A lossless programmable arbitrary vector beam generation system and method

Abstract

The present invention discloses a lossless programmable arbitrary vector light beam generation system and method. The system comprises a laser, wherein the output laser of the laser passes through a polarizing plate, a first half-wave plate, a polarization beam splitter, a unitary transformation spatial light conversion system, a polarization beam combiner, a quarter-wave plate, a polarization analyzer and a CCD camera in sequence, wherein a second half-wave plate is further arranged between the polarization beam splitter and the unitary transformation spatial light conversion system, and a third half-wave plate is further arranged between the unitary transformation spatial light conversion system and the polarization beam combiner; the unitary transformation spatial light conversion system is composed of a plurality of phase planes and a plane reflector, and the unitary transformation spatial light conversion system is used for converting an ordinary Gaussian mode laser of orthogonal polarization outputted by the polarization beam splitter into a Laguerre Gaussian mode laser of orthogonal polarization; the phase planes are connected to a computer, and each phase plane displays a phase mask generated by an algorithm run by the computer.

Description

Technical Field

[0001] The present invention relates to the field of vector beams, and more particularly, to a system and method for generating lossless, programmable, and highly accurate arbitrary vector beams. Background Art

[0002] Vector beams refer to beams with uneven spatial polarization states. Common vector beams include radially polarized and azimuthally polarized vector beams. After being focused by a high numerical aperture lens, a strong longitudinal electric field component will be generated on the focal plane of the radially polarized vector beam, forming a clearer focus than a uniformly polarized beam; while the azimuthally polarized vector beam has a zero light intensity on the axis after focusing, producing a hollow light field distribution on the focal plane. Due to these special optical properties, vector beams are widely used in spectroscopy, high-resolution imaging, and optical capture. Many methods have been proposed to generate arbitrary vector beams, which can be divided into extra-cavity and intra-cavity generation methods. The extra-cavity generation method usually uses a spatial light modulator or a liquid crystal-based polarization converter to control the degree of freedom of polarization to generate an arbitrary vector beam; the intra-cavity generation method controls the structure of the laser resonator to make the laser emit the desired vector beam. These existing methods usually face the challenges of high loss, low conversion efficiency, and inflexible experimental schemes. In the present invention, we propose a lossless, efficient, and more flexible method for generating arbitrary vector beams.

[0003] Figure 1This is a device for generating arbitrary vector beams in a cavity in the prior art, see reference [1]. This device mainly generates arbitrary vector beams by inserting optical elements such as a quarter wave plate (QWP) and a q plate (QP) into a standard FP cavity, where the QWP is used to change the polarization state of light; the QP is an optical phase element that can map polarization control to orbital angular momentum (OAM) control: a left (right) circularly deflected Gaussian beam with a spiral charge number l = 0 can be transformed into a right (left) OAM beam with a spiral charge number l = ±q through the QP, and the positive or negative spiral charge number is related to the polarization state of the initial light. As shown in the figure, the horizontally polarized Gaussian beam emitted by the Nd:YAG laser is converted into a left-handed circularly deflected Gaussian beam after passing through a quarter-wave plate at 45 degrees to the axis. The QP converts the left-handed circularly deflected beam into a right-handed circularly deflected OAM beam with a spiral charge l=1. The reflection on the reflector placed at 45 degrees to the optical axis can reverse the polarization state and the spiral charge number, generating a left-handed circularly deflected OAM beam with a spiral charge l=-1. The superposition of two OAM beams with opposite polarization states and opposite spiral charge numbers can generate a vector beam with uneven polarization distribution. Therefore, by controlling the relative angle between QWP and QP, any vector beam can be generated. This technology can realize the generation of any vector beam in the laser cavity by changing the relative angle between QWP and QP. However, the generation of a specific vector beam through this device requires the precise setting of the rotation angle of QWP and QP. If multiple vector beams need to be generated, the rotation angles of QWP and QP need to be manually adjusted one by one, which makes this scheme lack flexibility in generating multiple vector beams. In addition, the QP surface is composed of a series of uneven phase elements, which is relatively complicated to manufacture.

[0004] Figure 2This is a device for generating arbitrary vector beams outside the cavity in the prior art, see reference [2]. The laser emits linear polarization in the x direction, which is expanded by a rotating beam expander and then converted into HG mode by a transmission-type spatial light modulator. A 4-fold focal length (4-f) system consisting of a pair of identical lenses (L1 and L2) with focal lengths of f is placed behind the spatial light modulator. The holographic grating (HG) on the spatial light modulator can diffract the incident beam into different orders. Only the ±1-order diffracted beams are allowed to pass through the spatial filter F located on the Fourier plane of the 4-f system, and then the ±1-order diffracted beams are converted into left-handed and right-handed circularly polarized beams, respectively. These two beams are recombined on the phase grating G placed at the rear focal plane of L2 to generate a vector beam. This technology can generate two Hermitian Gaussian (HG) modes with opposite polarization directions and opposite spiral charge numbers by setting the pattern diagram of the holographic grating on the SLM by a computer. The two HG modes are superimposed to generate an arbitrary vector beam, which is more flexible in the experimental scheme. However, in this device, the spatial light modulator has non-negligible diffraction losses. The grating G has only 40% diffraction efficiency for the first-order diffracted light. In addition, the mismatch between the HG mode generated by the SLM and the period of the grating G will also cause certain losses. Therefore, this technology has large losses and low mode conversion efficiency. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and solve the technical problems of large loss, low mode conversion efficiency, non-programmability, inflexible experimental scheme, etc. in the above-mentioned existing devices for generating arbitrary vector beams. A lossless programmable arbitrary vector beam generation system and method are provided.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A lossless programmable arbitrary vector beam generation system comprises a laser, wherein the output laser of the laser passes through a polarizer, a first half-wave plate, a polarization beam splitter, a unitary transformation spatial light conversion system, a polarization beam combiner, a quarter-wave plate, a polarization analyzer and a CCD camera in sequence, a second half-wave plate is further arranged between the polarization beam splitter and the unitary transformation spatial light conversion system, and a third half-wave plate is further arranged between the unitary transformation spatial light conversion system and the polarization beam combiner; the unitary transformation spatial light conversion system is composed of a plurality of phase planes and a plane reflector, and the unitary transformation spatial light conversion system is used for converting an ordinary Gaussian mode laser of orthogonal polarization outputted by the polarization beam splitter into a Laguerre Gaussian mode laser of orthogonal polarization; the phase planes are connected to a computer, and each phase plane displays a phase mask generated by an algorithm run by the computer.

[0008] Furthermore, the phase plane is divided into an upper part and a lower part, respectively realizing mode conversion of polarized light in the X and Y directions.

[0009] Furthermore, the phase mask is obtained by a wavefront matching algorithm. In a unitary transformation spatial light conversion system, all forward propagation input fields and backward propagation output fields are moved forward to the next plane together, or moved backward to the previous plane together, and iterated until the error is minimized.

[0010] The present invention also provides a lossless programmable arbitrary vector beam generation method, wherein a laser emits a linearly biased Gaussian mode laser, which is converted into an arbitrary linearly biased Gaussian mode laser by using a polarizing plate and a first half-wave plate;

[0011] The linearly deflected Gaussian mode laser is propagated into the polarization beam splitter and is divided into vertically and horizontally polarized linearly deflected Gaussian mode lasers, wherein the horizontally deflected Gaussian mode laser is converted into a vertical polarization direction that can be modulated by the phase plane through the second half-wave plate; then the two vertical linearly deflected Gaussian mode lasers are respectively incident on the upper and lower parts of the phase plane, and are converted into two vertically deflected Laguerre-Gaussian mode lasers with controllable relative phases through mode conversion, wherein one vertically deflected Laguerre-Gaussian mode laser is converted into a horizontally deflected Laguerre-Gaussian mode laser through the third half-wave plate, and two orthogonal linearly deflected Laguerre mode lasers are obtained and superimposed on the polarization beam combiner to generate a vector beam, and then the horizontal and vertical linear polarization components in the synthesized vector beam are converted into left circular and right circular polarization components respectively using a quarter-wave plate; finally, the generated vector beam is detected by a polarization analyzer and a CCD camera.

[0012] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0013] 1. The present invention mainly utilizes a unitary transformation spatial light conversion system, which can perform lossless and high-precision arbitrary spatial mode conversion. The unitary transformation spatial light conversion system consists of a phase plane and a plane reflector. The spatial phase conversion is realized by a series of lateral phase masks separated by Fourier transform on the phase plane, and arbitrary spatial conversion can be performed between the orthogonal input and output mode bases of the spatial mode. The present invention adopts the form of spatial diversity to divide the phase plane in the unitary transformation spatial light conversion system into an upper and lower part, corresponding to the polarization in the x and y directions respectively. These two parts can convert the ordinary Gaussian mode of orthogonal polarization generated after the polarization beam splitter into an arbitrary orthogonal polarization Laguerre Gaussian (LG) mode, and make it carry relative phase. The two orthogonal polarization Laguerre Gaussian modes are then converted into left-handed and right-handed circularly polarized Laguerre Gaussian modes respectively through a quarter-wave plate. The superposition of left-handed and right-handed circularly polarized Laguerre Gaussian modes with relative phase can generate arbitrary vector beams. Since this mode conversion process is a transformation from one mode basis (ordinary Gaussian mode of orthogonal polarization) to another mode basis (Laguerre-Gaussian mode of orthogonal polarization), it can be regarded as a spatial unitary transformation. Although the unitary transformation spatial light conversion system changes the spatial characteristics of the light field, it does not increase or decrease its energy, so there is no inherent energy loss.

[0014] 2. The present invention mainly utilizes the unitary transformation spatial light conversion system, half-wave plate and quarter-wave plate, which can convert ordinary orthogonal linearly polarized Gaussian beams into left- and right-handed circularly polarized Laguerre-Gaussian modes without loss and with high efficiency, realize the conversion of orthogonal polarization modes, and make them have controllable relative phase. The superposition of orthogonal polarized Laguerre-Gaussian modes with relative phase can generate arbitrary vector beams.

[0015] 3. The phase mask on the phase plane in the unitary transformation spatial light conversion system proposed in the present invention has programmable characteristics. First, set the target mode for the polarization diversity phase plane respectively, run the MATLAB code, and obtain the phase mask information on the phase plane through the wavefront matching algorithm, so that the ordinary Gaussian beam can be transformed into the target Laguerre Gaussian mode. Compared with the traditional q-plate, its adjustment method is more flexible.

[0016] 4. The unitary transformation spatial light conversion system proposed by the present invention allows lossless transformation of arbitrary spatial modes. It operates as a discrete Fourier transform through continuous lateral phase masks separated by free space propagation, thereby achieving the generation of any set of orthogonal spatial modes. Compared with a spatial light modulator with only one phase plane, this system has higher conversion efficiency and higher accuracy of mode conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The invention is a device for generating an arbitrary vector light beam in a cavity in the prior art.

[0018] Figure 2 The invention is a device for generating an arbitrary vector light beam outside a cavity in the prior art.

[0019] Figure 3 It is a schematic diagram of the structure of the arbitrary vector light beam generating system of the present invention.

[0020] Figure 4 Schematic diagram of a discretized phase mask on a phase plane used for mode conversion according to the present invention.

[0021] Figure 5 This is a theoretical schematic diagram of the present invention using the superposition method to generate four special first-order linear polarization vector LG beams.

[0022] Figures 6a to 6d They are schematic diagrams of experimental simulation results of four special first-order linear polarization vector LG light beams according to the present invention. Figure 6a is the experimental simulation result of radially polarized LG01 beam, Figure 6b is the experimental simulation result of azimuthally polarized LG01 beam, Figure 6c is the experimental simulation result of the anti-vortex LG01 beam, Figure 6d for relative to Figure 6c Experimental simulation results of the antivortex LG01 beam after rotating 45° clockwise.

[0023] Figure 7a and Figure 7b Schematic diagram of experimental simulation results of two high-order radially polarized vector beams (LG11 and LG21) using the method of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] like Figure 3The present embodiment shows a lossless programmable arbitrary vector beam generating system, comprising a laser 1, wherein the output laser of the laser 1 passes through a polarizer 2, a half-wave plate 3, a polarization beam splitter 4, a unitary transformation spatial light conversion system 6, a polarization beam combiner 8, a quarter-wave plate 9, a polarization analyzer 10 and a CCD camera 11 in sequence, a half-wave plate 5 is further arranged between the polarization beam splitter 4 and the unitary transformation spatial light conversion system 6, and a half-wave plate 7 is further arranged between the unitary transformation spatial light conversion system 6 and the polarization beam combiner 8; the unitary transformation spatial light conversion system is composed of a plurality of phase planes 601 and a plane reflector 602, and the unitary transformation spatial light conversion system 6 is used to convert the ordinary Gaussian mode laser of orthogonal polarization output by the polarization beam splitter 4 into the Laguerre Gaussian mode laser of orthogonal polarization; the phase planes 601 are connected to a computer, and each phase plane 601 displays a phase mask generated by an algorithm run by the computer.

[0026] Specifically, any desired lossless conversion of spatial modes between the input plane and the output plane can be achieved by a series of transverse phase masks separated by optical Fourier transform. The unitary transformation spatial light conversion system 6 in this embodiment allows the lossless conversion of any spatial mode, which is composed of a series of phase planes 601 and plane reflectors 602, and each phase plane corresponds to a phase mask generated by an algorithm. This unitary transformation spatial light conversion system uses continuous transverse phase masks separated by free space propagation as discrete Fourier transform operations, thereby achieving the generation of any set of orthogonal spatial modes.

[0027] For a given mode conversion, the phase mask on the phase plane in the unitary transformation spatial light conversion system can be obtained by the wavefront matching algorithm (WFM), see reference [3]. Figure 4 The wavefront matching algorithm is implemented by forward propagating the input field and backward propagating the output field in the unitary transformation spatial light conversion system. The only way to achieve an input stimulating a corresponding output is to completely match the phase of the forward propagation input field fi and the backward propagation output field bi at each spatial coordinate. When the phase of the input and output fields does not match, the phase error at each spatial coordinate can be calculated and corrected on the phase plane corresponding to each spatial position coordinate. This is the optimization process of the phase mask. In the unitary transformation spatial light conversion system, the wavefront matching algorithm moves all fi and bi forward to the next plane together, or moves them backward to the previous plane together, and iterates until the error is minimized.

[0028] The phase error ΔΦ applied to each plane k (x, y) can be calculated from the field overlap matrix on the kth plane:

[0029]

[0030] Overlap integral matrix O k With item O kij , which can quantify the degree of coupling between each input and output mode:

[0031] O kij (z) = ∫∫o kij (x,y)dxdy

[0032] In the unitary transformation spatial light conversion system, in order to achieve the maximum mode conversion efficiency, it is necessary to minimize the system's mode-dependent loss (MDL) and insertion loss (IL) to determine the optimal phase mask profile. MDL is defined as the matrix O k The ratio of the largest to the smallest squared singular value of IL is the mean of the squared singular values. Since the phase mask and free space propagation are lossless transformations, O kij The magnitude of (z) remains constant with z; however, at each z, the spatial profile of okij(x,y) can be very different, which means that local phase optimization can minimize the global error. Phase optimization techniques find the best phase mask profile by taking a weighted average of all field overlaps.

[0033]

[0034] in O kii The average phase, O kii represents the overlap matrix of the forward propagation input field fi and the backward propagation output field bi; kij Represents the overlap matrix of the forward propagation input field fi and the backward propagation output field bj; once the phase mask Φ on the kth plane k (x, y) is updated, fi and bi will be propagated forward or backward to the next plane together through the unitary transformation spatial light conversion system, and convergence will be achieved by continuously enforcing phase matching in each iterative step, and finally the phase mask contour on the phase plane of the unitary transformation spatial light conversion system is determined.

[0035] In the polarization-diversified unitary transformation spatial light conversion system proposed in the present invention, in order to realize the generation of arbitrary vector light beams, according to specific mode conversion, a wavefront matching algorithm is used to generate corresponding phase mask contours on the phase planes in two polarization directions, and the generated phase masks are used to realize mode conversion in the two polarization directions.

[0036] The principle of using the polarization diversity unitary transformation spatial light conversion system to convert the ordinary Gaussian mode of orthogonal polarization output by the polarization beam splitter into the Laguerre Gaussian mode of orthogonal polarization is as follows:

[0037] For the sake of simplicity, the Laguerre-Gaussian mode laser is hereinafter referred to as LG mode laser.

[0038] The phase plane in the unitary transformation spatial light conversion system is divided into an upper part and a lower part, respectively realizing mode conversion of polarized light in the x and y directions. According to the method of generating arbitrary vector beams by superposition of LG mode lasers, in order to generate a target vector beam, the LG mode lasers to be superimposed are first set in two directions, that is, the target output modes in the two directions, and the inputs in the two directions are linearly polarized coherent ordinary Gaussian mode lasers. For such a given mode conversion, run the MATLAB code to obtain the upper and lower sets of phase masks respectively, and then import the upper and lower sets of phase mask information into the x and y direction phase plates in the unitary transformation light conversion system respectively; the ordinary linearly polarized Gaussian mode laser emitted by the laser is converted into vertical and horizontal linearly polarized mode lasers through a polarization beam splitter. Since the phase plane in this embodiment can only perform mode conversion for vertical linear polarization, the horizontally polarized light first passes through the half-wave plate in front of the phase plane to rotate the horizontal polarization to the vertical polarization state, and then they are respectively incident on the upper and lower parts of the unitary transformation spatial light conversion system. At this time, the phase mask on the polarization diversity phase plane can convert two vertically deflected ordinary Gaussian mode lasers into two vertically deflected LG mode lasers with controllable relative phases, and one of the vertically deflected LG mode lasers is then converted into a horizontally deflected LG mode laser through a half-wave plate; the polarization beam combiner recombines the two vertically and horizontally deflected LG mode lasers into a beam, maintaining their respective horizontal and vertical polarization states, thereby forming a vector beam with an uneven spatial polarization distribution. In order to create a special type of linearly polarized vector beam (i.e., linear polarization at each local position, but the linear polarization direction varies with the spatial position), a quarter-wave plate is placed behind the polarization beam combiner. It converts the horizontal and vertical linear polarization components in the synthesized vector beam into left-circular and right-circular polarization components, respectively, so that a special linearly polarized vector beam can be generated by superposition.

[0039] Theoretically, orthogonal mode coherent superposition can generate any vector beam, see reference [4]. Specifically, this embodiment adopts the LG superposition method of left-handed and right-handed circular polarization to generate any vector beam by superimposing two left-handed and right-handed circular polarization LG mode lasers with relative phases. Figure 5This is a theoretical schematic diagram of the superposition of two left-handed and right-handed circularly deflected LG modes to generate four types of special first-order linearly polarized vector beams. The first row shows the coherent superposition of the left-handed circularly deflected LG01 mode laser and the right-handed circularly deflected LG0-1 mode laser with a relative phase of 0 (i.e., the corresponding electric field amplitude reaches the corresponding maximum and minimum values ​​at the same time), and the superposition produces a radially polarized vector LG01 beam; in the second row, the LG0-1 mode laser has a phase shift of π, and the superposition produces an azimuthal polarized vector LG01 beam; the third row shows the coherent superposition of the left-handed circularly deflected LG0-1 mode laser and the right-handed circularly deflected LG01 mode laser with a relative phase of 0 (i.e., the corresponding electric field amplitude reaches the corresponding maximum and minimum values ​​at the same time), and the anti-vortex vector LG01 beam is generated; in the last row, the LG0-1 mode laser has a phase shift of π, and the superposition still produces an anti-vortex vector LG01 beam, but it is rotated 45 degrees relative to the result of the third row. More complex high-order vector beams can also be obtained by superposition of high-order orthogonal LG modes.

[0040] Specifically, a method for generating an arbitrary vector beam based on the above beam generating system includes the following steps:

[0041] Laser 1 emits a linearly polarized basic Gaussian mode laser, which can be transformed into an arbitrary linearly polarized Gaussian mode laser by using polarizer 2 and half-wave plate 3;

[0042] Afterwards, the linearly deflected Gaussian mode laser is propagated to a polarization beam splitter 4 and is divided into vertically and horizontally polarized linearly deflected Gaussian mode lasers, wherein the horizontally deflected Gaussian mode laser is converted into a linearly deflected Gaussian mode laser of a vertical polarization direction that can be modulated by the phase plane through a half-wave plate 5. Afterwards, the two vertically deflected Gaussian mode lasers are respectively incident on the upper and lower parts of the polarization diversity phase plane 601, and after mode conversion, the two vertically deflected Gaussian mode lasers are respectively converted into vertically deflected Laguerre Gaussian mode lasers with controllable relative phases, and one of the vertically deflected Laguerre Gaussian mode lasers is converted into a horizontally deflected Laguerre Gaussian mode laser through a half-wave plate 7, thus realizing the conversion of orthogonal modes using the unitary transformation optical conversion system 6;

[0043] Afterwards, the two orthogonal linearly polarized Laguerre mode lasers are superimposed on the polarization beam combiner 8 to generate a vector beam, and then the quarter-wave plate 9 is used to convert the horizontal and vertical linear polarization components in the synthesized vector beam into left circular and right circular polarization components respectively; finally, the generated vector beam is detected by the polarization analyzer 10 and the CCD camera 11.

[0044] The experimental simulation results of the present invention for four special first-order linear polarization vector LG mode beams and two high-order vector beams are as follows: Figures 6a to 7bAs shown. The unitary transformation light conversion system can realize lossless transformation of orthogonal modes, and the phase mask on the phase plane has programmable characteristics. In summary, the results show that the arbitrary vector beam generation system proposed in the present invention can realize the generation of arbitrary vector beams losslessly, efficiently and flexibly.

[0045] Finally, it should be pointed out that the above examples are only used to illustrate the calculation process of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above examples, a person skilled in the art should understand that the calculation process described in the above examples can still be modified, or some parameters can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding calculation method deviate from the spirit and scope of the calculation method of the present invention.

[0046] The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solution of the present invention. The above specific embodiments are merely illustrative and not restrictive. Without departing from the scope of the present invention and the scope of protection of the claims, a person of ordinary skill in the art can also make many forms of specific changes under the guidance of the present invention, which all fall within the scope of protection of the present invention.

[0047] References:

[0048] [1] Naidoo, Darryl, et al. "Controlled generation of higher-order Poincarésphere beams from a laser." Nature Photonics 10.5(2016):327-332.

[0049] [2] Xi-Lin, et al. "Generation of arbitrary vector beams with a spatiallight modulator and a common path interferometric arrangement." Optics letters32.24(2007):3549-51.

[0050] [3]Sakamaki, Y., et al. "New Optical Waveguide Design Based on WavefrontMatching Method." Journal of Lightwave Technology 25.11(2007):3511-3518.

[0051] [4]Shizhen,et al."Generation of arbitrary cylindrical vector beams onthe higher order Poincarésphere."Optics Letters(2014).

Claims

1. A lossless programmable arbitrary vector beam generation system, comprising a laser, characterized in that: The output laser of the laser passes through a polarizer, a first half-wave plate, a polarization beam splitter, a unitary transformation spatial light conversion system, a polarization beam combiner, a quarter-wave plate, a polarization analyzer and a CCD camera in sequence; a second half-wave plate is further arranged between the polarization beam splitter and the unitary transformation spatial light conversion system, and a third half-wave plate is further arranged between the unitary transformation spatial light conversion system and the polarization beam combiner; the unitary transformation spatial light conversion system is composed of a plurality of phase planes and a plane reflector, and the unitary transformation spatial light conversion system is used to convert the ordinary Gaussian mode laser of orthogonal polarization output by the polarization beam splitter into the Laguerre Gaussian mode laser of orthogonal polarization; the phase planes are connected to a computer, and each phase plane displays a phase mask generated by an algorithm run by the computer.

2. A lossless programmable arbitrary vector beam generation system according to claim 1, characterized in that: The phase plane is divided into an upper part and a lower part, which respectively realize the mode conversion of polarized light in the X and Y directions.

3. A lossless programmable arbitrary vector beam generation system according to claim 1, characterized in that: The phase mask is obtained by a wavefront matching algorithm. In a unitary transformation spatial light conversion system, all forward propagation input fields and backward propagation output fields are moved forward to the next plane together, or moved backward to the previous plane together, and iterated until the error is minimized.

4. A method for generating a lossless and programmable arbitrary vector beam, based on the beam generating system according to any of claims 1 to 3, characterized in that: The laser emits a linearly biased Gaussian mode laser, which is converted into an arbitrary linearly biased Gaussian mode laser by using a polarizer and a first half-wave plate; The linearly deflected Gaussian mode laser is propagated into the polarization beam splitter and is divided into vertically and horizontally polarized linearly deflected Gaussian mode lasers, wherein the horizontally deflected Gaussian mode laser is converted into a vertical polarization direction that can be modulated by the phase plane through the second half-wave plate; then the two vertical linearly deflected Gaussian mode lasers are respectively incident on the upper and lower parts of the phase plane, and are converted into two vertically deflected Laguerre-Gaussian mode lasers with controllable relative phases through mode conversion, wherein one vertically deflected Laguerre-Gaussian mode laser is converted into a horizontally deflected Laguerre-Gaussian mode laser through the third half-wave plate, and two orthogonal linearly deflected Laguerre mode lasers are obtained and superimposed on the polarization beam combiner to generate a vector beam, and then the horizontal and vertical linear polarization components in the synthesized vector beam are converted into left circular and right circular polarization components respectively using a quarter-wave plate; finally, the generated vector beam is detected by a polarization analyzer and a CCD camera.

Images