CN114628979A - Laser coherent array phase calibration and control method - Google Patents

Abstract

The invention provides a laser coherent array phase calibration and regulation method, which is used for building a laser coherent array and completing system phase error calibration through a coherent synthesis technology, so that a new system error is not introduced in the calibration process, and the calibration precision is high. In addition, the polarization regulation of each path of laser by each half-wave plate is directly regulated, and the radial polarization distribution, the annular polarization distribution, the spiral polarization distribution and the like of the array laser can be formed by independently setting the polarization direction of each path of laser. The invention can realize the flexible regulation and control of the phase and polarization of each path of laser in the high-power laser array, and has simple phase and polarization calibration process and easy realization of phase control.

Description

Laser coherent array phase calibration and control method

technical field

The invention relates to the technical field of laser light field regulation, in particular to a laser array phase and polarization regulation method.

Background technique

Laser arrays can be widely used in fields such as laser communication, lidar and directed energy technology. The laser array based on Master Oscillator Power Amplifier (English name is Master Oscillator Power Amplifier, MOPA for short) can realize the coherent synthesis of multiple lasers, and maintain the beam quality of the array laser while increasing the total power. If the piston phase of each laser can be flexibly regulated by optical field regulation, array beams with special transmission characteristics such as vortex beams can also be obtained.

In order to realize the phase detection and regulation of each laser, the method of interference fringe detection can be used to calibrate the phase of each laser. However, the above methods are difficult to achieve flexible and simple regulation of the phase and polarization of each laser in a high-power laser array.

SUMMARY OF THE INVENTION

The invention provides a method for adjusting the phase and polarization of a laser array, which can realize the flexible adjustment of the phase and polarization of each laser in a high-power laser array, and the phase and polarization calibration process is simple and the phase control is easy to realize.

For achieving the above object, the technical scheme adopted in the present invention is:

On the one hand, the present invention provides a laser coherent array phase calibration method, including:

Build a laser coherent array: In the laser coherent array, N beams of sub-lasers are input to the corresponding first beam splitter after passing through the phase modulator, laser amplifier, and laser collimator respectively, and most of the laser power is passed through the first beam splitter. The first output optical path of the spectroscope is output, and the remaining small part of the laser power is output through the second output optical path of the first spectroscope; the laser output from the first output optical path of each first spectroscope is transmitted to the first laser through the half-wave plate A beam combiner, the first laser beam combiner combines the output array beams, wherein the half-wave plate is used to change the polarization direction of each laser; the laser output from the second output optical path of each first beam splitter is modulated by the spatial light phase The second laser beam combiner is transmitted to the second laser beam combiner, and the second phase controller is connected to each spatial optical phase modulator; the array beam combined and output by the second laser beam combiner passes through the first lens and the first small hole to reach the first a photodetector, the first photodetector is connected to the first phase controller, and is used to convert the detected optical signal into an electrical signal and transmit it to the first phase controller, and the first phase controller is connected to each phase modulator;

A second beam splitter is set on the output optical path of the first laser beam combiner. The second beam splitter collects a small part of the array beam to the second lens and passes through the second small hole to reach the second photodetector. The second photodetector The device is connected to the second phase controller, and is used to convert the detected optical signal into an electrical signal and transmit it to the second phase controller;

Calibrate the phase difference between the array beam combined output by the first laser beam combiner and the array beam combined output by the second laser beam combiner: first turn on the first phase controller, and load the operation on the first phase controller The phase control algorithm based on the phase control algorithm changes the voltage value output to each phase modulator until the power in the barrel detected by the first photodetector maintains the maximum value; then the second phase controller is turned on to run the The phase control algorithm changes the voltage value output to each spatial optical phase modulator until the power in the barrel detected by the second photodetector reaches the maximum value, and records when the power in the barrel detected by the second photodetector reaches the maximum value , the voltage value V _i output to each spatial optical phase modulator, i=1, 2, . . . , N, so far the calibration is completed.

After the phase calibration of the laser coherent array is completed by using the above method, a method for adjusting the phase of the laser coherent array is provided, including:

Remove the second beam splitter, the second lens, the second aperture and the second photodetector;

为从第一激光合束器输出阵列光束中第i路子激光的相位，V_π为空间光相位调制器的半波电压。First turn on the first phase controller, run the phase control algorithm loaded on the first phase controller, and change the voltage value output to each phase modulator until the power in the barrel detected by the first photodetector maintains the maximum value; then Turn on the second phase controller and directly output the voltage value to the i-th spatial optical phase modulator

is the phase of the i-th sub-laser in the output array beam from the first laser beam combiner, and V _π is the half-wave voltage of the spatial optical phase modulator.

In the present invention, the implementation manner of the N-beam sub-laser in the present invention is not limited. Preferably, the laser coherent array includes a seed laser and a laser beam splitter, the seed laser is connected to the laser beam splitter, and the seed laser output from the seed laser is equally divided into N beams of sub-lasers, N≥2.

The invention builds a laser coherent array, completes the system phase error calibration through the coherent synthesis technology, does not introduce new system errors in the calibration process, and has high calibration accuracy. The first phase controller is a high-speed phase controller, which uses a mature phase control algorithm to achieve phase locking of each laser. In the normal phase control process after completing the phase calibration of the laser coherent array, the second phase controller directly outputs the voltage value to realize the phase control of each laser.

In addition, the present invention can realize the polarization regulation of each laser by directly adjusting each half-wave plate, and by separately setting the polarization direction of each laser, the array laser can form radial polarization distribution, annular polarization distribution, helical polarization distribution, and the like.

The invention can realize the flexible regulation of the phase and polarization of each laser in the high-power laser array, the phase and polarization calibration process is simple, and the phase control is easy to realize.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that are required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can also be obtained according to the structures shown in these drawings without creative efforts. picture.

1 is a schematic structural diagram of Embodiment 1 of the present invention;

2 is a schematic structural diagram of Embodiment 2 of the present invention;

Labels in the figure:

1. Seed laser; 2. Laser beam splitter; 3. Phase modulator; 4. Laser amplifier; 5. Laser collimator; 6. First beam splitter; 7. Half-wave plate; 8. First laser beam combiner 9. Spatial light phase modulator; 10. Second laser beam combiner; 11. First lens; 12. First aperture; 13. First photodetector; 14. First phase controller; 15. The second phase controller; 16, the second beam splitter; 17, the second lens; 18, the second aperture; 19, the second photodetector.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention more clearly understood, the following will clearly illustrate the spirit of the disclosed contents of the present invention with the accompanying drawings and detailed description. Afterwards, changes and modifications can be made by the technology taught by the content of the present invention, without departing from the spirit and scope of the content of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

1, a laser coherent array provided in an embodiment includes a seed laser 1, a laser beam splitter 2, N phase modulators 3, N laser amplifiers 4, N laser collimators 5, N first Beam splitter 6, N half-wave plates 7, first laser beam combiner 8, N spatial optical phase modulators 9, second laser beam combiner 10, first lens 11, first aperture 12, first photoelectric The detector 13 , the first phase controller 14 and the second phase controller 15 . The first phase controller 14 is a high-speed phase controller. Compared with the first phase controller 14 , the second phase controller 15 adopts a low-speed phase controller. N is an integer and N≥2.

The seed laser 1 is connected to the input end of the laser beam splitter 2 , and the seed laser output from the seed laser 1 is equally divided into N beams of sub-lasers by the laser beam splitter 2 .

The laser beam splitter 2 has N output ends, and the ith output end is connected to the ith phase modulator 3 by the optical path, i=1, . . . , N.

The phase modulator 3 is used to change the piston phase of each sub-laser. The ith phase modulator 3 is optically connected to the ith laser amplifier 4, i=1, 2, . . . , N.

The laser amplifier 4 is used to amplify the power of the sub-laser. The ith laser amplifier 4 is optically connected to the ith laser collimator 5, i=1, 2, . . . , N.

The laser collimator 5 is used for collimating the laser light output by the laser amplifier 4 , and the laser light output by the laser collimator 5 is linearly polarized laser with the same polarization direction. The outgoing laser light of the i-th laser collimator 5 is incident on the i-th first beam splitter 6, i=1, 2, . . . , N.

The i-th first beam splitter 6 is used to split the outgoing laser energy of the i-th laser collimator 5 , wherein >99% of the laser energy is output through the first output optical path of the i-th first beam splitter 6 , and the rest <1% laser energy is output through the second output optical path of the i-th first beam splitter 6 . A half-wave plate 7 is provided on the first output optical path of each first beam splitter 6 , and a spatial light phase modulator 9 is provided on the second output optical path of each first beam splitter 6 . The second phase controller 15 is connected to each of the spatial light phase modulators 9 .

The half-wave plate 7 is used to change the polarization direction of each sub-laser, and change the polarization direction of each sub-laser by an angle θ _i , i=1, 2, . . . , N. Each sub-laser outputted by each half-wave plate 7 is incident on the first laser beam combiner 8, and the first laser beam combiner 8 combines the beams to output an array beam. The first laser beam combiner 8 can reduce the spacing between the incident sub-lasers to form a closely arranged array of laser outputs.

The spatial light phase modulator 9 is used to change the piston phase of each laser. The sub-lasers output by the spatial optical phase modulators 9 are incident on the second laser beam combiner 10, and the second laser beam combiner 10 combines the beams to output an array beam. The second laser beam combiner 10 can also reduce the spacing between the incident sub-lasers to form a closely arranged array of laser outputs.

The array beam combined and output by the second laser beam combiner 10 reaches the first photodetector 13 after passing through the first lens 11 and the first small hole 12, and the first photodetector 13 is connected to the first phase controller 14. It is used to convert the detected optical signals into electrical signals and transmit them to each of the first phase controllers 14 , and the first phase controllers 14 are connected to each of the phase modulators 3 .

After the laser coherent array shown in FIG. 1 is built, the present invention provides a calibration method for the laser coherent array, including:

Build a calibration device for laser coherent arrays,

As shown in FIG. 2 , a second beam splitter 16 is arranged on the output optical path of the first laser beam combiner 8 . The second beam splitter 16 collects a small part of the array beam to the second lens 17 and passes through the second small hole 18 Reaching the second photodetector 19 , the second photodetector 19 is connected to the second phase controller 15 for converting the detected optical signal into an electrical signal and transmitting it to the second phase controller 15 .

Calibrate the phase difference between the array beam combined and output by the first laser beam combiner 8 and the array beam combined and output by the second laser beam combiner 10: first turn on the first phase controller 14, and run the load at the first phase The phase control algorithm on the controller 14 changes the voltage value output to each phase modulator 3 until the power in the barrel detected by the first photodetector 13 maintains the maximum value; then the second phase controller 15 is turned on, and the operation is loaded at The phase control algorithm on the second phase controller 15 changes the voltage value output to each spatial optical phase modulator 9 until the power in the barrel detected by the second photodetector 19 reaches the maximum value, and records the second photodetector 19 When the detected power in the barrel reaches the maximum value, the voltage values V _i output to each spatial optical phase modulator 9 , i=1, 2, . . . , N, and the calibration is completed.

The first lens 11 , the first small hole 12 and the first photodetector 13 are used to detect the power in the barrel of the far-field spot of the incident array beam. The same second lens 17, second aperture 18 and second photodetector are used 19 to detect the power in the barrel of the far-field spot of the incoming array beam.

The first phase controller 14 is used to correct the phase noise of each laser. Its input port is connected to the first photodetector 13, and the i-th output port is connected to the i-th phase modulator 3, i=1, 2, . . . , N. The first phase controller 14 is a high-speed phase controller, which is preloaded with a phase control algorithm. By running the phase control algorithm, the voltage value output to each phase modulator 3 is changed, so that the first photodetector 13 detects The power in the barrel is kept at the maximum value.

为从第一激光合束器8输出的第i路子激光的相位，V_π为空间光相位调制器9的半波电压。The second phase controller 15 is used for calibrating the phase difference between the array beams output by the first laser beam combiner 8 and the second laser beam combiner 10, and for the array beam output by the first laser beam combiner 8. The phase of the beam is regulated. The i-th output port of the second phase controller 15 is connected to the i-th spatial optical phase modulator 9 . In the process of calibrating the laser coherent array, its input port is connected to the second photodetector 19, and by running the phase control algorithm loaded on it, the power in the barrel detected by the second photodetector 19 reaches the maximum value, and records The voltage value V _i output to the i-th spatial light phase modulator 9 . In the normal working stage of the laser coherent array after the calibration of the laser coherent array is completed, the second phase controller 15 will directly output the voltage value to the i-th spatial optical phase modulator 9

is the phase of the i-th sub-laser output from the first laser beam combiner 8 , and V _π is the half-wave voltage of the spatial optical phase modulator 9 .

Specifically, an embodiment provides a method for adjusting the phase of a laser coherent array, including:

Build the phase calibration system of the laser coherent array as shown in Figure 2, and use the laser coherent array phase calibration method provided in the above embodiment to complete the phase calibration of the laser coherent array, remove the second beam splitter 16, the second lens 17, the second Small hole 18 and second photodetector 19;

为从第一激光合束器8输出阵列光束中第i路子激光的相位，V_π为空间光相位调制器9的半波电压。First turn on the first phase controller 14, run the phase control algorithm loaded on the first phase controller 14, and change the voltage value output to each phase modulator 3 until the power in the barrel detected by the first photodetector 13 remains The maximum value; then turn on the second phase controller 15, and directly output the voltage value to the i-th spatial optical phase modulator 9

In order to output the phase of the i-th sub-laser in the array beam from the first laser beam combiner 8 , V _π is the half-wave voltage of the spatial optical phase modulator 9 .

The phase control algorithm described in the present invention is not limited, and may be a parallel gradient random descent algorithm, a single-jitter algorithm or a multi-jitter algorithm.

In the present invention, the polarization direction of each sub-laser is individually adjusted by the half-wave plate corresponding to each sub-laser, so that the first laser beam combiner combines beams to output array beams with different polarization distributions. The specific polarization distribution methods are not limited, including but not limited to through The half-wave plate corresponding to each sub-laser individually adjusts the polarization direction of each sub-laser, so that the first laser beam combiner combines beams to output an array beam with radial polarization distribution, annular polarization distribution or helical polarization distribution.

The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, all It is considered to be the range described in this specification.

The above-mentioned embodiments only represent several embodiments of the present application, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the scope of protection of the patent of the present application shall be subject to the appended claims.

Claims (10)

1. The laser coherent array phase calibration method is characterized by comprising the following steps:

building a laser coherent array, wherein N beams of sub-lasers respectively pass through a phase modulator, a laser amplifier and a laser collimator and then are input into corresponding first beam splitters for splitting, wherein most of the power lasers are output through a first output light path of the first beam splitters, and the rest of the power lasers are output through a second output light path of the first beam splitters; the laser output by the first output light path of each first spectroscope is transmitted to a first laser beam combiner through a half-wave plate, the first laser beam combiner combines the laser beams to output an array beam, and the half-wave plate is used for changing the polarization direction of each path of laser; the laser output by the second output light path of each first spectroscope is transmitted to a second laser beam combiner through a spatial light phase modulator, and a second phase controller is connected with each spatial light phase modulator; the array light beam output by the second laser beam combiner passes through the first lens and the first small hole and then reaches the first photoelectric detector, the first photoelectric detector is connected with the first phase controller and used for converting the detected optical signal into an electric signal and transmitting the electric signal to the first phase controller, and the first phase controller is connected with each phase modulator;

a second beam splitter is arranged on an output light path of the first laser beam combiner, a small part of array light beams are collected by the second beam splitter to a second lens and reach a second photoelectric detector after passing through a second small hole, and the second photoelectric detector is connected with a second phase controller and is used for converting detected optical signals into electric signals and transmitting the electric signals to the second phase controller;

calibrating the phase difference between the array beams output by the first laser beam combiner and the array beams output by the second laser beam combiner: first, the first phase controller is started, the phase control algorithm loaded on the first phase controller is operated, and the electricity output to each phase modulator is changedThe pressure value is kept until the power in the barrel detected by the first photoelectric detector keeps the maximum value; then, the second phase controller is started, a phase control algorithm loaded on the second phase controller is operated, the voltage value output to each space optical phase modulator is changed until the power in the barrel detected by the second photoelectric detector reaches the maximum value, and when the power in the barrel detected by the second photoelectric detector reaches the maximum value, the voltage value V output to each space optical phase modulator is recorded_iI is 1,2, …, N, to this point the calibration is completed.

2. The method for calibrating the phase of the laser coherent array according to claim 1, wherein the laser coherent array comprises a seed laser and a laser beam splitter, the seed laser is connected with the laser beam splitter, and the seed laser output by the seed laser is equally divided into N beams of sub-laser, wherein N is larger than or equal to 2.

3. The method for calibrating the phase of a laser coherent array according to claim 1, wherein the phase control algorithm is a parallel gradient random descent algorithm, a single-jitter algorithm or a multi-jitter algorithm.

4. The method for calibrating the phase of the laser coherent array according to claim 1, wherein the polarization direction of each path of sub-laser is independently adjusted through a half-wave plate corresponding to each path of sub-laser, so that the first laser beam combiner combines beams to output array beams with different polarization distributions.

5. The method for calibrating the phase of the laser coherent array according to claim 4, wherein the polarization direction of each path of sub-laser is independently adjusted through a half-wave plate corresponding to each path of sub-laser, so that the first laser beam combiner combines beams to output array beams with radial polarization distribution or annular polarization distribution or spiral polarization distribution.

6. A laser coherent array phase regulation method is characterized by comprising the following steps:

after completing the phase calibration of the laser coherent array by the method of claim 1, removing the second beam splitter, the second lens, the second aperture and the second photodetector;

starting a first phase controller, operating a phase control algorithm loaded on the first phase controller, and changing voltage values output to each phase modulator until the power in the barrel detected by a first photoelectric detector keeps the maximum value; then the second phase controller is started to directly output the voltage value to the ith space optical phase modulator

For outputting the phase, V, of the ith sub-laser in the array beam from the first laser beam combiner_πIs the half-wave voltage of the spatial optical phase modulator.

7. The method for calibrating the phase of the laser coherent array according to claim 6, wherein the laser coherent array comprises a seed laser and a laser beam splitter, the seed laser is connected with the laser beam splitter, and the seed laser output by the seed laser is equally divided into N beams of sub-laser, wherein N is larger than or equal to 2.

8. The method for calibrating the phase of the laser coherent array according to claim 6 or 7, wherein the phase control algorithm is a parallel gradient random descent algorithm, a single-jitter algorithm or a multi-jitter algorithm.

9. The method for calibrating the phase of the coherent laser array of claim 8, wherein the polarization direction of each path of sub-laser is individually adjusted by the half-wave plate corresponding to each path of sub-laser, so that the first laser beam combiner combines the beams to output the array beams with different polarization distributions.

10. The method for calibrating the phase of a laser coherent array according to claim 8, wherein the polarization direction of each sub-laser is individually adjusted by the half-wave plate corresponding to each sub-laser, so that the first laser beam combiner combines beams to output an array beam with radial polarization distribution or circular polarization distribution or spiral polarization distribution.

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