Synthetic light field method and apparatus based on coherent array of fiber lasers

Abstract

The application provides a method and device for synthesizing an optical field based on a coherent array of fiber lasers, n sub-beams are combined into one beam in an array form, each unit beam in the array beam corresponds to one pixel in the synthesized optical field, the number of sub-beams participating in the array synthesis is determined according to the structure shape and the number of pixels of the required optical field, the array beam is combined in the required array arrangement form, and the amplitude, phase and polarization direction of each unit beam are adjusted to synthesize beams with different optical field distributions, that is, the digital direct synthesis of an arbitrary structure optical field is realized, and the method has the advantages of flexible and convenient generation of an optical field and high output power.

Description

Technical Field

[0001] This invention belongs to the field of optical field manipulation technology, and in particular to a method and apparatus for synthesizing optical fields based on fiber laser coherent arrays. Background Technology

[0002] With the rapid development of fundamental laser theory and technology, optical field manipulation technology has made significant progress in recent years. Optical field manipulation technology refers to the technique of controlling parameters such as amplitude, phase, and polarization of an optical field in one or more dimensions to achieve more specialized properties. This technology is of great significance for the intelligence, compactness, and functional diversification of optical systems, and has broad application prospects in laser communication, life sciences, industrial processing, and materials science. Current optical field manipulation technologies mostly employ specialized functional devices (such as phase plates and spatial light modulators) to generate specific types of optical fields, resulting in relatively limited functionality and lower output power. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention proposes a method and apparatus for synthesizing optical fields based on fiber laser coherent arrays.

[0004] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: On one hand, the present invention provides a method for synthesizing optical fields based on fiber laser coherent arrays, comprising: n After undergoing processing including phase modulation, polarization control, and power amplification, the individual beams are combined into a single output beam using a preset array arrangement. Each unit beam in the output array beam corresponds to a pixel in the synthesized optical field. n The number of pixels is equal to the preset number of pixels in the composite light field, and the preset array arrangement corresponds to the preset arrangement of pixels in the composite light field. Control the amplitude distribution of the array beam according to the preset amplitude distribution requirements. n The power of the beam is amplified accordingly so that the output array beam meets the preset amplitude distribution requirements; A small portion of the output array beam is collected for phase control of the array beam: based on the preset phase distribution diagram of the array beam, the phase of the array beam is controlled. n The phase of the beam is compensated and controlled so that the output array beam meets the preset phase distribution requirements; A small portion of the output array beam is collected for polarization control: the polarization direction of the array beam is detected, and if the polarization direction deviates from the preset polarization state distribution requirement, then... n The polarization direction of the beam is controlled so that the output array beam meets the preset polarization state distribution requirements.

[0005] Further, a small portion of the output array beam is input to the phase error detection module. The phase error detection module includes a liquid crystal phase modulator array plate, a convex lens, a pinhole camera, and a photodetector. The liquid crystal phase modulator array plate has liquid crystal phase adjustment units arranged in an array, with the arrangement of these units matching the array beam. Each beam in the array beam corresponds to a liquid crystal phase adjustment unit on the liquid crystal phase modulator array plate. The liquid crystal phase modulator array plate is loaded with a preset phase distribution map after a flipping operation. A small portion of the output array beam is then incident on the liquid crystal phase modulator array plate. The liquid crystal phase modulator array plate introduces a set phase difference between each unit beam of the array beam. After passing through the liquid crystal phase modulator array plate, the array beam is received by a photodetector after passing through a convex lens and a pinhole. The photodetector converts the optical signal into an electrical signal and transmits it to the phase noise signal processor. The phase noise signal processor optimizes the phase difference compensation between each unit beam in the array beam after passing through the liquid crystal phase modulator array plate to be 0. It loads a phase control signal that is opposite to the preset phase distribution diagram after the flipping operation on the phase modulator corresponding to each sub-beam, so that the output array beam meets the preset phase distribution requirements.

[0006] Furthermore, a small portion of the output array beam is collected and input into the polarization direction detection module, which includes a quarter-wave plate, a liquid crystal delay array plate, a polarization detection plate, and a photodetector array plate. A small portion of the output array beam is incident from one side of a quarter-wave plate, passes through the quarter-wave plate, a liquid crystal retarder array plate, and a polarization detection plate, and is then received by a photodetector array plate. The liquid crystal retarder array plate contains an array of liquid crystal retarders arranged in the same manner as the array beam. Each unit beam in the array beam corresponds to one liquid crystal retarder on the array plate. The fast and slow axes of all liquid crystal retarders are aligned in the same direction, and the spacing between each liquid crystal retarder is consistent with the spacing between unit beams in the corresponding array beam. Similarly, the photodetector array plate contains an array of photodetectors arranged in the same manner as the array beam. Each unit beam in the array beam corresponds to one photodetector on the photodetector array plate, and the spacing between each photodetector on the photodetector array plate is consistent with the spacing between unit beams in the corresponding array beam.

[0007] Furthermore, the fast and slow axis directions of the liquid crystal retarder array plate are at an angle of 45° to the fast and slow axis directions of the quarter-wave plate, and the polarization direction of the polarization detection plate is consistent with the fast axis direction of the quarter-wave plate.

[0008] Furthermore, a small portion of the output array beam is incident on a quarter-wave plate. Based on the angle between the polarization direction of the incident beam and the fast and slow axes of the quarter-wave plate, each unit beam in the output beam of the quarter-wave plate is elliptically polarized, and the fast and slow axes of the elliptically polarized light are consistent with the fast and slow axes of the quarter-wave plate. According to the preset polarization state distribution requirements of the array beam, the corresponding delay phase difference between the fast and slow axes is set for each liquid crystal delayer on the liquid crystal delayer array plate by voltage control; Polarization control is applied to each sub-beam. When the elliptically polarized light output from the quarter-wave plate passes through the corresponding liquid crystal delay unit, different polarization states will be formed under different phase delay conditions. When the polarization state of the beam input to the liquid crystal delay unit is properly matched with the phase difference of the delay of the liquid crystal delay unit, the liquid crystal delay unit will output a linearly polarized beam with the same polarization direction as the polarization detection plate. At this time, the corresponding photodetector on the photodetector array plate will obtain the maximum optical power, thereby outputting the maximum voltage value. The array beam output at this time meets the preset polarization state distribution requirements.

[0009] On the other hand, the present invention provides a synthesized optical field device based on a fiber laser coherent array, comprising: An array beam generating optical path is used to output the array beam, which is composed of... n After undergoing processing including phase modulation, polarization control, and power amplification, the individual beams are combined into a single output beam using a preset array arrangement. Each unit beam in the array corresponds to a pixel in the synthesized light field. n The number of pixels is equal to the preset number of pixels in the composite light field, and the preset array arrangement corresponds to the preset arrangement of pixels in the composite light field. The amplitude control unit is used to control the amplitude distribution of the array beam according to the preset amplitude distribution requirements. n The power of the beam is amplified accordingly so that the output array beam meets the preset amplitude distribution requirements; A phase control loop is used to acquire a small portion of the output array beam for phase control of the array beam: based on a preset phase distribution diagram of the array beam, the phase of the array beam is controlled. n The phase of the output array beam is compensated and controlled to ensure that the output array beam meets the preset phase distribution requirements. A polarization control loop is used to acquire a small portion of the output array beam for polarization control: the polarization direction of the array beam is detected, and if the polarization direction deviates from the preset polarization state distribution requirement, then... n The polarization direction of the beam is controlled so that the output array beam meets the preset polarization state distribution requirements.

[0010] Furthermore, the array beam generation optical path includes a seed laser, an optical fiber beam splitter, a phase modulator, a polarization controller, an optical fiber amplifier, and an optical fiber collimator array. The laser output from the seed laser is split into beams by the optical fiber beam splitter. n Path beam, n The individual beams are respectively phase-modulated, polarized-controlled, and power-amplified by corresponding phase modulators, polarization controllers, and fiber amplifiers. Then, they are combined by a fiber collimator array and output into space to form an array beam. The fiber collimator array includes... n One fiber collimator n The fiber collimators are arranged in a preset array configuration so that the arrangement of the output array beam corresponds to the arrangement of pixels in the preset composite light field.

[0011] Furthermore, the array beam output after the fiber collimator array is synthesized is split into two parts by the first beam splitter. Most of the beam is reflected by the first beam splitter and output to free space. A small portion of the beam transmitted by the first beam splitter is incident on the second beam splitter. The beam reflected by the second beam splitter is input into the polarization control circuit. The beam transmitted by the second beam splitter is input into the reflector and then input into the phase control circuit by the reflector.

[0012] Furthermore, the phase control loop includes a phase error detection module and a phase noise signal processor.

[0013] Furthermore, the polarization control loop includes a polarization direction detection module and a polarization signal processor.

[0014] This invention provides a direct digital synthesis optical field technology based on fiber laser coherent array, which can realize the direct digital synthesis of optical fields with arbitrary structure, and has the advantages of flexible and convenient optical field generation and high output power. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of a synthesized optical field device based on a fiber laser coherent array, provided in one embodiment. Figure 2 This is a structural diagram of a polarization direction detection module in one embodiment; Figure 3 This is a schematic diagram of the front structure of a liquid crystal delay array panel in one embodiment; Figure 4 This is a schematic diagram of the front structure of a photodetector array plate in one embodiment; Figure 5 This is a schematic diagram of the fast and slow axis directions of each device in the polarization direction detection module in one embodiment; Figure 6 This is a schematic diagram of the phase error detection module structure in one embodiment; Figure 7 This is a schematic diagram of a transmissive liquid crystal phase adjuster array plate in one embodiment; The image is labeled as follows: 1. Seed source laser; 2. Fiber beam splitter; 3. Phase modulator; 4. Polarization controller; 5. Fiber amplifier; 6. Fiber collimator array; 7. First beam splitter; 8. Second beam splitter; 9. Mirror; 10. Phase error detection module; 11. Phase noise signal processor; 12. Polarization direction detection module; 13. Polarization signal processor; 14. Optical field parameter controller; 101. Liquid crystal phase adjuster array plate; 102. Convex lens; 103. Pinhole; 104. Second photodetector; 105. Liquid crystal phase adjustment unit; 121. Quarter-wave plate; 122. Liquid crystal delay array plate; 123. Polarization detection plate; 124. Photodetector array plate; 125. Liquid crystal delay; 126. First photodetector; The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Specific implementation methods To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the spirit of the disclosed content will be clearly explained below with reference to the accompanying drawings and detailed description. Any person skilled in the art, after understanding the embodiments of the present invention, can make changes and modifications based on the techniques taught in the present invention without departing from the spirit and scope of the present invention. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0017] To achieve direct digital synthesis of optical fields with arbitrary structures, this invention proposes a method and apparatus for synthesizing optical fields based on a fiber laser coherent array. n Sub-beams are combined into a single beam in an array. Each unit beam in the array beam is equivalent to a pixel in the synthesized light field. The number of sub-beams participating in the array synthesis is determined by the desired light field structure and the number of pixels. They are then combined into the array beam in the required array arrangement. By adjusting three parameters, namely the amplitude, phase, and polarization direction of each unit beam, beams with different light field distributions are synthesized. This achieves direct digital synthesis of light fields with arbitrary structures, and has advantages such as flexible and convenient light field generation and high output power.

[0018] Specifically, in one embodiment, a method for synthesizing optical fields based on a fiber laser coherent array is proposed, comprising: n After undergoing processing including phase modulation, polarization control, and power amplification, the individual beams are combined into a single output beam using a preset array arrangement. Each unit beam in the output array beam corresponds to a pixel in the synthesized optical field. n The number of pixels is equal to the preset number of pixels in the composite light field, and the preset array arrangement corresponds to the preset arrangement of pixels in the composite light field. Control the amplitude distribution of the array beam according to the preset amplitude distribution requirements. n The power of the beam is amplified accordingly so that the output array beam meets the preset amplitude distribution requirements; A small portion of the output array beam is collected for phase control of the array beam: based on the preset phase distribution diagram of the array beam, the phase of the array beam is controlled. n The phase of the output array beam is compensated and controlled to ensure that the output array beam meets the preset phase distribution requirements. A small portion of the output array beam is collected for polarization control: the polarization direction of the array beam is detected, and if the polarization direction deviates from the preset polarization state distribution requirement, then... n The polarization direction of the beam is controlled so that the output array beam meets the preset polarization state distribution requirements.

[0019] Reference Figure 1 A schematic diagram of a fiber laser coherent array-based synthesized light field device is provided in one embodiment, including: An array beam generating optical path is used to output the array beam, which is composed of... n After undergoing processing including phase modulation, polarization control, and power amplification, the individual beams are combined into a single output beam using a preset array arrangement. Each unit beam in the array corresponds to a pixel in the synthesized light field. n The number of pixels is equal to the preset number of pixels in the composite light field, and the preset array arrangement corresponds to the preset arrangement of pixels in the composite light field. The amplitude control unit is used to control the amplitude distribution of the array beam according to the preset amplitude distribution requirements. n The power of the beam is amplified accordingly so that the output array beam meets the preset amplitude distribution requirements; A phase control loop is used to acquire a small portion of the output array beam for phase control of the array beam: based on a preset phase distribution diagram of the array beam, the phase of the array beam is controlled. n The phase of the output array beam is compensated and controlled to ensure that the output array beam meets the preset phase distribution requirements. A polarization control loop is used to acquire a small portion of the output array beam for polarization control: the polarization direction of the array beam is detected, and if the polarization direction deviates from the preset polarization state distribution requirement, then... n The polarization direction of the beam is controlled so that the output array beam meets the preset polarization state distribution requirements.

[0020] exist Figure 1 In the illustrated embodiment, the optical path for generating the array beam includes a seed laser 1, an optical fiber beam splitter 2, a phase modulator 3, a polarization controller 4, an optical fiber amplifier 5, and an optical fiber collimator array 6. The laser output from the seed laser 1 is split by the optical fiber beam splitter 2. n Path beam, n The individual beams are respectively phase-modulated, polarized-controlled, and power-amplified by corresponding phase modulators 3, polarization controllers 4, and fiber amplifiers 5, and then combined by fiber collimator array 6 and output into space to form an array beam. The fiber collimator array 6 includes... n One fiber collimator n The fiber collimators are arranged in a preset array configuration, such that the arrangement of the output array beam corresponds to the pixel arrangement in the preset composite light field. The array beam output from the fiber collimator array 6 is split into two parts by a first beam splitter 7. Most of the beam is reflected by the first beam splitter 7 and output to free space. A smaller portion of the beam transmitted through the first beam splitter 7 is incident on a second beam splitter 8. The beam reflected by the second beam splitter 8 is input to a polarization control loop, and the beam transmitted through the second beam splitter 8 is input to a reflector 9, which in turn inputs to a phase control loop. The phase control loop includes a phase error detection module 10 and a phase noise signal processor 11. The phase noise signal processor 11 controls the phase modulators corresponding to each sub-beam in real time based on the phase noise information output by the phase error detection module 10, compensating for random phase noise between the array beams and ensuring that the output array beam meets the preset phase distribution requirements. The polarization control loop includes a polarization direction detection module 12 and a polarization signal processor 13. The polarization signal processor 13 adjusts the polarization controllers corresponding to each sub-beam in real time according to the information output by the polarization direction detection module 12, so that the output array beam meets the preset polarization state distribution requirements.

[0021] In one embodiment, reference is made to Figure 2A polarization direction detection module is provided, including a quarter-wave plate 121, a liquid crystal retarder array plate 122, a polarization detection plate 123, and a photodetector array plate 124. Liquid crystal retarders 125 are arranged in an array on the liquid crystal retarder array plate 122. The arrangement of the liquid crystal retarders 125 is the same as that of the array beam. Each unit beam in the array beam corresponds to one liquid crystal retarder 125 on the liquid crystal retarder array plate 122. The fast axis and slow axis directions of all liquid crystal retarders 125 are kept the same, and the spacing between each liquid crystal retarder 125 is consistent with the spacing between each unit beam in the corresponding array beam. The photodetector array plate 124 has a first photodetector 126 arranged in an array. The arrangement of the first photodetectors 126 is the same as that of the array beam. Each unit beam in the array beam corresponds to a first photodetector 126 on the photodetector array plate 122. The spacing between each first photodetector 126 on the photodetector array plate 122 is consistent with the spacing between each unit beam in the corresponding array beam. The fast axis and slow axis directions of the liquid crystal delay array plate 122 are at an angle of 45° with the fast axis and slow axis directions of the quarter wave plate 121. The polarization direction of the polarization detection plate 123 is consistent with the fast axis direction of the quarter wave plate 121. A small portion of the output array beam is incident from one side of the quarter-wave plate 121. Based on the angle between the polarization direction of the incident beam and the fast and slow axes of the quarter-wave plate, each unit beam in the output beam of the quarter-wave plate is elliptically polarized, and the fast and slow axes of the elliptically polarized light are aligned with the fast and slow axes of the quarter-wave plate. Linearly polarized light and circularly polarized light are also elliptically polarized light, representing two special cases of elliptically polarized light.

[0022] Each liquid crystal delay unit 125 on the liquid crystal delay unit array 122 is provided with a corresponding delay phase difference between the fast and slow axes. The delay phase difference between the slow axis and the fast and slow axis of each liquid crystal delay unit 125 on the liquid crystal delay unit array 122 is set according to the preset polarization state distribution requirements of the array beam.

[0023] The polarization signal processor 13 controls the polarization of each sub-beam through the polarization controller 4 corresponding to each sub-beam. When the elliptically polarized light output from the quarter-wave plate 121 passes through the corresponding liquid crystal delay unit 125, it will form different polarization states under different phase delay conditions. When the polarization state of the beam input to the liquid crystal delay unit 125 and the delay phase difference of the liquid crystal delay unit 125 are properly matched, the liquid crystal delay unit 125 will output a linearly polarized beam with the same polarization direction as the polarization detection plate 123. At this time, the corresponding first photodetector 126 on the photodetector array plate 124 will obtain the maximum optical power, thereby outputting the maximum voltage value. At this time, the output array beam meets the preset polarization state distribution requirements.

[0024] The quarter-wave plate 121 can be a commercially available quarter-wave plate, and its operating wavelength is consistent with that of the seed source laser 1. The liquid crystal retarder array plate 122 can be realized by fabricating a nematic liquid crystal cell array on a glass substrate. Each nematic liquid crystal cell is a liquid crystal retarder, corresponding to one unit beam in the array beam. The arrangement of the nematic liquid crystal cells is not limited and can be designed according to requirements.

[0025] Reference Figure 3 A schematic diagram of the front structure of a liquid crystal retarder array plate provided in one embodiment is shown in the figure in the form of a square array. Each nematic liquid crystal cell is a liquid crystal retarder, corresponding to an independent unit beam in the array beam. The fast axis and slow axis directions of all liquid crystal retarders are kept the same, and the spacing between each liquid crystal retarder 125 is consistent with the spacing between each unit beam in the corresponding array beam.

[0026] The polarization detection plate 123 can be implemented using a commercial linear polarizer.

[0027] Reference Figure 4 A schematic diagram of the front structure of a photodetector array plate provided in one embodiment shows that it consists of a photodetector array and a substrate. First photodetectors 126 are arranged in an array on the substrate, with the arrangement of the first photodetectors 126 being the same as that of the array beam. Each unit beam in the array beam corresponds to one first photodetector 126 on the photodetector array plate 122. The spacing between each first photodetector 126 on the photodetector array plate 122 is consistent with the spacing between each unit beam in the corresponding array beam. The photodetectors can be commercially available photodetectors, requiring their response wavelength range to cover the output wavelength of the seed source laser, and the photosensitive surface size to be larger than the output beam size of the liquid crystal delay unit. The substrate can be made of epoxy resin circuit board or other materials.

[0028] In one embodiment, the fast axis and slow axis directions of the quarter-wave plate 121 and the liquid crystal delay array plate 122, and the polarization direction of the polarization detection plate are required as follows: Figure 5 The fast and slow axis directions of the liquid crystal delay array plate 122 are at an angle of 45° to the fast and slow axis directions of the quarter wave plate 121, and the polarization direction of the polarization detection plate 123 is consistent with the fast axis direction of the quarter wave plate 121.

[0029] The working principle of the polarization direction detection module is as follows. nAll beams in the output array are linearly polarized, and similarly, each unit beam in the output array is also linearly polarized. When a linearly polarized beam is incident on a quarter-wave plate, depending on the angle between the incident beam's polarization direction and the plate's fast and slow axes, the output beam may be linearly polarized, circularly polarized, or elliptically polarized. Linearly polarized and circularly polarized are two special cases of elliptically polarized light, where the fast and slow axes of the elliptically polarized light are aligned with those of the quarter-wave plate. Since the liquid crystal retarder can control the phase difference between its fast and slow axes via voltage, when the elliptically polarized light output from the quarter-wave plate passes through the liquid crystal retarder, it will form different polarization states under different phase delay conditions. When the polarization state of the elliptically polarized linearly polarized beam input to the liquid crystal retarder matches the phase difference of the retarder appropriately, a linearly polarized beam with the same polarization direction as the polarization detection plate will be output. At this time, the corresponding first photodetector on the photodetector array will obtain the maximum optical power, thus outputting the maximum voltage value. Based on this working principle, the polarization control of the array beam can be achieved in the following steps: First, set the corresponding fast and slow axis phase difference of the liquid crystal delay array according to the preset required polarization distribution. At this time, only array beams with specific polarization directions can make the output voltage of the photodetector array reach the maximum value. Second, use an optimization algorithm to control the polarization controller of each beam so that the corresponding first photodetector outputs the maximum value, thereby obtaining the required polarization distribution.

[0030] The polarization signal processor consists of a controller (which can be a computer, microcontroller, etc.) and digital-to-analog and analog-to-digital conversion circuits. Its main function is to acquire the voltage signals of each photodetector output from the polarization direction detection module, and based on this, run an optimization algorithm (such as the SPGD algorithm) to control the polarization controller and adjust the polarization direction of the array beam to maximize the output value of the array photodetectors.

[0031] In one embodiment, reference is made to Figure 6 A phase error detection module 10 is provided, including a liquid crystal phase modulator array plate 101, a convex lens 102, a pinhole 103, and a second photodetector 104. The array beam is incident on the liquid crystal phase modulator array plate 101 and finally received by the second photodetector 104.

[0032] The liquid crystal phase modulator array plate 101 has liquid crystal phase adjustment units 105 arranged in an array. The arrangement of the liquid crystal phase adjustment units 105 is the same as that of the array beam. Each unit beam in the array beam corresponds to one liquid crystal phase adjustment unit 105 on the liquid crystal phase modulator array plate 101. The liquid crystal phase modulator array plate 101 is loaded with a preset phase distribution map after the flipping operation. A small portion of the output array beam is collected and incident on the liquid crystal phase modulator array plate 101. In this way, the liquid crystal phase modulator array plate 101 introduces a set phase between the unit beams of the array beam. The phase difference, after passing through the liquid crystal phase modulator array plate 101, the array beam is received by the second photodetector 104 after passing through the convex lens 102 and the pinhole 103. The second photodetector 104 converts the optical signal into an electrical signal and transmits it to the phase noise signal processor 11. The phase noise signal processor 11 optimizes the phase difference compensation between each unit beam in the array beam after passing through the liquid crystal phase modulator array plate to be 0. It loads a phase control signal that is opposite to the preset phase distribution diagram after the flipping operation on the phase modulator corresponding to each sub-beam, so that the output array beam meets the preset phase distribution requirements.

[0033] The liquid crystal phase adjuster array 101 can be realized by fabricating a transmissive liquid crystal phase adjustment unit array on a glass substrate. The number and arrangement of the liquid crystal phase adjustment units 105 are set according to requirements and are not limited.

[0034] In one embodiment, the liquid crystal phase adjustment units 105 are arranged as follows: Figure 7 As shown, Figure 7 The array is presented in a square matrix form, but in practical applications, it can also be arranged in various other forms such as circular, rectangular, or polygonal arrays. Each liquid crystal phase adjustment unit 105 corresponds to an independent unit beam in the array beam, and different phase delays can be achieved according to the magnitude of the applied voltage. The spacing between each liquid crystal phase adjustment unit 105 is consistent with the spacing between the corresponding unit beams in the array beam.

[0035] The convex lens 102 can be a commercially available convex lens, with its operating wavelength matching the output wavelength of the seed source laser, and its aperture larger than the circumscribed circle diameter of the array beam. The pinhole 103 can be a commercially available pinhole, with its size comparable to the central main lobe size of the far-field interference spot focused by the convex lens. The second photodetector 104 can be a commercially available photodetector, required to have a response wavelength range covering the output wavelength of the seed source laser, and its photosensitive surface larger than the pinhole size.

[0036] The working principle of the phase error detection module is as follows: The phase error detection module does not need to detect the precise phase error between each beam. Instead, it actively introduces the required phase difference between each unit beam through the liquid crystal phase modulation array plate. Then, it uses a coherent synthesis method based on an optimization algorithm to make the phase difference of the beam array after passing through the liquid crystal phase modulation array plate zero.

[0037] The phase noise signal processor consists of a controller (which can be a computer, microcontroller, FPGA, etc.) and digital-to-analog and analog-to-digital conversion circuits. Its main function is to acquire the voltage signal output by the photodetector, and based on this, run optimization algorithms (such as SPGD algorithm, dithering method, etc.) to control the phase modulator, compensate for the phase noise of the array beam, and maximize the output value of the photodetector. At this time, the array beams on the back side of the liquid crystal phase modulator array plate remain in phase, and the phase distribution of the output beam meets the design requirements.

[0038] Figure 1 The illustrated embodiment also includes an optical field parameter controller 14, which consists of a controller (which may be a computer, microcontroller, FPGA, etc.) and digital-to-analog and analog-to-digital conversion circuits. The optical field parameter controller 14 has several functions. Firstly, it is used to load preset amplitude distribution requirements, preset phase distribution diagrams, and polarization state distribution requirements for the array beam. Secondly, it functions as an amplitude control unit, controlling the optical field parameter controller according to the preset amplitude distribution requirements of the array beam. n The fiber amplifier corresponding to the path beam amplifies the power accordingly, so that the output array beam meets the preset amplitude distribution requirements. Third, the optical field parameter controller 14, based on the preset polarization state distribution requirements of the array beam, sets the corresponding delay phase difference between the fast and slow axes for each liquid crystal delayer on the liquid crystal delayer array plate through voltage control. Fourth, based on the preset phase distribution diagram of the array beam, the optical field parameter controller 14 performs a flipping operation on the preset phase distribution diagram of the array beam and loads the flipped preset phase distribution diagram onto the liquid crystal phase modulator array plate. If the amplitude, polarization, and phase of the generated array beam need to change over time, the optical field parameter controller 14 needs to send the changing data to the corresponding detection or control module in real time.

[0039] like Figure 1In the illustrated embodiment, in the phase control loop, the optical field parameter controller first performs a flip operation on the phase distribution map to be loaded (the so-called flip operation refers to subtracting the corresponding phase of each unit beam from the phase π to obtain a new phase distribution map). Then, the phase distribution map after the flip operation is loaded onto the liquid crystal phase modulation plate in the phase error detection module. This introduces a specific phase difference between each unit beam. The phase noise signal processor will compensate the phase difference between each unit beam at the phase error detection module to 0. For this purpose, a phase control signal opposite to the flipped phase distribution map, i.e., the control signal corresponding to the originally designed phase distribution map, needs to be loaded on the phase modulator corresponding to each beam to obtain the desired phase distribution at the output beam.

[0040] like Figure 1 In the illustrated embodiment, within the polarization distribution control loop, the polarization direction detection module can form an independently controllable polarizer array based on an external loading signal. Each polarizer unit in the array corresponds to a single unit beam. During operation of the polarization distribution control loop, the optical field parameter controller first controls the polarization direction of each polarizer unit in the polarization direction detection module to align with the polarization direction distribution design. Subsequently, the polarization signal processor controls the polarization controller to ensure that the polarization direction of each unit beam meets the design requirements. At this point, the polarization direction detection module detects the polarization direction of the array beams. If a deviation occurs, the polarization direction controller will further adjust the polarization controller accordingly to ensure that its polarization direction matches the design.

[0041] The seed source laser 1 can be a commercial single-frequency or narrow-linewidth single-mode linearly polarized fiber laser, and its output wavelength can be designed according to requirements.

[0042] The fiber beam splitter 2 can be a commercial polarization-maintaining single-mode fiber beam splitter. The number of beams split is selected according to the requirements. If the number of beams split exceeds the number of beams split by a commercial beam splitter, it can be solved by cascading multiple fiber beam splitters. The type of its input fiber must match the type of its output fiber of the seed source laser 1.

[0043] The phase modulator 3 can be a commercial lithium niobate crystal electro-optic phase modulator or a piezoelectric ceramic phase modulator. The operating wavelength range of the modulator needs to cover the output wavelength of the seed source laser 1, and its power tolerance needs to meet the output power requirements of the beam splitter.

[0044] The polarization controller 4 can be a commercially available electrically controlled fiber optic polarization controller. The fiber of this controller is a non-polarization-maintaining single-mode fiber, and its core size must be the same as the core size of the output pigtail of the phase modulator 3. The polarization direction of the output beam can be controlled by electrical signals.

[0045] The fiber amplifier 5 can be a commercial single-mode fiber amplifier, which amplifies the power of the array beam and can adjust the output power by receiving external commands. Its input fiber type and input power must match the output fiber type and output power of the polarization controller 4.

[0046] The fiber collimator array 6 can be the high duty cycle rod lens collimator array described in the patent "Bar Lens Array Device for Beam Splicing and Synthesis of Fiber Laser Array" (Patent No.: 202110656820.6). The array can be a square array or a hexagonal close-packed array, and the aperture size of the array elements can be designed according to actual needs.

[0047] The first beam splitter 7 can be a commercial laser beam splitter. Its splitting ratio can be determined according to the output power of the array beam according to the following principles: ensuring that the reflected light power meets the requirements of subsequent applications, ensuring that the transmitted light power meets the requirements of the subsequent phase and polarization detection optical path, and its aperture is larger than the diameter of the outer circle of the array beam.

[0048] The second beam splitter 8 can be a commercial laser beam splitter, and its splitting ratio can be designed according to the actual needs of the phase error detection module and the polarization direction detection module. Its aperture is larger than the diameter of the outer circle of the array beam.

[0049] The reflector 9 can be a commercial laser reflector, whose aperture is larger than the diameter of the circumcircle of the array beam.

[0050] Matters not covered in this invention are common knowledge.

[0051] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0052] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for synthesizing optical fields based on fiber laser coherent arrays, characterized in that, include: n After undergoing processing including phase modulation, polarization control, and power amplification, the individual beams are combined into a single output beam using a preset array arrangement. Each unit beam in the output array beam corresponds to a pixel in the synthesized optical field. n The number of pixels is equal to the preset number of pixels in the composite light field, and the preset array arrangement corresponds to the preset arrangement of pixels in the composite light field. Control the amplitude distribution of the array beam according to the preset amplitude distribution requirements. n The power of the beam is amplified accordingly so that the output array beam meets the preset amplitude distribution requirements; A phase error detection module that acquires a small portion of the output array beam is used for phase control of the array beam: based on a preset phase distribution diagram of the array beam, the phase error is detected... n The phase of the output array beam is compensated and controlled to ensure that the output array beam meets the preset phase distribution requirements. The phase error detection module includes a liquid crystal phase modulator array plate, a convex lens, a pinhole camera, and a photodetector. Liquid crystal phase adjustment units are arranged in an array on the liquid crystal phase modulator array plate, with the arrangement of these units matching the array beam. Each unit beam in the array beam corresponds to a liquid crystal phase adjustment unit on the liquid crystal phase modulator array plate. The liquid crystal phase modulator array plate is loaded with a preset phase distribution map after a flipping operation. A small portion of the output array beam is collected and incident on the liquid crystal phase modulator array. On the board, a set phase difference is introduced between the unit beams of the array beam through the liquid crystal phase modulator array board. The array beam after passing through the liquid crystal phase modulator array board is received by the photodetector after passing through the convex lens and pinhole. The photodetector converts the optical signal into an electrical signal and transmits it to the phase noise signal processor. The phase noise signal processor takes the phase difference compensation between the unit beams of the array beam after passing through the liquid crystal phase modulator array board as the optimization target, and loads the phase control signal opposite to the preset phase distribution diagram after the flipping operation on the phase modulator corresponding to each sub-beam, so that the output array beam meets the preset phase distribution requirements. A small portion of the output array beam is collected by an input polarization direction detection module for array beam polarization control: the polarization direction of the array beam is detected, and if the polarization direction deviates from the preset polarization state distribution requirement, then... n The polarization direction of the beam is controlled so that the output array beam meets the preset polarization state distribution requirements. The polarization direction detection module includes a quarter-wave plate, a liquid crystal delay array plate, a polarization detection plate and a photodetector array plate. The fast axis and slow axis of the liquid crystal delay array plate are at an angle of 45° with the fast axis and slow axis of the quarter-wave plate. The polarization direction of the polarization detection plate is consistent with the fast axis of the quarter-wave plate. A small portion of the output array beam is incident from one side of a quarter-wave plate, passes through the quarter-wave plate, a liquid crystal retarder array plate, and a polarization detection plate, and is then received by a photodetector array plate. The liquid crystal retarder array plate contains liquid crystal retarders arranged in the same manner as the array beam. Each unit beam in the array beam corresponds to one liquid crystal retarder on the array plate. The fast and slow axes of all liquid crystal retarders are in the same direction, and the spacing between each liquid crystal retarder is consistent with the spacing between the unit beams in the corresponding array beam. Similarly, the photodetector array plate contains photodetectors arranged in the same manner as the array beam. Each unit beam in the array beam corresponds to one photodetector on the photodetector array plate, and the spacing between the photodetectors on the photodetector array plate is consistent with the spacing between the unit beams in the corresponding array beam. Based on the preset polarization state distribution requirements of the array beam, the corresponding delay phase difference between the fast and slow axes is set for each liquid crystal delay unit on the liquid crystal delay unit array plate through voltage control.

2. The method for synthesizing optical fields based on fiber laser coherent arrays according to claim 1, characterized in that, A small portion of the output array beam is incident on a quarter-wave plate. Based on the angle between the polarization direction of the incident beam and the fast and slow axes of the quarter-wave plate, each unit beam in the output beam of the quarter-wave plate is elliptically polarized, and the fast and slow axes of the elliptically polarized light are consistent with the fast and slow axes of the quarter-wave plate. Polarization control is applied to each sub-beam. When the elliptically polarized light output from the quarter-wave plate passes through the corresponding liquid crystal delay unit, different polarization states will be formed under different phase delay conditions. When the polarization state of the beam input to the liquid crystal delay unit is properly matched with the phase difference of the delay of the liquid crystal delay unit, the liquid crystal delay unit will output a linearly polarized beam with the same polarization direction as the polarization detection plate. At this time, the corresponding photodetector on the photodetector array plate will obtain the maximum optical power, thereby outputting the maximum voltage value. The array beam output at this time meets the preset polarization state distribution requirements.

3. A synthesized optical field device based on a fiber laser coherent array, characterized in that, include: An array beam generating optical path is used to output the array beam, which is composed of... n After undergoing processing including phase modulation, polarization control, and power amplification, the individual beams are combined into a single output beam using a preset array arrangement. Each unit beam in the array corresponds to a pixel in the synthesized light field. n The number of pixels is equal to the preset number of pixels in the composite light field, and the preset array arrangement corresponds to the preset arrangement of pixels in the composite light field. The amplitude control unit is used to control the amplitude distribution of the array beam according to the preset amplitude distribution requirements. n The power of the beam is amplified accordingly so that the output array beam meets the preset amplitude distribution requirements; A phase control loop is used to acquire a small portion of the output array beam for phase control of the array beam: based on a preset phase distribution diagram of the array beam, the phase of the array beam is controlled. n The phase of the output array beam is compensated and controlled to ensure that the phase distribution of the output array beam meets the preset phase distribution requirements. The phase control loop includes a phase error detection module and a phase noise signal processor. The phase error detection module includes a liquid crystal phase modulator array plate, a convex lens, a pinhole camera, and a photodetector. The liquid crystal phase modulator array plate has liquid crystal phase adjustment units arranged in an array, with the arrangement of the liquid crystal phase adjustment units being the same as that of the array beam. Each unit beam in the array beam corresponds to a liquid crystal phase adjustment unit on the liquid crystal phase modulator array plate. The liquid crystal phase modulator array plate is loaded with a preset phase distribution map after the flipping operation, and a small portion of the output array beam is collected. The array beam is incident on the liquid crystal phase modulator array plate, which introduces a set phase difference between the unit beams of the array beam. After passing through the liquid crystal phase modulator array plate, the array beam is received by a photodetector after passing through a convex lens and a pinhole. The photodetector converts the optical signal into an electrical signal and transmits it to the phase noise signal processor. The phase noise signal processor aims to make the phase difference compensation between the unit beams of the array beam after passing through the liquid crystal phase modulator array plate zero. It loads a phase control signal that is opposite to the preset phase distribution diagram after the flipping operation on the phase modulator corresponding to each sub-beam, so that the output array beam meets the preset phase distribution requirements. A polarization control loop is used to acquire a small portion of the output array beam for polarization control: the polarization direction of the array beam is detected, and if the polarization direction deviates from the preset polarization state distribution requirement, then... n The polarization direction of the beam is controlled so that the output array beam meets the preset polarization state distribution requirements. The polarization control loop includes a polarization direction detection module and a polarization signal processor. The polarization direction detection module includes a quarter-wave plate, a liquid crystal retarder array plate, a polarization detection plate, and a photodetector array plate. The liquid crystal retarder array plate has liquid crystal retarders arranged in the same way as the array beam. Each unit beam in the array beam corresponds to one liquid crystal retarder on the liquid crystal retarder array plate. The fast and slow axes of all liquid crystal retarders are the same, and the spacing between each liquid crystal retarder is consistent with the spacing between the unit beams in the corresponding array beam. The photodetector array plate has photodetectors arranged in the same way as the array beam. Each unit beam in the array beam corresponds to one photodetector on the photodetector array plate, and the spacing between each photodetector on the photodetector array plate is consistent with the spacing between the unit beams in the corresponding array beam. The fast and slow axes of the liquid crystal retarder array plate form an angle of 45° with the fast and slow axes of the quarter-wave plate. The polarization direction of the polarization detection plate is consistent with the fast axis direction of the quarter-wave plate. Each liquid crystal delay unit on the liquid crystal delay unit array plate is provided with a corresponding delay phase difference between its fast and slow axes. The delay phase difference between the fast and slow axes of each liquid crystal delay unit on the liquid crystal delay unit array plate is set according to the preset polarization state distribution requirements of the array beam.

4. The optical field synthesizing device based on a fiber laser coherent array according to claim 3, characterized in that, The array beam generation optical path includes a seed laser, an optical fiber beam splitter, a phase modulator, a polarization controller, an optical fiber amplifier, and an optical fiber collimator array. The laser output from the seed laser is split into beams by the optical fiber beam splitter. n Path beam, n The individual beams are respectively phase-modulated, polarized-controlled, and power-amplified by corresponding phase modulators, polarization controllers, and fiber amplifiers. Then, they are combined by a fiber collimator array and output into space to form an array beam. The fiber collimator array includes... n One fiber collimator n The fiber collimators are arranged in a preset array configuration so that the arrangement of the output array beam corresponds to the arrangement of pixels in the preset composite light field.

5. The optical field synthesizing device based on a fiber laser coherent array according to claim 4, characterized in that, The array beam output by the fiber collimator array after synthesis is split into two parts by the first beam splitter. Most of the beam is reflected by the first beam splitter and output to free space. A small portion of the beam transmitted by the first beam splitter is incident on the second beam splitter. The beam reflected by the second beam splitter is input into the polarization control circuit. The beam transmitted by the second beam splitter is input into the reflector and then into the phase control circuit.

6. The optical field synthesizer based on a fiber laser coherent array according to claim 3, 4, or 5, characterized in that, It also includes an optical field parameter controller, used to load the preset amplitude distribution requirements, preset phase distribution map, and polarization state distribution requirements of the array beam; The optical field parameter controller controls the beam according to the preset amplitude distribution requirements of the array beam. n The fiber amplifier corresponding to the path beam amplifies the power accordingly, so that the output array beam meets the preset amplitude distribution requirements. The optical field parameter controller sets the corresponding delay phase difference between the fast and slow axes for each liquid crystal delayer on the liquid crystal delayer array plate through voltage control, according to the preset polarization state distribution requirements of the array beam. The light field parameter controller flips the preset phase distribution map of the array beam and loads the flipped preset phase distribution map onto the liquid crystal phase tuner array plate.

7. The optical field synthesizing device based on a fiber laser coherent array according to claim 6, characterized in that, A small portion of the output array beam is incident from one side of the quarter-wave plate. Based on the angle between the polarization direction of the incident beam and the fast and slow axes of the quarter-wave plate, each unit beam in the output beam of the quarter-wave plate is elliptically polarized, and the fast and slow axes of the elliptically polarized light are consistent with the fast and slow axes of the quarter-wave plate. The polarization signal processor controls the polarization of each sub-beam through the polarization controller corresponding to each sub-beam. When the elliptically polarized light output from the quarter-wave plate passes through the corresponding liquid crystal delay unit, it will form different polarization states under different phase delay conditions. When the polarization state of the beam input to the liquid crystal delay unit and the delay phase difference of the liquid crystal delay unit are properly matched, the liquid crystal delay unit will output a linearly polarized beam with the same polarization direction as the polarization detection plate. At this time, the corresponding photodetector on the photodetector array plate will obtain the maximum optical power, thereby outputting the maximum voltage value. At this time, the output array beam meets the preset polarization state distribution requirements.

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