Distributed laser coherent combination system based on time division multiplexing

Abstract

The invention discloses a distributed laser coherent combination system based on time division multiplexing, belongs to the field of laser technology and application, and aims to solve the problem of high-precision phase locking in a large-scale laser coherent combination system. The specific operation mode is that seed laser is divided into N + 1 beams, one beam serves as reference light, N beams serve as output laser, and the seed laser is further divided into M sub-arrays; beam combination and collimation are respectively carried out on each sub-array, most laser is reflected by a high-reflectivity mirror as output, and an extremely small part of laser is transmitted as detection light; the time division multiplexing technology is adopted, the detection light of the M sub-arrays interferes with reference light in the center of a detector PD in different time periods, and obtained power signals in buckets serve as input of corresponding sub-array phase control algorithms; the phase control algorithm adjusts the control voltage of the phase modulator to enable the detection light phase of the M sub-arrays at the PD to be consistent with the reference light phase; and optical path compensation is carried out on the detection light of the M sub-arrays, so that the same phase when all the laser arrives at the transmitting end is ensured. According to the method, through the time division multiplexing technology, high-scale expansion of the number of synthesized lasers can be achieved theoretically, and on the premise that high convergence precision is guaranteed, the phase convergence speed is increased, and the system complexity is reduced.

Description

Technical field:

[0001] The invention relates to the technical field of laser coherent synthesis, and in particular to a distributed laser coherent synthesis system based on time division multiplexing. Background technology:

[0002] With the increasing demand for high-power and high-brightness laser sources, the output power of lasers continues to increase. However, single fiber lasers face challenges such as thermal damage and nonlinear effects during power amplification, which limit the output power to tens of kilowatts. To address this limitation, laser coherent synthesis technology has become a research hotspot. By combining multiple laser units, this technology can not only provide high-power output but also achieve high beam quality. In laser coherent synthesis systems, factors such as environmental disturbances and thermal effects will introduce dynamic phase noise, so it is crucial to achieve high-precision phase control. Traditional phase control methods include random parallel gradient algorithms, heterodyne methods, multi-jitter methods, and machine learning algorithms that have gradually developed in recent years. These methods have demonstrated their respective advantages in different application scenarios, but when faced with large-scale laser systems, a single centralized control method is often difficult to meet the requirements of high bandwidth and high precision. To meet this challenge, new laser coherent synthesis system structures have emerged, such as cascade and distribution. Distributed systems group multiple laser units into multiple sub-arrays and achieve phase control through distributed processing, which can effectively reduce system complexity while improving the accuracy and efficiency of phase control. In distributed systems, time-division multiplexing technology is used to control the detection light of different sub-arrays, interfering with the reference light in different time periods, thereby improving the overall performance of the system. In this way, the system can not only handle large-scale laser units, but also improve the phase convergence speed while ensuring high convergence accuracy. The flexible use of different phase control algorithms, combined with distributed architecture and time-division multiplexing technology, will provide a more efficient solution for large-scale laser coherent synthesis systems, which will help further promote the development of laser coherent synthesis technology. Summary of the invention:

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a distributed laser coherent combining system based on time division multiplexing. The system and method can effectively improve the phase control bandwidth and convergence accuracy in a large-scale coherent combining system and have high scalability.

[0004] The solution of the present invention to solve the above technical problems is: the system is used for large-scale phase control of N laser beams, and N laser beams and corresponding phase controllers are divided into M groups for distributed processing. The system device includes N phase controllers, M high-reflection mirrors, M adjustable liquid crystals, 1 reference light, 1 PD detector, 1 time-division multiplexing module, and a phase control algorithm module that can execute M tasks, multiple reflectors, etc. The specific implementation plan includes the following steps:

[0005] (S1), dividing the seed laser into N+1 beams, of which 1 beam is used as reference light and the remaining N beams are used as output lasers, and further dividing the N output laser beams into M sub-arrays according to system requirements;

[0006] (S2), combining and collimating the output lasers of each subarray, and reflecting most of the light through M high-reflection mirrors as the final output, and a small part of the transmitted light as the detection light;

[0007] (S3), using a time division multiplexing module to make the detection lights of the M sub-arrays interfere with the reference lights at the same PD center in different time periods, and transmitting the generated power signals in the barrels to the corresponding phase control algorithm modules respectively;

[0008] (S4), the phase control algorithm module applies control voltage to the phase modulator of each subarray in different time periods according to the power signal in the bucket received each time, so that the detection light phase of the M subarrays at the PD is consistent with the reference light phase;

[0009] (S5) Using adjustable liquid crystal to perform optical path compensation on the detection light of the M sub-arrays, the required compensation is conjugate with the optical path difference of the laser emitted between the sub-arrays to ensure that all output lasers have the same phase at the emission end.

[0010] Preferably, in step (S1), the N output laser beams are grouped, and the number of lasers in each group and the arrangement can be flexibly adjusted according to the specific needs of the system. The grouping method includes but is not limited to averaging and arbitrarily dividing into M groups, and the arrangement method includes but is not limited to triangle, square and regular hexagon.

[0011] Preferably, in step (S2), the transmittance and reflectance of the high-reflection mirror can be changed according to the laser output power and the relative intensity of the reference light, and the reflectance includes but is not limited to any value between 0.9 and 1. M independent drivers are used to adjust the reflection angle of the high-reflection mirror, and the emission angles of different output laser groups are flexibly controlled to achieve conformal emission.

[0012] Preferably, in step (S3), the phases of different sub-reference lights arriving at the transmitting end are precisely controlled by optical path compensation. This optical path compensation is adjusted according to the actual application of the system to control the phase difference of the output laser group when it reaches the target target surface. The specific circumstances of optical path compensation include but are not limited to: if the main goal of the system is to directly output high-power lasers, the optical path of the sub-reference light is adjusted so that the phase difference of all output laser groups when they arrive at the target target surface is zero; if the system is used for laser communication, optical path compensation is usually not required; if the system is used for beam shaping, the optical path of the sub-reference light should be adjusted to ensure that the output laser group forms the required specific beam phase difference when it reaches the target target surface.

[0013] Preferably, in step (S4), the input of the phase control algorithm module includes but is not limited to the barrel power detected by the PD, the maximum output power, the main lobe power, the synthetic beam quality factor, the pattern contrast of the far-field synthetic spot, and a combination of the above physical quantities.

[0014] The beneficial effects of the present invention compared with the prior art are:

[0015] 1. The present invention discloses a distributed laser coherent synthesis system based on time division multiplexing. The time division multiplexing technology is used to concentrate the detection light of different sub-arrays on one PD for interference in different time periods. This method significantly reduces the need for multiple detectors, thereby reducing hardware costs and system complexity. There is no need to configure independent photodetectors and related hardware for each group of detection light, which saves equipment procurement and maintenance costs and simplifies system design and operation. The time period can be flexibly adjusted under different operating conditions to meet the needs of different application scenarios, thereby further improving the adaptability and flexibility of the system.

[0016] 2. The present invention adopts time division multiplexing technology and uses one detector to collect and process data, which effectively reduces the interference caused by the interaction between multiple detectors. This centralized processing method improves the data processing efficiency and accuracy of the system. By reducing the number of detectors, the present invention reduces the possible noise and errors in the system and improves the overall measurement and control accuracy. Reducing the demand for detectors and related hardware directly reduces the procurement, installation and maintenance costs of the system. In addition, the simplified system design also reduces the complexity of engineering implementation and maintenance. The centralized use of one detector reduces the occupancy of physical space and is particularly suitable for application scenarios with limited space.

[0017] 3. The present invention provides a distributed laser coherent synthesis system based on time division multiplexing, which has significant flexibility and scalability. The system can arbitrarily group large-scale output lasers and their phase controllers according to actual needs. The grouping method is not limited to average distribution, and laser arrays in different groups can be arranged in a variety of ways. Its distributed structure enables the system to theoretically expand the number of laser beams infinitely. It only needs to reasonably increase the number of phase modulators, high-reflection mirrors and liquid crystals to achieve the merging and expansion of coherent synthesis systems of any scale, thereby providing strong compatibility and flexibility.

[0018] 4. The present invention uses an independent driver to adjust the reflection angle of the high-reflection mirror, achieving precise control of the emission angles of different output laser groups, thereby improving the tilt control accuracy and structural flexibility of the system. According to system requirements, the optical path compensation of the sub-array detection light can effectively control the phase difference of the output laser group on the target surface, thereby enhancing the adaptability of the system. In addition, the system of the present invention can be multiplexed into a laser communication system and a beam shaping system. By adjusting the reflection direction of the high-reflection mirror, the laser beam can be aimed at different communication targets to achieve multi-point laser communication. This multifunctional feature expands the application range of the system. Description of the drawings:

[0019] Figure 1 A block diagram of a distributed laser coherent synthesis system for any number of lasers of the present invention;

[0020] Figure 2 A block diagram of a distributed laser coherent synthesis system according to a specific embodiment of the present invention;

[0021] Figure 3 is an arrangement diagram of sub-array lasers of a specific embodiment of the present invention;

[0022] Figure 4 The figure is a flow chart of a specific implementation case of the present invention. Specific implementation method:

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0024] Figure 1 The block diagram of the distributed laser coherent synthesis system of the present invention is universal for any number of lasers. Figure 2 The block diagram of the distributed laser coherent synthesis system of this specific embodiment is used for large-scale beam phase control of 3×61 beams. The 183 output laser beams and the corresponding phase controllers are divided into 3 identical sub-arrays for distributed processing. The arrangement of the sub-arrays Figure 3The system device includes 183 phase controllers, 3 high-reflection mirrors, 1 PD, 1 time-division multiplexing algorithm module, and 1 phase control algorithm module. The final object controlled by the system is the phase of each laser beam.

[0025] See also Figure 4 The present invention is used in this embodiment of a distributed laser coherent synthesis system based on time division multiplexing, which includes the following steps:

[0026] (S1) The seed laser is divided into 184 beams, of which 1 beam is used as a reference beam and 183 beams are used as output lasers. According to the actual needs of the system, the 183 output laser beams and 183 phase controllers are divided into 3 sub-arrays at the same time. The grouping method is evenly distributed, and the number of paths in each group is 61, and the arrangement method is a regular hexagon;

[0027] (S2) collimating and combining the three sub-array lasers respectively, using the low-power transmitted light after passing through the three high-reflection mirrors as the detection laser group, and the high-power reflected light as the final output, adjusting the angles of the three high-reflection mirrors so that different laser groups are directed to the same target surface, wherein the transmittance and reflectance of the high-reflection mirrors can be changed according to demand. In this embodiment, the reflectance is set to 0.99, and three independent drivers are used to adjust the reflection angle of the high-reflection mirror. The emission angles of different output laser groups are flexibly controlled to complete collimation, and the emission direction of the detection laser group after transmission through the high-reflection mirror remains unchanged;

[0028] (S3), using the time division multiplexing module to first activate the detection light of subarray 1 within the set time period, interfere with the reference light, and the power signal in the bucket measured by the detector is recorded and processed. Then, the system switches to the next time period, activates the detection light of subarray 2 and subarray 3 in turn, and repeats the above interference and signal measurement process. The interference signal generated in each time period is respectively transmitted to the corresponding phase control algorithm module for calculating and adjusting the phase control of the laser array;

[0029] (S4), the phase control algorithm module processes the power signal in the bucket each time it is received, and first inputs the measured power signal into the algorithm module. The algorithm module compares these signals with the preset target signal and calculates the deviation between the current system phase and the reference light phase. Based on these deviations, the algorithm module iteratively adjusts the control voltage of the phase modulator to gradually reduce the phase difference between the detection light and the reference light. This process continuously updates and optimizes the control voltage so that the detection light phases of the three subarrays can gradually approach the reference light phase, and ultimately achieve precise phase consistency.

[0030] (S5) accurately measure the actual optical path length of the detection light of the three subarrays to determine the optical path length difference relative to the reference light. Based on these optical path length differences, calculate the required compensation amount and use liquid crystal to perform corresponding optical path length compensation on each subarray. The required compensation is conjugate to the optical path length difference of the laser emitted between the subarrays. Finally, the emitted lasers of all subarrays have the same phase when they arrive at the target surface.

[0031] The above is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited to the above content. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A distributed laser coherent combining system based on time division multiplexing, characterized in that: The system is used for large-scale phase control of N light beams. N laser beams and corresponding phase controllers are divided into M groups for distributed processing. The system device includes N phase controllers, M high-reflection mirrors, M adjustable liquid crystals, 1 reference light, 1 PD (photo detector), 1 time-division multiplexing module, a phase control algorithm module that can execute M tasks, and multiple reflectors.

2. A distributed laser coherent combining system based on time division multiplexing according to claim 1, characterized in that The following steps are involved: (S1), dividing the seed laser into N+1 beams, of which 1 beam is used as reference light and the remaining N beams are used as output lasers, and further dividing the N output laser beams into M sub-arrays according to system requirements; (S2), combining and collimating the output lasers of each subarray, and reflecting most of the light through M high-reflection mirrors as the final output, and a small part of the transmitted light as the detection light; (S3), using a time division multiplexing module to make the detection lights of the M sub-arrays interfere with the reference lights at the same PD center in different time periods, and transmitting the generated power signals in the barrels to the corresponding phase control algorithm modules respectively; (S4), the phase control algorithm module applies control voltage to the phase modulator of each subarray in different time periods according to the power signal in the bucket received each time, so that the detection light phase of the M subarrays at the PD is consistent with the reference light phase; (S5) Using adjustable liquid crystal to perform optical path compensation on the detection light of the M sub-arrays, the required compensation is conjugate with the optical path difference of the laser emitted between the sub-arrays to ensure that all output lasers have the same phase at the emission end.

3. The system structure according to claim 2, characterized in that: In step (S1), the entire laser array is grouped according to system requirements. The grouping method can be flexibly adjusted. The arrangement of the sub-arrays can include but is not limited to equal division or grouping in any manner, and arranged in a triangle, rectangle or hexagon.

4. The system structure according to claim 2, characterized in that: In step (S2), different high-reflection mirrors are selected according to the laser output power, with a reflectivity range of 0.9 to 1 to adapt to the power of the reference light. An independent driver is used to adjust the reflection angle of the high-reflection mirror to control the emission direction of the output light of different sub-arrays, so that different sub-arrays converge on the same emission plane.

5. The system structure according to claim 2, characterized in that: In step (S4), the selection of the phase control algorithm can be adjusted according to system requirements, including but not limited to the SPGD algorithm and other suitable phase control algorithms, to quickly ensure that the phase of the detection light of the M subarrays at the PD is consistent with the phase of the reference light.

6. The distributed laser coherent combining system based on time division multiplexing according to claim 2, characterized in that: In step (S5), the phases of different sub-arrays arriving at the transmitting end are controlled by optical path compensation. The optical path compensation is performed according to the actual needs of the system to control the phase difference between the output laser groups arriving at the target target surface. The optical path compensation includes but is not limited to the following three situations: (1) If the purpose of the coherent combining system is to directly output high-power lasers, the phase difference between the output laser groups when they reach the target surface is zero by performing optical path compensation on the sub-reference beams; (2) If the coherent combining system is multiplexed into a laser communication system, optical path compensation is not required; (3) If the coherent combining system is multiplexed into a beam shaping system, the optical path of the sub-reference light can be compensated so that the output laser groups have the phase difference required to form the target beam when they arrive at the target surface.

7. The distributed laser coherent combining system based on time division multiplexing according to claim 2, characterized in that: In step (S3), the input of the phase control algorithm module includes but is not limited to the barrel power detected by the PD, the maximum output power, the main lobe power, the synthetic beam quality factor, the pattern contrast of the far-field synthetic spot, and a combination of the above physical quantities.

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