Laser beam method and system

Abstract

This application relates to laser beam methods and systems. Methods and apparatus for manipulating and modulating laser beams are also provided. These methods and apparatus enable the activation and deactivation of a laser beam while the laser system maintains its operating power. Furthermore, a hybrid pump module is provided, configured to be coupled to an optical fiber having a core and at least one cladding. The hybrid pump module includes: at least one focusing lens optically coupled to the optical fiber; a plurality of diode modules, each configured to output a multimode beam in the cladding optical path; and at least one core-correlated module in the core optical path, configured to provide selection functionality. Additionally, the apparatus and method are configured to frequency double optical radiation.

Description

[0001] This application is a divisional application of the application filed on May 13, 2019, with application number 201980045970.4 and invention title "Laser Beam Method and System". Background of the Invention

[0002] The ability to manipulate beams emitted from lasers, laser beam arrays, and fiber optic arrays has become important in numerous fields, including welding, cutting, surveying, garment manufacturing, laser fusion, communications, laser printing, CDs and optical discs, spectroscopy, heat treatment, barcode scanners, laser cooling, and tracking and positioning technologies. In these and other related fields, laser applications often require the high-speed activation and deactivation of laser beams.

[0003] Currently, methods for manipulating (activating / deactivating) fiber bundles require manipulating the power of the laser system. This includes, for example, "turning on" / "turning off" the seed beam device, redirecting / blocking the seed beam, or cutting off its current. These power manipulations are relatively slow (in the 1-5 kHz range) due to the spontaneous emission time of fiber lasers, and can damage certain components of the laser system when the laser emits amplified spontaneous emissions.

[0004] There has long been a need for a method and / or apparatus that enables high-speed manipulation (activation / deactivation) of high-power laser beams, such as a method and / or apparatus that can be used in beam scanning and other rapid material processing.

[0005] High-power fiber lasers and fiber amplifiers require high-brightness pump sources and efficient techniques to couple with doped fibers, thereby exciting ions and initiating the laser-generating process. Coupled signal power to the core is also crucial.

[0006] A common method for coupling pump and / or signal light to doped optical fibers is based on endface pumping techniques via fused couplings, which are fiber combiners or fused taper fiber bundles (TFBs). A TFB combiner with a signal feedthrough consists of a center input signal fiber and an output pigtail (curled) double-clad (DC) fiber, which combines the signal and pump light in a single pigtail. The use of TFBs involves guiding both the signal and pump light (surrounded by several multimode fibers). To match the diameter of the fiber bundle to the diameter of the output pigtail, the bundle should be slowly melted and gradually tapered. After this tapering process, the bundle is split around the tapered waist and fused together to form the output pigtail DC fiber. However, tapering the fiber bundle inevitably involves increasing the numerical aperture (NA) of the pump light and altering the mode field diameter (MFD) of the signal light. Therefore, the necessary optical matching and mechanical alignment requirements between the tapered fiber bundle and the output DC fiber pigtail may lead to several disadvantages in the TFB structure, such as:

[0007] -After the process of gradually thinning, the flexibility in selecting an input fiber that can be matched with the output pigtail DC fiber is reduced.

[0008] Slight mismatch or misalignment between the signal mode field diameter (MFD) of the tapered input signal fiber and the output pigtail DC fiber can lead to a decrease in beam quality, which is mainly related to signal insertion loss and can also cause catastrophic damage to the fiber during high-power operation.

[0009] - In the case of reverse propagation signals, such as for a reverse propagation pumped fiber amplifier, signal insertion loss (up to 10%) can damage the pump diode due to insufficient isolation of the amplified signal light.

[0010] Another common technique includes monolithic all-fiber combiners, such as graded-tone (GT) wave couplers, which use tapered capillaries around multi-clad fibers, or fuse one or more tapered multimode fibers directly to the outermost cladding of a multi-clad fiber.

[0011] However, the coupling efficiency of current combiners is insufficient to allow their use in ultra-high power amplifiers and lasers. Furthermore, the small core diameter of the signal fiber, resulting from the tapering together with the pump fiber, creates a severe mismatch when coupled to a large mode area double-clad fiber. These large mode area diameter mismatches lead to unacceptably high signal loss, which can cause temperature rise and damage to the TFB.

[0012] Another drawback is their susceptibility to parasitic nonlinear processes (primarily stimulated Brillouin scattering (SBS)) that occur when the laser signal linewidth is narrower than tens of megahertz. This is due to the long interaction length between the optical signal field and the fiber core (caused by the additional fiber length of the components).

[0013] Therefore, a new technology is needed to overcome the above-mentioned defects, reduce the number of welding points, and reduce energy loss.

[0014] In some embodiments, the present invention relates to frequency conversion of high-average power laser beams in nonlinear crystals (NLCs). It relates to an apparatus for correcting a harmful mismatch phase (MP) that may occur in a single NLC or the first of a chain of NLCs between the fundamental frequency input beam and the frequency-converted output beam.

[0015] Past efforts to achieve high-average power harmonic conversion have reached the limits determined by the damage threshold (damage inside the crystal or its anti-reflective coating) or the thermal effects caused by absorption.

[0016] Improvements in crystals and their antireflective (AR) coatings have made thermally induced mismatch phases (TMPs) a major limiting factor for high average power performance. One option for controlling TMPs is to use ultra-low absorption crystals. An example is lithium triborate (LBO) used for frequency doubling in 1064nm lasers.

[0017] However, at a certain power level, the performance of the crystal begins to degrade when heated, and therefore some form of compensation method must be employed.

[0018] One method reported in the literature is to use two crystals with an intermediate phase mismatch compensator (PMC). The PMC is an optical element that exhibits dispersion and / or polarization-dependent refractive index.This dispersion may be an inherent property of the material [D. Fluck and P. Gunter in Optics Comm. 147, 305-308 (1998): "Efficient second-harmonic generation by lens wave-guiding in KNbO crystals"; AK Hansen, M. Tawfieq, OB Jensen, PE Andersen, B. Sumpf, G. Erberty and PM Petersen in Optics Express 23, 15921-15934 (2015): "Concept for power scaling second harmonic generation using a cascade of nonlinear crystals"; AK Hansen, OB Jensen, B. Sumpf, G. Erberty, A. Unterhuber, W. Drexler, PE Andersen, PM Petersen in SPIE Proceedings Vol. 8964 (2016): "Generation of 3.5W of diffraction-limited greenlight from SHG of a "Single tapered diode laser in acascade of nonlinear crystals"; X. Liu, X. Shen, J. Yin and X. Li in J. Opt. Soc. Am. B 34, 383-388 (2017): "Three-crystal method for thermally induced phase mismatch compensation in second-harmonic generation"; or, it can be applied by an external electric field (an electric field applied to the electro-optic material, such as the electric field in a Pockels cell) [Z. Cui, D. Liu, I. M. Suny, J. Miao and J. Zhu in JOSA B 33, 525-534 (2016): "Compensation method for temperature-induced phase mismatch during frequency conversion in high-power laser systems"].

[0019] PMC has been proven in the laboratory and in simulations to be very effective in compensating for MP in the second crystal of a bicrystalline frequency doubling chain. However, at sufficiently high input power, better handling of MP in the first frequency conversion crystal is required.

[0020] A frequency doubling module for converting the input laser wavelength can consist of one or more nonlinear crystals (NLCs) placed in series. The input light is focused into the first crystal and then relay-imaged between subsequent crystals via achromatic optics, thereby maximizing the frequency doubling of each crystal and each frequency doubling system. The crystals can be separated by a phase mismatch compensator (PMC), which functions to correct any phase mismatch between the fundamental and harmonic beams that occurs during the frequency doubling process before the high-intensity interaction region of any particular crystal.

[0021] Typically, even if some degree of control can be attempted by changing the crystal's operating temperature, such systems are considered static. Current frequency doubling systems are configured to operate at a single operating point, and the PMC is tuned to maintain a fixed phase difference. Therefore, an active PMC is needed to provide the boost capability. Invention Overview

[0022] In some embodiments, a method is provided for modulating a laser beam provided by a laser system, the laser system including at least one seed laser device and a coherent beam combining (CBC) system, the coherent beam combining system being configured to receive a seed beam from the seed laser device and to selectively provide an amplified laser beam; the CBC system including:

[0023] - Multiple phase modulators configured to be (directly or indirectly) optically connected to: the seed beam, multiple optical amplifiers, at least one beam splitter, and optionally at least one beam combiner; the seed beam, the multiple optical amplifiers, the at least one beam splitter, and optionally the at least one beam combiner are all arranged to enable constructive or destructive beam interference at the CBC point; and

[0024] - At least one control circuit, the at least one control circuit being configured to monitor beam interference at the CBC point and control at least one phase modulator of the phase modulators accordingly;

[0025] The method includes the following steps:

[0026] ■ The laser beam is provided by activating the laser beam by controlling the phase modulator to provide the phase-construction beam interference at the CBC point;

[0027] ■The laser beam is deactivated by controlling the phase modulator to provide the destructive beam interference at the CBC point, thereby blocking the laser beam.

[0028] In some embodiments, the step of activating by controlling the phase modulator to provide the constructive beam interference includes tuning the phase modulator to provide the constructive beam interference with maximum intensity.

[0029] In some embodiments, the step of deactivating by controlling the phase modulator to provide the destructive interference includes controlling half of the tuned phase modulators to add half a phase (π) to the beam of the half of the tuned phase modulators.

[0030] In some embodiments, the step of deactivating by controlling the phase modulator to provide the destructive interference includes modifying some of the tuned phase modulators.

[0031] In some embodiments, each of the tuned phase modulators is modified differently.

[0032] In some embodiments, the method further includes the step of tuning the laser beam by modifying some of the phase modulators tuned to provide maximum beam intensity, the modification being configured such that the intensity of the laser beam is equal to a predetermined percentage of the maximum intensity.

[0033] In some embodiments, the step of deactivating by controlling the phase modulator to provide the destructive beam interference includes tuning the phase modulator to provide the beam interference with minimum intensity.

[0034] In some embodiments, a method for modulating a laser beam provided by a laser system is provided, the laser system comprising:

[0035] - At least one seed laser device;

[0036] - A fast optical modulator (FOM) configured to receive a seed beam from the seed laser device and modulate the bandwidth of the seed beam;

[0037] - A coherent beam combining (CBC) system, which is configured to receive a modulated seed beam and accordingly provide an amplified laser beam;

[0038] The method includes the following steps:

[0039] ■ The laser beam is provided by controlling the FOM to provide a seed beam with a first (narrow) bandwidth (Δω1), thereby enabling constructive interference at the CBC point of the CBC system;

[0040] ■ By controlling the FOM to provide a seed beam with a second (wide) bandwidth (Δω2, where Δω2>Δω1) to deactivate the laser beam, thereby blocking the laser beam, the second bandwidth being configured to disable constructive interference at the CBC point.

[0041] In some embodiments, the CBC system includes:

[0042] - Multiple phase modulators configured to be optically connected (directly or indirectly) to: the modulated seed beam, multiple optical amplifiers, at least one beam splitter, and optionally at least one beam combiner; the modulated seed beam, the multiple optical amplifiers, the at least one beam splitter, and optionally the at least one beam combiner are all arranged to enable constructive beam interference at the CBC point; and

[0043] - At least one control circuit, the at least one control circuit being configured to monitor beam interference at the CBC point and control at least one phase modulator of the phase modulators accordingly;

[0044] Furthermore, the activation step also includes controlling the phase modulator to provide the phase-length beam interference.

[0045] In some embodiments, the step of controlling the phase modulator to provide the phase-length beam interference includes tuning the phase modulator to provide the phase-length beam interference with maximum intensity.

[0046] In some embodiments, a method for modulating a laser beam provided by a laser system is provided, the laser system comprising:

[0047] - A coherent beam combining (CBC) system, which is configured to receive a seed laser beam and accordingly provide an amplified laser beam;

[0048] - A first seed laser device, configured to provide a first seed beam having a first wavelength (λ1);

[0049] - A second seed laser device, configured to provide a second seed beam having a second wavelength (λ2), the second wavelength being different from the first wavelength (λ2 ≠ λ1); and

[0050] - An optical switch configured to link only one of the first seed beam and the second seed beam to the CBC system;

[0051] The CBC system includes:

[0052] - A plurality of phase modulators configured to be optically linked (directly or indirectly) to: a linked (first or second) seed laser beam, a plurality of optical amplifiers, at least one beam splitter, and optionally at least one beam combiner; the linked seed laser beam, the plurality of optical amplifiers, the at least one beam splitter, and optionally the at least one beam combiner are all arranged to enable constructive beam interference at the CBC point; and

[0053] - At least one control circuit, the at least one control circuit being configured to monitor beam interference at the CBC point and control at least one phase modulator of the phase modulators accordingly;

[0054] The method includes the following steps:

[0055] ■ The laser beam is provided by controlling the optical switch to link the first seed beam to the CBC system and controlling the phase modulator to provide the constructive beam interference;

[0056] ■ By controlling the optical switch to link the second seed beam to the CBC system, the laser beam is deactivated, thereby disabling the constructive beam interference and blocking the laser beam.

[0057] In some embodiments, controlling the phase modulator to provide the constructive beam interference includes tuning the phase modulator to provide the constructive beam interference with maximum intensity.

[0058] In some embodiments, a method for modulating a laser beam provided by a laser system is provided, the laser system comprising:

[0059] - A coherent beam combining (CBC) system, which is configured to receive a seed laser beam and accordingly provide an amplified laser beam;

[0060] - A first seed laser device, the first seed laser device being configured to provide a first seed laser beam having a first bandwidth (Δω1);

[0061] - A second seed laser device, configured to provide a second seed laser beam having a second bandwidth (Δω2), the second bandwidth being greater than the first bandwidth (Δω2>Δω1); and

[0062] - An optical switch configured to link only one of the first seed beam and the second seed beam to the CBC system;

[0063] Wherein, the first bandwidth (Δω1) is configured to enable constructive beam interference at the CBC point of the CBC system, and wherein the second bandwidth (Δω2) is configured to disable constructive beam interference at the CBC point;

[0064] The method includes the following steps:

[0065] ■ The laser beam is activated by controlling the optical switch to link the first seed laser beam to the CBC system, thereby enabling constructive interference and providing the laser beam;

[0066] ■ By controlling the optical switch to link the second seed laser beam to the CBC system, the laser beam is deactivated, thereby disabling constructive interference and blocking the laser beam.

[0067] In some embodiments, the CBC system includes:

[0068] - A plurality of phase modulators configured to be optically linked (directly or indirectly) to: a linked (first or second) seed beam, a plurality of optical amplifiers, at least one beam splitter, and optionally at least one beam combiner; the linked seed beam, the plurality of optical amplifiers, the at least one beam splitter, and optionally at least one beam combiner are all arranged to enable constructive beam interference at the CBC point; and

[0069] - At least one control circuit, the at least one control circuit being configured to monitor beam interference at the CBC point and control at least one phase modulator of the phase modulators accordingly;

[0070] Furthermore, the activation step also includes controlling the phase modulator to provide the phase-length beam interference.

[0071] In some embodiments, controlling the phase modulator to provide the constructive beam interference includes tuning the phase modulator to provide the constructive beam interference with maximum intensity.

[0072] In some embodiments, a method for modulating a laser beam provided by a laser system is provided, the laser system comprising:

[0073] - A coherent beam combining (CBC) system configured to receive a seed beam and provide an amplified laser beam;

[0074] - A first seed laser, configured to provide a first seed beam having a first wavelength (λ1);

[0075] - A second seed laser, configured to provide a second seed beam having a second wavelength (λ2), the second wavelength being different from the first wavelength (λ2≠λ1);

[0076] - An optical switch configured to link only one of the first seed beam and the second seed beam to the CBC system; and

[0077] - A dichroic mirror, configured to receive the amplified laser beam, transmit a beam having the first wavelength (λ1) to the output of the laser system, and reflect a beam having the second wavelength (λ2), thus selectively providing the output laser beam;

[0078] The method includes the following steps:

[0079] ■ The laser beam is delivered and provided by activating the laser beam by controlling an optical switch to link the first seed beam to the CBC system;

[0080] ■The laser beam is deactivated by controlling an optical switch to link the second seed beam to the CBC system, thereby reflecting and avoiding the laser beam.

[0081] In some embodiments, the CBC system includes:

[0082] - A plurality of phase modulators configured to be optically connected (directly or indirectly) to: a linked (first or second) seed beam, a plurality of optical amplifiers, at least one beam splitter, and optionally at least one beam combiner; the linked seed beam, the plurality of optical amplifiers, the at least one beam splitter, and optionally the at least one beam combiner are all arranged to enable constructive beam interference at the CBC point; and

[0083] - At least one control circuit, the at least one control circuit being configured to monitor beam interference at the CBC point and being configured to control at least one of the phase modulators accordingly;

[0084] Furthermore, the method further includes controlling the phase modulator at least during the activation step to provide the phase-length beam interference at the CBC point.

[0085] In some embodiments, controlling the phase modulator to provide the constructive beam interference includes tuning the phase modulator to provide the constructive beam interference with maximum intensity.

[0086] In some embodiments, a method for modulating a laser beam provided by a laser system is provided, the laser system comprising:

[0087] - Master Oscillator Power Amplifier (MOPA), which is configured to receive a seed beam and provide an amplified laser beam;

[0088] - A first seed laser, configured to provide a first seed beam having a first wavelength (λ1);

[0089] - A second seed laser, configured to provide a second seed beam having a second wavelength (λ2), the second wavelength being different from the first wavelength (λ2≠λ1);

[0090] - An optical switch configured to link only one of the first seed beam and the second seed beam to the MOPA; and

[0091] - A dichroic mirror, configured to receive the amplified laser beam, transmit a beam having the first wavelength (λ1) to the output of the laser system, and reflect a beam having the second wavelength (λ2), thus selectively providing the output laser beam;

[0092] The method includes the following steps:

[0093] ■ The laser beam is delivered and provided by activating the laser beam by controlling an optical switch to link the first seed beam to the MOPA;

[0094] ■The laser beam is deactivated by controlling an optical switch to link the second seed beam to the MOPA, thereby reflecting and avoiding the laser beam.

[0095] In some embodiments, a method for modulating a laser beam provided by a laser system is provided, the laser system comprising:

[0096] - At least one seed laser device;

[0097] - An optical polarization beam combiner (OPC) configured to receive a seed laser beam from the seed laser device and modulate the polarization direction of the seed laser beam; wherein the modulation includes providing at least two polarization components to the seed beam, wherein one of the polarization components includes a predetermined polarization direction (P1).

[0098] - A coherent beam combining (CBC) system configured to receive the polarization-modulated seed beam and provide an amplified laser beam; and

[0099] - A polarization beam splitter (PBS) configured to receive the amplified laser beam and transmit only the beam having the predetermined polarization direction (P1) to the output of the laser system, and reflect the beam having another polarization direction, thereby selectively providing the laser beam;

[0100] The method includes the following steps:

[0101] ■The laser beam is provided by controlling the OPC to activate the beam component having the predetermined polarization direction (P1) and an intensity (I1) greater than 50% of the total intensity of the seed laser beam;

[0102] ■The laser beam is deactivated by controlling the OPC to provide a beam component having the predetermined polarization direction (P1) and an intensity (I1) equal to or less than 50% of the total intensity of the seed laser beam, thereby avoiding the laser beam.

[0103] In some embodiments, the method further includes the step of: tuning the laser beam by controlling the OPC to provide a beam component having the predetermined polarization direction (P1) and an intensity (I1) equal to a predetermined percentage of the total intensity of the seed laser beam.

[0104] In some embodiments, the CBC system includes:

[0105] - Multiple phase modulators configured to be optically connected (directly or indirectly) to: the polarization-modulated seed beam, multiple optical amplifiers, at least one beam splitter, and optionally at least one beam combiner; the polarization-modulated seed beam, the multiple optical amplifiers, the at least one beam splitter, and optionally the at least one beam combiner are all arranged to enable constructive beam interference at the CBC point; and

[0106] - At least one control circuit, the at least one control circuit being configured to monitor beam interference at the CBC point and control at least one phase modulator of the phase modulators accordingly;

[0107] Furthermore, the method further includes controlling the phase modulator at least during the activation step to provide the phase-length beam interference at the CBC point.

[0108] In some embodiments, the OPC includes:

[0109] - A beam splitter assembly configured to receive an input beam having a first polarization direction (P1) and configured to output a first beam (B1(I1, P1)) having the first polarization direction (P1) and a first intensity (I1) and a second beam (B2(I2, P1)) having the first polarization direction (P1) and a second intensity (I2), wherein the sum of the first intensity and the second intensity (I1+I2) is equal to the intensity of the input beam;

[0110] - A polarization converter configured to receive one of the output beams (B1 or B2) from the beam splitter assembly and convert the polarization of the one of the output beams (from S to P, or from P to S, therefore P1 ≠ P2, B2 (I2, P2)); and

[0111] - A polarization beam splitter (PBS), configured to receive the first output beam (B1(I1, P1)) and the second converted output beam (B2(I2, P2)), and combine the first output beam and the second converted output beam into a third beam, which is provided as an input to the CBC system; or, a coupler, configured to receive the first output beam (B1(I1, P1)) and the second converted output beam (B2(I2, P2)), combine the first output beam and the second converted output beam, and split the first output beam and the second converted output beam into two output beams, wherein only one of the two output beams is provided as an input to the CBC system.

[0112] In some embodiments, the beam splitter assembly includes:

[0113] - A beam splitter, configured to receive an input beam and split the input beam into two beams;

[0114] - A phase modulator, the phase modulator being configured to modulate the phase of one of the two beams;

[0115] - A coupler configured to receive the two beams (after the phase of one of the beams in the modulated beam) and provide interference of the two beams at two locations, thereby providing a first output beam (B1(I1, P1)) and a second output beam (B2(I2, P1));

[0116] - An electronic controller configured (optionally via a telescoper (TAP))

[0117] (and diode) monitor one of two interference positions and control the phase modulator to enable constructive or destructive beam interference at the monitored position accordingly, wherein destructive or constructive beam interference is thereby provided to the unmonitored interference position accordingly;

[0118] Furthermore, the step of controlling the OPC includes controlling the phase modulator (via a controller).

[0119] In some embodiments, a method for modulating a laser beam provided by a laser system is provided, the laser system comprising:

[0120] - At least one seed laser device;

[0121] - At least one optical polarization combiner (OPC), configured to receive a seed beam from the seed laser device and modulate the polarization direction of the seed beam; wherein the modulation includes providing at least two polarization components to the seed beam.

[0122] Wherein, one of the polarization components includes a predetermined polarization direction (P1);

[0123] - Master Oscillator Power Amplifier (MOPA), the master oscillator power amplifier being configured to receive the modulated seed beam and provide an amplified laser beam; and

[0124] - A polarization beam splitter (PBS) configured to receive the amplified laser beam and transmit only the beam having the predetermined polarization direction (P1) to the output of the laser system, and reflect the beam having another polarization direction, thereby selectively providing the laser beam;

[0125] The method includes the following steps:

[0126] ■The laser beam is provided by controlling the OPC to activate the beam component having the predetermined polarization direction (P1) and an intensity (I1) greater than 50% of the total intensity of the beam.

[0127] ■The laser beam is deactivated by controlling the OPC to provide a beam component having the predetermined polarization direction (P1) and an intensity (I1) equal to or less than 50% of the total intensity of the beam, thereby avoiding the laser beam.

[0128] In some embodiments, a laser system configured to modulate a laser beam is provided, the laser system comprising:

[0129] - At least one seed laser device;

[0130] - At least one optical polarization beam combiner (OPC) configured to receive the seed beam from the seed laser device and modulate the polarization direction of the seed beam;

[0131] -The modulation includes providing at least two polarization components to the seed beam, wherein one of the polarization components includes a predetermined polarization direction (P1);

[0132] - A coherent beam combining (CBC) system, which is configured to receive a polarization-modulated seed beam and provide an amplified laser beam;

[0133] - A polarization beam splitter (PBS), configured to receive the amplified laser beam and transmit only beams having the predetermined polarization direction (P1) to the output of the laser system, while reflecting beams having other polarization directions, thus selectively providing the laser beam; and

[0134] - An electronic controller, the electronic controller being configured to:

[0135] ■The laser beam is activated by controlling the OPC to provide a beam component having the predetermined polarization direction (P1) and an intensity (I1) greater than 50% of the total intensity of the beam, thus providing the laser beam;

[0136] ■The laser beam is deactivated by controlling the OPC to provide a beam component having the predetermined polarization direction (P1) and an intensity (I1) equal to or less than 50% of the total intensity of the beam, thus avoiding the laser beam.

[0137] In some embodiments, the CBC system includes:

[0138] - Multiple phase modulators configured to be optically connected (directly or indirectly) to: the polarization-modulated seed beam, multiple optical amplifiers, at least one beam splitter, and optionally at least one beam combiner; the polarization-modulated seed beam, the multiple optical amplifiers, the at least one beam splitter, and optionally the at least one beam combiner are all arranged to enable constructive beam interference at the CBC point; and

[0139] - At least one control circuit configured to monitor beam interference at the CBC point and accordingly control at least one phase modulator of the phase modulators to provide the constructive interference at the CBC point.

[0140] In some embodiments, the OPC includes:

[0141] - A beam splitter assembly configured to receive an input beam having a first polarization direction (P1) and configured to output a first beam (B1(I1, P1)) having the first polarization direction (P1) and a first intensity (I1) and a second beam (B2(I2, P1)) having the first polarization direction (P1) and a second intensity (I2), wherein the sum of the first intensity and the second intensity (I1+I2) is equal to the intensity of the input beam;

[0142] - A polarization converter configured to receive one of the output beams (B1 or B2) from the beam splitter assembly and convert the polarization of the one of the output beams (from S to P, or from P to S, therefore P1 ≠ P2, B2 (I2, P2)); and

[0143] - A polarization beam splitter configured to receive the first output beam (B1(I1, P1)) and the second converted output beam (B2(I2, P2)), and combine the first output beam and the second converted output beam into a third beam, which is provided as an input to the CBC system; or, a coupler configured to receive the first output beam (B1(I1, P1)) and the second converted output beam (B2(I2, P2)), combine the first output beam and the second converted output beam, and split the first output beam and the second converted output beam into two output beams, wherein only one of the two output beams is provided as an input to the CBC system.

[0144] In some embodiments, the beam splitter assembly includes:

[0145] - A beam splitter, configured to receive an input beam and split the input beam into two beams;

[0146] - A phase modulator, the phase modulator being configured to modulate the phase of one of the two beams;

[0147] - A coupler configured to receive the two beams (after the phase of one of the beams in the modulated beam) and provide interference of the two beams at two locations, thereby providing a first output beam (B1(I1, P1)) and a second output beam (B2(I2, P1));

[0148] - An electronic controller configured (optionally via a telescoper (TAP))

[0149] The diode monitors one of two interference positions and controls the phase modulator to enable constructive or destructive beam interference at the monitored position accordingly, and thereby provides destructive or constructive beam interference to the unmonitored interference position accordingly.

[0150] In some embodiments of the present invention, a hybrid fiber-coupled diode pump module (in short, a pump module) is provided, the hybrid pump module being configured to be coupled to an optical fiber having a core and at least one cladding, the pump module comprising:

[0151] - At least one focusing lens in the optical path carrying the optical fiber;

[0152] - Multiple diode modules, each configured to output a multimode beam in an optical path having the cladding;

[0153] - At least one core-related module in the optical path carrying the core, the core-related module being configured to provide functionality selected from the group consisting of:

[0154] a) Output a single-mode beam to the core;

[0155] b) Receive the light beam from the core and couple the received light beam to the output fiber;

[0156] c) Receive the light beam from the core and reflect the received light beam back to the core, and

[0157] d) Receive the light beam from the core, reflect a portion of the received light beam back to the core, and couple the remaining portion of the received light beam to the output fiber.

[0158] In some embodiments, the pump module further includes a volume Bragg grating (VBG) configured to narrow the beam and lock the beam to a predetermined wavelength range.

[0159] In some embodiments, the plurality of diode modules and the chip-related module are arranged in at least one row such that the output beams of the plurality of diode modules and the chip-related module in each row are parallel to each other.

[0160] In some embodiments, when there are two or more rows, the pump module further includes:

[0161] - At least one polarizer beam combiner in the path of the first beam;

[0162] - One or more folding mirrors, each folding mirror for each additional row, wherein each folding mirror is configured to redirect the parallel beam row corresponding to each folding mirror into the corresponding polarizer beam combiner.

[0163] In some embodiments, each diode module in the diode module includes:

[0164] - Wide-area laser (BAL);

[0165] - A BAL-associated folding mirror, wherein the BAL-associated folding mirror is configured with an optical path between the BAL associated with the BAL-associated folding mirror and the cladding; and

[0166] - Optionally, at least one lens is disposed between the BAL and the folding mirror associated with the BAL, and is configured to adjust the shape of the beam of light from the BAL.

[0167] In some embodiments, the core-related module includes a seed module, the seed module comprising:

[0168] - At least one seed input terminal, the at least one seed input terminal being configured to be coupled to a seed laser device;

[0169] - A seed-associated folding mirror, configured for an optical path between the seed input and the core; and

[0170] - Optionally, at least one lens is disposed between the seed input end and a folding mirror associated with the seed input end, and is configured to adjust the shape of the beam of the seed.

[0171] In some embodiments, the seed-related module further includes at least one of the following:

[0172] - A beam amplifier, the beam amplifier being configured to amplify the seed beam;

[0173] - A beam splitter (tap) (not shown) or a local reflector configured to sample the seed beam; and a monitor configured to monitor and alert to reverse beam transmission; and

[0174] - An isolator, which is configured to allow light to travel in only one direction.

[0175] In some embodiments, the chip-related module includes an output module, the output module comprising:

[0176] - Output optical fiber, which optionally includes an end cap element;

[0177] - A folding mirror associated with the output fiber, the folding mirror being configured for an optical path between the core and the output fiber;

[0178] Optionally, at least one lens is disposed between the output optical fiber and a folding mirror associated with the output optical fiber, and is configured to adjust the shape of the received core bundle; and

[0179] -Optimal, pump-dump.

[0180] In some embodiments, the chip-related module includes a high reflectivity (HR) module, the high reflectivity module comprising:

[0181] -HR lens;

[0182] - A folding mirror associated with the HR mirror, the folding mirror being configured for an optical path between the core and the HR mirror; and

[0183] - Optionally, at least one lens is disposed between the HR mirror and a folding mirror associated with the HR mirror, and is configured to adjust the shape of the associated beam.

[0184] In some embodiments, the HR module further includes an intracavity modulator disposed between the HR mirror and a folding mirror associated with the HR mirror, and configured to modulate the reflected light beam.

[0185] In some embodiments, the core-related module includes a local reflection (PR) module, the local reflection (PR) module comprising:

[0186] - Output optical fiber, the output optical fiber optionally including an end cap;

[0187] - A PR mirror in the optical path carrying the output fiber;

[0188] - A folding mirror associated with the PR mirror, the folding mirror being configured for an optical path between the core and the PR mirror; and

[0189] - Optionally, at least one lens is disposed between the PR mirror and the folding mirror associated with the PR mirror, and is configured to adjust the shape of the associated beam.

[0190] In some embodiments, the pump module further includes at least one heat dissipation element selected from the group consisting of: a bottom surface, a rib, a screw, and any combination of the bottom surface, the rib, and the screw.

[0191] In some embodiments of the present invention, an optical fiber amplification system is provided, comprising:

[0192] - An optical fiber, the optical fiber comprising a core and at least one cladding;

[0193] -According to at least some of the pump modules described in the above embodiments, the hybrid pump module is coupled to a first end of the optical fiber.

[0194] In some embodiments, the system further includes at least one selected from the following: a pump dump and an end cap element.

[0195] In some embodiments, the fiber optic amplification system further includes a pump module according to at least some of the above embodiments coupled to a second end of the fiber optic cable.

[0196] In some embodiments of the present invention, a fiber laser system is provided, comprising:

[0197] - An optical fiber, the optical fiber comprising a core and at least one cladding;

[0198] - According to at least some of the pump modules described in the above embodiments, the hybrid pump module is coupled to a first end of the optical fiber; and

[0199] - A fiber Bragg grating (FBG) or a hybrid pumping module according to at least some of the above embodiments, wherein the fiber Bragg grating (FBG) or the hybrid pumping module is coupled to a second end of the optical fiber.

[0200] In some embodiments, the fiber laser system further includes at least one of the following: a pump-dump unit and an end cap element.

[0201] Some embodiments of the present invention are based on adding a weak second-harmonic seed beam to the high-power fundamental frequency beam before the power frequency multiplier (PFD) nonlinear crystal (NLC). Therefore, the phase difference between the seed and fundamental frequency beams is controlled to provide a conjugate phase difference that will be generated in the first PFD NLC. The end result is a minimum mismatch phase (MP) generated by the input of the PFD and through the harmonic conversion region in the NLC.

[0202] In some embodiments, a temperature- and / or angle-tuned PFD NLC is provided, configured to achieve optimal harmonic conversion in the maximum conversion region (the focal waist if a lens is used, or the entire crystal length if the beam is collimated), and thus, by adding a seed beam, sufficient parameters are provided to achieve a conversion efficiency within 5% of the conversion efficiency achieved without using MP.

[0203] In some embodiments of the invention, novel devices configured to frequency double optical radiation are provided, the novel devices comprising at least two sequential nonlinear crystals (NLCs):

[0204] - First NLC, the first NLC is configured to receive baseband (F) FThe fundamental frequency beam is emitted at the second harmonic frequency (F). H The weak second harmonic beam at the fundamental frequency (F) and the weak second harmonic beam at the fundamental frequency (F) F The strong residual beam at the location; the power ratio between the weak second harmonic beam and the fundamental frequency beam is correspondingly less than 5 × 10. -3 :1; and

[0205] - At least one second NLC, the second NLC being configured to receive the signal from the previous NLC at the base frequency (F). F The remaining beam at the second harmonic frequency (F) and the remaining beam at the second harmonic frequency (F) H The second harmonic beam at the second harmonic frequency (F) is configured to be emitted at the second harmonic frequency (F). H The strong harmonic beam at the fundamental frequency (F) and the strong harmonic beam at the fundamental frequency (F) F The remaining beam at position ); the power ratio between the strong overtone beam and the fundamental beam is correspondingly greater than 0.3:1.

[0206] In some embodiments, the device further includes at least one phase mismatch compensator (PMC), the phase mismatch compensator being configured to operate at the fundamental frequency (F... F The remaining beam at the second harmonic frequency (F) and the second harmonic frequency (F) H The second harmonic beam at the fundamental frequency (F) is corrected before being received by the second NLC. F The remaining beam at point ) and the second harmonic frequency (F) H The phase relationship between the second harmonic beams at point ().

[0207] In some embodiments, the device further includes at least one feedback and control system configured to sample the high frequency harmonic beam and adjust the PMC accordingly to achieve the maximum power of the high frequency harmonic beam.

[0208] In some embodiments, the feedback and control system includes: at least one measuring element, at least one processing element, and at least one adjusting element configured to adjust the PMC.

[0209] In some embodiments, the above-described apparatus further includes at least one oven, each oven being configured to adjust the temperature of the NLC.

[0210] In some embodiments, the length (L) of the first NLC s ) equal to or less than the length (L) of the second NLC D 10% (L) s ≤0.1L D ).

[0211] In some embodiments, the second NLC includes an LBO, and the length of the second NLC (LD (Greater than 40mm)

[0212] In some embodiments, the base frequency (F) F This includes the characteristics of infrared (IR) light (λ). F =1064nm), therefore the second harmonic frequency (F H This includes the properties of visible light (λ). H =532nm).

[0213] In some embodiments, each of the NLCs is configured with a fundamental frequency beam polarization along the crystal axis of each NLC or is configured with a fundamental frequency beam polarization at 45° relative to the crystal axis of each NLC.

[0214] In some embodiments, each NLC in the NLC includes at least one material selected from the group consisting of: BBO, KTP, LBO, CLBO, DKDP, ADP, KDP, LiIO3, KNbO3, LiNbO3, AgGaS2, AgGaSe2.

[0215] In some embodiments, the size of the lateral region of each NLC is larger than the size of the input beam received by each NLC.

[0216] In some embodiments, the device further includes at least one converging element configured to focus the light beam into the NLC.

[0217] In some embodiments of the present invention, a novel method for frequency doubling of optical radiation is provided, the method comprising:

[0218] - Provide nonlinear crystals (NLCs) with a frequency at the fundamental frequency (F) F The fundamental frequency beam at ) and at the second harmonic frequency (F H The weak second harmonic beam at () location;

[0219] -thus emitted via the NLC at the second harmonic frequency (F H The strong harmonic beam at the fundamental frequency (F) and the strong harmonic beam at the fundamental frequency (F) F The remaining beam at () position;

[0220] The power ratio between the provided weak second harmonic beam and the fundamental frequency beam is correspondingly less than 5×10⁻³:1;

[0221] Furthermore, the power ratio between the emitted high-frequency harmonic beam and the fundamental frequency beam is correspondingly greater than 0.3:1.

[0222] In some embodiments, the method further includes the step of providing the following steps: performing phase mismatch compensation between the fundamental frequency beam and the weak second harmonic beam; and wherein the method further includes controlling the PMC to achieve the maximum power of the strong harmonic beam.

[0223] In some embodiments of the present invention, an apparatus configured to frequency multiply an input of optical radiation and provide an output beam including a second harmonic frequency is provided, the apparatus comprising:

[0224] - At least two sequential nonlinear crystals (NLCs); each NLC is configured to receive signals from the previous NLC at the fundamental frequency (F). F The first beam at the second harmonic frequency (F) and optional beam at the second harmonic frequency (F) H The second beam is positioned at the second harmonic frequency (F) and is configured to be emitted at the second harmonic frequency (F). H The strong harmonic beam at the fundamental frequency (F) and the strong harmonic beam at the fundamental frequency (F) F The remaining beam at () position;

[0225] - At least one phase mismatch compensator (PMC), said phase mismatch compensator being positioned between the two NLCs; said PMC being configured to operate at the base frequency (F F The remaining beam at the second harmonic frequency (F) and the second harmonic frequency (F) H The second harmonic beam at the specified frequency (F) is corrected before being received by the subsequent NLC. F The remaining beam at the second harmonic frequency (F) and the second harmonic frequency (F) H The phase relationship between the second harmonic beams at point ) and

[0226] - Each of the PMCs is equipped with an electric rotating device configured to actively rotate the PMC and thus actively adjust the correction of the phase relationship between the remaining beam and the second harmonic beam.

[0227] In some embodiments, the device further includes at least one feedback and control system configured to sample the high frequency harmonic beam and accordingly tilt the PMC via the electric rotating device to achieve maximum power of the high frequency harmonic beam.

[0228] In some embodiments, the feedback and control system includes: at least one beam splitter, at least one measuring element, at least one processing element, and at least one control element configured to control the electric rotating device.

[0229] In some embodiments, the PMC includes an optically transparent window exhibiting dispersion, such that the distance the light beam must travel through the window varies with respect to the beam rotation angle. According to some embodiments, the PMC includes a plate exhibiting dispersion, such that the distance the light beam must travel through the window (e.g., an optically transparent plate polished on both sides) varies with respect to the beam rotation angle.

[0230] In some embodiments, the motor is configured to cause the PMC to rotate in a stepping and / or continuous motion manner.

[0231] In some embodiments, the motor is further configured to cause the PMC to rotate in a jittering manner limited to an upper limit and a lower limit.

[0232] In some embodiments, the feedback and control system is configured to use the jitter pattern to provide at least one of the following:

[0233] - Minimize the inversion conversion in the subsequent NLC to maximize the power of the output beam;

[0234] - Maximize the inverse conversion in the subsequent NLC to minimize the power of the output beam;

[0235] - Adjusting the power of the output beam to the predetermined value between the maximum and minimum values ​​under dynamic or static operating conditions may include changing the input laser power and / or changing the oven temperature.

[0236] In some embodiments, the motor is configured to rotate the PMC in a switching mode between a maximum harmonic conversion state and a minimum harmonic conversion state, such that the output beam is switched on and off accordingly.

[0237] In some embodiments, the motor is configured to rotate the PMC to provide a flat-top pulse with controlled rise and fall times and a controllable duration.

[0238] In some embodiments, the motor is configured to rotate the PMC according to a lookup table, and thus provide shaped harmonic pulses.

[0239] In some embodiments, the device further includes at least one dichroic beam splitter configured to separate at least a portion of the remaining beam from the output beam.

[0240] In some embodiments, the power ratio between the emitted high-frequency harmonic beam and the emitted fundamental frequency beam is correspondingly greater than 0.3:1.

[0241] In some embodiments, the apparatus further includes at least one oven, each configured to adjust the temperature of the NLC. In some embodiments, the apparatus further includes at least two ovens, each configured to adjust the temperature of a different NLC.

[0242] In some embodiments, the active control of the PMC is configured to minimize power variations caused by temperature changes in the oven housing the NLC.

[0243] In some embodiments, at least one NLC in the NLC includes an LBO, and its length (L D This is sufficient to achieve significant harmonic light. In some embodiments, at least one of the NLCs includes an LBO, and its length (L...) is sufficient to achieve significant harmonic light. D (Greater than 40mm)

[0244] In some embodiments, the base frequency (F) F This includes the characteristics of infrared (IR) light (λ). F =1064nm), therefore the second harmonic frequency (F H This includes the properties of visible light (λ). H =532nm).

[0245] In some embodiments, each of the NLCs is configured with a fundamental frequency beam polarization along the crystal axis of each NLC or is configured with a fundamental frequency beam polarization at 45° relative to the crystal axis of each NLC.

[0246] In some embodiments, each NLC in the NLC includes at least one material selected from the group consisting of: BBO, KTP, LBO, CLBO, DKDP, ADP, KDP, LiIO3, KNbO3, LiNbO3, AgGaS2, AgGaSe2.

[0247] In some embodiments, the size of the lateral region of each NLC is larger than the size of the input beam received by each NLC.

[0248] In some embodiments, the device further includes at least one achromatic converging element configured to focus the fundamental beam and harmonic beam into the NLC.

[0249] In some embodiments of the present invention, a method is provided for activating (“turning on”) and / or deactivating (“turning off”) a frequency-doubled output beam from the aforementioned device; the method includes:

[0250] -Sampling and measuring the output beam;

[0251] - Determine if the output beam has reached the maximum value required to "turn on" the output (or the minimum value required to "turn off" the output).

[0252] ■ If “No”, rotate the PMC and repeat the method from the sampling step;

[0253] ■ If "yes", then keep the current angle at α. 最大 (or α) 最小 The method is repeated from the sampling step in any case of dynamic input beam and / or dynamic oven temperature. Brief description of the attached diagram

[0254] The subject matter considered to be the present invention is specifically pointed out and clearly claimed in the conclusion section of the specification. However, the organization and operation of the invention, as well as its objects, features, and advantages, can be best understood by referring to the following detailed description while reading the accompanying drawings, wherein:

[0255] Figure 1 An example of a prior art coherent beam combining (CBC) system is illustrated schematically;

[0256] Figure 2 A laser system according to some embodiments is schematically illustrated, the laser system including a seed laser device and a coherent beam combining (CBC) system, both of which are configured as modulated and amplified laser beams;

[0257] Figure 3 A laser system according to some embodiments is schematically illustrated, the laser system including a seed laser device, a fast optical modulator (FOM) and a coherent beam combining (CBC) system, all configured to modulate an amplified laser beam;

[0258] Figure 4 A laser system according to some embodiments is schematically illustrated, the laser system including two seed laser devices that each provide seed beams of different wavelengths, an optical switch, and a coherent beam combining (CBC) system, all of which are configured to modulate and amplify the laser beams;

[0259] Figure 5 A laser system according to some embodiments is schematically illustrated, the laser system including two seed laser devices that each provide seed beams with different bandwidths, an optical switch, and a coherent beam combining (CBC) system, all of which are configured to modulate and amplify the laser beam;

[0260] Figure 6A A laser system according to some embodiments is schematically shown, the laser system including two seed laser devices that each provide seed beams of different wavelengths, an optical switch, a dichroic mirror and a coherent beam combining (CBC) system, all of which are configured to modulate and amplify the laser beam;

[0261] Figure 6B A laser system according to some embodiments is schematically shown, the laser system including two seed laser devices, each providing a seed beam of different wavelengths, an optical switch, a dichroic mirror, and a master oscillator power amplifier (MOPA), all of which are configured to modulate the amplified laser beam;

[0262] Figure 6C Another laser system according to some embodiments is schematically shown, which includes two seed laser devices that each provide seed beams of different wavelengths, an optical switch, a dichroic mirror, and a coherent beam combining (CBC) system, all of which are configured to modulate and amplify the laser beams.

[0263] Figure 7A A laser system according to some embodiments is schematically illustrated, the laser system including a seed laser device, an optical polarization beam combiner (OPC), a polarization beam splitter (PBS), and a coherent beam combining (CBC) system, all of which are configured to modulate and amplify the laser beam;

[0264] Figure 7B A laser system according to some embodiments is schematically illustrated, the laser system including a seed laser device, an optical polarization beam combiner (OPC), a polarization beam splitter (PBS), and a master oscillator power amplifier (MOPA), all of which are configured to modulate an amplified laser beam;

[0265] Figure 8A An optical polarization beam combiner (OPC) according to some embodiments is schematically shown;

[0266] Figure 8B Another optical polarization beam combiner (OPC) according to some embodiments is schematically shown;

[0267] Figure 9 An example of a prior art fiber optic amplification system is illustrated schematically;

[0268] Figure 10A , Figure 10B , Figure 10C and Figure 10D A hybrid pump module according to various embodiments of the present invention is schematically illustrated;

[0269] Figure 11A , Figure 11B and Figure 11C A hybrid pumping module according to some embodiments of the present invention is schematically illustrated, wherein the core-related module is a seed-related module;

[0270] Figure 12A hybrid pump module according to some embodiments of the present invention is schematically shown, wherein the core related module is an output module;

[0271] Figure 13 A hybrid pumping module according to some embodiments of the present invention is schematically shown, wherein the core-related module is a high-reflectivity module;

[0272] Figure 14 A hybrid pumping module according to some embodiments of the present invention is schematically illustrated, wherein the core-related module is a local reflection module;

[0273] Figure 15 An optical fiber amplification system according to some embodiments of the present invention is illustrated schematically;

[0274] Figure 16A and Figure 16B A fiber laser system according to some embodiments of the present invention is illustrated schematically;

[0275] Figure 17A , Figure 17B and Figure 17C The illustration schematically shows several configurations of a device for frequency doubling a radiated laser beam according to some embodiments of the present invention;

[0276] Figure 18A The illustration schematically shows an example of temperature variation along the optical axis of a single crystal placed in an oven, which is configured for low-power frequency doubling but operates at high power, according to some embodiments of the invention.

[0277] Figure 18B An example illustrating the phase difference between the fundamental and harmonic beams accumulated at each point within the crystal;

[0278] Figure 19A , Figure 19B and Figure 19C This schematically illustrates the temperature retuning of the PFD after adding a second harmonic seed beam with a conjugate phase difference to achieve the goal of minimum MP and optimal temperature in the focusing region.

[0279] Figure 20A , Figure 20B and Figure 20C This presents a summary of a set of simulations performed using a 500W input beam and a 50mm seeder crystal;

[0280] Figure 21 The seeder beam profile at a non-resonant temperature is shown according to some embodiments of the present invention.

[0281] Figure 22A and Figure 22BSimulation results and comparisons of using and not using a seeder beam according to some embodiments of the present invention are shown.

[0282] Figure 23 This demonstrates the increased value of using a seeder beam according to some embodiments of the invention;

[0283] Figure 24 According to some embodiments of the present invention, the seeder beam provides a phase effect by presenting the relationship between the green output beam and the PMC rotation;

[0284] Figure 25A , Figure 25B and Figure 25C The illustrations schematically depict various configurations for a frequency multiplier device according to some embodiments of the present invention;

[0285] Figure 26A and Figure 26B The diagram schematically illustrates the rotation angle or tilt angle of the PMC according to some embodiments of the present invention. Figure 26A For the front view and Figure 26B This is a side view;

[0286] Figure 27 An optional feedback algorithm for continuously adjusting the rotation angle of the PMC is illustrated schematically according to some embodiments of the present invention;

[0287] Figure 28A and Figure 28B The illustrations schematically depict the changes in crystal temperature and frequency multiplier power over time due to undershoot / overshoot of the oven controller, according to some embodiments of the invention.

[0288] Figure 29 The diagram illustrates, according to some embodiments of the invention, the output power stabilization of a rotating PMC via jitter control, wherein the PMC is configured to overcome undershoot / overshoot of the oven;

[0289] Figure 30 Experimental results are shown for a jitter control with feedback according to some embodiments of the present invention, which is used to optimize the PMC angle after changes in operating conditions;

[0290] Figure 31A and Figure 31B This demonstrates experimental results showing that, according to some embodiments of the present invention, harmonic power is maintained at its maximum value while reducing fluctuations using static and dynamic PMC respectively;

[0291] Figure 32The power spectrum of the harmonic output is shown for one hour of operation with and without the use of a stabilization algorithm, according to some embodiments of the present invention.

[0292] Figure 33 The reverse conversion phase difference is schematically illustrated according to some embodiments of the present invention; and

[0293] Figure 34A and Figure 34B This illustrates, according to some embodiments of the present invention, by means of, Figure 34A A comparison between the rise time obtained by quickly switching on the laser as described in the example and the rise time obtained by switching the PMC position.

[0294] It should be understood that, for the sake of simplicity and clarity, the elements shown in the accompanying drawings are not necessarily drawn to scale. For example, the dimensions of some elements may be enlarged relative to others for clarity. Furthermore, where deemed appropriate, reference numerals may be repeated between drawings to indicate corresponding or similar elements. Detailed description of the invention

[0295] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, those skilled in the art will understand that the invention can be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the invention.

[0296] As used herein, in one embodiment, the term "about" means ±10%. In another embodiment, the term "about" means ±9%. In another embodiment, the term "about" means ±9%. In another embodiment, the term "about" means ±8%. In another embodiment, the term "about" means ±7%. In another embodiment, the term "about" means ±6%. In another embodiment, the term "about" means ±5%. In another embodiment, the term "about" means ±4%. In another embodiment, the term "about" means ±3%. In another embodiment, the term "about" means ±2%. In another embodiment, the term "about" means ±1%.

[0297] Methods and systems for modulating laser beams

[0298] This invention relates to methods and apparatus for manipulating and modulating laser beams from lasers, laser beam arrays, and fiber optic arrays. More specifically, the invention provides methods and apparatus for enabling the activation and deactivation of a laser beam while the laser system maintains its operating power, for example, without shutting down or reducing the system power source or blocking the seed laser beam. Thus, operating time is saved (reduced) without damaging components such as amplifiers, and by enabling higher operating frequencies (e.g., modulation frequencies up to 10 GHz).

[0299] U.S. Patent Application Publication 2013 / 0107343 discloses an example of a laser amplification system and a coherent beam combining (CBC) system. This disclosure illustrates a laser system comprising a seed laser and an optical amplification subsystem that receives the output of the seed laser and provides an amplified laser output. The optical amplification subsystem includes a first plurality of amplifier components, each of which includes a second plurality of optical amplifiers, and phase control circuitry including a phase modulation function associated with each of the first plurality of amplifier components.

[0300] Figure 1 This illustrates a general or typical model / design of coherent beam combining (CBC). System 1100 includes a seed laser 1110 configured to provide a seed beam to CBC system 1101. CBC system 1101 includes a first optical amplifier 1121 that receives the output of the seed laser 1110 and provides a first amplified output beam. A first beam splitter 1131 splits the first output beam into a first plurality of input beams to be received by a second plurality of optical amplifiers 1122 arranged in a parallel configuration. The second plurality of optical amplifiers 1122 are configured to provide a second plurality of amplified output beams. The second plurality of output beams are then split by the second plurality of beam splitters 1132, which provide a second plurality of input beams, which are received by a third plurality of optical amplifiers 1123 arranged in a parallel configuration to provide a third plurality of amplified output beams. The third plurality of amplified output beams are then coherently combined into a single CBC output beam 170. Coherent beam combining can be provided, for example, by at least one beam combiner 1140 configured to provide beam interference at a location marked CBC point 1171, thereby providing a CBC output beam. Alternatively, coherent beam combining can be provided in free space (collimated free space, without any beam combiner; not shown), where beam interference occurs at the location marked CBC point 1171.

[0301] The CBC system also includes a phase control circuit 1160 associated with each of the second plurality of input beams, which includes a phase modulation function 1150. The control circuit 1160 is configured to monitor beam interference at CBC point 1171 and control the phase of each of the second plurality of input beams via the plurality of phase modulators 1150, such that constructive beam interference is received at CBC point 1171. Note that all optical connections can be provided via optical fiber 1102. It should also be noted that optical amplifiers 1121, 1122, and 1123 can be configured to have the same or different intensities; the beam combiner 1140 can be as described in U.S. Publication 2013 / 0107343. Figure 4 A and Figure 4 Configure as described in section B.

[0302] Pulsed operation of a laser refers to any laser not classified as continuous-wave (CW), where optical power appears in pulses of a certain duration with a certain repetition rate. This use of laser waves encompasses a wide range of techniques to address many different motivations. Some lasers are pulsed simply because they cannot operate in continuous mode. In other cases, applications require the generation of pulses with the largest possible energy. Since pulse energy equals average power divided by the repetition rate, this can sometimes be achieved by reducing the pulse rate so that more energy can be accumulated between pulses. Other applications rely on peak pulse power (rather than the energy within the pulse), particularly for achieving nonlinear optical effects. For a given pulse energy, this requires forming pulses of the shortest possible duration. Quasi-continuous-wave (QCW) operation of a laser means that its pump source is "on" only for a specific time interval, short enough to significantly reduce thermal effects, but still long enough for the laser process to approach its steady state, i.e., the laser is optically in continuous-wave operation. The duty cycle (the percentage of the "on" time) can be, for example, several percentages, thus greatly reducing heating and all associated thermal effects such as thermal lensing and overheating damage. Therefore, QCW operation allows for operation with higher peak output power, but at the cost of lower average power. (Source: https: / / en.wikipedia.org / wiki / Pulsed_lase; see also: https: / / en.wikipedia.org / wiki / Wikipedia:Text of Creative Commons Attribution-ShareAlike 3.0 Unported License)

[0303] Those skilled in the art will understand that the term "fast optical modulator (FOM)" can refer to an electro-optic modulator (EOM) (or electro-optic modulator) configured to control the power, phase, or polarization of a laser beam with electronic control signals. In some embodiments, the operating principle can be based on the linear electro-optic effect (also known as the Pockels effect), i.e., by changing the refractive index of a nonlinear crystal in proportion to the electric field strength.

[0304] Those skilled in the art will understand that the term "one or more phase modulators" can refer to optical modulators that can be used to control the optical phase of a laser beam. Commonly used types of phase modulators are Pockels-based electro-optic modulators and liquid crystal modulators, but it is also possible to utilize, for example, changes in refractive index or length caused by heat in an optical fiber, or changes in length caused by stretching. Various phase modulators are used within the area of ​​an integrated optical device, where the modulated light propagates in a waveguide.

[0305] Those skilled in the art will understand that the term "one or more master oscillator power amplifiers (MOPAs)" can refer to a configuration that includes a master laser (or seed laser) and an optical amplifier to increase output power. In some embodiments, the power amplifier is an fiber optic device. According to other embodiments, the MOPA may include a solid-state bulk laser and a bulk amplifier, or it may include a tunable external cavity diode laser and a semiconductor optical amplifier.

[0306] Those skilled in the art will understand that the term "beam splitter" can refer to an optical device configured to split an incident beam (e.g., a laser beam) into two or more beams that may or may not have the same optical power. In some embodiments, a beam splitter is used as a beam combiner to combine several beams into a single beam. In some embodiments, a beam splitter is required for use in interferometers, autocorrelators, cameras, projectors, and laser systems. In some embodiments, a beam splitter may include at least one of the following:

[0307] - A dielectric mirror, which can be any localized reflector used to separate the beam. In laser technology, dielectric mirrors are commonly used for this purpose. The angle of incidence also determines the angular separation of the output beam, such as 45°, which is generally convenient, but it can also have other values ​​and affect the characteristics of the beam splitter. A wide range of power splitting ratios can be achieved through different designs of the dielectric coating.

[0308] - A cube, where beam splitting occurs at the interface within the cube. This cube is typically made of two triangular glass prisms bonded together with some kind of transparent resin or cement. The thickness of this layer can be used to adjust the power distribution ratio for a given wavelength.

[0309] - An optical fiber splitter, which is a type of optical fiber coupler that functions as an optical fiber bundler. Such a device can be made by fusion-bonding fibers and can have two or more output ports. For block devices, the split ratio may or may not strongly depend on the input wavelength and polarization.

[0310] - Planar optical wave circuit (PLC) splitter. A PLC is an optical integrated circuit (IC) or an optical circuit board that uses optical waveguides to route photons.

[0311] A grating is an optical component with a periodic structure that separates and diffracts light into several beams that propagate in different directions. The directions of these beams depend on the spacing of the gratings and the wavelength of the light. In some embodiments, the grating can also be used as a beam combiner.

[0312] - Multimode interference (MMI) is an optical waveguide with spatially inhomogeneous structures used to guide light, i.e., spatially inhomogeneous structures used to confine the spatial regions in which light can propagate. MMI can be used to separate and combine light beams, for example, in integrated optical interferometers.

[0313] Those skilled in the art will understand that the term "fiber optic coupler" or "coupler" can refer to a fiber optic device having one or more input fibers and one or more output fibers. Light from the input fibers may appear at one or more output ends, and the power distribution may depend on wavelength and polarization.

[0314] Those skilled in the art will understand that the term "splitter (tap)" can refer to a coupler configured for a coupling output ratio of 50:50, 75:25, 90:10, or 99:1. Fiber optic splicing can utilize network splicing methods that allow signals to be extracted from the fiber without disconnecting the connection. Fiber optic splicing allows certain signals transmitted in the optical core to be transferred to another fiber or detector.

[0315] Those skilled in the art will understand that the terms "beam interference" or "interference" can refer to the phenomenon where two or more light waves overlap to form a composite wave with a larger, lower, or the same amplitude. When the composite wave is greater than either of the two original waves, it is called "constructive interference"; when the sum of the two waves is less than either wave, or even equal to zero, it is called "destructive interference".

[0316] Those skilled in the art will understand that the term "optical amplifier" can refer to a device that receives some input signal and generates an output signal with high optical power. In some embodiments, the input and output are laser beams propagating in free space or optical fibers. Amplification occurs in a so-called gain medium, which must be "pumped" (i.e., provided with energy) from an external source. In some embodiments, the optical amplifier is optically, chemically, or electrically pumped.

[0317] Those skilled in the art will understand that the term "dichroic mirror" can refer to a mirror that has significantly different reflection or transmission characteristics at two different wavelengths.

[0318] Those skilled in the art will understand that the term "seed laser" can refer to a laser whose output is injected into an amplifier or another laser. Typical types of seed lasers are small laser diodes (single-frequency or gain-switched), short-cavity fiber lasers, and miniature solid-state lasers, such as non-planar ring oscillators (NPROs).

[0319] Now for reference Figure 2 This illustrates a laser system 1200 configured to provide and modulate a laser beam 1270 (more specifically, a high-power laser beam) according to some embodiments of the present invention. System 1200 includes:

[0320] - Coherent beam combining (CBC) system; and

[0321] - At least one seed laser device 1210, which is configured to provide at least one input seed beam to the CBC system 1201;

[0322] The output laser beam 1270 is selectively provided by the CBC system.

[0323] In some embodiments of the invention, components of the CBC system can be provided in many different designs and configurations, some of which are known in the art, such as... Figure 1 The CBC system 1101 shown is a non-limiting example, or for example... Figure 2 Another non-limiting example of the CBC system 1201 shown, the components of the CBC system include:

[0324] - A plurality of phase modulators 1250, configured (e.g., via optical fiber) to be directly or indirectly optically connected 1202 to: a seed beam provided by a seed laser device, a plurality of optical amplifiers 1220, at least one beam splitter 1230, and optionally at least one beam combiner 1240 (which can provide coherent beam combining without any beam combiner, e.g., collimated free space; not shown), all arranged to enable constructive or destructive beam interference at CBC point 1271; and

[0325] - At least one control circuit 1260 is configured to monitor beam interference at CBC point 1271 and accordingly control at least one phase modulator in phase modulator 1250 to provide constructive or destructive beam interference.

[0326] In some embodiments, the laser system 1200 is configured to provide rapid and efficient modulation of the output laser beam 1270 according to the following method:

[0327] ■ In order to activate the laser beam 1270 (in other words, when the laser beam 1270 needs to be “turned on”), the phase modulator 1250 is controlled via the control circuit 1260 to enable constructive interference at the CBC point 1271, thereby providing the output laser beam 1270.

[0328] ■ In order to deactivate the laser beam 1270 (in other words, when it is necessary to “turn off” the laser beam 1270), the phase modulator 1250 is controlled via the control circuit 1260 to enable destructive interference at the CBC point 1271, thereby blocking the output laser beam 1270.

[0329] In some embodiments, controlling the phase modulator to enable constructive interference includes tuning the phase modulator to provide a laser beam with maximum intensity at CBC point 1271.

[0330] - In some related embodiments, controlling the phase modulator to enable destructive interference includes controlling half of the previously tuned phase modulators 1250 to provide maximum beam intensity to add half a phase (π) to the beams they were previously tuned to.

[0331] -According to other related embodiments, controlling the phase modulator to enable destructive interference includes modifying some of the phase modulators 1250 that were previously tuned to provide maximum beam intensity; the modifications may be the same as or different from each other.

[0332] - In some embodiments, constructive interference is considered if the laser intensity is greater than 50% of the maximum intensity; wherein, constructive interference is preferably considered if the laser intensity is approximately 100% of the maximum intensity. In some embodiments, destructive interference is considered if the laser intensity is equal to or less than 50% of the maximum intensity; wherein, destructive interference is preferably considered if the laser intensity is approximately 0% of the maximum intensity.

[0333] In some other related embodiments, the method further includes the step of tuning the laser beam 1270 by modifying some of the phase modulators tuned to provide maximum beam intensity (via controller 1260), wherein the modification is configured to make the intensity of the output laser beam 1270 equal to a predetermined percentage range (e.g., 5%, 10%, 25%, 50%, 75%, 90%, 95%, or any other percentage) between 0% and 100% of the previously provided maximum intensity.

[0334] In some embodiments, controlling the phase modulator via controller 1260 to enable destructive interference includes modifying the phase modulator at CBC point 1271 to provide a laser beam with minimum intensity.

[0335] Now for reference Figure 3 This illustrates another laser system 1300 configured to provide and modulate a laser beam 1370 (more specifically, a high-power laser beam) according to some embodiments of the present invention. System 1300 includes:

[0336] -At least one seed laser device 1310;

[0337] - Fast optical modulator (FOM) 1316, which is configured to receive a seed laser beam from a seed laser device and modulate its bandwidth;

[0338] - Coherent beam combining (CBC) system 1301, which is configured to receive a modulated seed beam and accordingly provide an amplified laser beam 1370.

[0339] In some embodiments, FOM 1316 modulation is configured to select a first bandwidth (Δω1) or a second bandwidth (Δω2) between two predetermined bandwidths, wherein the second bandwidth is greater than the first bandwidth (Δω2>Δω1).

[0340] In some embodiments, a first bandwidth (Δω1) is selected such that its coherence length Lc1 is longer than the root mean square (RMS) of the optical path difference (OPD) between different channels in the system, Lc1 > OPD; and wherein a second bandwidth (Δω2) is selected such that its coherence length Lc2 is shorter than the RMS of the OPD between different channels in the system, Lc2 <OPD。

[0341] In some embodiments of the invention, components of the CBC system can be provided in many different designs and configurations, some of which are known in the art, such as... Figure 1 The CBC system 1101 shown is a non-limiting example, or for example... Figure 3 Another non-limiting example of the CBC system 1301 shown, the components of the CBC system include:

[0342] - A plurality of phase modulators 1350, configured, for example, via optical fiber, to be directly or indirectly optically connected to: a seed beam provided by a seed laser device 1310, a plurality of optical amplifiers 1320, at least one beam splitter 1330, and optionally at least one beam combiner 1340 (which can provide beam combining without any beam combiner, for example, collimated free space; not shown), all arranged to enable constructive or destructive beam interference at CBC point 1371; and

[0343] - At least one control circuit 1360 is configured to monitor beam interference at CBC point 1371 and accordingly control at least one of the phase modulators 1350 to provide constructive or destructive beam interference.

[0344] In some embodiments, the laser system 1300 is configured to provide rapid and efficient modulation of the output laser beam 1370 according to the following method:

[0345] ■ In order to activate the laser beam 1370, the FOM 1316 is controlled to provide a seed laser beam with a narrow bandwidth (Δω1) configured to enable constructive interference at the CBC point 1371, thereby providing the output laser beam 1370;

[0346] ■ In order to deactivate the laser beam 1370, the FOM 1316 is controlled to provide a seed laser beam with a wide bandwidth (Δω2, where Δω2>Δω1) at the CBC point 1371, which is configured to disable constructive interference, thereby blocking the output laser beam 1370.

[0347] In some embodiments, the step of controlling FOM 1316 to provide a seed laser beam with a narrow bandwidth further includes controlling phase modulator 1350 via control circuit 1360 to enable constructive interference at CBC point 1371.

[0348] In some embodiments, the step of controlling the phase modulator to provide constructive beam interference includes tuning the phase modulator to provide constructive beam interference with maximum intensity.

[0349] In some embodiments, constructive interference is considered if the laser intensity is greater than 50% of the maximum intensity; wherein, constructive interference is preferably considered if the laser intensity is approximately 100% of the maximum intensity. In some embodiments, destructive interference is considered if the laser intensity is equal to or less than 50% of the maximum intensity; wherein, destructive interference is preferably considered if the laser intensity is approximately 0% of the maximum intensity.

[0350] In some embodiments, control of the FOM 1316 is provided by at least one control circuit 1360 of the CBC system 1301. According to other embodiments, control of the FOM 1316 is provided by an advanced control circuit 1361 configured to control both the FOM 1316 and at least one control circuit 1360 of the CBC system 1301.

[0351] Now for reference Figure 4 This illustrates another laser system 1400 configured to provide and modulate a laser beam 1470 (more specifically, a high-power laser beam) according to some embodiments of the present invention. System 1400 includes:

[0352] - Coherent beam combining (CBC) system 1401, which is configured to receive a seed laser beam and accordingly provide an amplified laser beam 1470;

[0353] - First seed laser device 1410, which is configured to provide a first seed beam having a first wavelength (λ1);

[0354] - A second seed laser device 1411 configured to provide a second seed beam having a second wavelength (λ2) different from the first wavelength (λ2≠λ1); and - an optical switch 1415 configured to link only one of the first and second seed laser beams to the CBC system 1401.

[0355] Therefore, the output laser beam 1470 is provided by the CBC system 1401.

[0356] In some embodiments of the invention, components of the CBC system can be provided in many different designs and configurations, some of which are known in the art, such as... Figure 1 The CBC system 1101 shown is a non-limiting example, or for example... Figure 4 Another non-limiting example of the CBC system 1401 shown, the components of the CBC system include:

[0357] - A plurality of phase modulators 1450, which are configured (e.g., via optical fiber) to be directly or indirectly optically connected to: linked (first or second)

[0358] A seed laser beam, multiple optical amplifiers 1420, at least one beam splitter 1430, and optionally at least one beam combiner 1440 (which can provide beam combining without any beam combiner, e.g., collimated free space; not shown) are all arranged to enable constructive beam interference at CBC point 1471; and

[0359] - At least one control circuit 1460, configured to monitor beam interference at CBC point 1471 and accordingly control at least one phase modulator among the phase modulators.

[0360] In some embodiments, if the phase modulator 1450 is tuned to allow constructive interference based on the first wavelength (λ1), the second wavelength (λ2) is selected such that it cannot provide constructive beam interference at the CBC point 1471.

[0361] In some embodiments, at least one beam combiner 1440 is a wavelength-sensitive diffractive optical element (DOE) configured to combine a beam having a specific wavelength (i.e., a first wavelength (λ1)) and to scatter beams having other wavelengths (including a second wavelength (λ2)). A non-limiting example of such a beam combiner is a Damman grating, where the optimal angle between the combined beams is highly sensitive to wavelength. Thus, the beams are arranged to achieve maximum combining efficiency for a first seed laser beam having the first wavelength (λ1). Therefore, when the seed laser beam is switched to a second laser beam having the second wavelength (λ2, where λ2 ≠ λ1), the combining efficiency decreases, and thus the output beam 1470 is disabled.

[0362] In some embodiments, the laser system 1400 is configured to provide rapid and efficient modulation of the output laser beam 1470 according to the following method:

[0363] ■ In order to activate the laser beam 1470, the optical switch 1415 is controlled to link the first seed beam to the CBC system 1401, and the phase modulator 1450 is controlled via the control circuit 1460 to enable constructive interference at the CBC point 1471, thereby providing the output laser beam 1470.

[0364] ■ In order to deactivate the laser beam 1470, the optical switch 1415 is controlled to link the second seed beam to the CBC system 1401 (without modifying the phase modulator 1450), thereby disabling constructive interference at the CBC point 1471 and preventing the output laser beam 1470 from being output.

[0365] Note that, for illustrative purposes, after activating laser beam 1470, phase modulator 1450 is tuned to enable constructive interference at CBC point 1471 based on the first wavelength (λ1) of the first seed laser beam 1410. Therefore, when optical switch 1415 is linked with a second seed laser beam having a second wavelength (λ2, λ2 ≠ λ1), phase modulator 1450 is not readjusted, and thus no constructive interference occurs, and it is disabled. Therefore, when optical switch 1415 is linked again with the first seed laser beam having the first wavelength (λ1), phase modulator 1450 has been adjusted.

[0366] In some embodiments, according to the above embodiments and their selected features, λ1 and λ2 are selected such that their difference (λ2≠λ1) allows the beam to be activated and deactivated.

[0367] In some embodiments, the step of controlling the phase modulator 1450 to provide a lengthwise beam interference includes tuning the phase modulator to provide a lengthwise beam interference with maximum intensity.

[0368] In some embodiments, constructive interference is considered if the laser intensity is greater than 50% of the maximum intensity; wherein, constructive interference is preferably considered if the laser intensity is approximately 100% of the maximum intensity. In some embodiments, destructive interference is considered if the laser intensity is equal to or less than 50% of the maximum intensity; wherein, destructive interference is preferably considered if the laser intensity is approximately 0% of the maximum intensity.

[0369] In some embodiments, control of the optical switch 1415 is provided by at least one control circuit 1460 of the CBC system 1401. According to other embodiments, control of the optical switch 1415 is provided by an advanced control circuit 1461 configured to control both the optical switch 1415 and at least one control circuit 1460 of the CBC system 1401.

[0370] Now for reference Figure 5 This illustrates a laser system 1500 configured to provide and modulate a laser beam 1570 (more specifically, a high-power laser beam) according to some embodiments of the present invention. System 1500 includes:

[0371] - Coherent beam combining (CBC) system 1501, which is configured to receive a seed laser beam and accordingly provide an amplified laser beam;

[0372] - First seed laser device 1510, which is configured to provide a first seed laser beam with a narrow bandwidth (Δω1);

[0373] - A second seed laser device 1511, configured to provide a second seed laser beam with a wide bandwidth (Δω2) greater than that of a first laser (where Δω2 > Δω1); and

[0374] - Optical switch 1515, which is configured to link only one of the first seed laser beam and the second seed laser beam to CBC system 1501;

[0375] - Wherein, a narrow bandwidth (Δω1) is configured to enable phase length beam interference at CBC point 1571 of CBC system 1501, and a wide bandwidth (Δω2) is configured to disable phase length beam interference at CBC point 1571; therefore, the output laser beam 1570 is provided by CBC system 1501.

[0376] In some embodiments, a first bandwidth (Δω1) is selected such that its coherence length Lc1 is longer than the RMS of the optical path difference (OPD) between different channels in the system, Lc1 > OPD; and wherein a second bandwidth (Δω2) is selected such that its coherence length Lc2 is shorter than the RMS of the OPD between different channels in the system, Lc2 <OPD。

[0377] In some embodiments of the invention, components of the CBC system can be provided in many different designs and configurations, some of which are known in the art, such as... Figure 1 The CBC system 1101 shown is a non-limiting example, or for example... Figure 5 Another non-limiting example of the CBC system 1501 shown, the components of the CBC system include:

[0378] - A plurality of phase modulators 1550, which are configured (e.g., via optical fiber) to be directly or indirectly optically connected to the following: linked (first or second).

[0379] A seed laser beam, multiple optical amplifiers 1520, at least one beam splitter 1530, and optionally at least one beam combiner 1540 (which can provide beam combining without any beam combiner, e.g., collimated free space; not shown) are all arranged to enable constructive beam interference at CBC point 1571; and

[0380] - At least one control circuit 1560, configured to monitor beam interference at CBC point 1571 and control at least one phase modulator in the phase modulator accordingly.

[0381] In some embodiments, the laser system 1500 is configured to provide rapid and efficient modulation of the output laser beam 1570 according to the following method:

[0382] ■ In order to activate the laser beam 1570, the optical switch 1515 is controlled to link the first seed laser beam to the CBC system 1501, thereby enabling constructive interference at the CBC point 1571 and providing the output laser beam 1570.

[0383] ■ In order to deactivate the laser beam 1570, the optical switch 1515 is controlled to link the second seed laser beam to the CBC system 1501, thereby disabling constructive interference at the CBC point 1571 and preventing the output laser beam 1570 from being output.

[0384] In some embodiments, the activation step further includes controlling the phase modulator 1550 via the controller 1560 to enable constructive interference at the CBC point 1571.

[0385] In some embodiments, the step of controlling the phase modulator 1550 to provide a lengthwise beam interference includes tuning the phase modulator to provide a lengthwise beam interference with maximum intensity.

[0386] In some embodiments, constructive interference is considered if the laser intensity is greater than 50% of the maximum intensity; wherein, constructive interference is preferably considered if the laser intensity is approximately 100% of the maximum intensity. In some embodiments, destructive interference is considered if the laser intensity is equal to or less than 50% of the maximum intensity; wherein, destructive interference is preferably considered if the laser intensity is approximately 0% of the maximum intensity.

[0387] In some embodiments, control of the optical switch 1515 is provided by at least one control circuit 1560 of the CBC system 1501. According to other embodiments, control of the optical switch 1515 is provided by an advanced control circuit 1561 configured to control both the optical switch 1515 and at least one control circuit 1560 of the CBC system 1501.

[0388] Now for reference Figure 6A and Figure 6C These illustrate laser systems 1600A / 1600C configured to provide and modulate laser beams 1670A / 1670C (more specifically, high-power laser beams) according to some embodiments of the invention.

[0389] like Figure 6A As shown, system 1600A includes:

[0390] - Coherent beam combining (CBC) system 1601A, which is configured to receive a seed beam and provide an amplified laser beam 1672A;

[0391] - First seed laser 1610, which is configured to provide a first seed beam having a first wavelength (λ1);

[0392] - Second seed laser 1611, the second seed laser being configured to provide a second seed beam having a second wavelength (λ2) different from the first wavelength (λ2≠λ1);

[0393] - Optical switch 1615, configured to link only one of the first seed beam and the second seed beam to CBC system 1601A; and

[0394] - Dichroic mirror 1680A, which is configured to receive amplified laser beam 1672A.

[0395] A beam with a first wavelength (λ1) is transmitted to the output of the laser system 1600A and a beam with a second wavelength (λ2) is reflected, thus selectively providing an output laser beam 1670A.

[0396] In some embodiments, the first wavelength (λ1), the second wavelength (λ2), and the dichroic mirror 1680A are selected such that when the first wavelength (λ1) is present, the dichroic mirror 1680A transmits more than 50% (preferably about 100%) of the light beam; and when the second wavelength (λ2) is present, it reflects more than 50% (preferably about 100%) of the light beam.

[0397] like Figure 6C As shown, system 1600C includes:

[0398] - Coherent beam combining (CBC) system 1601C, which is configured to receive a seed beam and provide an amplified laser beam 1672C;

[0399] - First seed laser 1610, which is configured to provide a first seed beam having a first wavelength (λ1);

[0400] - Second seed laser 1611, the second seed laser being configured to provide a second seed beam having a second wavelength (λ2) different from the first wavelength (λ2≠λ1);

[0401] - Optical switch 1615, configured to link only one of the first seed beam and the second seed beam to CBC system 1601C; and

[0402] - A dichroic mirror 1680C is configured to receive an amplified laser beam 1672C, transmit a beam with a first wavelength (λ1) to the output of the laser system 1600C, and reflect a beam with a second wavelength (λ2), thus selectively providing the output laser beam 1670C.

[0403] In some embodiments, the first wavelength (λ1), the second wavelength (λ2), and the dichroic mirror 1680C are selected such that when the first wavelength (λ1) is present, the dichroic mirror 1680A transmits more than 50% (preferably about 100%) of the light beam; and when the second wavelength (λ2) is present, it reflects more than 50% (preferably about 100%) of the light beam.

[0404] In some embodiments of the invention, components of the CBC system can be provided in many different designs and configurations, some of which are known in the art, such as... Figure 1 The CBC system 1101 shown is a non-limiting example, or for example... Figure 6A Another non-limiting example of the CBC system 1601A shown, the components of the CBC system include:

[0405] - A plurality of phase modulators 1650, which are configured to be optically connected (directly or indirectly) to: a linked (first or second) seed beam, a plurality of optical amplifiers 1620, at least one beam splitter 1630, and optionally at least one beam combiner 1640; all of the above are arranged to enable phase length beam interference at CBC point 1671A.

[0406] as well as

[0407] - At least one control circuit 1660, configured to monitor beam interference at CBC point 1671A and accordingly control at least one phase modulator among the phase modulators.

[0408] In some embodiments, for such Figure 6A The CBC system configuration 1601A shown includes at least one beam combiner 1640, which can place a dichroic mirror 1680A outside the CBC point 1671A. In some embodiments, the dichroic mirror 1680A can be placed before the CBC point.

[0409] According to other embodiments of the present invention, the CBC system is configured as follows: 1601C Figure 6C As shown, it includes:

[0410] - A plurality of phase modulators 1650, configured to be optically connected (directly or indirectly) to: a linked (first or second) seed beam, a plurality of optical amplifiers 1620, at least one beam splitter 1630, and wherein beam combining is configured to occur in free space; all of the above are arranged to enable constructive beam interference at a CBC point 1671A, which is set in the far field in this illustration; and

[0411] - At least one control circuit 1660, configured to monitor beam interference at CBC point 1671C and accordingly control at least one phase modulator among the phase modulators.

[0412] according to Figure 6C In the embodiment shown, the dichroic mirror 1680C is placed before the CBC point 1671C.

[0413] In some embodiments, Figure 6A and Figure 6C The two laser systems 1600A / 1600C shown are configured to provide rapid and efficient modulation of the output laser beam 1670A / 1670C according to the following methods:

[0414] ■ In order to activate the laser beam 1670A / 1670C, the optical switch 1615 is controlled to link the first seed laser beam to the CBC system 1601A / 1601C, thereby transmitting and providing the output laser beam 1670A / 1670C.

[0415] ■ In order to deactivate the laser beam 1670A / 1670C, the optical switch 1615 is controlled to link the second seed laser beam to the CBC system 1601A / 1601C, thereby reflecting and preventing the output laser beam 1670A / 1670C from being emitted.

[0416] In some embodiments, the method further includes the step of controlling a phase modulator 1650 via a control circuit 1660 to enable constructive interference at CBC points 1671A / 1671C. In some embodiments, the step of controlling the phase modulator may be performed only during the step of activating the laser beam, and phase modulation may not be performed during deactivation.

[0417] In some embodiments, controlling the phase modulator 1650 to provide constructive beam interference includes tuning the phase modulator to provide constructive beam interference with maximum intensity.

[0418] In some embodiments, constructive interference is considered if the laser intensity is greater than 50% of the maximum intensity; wherein, constructive interference is preferably considered if the laser intensity is approximately 100% of the maximum intensity. In some embodiments, destructive interference is considered if the laser intensity is equal to or less than 50% of the maximum intensity; wherein, destructive interference is preferably considered if the laser intensity is approximately 0% of the maximum intensity.

[0419] In some embodiments, control of the optical switch 1615 is provided by at least one control circuit 1660 of the CBC system 1601A / 1601C. According to other embodiments, control of the optical switch 1615 is provided by an advanced control circuit 1661 configured to control both the optical switch 1615 and at least one control circuit 1660 of the CBC system 1601A / 1601C.

[0420] Now for reference Figure 6B This illustrates a laser system 1600B configured to provide and modulate a laser beam 1670B. System 1600B includes:

[0421] - Master Oscillator Power Amplifier (MOPA) 1620B, which is configured to receive a seed beam and provide an amplified laser beam 1672B;

[0422] - First seed laser 1610B, the first seed laser being configured to provide a first seed laser beam having a first wavelength (λ1);

[0423] - Second seed laser 1611B, the second seed laser being configured to provide a second seed laser beam having a second wavelength (λ2) different from the first wavelength (λ2≠λ1);

[0424] - Optical switch 1615B, configured to link only one of the first and second seed laser beams to MOPA 1620B; and

[0425] - A dichroic mirror 1680B is configured to receive an amplified laser beam 1672B, transmit a beam with a first wavelength (λ1) to the output of the laser system 1600B, and reflect a beam with a second wavelength (λ2), thus selectively providing the output laser beam 1670B.

[0426] Laser system 1600B is configured to provide rapid and efficient modulation of the output laser beam 1670B according to the following methods, including:

[0427] ■ In order to activate the laser beam 1670B, the optical switch 1615B is controlled to link the first seed beam to the MOPA 1620B, thereby transmitting and providing the laser beam 1670B.

[0428] ■ In order to deactivate the laser beam 1670B, the optical switch 1615B is controlled to link the second seed beam to the MOPA 1620B, thereby reflecting and avoiding the laser beam 1670B.

[0429] In some embodiments, according to the above embodiments and their selected features, λ1 and λ2 are selected such that their difference (λ2≠λ1) enables beam activation and deactivation.

[0430] Now for reference Figure 7A This illustrates a laser system 1700A configured to provide and modulate a laser beam 1770 (more specifically, a high-power laser beam) according to some embodiments of the present invention. System 1700A includes:

[0431] -At least one seed laser device 1710;

[0432] - Optical polarization beam combiner (OPC) 1717, which is configured to receive a seed laser beam from a seed laser device and modulate its polarization direction (its output beam is indicated by reference numeral 1718); wherein the modulation includes providing at least two polarization components to the seed beam, wherein one of the polarization components includes a predetermined polarization direction (P1).

[0433] - A coherent beam combining (CBC) system 1701, configured to receive a polarization-modulated seed laser beam 1718 and provide an amplified laser beam 1772; and

[0434] - Polarization beam splitter (PBS) 1790, which is configured to receive the amplified laser beam 1772 and transmit only the beam with a predetermined polarization direction (P1) to the output of the laser system 1700A, and reflect the beam with another polarization direction, thus selectively providing the laser beam 1770.

[0435] Therefore, the output laser beam 1770 is provided via the CBC system 1701.

[0436] In some embodiments of the invention, components of the CBC system can be provided in many different designs and configurations, some of which are known in the art, such as... Figure 1 The CBC system 1101 shown is a non-limiting example, or for example... Figure 7A Another non-limiting example of the CBC system 1701 shown includes components of:

[0437] - A plurality of phase modulators 1750, which are configured to be optically connected (directly or indirectly) to: a polarization-modulated seed beam 1718, a plurality of optical amplifiers 1720, at least one beam splitter 1730, and optionally at least one beam combiner 1740.

[0438] All of the above are configured to enable constructive beam interference at point CBC 1771; and

[0439] - At least one control circuit 1760, configured to monitor beam interference at CBC point 1771 and accordingly control at least one phase modulator among the phase modulators.

[0440] In some embodiments, the laser system 1700A is configured to provide rapid and efficient modulation of the output laser beam 1770 according to the following method:

[0441] ● In order to activate the laser beam 1770, OPC 1717 is controlled to provide a beam component having a predetermined polarization direction (P1) and an intensity (I1) greater than 50% (preferably about 100%) of the total intensity of the seed laser beam, thereby providing the output laser beam 1770.

[0442] • To deactivate the laser beam 1770, OPC 1717 is controlled to provide a beam component with a predetermined polarization direction (P1) and an intensity (I1) equal to or less than 50% (preferably about 0%) of the total intensity of the seed laser beam, thereby preventing the output laser beam 1770 from being deactivated.

[0443] In some embodiments, the method further includes the step of: tuning the laser beam by controlling the OPC 1717 to provide a beam component having a predetermined polarization direction (P1) and an intensity (I1) equal to a predetermined percentage of the total intensity of the seed laser beam.

[0444] In some embodiments, the method further includes the step of controlling a phase modulator 1750 via a control circuit 1760 to enable constructive interference at a CBC point 1771. In some embodiments, the step of controlling the phase modulator may be performed only during the step of activating the laser beam, and no modulation may be performed during the deactivation period.

[0445] In some embodiments, controlling the phase modulator 1750 to provide constructive beam interference includes tuning the phase modulator to provide constructive beam interference with maximum intensity.

[0446] In some embodiments, constructive interference is considered if the laser intensity is greater than 50% of the maximum intensity; wherein, constructive interference is preferably considered if the laser intensity is approximately 100% of the maximum intensity. In some embodiments, destructive interference is considered if the laser intensity is equal to or less than 50% of the maximum intensity; wherein, destructive interference is preferably considered if the laser intensity is approximately 0% of the maximum intensity.

[0447] In some embodiments, and as Figure 8A and Figure 8B As shown, the optical polarization beam combiner (OPC) 1717 includes:

[0448] - Beam splitter 1820, which is configured to receive an input beam having a first polarization direction (P1) and output a first beam (B1(I1,P1)) having a first polarization direction (P1) and a first intensity (I1) and a second beam (B2(I2,P1)) having a first polarization direction (P1) and a second intensity (I2), wherein the sum of the first intensity and the second intensity (I1+I2) is equal to the intensity of the input seed beam;

[0449] - Polarization converter 1830, configured to receive one (B1 or B2) of the output beam from beam splitter 1820 and convert its polarization; from S to P, or from P to S, therefore P1 ≠ P2; for example, in the case where the polarization of B2 is converted (such as... Figure 8A and Figure 8B (As shown), B1(I1, P1) and B2(I2, P2); and for example, in the case where the polarization of B1 has been changed (not shown), B1(I1, P2) and B1(I2, P1); and

[0450] - Polarization beam splitter (PBS) 1840A (e.g.) Figure 8A As shown), the polarization beam splitter is configured to receive a first output beam (B1(I1, P1)) and a second converted output beam (B2(I2, P2)), and combine (superimpose) them into a third beam, which is provided as an input to the CBC system 1701; or, the coupler 1840B (as shown) Figure 8B As shown, the coupler is configured to receive a first output beam (B1(I1, P1)) and a second converted output beam (B2(I2, P2)), combine (superimpose) them, and then split them into two output beams, wherein only one of the two output beams is provided as an input to the CBC system 1701. In some embodiments, the other output beam may be used by another system.

[0451] In some embodiments, the beam splitter assembly 1820 includes:

[0452] - Beam splitter 1821, which is configured to receive an input beam and split the input beam into two output beams; in some embodiments, the relationship between the intensities of the two output beams is constant.

[0453] - Phase modulator 1822, which is configured to modulate the phase of one of two beams;

[0454] - Coupler 1823, configured to receive two beams (after modulating the phase of one of the beams) and provide their interference at two positions 1823A and 1823B, thereby providing a first output beam (B1(I1, P1)) and a second output beam (B2).

[0455] (I2, P1));

[0456] - An electronic controller 1826 is configured to monitor one of two interference positions 1823A via a beam splitter 1824 and a diode 1825, and control a phase modulator 1822 to correspondingly enable constructive or destructive beam interference at the monitored position 1823A, wherein destructive or constructive beam interference is thereby provided to the non-monitored interference position 1823B; thereby determining a first intensity (I1);

[0457] Furthermore, the method steps for controlling OPC 1717 include controlling phase modulator 1822 (via controller 1826).

[0458] In some embodiments, control of the OPC 1717 is provided by at least one control circuit 1760 of the CBC system 1701. According to other embodiments, control of the optical switch 1717 is provided by an advanced control circuit 1761 configured to control both the optical switch 1717 and at least one control circuit 1760 of the CBC system 1701.

[0459] Now for reference Figure 7B This illustrates a laser system 1700B configured to provide and modulate a laser beam 1770B according to some embodiments of the present invention. System 1700B includes:

[0460] - Seed laser device 1710B;

[0461] - Optical polarization beam combiner (OPC) 1717, which is configured to receive a seed laser beam from a seed laser device and modulate its polarization direction (its output beam is indicated by reference numeral 1718B); wherein the modulation includes providing at least two polarization components to the seed beam, wherein one of the polarization components includes a predetermined polarization direction (P1).

[0462] - Master Oscillator Power Amplifier (MOPA) 1720B, which is configured to receive a seed beam and provide an amplified laser beam 1772B; and

[0463] - Polarization beam splitter (PBS) 1790B, which is configured to receive the amplified laser beam 1772B and transmit only the beam with a predetermined polarization direction (P1) to the output of the laser system 1700B, and reflect the beam with another polarization direction, thus selectively providing the output laser beam 1770B.

[0464] Laser system 1700B is configured to provide rapid and efficient modulation of the output laser beam 1770B according to the following methods, including:

[0465] ■ In order to activate the laser beam 1770B, OPC 1717 is controlled to provide a beam component having a predetermined polarization direction (P1) and an intensity (I1) greater than 50% (preferably about 100%) of the total intensity of the beam, thereby providing the laser beam 1770B;

[0466] ■ In order to deactivate the laser beam 1770B, OPC 1717 is controlled to provide a beam component with a predetermined polarization direction (P1) and an intensity (I1) equal to or less than 50% (preferably about 0%) of the total intensity of the beam, thereby avoiding the laser beam 1770B.

[0467] It should be noted that all embodiments of the present invention provide a laser modulation method and / or system that keeps the seed laser and CBC system (and its various components) active during both modulation states (beam “on” / beam “off”), thereby preventing any damage that may be caused by the seed beam being “off” or “blocked”, as described in the background.

[0468] In some embodiments of the present invention, the laser modulation methods and / or systems 1200, 1300, 1400, 1500, 1600A, 1600B, 1600C, 1700A, 1700B described above can be controlled via their controllers and, depending on the limitations of the switching elements, can be used for quasi-continuous wave (QCW) operation of laser devices at very high frequencies up to tens of GHz (e.g., 10 MHz, 100 MHz, 1 GHz, 10 GHz, 100 GHz, and any combination thereof). In some embodiments of the present invention, the laser modulation method and / or system 1200, 1300, 1400, 1500, 1600A, 1600B, 1600C, 1700A, 1700B described above can be controlled via their controller and can be used for quasi-continuous wave (QCW) operation of the laser device at various duty cycles ranging from 0% to 100% (e.g., 1%, 5%, 10%, 25%, 50%, 75%, 95%, 99% and any combination thereof).

[0469] In some embodiments of the present invention, at least some of the methods described above using systems 1200, 1300, 1400, 1500, 1600A, 1600B, 1600C, 1700A, and 1700B can be combined into a laser system to achieve more flexible operation of the laser beam.

[0470] Hybrid fiber-coupled diode-pumped laser module

[0471] In some embodiments, the present invention relates to methods and apparatuses configured to provide an optical signal amplifier and, more specifically, to provide a hybrid fiber-coupled diode-pumped laser module (and, in short, a hybrid pump module) configured to be coupled to an optical fiber. Those skilled in the art will understand that, according to some embodiments, the term "hybrid" can refer to a combination of pumping and signaling.

[0472] Those skilled in the art will understand that the fiber optic amplification system is configured to absorb and couple energy from several multimode pumps and typically a single-mode seed device, and amplify it to output a high-power single-mode beam.

[0473] Figure 9This illustrates a general or typical model / design of an optical fiber amplification system. The optical fiber amplification system 2100 includes: a seed lasing device 2110, which is connected via optical fibers (marked with a line and a fusion point symbol x) to an amplifier 2120, an isolator 2130, a beam splitter element 2140, and a monitor 2141, all serving as inputs to a multimode combiner (MMC) 2170, and a mode field adapter (MFA) 2150. This MMC is configured to combine the fibers of six pump modules 2160 with one fiber originating from the seed device into an active optical fiber 2180. The active optical fiber is configured to receive the input signal and generate an output signal with higher optical power. As shown, the active optical fiber is connected at a first end to the MMC (as described above) and at a second end to a pump dump 2190, which is configured to dump the remaining pump power and scattered signal into the cladding. The system output is typically achieved via an output optical fiber with an end cap 2191. As shown in the figure, the use of optical fiber to transmit the beam requires multiple fusion splices 2192, which are marked with the "x" symbol.

[0474] Those skilled in the art will understand that the aforementioned "fusion splice" is also referred to as a fusion joint. Those skilled in the art will understand that fusion splicing is the act of connecting two optical fibers end-to-end using heat. The aim is to fuse the two optical fibers together so that light passing through the fibers is not scattered or reflected back by the joint, and to make the joint and its surrounding area almost as robust as the original fiber itself. Before removing the spliced ​​fiber from the fusion splicer, verification tests are performed to ensure that the joint is robust enough to withstand handling, packaging, and long-term use. Exposed fiber areas can be protected by recoating or using a joint protector. Therefore, there is a need for an optical fiber amplification system that can reduce the number of fusion splices, thereby reducing energy loss and production costs.

[0475] Those skilled in the art will understand that the term "multimode combiner (MMC)" can refer to an optical component configured to combine several optical fibers into a single optical fiber (in... Figure 9 In the example: six pump-connected fibers + one seed-connected fiber), it is compatible with fiber amplifiers, allowing light from the pump module to enter the cladding and light from the seed to enter the core. MMCs are complex devices (e.g., requiring special functions for heat dissipation) and are therefore expensive.

[0476] Those skilled in the art will understand that, according to some embodiments, the term "fiber amplifier" or "active fiber amplifier" can refer to a doped fiber (e.g., an fiber that receives power from several pump modules and seed modules) Figure 9The system consists of six multimode beams plus one single-mode beam, outputting a single-mode beam with an enhanced effect (attributed to the single-mode seed). The overall diameter can be approximately 400 micrometers, with the core diameter being approximately 20 micrometers. Light from the pump module enters the cladding, while light from the seed enters the core. For example, fiber amplifiers are based on “active” fibers with a core doped with laser active ions such as Er3+, Nd3+, or Yb3+. Typically, in addition to the input signal light, the fiber coupler is used to introduce some “pump light.” This pump light is absorbed by the laser active ions, converting it into an excited electronic state, thus allowing amplification of other wavelengths of light via stimulated emission.

[0477] Those skilled in the art will understand that, according to some embodiments of the invention, the term "pump dump" can refer to a beam dump, which is a device designed to absorb or deflect residual unabsorbed pump power or scattered signals in the cladding. For Figure 9 For example, the emission is absorbed and retained in the cladding of the active fiber.

[0478] Those skilled in the art will understand that, according to some embodiments of the invention, the term "isolator" can refer to an optical element configured to allow light to travel in only one direction.

[0479] Those skilled in the art will understand that, according to some embodiments of the invention, the term "pump module" can refer to a module in which the diode provides a multimode beam. Those skilled in the art will understand that the term "wide-area laser (BAL) diode" can refer to a diode that provides a multimode beam with an elliptical cross-section. A BAL (also known as a wide-striped or wide-emitter laser diode, a single-emitter laser diode, and a high-brightness diode laser) is an edge-emitting laser diode in which the emission region at the front face has a wide stripe shape.

[0480] Those skilled in the art will understand that, according to some embodiments of the present invention, the term "single-mode" may refer to a beam in which only one transverse mode is excited.

[0481] Those skilled in the art will understand that, according to some embodiments of the present invention, the term "polarizer combiner" can refer to an optical element configured to combine two signals having vertical polarization together.

[0482] Those skilled in the art will understand that, according to some embodiments of the invention, the term "volume Bragg grating (VBG)" can refer to an optical device comprising a grating within a glass block, configured to reflect an incident beam at an angle relative to the wavelength of the incident beam. A typical application of volume Bragg gratings is the wavelength stabilization of lasers (most commonly laser diodes).

[0483] Those skilled in the art will understand that, according to some embodiments of the invention, the term "end cap" can refer to an optical device configured to expand the cross-section of a light beam. An optical fiber end cap is formed by fusion splicing or laser fusing short lengths of material onto the end face of an optical fiber. Optical fiber end caps are necessary in many applications, including the formation of collimators, to allow high-power fiber laser beams to expand to reduce power density at the air / quartz interface and to protect structured optical fibers from environmental damage.

[0484] Those skilled in the art will understand that, according to some embodiments of the invention, the term "one or more phase modulators" can refer to optical modulators that can be used to control the optical phase of a laser beam. Commonly used types of phase modulators include Pockels-based electro-optic modulators, lithium niobate (LiNbO3) electro-optic modulators, and liquid crystal modulators, but it is also possible to utilize, for example, thermally induced refractive index changes or length changes in optical fibers, or length changes induced by stretching. Various phase modulators are used within the area of ​​an integrated optical device, wherein the modulated light propagates in a waveguide.

[0485] Those skilled in the art will understand that, according to some embodiments of the present invention, the term "beam splitter" can refer to an optical device configured to split an incident beam (e.g., a laser beam) into two or more beams, which may or may not have the same optical power. In some embodiments, a beam splitter is used as a beam combiner to combine several beams into a single beam. In some embodiments, interferometers, autocorrelators, cameras, projectors, and laser systems require beam splitters. In some embodiments, a beam splitter may include:

[0486] - A dielectric mirror, which can be any localized reflector used to separate the beam. In laser technology, dielectric mirrors are commonly used for this purpose. The angle of incidence also determines the angular separation of the output beam, such as 45°, which is generally convenient, but it can also have other values ​​and affect the characteristics of the beam splitter. A wide range of power splitting ratios can be achieved through different designs of the dielectric coating.

[0487] - A cube, where beam splitting occurs at the interface within the cube. This cube is typically made of two triangular glass prisms bonded together with some kind of transparent resin or cement. The thickness of this layer can be used to adjust the power distribution ratio for a given wavelength.

[0488] - An optical fiber splitter, which is a type of optical fiber coupler that functions as an optical fiber bundle splitter. Such a device can be manufactured by fusion bonding of fibers and can have two or more output ports. For bulk devices, the split ratio may or may not strongly depend on the input wavelength and polarization.

[0489] A grating is an optical component with a periodic structure that separates and diffracts light into several beams propagating in different directions. The resulting shading is a form of structural shading. The directions of these beams depend on the spacing of the grating and the wavelength of the light, so that the grating acts as a dispersive element. In some embodiments, the grating can also be used as a beam combiner.

[0490] Those skilled in the art will understand that, according to some embodiments of the present invention, the term "fiber optic coupler" or "coupler" can refer to an optical fiber device having one or more input fibers and one or more output fibers. Light from the input fibers may appear at one or more output ends, where the power distribution may depend on wavelength and polarization.

[0491] Those skilled in the art will understand that, according to some embodiments of the invention, the term "tap" or "tap element" can refer to a coupler configured for a coupling output ratio of 50:50, 75:25, 90:10, or 99:1. Fiber optic splicing can utilize network splicing methods that allow signal extraction from the fiber without disconnecting the connection. Fiber optic splicing allows certain signals transmitted in the core of the fiber to be transferred to another fiber or to a detector or monitor.

[0492] Those skilled in the art will understand that, according to some embodiments of the invention, the term "optical amplifier" can refer to a device that receives some input signals and generates an output signal with high optical power. In some embodiments, the input and output are laser beams propagating in free space or in an optical fiber. Amplification occurs in a so-called gain medium, which must be "pumped" (i.e., provided with energy) from an external source. In some embodiments, the optical amplifier is optically, chemically, or electrically pumped.

[0493] Those skilled in the art will understand that, according to some embodiments, the term "dichroic mirror" can refer to a mirror that has significantly different reflection or transmission characteristics at two different wavelengths.

[0494] Those skilled in the art will understand that, according to some embodiments of the invention, the term "seed laser" can refer to a laser whose output is injected into an amplifier or another laser. Typical types of seed lasers are small laser diodes (single-frequency or gain-switched), short-cavity fiber lasers, and miniature solid-state lasers, such as nonplanar ring oscillators (NPROs).

[0495] Now for reference Figure 10A , Figure 10B , Figure 10C and Figure 10DThis schematically illustrates a hybrid pump module configured to be coupled to optical fiber 2240. In some embodiments, the optical fiber can be a doped (active) fiber or a passive fiber (data format transparent). The optical fiber includes a core 2241 and at least one cladding 2242. Figure 10A , Figure 10B , Figure 10C and Figure 10D As shown, the pump module 2200 includes:

[0496] - At least one focusing lens 2230 that is in the free space optical path with the optical fiber 2240;

[0497] - Multiple diode modules 2210, each diode module being configured to output a multimode beam in a free-space optical path via an optical lens and the cladding 2242 of an optical fiber;

[0498] - At least one core-related module 2220, which is located in the free space optical path with the core 2241 of the optical fiber.

[0499] The relevant module of this chip is configured to provide functionality selected from a group including the following:

[0500] a) A single-mode beam is output to the core 2241 of the optical fiber via an optical lens;

[0501] b) Receives the light beam from the core 2241 of the optical fiber via a focusing lens, and couples the received light beam to the output optical fiber 2411. Figure 12 );

[0502] c) Receives a light beam from the core 2241 of the optical fiber via a focusing lens, and reflects the received light beam back to the core 2241 again via the focusing lens; and

[0503] d) The light beam is received from the core 2241 of the optical fiber via a focusing lens, and a portion of the received light beam is reflected back to the core again via the focusing lens, while the other portion of the received light beam is coupled to the output optical fiber 2610. Figure 14 ).

[0504] In some embodiments, the term "single-mode beam" refers to a beam that includes one or more beam modes (ranging from 1 to 10 modes).

[0505] In some embodiments, a plurality of diode modules 2210 are in a free-space optical path with the cladding 2242 of the optical fiber. In some embodiments, the optical path does not include any optical fiber used for the optical path. In some embodiments, some diode modules 2210 are also in a free-space optical path with the core 2241 of the optical fiber.

[0506] In some embodiments, the core-related module 2220 is in a free-space optical path only with the core 2241 of the optical fiber; this means that no optical light is coupled to the cladding 2242 of the optical fiber 2240. In some embodiments, the optical path does not include any optical fiber used for the optical path.

[0507] In some embodiments, the hybrid pump module 2200 further includes a volume Bragg grating (VBG) 2250 configured to narrow and lock the diode beam to a narrow, predetermined wavelength range. In some embodiments, a common VGB is a 976 wavelength-locked module, which is perfectly matched to high-absorption, narrow-linewidth yttrium boride (Yb) ions. In some embodiments, and as... Figure 10D As shown, VGB is located between focusing lens 2230 and optical fiber 2240.

[0508] In some embodiments, a plurality of diode modules 2210 and chip-related modules 2220 are arranged in at least one row 2281 such that their output beams are parallel to each other in each row. Figure 10A , Figure 10B and Figure 10C Isometric views, top views, and front views of a system having multiple diode modules 2210 (eight diode modules in this example) and core-related modules 2220 arranged in a single row are shown. Figure 10D An isometric view of a system having multiple diode modules 2210 (seventeen diode modules in this example) and core-related modules 2220 arranged in two rows 2281 and 2282 is shown.

[0509] In some embodiments, and as Figure 10D As shown, for the case of two or more rows 2181 and 2182, the pump module also includes:

[0510] -At least one polarizer beam combiner 2260 in the optical path of the first beam line 2281;

[0511] - One or more folding mirrors 2282A, each folding mirror for each additional row, wherein...

[0512] Each folding mirror is configured to redirect its corresponding parallel beam line into its respective polarizer combiner.

[0513] In some embodiments, and as Figure 10A and Figure 10B As shown, each diode module 2210 includes:

[0514] - Wide-area laser (BAL) 2211, which is configured to output a multimode beam;

[0515] - A BAL-associated folding mirror 2212 is configured to have an optical path (via a focusing lens 2230) between its associated BAL and the cladding 2242 of the optical fiber; and - optionally, at least one lens 2213, 2214 is arranged between the BAL and its associated folding mirror 2212 and is configured to adjust the shape of the BAL beam.

[0516] Now for reference Figure 11A , Figure 11B and Figure 11C The figure schematically illustrates a hybrid pump module 2300, which includes, as shown in the figure... Figure 10A-10D At least some features and elements of the hybrid pump module 2200 shown. In some embodiments, the core correlation module is a seed correlation module 2301, which is configured to output a single-mode beam to the core of the optical fiber via an optical lens. The seed correlation module 2301 includes:

[0517] - At least one seed input 2311, which is configured to be coupled to a seed laser device 2702 via an optical fiber 2310 (e.g., Figure 15 (as shown);

[0518] - A seed-associated folding mirror 2312, configured via a focusing lens 2230, provides an optical path between the seed input end and the core 2241 of the optical fiber.

[0519] - Optionally, at least one lens 2313 is arranged between the seed input end and its associated folding mirror 2312 and is configured to adjust the shape of the seed beam.

[0520] In some embodiments, the seed-related module 2300 further includes at least one of the following:

[0521] - A beam splitter (not shown) or a partial reflector 2305 and a monitor 2306, such as Figure 11A As shown, located between the seed input terminal 2311 and the optimal lens 2313 or folding mirror 2312, it is configured to sample the seed beam, monitor the seed beam, and issue an alarm for reverse beam transmission (returning to the seed input terminal 2311).

[0522] - Beam amplifier 2315, such as Figure 11B As shown, located between the seed input 2311 and the optimal lens 2313 or folding mirror 2312, it is configured to amplify the seed beam; and

[0523] -Isolator 2316, such as Figure 11C As shown, the lens located between the seed input 2311 and the optimal lens 2313 or folding mirror 2312 is configured to allow light to pass through in only one direction.

[0524] Now for reference Figure 12 The figure schematically illustrates a hybrid pump module 2400, which includes, as shown in the figure... Figure 10A-10D At least some features and elements of the hybrid pump module 2200 shown. In some embodiments, the core-related module is an output module 2401, which is configured to receive a light beam from the core of the optical fiber via a focusing lens and couple the received light beam to an output optical fiber 2411. The output module 2401 includes:

[0525] - Output fiber 2411, optionally including end cap element 2409;

[0526] - A folding mirror 2412 associated with the output fiber 2411 is configured for the optical path between the core 2241 of the fiber and the output fiber 2411.

[0527] Optionally, at least one lens 2413 is disposed between the output optical fiber 2411 and its associated folding mirror 2412, and is configured to adjust the shape of the received core bundle; and

[0528] -Optimally, a pump-dump (not shown).

[0529] In some embodiments, the output module 2400 further includes a beam splitter (not shown) or a local reflector 2405 and a monitor 2406, which are located between the output fiber 2411 and the optimal lens 2413 or the folding mirror 2412, and are configured to sample the seed beam, monitor it, and issue an alarm for reverse beam transmission (back to the folding mirror 2412).

[0530] Now for reference Figure 13 The diagram schematically illustrates a hybrid pump module 2500, which includes, as shown below: Figure 10A-10D At least some features and elements of the hybrid pump module 2200 shown. In some embodiments, the core-related module is a high reflectivity (HR) module 2501, which is configured to receive a light beam from the core 2241 of the optical fiber via a focusing lens and reflect the received light beam back to the core 2241 via the focusing lens. The HR module 2501 includes:

[0531] -HR mirror 2511,

[0532] - A folding mirror 2512 associated with the HR mirror 2511, configured for the optical path between the fiber core 2241 and the HR mirror, and

[0533] - Optionally, at least one lens 2513 is arranged between the HR mirror 2511 and the associated folding mirror 2512, and is configured to adjust the shape of the associated beam.

[0534] In some embodiments, the (HR) module 2501 is configured to reflect the received light beam back and forth in the form of an optical fiber resonator.

[0535] In some embodiments, the HR module 2501 further includes an intracavity modulator 2510 disposed between the HR mirror 2511 and its associated folding mirror 2512, configured to modulate the amplitude, phase, or polarization of the reflected beam, or any combination thereof. In some embodiments, the intracavity modulator includes a non-acousto-optic modulator or an electro-optic modulator. In some embodiments, intracavity modulation allows pulsed laser behavior.

[0536] Now for reference Figure 14 The diagram schematically illustrates a hybrid pump module 2600, which includes, as shown below: Figure 10A-10D At least some features and elements of the hybrid pump module 2200 shown. In some embodiments, the core-related module is a local reflection (PR) module 2601, including:

[0537] - Output fiber 2610, optionally including end cap 2609;

[0538] -PR mirror 2611, which is in the optical path with output fiber 2610;

[0539] - A folding mirror 2612 associated with the PR mirror 2611, which is configured for the optical path between the fiber core 2241 and the PR mirror 2611; and

[0540] - Optionally, at least one lens 2613 is arranged between the PR mirror 2611 and the associated folding mirror 2612, and is configured to adjust the shape of the associated beam.

[0541] In some embodiments, the components of the hybrid pump modules 2200, 2300, 2400, 2500, and 2600 are configured to be photomechanically aligned by measuring the beam path and adjusting the position and / or orientation of the elements as described above. In some embodiments, the adjustment is provided by a jig vacuum catcher. In some embodiments, the adjusted elements are at least one selected from the following: any of the core modules, any of the diode modules, any of the seed devices, any of the BAL, any of the folding mirrors, any of the lenses, any of the beam amplifiers, any of the beam splitters or local mirrors and monitors, any of the isolators, any of the HR mirrors, any of the PR mirrors, any of the seed inputs, one or more focusing lenses, and VGBs.

[0542] In some embodiments, at least some of the lenses 2213, 2214, 2313, 2413, 2513, and 2613 configured to shape the cross-section of the light beam are selected from: fast-entry collimator (FAC) 2213 and slow-entry collimator (SAC) 2214.

[0543] In some embodiments, at least some of the folding mirrors 2212, 2312, 2412, 2512, and 2612 are configured to deflect (pass through) a portion of the reflected light beam for further monitoring purposes (e.g., as...). Figure 11A (As shown in 2399).

[0544] Now for reference Figure 15 This schematically illustrates the fiber optic amplification system 2700. In some embodiments of the invention, the fiber optic amplification system 2700 includes:

[0545] - Active optical fiber 2740, including a core and at least one cladding;

[0546] - Hybrid laser pumping module 2300, which includes a seed-related module 2301 according to the above embodiment, the hybrid laser pumping module being coupled to a first end 2744 of an optical fiber.

[0547] like Figure 15 As shown, the fiber optic amplification system 2700 is configured to receive a seed laser beam from the seed laser device 2702 and amplify it into a high-power single-mode laser beam.

[0548] In some embodiments, the fiber amplification system 2700 further includes a hybrid pump module 2400, which includes an output module 2401 coupled to a second end 2745 of the fiber. Those skilled in the art will understand that the hybrid pump module 2400 can be used as a counter pump module configured to increase beam amplification at the active fiber 2745.

[0549] In some embodiments, the fiber optic amplification system 2700 further includes at least one of the following: a pump dump 2703, an output fiber 2411 having an end cap element 2704 having a second end 2745 coupled to an active fiber 2740.

[0550] Those skilled in the art will understand that the fiber optic amplification system 2700 according to the various embodiments described above significantly reduces the number of required fusion splices while allowing the number of diode modules to be independent. For example, Figure 9 The existing system 2100 includes six diodes and requires at least nine (9) fusion splices. The current system 2700 includes at least eight (and possibly more) diode modules, but requires only two (2) fusion splices.

[0551] Now for reference Figure 16A and Figure 16B This schematically illustrates a fiber laser system 2800 according to some embodiments of the present invention, comprising:

[0552] -Fiber 2840, comprising a core and at least one cladding;

[0553] - Hybrid laser pumping module 2500, the hybrid laser pumping module including HR module 2501 coupled to a first end 2844 of an optical fiber; and

[0554] - Fiber Bragg grating (FBG) 2804 (e.g.) Figure 16B (as shown) or a hybrid laser pumping module 2600 including a PR module 2601 (such as...) Figure 16A As shown, the fiber Bragg grating (FBG) 2804 or hybrid laser pump module 2600 is coupled to the second end 2845 of the optical fiber.

[0555] Those skilled in the art will understand that the hybrid pump module 2600 can be used as a reverse pump module, which is configured to increase beam amplification at the active fiber 2840.

[0556] In some embodiments, the fiber laser system 2800 further includes at least one of the following: a pump dump 2803 and an output fiber including an end cap element 2804.

[0557] Enhanced frequency conversion via weak high-frequency seed beam generated collinearly in the main beam

[0558] Some embodiments of the present invention relate to frequency conversion of high average power laser beams in nonlinear crystals (NLCs). In some embodiments, in the example of frequency doubling of light with a wavelength of 1064 nm, the term "high average power" refers to a power greater than 300 W from a continuous laser, wherein in a low-absorption LBO, "high power green" is greater than 100 W.

[0559] In some embodiments, the present invention provides a device for correcting a harmful mismatch phase (MP) between the fundamental frequency input beam and the frequency-converted output beam that may occur in the first of a single-power frequency multiplier (PFD) or multi-power frequency multiplier (PFD) chain in a nonlinear crystal (NLC).

[0560] In some embodiments of this application, the term "nonlinear crystal" is disclosed, or simply "NLC" or "crystal"; it should be noted that these terms are used interchangeably. In some embodiments of this application, the term "power frequency multiplier" is disclosed, or simply "PFD" or "frequency multiplier"; it should be noted that these terms are used interchangeably. In some embodiments of this application, the term "power frequency multiplier of nonlinear crystal" is disclosed, or simply "PFD NLC," or "frequency multiplier NLC," or "frequency multiplier crystal"; it should be noted that these terms are used interchangeably. In some embodiments of this application, the term "second harmonic" is disclosed, or simply "harmonic"; it should be noted that these terms are used interchangeably.

[0561] In some embodiments, the following two factors are controlled for effective frequency conversion: the temperature in the interaction region of the crystal, and the relative phase between the fundamental beam and one or more NLC output harmonic beams.

[0562] According to existing technology, with respect to a first-harmonic-doubled NLC, near-optimal crystal parameters in the harmonic conversion region are maintained solely by an oven, which does not control the phase mismatch that accumulates as the beam propagates from the entrance of the first-harmonic-doubled NLC (where first harmonic photons are generated) to the first harmonic conversion region of the first-harmonic-doubled NLC. This results in poor high-power frequency conversion. The reason for this is that a uniform temperature oven (UTO) has only one parameter that can be varied (oven temperature), and the maximum power (MP) of the beam near the oven input surface depends on the local temperature at that location. In some embodiments, the present invention provides an apparatus that imposes any desired phase difference between the beams in front of the first-harmonic-doubled NLC so that it is optimal once the beam has propagated to the harmonic conversion region.

[0563] One method reported in the literature is to use two PFD NLCs with intermediate phase mismatch compensators (PMCs). A PMC is an optical element that exhibits dispersion and / or polarization-dependent refractive index. This dispersion can be an intrinsic property of the material or imposed by an external field (an electric field applied to an electro-optic material, such as a Pockels cell).

[0564] The advantage of this inline crystal-PMC-crystal method is that the dispersive element only serves to induce a controllable phase difference between the two co-propagating beams of different wavelengths, and it does not require control over the interference (subwavelength) optical path length of the individually generated beam. This significantly reduces the requirements for sensitivity and stability.

[0565] The key points of existing work on phase mismatch correction are summarized as follows:

[0566] i. Each NLC is configured to achieve maximum frequency conversion, i.e., each NLC is used as a PFD.

[0567] For each crystal used, seek the lowest possible absorption level.

[0568] ii. PMC will only correct the TMP of the first crystal after it has been removed.

[0569] iii. PMC, together with temperature and / or angle tuning, can correct the TMP in the second harmonic crystal.

[0570] iv. To date, there is no way to compensate for the TMP within the first crystal placed in a uniform temperature oven (UTO) except by temperature or angle tuning of the first PFD crystal, or alternatively, to maintain optimal harmonic conversion conditions in the primary conversion region (or the focal region if a focusing lens is used).

[0571] v. More complex gradient temperature ovens (GTOs) can eliminate the possibility of generating MP within a single oven. However, if a linear gradient is required, the GTO needs to control the input and output temperatures of the oven, or if the temperature rise due to light absorption varies along the length of the crystal (like a beam of light focused at the center of the crystal), the GTO needs to control the temperature at multiple points along the oven axis.

[0572] In some embodiments, the present invention relates to an apparatus for overcoming the limitations mentioned in point (iv) for compensating MP in a first PFD NLC in order to improve the frequency doubling efficiency in the first PFD and subsequent PFDs.

[0573] In some embodiments of the present invention, and as such Figure 17AAs shown, improvements are provided by generating a low-power second-harmonic seed beam in a "seeder" NLC 3100 placed in a high-power fundamental frequency beam 3101 prior to the first PFD NLC 3200. The phase difference between the fundamental frequency beam 3101 and one or more harmonic beams 3202 from the seeder NLC is controlled by adding a PMC 3502. In some embodiments and as... Figure 17B As shown, the seeder NLC 3100 is placed in a temperature-controlled oven 3701. In some embodiments, a PMC 3502 placed after the seeder crystal 3100 is provided together with a feedback control system 3602, which is configured to sample the harmonic light 3202 after the first PFD NLC 3200 and control the PMC accordingly to obtain the maximum harmonic light 3202.

[0574] It is important to emphasize that the seeder crystal 3100 only needs to generate a low-power harmonic beam 3102, the phase of which relative to the fundamental frequency beam 3101 can be controlled. Therefore, it may not be necessary to focus the fundamental frequency beam onto a small dot within the seeder crystal 3100, nor is it necessary for the seeder crystal to have approximately the same length (Ls) as that used by the first harmonic NLC 3200.

[0575] High-power light absorption generates and affects the transverse and axial temperature variations of harmonic conversion. Therefore, at all locations along the propagation axis (from the front, through any focal point, to the back), the temperature increases with increasing laser power. This necessitates reducing the oven temperature as the laser power increases.

[0576] In some embodiments, when a uniform temperature oven (UTO) is used in all cases, the temperature along the optical axis varies due to variations in absorptivity (green absorptivity is higher than IR absorptivity), thus increasing the heat towards the rear half of the crystal, and cooling depends on the laser beam radius if a focusing lens is used to increase laser intensity. In the prior art scenario, in the first PFD NLC, there is no independent control over the initial phase matching between the fundamental beam and the harmonic beams. The only observable parameter is the output harmonic power, which is affected by variations occurring along the entire length of the crystal. The prior art solution maximizes the amount of harmonic light generated by varying the oven temperature. For the case of phase matching of the focused beam, the main consideration is maintaining the correct temperature in the focusing region. Changing the temperature to achieve optimal harmonic conversion in the focusing region means that the temperature is not optimal at the beginning of the crystal. The resulting MP reduces harmonic conversion. The present invention provides the following improvement.

[0577] In some embodiments, the oven temperature can be retuned to achieve phase matching at the focal region; however, within the UTO, the MP accumulated from the front of the first PFD NLC to the middle cannot be corrected.

[0578] In some embodiments, adding a weak second harmonic seed beam 3102 to the high-power fundamental frequency beam 3101 before the first PFD NLC 3200 is configured to allow the input phase difference to be adjusted before the first PFD NLC independently of controlling phase matching in the focusing region.

[0579] According to an embodiment of the invention, a “short” nonlinear crystal (seeder crystal) 3100 is provided prior to the first long PFD NLC 3200. The seeder crystal 3100 is configured to generate a weak second harmonic beam that can be in a controllable phase relative to the strong fundamental frequency beam.

[0580] In some embodiments, a PMC 3501 is provided to adjust the IR green MP after the seeder NLC 3100 such that the seeder-NLC MP plus the MP from the first PFD (first PFD NLC) equals zero, i.e.

[0581] ∑MP=MP 播种器 +MP l / 2PFD =0

[0582] It's important to note that the maximum oscillation (MP) accumulated in the first half of a PFD crystal is more significant than that accumulated in the second half. This is because the MP reaching the focal point strongly influences the frequency doubling in the focal region. MP accumulated after the focal region does not significantly reduce the frequency doubling in the crystal because the intensity has already decreased. Furthermore, the next PMC can correct for this latter part of the MP.

[0583] It should be noted that when heat is generated due to NLC absorption, the temperature deviates from the temperature required for phase matching, and particularly for noncritical phase matching (NCPM). The negative consequences are:

[0584] ● Temperature, angle, and spectral bandwidth reduction are most critical in the focal region where most octaves occur.

[0585] • As the beam propagates through the crystal, phase mismatch accumulates, even in regions of weak frequency doubling. This phase mismatch can subsequently reduce frequency doubling efficiency or cause inversion conversion. The accumulation of phase mismatch is most critical between the incident plane and the end of the focusing region.

[0586] In some embodiments, a uniform oven temperature retuning technique is provided to mitigate some of the thermal effects.

[0587] In some embodiments, adjusting the oven temperature can only correct one effect: achieving T=T in the focusing region. 相位匹配Or until the NLC's focal region reaches ∑MP = 0.

[0588] In some embodiments, adding seeders NLC and PMC allows the input phase to be set to the conjugate of the phase mismatch of the crystal, i.e.:

[0589] Δφ 播种器 =(-)MP PFD

[0590] It is independent of the temperature of the focal spot of the PFD NLC.

[0591] In some embodiments, a PMC may not be necessary. The seeder crystal itself generates the phase mismatch required for optimal frequency doubling in a power frequency doubling crystal. The source of this mismatch may be provided by controlling the heating level of the seeder crystal during the passage of the IR beam, or by intentional movement caused by operator-imposed oven temperature variations. However, it should be noted that the response to changing the oven temperature is much slower than rotating the PMC or applying voltage to the electro-optic PMC device.

[0592] In some embodiments, the PMC can generate a desired or predetermined phase difference regardless of the phase difference (between the fundamental beam and the harmonic beam) leaving the seeder crystal. In some embodiments, the PMC can be adjusted faster than the oven temperature. In some embodiments, the PMC allows the power of the seeder crystal to remain constant as the phase difference is adjusted.

[0593] In some embodiments, any phase mismatch caused within the PFD NLC can be mitigated by using a seeder NLC, wherein conjugate mismatch is used to mitigate MP caused by varying laser wavelengths and / or oven temperatures.

[0594] In some embodiments, the above techniques can be applied to any periodically polarized crystal with a constant polarization period.

[0595] Now for reference Figures 17A-17C , Figures 17A-17C This illustration shows several configurations 3100 of an apparatus 3000, according to various embodiments of the invention, for generating a weak second-harmonic seed beam 3102 and for controlling its phase relative to a high-power input beam (fundamental frequency beam) 3101. In some embodiments, after generating the second-harmonic seed beam 3102 and adjusting the phase offset, the beam is propagated into a power frequency doubling (PFD) crystal 3200. In the case depicted here, a long-wavelength beam is frequency-doubled. An achromatic optics device 3402 (achromatic lens or multi-wavelength mirror) can be used to focus the two beams 3102, 3103 onto the same point within the first PFD crystal 3200 to increase intensity and thereby enhance frequency conversion.

[0596] In some embodiments, frequency doubling is effective when phase matching occurs.

[0597] In some embodiments, input waves 3102 and 3103 propagate through the PFD crystal 3200 at exactly the same speed from the first high-frequency photon to the end of the frequency conversion region. In some embodiments, phase matching between two wavelengths can occur in certain crystals by controlling the polarization orientation of the beam relative to the crystal axis. The higher-frequency beam will be automatically polarized along its preferred phase-matching axis.

[0598] In some embodiments, phase matching is a function of the refractive index, which in turn is a function of propagation relative to the crystal axis, polarization, and crystal temperature. In some embodiments, certain crystals held at a specific temperature for a particular input wavelength are particularly insensitive to propagation angle and / or bandwidth. In these cases, the frequency conversion is called noncritical phase matching (NCPM). Thus, for example, if an LBO held at 149.1°C is used to double the frequency of a 1064 nm beam, the beam can be focused into a relatively long crystal. In some embodiments, the focal point and interaction length can then be optimized. However, NCPM is temperature-sensitive, and it is inferred that NCPM is sensitive to light absorption. Green light absorption is approximately four times that of infrared absorption.

[0599] In some embodiments of the present invention, a configuration is provided to double the frequency of light radiation and Figures 17A-17C The new device 3000 is shown in the diagram. Device 3000 includes at least two sequential nonlinear crystals (NLCs) 3100, 3200, and 3300:

[0600] - First NLC 100, which is configured to receive at baseband (F) F The fundamental frequency beam 3101 at the second harmonic frequency (F) is emitted. H The weak second harmonic beam 3102 at the fundamental frequency (F) and the weak second harmonic beam at the fundamental frequency (F) F The power ratio between the strong residual beam 3103 at point 3103 and the weak second harmonic beam 3102 and the fundamental frequency beam 3101 is correspondingly less than 5 × 10⁻⁶. -3 :1; and

[0601] - At least one second NLC 3200 and any optional subsequent NLC 3300, configured to optionally receive the previous NLCs 3100, 3200 at the fundamental frequency (F) after their phase differences have been adjusted for optimal frequency doubling. F The remaining beams 3103 and 3203 at the second harmonic frequency (F) and at the second harmonic frequency (F) H Second harmonic beams 3102 and 3202 at the second harmonic frequency (F) are emitted, and are configured to be emitted at the second harmonic frequency (F). HThe strong frequency-harmonic beams 3202 and 3302 at the location and at the fundamental frequency (F) F The remaining beams 3203 and 3303 at point ) and the power ratio between the strong overtone beams 3202 and 3203 and the fundamental beam 3101 are respectively greater than 0.3:1.

[0602] In some embodiments, the device 3000 further includes at least one phase mismatch compensator (PMC) 3502, 3503, which is configured to operate at the base frequency (F... F The remaining beams 3103 and 3203 at the second harmonic frequency (F) H The second harmonic beams 3102 and 3202 at the location are corrected at the fundamental frequency (F) before being received by the second NLC 3200 and / or any subsequent NLC 3300. F The remaining beams 3103 and 3203 at the second harmonic frequency (F) H The phase relationship between the second harmonic beams 3102 and 3202 at point (). In some embodiments, the PMC includes a dispersive element whose integral value can be controlled by tilting or by an applied voltage.

[0603] Figures 17A-17B This illustrates a device 3000, according to various embodiments of the present invention, having only one frequency multiplier for the NLC 3200, while... Figure 17C This indicates devices with two frequency multipliers: NLC 3200 and 3300 (first frequency multiplier NLC 3200 and second frequency multiplier NLC 3300). Figures 17A-17B This indicates that device 3000 is provided, in which PMC3502 is provided before the first frequency multiplier NLC 3200, while Figure 17C The invention illustrates a device in which two PMCs 3502 and 3503 are provided, with one PMC 3502 preceding a first frequency multiplier NLC 3200 and another PMC 3503 preceding a second frequency multiplier NLC 3300.

[0604] In some embodiments, the device 3000 further includes at least one feedback and control system 3602, 3603 configured to sample the high frequency harmonic beams 3202, 3302 and adjust the PMC 3502, 3503 accordingly to achieve maximum power of the high frequency harmonic beams 3202, 3302 over a wide range of operating conditions.

[0605] Figure 17B This demonstrates a feedback and control system 3602 configured to sample a strongly frequency-doubled beam 3202 emitted by a second NLC 3200 (which is a first frequency-doubled NLC) and accordingly adjust the PMC 3502 provided prior to the first frequency-doubled NLC 3200; while Figure 17C The feedback and control system 3603 is shown, which is configured to sample the strong frequency-doubled beam 3302 emitted by the third NLC 3300 (which is a second frequency-doubled NLC) and adjust the PMC 3503 provided before the second frequency-doubled NLC 3300 accordingly; both 3602 and 3603 can be provided sequentially.

[0606] In some embodiments, the feedback and control systems 3602, 3603 include:

[0607] - At least one measuring element (not shown), such as a photodetector;

[0608] - At least one processing element (not shown) configured to analyze data received from at least one measuring element and accordingly provide control commands for one or more PMC adjustments; and

[0609] - At least one adjusting element (not shown) is configured to adjust PMC 3502, 3503 according to control commands; for example, by means of an electric rotating device and / or by applying voltage to the PMC to tilt the PMC.

[0610] In some embodiments, the device 3000 further includes at least one oven 3701, 3702 (in Figure 17B As indicated in the document, each oven is configured to adjust the temperature of the NLC 3100 and 3200 (seeder NLC 3100 and / or frequency doubling NLC 3200).

[0611] In some embodiments, the length (L) of the first NLC 3100 (seeder NLC) s It is basically smaller than the length (L) of the second NLC3100 (frequency multiplier NLC). D In some embodiments, L s equal to L D 10% or less, L s ≤0.1L D .

[0612] In some embodiments, the second NLC 3200 and any optional subsequent NLC 3300 comprise LBO material (for converting continuous-wave laser), and their length (L...) D (Greater than 40mm)

[0613] In some embodiments, the baseband (F) F This includes the characteristics of infrared (IR) light (λ). F =1064nm), therefore the second harmonic frequency (F H This includes the properties of visible light (λ). H=532nm).

[0614] In some embodiments, each NLC is configured with fundamental beam polarization along its crystal axis (Type 1) or with fundamental beam polarization at 45° relative to its crystal axis (Type 2).

[0615] In some embodiments, each NLC includes at least one material selected from the group consisting of: BBO, KTP, LBO, CLBO, DKDP, ADP, KDP, LiIO3, KNbO3, LiNbO3, AgGaS2, AgGaSe2.

[0616] In some embodiments, the size of the lateral region 3210 of each NLC is larger than the size of the input beam it receives.

[0617] In some embodiments, the device further includes at least one collimating lens 3401 configured to precisely parallel the input light rays. In some embodiments, the device further includes at least one converging element 3402, 3403 configured to focus both the frequency-doubled beam and the residual beam into subsequent elements, such as NLC or PMC, optionally focusing to a center (e.g., Figure 17A (3215 in the middle).

[0618] In some embodiments of the present invention, a novel method for frequency doubling of optical radiation is provided, the method comprising:

[0619] - Provide nonlinear crystals (NLCs) with a frequency at the fundamental frequency (F) F The fundamental frequency beam at ) and at the second harmonic frequency (F H The weak second harmonic beam at () location;

[0620] -thus emitted via NLC at the second harmonic frequency (F H The strong harmonic beam at the frequency of ) and the strong harmonic beam at the fundamental frequency (F) F The remaining beam at ().

[0621] The power ratio between the provided weak second harmonic beam and the fundamental frequency beam is correspondingly less than 5×10. -3 :1.

[0622] The power ratio between the emitted high-frequency harmonic beam and the fundamental frequency beam is greater than 0.3:1.

[0623] In some embodiments, the provided steps further include compensating for phase mismatch between the fundamental frequency beam and the weak second harmonic beam via a phase mismatch compensator (PMC); and wherein the method further includes controlling the PMC to achieve maximum power of the strong harmonic beam.

[0624] Now for reference Figure 18A and Figure 18B . Figure 18A The diagram schematically illustrates the temperature variation along the optical axis in a temperature-tuned single crystal for low power conversion, but it undergoes heating when operating at high power. Figure 18B The cumulative phase up to any position Z in the crystal is shown. Temperatures are given as (T0 = 149.1 °C), where T0(Z) is the on-axis temperature. As shown, the crystal is hottest in the focusing region. This is because the area around the heat-generating zone (beam beam) through which heat must pass is the lowest at the focal point, and because the distance heat must travel before leaving the heat-transferring zone (the unirradiated crystal) is the longest at the focal point. The temperature distribution is asymmetrical relative to the focusing region because more green light is generated as the beam propagates, thus absorbing more light in the latter half of the crystal. In this case, every point in the crystal is too hot, and MP increases monotonically.

[0625] As mentioned above, Figure 18A The diagram schematically illustrates the temperature variation along the optical axis in a single LBO crystal placed in an oven set for low-power frequency doubling of a 1064 nm beam. In some embodiments, optimal frequency doubling occurs at 149.1 °C. Due to heating by the laser beam, the temperature range (TO) is greater than the optimal temperature. The non-uniform temperature distribution is because the beam is focused to the center of the crystal, and the green absorptivity is approximately four times greater than the IR absorptivity. Optimal frequency doubling does not occur due to this heating.

[0626] Figure 18B The diagram schematically illustrates the total phase difference between the fundamental and harmonic beams. It should be noted that the phase mismatch begins on the front side of the crystal and gradually accumulates, even though most harmonics occur in the focusing region. This accumulation of MP (primary frequency) significantly affects frequency conversion in the focusing region.

[0627] Now for reference Figures 19A-19C , Figures 19A-19C This demonstrates the temperature retuning of the PFD crystal, followed by the addition of a conjugate seed phase difference to achieve minimum MP and optimal temperature in the focusing region where most frequency transitions occur. In some embodiments, Figures 18A-18B The conditions described in the text are considered as initial conditions.

[0628] Figure 19A A solution with temperature retuning and phase shift provided by a seeder crystal, which is the basis of the solution, is described according to some embodiments. The first step, as in conventional methods, is to perform temperature tuning on the PFD, such as... Figure 19B As shown, the feedback parameter is the maximum harmonic power after the first PFD. However, in some embodiments, the phase of the second harmonic seed beam generated by the seeder crystal may not be optimal. To achieve the optimal phase difference relative to the seeder crystal, the PMC needs to be changed, such as... Figure 19C As shown. Repeat these two steps until no further improvement is achieved. Simulations show that the optimal value can almost always be reached regardless of the initial phase difference, and this optimal value is very close to the conversion efficiency achieved by a perfect PM.

[0629] In some embodiments, the device 3000 described above can be integrated into various systems; the following are a few non-limiting examples:

[0630] • Industrial applications, such as irradiating workpieces with poor infrared absorption for purposes such as cutting, welding, surface treatment, or additive manufacturing.

[0631] • Scientific application systems, such as pumping Ti:sapphire, for the purpose of generating femtosecond pulses at high repetition rates and high average power, or for generating higher frequencies by further total mixing / additional frequency doubling, or for generating tunable frequencies below the second harmonic by adding optical parametric oscillators.

[0632] • Medical application systems that require rapid execution of invasive surgeries.

[0633] Simulation test

[0634] Now for reference Figure 20A , Figure 20B and Figure 20C This demonstrates the results of a set of simulations performed with a 500W input beam. Using a 50mm thick seeder crystal to generate a second-harmonic seed beam, the phase difference is significantly different from the conjugate phase difference required to correct the MP in the PFD NLC. It should be noted that a thinner crystal could have been used from the perspective of the required seeder beam power.

[0635] Models included in the simulation:

[0636] a. Axial-dependent absorption at each wavelength.

[0637] b. The beam of light is focused onto the center of the crystal.

[0638] c. Calculate the transverse temperature within the beam (heated zone) and the unirradiated zone (heat transfer zone).

[0639] d. Phase calculated based on thermo-optic coefficient and segment propagation length.

[0640] e. Use SNLO to multiply the frequency of each segment.

[0641] f. The crystal is divided into seven (7) segments. The beam diameter of each segment is constant.

[0642] g. Use the output for qualitative analysis.

[0643] Figures 20A-20CThis illustrates three scenarios where the axial temperature deviates from the optimal temperature (blue dashed lines). The input laser power was 500W, and a 50mm seeder crystal was used. The test results are as follows:

[0644] • The black line with a solid circle indicates temperature changes, and the oven does not need to be readjusted from low power.

[0645] • The orange line with squares represents the temperature offset after temperature tuning at maximum harmonic power.

[0646] • The green line with the triangle indicates the retuned PMC and the final (smaller) temperature after retuning.

[0647] At the center of the focused region, the optimization objective was set to T0(Z) = 149.1℃. It was assumed that heat transfer along the input surface was equal to heat transfer within the interior. It was also assumed that heat transfer at the input surface was zero. Other boundary conditions were tested.

[0648] Figure 20B This demonstrates the phase difference between the fundamental frequency beam (input beam) and the harmonic beam when using the provided seeder NLC. The PMC phase was adjusted to achieve optimal harmonics at the center of the PFD NLC. This strategy consistently produces optimal harmonics.

[0649] Figure 20C The green beam power as the beam propagates through the PFD is shown. Note that the poor transition before temperature and PMC retuning is evident. Also note that by adding PMC after temperature retuning, the output increases by a factor of 1.3, reaching the calculated power without phase mismatch.

[0650] Table 1 presents a summary of simulation results for frequency doubling of a 500W input beam with and without a 50mm seeder crystal.

[0651] Table 1. Overview of 500W frequency multipliers used with and without a 50mm seeder.

[0652]

[0653] 1. Select only the 50mm seeder to demonstrate its natural MP effect.

[0654] 2.P 2ω (Seeder) = 2.545W

[0655] 3. Despite intense heating, the frequency doubling reached its maximum theoretical level.

[0656] Table 2 shows a summary of the test results when a 500W input beam is frequency-doubled with and without a 10mm seeder crystal.

[0657] Table 2. Overview of 500W frequency multipliers with and without a 10mm seeder. 1.P 2ω (Seeder) = 0.1018W

[0658] 2. Despite intense heating, the frequency doubling reached its maximum theoretical level.

[0659] The key points to note in the above simulation tests are:

[0660] • Two independent parameters are required to correct for phase mismatch between temperature and PMC. Although we have analyzed phase mismatch caused by temperature, the temperature + PMC correction technique can be applied to MP caused by other factors.

[0661] • With the analysis of the focused geometry and the use of an oven at a uniform temperature, acceptable phase matching can be achieved over a longer portion of the PFD.

[0662] • Correction can significantly improve performance. It can raise the performance level to that of a PFD without MP.

[0663] The use of (seeder crystal + PMC) is fully compatible with multiple PFDs. In this case, each additional PFD has its own PMC. Simulations using a second PFD crystal show that ~350W (70% conversion efficiency) can be achieved.

[0664] The purpose of one experimental test was to demonstrate that, as in some of the embodiments described above, injecting a weak seed beam with a controlled fundamental harmonic phase difference can produce better harmonics from a "power frequency multiplier" than an unseeded configuration. This test has the following characteristics:

[0665] a. The low temperature of the first oven generates a weak seed beam. Figure 21 Seed beam profiles for different non-resonant temperatures are shown. Optimal profiles are obtained when the temperature corresponds to the secondary peak value providing the desired power. In this case, 190mW was selected.

[0666] b. Determine P w ≈220W+P 2w The optimal temperature for the second oven is approximately 30W.

[0667] c. Increase the temperature of the second oven to simulate additional heating. Do this twice: once by keeping the PMC at a constant angle, and then by rotating the PMC to produce the maximum overtone.

[0668] The power of the two seeders was tested to distinguish between input power amplification and phase induction effects.

[0669] Figure 22A and Figure 22B The results show the experimental results and comparisons of using the seeder beam and not using the seeder beam. Figure 22A For a 0.643-watt seeder, and Figure 22B For a 0.188 watt seeder; the orange (top) row is for "using seeder" and the blue (bottom) row is for "not using seeder". Figure 22A and Figure 22B This indicates that:

[0670] 1. At the optimal temperature for a 0.643-watt seeder, there is a difference between the results "with seeder" and "without seeder". This indicates power amplification and phase effects.

[0671] 2. At the optimal temperature for the 0.188 watt seeder, there was no difference between the results "with seeder" and "without seeder". Increased temperature only indicates a phase mismatch effect. (Horizontal and / or vertical) differences show some improvement.

[0672] Figure 23 The additional value of using the seeder beam was calculated using the following formula:

[0673] (P 2W-利用播种器 -P 2W-不利用播种器 ) / P 2W-利用播种器 vs. the second oven temperature.

[0674] It seems moderate, since the maximum occurred on the wings and did not bring us back to the peak by more than double.

[0675] In some embodiments, for commercial products, a beam of constant power is generated with fluctuations on the order of ±1.5% SD. The wider the temperature bandwidth of the frequency multiplier, the easier it is to maintain this stability.

[0676] Table 3 shows the width of the temperature tuning curve at the 98.5% level.

[0677] Table 3

[0678]

[0679] Therefore, the bandwidth for "not using the seeder" is more stringent than that for the oven controller. The bandwidth for "using the seeder" is feasible.

[0680] Figure 24 This demonstrates that the seeder beam provides a phase effect by presenting the relationship between the green output beam and the PMC rotation;

[0681] 1. Only phase control can cause reverse conversion (power reduction).

[0682] 2. A fixed oven temperature is obtained by rotating the PMC, and the power is modified.

[0683] 3. A seeder with only 0.19W resulted in a 7-watt reduction in output. Therefore, phase control was confirmed.

[0684] Therefore, based on the above embodiments, the simulation test of the seeder concluded that, using a seed beam, a green power output of >200 watts can be provided from a single beam.

[0685] The functionality of the harmonic conversion system is enhanced by using an actively controlled phase mismatch compensator between two crystals.

[0686] In some embodiments, the present invention provides additional dynamic control functionality to the PMC via feedback or lookup tables to extend the capabilities of the frequency conversion system. In some embodiments, this can result in at least one of the following: enhanced stability in the presence of temperature variations in the oven housing the crystal, variations in the average power of the laser, and the ability to modulate harmonic beams.

[0687] In some embodiments, the PMC described herein includes a glass window. In some embodiments, the PMC can generally be applied to any optical element exhibiting dispersion, which is a function of certain externally controllable parameters.

[0688] refer to Figure 25A , Figure 25B and Figure 25C , Figure 25A , Figure 25B and Figure 25C This describes a device 4000 configured to multiply the input frequency of optical radiation 4101 and provide an output beam 4400 including a second harmonic frequency 4302. The device includes:

[0689] - At least two sequential nonlinear crystals (NLCs) 4200, 4300; each NLC is configured to receive signals from the previous NLC 4200 at a fundamental frequency (F). F The first beam 4101 or 4203 at the second harmonic frequency (F) and optionally at the second harmonic frequency (F) H The second beam is emitted at the second harmonic frequency (F). H The strong frequency-harmonic beams 4202 and 4302 at the location and at the fundamental frequency (F) F The remaining beams at positions 4203 and 4303;

[0690] - At least one phase mismatch compensator (PMC) 4503 positioned between two NLCs;

[0691] The PMC is configured to operate at the baseband frequency (F). FThe remaining beam 4203 at the second harmonic frequency (F) and the beam at the second harmonic frequency (F) H Before the second harmonic beam 4202 at the fundamental frequency (F) is received by the subsequent NLC, it is corrected at the fundamental frequency (F). F The remaining beam 4203 at the second harmonic frequency (F) and the beam at the second harmonic frequency (F) H The phase relationship between the second harmonic beam 4202 at point ) and; and

[0692] - Each PMC is equipped with an electric rotating device configured to actively rotate the PMC and thus actively adjust the correction of the phase relationship between the residual beam and the second harmonic beam.

[0693] In some embodiments, the device 4000 further includes at least one feedback and control system configured to sample the high frequency harmonic beam in real time and accordingly tilt the PMC in a continuous or stepwise manner via an electric rotating device to continuously achieve the maximum power of the high frequency harmonic beam.

[0694] In some embodiments, the feedback and control system includes: at least one beam splitter 4610, at least one measuring element (e.g., photodiode 4620), at least one processing element 4630, and at least one control element 4640 configured to control an electric rotating device 4650.

[0695] In some embodiments, the PMC includes an optically transparent window exhibiting dispersion, such that the distance a light beam must travel through the window varies with its rotation angle. In some embodiments, the PMC includes a plate exhibiting dispersion, such that the distance a light beam must travel through the window (e.g., a transparent plate polished on both sides) varies with its rotation angle.

[0696] In some embodiments, the motor is configured to rotate the PMC in a stepping and / or continuous motion manner in a continuous real-time manner.

[0697] In some embodiments, the motor is also configured to cause the PMC to rotate in a jittering manner limited to an upper limit and a lower limit.

[0698] In some embodiments, the feedback and control system is configured to use jitter to provide at least one of the following:

[0699] - Minimize the inversion conversion in the subsequent NLC to maximize the power of the output beam;

[0700] - Maximize the inverse conversion in the subsequent NLC to minimize the power of the output beam;

[0701] - Optionally, under static or dynamic operating conditions selected from the following, the power of the output beam can be adjusted to a predetermined value between a maximum and a minimum: changing the input laser power and changing the oven temperature.

[0702] In some embodiments, the motor is configured to rotate the PMC in a switching mode between a maximum harmonic conversion state and a minimum harmonic conversion state, such that the output beam is switched on and off accordingly.

[0703] In some embodiments, the motor is configured to rotate the PMC to provide a flat-top pulse with controlled rise and fall times and a controllable duration.

[0704] In some embodiments, the motor is configured to rotate the PMC according to a lookup table, and thus provide shaped harmonic pulses.

[0705] In some embodiments, the device 4000 further includes at least one dichroic beam splitter 4801, which is configured to separate at least a portion of the remaining beam 4303 from the output beam 4400.

[0706] In some embodiments, the power ratio between the emitted high-frequency harmonic beam and the emitted fundamental frequency beam is correspondingly greater than 0.3:1.

[0707] In some embodiments, the device 4000 further includes at least one oven, each configured to adjust the temperature of the NLC. In some embodiments, the device 4000 further includes at least two ovens, each configured to adjust the temperature of a different NLC.

[0708] In some embodiments, active control of the PMC is configured to minimize power variations caused by temperature changes in the oven housing the NLC.

[0709] In some embodiments, at least one NLC in the NLC includes an LBO, and its length (L D This is sufficient to achieve significant harmonic light. In some embodiments, at least one of the NLCs includes an LBO, and its length (L...) is sufficient to achieve significant harmonic light. D (Greater than 40mm)

[0710] In some embodiments, the baseband (F) F This includes the characteristics of infrared (IR) light (λ). F =1064 nanometers (nm), therefore the second harmonic frequency (F H This includes the properties of visible light (λ). H =532nm).

[0711] In some embodiments, each NLC is configured with a fundamental frequency beam polarization along its crystal axis or with a fundamental frequency beam polarization at 45° relative to its crystal axis.

[0712] In some embodiments, each NLC includes at least one material selected from the group consisting of: BBO, KTP, LBO, CLBO, DKDP, ADP, KDP, LiIO3, KNbO3, LiNbO3, AgGaS2, AgGaSe2.

[0713] In some embodiments, the size of the lateral region of each NLC is larger than the size of the input beam it receives.

[0714] In some embodiments, the device 4000 further includes at least one achromatic converging element 4232 or 4231 and 4232, which is configured to focus the fundamental frequency beam and harmonic beam into the NLC.

[0715] In some embodiments of the invention, device 4000 further includes at least one collimating lens 4406 configured to make the light beam rays passing through it approximately parallel. In some embodiments, device 4000 also includes at least one converging element 4404, 4405, such as an achromatic lens or a mirror, configured to focus both the frequency-doubled beam and the remaining beam onto subsequent elements, such as another NLC.

[0716] In some embodiments, the PMC consists of a fused-silica window with a thin (~1 mm) anti-reflection coated layer. In some embodiments, the intrinsic dispersion of the material is used to add a controllable amount of phase difference between the fundamental beam and the harmonic beam passing through it.

[0717] The following examples illustrate how, according to some embodiments, enhanced capabilities are achieved through active control of the PMC. In some embodiments, the PMC is mounted on an electrically rotating (or tilting) base 4650. In some embodiments, and as... Figure 26A and Figure 26B As shown, the fundamental harmonic phase difference increases with the rotation angle α of the PMC. The increased rotation (or tilt) angle α (from the PMC perpendicular to the beam positioning, α = 0) increases the optical path through the PMC. Figure 26B : P1>P0, where P0 is the path where α=0 and P1 is the path where α>0.

[0718] In some embodiments, the optimal rotation angle for providing the best output beam (e.g., a beam at a user-specified power) 4400 can be selected as the result of rotation to the predetermined position, either based on a lookup table (a predefined table based on an earlier database) or by using the feedback system 4603. Figure 25A and Figure 25B As shown (using a feedback system); Figure 25C This demonstrates devices that do not utilize feedback systems. In some embodiments, and as... Figure 25A and 25B As shown, this can be achieved by using a power measurement detector (e.g., a photodiode). Figure 25B Feedback is achieved by sampling the output beam 4400 (4620 in the model). In some embodiments, in both cases (lookup table and feedback system), a computer (or microprocessor) 4630 is used to send control signals to the motor 4650 via drive electronics 4640.

[0719] In some embodiments, and for example as Figure 27 As shown, the feedback algorithm can be used to continuously adjust the rotation angle of the PMC to find and then maintain the maximum frequency doubling efficiency, and to reduce (e.g., by a factor of two) the green power fluctuations caused by the temperature stability limitations of the oven, and the feedback algorithm is used to maintain a constant crystal temperature. In some embodiments, feedback control can be used to correct the PMC angle to overcome variations in laser input power caused by changes in crystal temperature due to differences in light absorption.

[0720] In some embodiments, the reverse frequency harmonic is an inverse conversion. The harmonic light generated in the first crystal can be inversely converted to the fundamental frequency in the second crystal (if the phase difference is adjusted to produce this effect). The PMC is effective in introducing this inverse conversion phase difference. Therefore, the PMC can be rotated to maximize or minimize the harmonic harmonic. This effect allows harmonic pulses to be generated by switching the PMC angle between a low green (LG) angle, thus “off” the output beam, and a high green (HG) angle, thus “on” the output beam.

[0721] In some embodiments, and as Figure 27 As shown, a method 5000 is provided for activating ("on") and / or deactivating ("off") the frequency-doubled output beam of the aforementioned device 4000. The method includes:

[0722] • Real-time sampling and measurement of the 4710 output beam;

[0723] • Continuously or frequently determine whether the output beam has reached the maximum value required to "turn on" the output 4720 (or the minimum value required to "turn off" the output).

[0724] - If “No” 4730, rotate the PMC and repeat the method from sampling step 4710;

[0725] - If "yes" is 4740, then keep the current angle at α. 最大 (or α) 最小 The method is repeated from sampling step 4710 in any case of dynamic input beam and / or dynamic oven temperature.

[0726] In some embodiments, the "on" / "off" state is long enough to achieve an optimal maximum / minimum value. In some embodiments, for faster "rise" or "fall" times ("on" / "off"), the rotation step includes switching the PMC between two predetermined states, thus rapidly modulating the harmonic output beam.

[0727] Device 4000 and method 5000 were tested, demonstrating that the activation (“on”) of the output beam 4400, with a rise time (30 ms), is limited only by the specific data communication hardware employed. In some embodiments, the rise time should be limited only by the inertia of the rotating system and the accuracy of torque and motor switching between the two positions (“on” / “off”). Thus, in phase-switching mode, a rise time of <1 ms should be produced.

[0728] In some embodiments, Figure 25B The aforementioned device 4000, comprising two nonlinear crystals (NLCs) 4200 and 4300, is schematically illustrated in a configuration used for the following test demonstration. The illustrated harmonic conversion setup utilizes two nonlinear crystals placed in an oven and separated by an actively controlled phase mismatch compensator (PMC) board. The PMC is mounted on a motor, the positioning of which can be computer-controlled using a lookup table or feedback provided by a photodiode sampling the harmonic output beam. In this setup, the beam is focused onto each crystal, thereby maximizing the conversion efficiency of each crystal. In some embodiments, and as used in this test setup, the NLC comprises lithium triborate (LBO) oriented for noncritical phase matching of type 1. As shown, the NLC is housed in a resistance oven, the temperature of which is maintained at approximately 149.1 ± 0.15 °C. The optimal temperature varies with input power due to the absorption of light at the fundamental and harmonic wavelengths. The degree of crystal absorption is an important factor. Typical variations in the optimal temperature occur between 10 W and 250 W of fundamental beam power.

[0729] In some embodiments, sensitivity to temperature scale changes is inversely proportional to crystal length. In the tested apparatus, the length of a single crystal is at least 40 millimeters (mm), and each apparatus has two power frequency doubling crystals. Harmonic power stability of ±1% is typically required. This means that the requirement for oven temperature stability through two crystal passes is approximately ±0.04°C, where in this example, the crystal experiences the same temperature change (through two pass tests on one crystal). Such temperature stability exceeds the capabilities of most ovens and controllers. Whenever the temperature drops below a certain level, the oven controller operates by applying an electrical pulse to the heating resistor. This raises the crystal temperature but always results in overshoot.

[0730] Figure 28A and Figure 28B The illustrations schematically depict the changes in crystal temperature and frequency multiplier power over time attributable to the undershoot / overshoot of the oven controller, according to some embodiments of the invention. Figure 28A This indicates that the oven temperature variation did not cross the optimal temperature for frequency doubling, while Figure 28B This indicates the oven temperature across the optimal frequency doubling temperature. For a typical system, the characteristic heating and cooling time is approximately one minute. As shown in the figure... Figure 28A As shown, if the temperature does not exceed the optimal temperature point, the change in harmonic optical power will mimic the frequency of the oven temperature change. Figure 28B As shown, when the oven temperature does indeed cross the optimal temperature point, the frequency of harmonic power changes increases until the temperature fluctuation frequency doubles (when the temperature change is at T). 最佳 (When symmetrical in the vicinity). This result is a consequence of the fact that each time the temperature crosses T... 最佳 The harmonic power reaches its peak value during both the rising and falling phases, but decreases for both positive and negative ΔT.

[0731] In some embodiments, due to phase mismatch between the fundamental and harmonic light caused by temperature variations, a phase mismatch compensator (PMC) plate can be used to add conjugate phase to invalidate the oven-induced phase mismatch. In some embodiments, the PMC rotation is continuously varied because the oven temperature varies continuously. Therefore, the PMC is placed on an electrically driven rotary table. In some embodiments, the PMC rotation angle is varied via jitter control. In some embodiments, jitter control is an intentionally applied form of noise used to randomize quantization errors, thereby preventing large-scale patterns.

[0732] Figure 29This demonstrates output power stabilization achieved via a jitter-controlled rotating PMC according to some embodiments of the invention, the PMC being configured to overcome oven undershoot / overshoot. As shown, the active PMC response is displayed as a vertical line of time. The rotation direction and speed are evaluated at the end of each response cycle. Errors and power drops can occur due to the time delay between the crystal starting to heat or cool and the PMC reorientation. High-frequency, small-amplitude, rotating jitter control is applied to the PMC, as shown. In some embodiments, the upper limit of the jitter frequency is determined by physical inertia plus the integral of the feedback signal and the system's response time. In some embodiments, the lower limit of the jitter frequency is determined by application requirements or the height / depth of power fluctuations caused by jitter. In some embodiments, the optimal PMC-induced phase is not constant but a sawtooth pattern with a period equal to the period of oven temperature change. In addition to this slower change, there is also a jitter phase variation. When the jitter control correctly tracks oven changes, the harmonic power fluctuates at twice the jitter frequency. If there is an error in the PMC phase (e.g., when the crystal has just started heating after the oven is turned on, and there is a lag in processing feedback signals and sending control signals to the PMC), the power decreases, and the high-frequency fluctuations decrease to the jitter frequency.

[0733] In some embodiments, such as Figure 30 As shown, after the operating conditions change, feedback-based jitter control is used to optimize the PMC angle, and according to some embodiments, the harmonic power is then maintained at its maximum value, while... Figure 31A The figure shows a reduction of approximately ±3.7% in typical jitter under static PMC conditions, and according to some embodiments, when the PMC operates using active feedback control, such as Figure 31B As shown, reducing jitter by approximately ±1.6% of the typical value, in Figure 31B Continuous jitter was used (the upper right shows a zoomed-in view of the time zone from 1440.5 to 1442.7 seconds). For these measurements, a feedback photodiode was monitored. Note: Figure 30 This indicates the green power output, where the feedback-controlled PMC is rotated to bring the output to its maximum level (P). 2ω =80 watts). The sawtooth pattern during power rise is a result of PMC jitter control. Data is acquired using a feedback photodiode. Figure 31A and Figure 31B This demonstrates that PMC is stable without continuous feedback control. Figure 31A ) and under the condition of PMC stability with continuous feedback control ( Figure 31B A comparison of power fluctuations. Figure 31A and Figure 31B This indicates a 10-minute window during a 60-minute run. A feedback photodiode was monitored for these measurements.

[0734] In some embodiments, further insights can be gained by examining power meter data in the frequency domain. This is in Figure 32 The demonstration used Fast Fourier Transform (FFT) to analyze a one-hour run with and without a stabilization algorithm (upper curve). For the run without the stabilization algorithm, the harmonic conversion started with optimal phase matching but drifted over time. Thus, two offset peaks were observed at the oven characteristic temperature response frequency and twice that frequency. It should also be noted that there is an increase in low-frequency power just above the constant power (constant output) peak at 0 Hz. Note that there is a point equal to 1 at 0 Hz. This is the constant power component of the signal. In some embodiments, a fully stabilized beam will contain only this one point. This is another indication of power drift. The results of continuous jitter stabilization are very different. The oven-induced power fluctuations are reduced by about 5 times, and the low-frequency drift is also greatly reduced. Higher frequency components beyond the plotting range are generated due to the jitter stabilization algorithm. These frequencies exceed the frequency response of the Ophir 50 (150) power meter used.

[0735] In some embodiments, the same technique used to maximize harmonic conversion in two NLC devices 4000 can be used to achieve and maintain a high level of inverse conversion. In some embodiments, the only parameter that changes is the infrared (IR)-green phase difference. Figure 33 Simulations demonstrating this effect show the impact of rotating the PMC plate on the harmonic output power using Smith nonlinear optics (SNLO) simulations for different input powers. At high power (LG / HG < 0.10), a typical low-to-high green ratio (greater than tenfold) has been experimentally achieved. In some embodiments, this effect can be used to modulate (“on” / “off”) a high-power continuous wave (CW) green beam. This is important because simply turning the fundamental frequency beam on and off only results in a rise time of several minutes. Note that the reason for this is that the oven temperature decreases to account for IR and green absorptivity in order to achieve high-power frequency doubling. When the laser is first turned on, the frequency doubling efficiency is low due to the low temperature. As infrared light is absorbed, the crystal temperature rises, generating more green. The green absorptivity further increases the crystal temperature, which approaches its optimal high-power value. In some embodiments, full frequency doubling efficiency is not achieved until the fundamental frequency is reached and then the green absorptivity brings the crystal to thermal equilibrium.

[0736] Figure 34A and Figure 34B This indicates that, according to some embodiments, such as Figure 34A The rise time (from minimum power to maximum power) achieved by rapidly "switching on" the input laser beam is shown in the figure, and as shown in the figure... Figure 34BThe comparison shown is between rise times (from minimum power to maximum power) achieved by switching PMC positions; IR input power is 246 watts; maximum green power is 75 watts. A thermopile power meter (τ) is used. 上升 =2 seconds) to execute Figure 34A The measurement is obtained using a feedback photodiode. Figure 34B The trace shown (τ) 上升 =30 milliseconds). In this test setup, the rise time of the PMC activation system is limited by the communication time between the photodiode and the computer, and between the computer and the PMC rotary table. The dashed line shows the rise time of the fiber laser during rapid turn-on. The dotted line shows that the rise of the green output power is much slower. This slow response is due to the time required to reach thermal equilibrium, primarily due to IR absorption, and then due to green absorption, as more green power is generated. The faster response using PMC switching is a result of the fact that the first crystal is in thermal equilibrium, while the second crystal is locally heated due to IR absorption. Sub-millisecond rise times should be achieved by minimizing inertia and through proper selection of the motor and controller.

[0737] It should be noted that more sophisticated pulse shaping is a direct extension of this technique. In some embodiments, any shaped pulse can be generated as long as the associated time-dependent PMC angle can be derived, programmed, and then executed.

[0738] In some embodiments, the device 4000 described above can be integrated into various systems; several non-limiting examples include:

[0739] • Industrial applications, such as irradiating workpieces with poor infrared absorption for purposes such as cutting, welding, surface treatment, or additive manufacturing.

[0740] • Application systems, such as pumping Ti:sapphire, for the purpose of generating femtosecond pulses at high repetition rates and high average power, or for generating higher frequencies through further total mixing / additional frequency doubling, or for generating tunable frequencies below the second harmonic by adding an optical parametric oscillator.

[0741] • Medical application systems that require rapid execution of invasive procedures.

[0742] While certain features of the invention have been described and illustrated herein, many modifications, substitutions, alterations, and equivalents will now occur to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and alterations falling within the true spirit of the invention.

Claims

1. A method for modulating a laser beam provided by a laser system, the laser system comprising at least one seed laser device and a coherent beam combining (CBC) system, the CBC system being configured to receive a seed beam from the seed laser device and to selectively provide an amplified laser beam; The CBC system includes: Multiple phase modulators are configured to be optically connected to: the seed beam, multiple optical amplifiers, at least one beam splitter, and at least one beam combiner; the seed beam, the multiple optical amplifiers, the at least one beam splitter, and the at least one beam combiner are all arranged to enable constructive or destructive beam interference at the CBC point; and At least one control circuit is configured to monitor beam interference at the CBC point and control at least one phase modulator of the phase modulators accordingly. The method includes the following steps: The laser beam is activated by controlling the phase modulator to provide the phase-construction beam interference at the CBC point, thereby providing the laser beam. The laser beam is deactivated by controlling the phase modulator to provide the destructive beam interference at the CBC point, thereby blocking the laser beam; The laser system also includes: A fast optical modulator (FOM) is configured to receive a seed beam from the seed laser device and modulate the bandwidth of the seed beam. The method further includes the following steps: The laser beam is provided by controlling the FOM to provide a seed beam with a first bandwidth Δω1, thereby activating the laser beam, the first bandwidth being configured to enable constructive interference at the CBC point of the CBC system; The laser beam is deactivated by controlling the FOM to provide a seed beam with a second bandwidth Δω2, thereby blocking the laser beam. The second bandwidth is configured to disable constructive interference at the CBC point, where Δω2 > Δω1.

2. The method of claim 1, wherein, The activation step by controlling the phase modulator to provide the constructive beam interference includes tuning the phase modulator to provide the constructive beam interference with maximum intensity.

3. The method of claim 2, wherein, The step of deactivating by controlling the phase modulator to provide the destructive beam interference includes controlling half of the tuned phase modulators to add half a phase (π) to the beam of the half of the tuned phase modulators.

4. The method according to claim 2, wherein, The step of deactivating the phase modulator by controlling it to provide the destructive beam interference includes modifying some of the phase modulators in the tuned phase modulator.

5. The method of claim 4, wherein, Each of the tuned phase modulators is modified differently.

6. The method according to claim 2, further comprising the following step: The laser beam is tuned by modifying some of the phase modulators that are tuned to provide maximum beam intensity, the modification being configured to make the intensity of the laser beam equal to a predetermined percentage of the maximum intensity.

7. The method of claim 1, wherein the step of deactivating by controlling the phase modulator to provide the destructive beam interference comprises tuning the phase modulator to provide beam interference with minimum intensity.

8. A method for modulating a laser beam provided by a laser system, the laser system comprising: At least one seed laser device; A fast optical modulator (FOM) is configured to receive a seed beam from the seed laser device and modulate the bandwidth of the seed beam. A coherent beam combining (CBC) system, the coherent beam combining system being configured to receive a modulated seed beam and accordingly provide an amplified laser beam; The method includes the following steps: The laser beam is provided by controlling the FOM to provide a seed beam with a first bandwidth Δω1, thereby activating the laser beam, the first bandwidth being configured to enable constructive interference at the CBC point of the CBC system; The laser beam is deactivated by controlling the FOM to provide a seed beam with a second bandwidth Δω2, thereby blocking the laser beam. The second bandwidth is configured to disable constructive interference at the CBC point, where Δω2 > Δω1.

9. The method of claim 8, wherein, The CBC system includes: Multiple phase modulators are configured to be optically connected to: a modulated seed beam, multiple optical amplifiers, at least one beam splitter, and at least one beam combiner; the modulated seed beam, the multiple optical amplifiers, the at least one beam splitter, and the at least one beam combiner are all arranged to enable constructive beam interference at the CBC point; and At least one control circuit is configured to monitor beam interference at the CBC point and control at least one phase modulator of the phase modulators accordingly. Furthermore, the activation step also includes controlling the phase modulator to provide the phase-length beam interference.

10. The method according to claim 9, wherein, The step of controlling the phase modulator to provide the constructive beam interference includes tuning the phase modulator to provide constructive beam interference with maximum intensity.

11. A method for modulating a laser beam provided by a laser system, the laser system comprising: A coherent beam combining (CBC) system, the coherent beam combining system being configured to receive a seed laser beam and correspondingly provide an amplified laser beam; A first seed laser device, the first seed laser device being configured to provide a first seed beam having a first wavelength λ1; A second seed laser device is configured to provide a second seed beam having a second wavelength λ2, which is different from the first wavelength. as well as An optical switch configured to link only one of the first seed beam and the second seed beam to the CBC system; The CBC system includes: Multiple phase modulators are configured to be optically linked to: a linked seed laser beam, multiple optical amplifiers, at least one beam splitter, and at least one beam combiner; the linked seed laser beam, the multiple optical amplifiers, the at least one beam splitter, and the at least one beam combiner are all arranged to enable constructive beam interference at the CBC point; and At least one control circuit is configured to monitor beam interference at the CBC point and control at least one phase modulator of the phase modulators accordingly. The method includes the following steps: The laser beam is provided by controlling the optical switch to link the first seed beam to the CBC system and controlling the phase modulator to provide the constructive beam interference. The laser beam is deactivated by controlling the optical switch to link the second seed beam to the CBC system, thereby disabling the constructive beam interference and blocking the laser beam.

12. The method of claim 11, wherein, Controlling the phase modulator to provide the constructive beam interference includes tuning the phase modulator to provide constructive beam interference with maximum intensity.

13. A method for modulating a laser beam provided by a laser system, the laser system comprising: A coherent beam combining (CBC) system, the coherent beam combining system being configured to receive a seed laser beam and correspondingly provide an amplified laser beam; A first seed laser device, the first seed laser device being configured to provide a first seed laser beam having a first bandwidth Δω1; A second seed laser device is configured to provide a second seed laser beam having a second bandwidth Δω2, the second bandwidth being greater than the first bandwidth; as well as An optical switch configured to link only one of the first seed laser beam and the second seed laser beam to the CBC system; Wherein, the first bandwidth Δω1 is configured to enable constructive beam interference at the CBC point of the CBC system, and wherein the second bandwidth Δω2 is configured to disable constructive beam interference at the CBC point; The method includes the following steps: The laser beam is activated by controlling the optical switch to link the first seed laser beam to the CBC system, thereby enabling constructive interference and providing the laser beam. The laser beam is deactivated by controlling the optical switch to link the second seed laser beam to the CBC system, thereby disabling constructive interference and blocking the laser beam.

14. The method of claim 13, wherein, The CBC system includes: Multiple phase modulators are configured to be optically linked to: a linked seed beam, multiple optical amplifiers, at least one beam splitter, and at least one beam combiner; the linked seed beam, the multiple optical amplifiers, the at least one beam splitter, and the at least one beam combiner are all arranged to enable constructive beam interference at the CBC point; and At least one control circuit is configured to monitor beam interference at the CBC point and control at least one phase modulator of the phase modulators accordingly. Furthermore, the activation step also includes controlling the phase modulator to provide the phase-length beam interference.

15. The method of claim 14, wherein, Controlling the phase modulator to provide the constructive beam interference includes tuning the phase modulator to provide constructive beam interference with maximum intensity.

16. A method for modulating a laser beam provided by a laser system, the laser system comprising: At least one seed laser device; An optical polarization beam combiner (OPC) is configured to receive a seed laser beam from the seed laser device and modulate the polarization direction of the seed laser beam; wherein the modulation includes providing at least two polarization components to the seed laser beam, wherein one of the polarization components includes a predetermined polarization direction (P1). A coherent beam combining (CBC) system, the coherent beam combining system being configured to receive a polarization-modulated seed beam and provide an amplified laser beam; and A polarization beam splitter (PBS) is configured to receive the amplified laser beam and transmit only beams having the predetermined polarization direction (P1) to the output of the laser system, while reflecting beams having other polarization directions, thereby selectively providing the laser beam. The method includes the following steps: The laser beam is provided by controlling the OPC to activate the laser beam by providing a beam component having the predetermined polarization direction (P1) and an intensity (I1) greater than 50% of the total intensity of the seed laser beam; The laser beam is deactivated by controlling the OPC to provide a beam component with the predetermined polarization direction (P1) and an intensity (I1) equal to or less than 50% of the total intensity of the seed laser beam, thereby avoiding the laser beam. The CBC system includes: Multiple phase modulators are configured to be optically connected to: a polarization-modulated seed beam, multiple optical amplifiers, at least one beam splitter, and at least one beam combiner; the polarization-modulated seed beam, the multiple optical amplifiers, the at least one beam splitter, and the at least one beam combiner are all arranged to enable constructive beam interference at the CBC point; and At least one control circuit is configured to monitor beam interference at the CBC point and control at least one phase modulator of the phase modulators accordingly. Furthermore, the method further includes controlling the phase modulator at least during the activated step to provide the phase length beam interference at the CBC point.

17. The method of claim 16, further comprising the step of: The laser beam is tuned by controlling the OPC to provide a beam component having the predetermined polarization direction (P1) and an intensity (I1) equal to a predetermined percentage of the total intensity of the seed laser beam.

18. The method of claim 16, wherein, The OPC includes: A beam splitter is configured to receive an input beam having a first polarization direction (P1) and to output a first output beam (B1(I1, P1)) having the first polarization direction (P1) and a first intensity (I1) and a second output beam (B2(I2, P1)) having the first polarization direction (P1) and a second intensity (I2), wherein the sum of the first intensity and the second intensity is equal to the intensity of the input beam. A polarization converter, configured to receive one of the output beams of the beam splitter and convert the polarization of the one of the output beams; and A polarization beam splitter (PBS), configured to receive a first output beam (B1(I1, P1)) and a converted second output beam (B2(I2, P2)), and combine the first output beam and the converted second output beam into a third beam, which is provided as input to the CBC system; or a coupler, configured to receive the first output beam (B1(I1, P1)) and the converted second output beam (B2(I2, P2)), combine the first output beam and the converted second output beam and split them into two output beams, wherein only one of the two output beams is provided as input to the CBC system.

19. The method of claim 18, wherein, The beam splitter assembly includes: A beam splitter, configured to receive an input beam and split the input beam into two beams; A phase modulator configured to modulate the phase of one of the two beams; A coupler configured to receive the two beams and provide interference between the two beams at two locations, thereby providing a first output beam (B1(I1, P1)) and a second output beam (B2(I2, P1)). An electronic controller is configured to monitor one of two interference positions and control the phase modulator to enable constructive or destructive beam interference at the monitored position accordingly, wherein destructive or constructive beam interference is thereby provided to the unmonitored interference position accordingly. Furthermore, the step of controlling the OPC includes controlling the phase modulator.

20. A laser system configured to modulate a laser beam, the laser system comprising: At least one seed laser device; At least one optical polarization combiner (OPC) is configured to receive a seed beam from the seed laser device and modulate the polarization direction of the seed beam; wherein the modulation includes providing at least two polarization components to the seed beam, wherein one of the polarization components includes a predetermined polarization direction (P1). A coherent beam combining (CBC) system, the coherent beam combining system being configured to receive a polarization-modulated seed beam and provide an amplified laser beam; A polarization beam splitter (PBS) is configured to receive the amplified laser beam and transmit only beams having the predetermined polarization direction (P1) to the output of the laser system, while reflecting beams having other polarization directions, thus selectively providing the laser beam; and Electronic controller, the electronic controller being configured to: The laser beam is activated by controlling the OPC to provide a beam component having the predetermined polarization direction (P1) and an intensity (I1) greater than 50% of the total intensity of the beam, thus providing the laser beam; The laser beam is deactivated by controlling the OPC to provide a beam component having the predetermined polarization direction (P1) and an intensity (I1) equal to or less than 50% of the total intensity of the beam, thus avoiding the laser beam. The CBC system includes: Multiple phase modulators are configured to be optically connected to: the polarization-modulated seed beam, multiple optical amplifiers, at least one beam splitter, and at least one beam combiner; the polarization-modulated seed beam, the multiple optical amplifiers, the at least one beam splitter, and the at least one beam combiner are all arranged to enable constructive beam interference at the CBC point; and At least one control circuit is configured to monitor beam interference at the CBC point and accordingly control at least one phase modulator of the phase modulators to provide the constructive beam interference at the CBC point.

21. The system of claim 20, wherein, The OPC includes: A beam splitter is configured to receive an input beam having a first polarization direction (P1) and to output a first output beam (B1(I1, P1)) having the first polarization direction (P1) and a first intensity (I1) and a second output beam (B2(I2, P1)) having the first polarization direction (P1) and a second intensity (I2), wherein the sum of the first intensity and the second intensity is equal to the intensity of the input beam. A polarization converter, configured to receive one of the output beams of the beam splitter assembly and convert the polarization of the one of the output beams; and A polarization beam splitter configured to receive a first output beam (B1(I1, P1)) and a converted second output beam (B2(I2, P2)), and combine the first output beam and the converted second output beam into a third beam, which is provided as input to the CBC system; or a coupler configured to receive the first output beam (B1(I1, P1)) and the converted second output beam (B2(I2, P2)), combine the first output beam and the converted second output beam, and split them into two output beams, wherein only one of the two output beams is provided as input to the CBC system.

22. The system according to claim 21, wherein, The beam splitter assembly includes: A beam splitter, configured to receive an input beam and split the input beam into two beams; A phase modulator configured to modulate the phase of one of the two beams; A coupler configured to receive the two beams and provide interference between the two beams at two locations, thereby providing a first output beam (B1(I1, P1)) and a second output beam (B2(I2, P1)). An electronic controller is configured to monitor one of two interference positions and control the phase modulator to enable constructive or destructive beam interference at the monitored position accordingly, wherein destructive or constructive beam interference is thereby provided to the unmonitored interference position.

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