Multi-channel polarization phase active control system and method for sub-aperture coherent synthesis system

Abstract

The application discloses a multi-channel polarization phase active control system and method of a split-aperture coherent synthesis system, relates to the technical field of split-aperture coherent synthesis, and comprises a detection module and a control module. The detection module samples coherent synthesis light, synthesizes and detects sampled light and reference light, obtains a first detection signal and a second detection signal, the control system demodulates the first detection signal, obtains a phase error signal corresponding to each split beam, controls each phase modulator to work based on the phase error signal corresponding to each split beam, adjusts the phase of each split beam, demodulates the second detection signal, obtains a polarization error signal corresponding to each split beam, and controls each polarization controller to work based on the polarization error signal corresponding to each split beam, so as to adjust the polarization of each split beam. The application can realize multi-channel polarization phase active control with high control speed under the condition of low system complexity.

Description

Technical Field

[0001] This application relates to the field of aperture-based coherent synthesis technology, and in particular to a multi-path polarization phase active control system and method for aperture-based coherent synthesis systems. Background Technology

[0002] Coherent combining technology can improve laser power while maintaining beam quality, making it an effective technical approach to overcome the single-aperture output power limitation of high-energy lasers. Coherent combining technology requires that all laser beams have the same polarization and phase synchronization. Polarization can be achieved through two methods: a fully polarization-maintaining laser amplification system or active polarization control of a non-polarization-maintaining laser amplification system. On the one hand, fully polarization-maintaining fiber devices are expensive and have complex manufacturing processes, leading to higher costs for fully polarization-maintaining laser amplification systems. On the other hand, the lower nonlinearity threshold in fully polarization-maintaining fiber amplifiers limits the output power level of such systems. Therefore, active polarization control of the non-polarization-maintaining laser amplification system offers advantages in reducing costs and increasing output power, which is of great significance for the design and implementation of coherent combining systems. Phase synchronization typically employs active phase control methods to correct phase noise caused by factors such as thermal effects, mechanical vibration, airflow disturbances, and power supply noise, thus achieving phase synchronization.

[0003] Both active polarization control and active phase control are based on certain error detection methods and optimization algorithms to control the polarization controller and phase modulator, ensuring that the polarization of each laser path is the same and the phase is synchronized. Currently, single-path polarization control and multi-path phase control technologies are relatively mature. Although theoretically, multi-path polarization control can be directly extended from single-path polarization control, it requires setting up multiple single-path control modules (including detection devices and control circuits) to detect each laser path separately and further control the polarization of each laser path separately. Obviously, this requires a significant increase in detection devices and control circuits, greatly increasing the system complexity, which increases with the number of laser paths. The technique of controlling multiple polarization paths simultaneously by sampling and probing the beam only once can greatly simplify the system structure, but it presents significant technical challenges. For example, sampling and probing the composite beam of multiple lasers only once generates a probe signal. Then, based on this probe signal, gradient optimization algorithms such as SPGD (Stochastic Parallel Gradient Descent) are used to simultaneously control the polarization of each laser path. However, due to the randomness and blind optimization characteristics of the SPGD algorithm, the control speed decreases as the number of laser paths increases, making it difficult to apply to large-scale systems. Furthermore, there is currently no scheme for simultaneously and actively controlling the polarization phase of multiple paths. Summary of the Invention

[0004] The purpose of this application is to provide a multi-path polarization phase active control system and method for a multi-aperture coherent combining system, which can simultaneously realize multi-path polarization phase active control. The system complexity and control speed do not change with the number of laser paths. Under the condition of low system complexity, high control speed multi-path polarization phase active control is achieved.

[0005] To achieve the above objectives, this application provides the following solution.

[0006] In a first aspect, this application provides a multi-path polarization phase active control system for a multi-aperture coherent synthesis system, comprising: a detection module and a control module;

[0007] The detection module is used to sample the coherent combined light output from the aperture-splitting coherent combining system to obtain sampled light, and then combine the sampled light and the reference light twice to obtain a first combined light and a second combined light. The first combined light and the second combined light are then detected to obtain a first detection signal and a second detection signal. The reference light is a collimated beam output from the beam splitter in the aperture-splitting coherent combining system. The first combined light is the combined light obtained by combining the sampled light and the reference light, and the second combined light is the combined light obtained by combining the sampled light and the reference light after a 90-degree phase shift.

[0008] The control module includes a control system, multiple phase modulators, and multiple polarization controllers. Each phase modulator and polarization controller corresponds one-to-one with the other split beams output by the beam splitter besides the reference beam. Each phase modulator applies a modulation signal, and the modulation angular frequency of the modulation signal applied by different phase modulators is different. The control system demodulates the first detection signal to obtain a phase error signal corresponding to each split beam, and controls each phase modulator to adjust the phase of each split beam based on the phase error signal. Then, it demodulates the second detection signal to obtain a polarization error signal corresponding to each split beam, and controls each polarization controller to adjust the polarization of each split beam based on the polarization error signal.

[0009] Optionally, the detection module includes a sampling mirror, a synthesizer, a first detector, and a second detector; the sampling mirror is used to sample the coherent synthesized light output by the aperture-splitting coherent synthesizing system to obtain sampled light; the synthesizer is used to synthesize the sampled light and the reference light twice to obtain a first synthesized light and a second synthesized light; the first detector is used to detect the first synthesized light to obtain a first detection signal; the second detector is used to detect the second synthesized light to obtain a second detection signal.

[0010] Optionally, the synthesizer is a 90° optical mixer;

[0011] The first detector includes a first polarizer, a first focusing lens, and a first photodetector. The first polarizer is used to convert the first composite light into first composite polarized light. The first focusing lens is used to focus the first composite polarized light to obtain first composite focused light. The first photodetector is used to perform photoelectric conversion on the first composite focused light to obtain a first detection signal.

[0012] The second detector includes a second polarizer, a second focusing lens, and a second photodetector. The second polarizer is used to convert the second composite light into a second composite polarized light. The second focusing lens is used to focus the second composite polarized light to obtain a second composite focused light. The second photodetector is used to perform photoelectric conversion on the second composite focused light to obtain a second detection signal.

[0013] Optionally, the aperture-splitting coherent combining system includes: a laser module and a beam combining module;

[0014] The laser module includes a seed laser, a first laser amplifier, a beam splitter, multiple second laser amplifiers, multiple first collimators, and a second collimator. The seed laser emits a seed laser beam. The first laser amplifier amplifies the seed laser beam to obtain an amplified laser beam. The beam splitter splits the amplified laser beam into multiple beams and an output beam. The second laser amplifiers and the first collimators correspond one-to-one with the beams. The second laser amplifier amplifies the beams to obtain amplified beams. The first collimator collimates the amplified beams to obtain collimated beams. The second collimator collimates the output beam to obtain the reference beam.

[0015] The beam combining module is used to coherently combine all the collimated and split beams.

[0016] Optionally, the phase modulator and the polarization controller are located between the beam splitter and the second laser amplifier. The phase modulator is used to modulate the phase of the split beam to obtain phase-modulated split beam, and the polarization controller is used to control the polarization of the phase-modulated split beam to obtain polarization-controlled split beam. All the polarization-controlled split beams are amplified by the second laser amplifier and collimated by the first collimator, and then combined by the beam combining module to form the coherent combined beam.

[0017] Secondly, this application provides a multi-path polarization phase active control method for a multi-aperture coherent combining system, which operates based on the aforementioned multi-path polarization phase active control system for the multi-aperture coherent combining system, including:

[0018] Acquire the first and second detection signals output by the detection module;

[0019] The first detection signal is demodulated to obtain the phase error signal corresponding to each beam, and each phase modulator is controlled based on the phase error signal corresponding to each beam to adjust the phase of each beam.

[0020] The second detection signal is demodulated to obtain the polarization error signal corresponding to each beam, and each polarization controller is controlled based on the polarization error signal corresponding to each beam to adjust the polarization of each beam.

[0021] Optionally, the first detection signal is demodulated to obtain the phase error signal corresponding to each beam, specifically including: demodulating the first detection signal using a coherent radio frequency demodulation method to obtain the phase error signal corresponding to each beam;

[0022] Demodulating the second detection signal to obtain the polarization error signal corresponding to each beam split specifically includes: using a coherent radio frequency demodulation method to demodulate the second detection signal to obtain the polarization error signal corresponding to each beam split.

[0023] Optionally, the formula for calculating the phase error signal is:

[0024] ;

[0025] in, For the first Phase error signal corresponding to the split beam; The integration time; For the first The modulation angular frequency of the split beam; For a specific moment; for The first detection signal at that moment; is the voltage conversion coefficient of the photodetector; For the first The power of the split beam illuminating the detection surface of the photodetector; It is a first-order Bessel function of the first kind; For the first Phase modulation depth of beam splitter; The number of beams; For the first The power of the split beam illuminating the detection surface of the photodetector; It is a Bessel function of the first kind, order 0; For the first Phase modulation depth of beam splitter; For the first The phase of the split beam in the main polarization direction; For the first The phase of the split beam in the main polarization direction;

[0026] The formula for calculating the polarization error signal is as follows:

[0027] ;

[0028] in, For the first Polarization error signal corresponding to beam splitting; For the first The power of the split beam illuminating the detection surface of the photodetector; the 0th split beam is the reference beam.

[0029] Optionally, each phase modulator is controlled to operate based on the phase error signal corresponding to each beam splitter in order to adjust the phase of each beam splitter. Specifically, for each beam splitter, the phase modulator corresponding to the beam splitter is controlled to operate based on the phase error signal corresponding to the beam splitter, and the phase of the beam splitter is adjusted to the updated phase.

[0030] The formula for calculating the updated phase is:

[0031] ;

[0032] in, For the first The updated phase of the split beam; For the first Phase of the split beam; For feedback coefficients; For the first Phase error signal corresponding to the split beam.

[0033] Optionally, each polarization controller is controlled based on the polarization error signal corresponding to each beam to adjust the polarization of each beam. Specifically, for each beam, the polarization error signal corresponding to the beam is used as input, and the SPGD algorithm is used to control the polarization controller corresponding to the beam to adjust the polarization of the beam.

[0034] According to the specific embodiments provided in this application, this application has the following technical effects.

[0035] This application provides a multi-path polarization phase active control system and method for a multi-aperture coherent combining system, comprising: a detection module and a control module. The detection module samples the coherent combined light output by the multi-aperture coherent combining system to obtain sampled light, and combines the sampled light and a reference light twice to obtain a first combined light and a second combined light. The first combined light and the second combined light are detected respectively to obtain a first detection signal and a second detection signal. The control module includes a control system, multiple phase modulators and multiple polarization controllers. The phase modulators and polarization controllers correspond one-to-one with the other beams output by the beam splitter except for the reference light. The phase modulators apply modulation signals, and the modulation angular frequencies of the modulation signals applied by different phase modulators are different. The control system demodulates the first detection signal to obtain a phase error signal corresponding to each beam, and controls each phase modulator to operate based on the phase error signal corresponding to each beam to adjust the phase of each beam. Then, the second detection signal is demodulated to obtain a polarization error signal corresponding to each beam, and controls each polarization controller to operate based on the polarization error signal corresponding to each beam to adjust the polarization of each beam. This application achieves two-stage synthesis using a sampling beam and a reference beam, and applies a modulation signal using a phase modulator. Different phase modulators apply modulation signals with different modulation angular frequencies. A first and second detection signal can be obtained through a single sampling and detection. Demodulation of these signals allows simultaneous control of multiple phase modulators and polarization controllers. This enables simultaneous active control of multiple polarization phases by sampling and detecting the beam only once, without requiring individual detection of each laser path, thus reducing system complexity and simplifying the system structure. Furthermore, in this active multi-path polarization control, only one sampling and detection of the beam is performed to control multiple polarization paths simultaneously, and control is based on polarization error signals, avoiding the blind optimization of traditional optimization algorithms. System complexity and control speed remain unchanged with the number of laser paths, achieving high control speed active multi-path polarization phase control under low system complexity conditions. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the optical path structure of a multi-path polarization phase active control system for a coherent synthesis system with different apertures, provided in Embodiment 1 of this application.

[0038] Figure 2 This is a schematic diagram of the simulation results of the seven-channel hexagonally arranged coherent combining system with different apertures provided in Embodiment 1 of this application; wherein, Figure 2 (a) in the figure represents the simulation results when the reference beam coincides only with the central beam splitter in the near field; Figure 2 (b) in the figure shows the simulation results when the reference light coincides with all the beams in the near field.

[0039] Figure 3 This is a flowchart illustrating a multi-path polarization phase active control method for a coherent synthesis system with varying apertures, as provided in Embodiment 2 of this application.

[0040] Figure 4 This is a schematic diagram of the structure of a computer device provided in Embodiment 3 of this application. Detailed Implementation

[0041] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0042] Example 1.

[0043] This embodiment provides a multi-path polarization phase active control system for a multi-aperture coherent synthesis system, including a detection module and a control module.

[0044] The detection module is used to sample the coherent combined light output from the aperture-splitting coherent combining system to obtain sampled light. The sampled light and the reference light are combined twice to obtain a first combined light and a second combined light. The first combined light and the second combined light are detected to obtain a first detection signal and a second detection signal. The reference light is a beam output from the beam splitter in the aperture-splitting coherent combining system and collimated. The first combined light is the combined light obtained by combining the sampled light and the reference light. The second combined light is the combined light obtained by combining the sampled light and the reference light after a 90-degree phase shift.

[0045] The control module includes a control system, multiple phase modulators, and multiple polarization controllers. Each phase modulator and polarization controller corresponds one-to-one with the other beams output by the beam splitter, excluding the reference beam. The phase modulators apply modulation signals, and the modulation angular frequencies of the modulation signals applied by different phase modulators are different. The control system demodulates the first detection signal to obtain the phase error signal corresponding to each beam, and controls each phase modulator to adjust the phase of each beam based on the phase error signal corresponding to each beam. Then, it demodulates the second detection signal to obtain the polarization error signal corresponding to each beam, and controls each polarization controller to adjust the polarization of each beam based on the polarization error signal corresponding to each beam.

[0046] This embodiment provides a multi-path polarization phase active control system for aperture-splitting coherent combining systems. This system is applicable to aperture-splitting coherent combining systems. Currently, a foreign research team has achieved simultaneous polarization and phase control of five non-polarization-maintaining lasers based on a multi-jitter method, and has also achieved high-power coherent combining of three 2.4 kW lasers based on the same method. However, the technical details of this multi-jitter method are unknown, and it has only been verified in a common-aperture coherent combining system. It is unclear whether it can be used in aperture-splitting coherent combining systems and how to use it, limiting its application scope. To overcome these technical difficulties, this embodiment proposes a multi-path polarization phase active control system based on the multi-jitter method, applicable to aperture-splitting coherent combining systems. This allows for the application of multi-path polarization phase active control technology in aperture-splitting coherent combining systems, expanding the application scope of the multi-jitter method.

[0047] The multi-path polarization phase active control system of the aperture-splitting coherent combining system in this embodiment mainly involves the active control of the multi-path polarization phase of the aperture-splitting coherent combining system, such as... Figure 1 As shown, the aperture-splitting coherent combining system of this embodiment will be introduced first. The aperture-splitting coherent combining system includes a laser module and a beam combining module. The laser module includes a seed laser, a first laser amplifier, a beam splitter, N second laser amplifiers, and N first collimators and second collimators, where N is the number of beam splitters. The beam combining module includes a beam combining system.

[0048] The seed laser emitted by the seed laser is amplified by the first laser amplifier and then split into N+1 paths by the beam splitter. One of these paths is collimated by the second collimator and used as the reference light, while the other N paths are used as split beams. The N split beams are amplified by the second laser amplifier and collimated by the first collimator, respectively, and then emitted by the first collimator and incident on the beam combining system to be combined into a single laser beam.

[0049] In this embodiment, the aperture-splitting coherent combining system includes a laser module and a beam combining module.

[0050] The laser module includes a seed laser, a first laser amplifier, a beam splitter, multiple second laser amplifiers, multiple first collimators, and a second collimator. The seed laser emits a seed laser beam. The first laser amplifier amplifies the seed laser beam to obtain an amplified laser beam. The beam splitter splits the amplified laser beam into multiple split beams and an output beam. The second laser amplifiers and first collimators correspond one-to-one with the split beams. The second laser amplifiers amplify the split beams to obtain amplified split beams. The first collimators collimate the amplified split beams to obtain collimated split beams. The second collimator collimates the output beam to obtain a reference beam.

[0051] The beam combining module is used to coherently combine all collimated beams.

[0052] It should be noted that the structure of the above-described aperture-division coherent synthesis system is only one example of this embodiment. Of course, this embodiment can also be applied to aperture-division coherent synthesis systems with other structures. The structure of the aperture-division coherent synthesis system disclosed above should not be construed as a limitation of this embodiment.

[0053] like Figure 1 As shown, the multi-path polarization phase active control system of the aperture coherent combining system used in this embodiment will be introduced. The multi-path polarization phase active control system of the aperture coherent combining system includes a detection module and a control module. The detection module includes a sampling mirror, a 90° optical mixer, two polarizers, two focusing lenses, and two photodetectors. The control module includes a control system, N phase modulators, and N polarization controllers. Small-amplitude sinusoidal modulation signals with different modulation angular frequencies are applied to the phase modulators. The modulation angular frequency and amplitude can be determined according to user requirements.

[0054] The seed laser emitted by the seed laser is amplified by the first laser amplifier and then split into N+1 paths by the beam splitter. One path is collimated by the second collimator and used as the reference beam. The remaining N paths are split beams, which are phase-modulated by the phase modulator, polarization-controlled by the polarization controller, and amplified by the second laser amplifier. After being collimated by the first collimator, they are emitted and incident on the beam combining system to form a coherent composite beam. After beam combining, a small portion of the coherent composite beam with a sampling mirror is extracted for detection to obtain the sample beam. This sample beam and the reference beam are input together into a 90° optical mixer, which outputs two different composite laser beams, namely the first composite beam and the second composite beam. These beams then pass through a polarizer and a focusing lens and are incident on two photodetectors to generate different detection signals, namely the first detection signal and the second detection signal. Inside the 90° optical mixer, both the reference beam and the sampling beam are split into two. One beam of the reference beam is combined with one beam of the sampling beam to produce a first composite beam. After passing through a polarizer and a focusing lens, the first composite beam generates a first detection signal on the photodetector, denoted as [missing information]. The other reference beam undergoes a 90° phase shift before being combined with the other sampling beam to produce a second composite beam. This second composite beam, after passing through a polarizer and focusing lens, generates a second detection signal on the photodetector, denoted as [significant signal]. Two detection signals are input into the control system together, among which... Used for phase control For polarization control, the phase error signal and polarization error signal of each beam splitter are demodulated by coherent radio frequency demodulation method. Based on the phase error signal and polarization error signal, the control voltage of the phase modulator and polarization controller are adjusted to change the phase and polarization of the beam splitter, and gradually achieve phase synchronization and polarization sameness.

[0055] In this embodiment, the detection module samples the coherent combined light output from the aperture-splitting coherent combining system to obtain sampled light. The sampled light and reference light are combined twice to obtain a first combined light and a second combined light. The first and second combined lights are then detected to obtain a first detection signal and a second detection signal. The control module includes a control system, multiple phase modulators, and multiple polarization controllers. Each phase modulator and polarization controller corresponds one-to-one with the other split beams output from the beam splitter besides the reference light. The phase modulators apply modulation signals, and the modulation angular frequencies of the modulation signals applied by different phase modulators are different. The phase modulators and polarization controllers are located between the beam splitter and the second laser amplifier. The phase modulators modulate the phase of the split beams to obtain phase-modulated split beams, and the polarization controllers control the polarization of the phase-modulated split beams to obtain polarization-controlled split beams. All polarization controllers... After being amplified by a second laser amplifier and collimated by a first collimator, the split beams are combined into coherent composite beams by a beam combining module. The control system demodulates the first detection signal to obtain the phase error signal corresponding to each split beam, and controls each phase modulator to adjust the phase of each split beam based on the phase error signal corresponding to each split beam. Then, the second detection signal is demodulated to obtain the polarization error signal corresponding to each split beam, and controls each polarization controller to adjust the polarization of each split beam based on the polarization error signal corresponding to each split beam.

[0056] The detection module includes a sampling mirror, a synthesizer, a first detector, and a second detector. The sampling mirror is used to sample the coherent synthesized light output by the aperture-splitting coherent synthesizing system to obtain sampled light. The synthesizer is used to synthesize the sampled light and the reference light twice to obtain a first synthesized light and a second synthesized light. The first detector is used to detect the first synthesized light to obtain a first detection signal. The second detector is used to detect the second synthesized light to obtain a second detection signal.

[0057] The synthesizer is a 90° optical mixer. The first detector includes a first polarizer, a first focusing lens, and a first photodetector. The first polarizer converts the first synthesized light into first synthesized polarized light, the first focusing lens focuses the first synthesized polarized light to obtain first synthesized focused light, and the first photodetector performs photoelectric conversion on the first synthesized focused light to obtain a first detection signal. The second detector includes a second polarizer, a second focusing lens, and a second photodetector. The second polarizer converts the second synthesized light into second synthesized polarized light, the second focusing lens focuses the second synthesized polarized light to obtain second synthesized focused light, and the second photodetector performs photoelectric conversion on the second synthesized focused light to obtain a second detection signal.

[0058] In addition to using a 90° optical mixer, other optical path structures can be used to synthesize the reference light and the sampling light, but it is necessary to ensure that there is a 90-degree phase difference between the reference light and the sampling light in the second synthesized light used for polarization control.

[0059] The control system in this embodiment uses a multi-jitter method. The execution steps of the multi-jitter method are as follows (integral time is...). (The specific duration depends on user needs): Collect the first detection signal. Second detection signal From time At that time , respectively , Demodulation was performed to obtain the phase error signals of each beam. Polarization error signal And based on the phase error signal To control the operation of the phase modulator, every Then, the phase modulator is controlled once, and the polarization error signal is stored simultaneously. When the control time is reached At this point, phase modulation is complete, and the phases of all beams are synchronized, based on the polarization error signal. To control the operation of the polarization controller, every Then, the polarization controller is controlled once until polarization control is complete, and the polarization of each beam is the same. The specific duration depends on the user's needs. Compare By selecting different orders of magnitude, the control processes of phase synchronization and polarization synchronization are made to ensure that they do not interfere with each other, thus guaranteeing that the laser phase is synchronized during polarization control.

[0060] Phase error signal and polarization error signal The process of determining is as follows.

[0061] For phase control, each beam is modulated with a different modulation angular frequency, the first... The radio frequency modulation angular frequency (i.e., modulation angular frequency) of the beam splitter is: Phase modulation depth is The reference light (i.e., the 0th beam splitter) is not modulated (i.e., =0), according to the principle of light wave superposition, the composite light field of the first composite light after polarization. and the first detection signal for:

[0062] (1);

[0063] In equation (1), For a specific moment; The number of beams; For the first The amplitude of the split beam in the main polarization direction; The laser's central angular frequency; For the first The phase of the split beam in the main polarization direction; For the first Phase modulation depth of beam splitter; For the first The modulation angular frequency of the split beam; is the voltage conversion coefficient of the photodetector; The detection area of ​​the photodetector; These are the vacuum dielectric constant, the air refractive index, and the speed of light, respectively. Represents the average time.

[0064] The first detection signal Multiplied by the sinusoidal modulation signal of each beam splitter and during the integration time Inner integration, further approximating using the Bessel expansion formula of trigonometric functions, retaining only the first two orders, yields the phase error signals for each beam:

[0065] (2);

[0066] In equation (2), For the first Phase error signal corresponding to the split beam; The integration time; For the first The modulation angular frequency of the split beam; For a specific moment; for The first detection signal at that moment; is the voltage conversion coefficient of the photodetector; For the first The power of the split beam illuminating the detection surface of the photodetector; It is a first-order Bessel function of the first kind; For the first Phase modulation depth of beam splitter; The number of beams; For the first The power of the split beam illuminating the detection surface of the photodetector; It is a Bessel function of the first kind, order 0; For the first Phase modulation depth of beam splitter; For the first The phase of the split beam in the main polarization direction; For the first The phase of the split beam in the main polarization direction.

[0067] In the above formula (2), (for example 、 The power of each beam of light incident on the detection surface of the photodetector is denoted as . , The phase error signal represents the amplitude of each beam in the main polarization direction. The average sinusoidal phase distance between the beam splitter and other beam splitters can be controlled by feedback to bring the phase error signal of each beam splitter close to 0, thereby achieving phase synchronization between the beam splitters.

[0068] For polarization control, the second detection signal is , with the first detection signal The difference lies in the phase change of the reference light by 90° (the phase after the change). =Phase before change +90°), similar to Equation (1) and Equation (2) for demodulation, only the phase of the 0th beam needs to be noted, when the phases of all beams are synchronized ( - ≈0, ), In equation (2) arrive All items are 0, leaving only 0. One of them, and Therefore, by approximating the phase difference between each path to approximately 0, the polarization error signal is calculated as follows:

[0069] (3);

[0070] In equation (3), For the first Polarization error signal corresponding to beam splitting; For the first The phase modulation depth of the split beam, if the phase modulation depth of each split beam is the same, then at this time... Available express; For the first The power of the split beam illuminating the detection surface of the photodetector; the 0th split beam is the reference beam.

[0071] Due to the The power of the split beam illuminating the detection surface of the photodetector The square root is proportional to the amplitude of the beam splitter. Therefore, the amplitude of each beam splitter is demodulated and calculated separately. This allows for optimization of each individual polarization error signal to maximize its amplitude, thereby achieving multi-path polarization control and ensuring identical polarization.

[0072] When performing simultaneous polarization and phase control, polarization control should be at least an order of magnitude slower than phase control to ensure that the phase is synchronized during polarization control. Only then can the approximate formula for the polarization error signal be valid.

[0073] In this embodiment, the first detection signal and the second detection signal output by the detection module are acquired. The first detection signal is demodulated to obtain the phase error signal corresponding to each beam. Based on the phase error signal corresponding to each beam, each phase modulator is controlled to adjust the phase of each beam. The second detection signal is then demodulated to obtain the polarization error signal corresponding to each beam. Based on the polarization error signal corresponding to each beam, each polarization controller is controlled to adjust the polarization of each beam.

[0074] The first detection signal is demodulated to obtain the phase error signal corresponding to each beam, which specifically includes: using a coherent radio frequency demodulation method to demodulate the first detection signal to obtain the phase error signal corresponding to each beam, and the calculation formula for the phase error signal is Equation (2).

[0075] The demodulation of the second detection signal to obtain the polarization error signal corresponding to each beam includes: demodulating the second detection signal using a coherent radio frequency demodulation method to obtain the polarization error signal corresponding to each beam, and the calculation formula for the polarization error signal is Equation (3).

[0076] When controlling a phase modulator based on a phase error signal, the phase error signal can be multiplied by a feedback coefficient of appropriate size. If the phase of the split beam is updated, then the first... The phase of the split beam becomes: ,in, For the first Updated phase of the split beam For the first Phase of the split beam For feedback coefficients, For the first The phase error signal corresponding to the split beam, at intervals of time A phase error signal is obtained, which controls the phase modulator to adjust the phase of the beam splitter.

[0077] In this embodiment, each phase modulator is controlled based on the phase error signal corresponding to each beam splitter to adjust the phase of each beam splitter. Specifically, for each beam splitter, the phase modulator corresponding to the beam splitter is controlled based on the phase error signal corresponding to the beam splitter to adjust the phase of the beam splitter to the updated phase.

[0078] The updated phase calculation formula is as follows:

[0079] (4);

[0080] In equation (4), For the first The updated phase of the split beam; For the first Phase of the split beam; For feedback coefficients; For the first Phase error signal corresponding to the split beam.

[0081] The control process of the phase modulator in this embodiment can also be implemented using other algorithms, such as the SPGD algorithm. Since the acquisition of the polarization error signal depends on the multi-jitter method, modulation signals with different modulation angular frequencies must be applied to each beam splitter. Therefore, the multi-phase active control is also best implemented using the multi-jitter method (i.e., the phase error signal solution method and phase control method given in this embodiment). In this case, there is no need to set up additional components to implement multi-phase active control, nor is it necessary to introduce additional algorithms, thus reducing system complexity.

[0082] When controlling a polarization controller based on polarization error signals, the SPGD algorithm can be used to convert the polarization error signals (i.e., the polarization error signals of each beam splitter) into polarization error signals. The algorithm optimizes the output beam to its maximum value, thereby ensuring that the polarization state of the split beams reaches the desired linear polarization direction. The SPGD algorithm contains N independent loops, each controlling the polarization of one of the N split beams. The first loop stores the multi-jitter method. Path polarization error signal As an evaluation function, denoted as , that is to say = When the polarization controller consists of four piezoelectric ceramics (this is the physical model of the polarization controller, composed of four piezoelectric ceramics, equivalent to four waveplates with adjustable phase delay), changing the polarization state of each beam requires adjusting four voltage signals simultaneously. Taking a certain loop of the SPGD algorithm as an example, the execution steps are as follows (the execution time for one step is...). , ).

[0083] (1) Generate a set of random disturbance voltages , These represent the disturbance voltages applied to the four piezoelectric ceramics and the voltage applied to the current control voltage. Perform a positive perturbation to obtain the evaluation function after the positive perturbation. = ( + ).

[0084] (2) Using a set of random disturbance voltages generated in (1), adjust the current control voltage. Perform a negative perturbation to obtain the evaluation function after the negative perturbation. = ( - ).

[0085] (3) Calculate the change in the evaluation function after the disturbance. =( - ) / ( + Update control voltage = + ,in, To update the control voltage, This represents the gain coefficient of the SPGD algorithm. Let V be the variance of a set of random disturbance voltages.

[0086] (4) Repeat (1)-(3) to make the evaluation function continuously approach the maximum value.

[0087] When all evaluation functions reach their maximum values, the polarization direction of the split beam is adjusted to the main polarization direction, and the polarization states of each path are consistent, thus completing polarization control.

[0088] In this embodiment, each polarization controller is controlled based on the polarization error signal corresponding to each beam splitter to adjust the polarization of each beam splitter. Specifically, for each beam splitter, the polarization error signal corresponding to the beam splitter is used as input, and the SPGD algorithm is used to control the polarization controller corresponding to the beam splitter to adjust the polarization of the beam splitter.

[0089] The polarization controller in this embodiment can also be implemented using other algorithms, and the polarization controller does not necessarily have to be equivalent to a structure of four piezoelectric ceramics. However, the control principle is still to optimize the polarization error signal obtained by demodulation using the multi-jitter method to make the signal amplitude the strongest (i.e., the amplitude of the main polarization direction of the split beam is the strongest). Since the multi-jitter method is an active phase control algorithm based on phase modulation and demodulation, it is not directly related to the laser amplitude / polarization. Therefore, no research team has applied the multi-jitter method to the polarization control process. This embodiment innovatively introduces the multi-jitter method into polarization control, which can calculate the polarization error signal of each split beam through a single sampling and detection. Furthermore, polarization control is performed based on the polarization error signal, which can achieve separation of multiple control paths. The control speed does not change with the number of paths, thereby achieving high control speed multi-path active polarization control under low system complexity conditions.

[0090] Based on the above principles, this embodiment simulates a coherent beam combining system with seven beams arranged in a hexagonal pattern, where the initial polarization and phase of the beams are random. The simulation results are as follows: Figure 2 As shown, the photodetector detects the power of the central main lobe of the far-field light spot. Figure 2 In (a), the reference beam has the same optical aperture as all the split beams, and in the near field, it only coincides with the central split beam. Figure 2 In (b), the reference beam is expanded to cover the entire aperture of the split aperture array and coincides with each split beam in the near field. It can be seen that both schemes can achieve polarization phase control and quickly reach maximum intensity (maximum combining efficiency), proving their feasibility in split aperture coherent combining systems.

[0091] This embodiment requires two photodetectors for phase and polarization control, respectively. Through a coherent RF demodulation process using the multi-jitter method, the phase error signal and polarization error signal (i.e., intensity information) of each beam splitter are acquired. These signals are then used as input signals for each phase control loop and polarization control loop, thus expanding the multi-path polarization phase active control technology and broadening its application scope. It can be used in aperture-splitting coherent combining systems. Compared with traditional polarization phase active control technology, it has the advantages of low system complexity and strong scalability, making it suitable for the application requirements of large-scale aperture-splitting coherent combining systems.

[0092] Example 2.

[0093] This embodiment provides a multi-path polarization phase active control method for a multi-aperture coherent combining system, which operates based on the multi-path polarization phase active control system of the multi-aperture coherent combining system described in Embodiment 1. Figure 3 As shown, it includes the following steps.

[0094] S1: Obtain the first and second detection signals output by the detection module.

[0095] S2: Demodulate the first detection signal to obtain the phase error signal corresponding to each beam, and control each phase modulator to adjust the phase of each beam based on the phase error signal corresponding to each beam.

[0096] S3: Demodulate the second detection signal to obtain the polarization error signal corresponding to each beam, and control each polarization controller to adjust the polarization of each beam based on the polarization error signal corresponding to each beam.

[0097] In S2, the first detection signal is demodulated to obtain the phase error signal corresponding to each beam. Specifically, this includes: using a coherent radio frequency demodulation method to demodulate the first detection signal to obtain the phase error signal corresponding to each beam.

[0098] In S3, the second detection signal is demodulated to obtain the polarization error signal corresponding to each beam. Specifically, this includes using a coherent radio frequency demodulation method to demodulate the second detection signal to obtain the polarization error signal corresponding to each beam.

[0099] In S2, the formula for calculating the phase error signal is:

[0100] ;

[0101] in, For the first Phase error signal corresponding to the split beam; The integration time; For the first The modulation angular frequency of the split beam; For a specific moment; for The first detection signal at that moment; is the voltage conversion coefficient of the photodetector; For the first The power of the split beam illuminating the detection surface of the photodetector; It is a first-order Bessel function of the first kind; For the first Phase modulation depth of beam splitter; The number of beams; For the first The power of the split beam illuminating the detection surface of the photodetector; It is a Bessel function of the first kind, order 0; For the first Phase modulation depth of beam splitter; For the first The phase of the split beam in the main polarization direction; For the first The phase of the split beam in the main polarization direction.

[0102] In S3, the formula for calculating the polarization error signal is:

[0103] ;

[0104] in, For the first Polarization error signal corresponding to beam splitting; For the first The power of the split beam illuminating the detection surface of the photodetector; the 0th split beam is the reference beam.

[0105] In S2, each phase modulator is controlled based on the phase error signal corresponding to each beam to adjust the phase of each beam. Specifically, for each beam, the phase modulator corresponding to the beam is controlled based on the phase error signal to adjust the phase of the beam to the updated phase.

[0106] The updated phase calculation formula is as follows:

[0107] ;

[0108] in, For the first The updated phase of the split beam; For the first Phase of the split beam; For feedback coefficients; For the first Phase error signal corresponding to the split beam.

[0109] In S3, each polarization controller is controlled based on the polarization error signal corresponding to each beam split to adjust the polarization of each beam split. Specifically, for each beam split, the polarization error signal corresponding to the beam split is used as input, and the SPGD algorithm is used to control the polarization controller corresponding to the beam split to adjust the polarization of the beam split.

[0110] Example 3.

[0111] In one exemplary embodiment, a computer device is provided, which may be a server or a terminal, and its internal structure diagram may be as follows. Figure 4As shown, this computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and a database. The internal memory provides the environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The database stores data. The I / O interfaces are used for exchanging information between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When the computer program is executed by the processor, it implements a multi-path polarization phase active control method for a multi-aperture coherent synthesis system.

[0112] Those skilled in the art will understand that Figure 4 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0113] In one exemplary embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the multi-path polarization phase active control method of the aperture-splitting coherent synthesis system in Embodiment 2.

[0114] Example 4.

[0115] In one exemplary embodiment, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, implements the multi-path polarization phase active control method of the aperture-splitting coherent synthesis system in Embodiment 2.

[0116] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0117] 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.

[0118] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A multi-path polarization phase active control system for a multi-aperture coherent combining system, characterized in that, include: Detection module and control module; The detection module is used to sample the coherent combined light output from the aperture-splitting coherent combining system to obtain sampled light, and then combine the sampled light and the reference light twice to obtain a first combined light and a second combined light. The first combined light and the second combined light are then detected to obtain a first detection signal and a second detection signal. The reference light is a collimated beam output from the beam splitter in the aperture-splitting coherent combining system. The first combined light is the combined light obtained by combining the sampled light and the reference light, and the second combined light is the combined light obtained by combining the sampled light and the reference light after a 90-degree phase shift. The control module includes a control system, multiple phase modulators and multiple polarization controllers. Each phase modulator and polarization controller corresponds one-to-one with the beam splitter output from the beam splitter other than the reference beam. Each phase modulator applies a modulation signal, and the modulation angular frequency of the modulation signal applied by different phase modulators is different. The control system is used to demodulate the first detection signal to obtain a phase error signal corresponding to each of the beam splitters, and to control each of the phase modulators to adjust the phase of each beam splitter based on the phase error signal corresponding to each of the beam splitters. The phase modulator is controlled once every integration time. When the control time is reached, the phase modulation is completed. Then, the second detection signal is demodulated to obtain a polarization error signal corresponding to each of the beam splitters, and to control each of the polarization controllers to adjust the polarization of each beam splitter based on the polarization error signal corresponding to each of the beam splitters. The polarization controller is controlled once every control time until the polarization control is completed. The control time is an order of magnitude larger than the integration time. Demodulating the first detection signal to obtain the phase error signal corresponding to each beam splitter specifically includes: using a coherent radio frequency demodulation method to demodulate the first detection signal to obtain the phase error signal corresponding to each beam splitter. Demodulating the second detection signal to obtain the polarization error signal corresponding to each beam splitter specifically includes: using a coherent radio frequency demodulation method to demodulate the second detection signal to obtain the polarization error signal corresponding to each beam splitter. The detection module includes a sampling mirror, a synthesizer, a first detector, and a second detector; The first detector includes a first polarizer, a first focusing lens, and a first photodetector. The first polarizer is used to convert the first composite light into first composite polarized light. The first focusing lens is used to focus the first composite polarized light to obtain first composite focused light. The first photodetector is used to perform photoelectric conversion on the first composite focused light to obtain a first detection signal. The second detector includes a second polarizer, a second focusing lens, and a second photodetector. The second polarizer is used to convert the second composite light into a second composite polarized light. The second focusing lens is used to focus the second composite polarized light to obtain a second composite focused light. The second photodetector is used to perform photoelectric conversion on the second composite focused light to obtain a second detection signal.

2. The multi-path polarization phase active control system of the aperture-splitting coherent combining system according to claim 1, characterized in that, The sampling mirror is used to sample the coherent combined light output by the aperture-splitting coherent combining system to obtain sampled light; the combiner is used to combine the sampled light and the reference light twice to obtain a first combined light and a second combined light; the first detector is used to detect the first combined light to obtain a first detection signal; The second detector is used to detect the second synthesized light to obtain a second detection signal.

3. The multi-path polarization phase active control system of the aperture-splitting coherent combining system according to claim 2, characterized in that, The synthesizer is a 90° optical mixer.

4. The multi-path polarization phase active control system of the aperture-splitting coherent combining system according to claim 1, characterized in that, The aperture-splitting coherent combining system includes: a laser module and a beam combining module; The laser module includes a seed laser, a first laser amplifier, a beam splitter, multiple second laser amplifiers, multiple first collimators, and a second collimator. The seed laser emits a seed laser beam. The first laser amplifier amplifies the seed laser beam to obtain an amplified laser beam. The beam splitter splits the amplified laser beam into multiple beams and an output beam. The second laser amplifiers and the first collimators correspond one-to-one with the beams. The second laser amplifier amplifies the beams to obtain amplified beams. The first collimator collimates the amplified beams to obtain collimated beams. The second collimator collimates the output beam to obtain the reference beam. The beam combining module is used to coherently combine all the collimated and split beams.

5. The multi-path polarization phase active control system of the aperture-splitting coherent combining system according to claim 4, characterized in that, The phase modulator and the polarization controller are located between the beam splitter and the second laser amplifier. The phase modulator is used to modulate the phase of the split beam to obtain phase-modulated split beam. The polarization controller is used to control the polarization of the phase-modulated split beam to obtain polarization-controlled split beam. All the polarization-controlled split beams are amplified by the second laser amplifier and collimated by the first collimator, and then combined by the beam combining module to form the coherent combined beam.

6. A method for active multi-path polarization phase control of a multi-aperture coherent combining system, operating based on the active multi-path polarization phase control system of the multi-aperture coherent combining system according to any one of claims 1-5, characterized in that, include: Acquire the first and second detection signals output by the detection module; The first detection signal is demodulated to obtain the phase error signal corresponding to each beam, and each phase modulator is controlled based on the phase error signal corresponding to each beam to adjust the phase of each beam. The phase modulator is controlled once every integration time. When the control time is reached, the phase modulation is completed. The second detection signal is then demodulated to obtain the polarization error signal corresponding to each beam. Based on the polarization error signal corresponding to each beam, each polarization controller is controlled to adjust the polarization of each beam. The polarization controller is controlled once every control time until the polarization control is completed. The control time is an order of magnitude larger than the integration time. Demodulating the first detection signal to obtain the phase error signal corresponding to each beam splitter specifically includes: using a coherent radio frequency demodulation method to demodulate the first detection signal to obtain the phase error signal corresponding to each beam splitter. Demodulating the second detection signal to obtain the polarization error signal corresponding to each beam split specifically includes: using a coherent radio frequency demodulation method to demodulate the second detection signal to obtain the polarization error signal corresponding to each beam split.

7. The method for active control of multi-path polarization phase in a coherent combining system with varying apertures according to claim 6, characterized in that, The formula for calculating the phase error signal is: ； in, For the first Phase error signal corresponding to the split beam; The integration time; For the first The modulation angular frequency of the split beam; For a specific moment; for The first detection signal at that moment; is the voltage conversion coefficient of the photodetector; For the first The power of the split beam illuminating the detection surface of the photodetector; It is a first-order Bessel function of the first kind; For the first Phase modulation depth of beam splitter; The number of beams; For the first The power of the split beam illuminating the detection surface of the photodetector; It is a Bessel function of the first kind, order 0; For the first Phase modulation depth of beam splitter; For the first The phase of the split beam in the main polarization direction; For the first The phase of the split beam in the main polarization direction; The formula for calculating the polarization error signal is as follows: ； in, For the first Polarization error signal corresponding to beam splitting; For the first The power of the split beam illuminating the detection surface of the photodetector; the 0th split beam is the reference beam.

8. The method for active control of multi-path polarization phase in a coherent combining system with varying apertures according to claim 6, characterized in that, Based on the phase error signal corresponding to each beam, each phase modulator is controlled to adjust the phase of each beam. Specifically, for each beam, the phase modulator corresponding to the beam is controlled to adjust the phase of the beam to the updated phase based on the phase error signal corresponding to the beam. The formula for calculating the updated phase is: ； in, For the first Updated phase of the split beam; For the first Phase of the split beam; For feedback coefficients; For the first Phase error signal corresponding to the split beam.

9. The method for active control of multi-path polarization phase in a coherent combining system with varying apertures according to claim 6, characterized in that, Based on the polarization error signal corresponding to each beam, the polarization controllers are controlled to adjust the polarization of each beam. Specifically, for each beam, the polarization error signal corresponding to the beam is used as input, and the SPGD algorithm is used to control the polarization controller corresponding to the beam to adjust the polarization of the beam.

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