High-energy laser processing system

Abstract

A high-energy laser processing system (100) comprising: a light source (102) for providing a CW initial laser signal having a spectral linewidth in the range of 15 to 250 GHz; an optical modulator (104) which can be configured in a CW operating mode for transmitting the unmodulated CW initial laser signal and in a pulse operating mode for forming a pulsed initial laser signal by applying amplitude modulation; an optical splitter (106); an optical amplifier (108) for amplifying the seed laser signal to an average optical power in the range of 800 W to 5 kW; a phase actuator (110) which can be configured to adjust the phase of the seed laser signal; an optical beam combiner (112); a phase control device (116, 310) which can be operated to transmit a phase control signal configured to cause the phase actuator to adjust the phase of the seed laser signal and minimize the phase difference between seed laser signals in the combined laser signal output from the beam combiner; and a controller (118) for transmitting one or more control signals configured to cause the optical modulator to switch between the operating modes.

Description

Technical Field

[0001] The present invention relates to a high-energy laser processing system.

Background Art

[0002] Lasers are used in many industries for laser processing of materials, including, for example, welding, cutting, marking, drilling, ablation, surface processing, and additive manufacturing. Both continuous wave (cw) and pulsed lasers are used for laser processing of materials. For example, Patent Document 1 describes a pulsed laser for material processing, and some lasers for material processing can be switched between cw operation and pulsed operation. For example, the TRUMPF (registered trademark) TruPulse nanofiber laser can be switched between nanosecond pulsed operation and cw operation.

[0003] The pulse length used varies depending on the specific laser processing being performed and can range from picoseconds to milliseconds, and hundreds of femtoseconds, picoseconds, and nanosecond pulses are widely used. For both cw operation and pulsed operation, the required average optical power also varies depending on the specific laser processing being performed. Cw lasers for material processing typically generate a cw average optical power of up to 5 kW. Pulsed lasers for laser processing typically operate at an average optical power of several tens to several hundreds of watts, and lasers that can be switched between cw operation and pulsed operation, such as the TRUMPF (registered trademark) TruPulse nano, are limited to a maximum cw output power of several hundred W. A number of physical effects, including but not limited to stimulated Brillouin scattering (SBS), stimulated Raman scattering (SRS), and Kerr self-focusing, make further power scaling difficult.

[0004] To achieve a higher cw laser optical power for material processing, spatial beam combining technology is used to combine a number of laser beams to form a higher-energy cw laser beam. The resulting combined laser beam has an insufficient beam quality factor M 2This has the effect of resulting in a corresponding increase in the minimum focused spot size that can be achieved. However, in many material processing applications, this reduction in optical fluence can be acceptable because the workpiece being laser-processed is typically less than 1.5 m from the laser power. Power scaling of fiber lasers can also be performed using coherent beam coupling or spectral beam coupling. Various methods of beam coupling for fiber lasers are reported in Non-Patent Literature 1. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2007 / 132182 [Non-patent literature]

[0006] [Non-Patent Document 1] Fathi, H., Narhi, M., and Gumenyuk, R., "Towards Ultimate High-Power Scaling: Coherent Beam Combining of Fiber Lasers," Photonics, 2021, Vol. 8, p. 566. [Overview of the project] [Problems that the invention aims to solve]

[0007] The objective is to provide an improved high-energy laser processing system. [Means for solving the problem]

[0008] One embodiment provides a high-energy laser processing system comprising a light source, an optical modulator, an optical splitter, a plurality of optical amplifiers, a plurality of phase actuators, an optical beam combiner, a phase control device, and a controller. The light source is configured to provide a continuous-wave (CW) initial laser signal having a spectral linewidth in the range of 15 to 250 GHz. The optical modulator has a CW operating mode and a pulsed operating mode. In the CW operating mode, the optical modulator is configured to transmit an unmodulated CW initial laser signal, and in the pulsed operating mode, the optical modulator is configured to apply amplitude modulation to form a pulsed initial laser signal consisting of initial laser pulses. The optical splitter is configured to power-split the initial laser signal into a plurality of seed laser signals. The optical amplifiers are configured to amplify the seed laser signals to an average optical power in the range of 800 W to 5 kW. The phase actuators can be configured to adjust the phase of the seed laser signals. The phase actuators are provided between the optical splitter and each optical amplifier. The optical beam combiner is configured to receive seed laser signals from the optical amplifiers. The optical beam combiner is further configured to combine a CW seed laser signal into a CW coupled laser signal and a pulsed seed laser signal into a pulsed coupled laser signal. A phase control device is configured to determine the phase difference between the seed laser signals in the coupled laser signal. The phase control device is operable to transmit a phase control signal to a phase actuator. The phase control signal is configured to cause the phase actuator to adjust the phase of the seed laser signals to minimize the phase difference between the seed laser signals in the coupled laser signal. The controller is operable to transmit one or more control signals to the optical modulator, configured to switch between operation in pulsed mode and operation in CW mode.

[0009] This system enables switching between pulsed and CW operation using coherent beam coupling based on power scaling of both CW and pulsed laser signals. The system advantageously utilizes a good diffraction-limited beam (i.e., beam quality less than 1.2 M) to maximize fluence on the material being processed. 2 While maintaining the same power, it scales the average and peak power available during CW and pulsed operation beyond conventional limits. Pulsed operation acts to increase peak power (unlike amplitude modulation of CW laser signals, which only changes the average power and does not increase peak power), allowing reflective surfaces to be processed. This is advantageous as it allows the system to be used to process reflective materials and materials with reflective coatings on their surfaces, and pulsed operation is used to remove reflective coatings from the surface of the material before switching to CW operation to cut or weld bulk material.

[0010] This system enables increased processing speed and the ability to process a wide range of materials, including those with reflective surfaces and coatings. Because the beam is diffraction-limited, the system can advantageously increase the distance between the laser and the material being processed compared to conventional prior art systems.

[0011] Configuring the light source to provide a seed laser signal with a spectral linewidth in the range of 15–250 GHz favorably mitigates nonlinear effects, including stimulated Brillouin scattering (SBS). The optical amplifier allows for the use of lower-power light sources and optical modulators designated for lower-power optical signals.

[0012] In one embodiment, the CW-coupled laser signal has an average optical power of 10 kW or more, such as up to 100 kW. The system enables power scaling to average optical power that cannot be achieved using a single light source and optical amplifier, while maintaining good beam quality.

[0013] In one embodiment, the optical modulator and optical amplifier are configured to provide a seed laser pulse having peak pulse energies in the range of 0.5 mJ and 10 mJ. In one embodiment, the pulse-coupled laser signal has a peak pulse energy of 20 mJ or more, such as up to 100 mJ. The system enables power scaling to peak pulse energies that cannot be achieved using a single light source and optical amplifier.

[0014] In one embodiment, the light source comprises a single-frequency laser and a phase modulator. The single-frequency laser is configured to generate a single-frequency CW laser signal with a spectral linewidth of up to 20 kHz. The phase modulator is operable to apply phase modulation to the single-frequency CW laser signal to spectrally expand the single-frequency CW laser signal and form a CW initial laser signal with a spectral linewidth of up to 120 GHz. Expanding the linewidth of the single-frequency CW laser signal using a phase modulator is advantageous in that an initial laser signal with a precisely controllable linewidth is provided while maintaining the advantage of the low relative intensity noise (RIN) of the single-frequency laser to mitigate nonlinear effects, including SBS.

[0015] In one embodiment, a phase modulator is operable to apply phase modulation to a single-frequency CW laser signal to spectrally expand the single-frequency CW laser signal and form a CW initial laser signal having a spectral linewidth of up to 120 GHz. An optical modulator is provided to the granules of the phase modulator. The optical modulator is configured to transmit an unmodulated CW initial laser signal in CW operating mode. In pulsed operating mode, the optical modulator is configured to apply amplitude modulation to the CW initial laser signal received from the phase modulator to form a pulsed initial laser signal.

[0016] In one embodiment, a single-frequency laser is provided between a phase modulator and an optical modulator. The optical modulator is configured to transmit an unmodulated single-frequency CW laser signal in CW operating mode. The optical modulator is configured to apply amplitude modulation to the single-frequency CW laser signal to form a single-frequency pulsed laser signal in pulsed operating mode. The phase modulator is operable to apply phase modulation to the single-frequency CW laser signal to spectrally expand the single-frequency CW laser signal and form a CW initial laser signal with a spectral linewidth of up to 120 GHz. The phase modulator is further operable to apply phase modulation to the single-frequency pulsed laser signal to spectrally expand the single-frequency pulsed laser signal and form a pulsed initial laser signal with a spectral linewidth of up to 120 GHz.

[0017] In one embodiment, a single-frequency CW laser signal has a spectral linewidth of up to 10 kHz. In another embodiment, a single-frequency CW laser signal has a spectral linewidth of up to 1 kHz. In yet another embodiment, a single-frequency CW laser signal has a spectral linewidth of up to 500 Hz. Expanding a single-frequency CW laser signal with a very narrow linewidth using a phase modulator is advantageous in that it allows a CW laser signal with a precisely controllable linewidth to mitigate SBS to be provided with minimal impact on laser intensity noise.

[0018] In one embodiment, the light source comprises a grating-based fiber laser oscillator configured to generate a CW seed laser signal having a spectral linewidth of up to 120 GHz. The use of a grating-based fiber laser oscillator allows for the direct generation of a CW laser signal with a desired spectral linewidth for mitigating SBS.

[0019] In one embodiment, the light source comprises a laser diode configured to generate a cw initial laser signal having a spectral linewidth in the range of 15 to 250 GHz. The use of the laser diode enables the direct generation of a cw initial laser signal having a desired spectral linewidth for mitigating SBS.

[0020] In one embodiment, the laser diode is one of a fiber Bragg grating locked laser diode or a Fabry - Perot laser diode. In one embodiment, the initial laser pulse is a nanosecond pulse. This can contribute to maintaining a peak power low enough to mitigate non - linear effects including stimulated Raman scattering (SRS) in one or more optical amplifiers.

[0021] In one embodiment, the initial laser pulse has a pulse duration in the range of 1 ns to 2000 ns. This contributes to maintaining a peak pulse power low enough to mitigate non - linear effects such as stimulated Raman scattering and enables the achievement of mJ pulse energy.

[0022] In one embodiment, the initial laser pulse has a pulse repetition rate in the range of 100 kHz to 10 MHz. This can contribute to maintaining a peak power low enough to mitigate non - linear effects including stimulated Raman scattering (SRS) in one or more optical amplifiers.

[0023] In one embodiment, the optical modulator is a semiconductor optical amplifier. In one embodiment, the semiconductor optical amplifier is further configured to amplify the cw initial laser signal in a cw operation mode. The use of the semiconductor optical amplifier (SOA) enables the optical modulator to both amplitude - modulate the cw initial laser signal to form a pulsed initial laser signal and amplify the cw initial laser signal.

[0024] In one embodiment, the semiconductor optical amplifier is further configured to amplify the CW initial laser signal up to a maximum optical power of 1W in CW operating mode. The use of a semiconductor optical amplifier (SOA) allows the optical modulator to both amplitude modulate the CW initial laser signal to form a pulsed initial laser signal and amplify the CW initial laser signal.

[0025] In one embodiment, the semiconductor optical amplifier is configured to amplify the CW initial laser signal up to a maximum optical power of 500 mW in CW operating mode. In another embodiment, the semiconductor optical amplifier is configured to amplify the CW initial laser signal up to a maximum optical power of 300 mW in CW operating mode. In yet another embodiment, the semiconductor optical amplifier is configured to amplify the CW initial laser signal up to a maximum optical power of 200 mW in CW operating mode. In yet another embodiment, the semiconductor optical amplifier is configured to amplify the CW initial laser signal up to a maximum optical power of 100 mW in CW operating mode.

[0026] In one embodiment, the semiconductor optical amplifier is further configured to amplify the initial laser pulse to an average optical power in the range of 1 mW to 250 mW in pulse operation mode. The use of a semiconductor optical amplifier (SOA) allows the optical modulator to amplitude modulate and amplify the CW laser signal simultaneously to form a pulsed initial laser signal.

[0027] In one embodiment, the optical modulator is one of the following: an acousto-optic modulator (AOM), an electroabsorption modulator (EAM), a booster optical amplifier (BOA), or an optical switch such as a micro-electromechanical switch.

[0028] In one embodiment, the optical splitter is configured to power-split an initial laser signal into n seed laser signals, where 5 ≤ n ≤ 100. In one embodiment, the optical splitter comprises one or more diffraction beam splitters, and / or the optical beam combiner comprises one or more diffraction beam combiners.

[0029] In one embodiment, the optical splitter is a geometric beam splitter. The geometric beam splitter may include two or more beam splitting cubes or partial reflection mirrors. In one embodiment, the optical beam combiner is a geometric beam combiner. The geometric beam combiner may include two or more beam coupling cubes or partial reflection mirrors.

[0030] In one embodiment, the optical splitter comprises a plurality of 1x2 optical splitters arranged in a cascaded configuration to sequentially power-split an initial laser signal into a plurality of seed laser signals, such as 8, 16, 32, or 64 seed laser signals of substantially equal power. The plurality of 1x2 optical splitters may be a planar light wave circuit (PLC) or a fused optical fiber splitter.

[0031] In one embodiment, the optical beam combiner includes a plurality of 2×1 optical combiners arranged in a cascade configuration to sequentially combine a plurality of seed laser signals. The plurality of 2×1 optical combiners may be a planar optical circuit (PLC) or a fused optical fiber combiner.

[0032] In one embodiment, one or more control signals are configured to cause the optical modulator to switch between operation in pulse mode and operation in CW mode according to a preset switching pattern.

[0033] In one embodiment, a pre-set switching pattern comprises the steps of: a. operating in pulse operation mode to generate a single pulse; b. switching to CW operation mode and operating in CW operation mode for a pre-set period; and c. restarting step a. at the end of the pre-set period. Steps a. to c. are repeated over the processing period.

[0034] In one embodiment, the controller comprises an interface circuit, a processor, and a memory, the memory containing instructions executable by the processor, thereby enabling the controller to operate to transmit one or more control signals to an optical modulator.

[0035] In one embodiment, the controller comprises an interface circuit, a processor, and a memory, the memory containing instructions executable by the processor, thereby enabling the controller to operate to transmit one or more control signals to an optical modulator. The one or more control signals are configured to cause the optical modulator to switch between operation in pulse mode and operation in continuous wave (CW) mode according to a preset switching pattern. The preset switching pattern is stored in the memory.

[0036] In one embodiment, the controller is operable to transmit a first control signal and a second control signal. The first control signal causes the optical modulator to be configured in pulse operation mode. The second control signal causes the optical modulator to be configured in continuous wave (CW) operation mode. The controller is operable to switch between transmitting the first control signal and transmitting the second control signal according to a preset switching pattern stored in memory.

[0037] In one embodiment, the controller is further operable to transmit one or more control signals in response to receiving an external trigger signal. In one embodiment, the controller is further operable to transmit one or more modulation timing control signals configured to synchronously apply amplitude modulation to the optical modulator.

[0038] In one embodiment, the phase control device comprises a wavefront sensor and a further controller. The wavefront sensor is configured to detect wavefront deformation of the coupled laser signal caused by a phase difference between seed laser signals in the coupled laser signal. The wavefront sensor is configured to output an error signal indicating the detected wavefront deformation. The further controller is operable to transmit a phase control signal in response to the error signal. The phase control signal is configured to cause a phase actuator to adjust the phase of the seed laser signal to minimize the error signal.

[0039] In one embodiment, the further controller comprises an interface circuit, a processor, and memory. The memory contains instructions executable by the processor, thereby enabling the further controller to receive an error signal and transmit a phase control signal in response to the error signal. [Brief explanation of the drawing]

[0040] [Figure 1] A block diagram showing an embodiment of a high-energy laser processing system. [Figure 2] A block diagram showing an embodiment of a high-energy laser processing system. [Figure 3] A block diagram showing an embodiment of a high-energy laser processing system. [Figure 4] A block diagram showing an embodiment of a high-energy laser processing system. [Figure 5] A block diagram showing an embodiment of a high-energy laser processing system. [Figure 6] A block diagram showing an embodiment of a high-energy laser processing system. [Modes for carrying out the invention]

[0041] Referring to Figure 1, one embodiment provides a high-energy laser processing system 100 comprising a light source 102, an optical modulator 104, an optical splitter 106, a plurality of optical amplifiers 108, a plurality of phase actuators 110, an optical beam combiner 112, a phase control device 116, and a controller 118.

[0042] The light source 102 is configured to provide a continuous wave CW initial laser signal having a spectral linewidth in the range of 15 to 250 GHz. The optical modulator 104 has a CW operating mode and a pulsed operating mode. In CW operating mode, the optical modulator is configured to transmit an unmodulated CW initial laser signal. In pulsed operating mode, the optical modulator is configured to apply amplitude modulation to form a pulsed initial laser signal consisting of initial laser pulses. Amplitude modulation is an on / off modulation configured to gate the CW initial laser signal into pulses having a predetermined pulse duration and a predetermined pulse repetition rate. The optical splitter 106 is configured to power split the initial laser signal into multiple seed laser signals.

[0043] Optical amplifiers 108(1) to 108(n) are configured to receive seed laser signals from an optical splitter. Although a single optical amplifier is shown for receiving and amplifying each seed laser signal, it will be understood by those skilled in the art that a series of optical amplifiers may be used for each seed laser signal instead. Each optical amplifier 108 or the series of optical amplifiers is configured to amplify its respective seed laser signal to an average optical power in the range of 800 W to 5 kW. Each optical amplifier 108 may be, for example, an optical fiber amplifier or a solid-state amplifier.

[0044] Phase actuators 110(1) to 110(n) can be configured to adjust the phase of the seed laser signal. The phase actuators are provided between the optical splitter 106 and the respective optical amplifiers 108(1) to 108(n).

[0045] The optical beam combiner 112 is configured to receive the amplified seed laser signal output from the optical amplifier. The optical beam combiner is configured to couple the CW seed laser signal to a CW coupled laser signal and to couple the pulsed seed laser signal to a pulsed coupled laser signal.

[0046] The optical tap 114 is provided downstream of the optical beam combiner and is configured to extract a portion of the combined laser signal output from the optical combiner to form a monitoring signal. The monitoring signal is led to the phase control device 116. The phase control device 116 is configured to determine the phase difference between the seed laser signals in the combined laser signal output from the optical beam combiner based on the monitoring signal.

[0047] The phase control device is operable to transmit a phase control signal to the phase actuator 110. The phase control signal is configured to cause the phase actuator to adjust the phase of the seed laser signal to minimize the phase difference between the seed laser signals in the combined laser signal output from the optical combiner.

[0048] The phase actuator 110, the optical beam combiner 112, the optical tap 114, and the phase control device 116 form a coherent beam coupling device. Coherent beam coupling is well known to those skilled in the art, as described, for example, in Non-Patent Document 1.

[0049] The controller 118 is operable to transmit one or more control signals configured to switch the optical modulator between pulse operation mode and continuous wave (CW) operation mode.

[0050] In one embodiment, the light source 102 includes a grating-based laser oscillator configured to generate a CW seed laser signal having a spectral linewidth of up to 120 GHz.

[0051] In a further embodiment, the light source 102 includes a laser diode configured to generate a cw seed laser signal having a spectral linewidth in the range of 15 to 250 GHz, corresponding to a full width at half maximum (FWHM) of approximately 50 pm to 1 nm at a seed laser wavelength in the range of 1030 nm to 1090 nm. The laser diode may be a fiber Bragg grating-locked laser diode or a Fabry-Perot laser diode.

[0052] In one embodiment, the seed laser pulse is a nanosecond pulse. In one embodiment, the seed laser pulse has a pulse duration in the range of 1 ns to 2000 ns.

[0053] In one embodiment, the seed laser pulse has a pulse repetition rate in the range of 100 kHz to 10 MHz. In one embodiment, the optical modulator 104 is a semiconductor optical amplifier (SOA). The optical modulator 104 may be replaced by an acousto-optic modulator (AOM), an electroabsorption modulator (EAM), a booster optical amplifier (BOA), or an optical switch such as a micro-electromechanical switch.

[0054] In one embodiment, the CW-coupled laser signal has an average optical power of 10 kW or more, such as a maximum of 100 kW. In one embodiment, the optical modulator 104 and the optical amplifier 108 are configured to provide a seed laser pulse having peak pulse energies in the range of 0.5 mJ and 10 mJ.

[0055] In one embodiment, the pulsed laser signal has a peak pulse energy of 20 mJ or more, such as a maximum of 100 mJ. In one embodiment, the optical modulator 104 is configured to gate a CW initial laser signal into pulses having an overall effective duty cycle (repetition rate × pulse duration) in the range of 1% to 10% and a very high extinction ratio (greater than 35 dB). This duty cycle range allows the peak power to be increased in the optical amplifier 108 up to 100 times compared to the average power. For example, a pulse may have a pulse duration of 25 ns, a repetition rate of 1 MHz, and a duty cycle of 2.5%, and may be amplified to an average power of 800 W and a pulse energy of 0.8 mJ.

[0056] In one embodiment, the controller 118 is operable to transmit one or more control signals to the optical modulator 104 that are configured to switch between operation in pulse mode and operation in CW mode according to a preset switching pattern.

[0057] In one embodiment, the preset switching pattern is: a. A step of operating in pulse operation mode to generate a single pulse, b. A process of switching to CW operating mode and operating in CW mode for a predetermined period of time, c. A step of restarting step a at the end of a predetermined period.

[0058] Steps a through c are repeated throughout the processing period. The combined laser signal may be used for material processing by scanning the combined laser signal across the material being processed during the processing period. Scanning can be performed point by point by directing the combined laser signal towards the surface of the material being processed, performing steps a. to c., then moving the combined laser signal to the next point and restarting step a. at the next point as described above. Thus, each of steps a. to c. may be performed at each point, and the combined laser signal is scanned across the material, processing the material point by point.

[0059] Referring to Figure 2, one embodiment provides a high-energy laser processing system 200 comprising a light source 102, an optical modulator 104, an optical splitter 106, a plurality of optical amplifiers 108, a plurality of phase actuators 110, an optical beam combiner 112, a phase control device 116, and a controller 210.

[0060] The controller 210 comprises an interface circuit 212, a processor 214, and a memory 216. The memory contains instructions 218 that can be executed by the processor, thereby enabling the controller to operate to transmit one or more control signals to the optical modulator 104.

[0061] In one embodiment, the controller 210 is operable to transmit a first control signal and a second control signal. The first control signal causes the optical modulator 104 to be configured in pulse operation mode. The second control signal causes the optical modulator to be configured in CW operation mode. The controller is operable to switch between transmitting the first control signal and transmitting the second control signal according to a preset switching pattern stored in memory.

[0062] In one embodiment, the controller 210 is further operable to transmit a first control signal and / or a second control signal in response to receiving an external trigger signal. Referring to Figure 3, one embodiment provides a high-energy laser processing system 300 comprising a light source 302, an optical modulator 304, an optical splitter 106, a plurality of optical amplifiers 108, a plurality of phase actuators 110, an optical beam combiner 112, a phase control device 310, and a controller 118.

[0063] The light source 302 comprises a single-frequency laser 306 and a phase modulator 308. The single-frequency laser 306 is configured to generate a single-frequency CW laser signal with a spectral linewidth of up to 20 kHz. The phase modulator 308 is operable to apply phase modulation to the single-frequency CW laser signal. Phase modulation spectrally expands the single-frequency CW laser signal to a spectral linewidth of up to 120 GHz. This forms the single-frequency CW laser signal into a CW initial laser signal with a spectral linewidth of up to 120 GHz.

[0064] A light modulator 304 is provided downstream of the phase modulator. The light modulator is configured to transmit an unmodulated CW initial laser signal in CW operating mode. In pulsed operating mode, the light modulator is configured to apply amplitude modulation to the CW initial laser signal received from the phase modulator to form a pulsed initial laser signal consisting of initial laser pulses. Amplitude modulation is an on / off modulation configured to gate the CW initial laser signal into pulses having a predetermined pulse duration and a predetermined pulse repetition rate. The phase control device 310 comprises a wavefront sensor 312 and a further controller 314. A light tap 114 is provided downstream of the light beam combiner and is configured to take a portion of the combined laser signal output from the light combiner and form a monitoring signal. The monitoring signal is led to the wavefront sensor. The wavefront sensor is configured to detect wavefront deformation of the monitoring signal, and therefore wavefront deformation of the combined laser signal, caused by the phase difference between the seed laser signals in the combined laser signal. The wavefront sensor 312 is configured to measure aberrations ("wavefront errors") in the optical wavefront of the monitoring signal. The wavefront sensor is configured to output an error signal indicating the measured aberration, i.e., the detected wavefront deformation.

[0065] The controller 314 is operable to transmit a phase control signal in response to the error signal. The phase control signal is configured to cause the phase actuator to adjust the phase of the seed laser signal to minimize the error signal, i.e., to minimize the wavefront deformation of the monitoring signal caused by the phase difference between the seed laser signals in the combined laser signal, and therefore the wavefront deformation of the combined laser signal.

[0066] The phase actuator 110, the optical beam combiner 112, the optical tap 114, the wavefront sensor 312, and the controller 314 form a coherent beam coupling device. Coherent beam coupling is well known to those skilled in the art, as described, for example, in Non-Patent Document 1.

[0067] For coherent beam coupling, the optical path length from the optical splitter 106 to the optical combiner 112 must be well within the coherence length of the single-frequency laser 306. The optical path length can be matched to within micrometers using a combination of delay lines and piezoelectric translation mirrors within the optical path, for example, between the optical amplifier 108 and the optical combiner 112.

[0068] In one embodiment, the controller 314 is further configured to determine a phase delay applied by a phase actuator in order to produce phase-front matching of each seed laser signal, minimize wavefront errors measured by the wavefront sensor 312, and ensure coherent coupling of each seed laser signal.

[0069] In one embodiment, the controller 314 is configured to determine the phase delay applied by the phase actuator to cause phase-front matching of each seed laser signal in order to minimize wavefront errors by applying a “hill-climbing” algorithm.

[0070] It is understood that the aforementioned controller 210 may be replaced by either or both of the controller 118 and the further controller 314. In one embodiment, a single-frequency CW laser signal has a spectral linewidth of up to 10 kHz.

[0071] For example, the single-frequency laser 306 is a ytterbium-doped fiber laser having an operating range of 1030–1120 nm, a spectral linewidth of up to 10 kHz, and an optical power of 10 mW or more. The ytterbium-doped fiber laser may be, for example, the NKT Photonics® Koheras BASIK Y10 ytterbium fiber laser having a wavelength of 1064 nm, an output power of 10 mW or more, and a spectral linewidth (full width at half maximum, FWHM) of 10 kHz.

[0072] In one embodiment, a single-frequency CW laser signal has a spectral linewidth of up to 1 kHz. In one embodiment, a single-frequency CW laser signal has a spectral linewidth of up to 500 Hz.

[0073] In one embodiment, the single-frequency laser 306 is a fiber laser. For example, the single-frequency laser 306 is an erbium-doped fiber laser having an operating range of 1535–1580 nm, a low spectral linewidth of 200 Hz, and an optical power of 30–40 mW. The erbium-doped fiber laser may be, for example, the NKT Photonics® Koheras BASIK E15 erbium fiber laser having a wavelength of 1550.12 nm, an output power of 40 mW, and a spectral linewidth (full width at half maximum, FWHM) of 200 Hz.

[0074] In one embodiment, the optical modulator 304 is a semiconductor optical amplifier (SOA). In one embodiment, the SOA304 is further configured to amplify the CW initial laser signal in CW operating mode.

[0075] In one embodiment, the SOA304 is configured to amplify the initial CW laser signal to a maximum optical power of 1W. SOA304 may be configured to amplify the CW initial laser signal to a maximum optical power of 500 mW. SOA304 may be configured to amplify the CW initial laser signal to a maximum optical power of 300 mW. SOA304 may be configured to amplify the CW initial laser signal to a maximum optical power of 200 mW. SOA304 may be configured to amplify the CW initial laser signal to a maximum optical power of 100 mW.

[0076] In one embodiment, the SOA304 is further configured to apply amplitude modulation to the CW initial laser signal received from the phase modulator in pulse operation mode to form and amplify a pulsed initial laser signal, thereby amplifying the initial laser pulse.

[0077] In one embodiment, the SOA304 is configured to amplify the CW initial laser signal received from the phase modulator so that, in pulse operation mode, the initial laser pulse is amplified to an average optical power in the range of 1 mW to 250 mW.

[0078] In further embodiments, the optical modulator 304 is an optical switch such as an AOM, EAM, BOA, or microelectromechanical switch. In one embodiment, the initial laser pulse is a nanosecond pulse.

[0079] In one embodiment, the initial laser pulse has a pulse duration in the range of 1 ns to 2000 ns. In one embodiment, the initial laser pulse has a pulse repetition rate in the range of 100 kHz to 10 MHz.

[0080] In one embodiment, the CW-coupled laser signal has an average optical power of 10 kW or more, such as a maximum of 100 kW. To achieve an average optical power of 10 kW, the high-energy laser processing system 300 may consist, for example, a 1:5 optical splitter 106, five phase actuators 110(1) to 110(5), and five optical amplifiers (or a series of optical amplifiers) 108(1) to 108(5). The SOA 304 and optical amplifiers 108 are configured to output a seed laser signal having an average optical power of 2 kW.

[0081] Alternatively, to achieve an average optical power of 10 kW, the high-energy laser processing system 300 may consist of a 1:10 optical splitter 106, 10 phase actuators 110(1) to 110(10), and 10 optical amplifiers (or a series of optical amplifiers) 108(1) to 108(10). The SOA 304 and optical amplifiers 108 are configured to output a seed laser signal with an average optical power of 1 kW. It is understood that other additional combinations of average optical power, optical splitter configuration, and the number of phase actuators and optical amplifiers may be used alternatively to achieve a coupled laser signal with an average optical power of 10 kW.

[0082] In one embodiment, the combined laser signal has an average optical power of up to 100 kW. To achieve an average optical power of 100 kW, the high-energy laser processing system 300 may consist, for example, a 1:20 optical splitter 106, 20 phase actuators 110(1) to 110(20), and 20 optical amplifiers (or a series of optical amplifiers) 108(1) to 108(20). The SOA 304 and optical amplifiers 108 are configured to output a seed laser signal having an average optical power of 5 kW. It is understood that other additional combinations of average optical power, optical splitter configuration, and the number of phase actuators and optical amplifiers may be used alternatively to achieve a combined laser signal having an average optical power of up to 100 kW.

[0083] In one embodiment, the optical beam combiner 112 is a tiled aperture beam combiner, for example, a tiled array of end-capped optical fibers, or a packed aperture beam combiner, for example, a geometric beam combiner such as a diffraction grating.

[0084] In one embodiment, the optical modulator 104 is configured to gate a CW initial laser signal into pulses having an overall effective duty cycle (repetition rate × pulse duration) in the range of 1% to 10% and a very high extinction ratio (greater than 35 dB). This duty cycle range allows the peak power to be increased in the optical amplifier 108 up to 100 times compared to the average power. For example, a pulse may have a pulse duration of 25 ns, a repetition rate of 1 MHz, and a duty cycle of 2.5%, and may be amplified to an average power of 800 W and a pulse energy of 0.8 mJ.

[0085] In one embodiment, the high-energy laser processing system 300 comprises, for example, a 1:20 optical splitter 106, 20 phase actuators 110(1) to 110(20), and 20 optical amplifiers (or a series of optical amplifiers) 108(1) to 108(20). In pulse operation mode, the SOA 304 is configured to gate control a cw initial laser signal into 20 ns pulses at a repetition rate of 500 kHz. The optical amplifiers are configured to amplify the pulses to a pulse energy of 2 mJ and an average optical power of 1 kW. The optical beam combiner 112 combines the 20 seed laser signals to give a combined laser signal having an average optical power of 20 kW and a pulse energy of 40 mJ.

[0086] The ablation threshold varies depending on the specific material. In practice, to exceed the ablation threshold for stainless steel or aluminum, 10 Jcm is required. -2 A minimum fluence of 10 Jcm is required. The coupled laser signal in this embodiment is 10 Jcm for a spot diameter (beam diameter) on the surface being processed, up to 714 μm. -2This provides the fluence described above. Commercial off-the-shelf (COTS) pulsed lasers for material processing require a much smaller spot size to achieve the same fluence. For example, the IPG Photonics YLPN-1000-R can generate pulses with a repetition rate of 500 kHz, a pulse energy of 2 mJ, and an average power of 1 kW, which results in a maximum spot diameter of 160 μm and 10 J cm. -2 This makes it possible to achieve a fluence. The spot size of the high-energy laser processing system 300 in this embodiment is significantly larger for the same fluence, which means that using this system, a surface can be processed point by point at a much faster rate using both pulsed laser signals and CW laser signals.

[0087] In one embodiment, the controller 118 is operable to transmit one or more control signals to the optical modulator 304 that are configured to switch between operation in pulse mode and operation in CW mode according to a preset switching pattern.

[0088] In one embodiment, a preset switching pattern is: a. A step of operating in pulse operation mode to generate a single pulse, b. A process of switching to CW operating mode and operating in CW mode for a predetermined period of time, c. A step of restarting step a at the end of a predetermined period.

[0089] Steps a through c are repeated over the processing time. The combined laser signal may be used for material processing by scanning the combined laser signal across the material being processed during the processing period. Scanning can be performed point by pointing the combined laser signal at the surface of the material being processed, performing steps a. to c., then moving the combined laser signal to the next point and restarting step a. at the next point as described above. Thus, each of steps a. to c. may be performed at each point, and the combined laser signal is scanned across the material, processing the material point by point. As described above, the larger spot size that can be provided by the high-energy laser processing system 300 of this embodiment allows the system to be used to process surfaces point by point at much faster speeds than known systems.

[0090] Referring to Figure 4, one embodiment provides a high-energy laser processing system 400 comprising a light source 402, an optical modulator 304, an optical splitter 106, a plurality of optical amplifiers 108, a plurality of phase actuators 110, an optical beam combiner 112, a phase control device 310, and a controller 118.

[0091] The light source 402 comprises a single-frequency laser 306 and a phase modulator 308. The single-frequency laser 306 is configured to generate a single-frequency CW laser signal with a spectral linewidth of up to 20 kHz. An optical modulator 304 is provided between the single-frequency laser 306 and the phase modulator 308. The optical modulator is configured to transmit an unmodulated single-frequency CW laser signal in CW operating mode. The phase modulator 308 is operable to apply phase modulation to the single-frequency CW laser signal to spectrally expand the single-frequency CW laser signal to a spectral linewidth of up to 120 GHz. This forms the single-frequency CW laser signal into a CW initial laser signal with a spectral linewidth of up to 120 GHz.

[0092] The optical modulator is configured to apply amplitude modulation to a single-frequency CW laser signal in pulse operation mode to form a single-frequency pulsed laser signal. The phase modulator 308 can be further operated to apply phase modulation to the single-frequency pulsed laser signal to spectrally expand the single-frequency pulsed laser signal to a spectral linewidth of up to 120 GHz. This forms the single-frequency pulsed laser signal into a pulsed initial laser signal with a spectral linewidth of up to 120 GHz.

[0093] The remaining details of the high-energy laser processing system 400 are the same as those of system 300 described above, with reference to Figure 3. Referring to Figure 5, one embodiment provides a high-energy laser processing system 500 comprising a light source 102, an optical modulator 104, an optical splitter 106, a plurality of optical amplifiers 108, a plurality of phase actuators 110, an optical beam combiner 112, a wavefront sensor 312, and a controller 510.

[0094] The system 500 of this embodiment is substantially the same as the system 200 described above with reference to Figure 2, but has the following modifications to the phase control device and controller 510. The controller 510 comprises an interface circuit 512, a processor 214, and a memory 216. The memory includes instructions 518 that can be executed by the processor, thereby enabling the controller to operate to transmit one or more control signals to the optical modulator 104, and enabling the controller to operate to transmit a phase control signal to the phase actuator 110.

[0095] The controller 510 is operable to transmit a first control signal to the optical modulator and a second control signal to the optical modulator. The first control signal causes the optical modulator 104 to be configured in pulse operation mode. The second control signal causes the optical modulator to be configured in CW operation mode. The controller is operable to switch between transmitting the first control signal and transmitting the second control signal according to a preset switching pattern stored in memory.

[0096] In this embodiment, the phase control device comprises a wavefront sensor 312 and the functions of a controller 510 associated with the phase actuator 110, as will be described in more detail below. The optical tap 114 is configured to take a portion of the coupled laser signal output from the optical combiner and form a monitoring signal. The monitoring signal is led to the wavefront sensor 312. The wavefront sensor is configured to detect wavefront deformation of the monitoring signal, and therefore wavefront deformation of the coupled laser signal, caused by the phase difference between the seed laser signals in the coupled laser signal. The wavefront sensor 312 is configured to measure aberrations ("wavefront errors") in the optical wavefront of the monitoring signal. The wavefront sensor is configured to output an error signal indicating the measured aberration, i.e., the detected wavefront deformation.

[0097] The controller 510 is operable to transmit a phase control signal in response to an error signal. The phase control signal is configured to cause a phase actuator to adjust the phase of the seed laser signal to minimize the error signal, i.e., to minimize the wavefront deformation of the monitoring signal caused by the phase difference between the seed laser signals in the combined laser signal, and therefore the wavefront deformation of the combined laser signal.

[0098] Referring to Figure 6, one embodiment provides a high-energy laser processing system 600 comprising a light source 302, an optical modulator 304, an optical splitter 106, a plurality of optical amplifiers 108, a plurality of phase actuators 110, an optical beam combiner 112, a wavefront sensor 312, and a controller 510.

[0099] The system 600 of this embodiment is substantially the same as the system 300 described above with reference to Figure 3, but has the following modifications. The controller 510 comprises an interface circuit 512, a processor 214, and a memory 216. The memory contains instructions 518 that can be executed by the processor, thereby enabling the controller to operate to send one or more control signals to the optical modulator 304, and enabling the controller to operate to send a phase control signal to the phase actuator 110. Thus, the controller 510 performs the operations of both the controller 118 and the further controller 314 in Figure 3.

[0100] The controller 510 is operable to transmit a first control signal to the optical modulator 304 and a second control signal to the optical modulator. The first control signal causes the optical modulator 304 to be configured in pulse operation mode. The second control signal causes the optical modulator to be configured in CW operation mode. The controller is operable to switch between transmitting the first control signal and transmitting the second control signal according to a preset switching pattern stored in memory.

[0101] In this embodiment, the phase control device comprises a wavefront sensor 312 and the functions of a controller 510 associated with the phase actuator 110, as will be described in more detail below. The optical tap 114 is configured to take a portion of the coupled laser signal output from the optical combiner and form a monitoring signal. The monitoring signal is led to the wavefront sensor 312. The wavefront sensor is configured to detect wavefront deformation of the monitoring signal, and therefore wavefront deformation of the coupled laser signal, caused by the phase difference between the seed laser signals in the coupled laser signal. The wavefront sensor 312 is configured to measure aberrations ("wavefront errors") in the optical wavefront of the monitoring signal. The wavefront sensor is configured to output an error signal indicating the measured aberration, i.e., the detected wavefront deformation.

[0102] The controller 510 is operable to transmit a phase control signal in response to an error signal. The phase control signal is configured to cause a phase actuator to adjust the phase of the seed laser signal to minimize the error signal, i.e., to minimize the wavefront deformation of the monitoring signal caused by the phase difference between the seed laser signals in the combined laser signal, and therefore the wavefront deformation of the combined laser signal.

[0103] Additional Embodiments 1. High-energy laser processing systems (100, 200, 300), A light source (102,302,402) configured to provide a continuous wave (CW) initial laser signal having a spectral linewidth in the range of 15 to 250 GHz, Optical modulators (104,304) that can be configured to transmit a laser signal without amplitude modulation or to apply amplitude modulation to a laser signal, having a CW operating mode configured to transmit the CW initial laser signal without amplitude modulation, and having a pulse operating mode configured to output a pulsed initial laser signal consisting of an initial laser pulse with amplitude modulation applied, An optical splitter (106) configured to power-divide the initial laser signal into multiple seed laser signals, Multiple optical amplifiers (108) configured to amplify the seed laser signal to an average optical power in the range of 800W to 5kW, A plurality of phase actuators (110) that can be configured to adjust the phase of a seed laser signal, provided between the optical splitter and each optical amplifier, A light beam combiner (112) is configured to receive a seed laser signal from the aforementioned optical amplifier, and to couple a CW seed laser signal to a CW coupled laser signal, and to couple a pulsed seed laser signal to a pulsed coupled laser signal. A phase control device (116, 310) configured to determine the phase difference between seed laser signals in the combined laser signal and operable to transmit a phase control signal to a phase actuator, wherein the phase control signal is configured to cause the phase actuator to adjust the phase of the seed laser signals to minimize the phase difference between seed laser signals in the combined laser signal, A system comprising: controllers (118, 210, 318, 510) operable to transmit one or more control signals to the optical modulator, configured to switch between operation in pulse operation mode and operation in CW operation mode.

[0104] 2. The system according to claim 1, wherein the CW coupled laser signal has an average optical power of 10 kW or more, such as a maximum of 100 kW. 3. The system according to claim 1 or 2, wherein the optical modulator (104, 304) and the optical amplifier (108) are configured to provide a seed laser pulse having peak pulse energies in the range of 0.5 mJ and 10 mJ.

[0105] 4. The system according to claim 3, wherein the pulse-coupled laser signal has a peak pulse energy of 20 mJ or more, such as a maximum of 100 mJ. 5. The system according to any one of claims 1 to 4, wherein the light source comprises a single-frequency laser (306) and a phase modulator (308), the single-frequency laser being configured to generate a single-frequency CW laser signal having a spectral linewidth of up to 20 kHz, and the phase modulator being operable to apply phase modulation to increase the spectral linewidth up to 120 GHz.

[0106] 6. The system according to claim 5, wherein the phase modulator (308) is operable to apply phase modulation to the single-frequency CW laser signal to increase the spectral linewidth up to 120 GHz to form a CW initial laser signal, the optical modulator is provided downstream of the phase modulator, the optical modulator (304) is configured to transmit the CW initial laser signal without amplitude modulation in the CW operating mode, and the optical modulator is configured to apply amplitude modulation to the CW initial laser signal received from the phase modulator in the pulse operating mode to form a pulsed initial laser signal.

[0107] 7. The system according to claim 5, wherein the optical modulator (304) is provided between the single-frequency laser (306) and the phase modulator (308), the optical modulator is configured to transmit the single-frequency CW laser signal without amplitude modulation in the CW operating mode, the optical modulator is configured to apply amplitude modulation to the single-frequency CW laser signal in the pulsed operating mode to form a single-frequency pulsed laser signal, the phase modulator is operable to apply phase modulation to increase the spectral linewidth of the single-frequency CW laser signal up to 120 GHz to form a CW initial laser signal, and the phase modulator is further operable to apply phase modulation to increase the spectral linewidth of the single-frequency pulsed laser signal up to 120 GHz to form a pulsed initial laser signal.

[0108] 8. The system according to any one of claims 5 to 7, wherein the single-frequency CW laser signal has a spectral linewidth of up to 10 kHz, such as up to 1 kHz, up to 500 kHz, or up to 10 kHz.

[0109] 9. The system according to any one of claims 1 to 4, wherein the light source (102) comprises one of a grating-based fiber laser oscillator configured to generate a CW initial laser signal having a spectral linewidth of up to 120 GHz, and a laser diode configured to generate a CW initial laser signal having a spectral linewidth in the range of 15 to 250 GHz.

[0110] 10. The system according to any one of claims 1 to 9, wherein the optical modulator (304) is a semiconductor optical amplifier. 11. The system according to claim 10, wherein the semiconductor optical amplifier is further configured to amplify the CW initial laser signal to a maximum optical power of 1W, such as a maximum of 500mW, a maximum of 300mW, a maximum of 200mW, a maximum of 100mW, etc., in the CW operating mode.

[0111] 12. The system according to claim 10 or 11, wherein the semiconductor optical amplifier is further configured to amplify the initial laser pulse to an average optical power in the range of 1 mW to 250 mW in the pulse operation mode.

[0112] 13. The system according to any one of claims 1 to 9, wherein the optical modulator (104) is one of an acousto-optic modulator (AOM), an electroabsorption modulator (EAM), a booster optical amplifier (BOA), and an optical switch such as a micro-electromechanical switch.

[0113] 14. The system according to any one of claims 1 to 15, wherein the controller (210, 510) comprises interface circuits (212, 512), a processor (214), and a memory (216), the memory comprising instructions (218, 518) executable by the processor, thereby enabling the controller (210, 510) to transmit a first control signal configured to configure the optical modulator to the pulse operation mode, and a second control signal configured to configure the optical modulator to the CW operation mode, and the controller is operable to switch between transmitting the first control signal and transmitting the second control signal according to a preset switching pattern stored in the memory.

[0114] 15. The phase control device (310) is, A wavefront sensor (312) is configured to detect wavefront deformation of the coupled laser signal caused by the phase difference between seed laser signals in the coupled laser signal, and to output an error signal indicating the detected wavefront deformation. A further controller (314) operable to transmit a phase control signal in response to the error signal, wherein the phase control signal is configured to cause a phase actuator to adjust the phase of a seed laser signal to minimize the error signal, according to any one of claims 1 to 16.

Claims

1. High-energy laser processing systems (100, 200, 300), A light source (102, 302, 402) configured to provide a continuous wave (cw) initial laser signal having a spectral linewidth in the range of 15 to 250 GHz, An optical modulator (104, 304) having a CW operating mode configured to transmit the unmodulated CW initial laser signal, and a pulse operating mode configured to apply amplitude modulation to form a pulsed initial laser signal consisting of an initial laser pulse, An optical splitter (106) configured to power-divide the initial laser signal into multiple seed laser signals, Multiple optical amplifiers (108) configured to amplify the seed laser signal to an average optical power in the range of 800W to 5kW, A plurality of phase actuators (110) that can be configured to adjust the phase of a seed laser signal, provided between the optical splitter and each optical amplifier, A light beam combiner (112) is configured to receive a seed laser signal from the optical amplifier, and to couple a CW seed laser signal to a CW coupled laser signal, and to couple a pulsed seed laser signal to a pulsed coupled laser signal. A phase control device (116, 310) configured to determine the phase difference between seed laser signals in the combined laser signal and operable to transmit a phase control signal to a phase actuator, wherein the phase control signal is configured to cause the phase actuator to adjust the phase of the seed laser signals to minimize the phase difference between seed laser signals in the combined laser signal, A system comprising: controllers (118, 210, 318, 510) that are operable to transmit one or more control signals to the optical modulator, configured to switch between operation in the pulse operation mode and operation in the CW operation mode.

2. The system according to claim 1, wherein the CW coupled laser signal has an average optical power of 10 kW or more, such as a maximum of 100 kW.

3. The system according to claim 1 or 2, wherein the optical modulators (104, 304) and the optical amplifier (108) are configured to provide a seed laser pulse having peak pulse energies in the range of 0.5 mJ and 10 mJ.

4. The system according to claim 3, wherein the pulse-coupled laser signal has a peak pulse energy of 20 mJ or more, such as a maximum of 100 mJ.

5. The system according to any one of claims 1 to 4, wherein the light source comprises a single-frequency laser (306) and a phase modulator (308), the single-frequency laser being configured to generate a single-frequency CW laser signal having a spectral linewidth of up to 20 kHz, and the phase modulator being operable to apply phase modulation to the single-frequency CW laser signal to spectrally expand the single-frequency CW laser signal to form a CW initial laser signal having a spectral linewidth of up to 120 GHz.

6. The system according to claim 5, wherein the phase modulator (308) is operable to apply phase modulation to the single-frequency CW laser signal to spectrally expand the single-frequency CW laser signal to form a CW initial laser signal having a spectral linewidth of up to 120 GHz, the optical modulator is provided downstream of the phase modulator, the optical modulator (304) is configured to transmit the unmodulated CW initial laser signal in the CW operating mode, and the optical modulator is configured to apply amplitude modulation to the CW initial laser signal received from the phase modulator in the pulse operating mode to form a pulsed initial laser signal.

7. The system according to claim 5, wherein the optical modulator (304) is provided between the single-frequency laser (306) and the phase modulator (308), the optical modulator is configured to transmit the unmodulated single-frequency CW laser signal in the CW operating mode, the optical modulator is configured to apply amplitude modulation to the single-frequency CW laser signal in the pulse operating mode to form a single-frequency pulsed laser signal, the phase modulator is operable to apply phase modulation to the single-frequency CW laser signal to spectrally expand the single-frequency CW laser signal to form a CW initial laser signal having a spectral linewidth of up to 120 GHz, and the phase modulator is further operable to apply phase modulation to the single-frequency pulsed laser signal to spectrally expand the single-frequency pulsed laser signal to form a pulsed initial laser signal having a spectral linewidth of up to 120 GHz.

8. The system according to any one of claims 5 to 7, wherein the single-frequency CW laser signal has a spectral linewidth of up to 10 kHz, such as up to 1 kHz, up to 500 kHz, or up to 10 kHz.

9. The system according to any one of claims 1 to 4, wherein the light source (102) comprises one of a grating-based fiber laser oscillator configured to generate a cw initial laser signal having a spectral linewidth of up to 120 GHz, and a laser diode configured to generate a cw initial laser signal having a spectral linewidth in the range of 15 to 250 GHz.

10. The system according to any one of claims 1 to 9, wherein the optical modulator (304) is a semiconductor optical amplifier.

11. The system according to claim 10, wherein the semiconductor optical amplifier is further configured to amplify the CW initial laser signal to a maximum optical power of 1W, such as a maximum of 500mW, a maximum of 300mW, a maximum of 200mW, a maximum of 100mW, etc., in the CW operating mode.

12. The system according to claim 10 or 11, wherein the semiconductor optical amplifier is further configured to amplify the initial laser pulse to an average optical power in the range of 1 mW to 250 mW in the pulse operation mode.

13. The system according to any one of claims 1 to 9, wherein the optical modulator (104) is one of an acousto-optic modulator (AOM), an electroabsorption modulator (EAM), a booster optical amplifier (BOA), and an optical switch such as a micro-electromechanical switch.

14. The system according to any one of claims 1 to 13, wherein the one or more control signals are configured to cause the optical modulators (104, 304) to switch between operation in pulse operation mode and operation in CW operation mode according to a preset switching pattern.

15. The aforementioned preset switching pattern is a. A step of operating in the pulse operation mode to generate a single pulse, b. A step of switching to the CW operating mode and operating in the CW operating mode for a predetermined period of time, c. A step of restarting step a. at the end of the predetermined period, The system according to claim 14, wherein steps a. to c. are repeated over the processing period.

16. The system according to any one of claims 1 to 15, wherein the controller (210, 510) comprises interface circuits (212, 512), a processor (214), and a memory (216), the memory comprising instructions (218, 518) executable by the processor, thereby enabling the controller (210, 510) to operate to transmit one or more control signals to the optical modulators (104, 304).

17. The phase control device (310) is A wavefront sensor (312) is configured to detect wavefront deformation of the coupled laser signal caused by the phase difference between seed laser signals in the coupled laser signal, and to output an error signal indicating the detected wavefront deformation. A further controller (314) operable to transmit a phase control signal in response to the error signal, wherein the phase control signal is configured to cause a phase actuator to adjust the phase of a seed laser signal to minimize the error signal, according to any one of claims 1 to 16.

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