Phase distribution design method and device for multi-plane light converter
By combining the total loop iterative calculation of WFM and GS algorithms, the problem of unknown target optical field phase distribution is solved, and the phase distribution design of multi-plane optical converter is realized, supporting static and dynamic adjustable custom optical field transformation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHAN POST & TELECOMM RES INST CO LTD
- Filing Date
- 2026-02-10
- Publication Date
- 2026-04-24
AI Technical Summary
In existing technologies, it is difficult to obtain the phase distribution of the phase plane of a multiplane optical converter (MPLC) when the phase distribution of the target optical field is ignored.
By combining the wavefront matching (WFM) algorithm and the Gerchberg-Saxton (GS) algorithm, the phase distribution of multiple phase planes is obtained through total iterative calculation. This includes updating the phase distribution using the WFM algorithm and using the GS algorithm to correlate the amplitude of the target light field to achieve iterative calculation of the phase distribution.
Even if only the amplitude of the target light field is known but the phase is unknown, the phase distribution of each phase plane of the multi-plane optical converter can be obtained through iterative calculation, realizing static and dynamic adjustable custom light field transformation.
Smart Images
Figure CN121918299A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of optics and beam manipulation technology, and in particular to a phase distribution design method and apparatus for a multi-plane optical converter. Background Technology
[0002] A multiplane light converter (MPLC) is a novel type of optical manipulation device composed of multiple spatially spaced phase planes stacked together. Theoretically, it can perform arbitrary unitary transformations, converting any set of spatial modes into any new set of spatial modes. This ability to perform arbitrary linear transformations gives MPLCs great application potential in optical communication, optical computing, and imaging. It is often used for mode multiplexing / demultiplexing and has recently been seen as an optical replacement for neural networks, enabling functions such as image classification and image encryption.
[0003] The design focus of MPLC lies in obtaining the phase delay distribution of the phase plane, which is achieved through reverse engineering, with the most commonly used method being Wavefront Matching (WFM). This algorithm requires knowledge of the complex amplitudes of both the input and target optical fields. It updates the phase by repeatedly propagating the optical fields forward and backward and integrating the overlapping areas of the optical fields before and after the phase plane, typically achieving fast convergence. However, aside from mode multiplexing / demultiplexing, in many other application areas, designers often neglect the phase distribution of the target optical field, only considering its amplitude, such as in beam deflection, image classification, and holographic reconstruction. In such cases, the complex amplitude of the target optical field is not explicit, causing the WFM algorithm to fail to execute effectively, thus preventing the acquisition of the phase distribution of the MPLC phase plane. Summary of the Invention
[0004] This application provides a phase distribution design method and apparatus for a multi-plane optical converter, to solve the problem in related technologies that it is difficult to obtain the phase distribution of the MPLC phase plane when the phase distribution of the target optical field is ignored.
[0005] In a first aspect, embodiments of this application provide a phase distribution design method for a multi-plane optical converter, comprising: Perform a total iterative calculation, which includes: - The wavefront matching algorithm is used to obtain the first output light field and the phase distribution of each phase plane when iterating for the first preset number of times. The first output light field is the forward propagation light field of the last phase plane when the incident light propagates forward. -Based on the first output light field and the target light field of the target plane, the GS algorithm is used to obtain the forward propagation light field of the virtual phase surface of the target plane when the first output light field propagates forward at the second preset number of iterations; Determine whether the total loop iteration calculation meets the termination condition. If the total loop iteration calculation meets the termination condition, output the phase distribution of each phase plane obtained by the last total loop iteration calculation.
[0006] In conjunction with the first aspect, in one implementation, the termination condition includes the total number of iterations of the total loop iteration calculation reaching a third preset number, or the forward propagation light field of the virtual phase surface of the target plane and the target light field of the target plane converging when the first output light field propagates forward.
[0007] In conjunction with the first aspect, in one implementation, the design method further includes, prior to performing the total iterative calculation, the following: When the light field is initialized, the forward propagation light field of each phase plane is obtained during the forward propagation of the incident light.
[0008] In conjunction with the first aspect, in one implementation, obtaining the first output light field and the phase distribution of each phase plane after a first preset number of iterations includes: First, obtain the backward propagation light field of each phase plane when the target light propagates backward, and update the phase distribution of each phase plane except the last phase plane. Then, obtain the forward propagation light field of each phase plane when the input light propagates forward, and update the phase distribution of each phase plane except the last phase plane. This completes one WFM loop iteration calculation. By repeating this process, the WFM iterative calculation is completed for the first preset number of times, resulting in the first output light field and the phase distribution of each phase plane.
[0009] In conjunction with the first aspect, in one embodiment, acquiring the backward propagation light field of each phase plane during the backward propagation of the target light, and updating the phase distribution of each phase plane except the last phase plane, includes: First, obtain the backpropagation light field of the phase plane when the target light propagates backward; Then, based on the backward propagating light field and the forward propagating light field of the phase plane, the phase distribution is obtained, and the phase plane is updated using the phase distribution; Finally, the target light passes through this phase plane and continues to propagate backward.
[0010] In conjunction with the first aspect, in one embodiment, acquiring the forward propagation optical field of each phase plane during the forward propagation of the input light, and updating the phase distribution of each phase plane except the last phase plane, includes: First, obtain the forward propagation optical field of the phase plane when the incident light propagates forward; Then, based on the forward propagation light field and the backward propagation light field of the phase plane, the phase distribution is obtained, and the phase plane is updated using the phase distribution. Finally, the incident light passes through this phase plane and continues to propagate forward.
[0011] In conjunction with the first aspect, in one implementation, based on the first output light field and the target light field of the target plane, the GS algorithm is used to obtain the forward propagation light field of the virtual phase surface of the target plane when the first output light field propagates forward at a second preset number of iterations, including: Obtain the forward propagation light field of the virtual phase plane of the target plane when the first output light field continues to propagate forward after passing through the last phase plane; keep the phase distribution of the forward propagation light field unchanged, and construct the first amplitude constraint light field in combination with the amplitude of the target light field; obtain the backward propagation light field of the first phase plane when the first amplitude constraint light field propagates backward, and complete one GS loop iteration calculation; Determine whether the number of iterations in the GS loop iteration calculation has reached the second preset number; If not, keep the amplitude of the first output light field unchanged, and combine it with the phase distribution of the backward propagation light field of the first phase plane when the first amplitude-constrained light field propagates backward, construct the second amplitude-constrained light field, and obtain the forward propagation light field of the virtual phase plane of the target plane when the second amplitude-constrained light field propagates forward; keep the phase distribution of the forward propagation light field unchanged, and combine it with the amplitude of the target light field to construct the first amplitude-constrained light field; If so, proceed to determine whether the total loop iteration calculation meets the termination condition.
[0012] In conjunction with the first aspect, in one implementation, if the total loop iteration calculation does not meet the termination condition, the backward propagation light field of the first phase plane when the first amplitude constraint light field propagates backward is taken as the backward propagation light field of the first phase plane when the target light propagates backward, and the process returns to using the wavefront matching algorithm to obtain the first output light field and the phase distribution of each phase plane when iterating for the first preset number of times.
[0013] Secondly, embodiments of this application provide a phase distribution design apparatus for a multi-plane optical converter, comprising: The WFM algorithm processing unit is used to execute the wavefront matching algorithm, obtain the first output light field and the phase distribution of each phase plane when iterating for the first preset number of times. The first output light field is the forward propagation light field of the last phase plane when the incident light propagates forward. The GS algorithm processing unit is used to execute the GS algorithm based on the first output light field and the target light field of the target plane to obtain the forward propagation light field of the virtual phase surface of the target plane when the first output light field propagates forward after a second preset number of iterations. An iterative control unit is used to coordinate the WFM algorithm processing unit and the GS algorithm processing unit to perform overall iterative calculations. The termination judgment unit is used to determine whether the total loop iteration calculation meets the termination condition. A phase distribution output unit is used to output the phase distribution of each phase plane obtained by the last total loop iteration calculation if the total loop iteration calculation meets the termination condition.
[0014] Thirdly, embodiments of this application provide a multi-plane optical converter, which includes multiple phase planes, and the phase distribution of each phase plane is obtained by adopting the phase distribution design method of the multi-plane optical converter as described above.
[0015] The beneficial effects of the technical solution provided in this application include: This application introduces the GS algorithm and links it with the WFM algorithm. The WFM algorithm is used to update the phase distribution of each phase plane, and the GS algorithm is used to associate the optical field of the last phase plane with the optical field of the virtual phase plane of the target plane as much as possible. After the overall loop iteration calculation is completed, the phase distribution of each phase plane can be obtained. It can be seen that even if only the amplitude of the target optical field is known but the phase is unknown, the phase distribution of each phase plane of the multi-plane optical converter can be obtained through iterative loop calculation. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 This is a schematic diagram of a static multi-plane optical converter provided in an embodiment of this application; Figure 2 A flowchart of iterative calculation provided for embodiments of this application; Figure 3 This is a schematic diagram illustrating the design and application of a multi-input single-output static multiplane optical converter provided in an embodiment of this application. Figure 4 A schematic diagram of a dynamically adjustable mechanical multiplane optical converter provided in an embodiment of this application; Figure 5 A schematic diagram illustrating the design and application of a single-input multiple-output dynamically adjustable mechanical multiplane optical converter (mode switching) provided in this application embodiment. Figure 6A schematic diagram illustrating the design and application of a single-input multiple-output dynamically adjustable mechanical multiplane optical converter (holographic switching) provided in this application embodiment. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0019] The design focus of a multi-plane optical converter (MPLC) lies in obtaining the phase delay distribution of the phase plane, which is achieved through reverse engineering. See also... Figure 1 As shown, the multi-plane optical converter includes N phase planes, where N≥2. The phase plane is a plane with phase modulation function, usually called a phase plate, while the target plane is the observation plane for observing the image of the target. The N phase planes are set sequentially at intervals and are numbered sequentially as the 1st phase plane, the 2nd phase plane, and so on up to the Nth phase plane. Finally, the target plane is set after the Nth phase plane and numbered as the N+1th layer. It is usually assumed that the target plane has a virtual phase surface, denoted as the N+1th virtual phase surface, for use in subsequent calculations. In fact, the N+1th virtual phase surface does not exist.
[0020] The incident light travels from the first phase plane to the (N+1)th virtual phase plane, which is called the forward propagation of the incident light. At the same time, the target light travels from the (N+1)th virtual phase plane to the first phase plane, which is called the backward propagation of the target light.
[0021] It is understandable that forward propagation and backward propagation are in opposite directions.
[0022] It is understandable that during forward propagation, the first phase plane reached by the incident light is the first phase plane, the second phase plane reached by the incident light is the second phase plane, and so on, until the Nth phase plane reached by the incident light is the Nth phase plane.
[0023] Understandably, during backward propagation, the first phase plane reached by the target light is the Nth phase plane, the second phase plane reached is the (N-1)th phase plane, and so on. The Nth phase plane reached by the target light is the 1st phase plane. For a better understanding, see [link to relevant documentation]. Figure 1 As shown below, the phase planes of each layer are numbered in the forward propagation order in this application.
[0024] Typically, during reverse engineering, apart from the phase distribution of each phase plane layer which needs to be calculated, other relevant parameters of the multi-plane optical converter are known quantities. These include the required incident light wavelength, the total number of phase plane layers N, the number of pixels in the phase plane, the pixel side length, the interlayer spacing between two adjacent phase plane layers, and the distance between the target plane and the Nth phase plane. At the same time, the complex amplitude of the input light field and the complex amplitude of the target light field are also known, and the wavefront matching algorithm WFM can be used to calculate them.
[0025] However, when the amplitude of the target light field is known but the phase is unknown, the above calculation method cannot obtain the phase distribution of each phase plane.
[0026] Based on this, this application proposes a phase distribution design method for a multi-plane optical converter, which can solve the problem in related technologies that it is difficult to obtain the phase distribution of the MPLC phase plane when the phase distribution of the target optical field is ignored.
[0027] See Figure 2 As shown in the figure, the phase distribution design method of a multi-plane optical converter provided in this application includes steps 101 and 102.
[0028] 101: Perform a total iterative calculation, which includes: The wavefront matching algorithm is used to obtain the first output light field and the phase distribution of each phase plane when iterating for a first preset number of times. The first output light field is the forward propagation light field of the last phase plane when the incident light propagates forward. Based on the first output light field and the target light field of the target plane, the GS algorithm is used to obtain the forward propagation light field of the virtual phase plane of the target plane when the first output light field propagates forward when iterating for a second preset number of times.
[0029] 102: Determine whether the total loop iteration calculation meets the termination condition. If the total loop iteration calculation meets the termination condition, output the phase distribution of each phase plane obtained by the last total loop iteration calculation.
[0030] The overall iterative calculation in this application consists of two parts. The first part uses the WFM algorithm to update the phase distribution of each phase plane. The second part correlates the amplitude of the forward propagation optical field of the last phase plane with the amplitude of the target optical field during the forward propagation of the incident light in the first part, and performs the calculation using the GS algorithm. The GS (Gerchberg-Saxton) algorithm is a phase retrieval algorithm commonly used in single-layer designs. When introducing the GS algorithm in this application, the target optical field is... amplitude As input light, the forward propagation light field of the last phase plane of the first part of the output will be used. amplitude As the target output amplitude, the target light field is made possible by searching the (N+1)th layer virtual phase surface. After backpropagation, the amplitude is as close as possible to... The actual backpropagation output of the Nth phase plane is the backpropagating optical field. The next WFM algorithm calculation will then begin. The GS algorithm also requires repeated forward and backward propagation of the light fields on both sides. After forward propagation, the... Forcefully replace the amplitude components of the light field, and use them after backpropagation. The amplitude components of the light field are forcibly replaced, so that the light field of the Nth phase plane is associated with the light field of the N+1th virtual phase plane as much as possible.
[0031] The total iterative calculation ends after the termination condition is met, and the phase distribution of each phase plane obtained by the last total iterative calculation is output, thereby designing the phase distribution of the multi-plane optical converter.
[0032] This application introduces the GS algorithm and links it with the WFM algorithm. The WFM algorithm is used to update the phase distribution of each phase plane, and the GS algorithm is used to associate the light field of the Nth phase plane with the light field of the N+1th virtual phase plane as much as possible. After the total loop iteration calculation is completed, the phase distribution of each phase plane can be obtained. It can be seen that even if only the amplitude of the target light field is known but the phase is unknown, the phase distribution of each phase plane of the multi-plane optical converter can be obtained through iterative calculation.
[0033] For a better understanding, see Figure 1 As shown, when the incident light propagates forward, the forward propagation light field of the first phase plane is: The forward propagation optical field of the second phase plane is The forward propagation optical field of the third phase plane is And so on, the forward propagation light field of the Nth phase plane is The forward propagation light field of the N+1th virtual phase surface is .
[0034] When the target light propagates backward, the backward propagation light field of the first phase plane is: The backpropagating light field of the second phase plane is The backpropagating light field of the third phase plane is And so on, the backpropagating light field of the Nth phase plane is .
[0035] The target light field of the target plane is denoted as Its amplitude It is a known quantity, but its phase distribution is unknown.
[0036] See Figure 2 As shown, before starting, all relevant parameters of the multi-plane optical converter are known quantities, including the incident light wavelength to be used, the total number of phase plane layers N, the number of pixels in the phase plane, the pixel side length, the interlayer spacing between two adjacent phase plane layers, and the distance between the target plane and the Nth phase plane.
[0037] After starting, the optical field is initialized for all phase planes. The optical field initialization involves the incident light continuously propagating forward, and the forward propagation optical field from the first phase plane to the Nth phase plane is recorded. , , … The target light propagates continuously backward, and the backward propagation light field from the first phase plane to the Nth phase plane is recorded. , , … .
[0038] Then, the WFM loop iterative calculation is entered, using the wavefront matching algorithm to obtain the first output light field and the phase distribution of each phase plane at the first preset number of iterations, specifically including: 201: First, obtain the backward propagation light field of each phase plane when the target light propagates backward, and update the phase distribution of each phase plane except the last phase plane. Then, obtain the forward propagation light field of each phase plane when the input light propagates forward, and update the phase distribution of each phase plane except the last phase plane. This completes one WFM loop iteration calculation.
[0039] 202: By analogy, the WFM iterative calculation is completed for the first preset number of times to obtain the first output light field and the phase distribution of each phase plane.
[0040] In steps 201 and 202, the WFM iterative calculation of the N-layer phase plane is basically consistent with the general WFM algorithm. Both involve repeatedly passing the incident light and the target light during the cycle through the updated phase plane and propagating forward or backward by a phase plane interlayer spacing. The difference lies in the order: the general WFM algorithm calculates the forward propagation process first, then the backward propagation process, while this application reverses this order, calculating the backward propagation process first, then the forward propagation process. This is to align with the subsequent GS iterative calculation, where the input is... Post-output The order matches.
[0041] In step 201, the backward propagation light field of each phase plane during the backward propagation of the target light is obtained, and the phase distribution of each phase plane except the last phase plane is updated, including: 301: First, obtain the backpropagation light field of the phase plane when the target light propagates backward.
[0042] 302: Then, based on the backward propagating light field and the forward propagating light field of the phase plane, obtain the phase distribution, and use the phase distribution to update the phase plane.
[0043] 303: Finally, the target light continues to propagate backward through this phase plane.
[0044] Combination Figure 1 and Figure 2 Taking the first WFM loop iteration calculation as an example, the principle of steps 301 to 303 is explained as follows: Before the first WFM loop iteration calculation, the optical field has been initialized, and the forward propagation optical field of each phase plane has been obtained. , , … When the target light propagates backward, the backward propagation light field of the first phase plane, i.e., the Nth phase plane, is obtained. ,use and The phase distribution of the Nth phase plane can then be calculated using the following formula:
[0045] in, Let M be the phase distribution of the j-th phase plane, where j = 1, 2, ..., N, and M is the number of modes of the incident light. Let be the forward propagation light field of the incident light of the i-th mode propagating forward to the j-th phase plane. Let be the backpropagation light field of the target light of the i-th mode propagating backward to the j-th phase plane.
[0046] After updating the Nth phase using the calculated phase distribution of the Nth phase plane, the target light continues to propagate backward to the second phase plane, i.e., the (N-1)th phase plane, after passing through the Nth phase plane. Then, the backward propagation light field of the (N-1)th phase plane is obtained. Since the forward propagation light field of the (N-1)th phase plane was obtained during light field initialization, the phase distribution of the (N-1)th phase plane can be calculated, and the N-1th phase is updated. This process continues until the target light passes through the (N-1)th phase plane, i.e., the second phase plane, and continues to propagate backward to the Nth phase plane, i.e., the first phase plane, obtaining the backward propagation light field of the first phase plane. After completing the backward propagation calculation, the loop logic is described in [link to loop logic]. Figure 2 As shown.
[0047] After completing the backpropagation calculation, the forward propagation calculation is then performed.
[0048] In step 201, the forward propagation optical field of each phase plane during the forward propagation of the input light is obtained, and the phase distribution of each phase plane except the last phase plane is updated, including: 401: First, obtain the forward propagation light field of the phase plane when the incident light propagates forward.
[0049] 402: Then, based on the forward propagation light field and the backward propagation light field of the phase plane, obtain the phase distribution, and use the phase distribution to update the phase plane.
[0050] 403: Finally, the incident light continues to propagate forward through this phase plane.
[0051] The calculation logic of steps 401 to 403 above is similar to that of steps 301 to 303.
[0052] Combination Figure 1 and Figure 2 Taking the first WFM loop iteration calculation as an example, the principle of steps 401 to 403 is explained as follows: When the incident light propagates forward, the forward propagation light field of the first phase plane is obtained. Similarly, when the backward propagation calculation is completed, the backward propagation light field of the first phase plane is also obtained. Based on the phase calculation formula mentioned above, the phase distribution of the first phase plane during forward propagation can be calculated, and the first phase is updated. This process continues until the incident light passes through the (N-1)th phase plane and continues to propagate forward to the Nth phase plane, where the forward propagation light field of the Nth phase plane is obtained, thus completing the forward propagation calculation.
[0053] After completing one backpropagation calculation according to steps 301-303, a forward propagation calculation is then completed according to steps 401-403, thus completing one WFM iterative calculation cycle. This process continues until the first preset number of WFM iterative calculations are completed, yielding the first output light field and the phase distribution of each phase plane. This first output light field and the phase distribution of each phase plane are obtained from the last forward propagation calculation performed according to steps 401-403, and are also denoted as... The first preset number of times K1 can be set according to actual needs, and usually K1≥1.
[0054] After completing the above WFM iterative calculation, the GS iterative calculation is entered. Based on the first output light field and the target light field of the target plane, the GS algorithm is used to obtain the forward propagation light field of the virtual phase surface of the target plane when the first output light field propagates forward at the second preset number of iterations, including: 501: Obtain the first output light field at the first preset number of iterations of the WFM iterative calculation. The forward propagation light field of the virtual phase surface of the target plane when it continues to propagate forward after passing through the last phase plane. Maintain the forward propagation light field The phase distribution remains unchanged, and this is combined with the amplitude of the target light field. Constructing the first amplitude constrained light field ; Obtain the first amplitude constrained light field The backpropagating light field of the first phase plane, i.e., the Nth phase plane, during backward propagation. This completes one GS loop iteration calculation.
[0055] In step 501, see Figure 2 As shown, the first output light field After passing through the Nth phase plane, the light continues to propagate forward to the target plane, resulting in the forward propagation light field of the (N+1)th virtual phase plane. Then maintain the forward propagation light field. The phase distribution remains unchanged, with the amplitude of the target light field. Constructing the first amplitude constrained light field When it propagates backward, the backward propagation optical field of the Nth phase plane is obtained. .
[0056] 502: Determine whether the number of iterations calculated by the GS loop has reached the second preset number.
[0057] The second preset number of times K2 can be set according to actual needs, and usually K2≥1.
[0058] 503: If the number of iterations in the GS iterative calculation has not reached K2, maintain the first output light field at the first preset number of iterations in the WFM iterative calculation. The amplitude remains unchanged, and the light field is constrained by the first amplitude. Backward propagation optical field of the first phase plane during backward propagation The phase distribution is used to construct a second amplitude constrained optical field. Obtain the second amplitude-constrained optical field Forward propagation optical field of the virtual phase plane of the target plane during forward propagation Maintain the forward propagation light field The phase distribution remains unchanged, and combined with the amplitude of the target light field, a first amplitude-constrained light field is constructed. The back-propagating light field of the first phase plane when the first amplitude-constrained light field propagates backward is obtained, and one GS loop iteration calculation is completed. Then, return to step 502.
[0059] In step 503, see Figure 2As shown, it is necessary to reconstruct the constrained light field, that is, to maintain the first output light field of the WFM iterative calculation output after the first preset number of iterations. The amplitude remains constant, and the light field is constrained using the first amplitude. The backpropagating light field of the first phase plane, i.e., the Nth phase plane, during backward propagation. By constraining the phase distribution, a second amplitude constrained optical field is constructed. The second amplitude constrains the light field The first amplitude-constrained light field is constructed by referring to the first output light field, and the process is iterated repeatedly.
[0060] 504: If the number of iterations of the GS loop iteration calculation reaches K2, proceed to determine whether the total loop iteration calculation meets the termination condition.
[0061] Further, see Figure 2 As shown, the termination condition includes the total number of iterations in the loop iteration calculation reaching a third preset number, or the forward propagation of the virtual phase surface of the target plane when the first output light field propagates forward after the first preset number of iterations in the WFM loop iteration calculation. Target light field with the target plane They converge.
[0062] In other words, when the total loop iteration calculation reaches the third preset number of iterations, it ends and the phase distribution of each phase plane obtained by the last total loop iteration calculation is output, which is the phase distribution of each phase plane obtained by the last WFM loop iteration calculation.
[0063] Alternatively, compare the forward propagation of the virtual phase surface of the target plane with the first output light field at the first preset number of iterations calculated by WFM loop iteration. Target light field with the target plane If the two converge, for example, if the difference in their amplitudes is within a preset range, then the process ends and the phase distribution of each phase plane obtained from the last total loop iteration calculation is output.
[0064] The third preset number of times K3 can be set according to actual needs, and usually K3≥1.
[0065] Further, see Figure 2 As shown, if the total iterative calculation does not meet the termination condition, the total iterative calculation needs to continue. Specifically, the backward propagation of the first phase plane of the first amplitude-constrained light field during backward propagation is performed. The backward propagation light field of the first phase plane when the target light propagates backward is returned to the WFM loop iteration calculation, that is, the wavefront matching algorithm is continued to be used to obtain the first output light field and the phase distribution of each phase plane when the first preset number of iterations is obtained.
[0066] Furthermore, embodiments of this application also provide a phase distribution design apparatus for a multi-plane optical converter, the phase distribution design apparatus for a multi-plane optical converter comprising: The WFM algorithm processing unit is used to execute the wavefront matching algorithm, obtain the first output light field and the phase distribution of each phase plane when iterating for the first preset number of times. The first output light field is the forward propagation light field of the last phase plane when the incident light propagates forward.
[0067] The GS algorithm processing unit is used to execute the GS algorithm based on the first output light field and the target light field of the target plane to obtain the forward propagation light field of the virtual phase surface of the target plane when the first output light field propagates forward after a second preset number of iterations.
[0068] An iterative control unit is used to coordinate the WFM algorithm processing unit and the GS algorithm processing unit to perform overall iterative calculations.
[0069] The termination judgment unit is used to determine whether the total loop iteration calculation meets the termination condition.
[0070] A phase distribution output unit is used to output the phase distribution of each phase plane obtained by the last total loop iteration calculation if the total loop iteration calculation meets the termination condition.
[0071] Furthermore, this application embodiment also provides a multi-plane optical converter, which includes multiple phase planes, and the phase distribution of each phase plane is obtained by the phase distribution design method of the multi-plane optical converter described above.
[0072] Furthermore, the WFM algorithm processing unit is also used to obtain the forward propagation optical field of each phase plane during the forward propagation of the incident light at the time of optical field initialization.
[0073] Furthermore, the WFM algorithm processing unit obtains the first output light field and the phase distribution of each phase plane after the first preset number of iterations, including: firstly, obtaining the backward propagation light field of each phase plane when the target light propagates backward, and updating the phase distribution of each phase plane except the last phase plane; then, obtaining the forward propagation light field of each phase plane when the input light propagates forward, and updating the phase distribution of each phase plane except the last phase plane, thus completing one WFM loop iteration calculation; and so on, completing the first preset number of WFM loop iteration calculations to obtain the first output light field and the phase distribution of each phase plane.
[0074] Furthermore, the WFM algorithm processing unit acquires the backward propagation light field of each phase plane when the target light propagates backward, and updates the phase distribution of each phase plane except the last phase plane, including: first acquiring the backward propagation light field of the phase plane when the target light propagates backward; then acquiring the phase distribution based on the backward propagation light field and the forward propagation light field of the phase plane, and using the phase distribution to update the phase plane; finally, allowing the target light to continue to propagate backward through the phase plane.
[0075] Furthermore, the WFM algorithm processing unit acquires the forward propagation light field of each phase plane when the input light propagates forward, and updates the phase distribution of each phase plane except the last phase plane, including: first acquiring the forward propagation light field of the phase plane when the incident light propagates forward; then acquiring the phase distribution based on the forward propagation light field and the backward propagation light field of the phase plane, and using the phase distribution to update the phase plane; finally, allowing the incident light to continue propagating forward through the phase plane.
[0076] Furthermore, the GS algorithm processing unit, based on the first output light field and the target light field of the target plane, uses the GS algorithm to obtain the forward propagation light field of the virtual phase surface of the target plane when the first output light field propagates forward after a second preset number of iterations. This includes: obtaining the forward propagation light field of the virtual phase surface of the target plane when the first output light field continues to propagate forward after passing through the last phase plane; keeping the phase distribution of the forward propagation light field unchanged, and constructing a first amplitude-constrained light field by combining it with the amplitude of the target light field; obtaining the backward propagation light field of the first phase plane when the first amplitude-constrained light field propagates backward, thus completing the process. One GS loop iteration calculation is performed; it is determined whether the number of iterations of the GS loop iteration calculation has reached the second preset number; if not, the amplitude of the first output light field remains unchanged, and the second amplitude constraint light field is constructed by combining the phase distribution of the backward propagation light field of the first phase plane when the first amplitude constraint light field propagates backward, and the forward propagation light field of the virtual phase surface of the target plane when the second amplitude constraint light field propagates forward is obtained; the phase distribution of the forward propagation light field remains unchanged, and the first amplitude constraint light field is constructed by combining the amplitude of the target light field; if yes, the process proceeds to determine whether the total loop iteration calculation meets the termination condition.
[0077] Furthermore, the iterative control unit is also used to, if the total loop iteration calculation does not meet the termination condition, take the backward propagation light field of the first phase plane when the first amplitude constraint light field propagates backward as the backward propagation light field of the first phase plane when the target light propagates backward, and return to the wavefront matching algorithm to obtain the first output light field and the phase distribution of each layer of phase plane when iterating for the first preset number of times.
[0078] The functions of each module in the phase distribution design device for the multi-plane optical converter mentioned above correspond to the steps in the embodiment of the phase distribution design method for the multi-plane optical converter mentioned above, and their functions and implementation processes will not be described in detail here.
[0079] This application combines the GS (Gerchberg-Saxton) algorithm with the WFM algorithm. The proposed WFM-GS algorithm can quickly realize static single-input single-output, multi-input single-output, or multi-input multi-output custom optical field transformations, as well as dynamically adjustable custom optical field switching, without considering the phase of the target light.
[0080] One of the differences between the WFM-GS algorithm and the general WFM algorithm in terms of input and output settings is that it can map multiple input modes to one output mode, while the WFM algorithm cannot achieve this function when the phase of the target light field is unknown.
[0081] This application illustrates this point using a multi-input single-output static multiplane optical converter design as an example. Figure 3 In the application examples, this application uses an MPLC configuration with a wavelength of 1550nm, two phase planes, 600×600 pixels, a pixel side length of 8μm, a phase plane interlayer spacing of 100mm, and a distance of 100mm from the target plane to the second phase plane. The MPLC configuration of this application includes, but is not limited to, this. In this example, Gaussian light with a mode field diameter of 500μm is incident normally on the first phase plane from four different spatial locations, converging at the same position on the target plane; at this point, the mode field diameter is 500μm. Figure 3 Simulation results show that the output spot of the WFM algorithm does not match the target light field spot significantly, while the WFM-GS algorithm of this application can achieve the target function well. This indicates that the input and output function settings of the WFM-GS algorithm can be more flexible.
[0082] The WFM-GS algorithm can be used not only for the design of static MPLC devices but also for the design of dynamically adjustable mechanical MPLCs. The adjustability of dynamically adjustable mechanical MPLCs is achieved by mechanically displacing single or multiple phase planes of the MPLC device in three dimensions and rotating them in-plane at an angle of θ. Figure 4 As shown, the dynamically adjustable mechanical MPLC designed using the WFM-GS algorithm can be used for optical manipulation in single-input single-output, single-input multiple-output, multiple-input single-output, and multiple-input multiple-output configurations.
[0083] This is illustrated by taking the design of a dynamically adjustable mechanical multiplane optical converter with single input and multiple outputs as an example, which achieves the following: Figure 5 and Figure 6The mode switching and holographic switching functions are shown. The example MPLC is set with a wavelength of 1550nm, 2 phase planes, 600×600 pixels, 8μm pixel side length, 100mm phase plane layer spacing, 100mm distance from the target plane to the second phase plane, and 1500μm Gaussian light as input light. The adjustable MPLC settings of this application include, but are not limited to, these.
[0084] exist Figure 5 In the example, when the second-layer phase plane does not rotate, the output is in HG01 mode; when the second-layer phase plane rotates by 90°, the output is in HG10 mode. The mode field diameter for both HG modes is 800 μm. The mode switching function achievable in this application includes, but is not limited to, switching between HG modes.
[0085] exist Figure 6 In the example, when the second phase plane does not rotate, the output is the holographic letter "A"; when the rotation angle of the second phase plane is 90°, the output is the holographic letter "B".
[0086] Applications of tunable MPLC based on the WFM-GS algorithm include, but are not limited to, beam steering, mode conversion and switching, as well as holographic generation and switching.
[0087] The rotation angle, input, and output of the WFM-GS algorithm can be customized, which can greatly reduce the difficulty and cost of its actual implementation. It has great potential in application fields such as beam steering, mode conversion, holographic display, lidar, optical communication, and AI computing.
[0088] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.
[0089] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0090] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. A phase distribution design method for a multi-plane optical converter, characterized in that, It includes: Perform a total iterative calculation, which includes: - The wavefront matching algorithm is used to obtain the first output light field and the phase distribution of each phase plane when iterating for the first preset number of times. The first output light field is the forward propagation light field of the last phase plane when the incident light propagates forward. -Based on the first output light field and the target light field of the target plane, the GS algorithm is used to obtain the forward propagation light field of the virtual phase surface of the target plane when the first output light field propagates forward at the second preset number of iterations; Determine whether the total loop iteration calculation meets the termination condition. If the total loop iteration calculation meets the termination condition, output the phase distribution of each phase plane obtained by the last total loop iteration calculation.
2. The phase distribution design method for a multi-plane optical converter as described in claim 1, characterized in that: The termination conditions include the total number of iterations of the total loop iteration calculation reaching a third preset number, or the forward propagation light field of the virtual phase surface of the target plane and the target light field of the target plane converging when the first output light field propagates forward.
3. The phase distribution design method for a multi-plane optical converter as described in claim 1, characterized in that, Before performing the overall iterative calculation, the design method further includes: When the light field is initialized, the forward propagation light field of each phase plane is obtained during the forward propagation of the incident light.
4. The phase distribution design method for a multi-plane optical converter as described in claim 1, characterized in that, Obtain the first output light field and the phase distribution of each phase plane at the first preset iteration, including: First, obtain the backward propagation light field of each phase plane when the target light propagates backward, and update the phase distribution of each phase plane except the last phase plane. Then, obtain the forward propagation light field of each phase plane when the input light propagates forward, and update the phase distribution of each phase plane except the last phase plane. This completes one WFM loop iteration calculation. By repeating this process, the WFM iterative calculation is completed for the first preset number of times, resulting in the first output light field and the phase distribution of each phase plane.
5. The phase distribution design method for a multi-plane optical converter as described in claim 4, characterized in that, Acquire the backpropagation optical field of each phase plane during the backward propagation of the target light, and update the phase distribution of each phase plane except the last one, including: First, obtain the backpropagation light field of the phase plane when the target light propagates backward; Then, based on the backward propagating light field and the forward propagating light field of the phase plane, the phase distribution is obtained, and the phase plane is updated using the phase distribution; Finally, the target light passes through this phase plane and continues to propagate backward.
6. The phase distribution design method for a multi-plane optical converter as described in claim 4, characterized in that, Acquire the forward propagation optical field of each phase plane during the forward propagation of the input light, and update the phase distribution of each phase plane except the last phase plane, including: First, obtain the forward propagation optical field of the phase plane when the incident light propagates forward; Then, based on the forward propagation light field and the backward propagation light field of the phase plane, the phase distribution is obtained, and the phase plane is updated using the phase distribution. Finally, the incident light passes through this phase plane and continues to propagate forward.
7. The phase distribution design method for a multi-plane optical converter as described in claim 1, characterized in that, Based on the first output light field and the target light field of the target plane, the GS algorithm is used to obtain the forward propagation light field of the virtual phase surface of the target plane when the first output light field propagates forward at the second preset number of iterations, including: Obtain the forward propagation light field of the virtual phase plane of the target plane when the first output light field continues to propagate forward after passing through the last phase plane; keep the phase distribution of the forward propagation light field unchanged, and construct the first amplitude constraint light field in combination with the amplitude of the target light field; obtain the backward propagation light field of the first phase plane when the first amplitude constraint light field propagates backward, and complete one GS loop iteration calculation; Determine whether the number of iterations in the GS loop iteration calculation has reached the second preset number; If not, keep the amplitude of the first output light field unchanged, and combine it with the phase distribution of the backward propagation light field of the first phase plane when the first amplitude-constrained light field propagates backward, construct the second amplitude-constrained light field, and obtain the forward propagation light field of the virtual phase plane of the target plane when the second amplitude-constrained light field propagates forward; keep the phase distribution of the forward propagation light field unchanged, and combine it with the amplitude of the target light field to construct the first amplitude-constrained light field; If so, proceed to determine whether the total loop iteration calculation meets the termination condition.
8. The phase distribution design method for a multi-plane optical converter as described in claim 7, characterized in that: If the total loop iteration calculation does not meet the termination condition, the backward propagation light field of the first phase plane when the first amplitude constraint light field propagates backward is taken as the backward propagation light field of the first phase plane when the target light propagates backward, and the process returns to using the wavefront matching algorithm to obtain the first output light field and the phase distribution of each phase plane when iterating for the first preset number of times.
9. A phase distribution design device for a multi-plane optical converter, characterized in that, It includes: The WFM algorithm processing unit is used to execute the wavefront matching algorithm, obtain the first output light field and the phase distribution of each phase plane when iterating for the first preset number of times. The first output light field is the forward propagation light field of the last phase plane when the incident light propagates forward. The GS algorithm processing unit is used to execute the GS algorithm based on the first output light field and the target light field of the target plane to obtain the forward propagation light field of the virtual phase surface of the target plane when the first output light field propagates forward after a second preset number of iterations. An iterative control unit is used to coordinate the WFM algorithm processing unit and the GS algorithm processing unit to perform overall iterative calculations. The termination judgment unit is used to determine whether the total loop iteration calculation meets the termination condition. A phase distribution output unit is used to output the phase distribution of each phase plane obtained by the last total loop iteration calculation if the total loop iteration calculation meets the termination condition.
10. A multi-plane optical converter, characterized in that: It includes multiple phase planes, and the phase distribution of each phase plane is obtained by adopting the phase distribution design method of the multi-plane optical converter as described in any one of claims 1 to 8.