Multi-wavelength co-directional regulation and control method and system based on liquid crystal optical phased array

Abstract

The invention relates to the technical field of laser communication, and particularly provides a multi-wavelength co-directional regulation and control method and system based on a liquid crystal optical phased array, and the method comprises the steps: carrying out the coaxial beam combination of multiple paths of signal light and beacon light with different working wavelengths through a light beam combiner, and carrying out the adjustment of the coaxial light beams through a polarizing film and a collimation and beam expansion system, determining an ideal phase value of each pixel point on the liquid crystal optical phased array according to the target deflection angles of the signal light and the beacon light, and calculating an error between target phase distribution and actual phase distribution of the signal light and the beacon light based on a phase optimization principle of complex amplitude least square error minimization; the optimal voltage gray value of each pixel point is obtained by minimizing the error value, a voltage gray-scale map is generated, and phase modulation is performed based on the voltage gray-scale map, so that the signal light and the beacon light realize the same target deflection angle. According to the invention, the problem of dispersion caused by different deflection angles of multi-wavelength light beams due to the limitation of a grating equation in the traditional LCOPA is solved.

Description

Technical Field

[0001] The present invention belongs to the field of laser communication technology, and in particular relates to a multi-wavelength co-directional control method and system based on a liquid crystal optical phased array. Background Art

[0002] As a new generation of efficient communication technology, laser communication is widely used in ground, underwater and space communication systems with its advantages of high bandwidth, low latency and high confidentiality. Among them, the coordinated regulation of light beams of different wavelengths is the key technology to achieve efficient and reliable communication links. Signal light and beacon light often exist at the same time, and they each have different functions: the longer wavelength signal light becomes the core carrier of communication due to its low loss and strong anti-interference ability, and is used for high data rate transmission; the shorter wavelength beacon light is mainly used for path calibration and real-time tracking to improve the accuracy and stability of the communication link. If the co-directional regulation of any two wavelength beams can be achieved, it can not only effectively reduce the pointing error between the beams and avoid link interruption, but also simplify the optical system structure and improve the system's integration and dynamic response performance. Therefore, the co-directional regulation of multi-wavelength beams has significant advantages and is an important research direction in the application of multi-wavelength laser communication.

[0003] In the prior art, the control of multi-wavelength beams is mainly divided into two control methods: mechanical and non-mechanical. Mechanical control relies on adjusting the physical position of optical devices to adjust the direction of the beam. Although the technology is mature, it is large in size, slow in response, and high in power consumption, making it difficult to meet the real-time requirements of modern communication systems. Liquid Crystal Optical Phased Array (LCOPA), as a non-mechanical beam control device, can achieve fast and high-precision beam control with its dynamic phase control capability, demonstrating its application potential in space laser communications. However, LCOPA is still limited by the grating equation in multi-wavelength control, and the deflection angles of beams of different wavelengths are difficult to achieve synchronous control, which in turn leads to increased link errors and increased bit error rates, resulting in limited system performance in practical applications. Therefore, how to break through the constraints of traditional grating equations and achieve co-directional control of signal light and beacon light has become a key problem in the current research on multi-wavelength beam control. Summary of the invention

[0004] In view of this, the present invention aims to provide a multi-wavelength co-directional regulation method and system based on a liquid crystal optical phased array. By constructing a phase optimization principle centered on minimizing the least square error of complex amplitude, the phase modulation of each pixel in the LCOPA is optimized, effectively solving the dispersion problem caused by different deflection angles of multi-wavelength light beams due to the grating equation limitation in traditional LCOPA, achieving high-precision co-directional regulation of multi-wavelength light beams, significantly reducing optical aberration and scattering phenomena caused by wavelength differences, and improving the regulation efficiency of multi-wavelength light beams.

[0005] To achieve the above object, the technical solution of the present invention is realized as follows: On the one hand, the present invention provides a multi-wavelength co-directional regulation method based on a liquid crystal optical phased array, including: Signal lights and beacon lights of different wavelengths are coaxially combined and then incident on the liquid crystal optical phased array; According to the target deflection angles of the signal lights and beacon lights, establish the target phase distributions of the signal lights and beacon lights, and determine the ideal phase values of each pixel point on the liquid crystal optical phased array; Based on the phase optimization principle of minimizing the least square error of complex amplitude, calculate the error between the target phase distributions and the actual phase distributions of the signal lights and beacon lights, calculate the optimal voltage gray value of each pixel point by minimizing this error, and generate a voltage gray map; The liquid crystal optical phased array regulates the alignment direction of liquid crystal molecules according to the voltage gray map, generates a phase modulation distribution with spatially linear variation, and enables the signal lights and beacon lights to achieve the same target deflection angle.

[0006] Preferably, a beam combiner is used to coaxially combine signal lights and beacon lights of different wavelengths.

[0007] Preferably, the signal light is a Gaussian beam with a wavelength of 1550 nm, and the beacon light is a Gaussian beam with a wavelength of 808 nm.

[0008] Preferably, after the signal lights and beacon lights are coaxially combined, it further includes adjusting the polarization direction of the coaxial beam so that the polarization direction of the coaxial beam is the same as the regulation direction of the liquid crystal optical phased array.

[0009] Preferably, after the signal lights and beacon lights are coaxially combined, it further includes adjusting the diameter of the coaxial beam so that the diameter of the coaxial beam matches the optical aperture of the liquid crystal optical phased array.

[0010] Preferably, a collimating and beam expanding system is used to adjust the diameter of the coaxial beam of the signal lights and beacon lights. The collimating and beam expanding system includes a first lens and a second lens; The first lens has a negative optical power and is used to expand the divergence angle of the coaxial beam; the second lens has a positive optical power and is used to correct the divergence angle of the coaxial beam.

[0011] On the other hand, the present invention provides a multi-wavelength co-directional regulation system based on a liquid crystal optical phased array, comprising: A first laser for providing a first-wavelength signal light; A second laser for providing a second-wavelength beacon light; A beam combiner for coaxially combining the signal light and the beacon light; A polarizer for adjusting the polarization direction of the coaxial beam of the signal light and the beacon light; A collimating and beam expanding system for adjusting the diameter of the coaxial beam; A liquid crystal optical phased array, which regulates the signal light and the beacon light by using a multi-wavelength co-directional regulation method based on the liquid crystal optical phased array.

[0012] Preferably, it further comprises: An autocollimator for far-field focusing of the signal light and the beacon light regulated by the liquid crystal optical phased array; A camera for imaging the signal light and the beacon light focused by the autocollimator, and analyzing the regulation consistency and pointing accuracy of the signal light and the beacon light by obtaining the spot images.

[0013] Compared with the prior art, the present invention can achieve the following beneficial effects: By the principle of minimizing the complex amplitude least square error, the present invention realizes the high-precision synchronous co-directional deflection of different-wavelength light beams in the same direction, can effectively reduce the pointing error between the light beams, avoid link interruption, and thus improve the stability and reliability of the communication link. Through the optimized design of minimizing the complex amplitude least square error, it is possible to independently adjust the phase of each pixel point on the liquid crystal optical phased array, so that different-wavelength light beams can achieve the same deflection angle under the same voltage grayscale map. This regulation method can flexibly adjust the phase distribution of the light beam, solves the problem of asynchronous deflection angles of multi-wavelength light beams caused by the grating equation, and significantly improves the precision of light beam regulation.

[0014] By minimizing the error between the target phase distribution and the actual phase distribution, the present invention ensures that the phase modulation of the two-wavelength light beams is as close as possible to the target phase distribution. By reducing the optical aberration and scattering phenomena caused by wavelength differences, it not only improves the regulation efficiency of multi-wavelength light beams, but also can reduce the bit error rate in the communication link, improve the communication quality, and meet the high-precision information transmission requirements in multi-wavelength laser communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 is an optical path diagram for multi-wavelength co-directional regulation based on a liquid crystal optical phased array according to an embodiment of the present invention; Figure 2 is a multi-wavelength two-dimensional voltage look-up table according to an embodiment of the present invention; Figure 3 is a two-dimensional deflection 3mrad voltage grayscale map loaded with LCOPA according to an embodiment of the present invention; Figure 4 is a comparison diagram of the far-field light intensity distribution of deflected 3mrad by different regulation methods according to an embodiment of the present invention; Figure 5 is a comparison diagram of the deflection pointing error curves at different angles according to an embodiment of the present invention; Figure 6 is a comparison diagram of the regulation effects of the single-wavelength mode and the multi-wavelength mode of the multi-wavelength co-directional regulation method according to an embodiment of the present invention.

[0016] The reference numerals therein include: The first laser 1, the second laser 2, the beam combiner 3, the polarizer 4, the first lens 5, the second lens 6, the liquid crystal optical phased array 7, the autocollimator 8, and the camera 9. Specific Embodiments

[0017] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. Similar elements in different embodiments are labeled with related similar reference numerals. In the following embodiments, many details are described to enable a better understanding of the present invention. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, and methods. In some cases, some operations related to the present invention are not shown or described in the specification to avoid the core part of the present invention being overwhelmed by excessive description. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0018] It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other to form various implementation manners. At the same time, the steps or actions in the method description can also be adjusted in sequence or regulated in a manner obvious to those skilled in the art. Therefore, the various sequences in the specification and drawings are only for clearly describing a certain embodiment and do not mean that they are necessary sequences, unless it is stated that a certain sequence must be followed.

[0019] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0020] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0021] The present invention will be described in detail below with reference to the drawings and in combination with embodiments.

[0022] Please refer to Figure 1, in an embodiment of the present invention, a multi-wavelength co-directional regulation system based on a liquid crystal optical phased array is provided. Specifically, taking the co-directional regulation of two wavelengths commonly used in laser communication as an example, among them, the wavelength of one signal light beam is 1550 nm, and the wavelength of the other beacon light beam is 808 nm. Specifically, the regulation system is sequentially provided with: a first laser 1, a second laser 2, a beam combiner 3, a polarizer 4, a first lens 5, a second lens 6, a liquid crystal optical phased array 7, an autocollimator 8, and a camera 9 along the light beam emission direction. Among them, the first laser 1 is used to provide the signal light, and the second laser 2 is used to provide the beacon light. Specifically, taking the laser beams with wavelengths of 1550 nm and 808 nm commonly used in laser communication as the signal light and the beacon light respectively as an example, the signal light emitted by the first laser 1 is a Gaussian beam with a wavelength of 1550 nm, the power of this beam is 10 mW, and the beam quality M² < 1.2. The signal light emitted by the second laser 2 is a Gaussian beam with a wavelength of 808 nm, the power of this beam is 15 mW, and the beam quality M² < 1.3. The light emission directions of the first laser 1 and the second laser 2 are perpendicular to each other, and the emitted signal light and beacon light are spatially superimposed at the position of the beam combiner 3 to form a coaxial beam containing two wavelengths, laying a foundation for subsequent co-directional regulation. The beam combiner 3 has a high transmittance characteristic for the incident 1550 nm wavelength signal light, and its transmittance for the 1550 nm wavelength signal light can reach more than 95%. And it has a high reflectance characteristic for the incident 808 nm wavelength beacon light, and its reflectance for the 808 nm wavelength signal light can also reach more than 95%. Therefore, under the action of the beam combiner 3, the signal light and the beacon light are coaxially combined in space, the light spots overlap, and the preliminary spatial unity is achieved, and the output forms a coaxial beam containing two wavelengths.

[0023] After beam combination, in order to make the coaxial beam match the subsequent liquid crystal optical phased array 7, it is also necessary to regulate the polarization direction and the beam diameter of the coaxial beam. First, a polarizer 4 is set at the rear end of the output optical path of the beam combiner 3 to adjust the polarization direction of the coaxial beam through the polarizer 4 to make it consistent with the regulation direction of the liquid crystal optical phased array 7, so as to ensure that the beam can perform phase regulation efficiently. In the embodiment of the present invention, the polarizer 4 needs to adopt an element with wide-band adaptability, and at least has a transmittance of more than 98% for light beams in the wavelength range of 400–1600 nm. After being processed by the polarizer 4, the polarization direction of the coaxial beam meets the polarization direction requirements of the liquid crystal optical phased array 7 for the incident beam.

[0024] After the polarization direction is adjusted, the coaxial beam continues to be transmitted into the collimating and beam expanding system composed of the first lens 5 and the second lens 6. The collimating and beam expanding system is used to change the divergence angle of the coaxial beam and the diameter of the coaxial beam on the one hand, and can collimate the coaxial beam on the other hand. In the embodiment of the present invention, the first lens 5 in the collimating and beam expanding system is a concave lens with a negative optical power; the second lens 6 is a convex lens with a positive optical power. The first lens 5 is a concave lens, and its main function is to expand the diameter of the coaxial beam. Through the diverging action of the negative focal length, the divergence angle of the coaxial beam is increased, and the beam density is reduced. Specifically, the concave lens diverges the incident beam, increasing the divergence angle of the beam, thereby preparing for the subsequent beam expansion by the convex lens. The second lens 6 is a convex lens, and its main function is to cooperate with the concave lens to complete the collimation and beam expansion of the beam. Specifically, the convex lens focuses and expands the beam that has been diverged by the concave lens, expanding the beam diameter to the size suitable for the working area of the liquid crystal optical phased array 7, and at the same time correcting the divergence angle of the beam. Through the cooperation of the concave lens and the convex lens, the collimating and beam expanding system realizes the divergence and beam expansion of the coaxial beams of the signal light and the beacon light, ensuring that the beam spot size of the incident liquid crystal optical phased array 7 can uniformly cover the effective aperture area of the liquid crystal optical phased array 7.

[0025] The signal light and the beacon light after collimation and beam expansion enter the liquid crystal optical phased array 7. As the core control device, the liquid crystal optical phased array 7 performs phase control on the signal light and the beacon light by loading an optimally designed voltage gray scale map to achieve synchronous deflection of multi-wavelength beams. In the embodiment of the present invention, the liquid crystal optical phased array 7 selects a pixel resolution of 1024×1024 and a single pixel size of 17μm. Based on the electro-optical effect of the liquid crystal material, the liquid crystal optical phased array 7 performs precise phase control on the beam by loading an optimally designed voltage gray scale map. In order to overcome the dispersion problem caused by different deflection angles of multi-wavelength beams due to the limitation of the grating equation in traditional LCOPA, the embodiment of the present invention provides a multi-wavelength co-directional control method based on a liquid crystal optical phased array. Specifically, to achieve the target co-directional deflection of the signal light and the beacon light of two wavelengths, the voltage gray scale distribution of each pixel point on the liquid crystal optical phased array 7 is specially optimized, and a voltage gray scale map is generated by optimizing with the principle of minimizing the complex amplitude least square error. Phase control is performed through this voltage gray scale map to achieve the same target deflection angle for the rotation of the signal light and the beacon light of different wavelengths. The specific control process is as follows: First, according to the application requirements, calculate and determine the target deflection angles of the signal light and the beacon light. In laser communication, it is usually necessary to deflect the beam to a specific angle to achieve precise link docking. The specific target deflection angle is calculated based on the design parameters of the optical system and the requirements of the communication link. The calculation process of the target deflection angle does not belong to the protection scope of the present invention, so it will not be described.

[0026] According to the determined target deflection angle, establish the target phase distribution of the signal light and the beacon light on the liquid crystal optical phased array 7, and calculate the target phase value of each pixel. The target phase distribution refers to the ideal phase value that each pixel on the liquid crystal optical phased array 7 should have, and this ideal phase value can ensure the co-directional deflection of the signal light and the beacon light to achieve the target deflection angle.

[0027] Provide the actual phase distribution of the liquid crystal optical phased array 7 at different voltage gray values. The actual phase distribution refers to the actual phase value of each pixel on the liquid crystal optical phased array 7 at a specific voltage gray value, and this actual phase distribution is usually obtained through actual measurement or simulation. Based on the phase optimization principle of minimizing the weighted complex amplitude least squares error, construct the weighted complex amplitude least squares error between the target phase value and the actual phase value , and take minimizing the weighted complex amplitude least squares error as the goal for voltage optimization to find a set of voltage gray values to minimize the error. This process needs to be iterated repeatedly until all constraint conditions are met and the optimal solution is obtained, as shown in the following formula:

[0028] Among them, and respectively represent the target phase complex amplitudes of two wavelengths, A 1 and A 2 respectively represent the actual phase complex amplitudes of two wavelengths, m and n are weight factors, and the weight factors can be flexibly adjusted according to the actual requirements for diffraction intensity in the dual-wavelength beam control process.

[0029] Calculate the optimal voltage gray value of each pixel on the liquid crystal optical phased array 7 according to the optimization result. The voltage gray value determines the phase modulation of each pixel on the liquid crystal optical phased array 7. Generate a voltage gray map with the optimal voltage gray values of all pixels. The voltage gray map is a two-dimensional array, and each element corresponds to the voltage gray value of a pixel on the liquid crystal optical phased array 7. Then load the generated voltage gray map onto the liquid crystal optical phased array 7. The liquid crystal optical phased array 7 regulates the phase of each pixel according to the voltage gray value. Through the electro-optical effect of the liquid crystal material, the arrangement direction of the liquid crystal molecules is regulated to generate a spatially varying phase modulation distribution, and independently adjust the phases of the 1550 nm signal light and the 808 nm beacon light respectively, so that the two different wavelengths are deflected by the same target deflection angle in the same direction. Through the above principle of minimizing the weighted complex amplitude least squares error, high-precision synchronous deflection of different wavelength beams in the same direction is achieved, breaking through the limitation of the traditional grating equation on the diffraction angle, and meeting the application requirements of high-precision optics such as multi-wavelength laser communication.

[0030] After phase modulation, the signal light and the beacon light are directed towards the autocollimator 8, which has a focal length of 5 meters. The autocollimator 8 is used for far-field calibration. Through a large-aperture design, the autocollimator 8 converts the beam deflection angle into the spatial position of the focal point. Finally, the beam focused by the autocollimator 8 reaches the imaging plane of the camera 9, and the camera 9 records the spot position and shape of the multi-wavelength beam, which is used to verify the consistency of the directions of the signal light and the beacon light and the accuracy of the co-directional regulation. In the embodiment of the present invention, the pixel size of the camera 9 is 15μm×15μm, and the pixel resolution is 640×512. The camera 9 is used to record the spot position and shape of the beam and can accurately capture the spot conditions of the multi-wavelength beam. During the actual test process, according to the imaging results of the camera 9, it shows that the spots of the 1550nm and 808nm beams completely overlap without obvious direction deviation, which proves that the multi-wavelength beam synchronous regulation method and device based on the liquid crystal optical phased array proposed in the embodiment of the present invention have high precision and high reliability.

[0031] As an alternative embodiment, in the embodiment of the present invention, only the dual-wavelength co-directional regulation is taken as an example. In specific applications, multi-wavelength co-directional regulation may be designed. The specific co-directional regulation process and principle are the same as those of the above dual-wavelength co-directional regulation. In terms of system structure, it may involve adding a laser and designing a beam combiner 3 so that it can combine multi-wavelength beams.

[0032] To prove the effectiveness of the system and method of the present invention, the present invention has been verified by simulation and experiment. Specifically: First, the multi-wavelength co-directional regulation based on the liquid crystal optical phased array is simulated. In the simulation stage, based on the voltage-phase relationship of two wavelengths (1550nm and 808nm), the embodiment of the present invention constructs a Figure 2 multi-wavelength two-dimensional voltage look-up table as shown. Among them, the abscissa and the ordinate respectively represent the phase values of the 1550nm and 808nm wavelengths, and the phase value range is from 0 to 2π. Figure 2 The different grayscales in it intuitively show the voltage grayscale distribution required under various phase combinations. Through this look-up table, the voltage grayscale value required under different phase combinations can be quickly determined. According to the phase combination required by the 1550nm signal light and the 808nm beacon light, the voltage grayscale value required by the pixels on the liquid crystal optical phased array 7 can be determined. Specifically, based on the Figure 2 phase distribution in it, the synchronous regulation performance of different wavelength beams is further verified, and the situation where the beams of 808nm and 155nm wavelengths are incident on the LCOPA simultaneously is simulated.

[0033] In the simulation, it is assumed that the horizontal and vertical deflection angles of the target are both 3 mrad. By loading the pre-generated single-wavelength voltage grayscale map and multi-wavelength voltage grayscale map, the deflection control of the signal light and the beacon light in the target direction is simulated. The voltage grayscale map loaded by the liquid crystal optical phased array 7 as shown in Figure 3 is obtained through the multi-wavelength co-directional regulation method based on the liquid crystal optical phased array. Figure 3 In (a) of Figure 3 is the single-wavelength voltage grayscale map for regulating the 808-nm beacon light to the target deflection angle; Figure 3 In (b) of Figure 3 is the single-wavelength voltage grayscale map for regulating the 1550-nm signal light to the target deflection angle. The voltage grayscale maps of the signal light and the beacon light both show a periodic distribution. The voltage grayscale map obtained by multi-wavelength synchronous regulation based on the voltage grayscale map of the 808-nm beacon light and the 1550-nm signal light shows an aperiodic and non-uniform distribution. This aperiodic characteristic is due to the fact that the phase of each pixel is optimized and selected according to the principle of minimizing the least squares error of multi-wavelength complex amplitude.

[0034] The simulation results of the diffraction light field obtained by the camera 9 show that when the 808-nm and 1550-nm light beams are incident on the liquid crystal optical phased array 7 simultaneously, their far-field light intensity distributions show obvious differences due to different loaded voltage grayscale maps.

[0035] For the voltage grayscale map for regulating the 1550-nm signal light, as shown in (a) and (b) of Figure 4 , when loading the conventional 1550-nm single-wavelength voltage grayscale map, the two-dimensional far-field diffraction pattern shows that the 1550-nm single light beam can be accurately deflected to the target angle, while when the 808-nm light beam is regulated according to this voltage grayscale map, it fails to be deflected to the target angle. Figure 4 On the contrary, for the voltage grayscale map for regulating the 808-nm beacon light, as shown in (c) and (d) of Figure 4 , when loading the conventional 808-nm single-wavelength voltage grayscale map, the two-dimensional far-field diffraction pattern shows that the 808-nm single light beam can be accurately deflected to the target angle, while when the 1550-nm light beam is regulated according to this voltage grayscale map, it fails to be deflected to the target angle.

[0036] For the multi-wavelength modulation voltage grayscale maps of the signal light and the beacon light obtained by the multi-wavelength co-directional regulation method based on the liquid crystal optical phased array of the present invention, as shown in (e) and (f) of Figure 4 , the 808-nm wavelength beacon light and the 1550-nm wavelength signal light are both successfully deflected to the target angle under the same voltage grayscale map. This result verifies the effectiveness of the multi-wavelength synchronous regulation method in realizing the synchronous co-directional regulation of two-wavelength light beams.

[0037] For the multi-wavelength modulation voltage grayscale maps of the signal light and the beacon light obtained by the multi-wavelength co-directional regulation method based on the liquid crystal optical phased array of the present invention, as shown in (e) and (f) of Figure 4 , the 808-nm wavelength beacon light and the 1550-nm wavelength signal light are both successfully deflected to the target angle under the same voltage grayscale map. This result verifies the effectiveness of the multi-wavelength synchronous regulation method in realizing the synchronous co-directional regulation of two-wavelength light beams.

[0038] After successful simulation verification, experimental verification is carried out. First, single-wavelength beam deflection voltage grayscale maps of the beacon light with a wavelength of 808 nm and the signal light with a wavelength of 1550 nm are generated, and the pointing errors of the beacon light with a wavelength of 808 nm and the signal light with a wavelength of 1550 nm under the regulation of the single-wavelength voltage grayscale map in the horizontal direction are measured through the system. The tests are divided into a small angle range (0.1 mrad to 1 mrad, with a step of 0.1 mrad) and a large angle range (1 mrad to 10 mrad, with a step of 1 mrad). 100 groups of data are collected at each deflection angle and statistically analyzed to obtain the pointing errors of the two-wavelength beams at different deflection angles. The pointing error curves at different angles of deflection are as shown in Figure 5 . In the figure, the abscissa is the deflection angle (Deflection angle), and the ordinate is the pointing error (Pointing accuracy).

[0039] Then, the beacon light with a wavelength of 808 nm and the signal light with a wavelength of 1550 nm are simultaneously incident on the liquid crystal optical phased array 7, and the voltage grayscale map capable of multi-wavelength regulation of the beacon light with a wavelength of 808 nm and the signal light with a wavelength of 1550 nm is generated by using the multi-wavelength co-directional regulation method based on the liquid crystal optical phased array proposed in the embodiment of the present invention to achieve synchronous co-directional deflection. For the same 10 small deflection angles and 10 large deflection angles as in the single-wavelength regulation, 100 groups of data points are measured, and the pointing errors of the two wavelengths under the regulation of the multi-wavelength voltage grayscale map are calculated. The results are as shown by the blue and green lines in Figure 5 . Through the statistical analysis of the experimental data, it can be clearly observed that in the small angle deflection range, the average pointing error of the 808 nm beam under dual-wavelength regulation is 2.37 μrad, while under single-wavelength regulation it is 2.056 μrad. The average pointing errors of the 1550 nm beam under dual-wavelength regulation and single-wavelength regulation are 2.76 μrad and 0.73 μrad respectively. In the large angle deflection range, the average pointing error of the 808 nm beam under dual-wavelength regulation is 9.97 μrad, while under single-wavelength regulation it is 9.17 μrad. The average pointing errors of the 1550 nm beam under dual-wavelength regulation and single-wavelength regulation are 8.56 μrad and 6.23 μrad respectively. It can be seen that in different angle deflection ranges, there is no significant difference in pointing accuracy between the multi-wavelength synchronous regulation method and the traditional single-wavelength method, showing good co-pointing characteristics.

[0040] As shown in Figure 6 , the multi-wavelength co-directional regulation method based on the liquid crystal optical phased array of the present invention has a single-wavelength regulation mode and a multi-wavelength regulation mode. For the 1550 nm and 1064 nm wavelength lights, in the single-wavelength regulation mode, as shown in Figure 6In FIGS. (a) and (b), the light beam is precisely deflected only at the corresponding target wavelength, and effective deflection cannot be achieved at the other wavelength. In the multi-wavelength co-directional regulation mode, as shown in Figure 6 FIG. (c), the light beams of both wavelengths are successfully deflected to the target angle under the action of the same voltage grayscale map.

[0041] The above simulation and test results show that by using the multi-wavelength co-directional regulation method based on a liquid crystal optical phased array proposed in the present invention to simultaneously regulate signal lights and beacon lights of different wavelengths, the pointing accuracy of the signal light and the beacon light after deflection is finally close to the deflection pointing accuracy of the traditional method that only regulates a single-wavelength light beam. It is proved that the multi-wavelength voltage grayscale map obtained by the method of the present invention can enable the light beams of both wavelengths to achieve highly accurate deflection in the same direction, solving the dispersion problem caused by different deflection angles of multi-wavelength light beams due to the limitation of the grating equation in traditional LCOPA, and can meet the high-precision information transmission requirements in multi-wavelength laser communication.

[0042] In conclusion, the above description is only a preferred embodiment of this specification and is not intended to limit the protection scope of this specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this specification shall be included within the protection scope of this specification.

[0043] The systems, devices, modules or units illustrated in the above one or more embodiments can be specifically implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer. Specifically, the computer can be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or any combination of these devices.

[0044] It should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements not only includes those elements but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, commodity or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, commodity or device including the said element.

[0045] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and the key point of each embodiment is to illustrate the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment.

[0046] The above description has been made of specific embodiments of the present specification. Other embodiments are within the scope of the appended claims. In some cases, the acts or steps recited in the claims may be performed in a different order than in the embodiments and still achieve the desired result. Additionally, the processes depicted in the figures do not necessarily require the particular order or sequential order shown to achieve the desired result. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A multi-wavelength co-directional control method based on liquid crystal optical phased array, characterized in that: include: The signal light and beacon light of different wavelengths are coaxially combined and incident on the liquid crystal optical phased array; According to the target deflection angles of the signal light and the beacon light, a target phase distribution of the signal light and the beacon light is established, and an ideal phase value of each pixel on the liquid crystal optical phased array is determined; Based on the phase optimization principle of minimizing the complex amplitude least squares error, the error between the target phase distribution and the actual phase distribution of the signal light and the beacon light is calculated, and the optimal voltage grayscale value of each pixel is obtained by minimizing the error, and a voltage grayscale map is generated; The liquid crystal optical phased array controls the arrangement direction of liquid crystal molecules according to the voltage grayscale image to generate a phase modulation distribution with spatial variation, so that the signal light and the beacon light achieve the same target deflection angle.

2. The multi-wavelength co-directional control method based on liquid crystal optical phased array according to claim 1, characterized in that: The signal light and the beacon light of different wavelengths are coaxially combined by a beam combiner.

3. The multi-wavelength co-directional control method based on liquid crystal optical phased array according to claim 1, characterized in that: It comprises a signal light beam and a beacon light beam, wherein the signal light beam is a Gaussian light beam with a wavelength of 1550nm, and the beacon light beam is a Gaussian light beam with a wavelength of 808nm.

4. The multi-wavelength co-directional control method based on liquid crystal optical phased array according to claim 1, characterized in that: After the signal light and the beacon light are coaxially combined, the polarization direction of the coaxial light beam is adjusted so that the polarization direction of the coaxial light beam is the same as the control direction of the liquid crystal optical phased array.

5. The multi-wavelength co-directional control method based on liquid crystal optical phased array according to claim 1, characterized in that: After the signal light and the beacon light are coaxially combined, the diameter of the coaxial light beam is adjusted to match the diameter of the coaxial light beam with the optical aperture of the liquid crystal optical phased array.

6. The multi-wavelength co-directional control method based on liquid crystal optical phased array according to claim 5, characterized in that: The diameter of the coaxial light beams of the signal light and the beacon light is adjusted by using a collimating beam expansion system, wherein the collimating beam expansion system comprises a first lens and a second lens; The first lens has a negative optical power and is used to expand the divergence angle of the coaxial light beam; the second lens has a positive optical power and is used to correct the divergence angle of the coaxial light beam.

7. A multi-wavelength co-directional control system based on liquid crystal optical phased array, characterized in that: include: A first laser for providing a signal light of a first wavelength; a second laser for providing beacon light at a second wavelength; beam combiner for repass; A polarizer for adjusting the polarization direction of the coaxial light beams of the signal light and the beacon light; Collimation and beam expansion system for adjusting the coaxial beam diameter; A liquid crystal optical phased array, which uses the multi-wavelength co-directional control method based on the liquid crystal optical phased array as described in any one of claims 1 to 6 to control the beams of the signal light and the beacon light.

8. The multi-wavelength co-directional control system based on liquid crystal optical phased array according to claim 7, characterized in that: Also includes: An autocollimator for far-field focusing of the signal light and the beacon light regulated by the liquid crystal optical phased array; A camera that images the signal light and the beacon light after being focused by the autocollimator analyzes the control consistency and pointing accuracy of the signal light and the beacon light through the acquired light spot image.

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