shift Δφ A The phase change applied to the relative phase change of sub-beam A is thus fixed at the second phase shift Δφ max for subsequent cycles, and the algorithm proceeds to optimize sub-beam B. A

[0236] ​During the continuous cycle of optimization of sub-beam A, it is understood that the relative phases of the remaining portions of the sub-beams are each changed as usual at a rate of phase change far exceeding the noise sampling rate at which the noise in sub-beam A is considered.

[0237] As can be further seen in the case of sub-beam B, and most clearly understood from consideration of the enlarged view 292, the thicker line during the optimization of channel B represents the pattern of change in the relative phase of sub-beam B that would be applied by the phase control subsystem 230 in the absence of any noise correction. This line is sometimes referred to as B uncorrected The thinner line during the optimization of channel B represents the actual relative phase of sub-beam B that has been corrected by the noise correction algorithm in order to find the optimal phase noise correction. This line is sometimes referred to as B corrected The corrected relative phase of B is shifted by a different Δφ corrected relative to the uncorrected relative phase of B over 5 cycles of the optimized sub-beam B. The intensity 286 measured by the detector 250 changes over these 5 cycles of the optimized sub-beam B due to the intentional change in the relative phase shift. uncorrected B After these 5 cycles of sub-beam B, the algorithm checks for the maximum intensity and finds the phase change Δφ

[0238] that produces the maximum intensity. In this case, the maximum intensity is seen to be IAB B produced by the 4th phase shift Δφ B . The phase change applied to the relative phase change of sub-beam B is then fixed at the 4th phase shift Δφ max for subsequent cycles, and the algorithm proceeds to optimize sub-beam C. B

[0239] ​​During five cycles of optimization of sub-beam B, it is understood that the relative phases of the remaining portions of the sub-beams are each changed as normal at a rate of phase change far exceeding the noise sampling rate at which the noise of sub-beam B is considered.

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

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

[0242] As will be understood by those skilled in the art, the specific parameters of the noise correction algorithm shown in graph 280 are merely illustrative and can be easily modified. For example, the phase shift Δφ may be optimized over a greater or fewer number of cycles than shown herein, each sub-beam may be fully optimized each time the sub-beam passes through detector 250, or some or all of the sub-beams may be optimized during each cycle in which the far-field intensity pattern passes through detector 250. Further, a discontinuous noise correction optimization algorithm, including but not limited to a stochastic parallel gradient descent optimization algorithm, may alternatively be implemented.

[0243] Using a dynamically shaped and noise-corrected optical phased array output beam for laser additive manufacturing is highly advantageous and enables rapid beam steering, high-speed power modulation, high-speed beam focusing, and beam shaping. Compared to conventional laser 3D printing methods, using a dynamically shaped and noise-corrected optical phased array output improves both the speed and quality with which an article can be manufactured. Without the provision of noise correction according to a preferred embodiment of the present invention, it is understood that the shape and position of the optical phased array output beam deteriorate, thereby degrading the quality, speed, and accuracy of the laser additive manufacturing process.

[0244] To maintain the output beam intensity as the far-field intensity pattern of the beam moves, the movement of the output beam can be controlled so that, for certain additive manufacturing applications, it is advantageous, thereby causing the beam to spend more time at lower intensity positions, compensating for the reduced power delivery there. Additionally or alternatively, an intensity profile mask, such as an ND filter, may be applied to the output beam to modify its intensity.

[0245] Next, refer to FIG. 3A, which is a simplified schematic diagram of an optical phased array laser system for noise-corrected dynamic beam shaping constructed and operating in accordance with a further preferred embodiment of the present invention, and FIGS. 3B and 3C, which are simplified graphical representations of phase change and noise correction within a system of the type shown in FIG. 3A.

[0246] As shown in FIG. 3A, an optical phased array (OPA) laser system 300 is provided, shown here by way of example as being used within a free space optical communication system 302. The free space optical communication system 302 may include an OPA laser system 300 mounted at an outdoor location such as a building, in a spaced relationship to a receiver 303 for receiving an optical signal emitted from the OPA laser 300. The free space optical communication system 302 is shown herein in the context of communication between two fixed points, but as will be understood by those skilled in the art, the free space optical communication system 302 can be adapted for use in communication between two positions moving relative to each other. The free space optical communication system 302 is shown herein in the context of terrestrial communication, but as will be understood by those skilled in the art, it is further understood that the free space optical communication system 302 can be adapted for use in extraterrestrial communication.

[0247] The free space optical communication system 302 is shown in FIG. 3A as including only a single OPA laser 300 and a receiver 303 for simplicity, but it will be understood that more single OPA lasers 300 and receivers 303 may be included depending on the communication requirements of the system 302. Further, it is further understood that the receiver 303 may be an OPA laser of a type similar to and having a receiving function as the OPA laser 300. Further, the OPA lasers 300 may include a receiving function to enable dual operation of the OPA lasers 300 and 303 for transmission and reception of optical signals therebetween.

[0248] As best seen in the enlarged view 310, the OPA laser 300 preferably comprises a seed laser 312 and a laser beam splitting and combining subsystem 314. The splitting and combining subsystem 314 preferably receives the output laser beam from the seed laser 312 and splits the output laser beam into a plurality of sub-beams along corresponding plurality of channels 316. Here, by way of example only, the output from the seed laser 312 is shown as being split into 10 sub-beams along 10 channels 316, but it is understood that the splitting and combining subsystem 314 may include a smaller number or a larger number of channels along which the output of the seed laser 312 is split, and typically may include a much larger 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 the channels 316. Each phase-modulated sub-beam generated by the splitting of the output of the seed laser 312 and subsequent phase modulation preferably propagates towards a collimating lens 319. The individually collimated and phase-modulated sub-beams are then combined, for example at a focusing lens 320, to form an output beam 322.

[0250] The splitting and combining subsystem 314 may also preferably provide laser amplification of the sub-beams after splitting the output beam of the seed laser 312 and before combining the sub-beams to form the output beam 322. Here, by way of example, the splitting and combining subsystem 314 is shown as including a plurality of optical amplifiers 324 positioned along corresponding channels of the channels 316 for amplifying each sub-beam. However, it is understood that such amplification is selectable according to the power output requirements of the OPA laser 300 and may be omitted.

[0251] The phase of the output beam 322, and thus the position and shape of its far-field intensity pattern, are at least partially controlled by the relative phases of the constituent sub-beams combined to form the output beam 322. In many applications such as free-space optical communication 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 the laser system 300 by the laser splitting and combining subsystem 314 dynamically changing the relative phases of the individual sub-beams, thereby changing the phase of the 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 pre-determined according to the desired laser output pattern for transmission to the receiver 303. Most preferably, the relative phases to be changed are applied by the phase control subsystem 330. The phase control subsystem 330 preferably forms part of the control electronics module 332 within the OPA laser 300 and controls each phase modulator 318 to dynamically modulate the relative phases of the sub-beams along the channel 316.

[0253] Due to the noise inherent in the OPA system 300, the output beam 322 has noise. The noise in the output beam 322 is typically phase noise generated by thermal or mechanical effects and / or by the amplification process if an optical amplifier 324 is within the OPA system 300. A particular feature of the preferred embodiment of the present invention is that the laser system 300 includes a noise cancellation subsystem 340 that operates to provide a noise cancellation phase correction output to cancel the noise in the output beam 322 in the manner detailed below.

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

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

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

[0257] To facilitate the application of phase changes and noise corrections to the output beam 322, a portion of the output of the OPA laser 300 is preferably extracted and directed towards at least one detector, shown here as a single detector 350. The detector 350 may alternatively be embodied as a plurality of detectors, as will be detailed below with reference to FIGS. 6 - 8 and FIGS. 15 - 21. The extracted portion of the output beam preferably functions as a reference beam based on characteristics from which the required noise corrections and / or phase changes can be calculated. In the embodiment shown in FIG. 3A, a plurality of sub - beams along channel 316 are directed towards a beam splitter 360. The beam splitter 360 preferably divides each sub - beam into a transmitted portion 362 and a reflected portion 364 according to a pre - determined ratio. For example, the beam splitter 360 may divide each sub - beam with a transmission rate of 99.9%: a reflectance of 0.01%.

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

[0259] The specific structure and configuration of the beam splitting and recombining elements shown herein, including the beam splitter 360 and the focusing lenses 320 and 368, are merely illustrative and are shown in a highly simplified form. It is understood that the OPA laser system 300 may include additional optical elements, such as various such elements, and by way of example only, additional or alternative lenses, optical fibers, and coherent free - space far - field combiners.

[0260] As described above in this specification, the shape and position of the far-field intensity pattern 366 of the output beam 322, as well as the corresponding shape and position of the far-field intensity pattern 372 of the reference beam 370, are constantly changing due to the ongoing change in the relative phase of the sub-beams. As a result, the far-field intensity pattern 372 is not fixed to the detector 350; rather, it is constantly being moved relative to the detector 350 in accordance with the combined relative phase of the constituent sub-beams. However, for the detector 350 to provide the required noise cancellation phase correction output, the far-field intensity pattern 372 must impinge on the detector 350 in order for the detector to measure the intensity of the far-field intensity pattern 372 and thus apply noise correction accordingly, resulting in a fixed output beam.

[0261] The contradiction between its dynamic nature due to the phase change of the far-field intensity pattern 372 and the fixed nature required of the far-field intensity pattern 372 for deriving and applying noise correction is advantageously resolved in the present invention by providing noise cancellation and phase change at mutually different times and rates.

[0262] The noise cancellation phase correction output is provided based on taking into account the noise measured at the detector 350 at the noise sampling rate. The output beam 322 is controlled in such a way that the far-field intensity pattern 372 impinges on the detector 350 at a rate equal to or faster than the required noise sampling rate during the process of the dynamic change in the shape and position of the output and reference far-field intensity patterns 366, 372. The noise of the reference beam 370 is taken into account during these intermittent times when the far-field intensity pattern 372 is returned to the detector 350.

[0263] During the time interval between the intermittent times when the far-field intensity pattern 372 impinges on the detector 350, the phase of the combined output beams 322, 370 is changed to dynamically vary the shape and position of the far-field intensity pattern of that phase as required to perform the additive manufacturing of the article 206. The combined laser output is changed at a phase change rate that exceeds the noise sampling rate in order to rapidly change the phase and thus rapidly change 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 change are preferably implemented in embodiments of the present invention can be best understood with reference to the graph 380 seen in FIG. 3A and its enlarged version shown in FIG. 3B.

[0265] As most clearly seen in FIG. 3B, the graph 380 includes an upper portion 382 that displays the change in intensity of the far-field intensity pattern 372 measured at the detector 350 over time, and a lower portion 384 that displays the change in the relative phase of a number of sub-beams contributing to the output beam 322 and the reference beam 370 over the same time period. For simplicity, the relative phases of 10 sub-beams are shown in the graph 380, but it is understood that the OPA system 300 and thus the description provided herein is applicable to fewer, or more typically, far more sub-beams.

[0266] As seen in the upper portion 382, the intensity peak 386 represents the measured intensity of the reference beam 370 when the far-field intensity pattern 372 passes over the detector 350. As seen in the lower portion 384, the intensity peak 386 occurs at the intermittent time T when the relative phase of each sub-beam is zero iOccurs, which means there is no phase shift between the sub-beams. Therefore, the position of the combined output beam does not change, and thus the far-field intensity pattern 372 is incident directly on the detector 350. It is understood that the detector 350 may alternatively be positioned such that the relative phase of the sub-beams there is non-zero. Further, as will be detailed below with reference to FIGS. 6-8 and FIGS. 15-21, it may be possible to use a plurality of detectors to measure the far-field intensity pattern 372 at a plurality of positions along them.

[0267] The far-field intensity pattern 372 is moved to either side of the detector 350 and thus does not directly impinge on the detector 350. So, between the intensity peaks 386, the measured intensity is close to zero. As understood from the consideration of the upper portion 382, the magnitude of the intensity peaks 386 is not constant due to the presence of noise in the laser output beam, and that noise degrades the far-field intensity pattern 372.

[0268] As seen in the lower portion 384, the relative phase of the sub-beams changes during an intermittent time T i for a time interval T between within. In the phase change function shown herein, the relative phase of the sub-beams is shown to change in a periodic and regular repeating pattern with equal phase shifts applied in both the positive and negative directions. Such a simplified pattern is merely illustrative, and it is understood that the phase change need not necessarily be regularly repeated and need not necessarily be symmetric in the positive and negative directions. Further, the time interval T between is preferably, but not necessarily, overlapping with the intermittent time T i It is understood that additionally, at least one of the phase change rate and the noise sampling rate may be constant or may change over time.

[0269] The noise cancellation subsystem 340 preferably operates by taking into account the noise at an intermittent time T i and at an intermittent time Ti Based on the noise detected at i , a noise cancellation phase correction output is provided. The noise cancellation subsystem 340 preferably uses an algorithm for detecting noise and correcting the detected noise accordingly.

[0270] According to one exemplary embodiment of the present invention, the noise cancellation subsystem 340 uses an algorithm in which, during each cycle of movement of the far-field intensity pattern 372 relative to the detector 350, the relative phase of one channel is varied in such a way that the relative phase is modified by a given phase change Δφ. Following such a number of cycles in which different phase changes Δφ are applied to the selected sub-beams over each cycle, the algorithm checks 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 in subsequent cycles, and the algorithm proceeds to optimize another sub-beam.

[0271] Graph 380 shows noise cancellation by this exemplary algorithm in channels A, B, and C of three sub-beams or a total of ten sub-beams. For simplicity, sub-beams A, B, and C are shown separately in FIG. 3C. In FIG. 3C, for the purposes of the description that follows herein, it is understood that the line styles of the lines representing the phase changes and noise corrections of sub-beams A, B, and C have been modified compared to FIGS. 3A and 3B to assist in distinguishing between the various sub-beams.

[0272] In the case of channel A, first seen and most clearly understood from consideration of the enlarged view 390, the dashed line represents the pattern of change in the relative phase of sub-beam A that would be applied by the phase control subsystem 330 in the absence of any noise correction. This line may be referred to as A uncorrected The dotted line and the dashed line represent the actual relative phase of sub-beam A corrected by the noise correction algorithm to find the optimal phase noise correction. This line may be referred to as Acorrected is sometimes referred to as A corrected The modified relative phase of A is different by Δφ from the unmodified relative phase of A over the first 5 cycles of sub-beam A uncorrected only shifted. The intensity 386 measured by detector 350 changes over the first 5 cycles of optimization of sub-beam A due to the intentional change in relative phase shift A After the first 5 cycles of sub-beam A, the algorithm checks for the maximum intensity and finds the phase change Δφ that produces the maximum intensity

[0273] In this case, the maximum intensity is seen to be IA produced by the second phase shift Δφ A The phase change applied to the relative phase change of sub-beam A is thus fixed at the second phase shift Δφ for subsequent cycles, and the algorithm proceeds to optimize sub-beam B A In the continuous cycles of optimization of sub-beam A, it is understood that the relative phases of the remaining parts of the sub-beams are each changed as usual at a phase change rate far exceeding the noise sampling rate at which noise in sub-beam A is considered max As further seen in the case of sub-beam B, and most clearly understood from the consideration of the enlarged view 392, the thicker line during the optimization of channel B represents the pattern of change in the relative phase of sub-beam B that would be applied by the phase control subsystem 330 in the absence of any noise correction A This line is sometimes referred to as B

[0274] The thin line during the optimization of channel B represents the actual relative phase of sub-beam B corrected by the noise correction algorithm to find the optimal phase noise correction

[0275] This line is sometimes referred to as B uncorrected The modified relative phase of B is over 5 cycles of optimizing sub-beam B corrected for B corrected only shifted. The intensity 386 measured by detector 350 changes over the first 5 cycles of optimization of sub-beam B due to the intentional change in relative phase shift uncorrectedis shifted by a different Δφ relative to the uncorrected relative phase B only. The intensity 386 measured by detector 350 changes over these 5 cycles of the optimized sub-beam B due to the intentional change in the relative phase shift.

[0276] After these 5 cycles of sub-beam B, the algorithm checks for the maximum intensity and finds the phase change Δφ B that produces it. In this case, the maximum intensity is the IAB B produced by the fourth phase shift Δφ max and is thus seen. The phase change applied to the relative phase change of sub-beam B is then fixed at the fourth phase shift Δφ B for subsequent cycles, and the algorithm proceeds to optimize sub-beam C.

[0277] It is understood that during the 5 cycles of optimization of sub-beam B, the relative phases of the remaining parts of the sub-beams are each changed as normal at a phase change rate far exceeding the noise sampling rate at which noise in sub-beam B is considered.

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

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

[0280] As will be understood by those skilled in the art, it is understood that the specific parameters of the noise correction algorithm shown in graph 380 are merely illustrative and can be easily modified. For example, the phase shift Δφ may be optimized over a greater or fewer number of cycles than shown herein, each sub-beam may be fully optimized each time the sub-beam 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. Further, a discontinuous noise correction optimization algorithm, including but not limited to the stochastic parallel gradient descent optimization algorithm, may alternatively be implemented.

[0281] Using the dynamically shaped and noise-corrected optical phased array output beam for free space optical communication is highly advantageous and enables rapid beam steering, high-speed power modulation, high-speed beam focusing, and beam shaping adjustment. Compared with conventional free space optical communication methods, using the dynamically shaped and noise-corrected optical phased array output improves both the speed and quality of communication. It is understood that without the provision of noise correction according to a preferred embodiment of the present invention, the shape and position of the optical phased array output beam would deteriorate, thereby degrading the quality, speed, and accuracy of the transmitted laser output.

[0282] To maintain the output beam intensity as the far-field intensity pattern of the beam moves, the movement of the output beam can be controlled so as to be advantageous for certain optical communication applications, thereby causing the beam to spend more time at lower intensity positions and compensating for the reduction in power delivery there. Additionally or alternatively, an intensity profile mask, such as an ND filter, may be applied to the output beam to modify its intensity.

[0283] Next, refer to FIG. 4A, which is a simplified schematic diagram of an optical phased array laser system for noise-corrected dynamic beam shaping constructed and operating in still another preferred embodiment of the present invention, and FIGS. 4B and 4C, which are simplified graphical representations of phase change and noise correction within a system of the type shown in FIG. 4A.

[0284] As seen in FIG. 4A, by way of example, there is provided an optical phased array (OPA) laser system 400, shown as being used within a laser welding system 402. The laser welding system 402 may include an OPA laser system 400 mounted on or within a portion of a laser welding robot 404. An article, such as article 406, may be welded by the laser welding robot 404, as detailed below. Although the laser welding system 402 is shown herein in the context of the welding robot 404, it will be understood by those skilled in the art that the system 402 may be adapted for use with any welding setup.

[0285] As best seen in the enlarged view 410, the OPA laser 400 preferably comprises a seed laser 412 and a laser beam splitting and combining subsystem 414. The splitting and combining subsystem 414 preferably receives the output laser beam from the seed laser 412 and splits the output laser beam into a plurality of sub-beams along corresponding plurality of channels 416. Here, by way of example only, the output from the seed laser 412 is shown as being split into 10 sub-beams along 10 channels 416, but it will be understood that the splitting and combining subsystem 414 may include fewer or greater number of channels along which the output of the seed laser 412 is split, and typically may 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 channel 416. Each phase-modulated sub-beam generated by splitting the output of the seed laser 412 and subsequent phase modulation preferably propagates towards the collimating lens 419. The individually collimated and phase-modulated sub-beams are then combined, for example, at the focusing lens 420 to form the output beam 422.

[0287] The splitting and combining subsystem 414 may also preferably provide laser amplification of the sub-beams after splitting the output beam of the seed laser 412 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 a plurality of optical amplifiers 424 positioned along the corresponding channels of channel 416 for amplifying each sub-beam. However, it is understood that such amplification can be selected according to the power output requirements of the OPA laser 400 and may be omitted.

[0288] The phase of the output beam 422, and thus the position and shape of its far-field intensity pattern, are at least partially controlled by the relative phases of the constituent sub-beams combined to form the 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 the laser system 400 by the laser splitting and combining subsystem 414 dynamically changing the relative phases of the individual sub-beams, thereby changing the phase of the combined laser output 422 and dynamically controlling the position and shape of its far-field intensity pattern.

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

[0290] Due to the noise inherent in the OPA system 400, the output beam 422 has noise. The noise of the output beam 422 is typically phase noise generated by thermal or mechanical effects and / or by the amplification process if the optical amplifier 424 is within the OPA system 400. A particular feature of the preferred embodiment of the present invention is that the laser system 400 operates to provide a noise cancellation phase correction output to cancel the noise in the output beam 422 in the manner detailed below, including a noise cancellation subsystem 440.

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

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

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

[0294] To facilitate the application of phase changes and noise corrections to the output beam 422, a portion of the output of the OPA laser 400 is preferably extracted and directed towards at least one detector, shown here as a single detector 450. The detector 450 may alternatively be embodied as a plurality of detectors, as will be detailed below with reference to FIGS. 6 - 8 and FIGS. 15 - 21. The extracted portion of the output beam preferably functions as a reference beam based on characteristics from which the necessary noise corrections and / or phase changes can be calculated. In the embodiment shown in FIG. 4A, a plurality of sub-beams along the channel 416 are directed towards a beam splitter 460. The 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, the beam splitter 460 may split each sub-beam with a transmittance of 99.9%: a reflectance of 0.01%.

[0295] The transmission portion 462 of the sub-beam preferably propagates towards the focusing lens 420, where the sub-beams are combined at the focusing lens 420 to form an output beam 422 having a far-field intensity pattern 466 that impinges on the article 406. The reflected portion 464 of the sub-beam is preferably reflected towards an additional focusing lens 468, where the sub-beams are combined at the additional focusing lens 468 to form an output reference beam 470 having a far-field intensity pattern 472 that impinges on the surface of the detector 450.

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

[0297] As described above herein, the shape and position of the far-field intensity pattern 466 of the output beam 422, and the corresponding shape and position of the far-field intensity pattern 472 of the reference beam 470, vary constantly due to the ongoing change in the relative phase of the sub-beams. As a result, the far-field intensity pattern 472 is not fixed to the detector 450, but rather is constantly shifted relative to the detector 450 in accordance with the combined relative phase of the constituent sub-beams. However, for the detector 450 to provide the necessary noise cancellation phase correction output, the far-field intensity pattern 472 must impinge on the detector 450 so that the detector measures the intensity of the far-field intensity pattern 472 and, consequently, applies noise correction accordingly, resulting in a fixed output beam.

[0298] The contradiction between its dynamic properties resulting from the phase change of the far-field intensity pattern 472 and the fixed properties required for the far-field intensity pattern 472 to derive and apply noise correction is advantageously resolved in the present invention by providing noise cancellation and phase change at different times and rates.

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

[0300] During the time intervals between the intermittent times when the far-field intensity pattern 472 impinges on the detector 450, the phase of the combined output beams 422, 470 is changed to dynamically change the shape and position of the far-field intensity pattern as required to perform laser welding of the article 406. The combined laser output is changed at a phase change rate exceeding the noise sampling rate to rapidly change the phase and thus 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 change are preferably implemented in embodiments of the present invention can be best understood with reference to the graph 480 seen in FIG. 4A and its enlarged version shown in FIG. 4B.

[0302] As most clearly seen in FIG. 4B, graph 480 includes an upper portion 482 that displays the change in intensity over time of the far-field intensity pattern 472 measured by detector 450, and a lower portion 484 that displays the change over the same time period of the relative phase of a number of sub-beams contributing to output beam 422 and reference beam 470. For simplicity, the relative phases of 10 sub-beams are shown in graph 480, but it is understood that OPA system 400, and thus the description provided herein, is applicable to fewer, or more typically, a much larger number of sub-beams.

[0303] As seen in the upper portion 482, intensity peak 486 represents the measured intensity of reference beam 470 when the far-field intensity pattern 472 passes over detector 450. As seen in the lower portion 484, intensity peak 486 occurs at intermittent times T i when the relative phase of each sub-beam is zero, which means there is no phase shift between the sub-beams, and thus the position of the combined output beam does not change, and thus the far-field intensity pattern 472 impinges directly on detector 450. It is understood that detector 450 may alternatively be positioned such that the relative phase of the sub-beams there is non-zero. Further, as will be described in detail below with reference to FIGS. 6-8 and FIGS. 15-21, it may be possible to use multiple detectors to measure the far-field intensity pattern 472 at multiple positions along them.

[0304] Since the far-field intensity pattern 472 is moved to either side of detector 450 and thus does not impinge directly on detector 450, between intensity peaks 486, the measured intensity is near zero. As understood from the consideration of the upper portion 482, the magnitude of intensity peak 486 is not constant due to the presence of noise in the laser output beam, and that noise degrades the far-field intensity pattern 472.

[0305] As seen in the lower portion 484, the time interval T i between intermittent times T betweenIt is changed. In the phase change function shown in this specification, the relative phase of the sub-beams is shown to change in a periodic and regular repeating pattern with equal phase shifts applied in both the positive and negative directions. Such a simplified pattern is merely illustrative, and it is understood that the phase change does not necessarily have to be regularly repeated, nor does it necessarily have to be symmetric in the positive and negative directions. Further, the time interval T between is preferably an intermittent time T i but it is understood that it does not necessarily have to overlap. Additionally, it is understood that at least one of the phase change rate and the noise sampling rate can be constant or can change over time.

[0306] The noise cancellation subsystem 440 preferably operates by considering the noise at the intermittent time T i and provides a noise cancellation phase correction output based on the noise detected at the intermittent time T i The noise cancellation subsystem 440 preferably uses an algorithm for detecting noise and correcting the detected noise accordingly.

[0307] According to one exemplary embodiment of the present invention, the noise cancellation subsystem 440 uses an algorithm in which, during each cycle of the movement of the far-field intensity pattern 472 with respect to the detector 150, the relative phase of one channel is changed in such a way that the relative phase is corrected by a given phase change Δφ. Following such a number of cycles in which different phase changes Δφ are applied to the selected sub-beams over each cycle, the algorithm checks 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 in subsequent cycles, and the algorithm proceeds to optimize another sub-beam.

[0308] Graph 480 shows noise cancellation by this exemplary algorithm in channels A, B, and C of three sub-beams or a total of ten sub-beams. For simplicity, sub-beams A, B, and C are shown separately in FIG. 4C. In FIG. 4C, for the purpose of the following description in this specification, to assist in distinguishing between the various sub-beams, the line styles of the lines representing the phase changes and noise corrections of sub-beams A, B, and C are modified compared to FIGS. 4A and 4B, respectively, as will be understood.

[0309] First seen in the case of channel A and most clearly understood from consideration of the enlarged view 490, the dashed line represents the pattern of the change in the relative phase of sub-beam A that would be applied by the phase control subsystem 430 in the absence of any noise correction. This line is sometimes referred to as A uncorrected The dotted and dashed lines represent the actual relative phase of sub-beam A corrected by the noise correction algorithm to find the optimal phase noise correction. This line is sometimes referred to as A corrected The corrected relative phase of A is shifted by a different Δφ corrected only relative to the uncorrected relative phase of sub-beam A over the first 5 cycles of sub-beam A. The intensity 486 measured by the detector 450 changes over the first 5 cycles of optimization of sub-beam A due to the intentional change in the relative phase shift. uncorrected After the first 5 cycles of sub-beam A, the algorithm checks for the maximum intensity and finds the phase change Δφ A that produces the maximum intensity. In this case, the maximum intensity is seen to be IA

[0310] generated by the second phase shift Δφ A The phase change applied to the relative phase change of sub-beam A is thus fixed at the second phase shift Δφ A for subsequent cycles, and the algorithm proceeds to optimize sub-beam B. max for subsequent cycles, and the algorithm proceeds to optimize sub-beam B. A for subsequent cycles, and the algorithm proceeds to optimize sub-beam B.

[0311] During successive cycles of optimization of sub-beam A, the relative phases of the remaining portions of the sub-beams are each changed as usual at a rate of phase change far exceeding the noise sampling rate at which noise in sub-beam A is considered.

[0312] As can be further seen in the case of sub-beam B, and most clearly understood from consideration of the enlarged view 492, the thicker line during optimization of channel B represents the pattern of change in the relative phase of sub-beam B that would be applied by phase control subsystem 430 in the absence of any noise correction. This line is sometimes referred to as B uncorrected The thinner line during optimization of channel B represents the actual relative phase of sub-beam B that has been corrected by the noise correction algorithm to find the optimal phase noise correction. This line is sometimes referred to as B corrected The corrected relative phase of B is shifted by a different Δφ corrected from the uncorrected relative phase of B over 5 cycles of optimizing sub-beam B. The intensity 486 measured by detector 450 changes over these 5 cycles of optimizing sub-beam B due to the intentional change in relative phase shift. uncorrected B After these 5 cycles of sub-beam B, the algorithm checks for the maximum intensity and finds the phase change Δφ

[0313] that produces the maximum intensity. In this case, the maximum intensity is seen to be IAB B produced by the 4th phase shift Δφ B . The phase change applied to the relative phase change of sub-beam B is then fixed at the 4th phase shift Δφ max for subsequent cycles, and the algorithm proceeds to optimize sub-beam C. B

[0314] ​​During five cycles of optimization of sub-beam B, it is understood that the relative phases of the remaining portions of the sub-beams are each changed as normal at a rate of phase change far exceeding the noise sampling rate at which the noise of sub-beam B is considered.

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

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

[0317] As will be understood by those skilled in the art, the specific parameters of the noise correction algorithm shown in graph 480 are merely illustrative and can be easily modified. For example, the phase shift Δφ may be optimized over more or fewer cycles than shown herein, each sub-beam may be fully optimized each time the sub-beam passes through detector 450, or some or all of the sub-beams may be optimized during each cycle in which the far-field intensity pattern passes through detector 450. Further, a discontinuous noise correction optimization algorithm, including but not limited to a stochastic parallel gradient descent optimization algorithm, may be alternatively implemented.

[0318] Using a dynamically shaped and noise-corrected optical phased array output beam for laser welding is highly advantageous and enables rapid beam steering, high-speed power modulation, high-speed beam focusing, and beam shaping. Compared to conventional laser cutting methods, using a dynamically shaped and noise-corrected optical phased array output improves both the speed and quality at which materials can be cut. Without the provision of noise correction according to a preferred embodiment of the present invention, it is understood that the shape and position of the optical phased array output beam deteriorate, thereby degrading the quality, speed, and accuracy of the laser cutting process.

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

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

[0321] As detailed above, using a dynamically shaped and noise-corrected optical phased array output beam in various laser applications including, but not limited to, laser cutting, laser additive manufacturing, laser welding, and laser free space optical communication, is highly advantageous and enables rapid beam steering, high-speed power modulation, high-speed beam focusing, and beam shaping adjustment. Exemplary far-field patterns showing 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. Mechanical beam steering may result from the motion provided by the positioning table 104 shown in FIG. 1A, from mirror scanning such as 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 the motion provided by the robot 404 shown in FIG. 4A, or from any other cause of mechanical motion.

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

[0323] As seen in FIG. 5A, the dynamically shaped and noise-corrected optical phased array output beam may exhibit rapid multi-point jumps, as indicated by the first beam path 502, which complement the beam motion resulting from mechanical scanning represented by the second beam path 504.

[0324] As an example, such multi-point jumps may be advantageous in material processing where it takes time for energy to be absorbed at each point of the material being processed. The multi-point jump allows the beam to jump between points and return to each point multiple times, thus facilitating parallel processing of a large number of points. As a further example, such multi-point jumps may be advantageous in a communication system because transmissions to multiple locations can be performed in parallel.

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

[0326] An exemplary telecentric beam pattern showing an electro-optic beam wobble according to a preferred embodiment of the present invention is shown in FIG. 5C. As seen in FIG. 5C, the dynamically shaped and noise-corrected optical phased array output beam is controlled to exhibit a rapid beam wobble 510 along the direction of beam motion 512 and is particularly useful, for example, in a laser welding system such as that shown in FIG. 4A.

[0327] Exemplary telecentric beam patterns showing dynamic modification of the depth of focus according to preferred embodiments of the present invention are shown in FIGS. 5D-5F. As seen in FIGS. 5D-5F, the depth of the beam focus may be dynamically varied by the system of the present invention, allowing for variable beam focal distances for scanning (FIG. 5E) and deep cutting (FIGS. 5D and 5F) and is particularly useful, for example, in cutting, additive manufacturing, and welding systems of the types shown in FIGS. 1A, 2A, and 4A.

[0328] An exemplary far-field beam pattern showing dynamic beam shaping according to a preferred embodiment of the present invention is shown in FIG. 5G. As can be seen in FIG. 5G, the shape of the beam may vary dynamically to produce a desired beam shape output. This can be particularly useful, for example, in cutting, additive manufacturing, and welding systems of the types shown in FIGS. 1A, 2A, and 4A, and 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 enables the beam to be dynamically adapted to an optimal shape at any point.

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

[0330] Next, referring to FIG. 6, FIG. 6 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 operating in accordance with a preferred embodiment of the present invention.

[0331] As shown 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 a plurality of sub-beams along corresponding plurality of channels 616. Here, by way of example only, the output from the seed laser 612 is shown as being split into four sub-beams along four channels 616, but the splitting and combining subsystem 614 may include fewer or greater numbers of channels along which the output of the seed laser 612 is split, and it is understood that typically it may 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 the channels 616. Each phase-modulated sub-beam generated by the splitting of the output of the seed laser 612 and subsequent phase modulation preferably propagates towards a collimating lens 619. The individually collimated and phase-modulated sub-beams are then combined, for example, at a focusing lens 620 to form an output beam 622.

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

[0334] The phase of the output beam 622, and thus the position and shape of its far-field intensity pattern, are at least partially controlled by the relative phases of the constituent sub-beams combined to form the output beam 622. As described herein with reference to FIGS. 1A-5G, in many applications such as laser cutting, laser welding, laser additive manufacturing, and free-space optical communication, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. This can be achieved in the laser system 600 by the laser splitting and combining subsystem 614 dynamically changing the relative phases of the individual sub-beams, thereby changing the phase of the 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 pre-determined according to the desired laser output pattern. Particularly preferably, the relative phases to be changed are applied by the phase control subsystem 630. The phase control subsystem 630 preferably forms part of the 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 with reference to the phase control subsystems 130, 230, 330, 430 of FIGS. 1A, 2A, 3A, and 4A, respectively.

[0336] Due to the noise inherent in the OPA system 600, the output beam 622 has noise. The noise in the output beam 622 is typically phase noise generated by thermal or mechanical effects and / or by the amplification process when the optical amplifier 624 is within the OPA system 600. The OPA system 600 preferably includes a noise cancellation subsystem 640 that operates to provide a noise cancellation phase correction output to cancel the noise in the output beam 622 in a manner detailed below.

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

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

[0339] According to a preferred embodiment of the present invention, a plurality of sub-beams along channel 616 are directed towards a beam splitter 660. The 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, the beam splitter 660 may split each sub-beam with a transmittance of 99.9%: a reflectance of 0.01%.

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

[0341] As described herein with reference to FIGS. 1A-4C, the noise cancellation phase correction output is preferably provided based on taking into account the noise measured by detector 650 at the noise sampling rate. Output beam 622 is controlled in such a way that far-field intensity pattern 672 impinges on detector 650 at a rate equal to or faster than the required noise sampling rate during the process of dynamic changes to the shape and position of the output and reference far-field intensity patterns 666, 672. The noise of 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 the intermittent times when far-field intensity pattern 672 impinges on detector 650, the phase of the combined output beams 622, 670 is changed to dynamically change the shape and position of that far-field intensity pattern. The combined laser output is changed at a phase change rate that exceeds the noise sampling rate in order to rapidly change the phase and thus rapidly change the shape and position of the far-field intensity pattern. Thus, noise cancellation and phase change are preferably provided at different times and rates relative to each other.

[0343] The use of a plurality of detectors 650 rather than a single detector has been found to be highly advantageous in certain embodiments of the present invention, which provides various advantages detailed below. However, if the focal length of the additional focusing lens 668 is relatively short, as may be desirable to form system 600 compactly, the detectors among the plurality of detectors 650 preferably need to be positioned very closely to each other. The desired detector spacing can be on the order of a few microns. Such a high spatial density arrangement of detectors 650 is typically unrealistic, especially in the case of conventional detectors having dimensions much larger than the preferred detector spacing.

[0344] To enable high spatial density sampling of the far-field intensity pattern 672 by the plurality of detectors 650, the OPA system 600 preferably includes a plurality of optical paths, embodied herein by way of example as a plurality of optical fibers 680, and accordingly coupled to the plurality of detectors 650. The reference beam 670 preferably enters one or more of the plurality of open ends 682 of the optical fibers 680 and travels along it to the corresponding detector among the detectors 650. The plurality of ends 682 of the plurality of optical fibers 680 are preferably arranged to have a spatial density greater than the spatial density of the plurality of detectors 650, which means that the spacing between the open ends 682 of adjacent optical fibers 680 of the optical fibers 680 is smaller than the spacing between the corresponding adjacent detectors of the detectors 650. Thereby, without the need for the detectors themselves to be physically positioned at closely spaced positions of the detectors 650 where the far-field intensity pattern 672 is sampled, the detectors 650 can detect the far-field intensity pattern 672 that is closely spaced along them.

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

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

[0347] The plurality of closely spaced optical paths are not limited to being embodied as a plurality of optical fibers 680 having end portions 682 that are very closely spaced and having an end-to-end spacing between the fibers that is less than the detector-to-detector spacing of detector 650. Rather, the scope of the present invention is extended to include any suitable plurality of optical paths that can deliver a far-field intensity reference pattern 672 along them to a plurality of detectors 650 and that can be arranged with a sufficiently large spatial density.

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

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

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

[0351] As shown in FIG. 9, an optical phased array (OPA) laser 900 is provided. The OPA laser 900 may be generally similar to the OPA laser 600 of FIG. 6 in its related aspects, except for the detector arrangement used therein. The OPA laser 600 preferably uses a plurality of detectors that receive the output beam through a corresponding plurality of closely spaced optical paths, but the OPA laser 900 does not necessarily use a plurality of detectors.

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

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

[0354] More specifically, the phases of the output and reference beams 622, 670 are preferably dynamically changed by the phase control subsystem 630 such that the output and reference beams 622 and 670 cross a predetermined orbit such as a star-shaped orbit corresponding to the shape of the star-shaped transmission region 982. When there is no noise in the OPA laser 900, the orbits crossed by the output and reference beams 622 and 670 will at least approximately accurately correspond to the shape of the transmission region 982, and as a result, the intensity of the far-field intensity pattern 672 detected by the detector 650 will be the maximum non-degraded intensity. However, due to the presence of noise in the output and reference beams 622 and 670, the orbit and shape of the far-field intensity pattern 672 deviate somewhat from the shape of the transmission region 982, and as a result, a portion of the reference beam 670 is incident on the opaque region of the mask 980 rather than on the transmission region 982, and thus does not transmit through the transmission region 982 to the detector 650. In such a case, the intensity of the far-field intensity pattern 672 detected by the detector 650 is lower than the maximum intensity that would be detected in the absence of noise.

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

[0356] The above-described arrangement of the detector 650 positioned behind the mask 980 makes it possible to use only a single detector 650 to sense the output intensity of the reference beam 670 along its beam orbit, and based on this, it is understood that the noise cancellation phase correction output can be applied. This is in contrast to alternative detector arrangements that do not include the mask 980, such as those described hereinabove with reference to FIGS. 6-8, for which multiple detectors may be used to provide sufficiently efficient and / or frequent noise correction during the dynamic change of the output beam 622.

[0357] In addition to changes in the intensity of the reference beam 670 measured by the detector 650 due to distortion of the beam trajectory caused by noise, the intensity of the reference beam 670 may typically change along the trajectory of the reference beam 670 due to inherent intensity changes in the far-field intensity pattern 672. This can complicate the noise correction feedback provided by the detector 650 because changes in the intensity of the reference beam 670 can be due to either noise or inherent intensity changes not related to noise.

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

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

[0360] It is understood that the various portions of the transmissive region 982 may have discretely different transparency values, or the transparency of the transmissive region 982 may change gradually according to the intensity compensation requirements of the far-field intensity pattern 672 across its various portions.

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

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

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

[0364] Next, referring to FIG. 11, FIG. 11 is a simplified schematic diagram of an optical phased array laser system including a detector mask configured according to an exemplary laser beam shape, constructed and operating according to another preferred embodiment of the present invention.

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

[0366] The transmission region 1182 may have a non-uniform transparency, and a very simplified representation thereof is shown in FIG. 12. As can be seen in FIG. 12, the first portion of the transmission region 1182 may have a first transparency T1, and the second portion of the transmission region 1182 may have a second transparency T2 different from the first transparency T1. As detailed herein with reference to FIG. 10, various levels of transparency of the transmissive region 1182 may be used to compensate for the inherent intensity variations of the output beam 670 and thus improve the noise correction output provided based on the intensity detected by the detector 650.

[0367] It is understood that the transmission regions 982 and 1182 of the masks 980 and 1180 may each additionally or alternatively be embodied as reflection regions that reflect the output reference beam 670 therefrom towards the detector 650. In such an arrangement, appropriate modifications and / or additions to a focusing subsystem, herein embodied as a focusing lens 990 by way of example, are required to direct the output reference beam 670 from the reflection regions 982, 1182 onto the surface of the detector 650. The reflection regions of the masks 980 and 1180 may have a uniform reflectivity. Alternatively, as described above herein, the reflection regions of the masks 980 and 1180 may have a non-uniform reflectivity to compensate for the inherent intensity variations in the output reference beam 670.

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

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

[0370] Next, refer to FIG. 13, which is a simplified schematic diagram of an optical phased array laser system including a voltage-phase correlation function, constructed and operating according to a preferred embodiment of the present invention.

[0371] As seen in FIG. 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, 400 described hereinabove with reference to FIGS. 1A - 4C. The OPA laser 1300 preferably comprises 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 a plurality of sub-beams along corresponding channels 1316.

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

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

[0374] The phase of the output beam 1322, and thus the position and shape of its far-field intensity pattern, are at least partially controlled by the relative phases of the constituent sub-beams combined to form the output beam 1322. In many applications such as laser cutting, laser welding, free-space optical communication, and laser additive manufacturing described above in this specification, it is desirable to dynamically move and shape the far-field intensity pattern of the output beam. As described above in this specification with reference to FIGS. 1A-4C, the dynamic alteration of the parameters of the output beam can be achieved by dynamically altering the relative phases of the individual sub-beams along the channel 1316, thereby altering the phase of the 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 pre-determined according to the desired laser output pattern. Particularly preferably, the relative phases to be altered are applied by the 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. The phase modulation control module 1330, in combination with the phase modulator 1318, forms a particularly preferred embodiment of the phase modulation subsystem 1332, which is preferably understood to operate to alter the phase of the combined laser output 1322.

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

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

[0378] The detector 1350 preferably samples the far-field intensity pattern 1372 incident thereon. Although the detector 1350 is shown in FIG. 13 as being embodied as a single detector that directly receives the far-field intensity pattern 1372, it is understood that a plurality of detectors may alternatively be used according to any of the plurality of detector arrangements shown in FIGS. 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 FIGS. 9 - 12.

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

[0380] In the operation of the phase modulation subsystem 1332, the phase modulation control module 1330 preferably applies a voltage to each of the phase modulators 1318, and as a result, generates a phase modulation output corresponding to the applied voltage. It is understood that the phase modulation control module 1330 must accurately apply a voltage corresponding to the specific phase modulation output that needs to be generated by each phase modulator 1318 in order for the phase modulator 1318 to generate the phase shift necessary to dynamically shape the far-field intensity pattern 1366 according to a predetermined pattern.

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

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

[0383] Including a correlation and calibration subsystem such as the voltage-to-phase correlation subsystem 1380 in the OPA laser 1300 is highly advantageous as it ensures that the voltage applied to the phase modulator 1318 is the voltage necessary to generate the desired phase shift of the output beam 1322 and, consequently, the shape of the far-field intensity pattern 1366. Considering that phase modulators suitable for use in the preferred embodiments of the present invention are typically sensitive devices and those different typically exhibit different voltage-phase relationships, this is particularly important. Furthermore, the voltage-phase relationship of individual phase modulators is not constant and may change over time depending on the operating conditions.

[0384] The phase modulation and calibration provided by the phase modulation control module 1330 and the voltage-to-phase correlation control module 1380 are not necessarily required respectively, but preferably are understood to be implemented in cooperation with the application of noise correction to the output of the OPA laser 1300 when the output of the laser 1300 has noise. In this case, the phase modulation control module 1330 and the voltage-to-phase correlation control module 1380 can be regarded as forming a particularly preferred embodiment of phase control subsystems such as the phase control subsystems 130 (FIG. 1A), 230 (FIG. 2A), 330 (FIG. 3A), and 430 (FIG. 4A) in combination.

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

[0386] As seen in the 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. Then, the far-field intensity pattern of the reference output beam 1372 is measured by the detector 1350 as seen in the second step 1404. Then, the required phase shift of the sub-beam is confirmed and the voltage is applied to the phase modulator 1318 again. The application of the voltage in the first step 1402 and the measurement of the reference output beam 1372 in the second step 1404 may be repeated a number of times periodically at a given repetition rate. By way of example only, the first and second steps may be repeated 20 times at a rate of one million times per second.

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

[0388] Then, in the fifth step 1410, the phase shift of the far-field intensity pattern 1372 is checked and it is confirmed whether the phase shift is zero. If the voltage applied in the third step 1406 is actually a voltage that generates a phase shift of 2π, it is understood that the phase shift of the beam 1322 will be zero and thus the intensity of the far-field intensity pattern 1372 will not change in response to the applied voltage. In this case, it can be seen that the phase modulator 1318 to which a phase shift of 2π was applied in the third step 1406 is correctly calibrated and no further calibration of the particular phase modulator 1318 is required.

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

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

[0391] It is understood that the frequency at which the voltage-to-phase correlation subsystem 1380 is activated is preferably much lower than the frequency at which the phase change of the output beam 1322 is performed. As an example, the phase change 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, flowchart 1400 does not include steps for noise correction, but it is understood that such noise correction can be applied in the process of phase shifting of the sub-beams contributing to the output beam 1322, as described hereinabove with reference to FIGS. 1A-4C.

[0393] Referring now to FIG. 15, FIG. 15 is a simplified schematic plan view of an optical phased array laser system that includes scaled phase correction of a dynamic beam, constructed and operating 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, and this OPA laser 1500 may have the type outlined herein with reference to FIGS. 1A-4C. The OPA laser 1500 preferably comprises 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 of FIG. 15. However, it is understood that the splitting and combining subsystem 1514 may include fewer or more channels into which the output of the seed laser 1512 is split, and typically may 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 channels 1516. Each phase-modulated sub-beam generated by splitting the output of the seed laser 1512 and subsequent phase modulation preferably propagates towards a collimating lens 1519. The individually collimated and phase-modulated sub-beams are then combined, for example, at the focal plane of a lens 1520 to form an output beam 1522.

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

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

[0398] In the case of the OPA laser 1500 that includes a plurality of individual sub - beams, the phase measurement and corresponding phase correction of each sub - beam with respect to the phases of all other sub - beams of the sub - beams 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 required to measure and correct the phase of each individual sub - beam with respect to the other sub - beams in order to dynamically control the phase of the combined laser output 1522 can be unacceptably long. Further, the signal - to - noise ratio can be unacceptably low.

[0399] It is a specific feature of a preferred embodiment of the present invention that the OPA laser 1500 includes a phase - modulation subsystem 1530 for performing phase - modulation of the combined laser output in an extended 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, within each group of sub - beams, performs phase - modulation only with respect to the other sub - beams within the group. Such group phase - modulation is preferably performed in parallel across the various individual groups of sub - beams. Then, the phase - modulation subsystem 1530 preferably optimizes the phase of each group of sub - beams with respect to the phases of the other groups of sub - beams in order to change the phase of the combined laser output 1522 in a manner detailed below.

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

[0401] To facilitate the application of phase changes to the output beam 1522, a portion of the output of the OPA laser 1500 is preferably extracted and directed towards a plurality of detectors 1550. The extracted portion of the output beam preferably functions as a reference beam based on characteristics from which the necessary phase changes can be calculated. In the embodiment shown in FIG. 15, a plurality of sub-beams along channel 1516 are directed towards a beam splitter 1560. The beam splitter 1560 preferably divides each sub-beam into a transmitted portion 1562 and a reflected portion 1564 according to a predetermined ratio. For example, the beam splitter 1560 can divide each sub-beam with a transmittance of 99.9%: a reflectance of 0.01%.

[0402] The transmitted portion 1562 of the sub-beam preferably propagates towards the focusing lens 1520, where the sub-beams are combined to form an output beam 1522 having a far-field intensity pattern 1566. The reflected portion 1564 of the sub-beam preferably propagates towards the cylindrical lens 1568. The cylindrical lens 1568 preferably operates to receive the reflected portion 1564 of the sub-beam and group the sub-beams into a number of groups by focusing the sub-beams along the curvature direction of the lens 1568. Here, by way of example, the sub-beams are shown converging into four groups 1570, with each group 1570 being composed of four sub-beams.

[0403] Preferably, each group 1570 of sub-beams grouped by the cylindrical lens 1568 forms a beam having a far-field intensity pattern 1572 incident on the surface of the corresponding detector among the plurality of detectors 1550. Each detector 1550 preferably samples the group far-field intensity pattern 1572 incident thereon. Each detector 1550 then preferably cooperates with the corresponding control electronics sub-module 1574 included in the control module 1532 to then optimize the relative phase of the sub-beams within the group of sub-beams 1570 sampled thereby with respect 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 among 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 group 1570 with respect to other groups of group 1570, a portion of group 1570 is preferably directed by auxiliary beam splitter 1580 to auxiliary cylindrical lens 1582. To focus the sub - beams, it is understood that the curvature of auxiliary cylindrical lens 1582 is preferably orthogonal to the curvature of cylindrical lens 1568. Auxiliary cylindrical lens 1582 preferably focuses the groups of sub - beams 1570 into a single beam 1584 having a far - field intensity pattern 1586 that impinges on auxiliary detector 1588. Auxiliary detector 1588 preferably receives a single beam having a far - field intensity pattern 1586 corresponding to the pattern of all combinations of groups of sub - beams 1570 there. Auxiliary detector 1588 preferably cooperates with an additional phase - control electronics sub - module 1590 included in electronic control module 1532 to sample and optimize the phases of group 1570 relative to each other. Particularly preferably, one function of phase - control electronics module 1532 is to control each phase modulator 1518 to apply a phase shift that maximizes the total power of auxiliary detector 1588.

[0405] It is understood that performing phase modulation in the extended method described above, where the phase of each sub - beam is optimized with respect to the phases of the members of the other sub - beams of its group 1570 and the phases of group 1570 are optimized relative to each other to change the phase of the combined laser output 1522, is much faster and less complex than optimizing the phase of each individual sub - beam with respect to the phases of all the other sub - beams in OPA1500. Further, this enables the phase optimization to be performed by individual sets of control electronics within each control - electronics sub - module 1574 connected respectively to each detector 1550, rather than requiring a single set of control electronics, and can improve the signal - to - noise ratio.

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

[0407] As seen in FIG. 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 FIG. 16, system 1500 includes 16 sub-beams, four of which are included in each of four groups 1570, and as a result, a total of four additional group phase modulators 1618 may be included in system 1500. Each group phase modulator 1618 preferably provides a phase shift that is common to and optimizes the collective group phase of the sub-beams along four channels 1516 that form part of each group 1570 and are connected thereto.

[0408] Preferably, the group phase modulators among group phase modulators 1618 are preferably controlled by an additional control sub-module 1690 included in control module 1532. Auxiliary detector 1588 is preferably coupled to additional control sub-module 1690. Optimizing the relative phases of groups 1570 with respect to one another by group phase modulators 1618 rather than by individual sub-beam phase modulators 1518 is more efficient and can simplify the phase modulation process, but requires the use of additional phase modulators and circuit elements and thus increases the cost and complexity of system 1500.

[0409] The change in the phase of the combined laser output 1522 preferably provides a spatial modulation of the output 1522. Due to the extended nature of the phase modulation performed by the phase modulation subsystem 1530, it is understood that the phase of the combined laser output 1522 can be changed 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 enhanced by additional mechanical spatial modulation mechanisms, or may not include mechanical spatial modulation, as is known in the art.

[0410] It is understood that the specific structure and configuration of the optical elements shown herein, including the beam splitter 1560, the focusing lens 1520, the cylindrical lens 1568, the auxiliary beam splitter 1580, and the auxiliary cylindrical lens 1582, are merely illustrative and are shown in a very simplified form. The OPA laser system 1500 may include additional optical elements, including various such elements, and by way of example only, additional or alternative lenses, optical fibers, and coherent free space far-field combiners.

[0411] Furthermore, it is understood that the cylindrical lens 1568 may have optical properties such that it groups the individual sub-beams into groups that are similar or identical to each other and contain an equal number of sub-beams. Alternatively, the cylindrical lens 1568 may have optical properties such that it groups the individual sub-beams into groups that are different from each other and contain different numbers of sub-beams.

[0412] An exemplary implementation of an OPA laser system of the type shown in FIG. 15 or FIG. 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 a plurality of sub-beams along a corresponding plurality of channels 1716. By way of example, the laser output can be split into a 10×10 matrix of 100 sub-beams along 100 corresponding channels 1716. For clarity of presentation, it is understood that only selected sub-beams of the sub-beams are shown in FIG. 17B. The sub-beams along channels 1716 can then be collimated and focused by collimating and focusing elements (not shown), such as collimating and focusing lenses 1519, 1520, to produce a combined output beam.

[0413] To facilitate the application of a phase change to the output beam, a portion of the output of OPA laser 1700 is preferably extracted and directed towards a plurality of detectors 1750. The extracted portion of the output beam preferably functions as a reference beam based on characteristics from which the necessary phase change can be calculated. In the embodiments shown in FIGS. 17A and 17B, the plurality of sub-beams along channels 1716 are directed towards 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 transmissive portion 1762 of the sub-beams is preferably combined to form an output beam. The reflective portion 1764 of the sub-beams is preferably reflected towards the cylindrical lens 1768, which is a particularly preferred embodiment of the cylindrical lens 1568. The cylindrical lens 1768 preferably receives the reflective portion 1764 of the sub-beams and operates to focus the sub-beams into a number of groups along the curvature direction of the cylindrical lens 1768. As an example, in the case of 100 sub-beams, the cylindrical lens 1768 can focus the sub-beams into 10 groups 1770 of 10 sub-beams each.

[0415] Preferably, each group 1770 of sub-beams grouped by the cylindrical lens 1768 forms a beam having a far-field intensity pattern that impinges on the surface of the corresponding detector among the plurality of detectors 1750. As an example, the plurality of detectors 1750 may include 10 detectors 1750, each sampling a group beam including 10 individual sub-beams. Each detector 1750 cooperates with a corresponding control electronics module (not shown), such as the control module 1532, and then preferably optimizes the phase of the sub-beams included in the group 1770 of sub-beams sampled thereby. Such sampling and optimization are preferably performed in parallel, preferably simultaneously, across all of the detectors 1750.

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

[0417] The auxiliary detector 1788 preferably receives a far-field intensity pattern corresponding to the pattern of all combinations of groups of sub-beams 1770 and, in cooperation with a phase control device (not shown), samples and optimizes the phases of the groups 1770 relative to each other. The optimization of the phases of the groups 1770 relative to each other can be by phase modulation of the phases of the individual sub-beams by the phase modulator 1518, as described hereinabove with reference to FIG. 15, or by phase modulation of the phases of the groups of sub-beams by the group phase modulator 1618, as described hereinabove with reference to FIG. 16.

[0418] Referring now to FIG. 18, FIG. 18 is a simplified schematic plan view of an optical phased array laser system including a scaled phase correction of a dynamic beam, constructed and operating 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, and this OPA laser 1800 may have the type outlined herein with reference to FIGS. 1A - 4C. The OPA laser 800 preferably comprises 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 corresponding plural 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 is understood that the splitting and combining subsystem 1814 may include fewer or more channels into which the output of the seed laser 1812 is split, and typically may 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 the channels 1816. Each phase-modulated sub-beam generated by splitting the output of the seed laser 402 and subsequent phase modulation preferably propagates towards the collimating lens 1819. The individually collimated and phase-modulated sub-beams are then combined, for example, at the focal plane of the lens 1820 to form the output beam 1822.

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

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

[0423] In the case of the OPA laser 1800 that includes a plurality of individual sub-beams, the phase measurement and corresponding phase correction of each sub-beam with respect to the phases of all other sub-beams of the sub-beams 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 required to measure and correct the phase of each individual sub-beam with respect to the other sub-beams to dynamically control the phase of the combined laser output 1822 can be unacceptably long. Further, the signal-to-noise ratio can be unacceptably low.

[0424] It is a specific feature of a preferred embodiment 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 extended 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, within each group of sub-beams, performs phase modulation only with respect to the phases of the other sub-beams within the group. Such group phase modulation is preferably performed in parallel across the various individual groups. Next, the phase modulation subsystem 1830 preferably optimizes the phase of each group of sub-beams with respect to the phases of the other groups of sub-beams to change the phase of the combined laser output 1822 in a manner detailed below.

[0425] The phase modulation subsystem 1830 preferably includes a phase control electronic module 1832 in the operation control of the phase modulator 1818. The phase control electronic module 1832 preferably controls each phase modulator 1818 to dynamically modulate the relative phase of the sub-beams along the channel 1816 in accordance with the desired far-field intensity pattern of the output beam 1822 as identified by the phase modulation subsystem 1830.

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

[0427] The transmitted portion 1862 of the sub-beam preferably propagates towards the focusing lens 1820, where the sub-beams are combined to form an output beam 1822 having a far-field intensity pattern 1866. The reflected portion 1864 of the sub-beam is preferably reflected towards an array of mirrors 1868, and each mirror 1868 is positioned in a spaced relationship with respect to a corresponding focusing lens 1869. As an example, the mirror array 1868 may comprise four mirrors 1868 positioned in a spaced relationship with respect to four focusing lenses 1869, two of which are visible in the top view of the system 1800 of FIG. 18.

[0428] The mirror 1868 is preferably angled to reflect the incident sub-beam towards the corresponding focusing lens 1869, thereby operating to group the reflected portion 1864 of the sub-beam into a number of groups, which are embodied herein as four groups 1870, each group 1870 including four sub-beams, two of which are visible in the top view of the system 18100 of FIG. 18.

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

[0430] To optimize the relative phase of each of the groups 1870 with respect to other groups of the group 1870, a portion of the reflective portion 1864 is preferably directed to an auxiliary lens 1882 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 impinges on an auxiliary detector 1888. The auxiliary detector 1888 preferably receives, therein, a single beam having a far-field intensity pattern 1886 corresponding to the pattern of all combinations of groups of sub-beams 1870. The auxiliary detector 1888 preferably samples and optimizes the phases of the groups 1870 with respect to each other in cooperation with a phase control electronics sub-module 1890 included in the electronic control module 1832. 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] The phase of each sub-beam is optimized relative to the phases of the members of the other sub-beams of its group 1870, and the phases of the groups 1870 are optimized relative to each other to change the phase of the combined laser output 1822. Performing phase modulation in the extended method described above is understood to be much faster and less complex than optimizing the phase of each individual sub-beam relative to the phases of all the other sub-beams in OP1800. Further, this enables phase optimization to be performed by the individual sets of control electronics within each control electronics sub-module 1874 connected to each detector 1850, rather than requiring a single set of control electronics, and can improve the signal-to-noise ratio.

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

[0433] As seen in FIG. 19, system 1800 may be modified by adding a series of group phase modulators corresponding to the number of groups 1870. Here, as an example, as seen in FIG. 19, system 1800 comprises 16 sub-beams, four of which are included in each of the four groups 1870, and as a result, a total of four additional group phase modulators 1918 may be 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 among the group phase modulators 1918 are preferably controlled by an additional control sub-module 1990 included in the control module 1832. The auxiliary detector 1888 is preferably connected to the additional control sub-module 1990. Optimizing the relative phases of the groups 1870 with respect to each other by the group phase modulators 1918 rather than by the individual sub-beam phase modulators 1818 is more efficient and can simplify the phase modulation process, but requires the use of additional phase modulators and circuit elements and thus is understood to increase the cost and complexity of the system 1800.

[0435] Changing the phase of the combined laser output 1822 preferably provides spatial modulation of the output 1822. Due to the extended nature of the phase modulation performed by the phase modulation subsystem 1830, it is understood that the phase of the combined laser output 1822 can be changed 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 enhanced by additional mechanical spatial modulation mechanisms or may not include mechanical spatial modulation, as is known in the art.

[0436] The specific structure and configuration of the optical elements shown herein, including the beam splitter 1860, the focusing lens 1820, the mirror array 1868, and the corresponding focusing lens 1869, are merely illustrative and are shown in a very simplified form. It is understood that the OPA laser system 1800 may include additional optical elements, including various such elements and, by way of example only, additional or alternative lenses, optical fibers, and coherent free space far-field combiners.

[0437] Furthermore, it is understood that the mirror 1868 and the corresponding focusing lens 1869 may have mutually similar or identical optical properties so as to group the individual sub-beams into mutually similar or identical groups each containing an equal number of sub-beams. Alternatively, the mirror 1868 and the corresponding focusing lens 1869 may have mutually different optical properties so as to group the individual sub-beams into mutually different groups each containing a different number of sub-beams.

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

[0439] To facilitate the application of a phase change to the output beam, a portion of the output of the OPA laser 2000 is preferably extracted and directed towards a plurality of detectors 2050. The extracted portion of the output beam preferably functions as a reference beam based on properties from which the necessary phase change can be calculated. In the embodiments shown in FIGS. 20A and 20B, the plurality of sub-beams along the channels 2016 are directed towards a beam splitter 2060. The 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 transmissive portion 2062 of the sub-beams preferably combines to form an output beam. The reflective portion 2064 of the sub-beams is preferably reflected towards the array of mirrors 2068, and each mirror 2068 is positioned in a spaced relationship with respect to the corresponding focusing lens 2069. It is understood that the mirror array 2068 and the lenses 2069 are a particularly preferred embodiment of the mirror array 1868 and the focusing lenses 1869.

[0441] The mirror 2068 is preferably angled to reflect the incident sub-beam towards the corresponding focusing lens 2069, thereby operating to group the reflective portion 2064 of the sub-beams into a number of groups, which are embodied as four groups by way of example here, and each group 2070 includes 25 sub-beams. Preferably, each set of sub-beams reflected by each of the mirrors 2068 is focused by the 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 the surface of the corresponding detector among the plurality of 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 the control electronics sub-module 1874 included in the control module 1832, and then preferably optimizes the phase of the sub-beams included in the group of sub-beams 2070 sampled thereby so that the combined phase generates the desired group far-field intensity pattern. Such sampling and optimization are preferably performed in parallel, preferably simultaneously, for the far-field intensity pattern among the far-field intensity patterns across all the detectors 2050.

[0442] To optimize the respective relative phases of group 2070 with respect to other groups of group 2070, a portion of reflective portion 2064 is preferably directed by auxiliary beam splitter 2080 to auxiliary lens 2082. Auxiliary lens 2082 preferably focuses a portion of reflective portion 2064 into a single beam 2084 that impinges on auxiliary detector 2088. Auxiliary detector 2088 preferably receives at that location a single beam having a far-field intensity pattern corresponding to the pattern of all combinations of sub-beams. Auxiliary detector 2088 preferably cooperates with phase control electronics included in electronic control module 1832 to sample and optimize the phases of groups 2070 relative to each other.

[0443] Optimization of the phases of groups 2070 relative to each other can be by phase modulation of the phases of the individual sub-beams by phase modulator 1818, as described hereinabove with reference to FIG. 18, or by phase modulation of the phases of groups of sub-beams by group phase modulator 1918, as described hereinabove with reference to FIG. 19. It is understood that this can be the case.

[0444] In the above-described embodiments of the OPA lasers 1500, 1700, 1800, and 2000 of FIGS. 15-20B, phase modulation is preferably performed in an extended manner using a plurality of detectors such as detectors 1550, 1750, 1850, 2050, etc. that are used to simultaneously perform phase measurements of sub-beams within a plurality of groups, and a single detector such as auxiliary detectors 1586, 1786, 1886, 2086 that are used to perform phase measurements of a single beam including a plurality of groups. It is understood that this is the case.

[0445] However, it is understood that a system constructed and operating in accordance with a preferred embodiment of the present invention can be further extensible to include still additional tiers of detectors and corresponding optical elements, depending on the number of sub-beams involved.

[0446] As an example, as shown in FIG. 21, the OPA laser system 1500 may be further modified to include an additional focusing lens 2102 for focusing a group 1570 of the sub-beams into an intermediate group 2104 where the intermediate group is incident on an intermediate detector 2106. Then, the intermediate groups 2104 are further combined and incident on a single detector 2108, where it is preferable that the intermediate groups 2104 in the single detector 2108 are phase-modified with respect to each other.

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

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

[0449] Next, referring to FIGS. 22A and 22B, these are simplified schematic diagrams of the first and second focal states, respectively, of an optical phased array laser system constructed and operating in accordance with a preferred embodiment of the present invention.

[0450] As shown in FIGS. 22A and 22B, preferably, a laser system 2200 including an optical phased array (OPA) laser 2202 is provided. The OPA laser system 2200 may have the type outlined in U.S. Patent No. 9,584,224 or U.S. Patent Application No. 15 / 406,032, which is assigned to the same assignee as the present invention and the content of which is incorporated herein by reference. Alternatively, the OPA laser system 2200 may be a laser system of the type described with reference to any one or a combination of FIGS. 1A-21 above of this specification.

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

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

[0453] The splitting and combining subsystem 2214 may also preferably provide laser amplification of the sub-beams after splitting the output beam of the seed laser 2212 and prior to combining the sub-beams to form the output beam 2222. Here, by way of example, the splitting and combining subsystem 2214 is shown as including a plurality of optical amplifiers 2224 for amplifying each sub-beam. However, it is understood that such amplification is selectable depending on the power output usage of the OPA laser 2200 and may be omitted.

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

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

[0456] Due to the noise inherent in the OPA system 2200, the output beam 2222 may have noise. The noise in the output beam 2222 is typically phase noise generated by thermal or mechanical effects and / or by the amplification process when the optical amplifier 2224 is within the OPA system 2200. If the output beam 2222 has noise, the OPA system 2200 may include a noise cancellation subsystem 2240 that operates to provide a noise cancellation phase correction output to cancel the noise in the output beam 2222 in a manner detailed below.

[0457] Particularly preferably, the noise cancellation subsystem 2240, while not necessarily required, preferably uses an algorithm that detects and corrects phase noise in the combined laser output of the type described herein with reference to FIGS. 1A-4C. The noise cancellation phase correction output is preferably provided by the noise cancellation subsystem 2240 to the phase modulator 2218 to correct the phase noise of the output beam 2222 and thus avoid distortion of the shape and position of the far-field intensity pattern of the output beam 2222 that would otherwise be caused by noise. The noise cancellation subsystem 2240 may be included in the control electronics module 2232.

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

[0459] To facilitate the application of phase changes and noise corrections in the case of the output beam 2222, a portion of the output of the OPA laser 2202 is preferably extracted and directed towards at least one detector 2250. Here, by way of example, at least one detector 2250 is shown as being embodied as a single detector 2250. However, it is understood that at least one detector 2250 may be embodied as a plurality of detectors that receive a portion of the output of the OPA laser 2202 via closely spaced optical paths, as described herein with reference to FIGS. 6-8, or as at least one detector that receives a portion of the output of the OPA laser 2202 via a transmissive or reflective optical mask, as described herein with reference to FIGS. 9-12. The extracted portion of the output beam preferably functions as a reference beam based on characteristics from which the necessary noise correction and / or phase change can be calculated.

[0460] According to a preferred embodiment of the present invention, a plurality of sub-beams along channel 2216 are directed towards beam splitter 2260. The beam splitter 2260 preferably splits each sub-beam into a transmission portion 2262 and a reflection portion 2264 according to a predetermined ratio. For example, the beam splitter 2260 can split each sub-beam with a transmittance of 99.9%: a reflectance of 0.01%.

[0461] The transmission portion 2262 of the sub-beam preferably propagates towards the focusing lens 2220, where the sub-beams are combined to form an output beam 2222 having a far-field intensity pattern 2266 at the focusing lens 2220. The reflection portion 2264 of the sub-beam is preferably reflected towards an additional focusing lens 2268, where the sub-beams are combined to form an output reference beam 2270 having a far-field intensity pattern 2272 that is incident on one or more surfaces of the plurality of detectors 2250.

[0462] In a particular application, the output beam 2222 is preferably directed towards a substrate 2280 on which the far-field intensity pattern 2266 of the output beam 2222 preferably impinges. The substrate 2280 may be a workpiece being processed by the OPA laser 2202. For example, the OPA laser 2202 may operate to additionally manufacture, cut, weld, sinter, or otherwise process the workpiece 2280. The phase control subsystem 2230 preferably changes the phase of the output beam 2222 to focus the output beam 2222 onto the substrate 2280. It is understood that without the application of such a phase change by the phase control subsystem 2230, the output beam 2222 will not be focused onto the substrate 2280.

[0463] A specific feature of a preferred embodiment of the present invention is that the focusing lens 2220 is designed such that the output beam 2222 of the OPA laser 2202, when no phase change is applied, is not focused by the lens 2220 onto the surface of the substrate 2280. By way of example, as can be understood from consideration of FIG. 22A showing the configuration of the output beam 2222 when no phase change is applied, the focusing lens 2220 may be optically designed to focus the non-phase change collimated wavefront 2282 including the output beam 2222 onto the focal point 2284 on the surface of the substrate 2280.

[0464] As can be understood from consideration of FIG. 22B showing the configuration of the output beam 2222 when a phase change is applied to the output beam 2222, the phase change of the output beam 2222 preferably serves to modify the shape of the wavefront 2282, and thus the focus, as seen in the case of a typical phase correction wavefront 2286, and this phase correction wavefront 2286 is preferably focused onto the substrate 2280 via the focusing lens 2220. Thus, it is understood that the focusing of the output beam 2222 on the substrate 2280 is achieved not only by the focusing lens 2220 but also by its phase change in combination with the focusing lens 2220, as shown in FIG. 22B.

[0465] As a result of the focusing of the output beam 2222 on the substrate 2280 being achieved by its phase change, the backscattering originating from the substrate 2280 is, accordingly, not focused by the focusing lens 2220 onto the OPA laser 2202. As is well known in the art, backscattering from a surface processed by a laser beam typically returns to the laser and can damage the laser, especially in a laser amplification system. In the present invention, the focusing lens 2220 does not focus the backscattering towards the OPA laser 2202, and thus such damage is avoided because the backscattering does not reach and damage the OPA laser 2202.

[0466] An exemplary return path of backscattering from substrate 2280 towards OPA laser 2202 is shown in FIG. 23. As seen in FIG. 23, the backscattered laser beam 2300 emitted from substrate 2280 preferably reaches the focusing lens 2220. However, the backscattered laser beam 2300 is preferably not focused by the focusing lens 2220 onto the OPA laser 2202, thereby preventing damage to them. If the focusing lens 2220 is designed to focus the non-phase-corrected laser output from the OPA laser 2202 onto the substrate 2280 as in a typical case in a conventional laser system, the path of the backscattered beam 2300 will accordingly be focused by the focusing lens 2220 onto the OPA laser 2202, and thus it is understood that it may cause damage to the focusing lens 2220.

[0467] In a particular embodiment of the present invention, it is understood that the focusing of the output of the OPA laser 2202 on the substrate 2280 can be achieved only by appropriate phase modification of the output beam 2222 such that the focusing lens 2220 becomes unnecessary.

[0468] As described above herein with reference to FIGS. 1A - 23, the output from the seed laser may be directed to an amplification system for its amplification. As is well known to those skilled in the art, defects in the laser output by the seed laser powering the amplification system can potentially cause damage to the amplification system. Typical defects in the laser output by the seed laser that cause damage to the amplification system connected to the seed laser include a decrease in the power of the seed laser output and degradation of the laser linewidth. The resulting damage to the amplification system can occur very rapidly, within about a few nanoseconds, before the response time of the internal detection mechanism that may be included in the amplification system.

[0469] A preferred embodiment of the present invention for preventing damage to an amplification system when there is a failure in a connected seed laser will now be described with reference to FIGS. 24 to 33. The seed laser failure protection system described below can be incorporated into any OPA laser of the type described hereinabove with reference to FIGS. 1A to 23, and it is understood that it can be incorporated into any other laser system including a seed laser and an amplifier connected thereto.

[0470] Next, referring to FIG. 24, as seen in FIG. 24, a laser system 2400 is preferably provided that 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, and the laser system 2400 that receives the laser output from the seed laser 2402 and amplifies the laser output to provide an amplified laser output 2406 may, by way of example, be embodied as a master oscillator power amplifier (MOPA) laser, or it may be any other laser system including 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 during the laser output of the seed laser 2402, the system 2400 preferably further includes a detector subsystem that is preferably embodied as a seed sensor 2420 and receives the output from the seed sensor 2402. The laser output from the seed laser 2402 preferably reaches the detector subsystem 2420 via a second optical path 2422. The detector subsystem 2420 may include one or more sensors for sensing characteristics during the laser output, and more specifically for detecting possible obstacles during the laser output. The sensor subsystem 2420 is preferably operably coupled to the power amplifier 2404. The sensor subsystem 2420 is preferably configured to deactivate the power amplifier 2404 when detecting an obstacle in the laser output from the seed laser 2402.

[0472] A specific feature of a preferred embodiment 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 required 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 an obstacle in the received laser output and deactivates the power amplifier 2404, after which the power amplifier 2404 receives a defective laser output, thereby preventing damage to the power amplifier 2404.

[0474] The extension of the flight time of the laser output from the seed laser 2402 to the power amplifier 2404 enables, in the embodiment of the present invention shown in FIG. 24, the sensor 2420 to detect a failure of the laser output and, if necessary, deactivate the power amplifier 2404 before receiving a defective laser output by the power amplifier 2404. This is achieved by including a fiber coil 2410 along the first optical path. As an example, the fiber coil 2410 may have a physical length of 10 km, and the flight time of the laser output along it may be about 50 microseconds. Thus, if a failure occurs in the output from the seed laser 2402, the power amplifier 2404 continues to receive a non-failed input signal for 50 microseconds after the start of the failed output signal from the seed laser 2402.

[0475] The optical path between the seed laser 2402 and the sensor subsystem 2420 may not include the coil 2410 and may be a direct and thus much shorter optical path. Thus, the flight time 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. Thus, after a failure occurs in the output from the seed laser 2402, the sensor subsystem 2420 can thus quickly receive the laser output, detect a failure 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, before the power amplifier 2404 receives a failure signal detected by the sensor subsystem 2420, the power amplifier 2404 is preferably switched off by the sensor subsystem 2420, thereby preventing damage to the power amplifier 2404.

[0476] The extension of the optical path between the seed laser 2402 and the power amplifier 2404, and thus the increase in the flight time along there, is not limited to being achieved by a method including a fiber coil along the optical path between the seed laser 2402 and the power amplifier 2404 as compared to the time and length of the optical path between the seed laser 2402 and the sensor subsystem 2420. Rather, the optical path between the seed laser 2402 and the power amplifier 2404 may be extended by any suitable means, including, for example, including an optical delay line 2500 along there as shown in FIG. 25. Further, 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 flight time along there may be extended by the use of optical elements such as reflecting mirrors. However, it is understood that including the coiled fiber 2410 in the first optical path 2408 may be particularly advantageous due to its compact configuration and due to the maintenance of the optical mode of the seed laser output by the coiled fiber 2410.

[0477] It is understood that the specific configuration of the coiled fiber 2410 shown in FIG. 24 is merely representative and exemplary. The coiled fiber 2410 may be embodied in any suitable form and may be adapted so that the laser output moves in one direction or back and forth along the optical path in order to further increase the effective length of the optical path provided by the coiled fiber 2410.

[0478] Referring now to FIG. 27, FIG. 27 is a simplified schematic diagram of a laser amplification system including a seed laser fault protection system constructed and operating in accordance with yet another preferred embodiment of the present invention.

[0479] As shown in FIG. 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 embodied herein as a power amplifier 2704 by way of example, and provides an amplified laser output 2706. The laser system 2700 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.

[0480] As is well known to those skilled in the art and as detailed above herein, defects in the laser output by the seed laser 2702 can potentially cause damage to the power amplifier 2704. Typical defects in the laser output by the seed laser 2702 that cause damage to the power amplifier 2704 can include a stoppage or decrease in the power of the seed laser output and a 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 the internal detection mechanism that may be included in the power amplifier 2704.

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

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

[0483] When the laser output of seed laser 2702 stops, due to malfunction of seed laser 2702, first amplifier 2703 stops receiving the laser output from seed laser 2702. In this case, first amplifier 2703 generates amplified spontaneous emission, and the amplified spontaneous emission is received by second amplifier 2704. Alternatively, first amplifier 2703 may be configured such that when the laser output from seed laser 2702 stops, first amplifier 2703 begins to operate as a laser and generates additional laser output.

[0484] Thus, it is understood that even when seed laser 2702 stops providing laser output, second amplifier 2704 continues to receive an input signal in the form of amplified spontaneous emission or in the form of 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, which damage might otherwise occur due to the cessation of signal provision to second amplifier 2704. It is understood that system 2700 additionally includes a sensor connected to seed laser 2702 that can detect an impairment of the laser output from seed laser 2702 and in response deactivate second amplifier 2704.

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

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

[0487] A particularly preferred embodiment of the linewidth filter 2800 suitable for use in the present invention is shown in FIG. 28.

[0488] Referring now to FIG. 28, the filter structure 2800 is seen to be implemented downstream of the seed laser 2702 and upstream of the first amplifier 2703. The laser output from the seed laser 2702 is preferably split into two parts by a splitter 2805 at the entrance to the filter 2800 and recombined by a recombiner 2806 before exiting the filter 2800. The first part of the split laser output from the seed laser 2702 preferably travels along the first arm 2807 of the filter 2800 between the splitter 2805 and the recombiner 2806. The second part of the split laser output from the seed laser 2702 preferably travels along the second arm 2808 of the filter 2800 between the splitter 2805 and the recombiner 2806. As can be understood 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 thus longer than the second arm 2808.

[0489] If the laser output from the seed laser 2702 has an unacceptably narrow linewidth, the laser outputs from the first and second arms 2807 and 2808 interfere with each other when recombined at the recombiner 2806 due to their relatively high coherence. The recombined beam is preferably detected by the detector 2810, which is preferably connected to the electronic control module 2811. The electronic control module 2811 preferably operates in controlling the operation of the phase modulator 2812 positioned along the second arm 2808 and is preferably a coherent beam combining (CBC) card. The phase modulator 2812 is preferably operated by the electronic control card 2811 to change the phase of the beam along the second arm 2808 such that substantially all of the recombined beam at the recombiner 2806 is directed towards the detector 2810. Thus, the recombined beam does not proceed towards the first amplifier 2703 and thus does not reach the second amplifier 2704 and cause damage to it. The receipt of the 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 above herein.

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

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

[0492] Referring now to FIG. 29, FIG. 29 is a simplified schematic diagram of a laser amplification system including a seed laser fault protection system constructed and operating in accordance with an even more preferred embodiment of the present invention.

[0493] As seen in FIG. 29, preferably, a laser system 2900 is provided that includes a seed laser 2902 that provides a first laser output 2903 and an amplification subsystem. Here, by way of example, the amplification subsystem is embodied as a power amplifier 2904, which receives the first laser output 2903 from the seed laser 2902 and amplifies the laser output to provide an amplified laser output 2906. The laser system 2900 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.

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

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

[0496] The auxiliary seed laser 2930 preferably provides the second laser output 2932 at least when the seed laser 2902 is stopped, to provide the first laser output 2903 to the amplifier 2904. Particularly preferably, the auxiliary seed laser 2930 preferably operates continuously so as to provide the second laser output 2932 to the amplifier 2904 both when the seed laser 2902 provides the first laser output 2903 to the amplifier 2904 and simultaneously when the seed laser 2902 stops providing the first laser output 2903.

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

[0498] When the laser output from the seed laser 2902 stops, due to a malfunction of the seed laser 2902 detected by the sensor subsystem 2920, the sensor subsystem 2920 preferably operates to deactivate the amplifier 2904. Due to the finite response times of the amplifier 2904 and the detector subsystem 2920, the amplifier 2904 is not instantaneously deactivated and continues to operate for a limited time period after the laser output from the seed laser 2902 stops. During this time, it is understood that the amplifier 2904 no longer receives the first laser output 2903 from the seed laser 2902. However, the auxiliary seed laser 2930 preferably continues to provide the second laser output 2932 to the amplifier 2904. Thus, it is understood that the amplifier 2904 continues to receive an input signal in the form of the second laser output 2932 even when the seed laser 2902 stops providing 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 is likely to occur due to a stoppage of signal supply, before the amplifier 2904 is deactivated by the sensor 2920.

[0499] Next, referring to FIG. 30, FIG. 30 is a simplified schematic diagram of a laser amplification system including a seed laser fault protection system constructed and operating in accordance with yet another preferred embodiment of the present invention.

[0500] As seen in FIG. 30, preferably, a laser system 3000 is provided that includes a seed laser 3002 that provides a first laser output 3003 and an amplification subsystem, which is embodied herein as a power amplifier 3004 by way of example, that receives the first laser output 3003 from the seed laser 3002 and amplifies the laser output to provide an amplified laser output 3006. The 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 impairments 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 when detecting an impairment in the laser output from the seed laser 3002.

[0502] A particular feature of a preferred embodiment of the present invention is that the 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 inlet 3034 of the amplifier 3004 and a second reflective grating 3036 preferably positioned at the outlet 3038 of the amplifier 3004. The pair of gratings 3030 in combination with the amplifier 3004 preferably forms a preferred embodiment of the auxiliary laser subsystem 3040.

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

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

[0505] Particularly preferably, although not necessarily, the pair of gratings 3030 is reflective at a wavelength different from the wavelength of the first laser output 3003 of the seed laser 3002, and during proper operation of the seed laser 3002, the gratings 3030 have a negligible effect on the amplified output 3006. Merely by way of example, the first laser output 3003 can have a wavelength in the range of 1060 - 1070 nm, but the gratings 3030 can be reflective at a wavelength in the range of 1090 - 1100 nm.

[0506] Thus, it is understood that even when the seed laser 3002 stops providing laser output, the amplifier 3004 continues to receive an input signal in the form of signal feedback from the grating 3030. As a result, the amplifier 3004 in combination with the grating 3030 begins to operate as a laser when the operation of the seed laser 3002 stops, thereby preventing damage to the amplifier 3004 that might otherwise occur due to the cessation of the provision of a signal to the amplifier.

[0507] As can be seen in FIGS. 29 and 30, the laser outputs from the seed lasers 2902, 3002 may be directly supplied to the amplifiers 2904, 3004 respectively. Alternatively, as shown in FIGS. 31 and 32, additional elements can be inserted to interface the seed lasers and the amplifiers. 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 out laser beams with an unacceptably narrow linewidth and prevent such laser beams from reaching the amplifiers 2904, 3004 and thus damaging them.

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

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

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

[0511] When the output from the seed laser degrades to an unacceptably narrow linewidth, non-linear effects will be initiated in fiber 3344. It is understood that fiber 3344 is advantageously configured to be as sensitive as possible to such non-linear effects. For this purpose, to increase the sensitivity of fiber 3344 to the linewidth of the laser output from the seed laser, fiber 3344 preferably has a fairly long length and preferably 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] When the linewidth of the output from the seed laser is narrowed, due to the non-linear effect starting in fiber 3344, fiber 3344 begins to act as a mirror and reflects the light backward toward amplifier 3340. As a result of the reflected light returning to amplifier 3340, the increased signal reaches splitter 3334 and is detected by detector 3336. When the increased signal is detected by detector 3336, the power amplifier is preferably deactivated to prevent damage to the power amplifier.

[0513] Those skilled in the art will understand that the present invention is not limited by what is particularly claimed below. Rather, the scope of the present invention includes various combinations and sub-combinations of the features described above in this specification, as well as their modifications and variations, which would occur to those skilled in the art upon reading the foregoing description with reference to the drawings, and which are not present in the prior art.

Claims

1. 1. A laser system comprising a coherent beam combining (CBC) laser, at least one detector, and a phase control system, the CBC laser is operative to provide a laser output having at least thermal noise, the CBC laser including at least one optical element positioned along a path of the laser output; the at least one detector is positioned downstream of the at least one optical element, the at least one detector operative to receive at least a portion of the laser output and detect the at least thermal noise; The phase control system operates as follows: a first phase modification that modifies a phase of the laser output to control at least one of a shape and a position of the laser output; and a second phase change that cancels the at least thermal noise detected by the detector, the second phase change being performed without disturbing the control; configured to provide The at least one detector is operative to detect the thermal noise at discrete times while controlling the laser power. Laser system.

2. 10. The laser system of claim 1, wherein said first phase change for controlling said laser output is applied during a time interval between said intermittent times.

3. 10. The laser system of claim 1, wherein the first phase change for controlling the laser output is applied at a faster rate than the second phase change for canceling the thermal noise.

4. 10. The laser system of claim 1 , wherein the at least one optical element comprises at least one lens.

5. 10. The laser system of claim 1, wherein the thermal noise comprises phase noise generated by thermal effects on the laser system.

6. 10. The laser system of claim 1, wherein the laser output has noise due to mechanical and / or amplification effects.

7. The laser system of claim 1 , wherein the at least one detector comprises a plurality of detectors.

8. 10. The laser system of claim 1 , wherein said phase control system operates to control said laser output using digital electronic control without the need for moving parts.

9. 1. A method for correcting noise in a laser output, comprising: providing a laser output having at least thermal noise with a coherent beam combining (CBC) laser, the CBC laser comprising at least one optical element positioned along a path of the laser output; receiving at least a portion of the laser output with at least one detector positioned downstream of the at least one optical element, the at least one detector detecting the at least thermal noise; a first phase-varying step of controlling at least one of a shape and a position of the laser output by varying a phase of the laser output; a step of second phase modification of the laser output to cancel the at least thermal noise detected by the detector, the second phase modification being performed without disturbing the control during the control; Including, The at least one detector is operative to detect the thermal noise at discrete times while controlling the laser power. method.

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