Apparatus and method for measuring topological charge of partially coherent vortex beams based on light intensity analysis

Abstract

The application provides a partial-coherence vortex beam topological charge measuring device and method based on light intensity analysis, which comprises the following steps: a solid laser emits laser light; a linear polarizer selects horizontal direction polarized light; a first lens focuses the polarized light; a frosted glass scatters the focused light to obtain incoherent light; a second lens collimates the partial-coherent light; a Gaussian filter shapes the collimated light to obtain a Gaussian Schell mode beam; a spatial light modulator modulates the Gaussian Schell mode beam to obtain a first Gaussian Schell mode vortex beam; a screening unit screens the first Gaussian Schell mode vortex beam to obtain a second Gaussian Schell mode vortex beam; a fifth lens focuses the second Gaussian Schell mode vortex beam to obtain a third Gaussian Schell mode vortex beam; and a charge-coupled device collects the light intensity diagram of the third Gaussian Schell mode vortex beam, and the size and sign of the topological charge are obtained according to the light intensity diagram. The size and sign of the topological charge of the Gaussian Schell mode vortex beam are analyzed through the light intensity diagram.

Description

Technical Field

[0001] This invention relates to the field of topological charge measurement technology, and specifically to a device and method for measuring the topological charge of a partially coherent vortex beam based on light intensity analysis. Background Technology

[0002] With the development of the information age, the demand for information from society and users is expanding rapidly. People's needs for communication services are no longer limited to text messages and calls, which poses new requirements and challenges to communication capacity and transmission rates. Currently, the communication field mostly uses multiplexing to expand communication capacity, which alleviates the contradiction of insufficient communication capacity to meet user needs to a certain extent, but its development has encountered a bottleneck. Therefore, it is particularly important to find a new technology to improve communication capacity. Among them, vortex beams with orbital angular momentum have become a hot topic in the field of optical communication in recent years.

[0003] Optical vortices with helical wavefronts and phase singularities have developed into an important branch of optics, known as singularity optics. The essential characteristic of vortex beams is that they carry orbital angular momentum. In recent years, advances in the research of vortex beams carrying orbital angular momentum have revolutionized beam applications, such as optical micromanipulation, high-capacity optical communication, and super-resolution imaging. Most current applications are based on known topological charges, making the measurement of these charges particularly important.

[0004] Currently, common methods for measuring topological charges fall into two main categories: one based on interferometry and diffraction techniques, and the other based on Fourier transform methods of vortex beam intensity. However, the first method often involves complex interferometric devices or unpredictable and complex diffraction patterns; the second method usually requires data processing and cannot be directly measured experimentally. Furthermore, both methods become ineffective as coherence decreases. In practical applications, beams often exist as partially coherent light, and most measurements are achieved through correlation function methods, requiring the acquisition of a sufficient number of instantaneous light intensities to obtain results, making real-time measurement impossible and resulting in high time costs; additionally, it cannot measure the sign of the topological charge; and it can only measure partially coherent vortex beams constructed using eigenmodes as fundamental modes. Summary of the Invention

[0005] In view of this, it is necessary to provide a device and method for measuring the topological charge of partially coherent vortex beams based on light intensity analysis, so as to solve the technical problem that existing technologies cannot measure the magnitude and sign of the topological charge of partially coherent vortex beams constructed with non-eigenmodes as fundamental modes in real time, thereby reducing the time cost of measurement.

[0006] On one hand, the present invention provides a device for measuring the topological charge of a partially coherent vortex beam based on light intensity analysis, comprising:

[0007] Solid-state laser, linear polarizer, first lens, frosted glass, second lens, Gaussian filter, spatial light modulator, screening unit, fifth lens, charge-coupled device and processing unit;

[0008] The solid-state laser is used to emit laser light;

[0009] The linear polarizer is used to select horizontally polarized light from the laser to obtain horizontally polarized light;

[0010] The first lens is used to focus the horizontally polarized light to obtain focused light;

[0011] The frosted glass is used to disperse the focused light to obtain incoherent light;

[0012] The second lens is used to collimate the partially coherent light obtained after the incoherent light has been transmitted, so as to obtain collimated light;

[0013] The Gaussian filter is used to shape the collimated light to obtain a Gaussian Sherman mode beam;

[0014] The spatial light modulator is used to modulate the Gaussian Scherrer mode beam to obtain a first Gaussian Scherrer mode vortex beam.

[0015] The filtering unit is used to filter the first Gaussian Scherrer mode vortex beam to obtain the second Gaussian Scherrer mode vortex beam.

[0016] The fifth lens is used to focus the second Gaussian Scherrer mode vortex beam to obtain the third Gaussian Scherrer mode vortex beam.

[0017] The charge-coupled device is used to acquire the intensity map of the third Gaussian Scherrer mode vortex beam, and to obtain the magnitude and sign of the topological charge based on the intensity map.

[0018] In some possible implementations, the filtering unit includes a third lens, an aperture stop, and a fourth lens;

[0019] The third lens is used to focus the first Gaussian Scherrer mode vortex beam to obtain a focused Gaussian Scherrer mode vortex beam.

[0020] The aperture is used to select the first-order diffraction spot according to the focused Gauss-Scher mode vortex beam to obtain a target focused Gauss-Scher mode vortex beam without other diffraction orders.

[0021] The focal plane of the fourth lens is the source surface of the Gauss-Scher mode vortex beam coupled with the cross phase, and is used to send the target focused Gauss-Scher mode vortex beam to the fifth lens to obtain the second Gauss-Scher mode vortex beam.

[0022] In some possible implementations, the charge-coupled device is used to obtain light intensity maps for different transmission distances based on its different positions and distances from the fifth lens.

[0023] Among some possible implementations, a first computer is also included;

[0024] The first computer generates a hologram containing vortex phase and cross phase, so that the spatial light modulator modulates the Gaussian Shear mode beam according to the hologram, loads the vortex phase and cross phase, and obtains a first Gaussian Shear mode vortex beam coupled with the cross phase.

[0025] Among some possible implementations, a second computer is also included;

[0026] The second computer is used to control the exposure time of the charge coupler and the acquisition frequency of the light intensity map.

[0027] Some possible implementations also include: a processing unit;

[0028] The processing unit is used to read the light intensity map and obtain the magnitude and sign of the topological charge by the number of dark stripes separated from the light intensity map and the direction of the dark stripe arrangement.

[0029] In some possible implementations, the incoherent light generated by the frosted glass becomes partially coherent light after a certain transmission distance, and then becomes completely coherent light after another certain transmission distance. The degree of coherence is adjusted by controlling the distance between the first lens and the frosted glass, the roughness of the frosted glass, and the focal length of the second lens.

[0030] On the other hand, the present invention also provides a method for measuring the topological charge of a partially coherent vortex beam based on intensity analysis, comprising:

[0031] Laser light is emitted by the solid-state laser, and horizontally polarized light is selected from the laser light by the linear polarizer to obtain horizontally polarized light.

[0032] The horizontally polarized light is focused by the first lens to obtain focused light, and the focused light is dispersed by the frosted glass to obtain incoherent light;

[0033] The incoherent light is collimated by the second lens to obtain partially coherent light after transmission, and then collimated light is shaped by the Gaussian filter to obtain a Gaussian Shear mode beam.

[0034] The Gaussian Sher mode beam is modulated by the spatial light modulator to obtain a first Gaussian Sher mode vortex beam. The first Gaussian Sher mode vortex beam is then filtered by the filtering unit to obtain a second Gaussian Sher mode vortex beam. The second Gaussian Sher mode vortex beam is then focused by the fifth lens to obtain a third Gaussian Sher mode vortex beam.

[0035] The intensity map of the third Gaussian Scherrer mode vortex beam is acquired by the charge-coupled device, and the magnitude and sign of the topological charge are obtained from the intensity map.

[0036] In some possible implementations, modulating the Gaussian Sherman mode beam using the spatial light modulator to obtain a first Gaussian Sherman mode vortex beam includes:

[0037] The Gauss-Sherman mode beam is modulated using a hologram containing vortex phase and cross phase generated by a first computer, and the vortex phase and cross phase are loaded to obtain a first Gauss-Sherman mode vortex beam coupled with the cross phase.

[0038] In some possible implementations, both the second Gauss-Scher mode vortex beam and the third Gauss-Scher mode vortex beam are Gauss-Scher mode vortex beams coupled with cross-phase.

[0039] The beneficial effects of the above embodiments are as follows: The partially coherent vortex beam topological charge measurement device based on light intensity analysis provided by this invention couples the vortex phase and cross phase with a Gaussian Sherman mode beam. Through light intensity diagrams, it is discovered that the cross phase can split the light intensity of the Gaussian Sherman mode vortex beam into several alternating bright and dark fringes. The number of dark fringes equals the magnitude of the topological charge, and the arrangement direction of the dark fringes can determine the sign (positive or negative) of the topological charge. Furthermore, by adjusting the cross phase, the magnitude and sign of the topological charge carried by the beam under test during transmission can be effectively measured, which greatly improves the flexibility of topological charge measurement. This invention has important applications in free-space optical communication.

[0040] This invention addresses the technical challenge in optical communication where environmental factors reduce beam coherence, hindering effective topological charge measurement. Existing methods require correlation functions to measure topological charge; this invention allows real-time measurement of topological charge magnitude and sign using intensity maps, reducing time costs. Furthermore, CP adjustment enables measurement of topological charge magnitude and sign during transmission, enhancing the flexibility of topological charge measurement. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 A schematic flowchart of an embodiment of the partially coherent vortex beam topological charge measurement method based on light intensity analysis provided by the present invention;

[0043] Figure 2 The theoretical result diagram of the light intensity distribution of the third Gaussian Scherrer mode vortex beam after cross-phase coupling at the focal plane, provided by the present invention;

[0044] Figure 3 The experimental results of the intensity distribution of the third Gaussian Sher mode vortex beam after cross-phase coupling at the focal plane are shown in the figure provided by the present invention.

[0045] Figure 4 The theoretical results of the intensity distribution of the third Gaussian Scherrer mode vortex beam after cross-phase coupling at different transmission distances provided by the present invention are shown in the figure.

[0046] Figure 5 The experimental results of the intensity distribution of the third Gaussian Scherrer mode vortex beam after cross-phase coupling at different transmission distances provided by the present invention are shown in the figure.

[0047] Figure 6 This is a schematic diagram of an embodiment of the partially coherent vortex beam topological charge measurement method based on light intensity analysis provided by the present invention.

[0048] The following are the labels in the diagram: 1. Solid-state laser, 2. Linear polarizer, 3. First lens, 4. Frosted glass, 5. Second lens, 6. Gaussian filter, 7. Spatial light modulator, 8. First computer, 9. Third lens, 10. Aperture, 11. Fourth lens, 12. Fifth lens, 13. Charge-coupled device, 14. Second computer. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0050] Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor systems and / or microcontroller systems.

[0051] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0052] This invention provides a device and method for measuring the topological charge of a partially coherent vortex beam based on light intensity analysis, which will be described below.

[0053] Figure 1 This is a schematic diagram of an embodiment of the partially coherent vortex beam topological charge measurement device based on light intensity analysis provided by the present invention, as shown below. Figure 1 As shown, the partially coherent vortex beam topological charge measurement device based on light intensity analysis includes: a solid-state laser 1, a linear polarizer 2, a first lens 3, a frosted glass 4, a second lens 5, a Gaussian filter 6, a spatial light modulator 7, a screening unit, a fifth lens 12, a charge-coupled device 13, and a processing unit.

[0054] The solid-state laser 1 is used to emit laser light;

[0055] The linear polarizer 2 is used to select horizontally polarized light from the laser to obtain horizontally polarized light;

[0056] The first lens 3 is used to focus the horizontally polarized light;

[0057] The frosted glass 4 is used to disperse the focused light to obtain incoherent light;

[0058] The second lens 5 is used to collimate the partially coherent light obtained after the incoherent light has been transmitted, so as to obtain collimated light;

[0059] The Gaussian filter 6 is used to shape the collimated light to obtain a Gaussian Sherman mode beam;

[0060] The spatial light modulator 7 is used to modulate the Gaussian Scherrer mode beam to obtain a first Gaussian Scherrer mode vortex beam.

[0061] The filtering unit is used to filter the first Gaussian Scherrer mode vortex beam to obtain the second Gaussian Scherrer mode vortex beam.

[0062] The fifth lens 12 is used to focus the second Gauss-Scher mode vortex beam to obtain the third Gauss-Scher mode vortex beam;

[0063] The charge-coupled device 13 is used to acquire the intensity map of the third Gaussian Scherrer mode vortex beam, and to obtain the magnitude and sign of the topological charge based on the intensity map.

[0064] Compared with existing technologies, the partial coherent vortex beam topological charge measurement device based on intensity analysis provided by this invention couples the vortex phase and cross phase with a Gaussian-Sherman mode beam. Intensity diagrams reveal that the cross phase splits the intensity of the Gaussian-Sherman mode vortex beam into several alternating bright and dark fringes. The number of dark fringes equals the magnitude of the topological charge, and the orientation of the dark fringes indicates the sign (positive or negative) of the topological charge. Furthermore, by adjusting the cross phase, the magnitude and sign of the topological charge carried by the beam under test during transmission can be effectively measured, greatly improving the flexibility of topological charge measurement. This invention has important applications in free-space optical communication.

[0065] This invention addresses the technical challenge in optical communication where environmental factors reduce beam coherence, hindering effective topological charge measurement. Existing methods require correlation functions to measure topological charge; this invention allows real-time measurement of topological charge magnitude and sign using intensity maps, reducing time costs. Furthermore, CP adjustment enables measurement of topological charge magnitude and sign during transmission, enhancing the flexibility of topological charge measurement.

[0066] It should be noted that the frosted glass 4 is a rotating frosted glass. This application can emit laser light using a solid-state laser 1, then select horizontally polarized light from the emitted laser using a linear polarizer 2, and then focus the laser light onto the frosted glass 4 using a first lens 3 to disperse it. The light exiting the surface of the frosted glass 4 is theoretically incoherent light. The light spot exiting the frosted glass 4 is transmitted to a second lens 5, which collimates the beam. A Gaussian filter 6 is placed close to the second lens 5, and the beam exiting the Gaussian filter 6 is a Gaussian Shear mode beam. The cross-spectral density expression of the Gaussian Shear mode beam at the source surface is shown in Formula 1:

[0067]

[0068] In the formula, W1(r1,r2) represents the expression for the cross spectral density of the Gaussian Sherman mode beam at the source surface, and r i (i = 1, 2) is the position vector at the beam source surface; ω and δ are the beam waist width and coherence width, respectively.

[0069] In some embodiments of the present invention, the incoherent light generated by the frosted glass 4 becomes partially coherent light after a certain transmission distance, and then becomes completely coherent light after another certain transmission distance. The degree of coherence is adjusted by controlling the distance between the first lens 3 and the frosted glass 4, the roughness of the frosted glass 4, and the focal length of the second lens 5.

[0070] In this embodiment of the invention, the level of coherence can be adjusted by adjusting the distance between the first lens 3 and the frosted glass 4, the roughness of the frosted glass 4, and the focal length of the second lens 5, so as to reduce the coherence of the topological charge of the vortex beam. In particular, by adjusting the distance between the lens and the frosted glass, the size of the light spot hitting the frosted glass can be changed. The larger the light spot, the more scattered it is hit, and the lower the coherence.

[0071] In some embodiments of the present invention, a first computer 8 is also included;

[0072] The first computer 8 generates a hologram containing vortex phase and cross phase, so that the spatial light modulator 7 modulates the Gaussian Shear mode beam according to the hologram, loads the vortex phase and cross phase, and obtains a first Gaussian Shear mode vortex beam coupled with the cross phase.

[0073] In a specific embodiment of the present invention, a hologram containing vortex phase and cross phase is copied onto the liquid crystal screen of the spatial light modulator 7. The generated Gaussian Sher mode beam hits the liquid crystal screen of the spatial light modulator and is reflected. The reflected beam is the first Gaussian Sher mode vortex beam coupled with the cross phase.

[0074] This invention modulates a light beam using a hologram to obtain the desired beam. The hologram is computer-generated and can be flexibly controlled as needed. Furthermore, since the light beam from the laser is a Gaussian beam, this invention requires loading information onto the hologram to obtain the desired beam.

[0075] In some embodiments of the present invention, the screening unit includes a third lens 9, an aperture 10, and a fourth lens 11;

[0076] The third lens 9 is used to focus the first Gaussian Scherrer mode vortex beam to obtain a focused Gaussian Scherrer mode vortex beam.

[0077] The aperture 10 is used to select the first-order diffraction spot according to the focused Gauss-Scher mode vortex beam to obtain a target focused Gauss-Scher mode beam without other diffraction orders.

[0078] The focal plane of the fourth lens is the source surface of the Gauss-Scher mode vortex beam coupled with the cross phase, and is used to send the target focused Gauss-Scher mode vortex beam to the fifth lens 12 to obtain the second Gauss-Scher mode vortex beam.

[0079] It should be noted that the first Gauss-Scher mode vortex beam is a Gauss-Scher mode vortex beam coupled with a cross phase, so the second Gauss-Scher mode vortex beam obtained through the first Gauss-Scher mode vortex beam is also a Gauss-Scher mode vortex beam coupled with a cross phase.

[0080] In a specific embodiment of the present invention, the 4f system consists of two equal-focal-length lenses, a third lens 9, a fourth lens 11, and an aperture stop 10. After obtaining the first Gaussian Sher mode beam with coupled cross-phase, the 4f system filters out the first-order diffraction spot from the first Gaussian Sher mode beam with coupled cross-phase to obtain the second Gaussian Sher mode beam with coupled cross-phase. Furthermore, different sizes of cross-phase factors can be loaded according to the level of coherence. In this example, ω = 1 mm, δ = 0.3 ω, δ = 0.5 ω, δ = 1 ω, and δ = 3 ω are selected, and the corresponding cross-phase factor value is u = 140 mm. -2 u = 50mm -2 u = 12mm -2 u = 4mm -2 The cross spectral density expression of the second Gaussian Sher mode beam source surface coupled with the cross phase is shown in Equation 2:

[0081]

[0082] In the formula, W2(r1,r2) represents the cross spectral density expression of the source surface of the second Gaussian Sher mode vortex beam with coupled cross phase, and r i (i=1,2) and These are the radial and angular coordinates of the second Gaussian Sher mode vortex beam source surface with coupled cross-phase; l is the topological charge, u is the cross-phase factor, exp(iux) i y i (i = 1, 2) is a cross-phase structure.

[0083] In some embodiments of the present invention, the fifth lens 12 is used to focus and transmit the second Gaussian vortex beam with the coupled cross phase to obtain a corresponding third Gaussian vortex beam.

[0084] It should be noted that the second Gauss-Scher mode vortex beam is a Gauss-Scher mode vortex beam coupled with a cross phase, so the third Gauss-Scher mode vortex beam obtained through the second Gauss-Scher mode vortex beam is also a Gauss-Scher mode vortex beam coupled with a cross phase.

[0085] In a specific embodiment of the present invention, the focal plane of the fourth lens 11 is the source plane of the Gaussian Sher mode vortex beam coupled through the cross phase. To facilitate the observation of the transmission characteristics of the second Gaussian Sher mode beam, a fifth lens 12 is added at the focal plane of the fourth lens 11, and then the beam is transmitted in free space, thereby forming a focusing transmission system. The focusing transmission system can study the transmission evolution characteristics of the beam at infinity in a limited experimental space. The cross spectral density expression of the second Gaussian Sher mode beam after passing through the focusing transmission system is shown in Formula 3.

[0086]

[0087] In the formula, W(ρ1,ρ2) represents the cross spectral density expression of the second Gaussian Sher mode beam after passing through the focusing and transmission system, and ρ i (i = 1, 2) is the position vector of the observation surface, A = 1 - z / f, B = z, C = -1 / f, D = 1 is the matrix expression of the focusing transmission system, which represents the process of the light beam passing through the lens and then being transmitted to point z. In this embodiment of the invention, k = 2π / λ is the wave number, λ = 532nm is the wavelength, and the focal length f = 400mm.

[0088] In some embodiments of the present invention, the charge-coupled device 13 is used to obtain light intensity maps with different transmission distances based on its different positions and distances from the fifth lens 12.

[0089] In a specific embodiment of the present invention, the distance between the charge coupler and the fifth lens 12 can be controlled by adjusting the position of the charge coupler, thereby obtaining light intensity maps at different transmission distances.

[0090] In some embodiments of the present invention, a second computer 14 is also included;

[0091] The second computer 14 is used to control the exposure time of the charge coupler and the acquisition frequency of the light intensity map.

[0092] In a specific embodiment of the present invention, the exposure time of the charge coupler and the acquisition frequency of the light intensity map can also be controlled by the second computer 14 to obtain light intensity maps at different transmission distances.

[0093] In some embodiments of the present invention, a processing unit is also included;

[0094] The processing unit is used to read the light intensity map and obtain the magnitude and sign of the topological charge by the number of dark stripes separated from the light intensity map and the direction of the dark stripe arrangement.

[0095] In a specific embodiment of the present invention, the light intensity images captured by the charge-coupled device 13 can be named in sequence, and then the light intensity images can be imported into Matlab for processing. At this time, the pixel size set in Matlab is consistent with the pixel size of the charge-coupled device 13, and it is necessary to ensure that the number of pixels occupied by the light intensity image is as large as possible, so as to ensure the clarity of the acquired light intensity image.

[0096] Figure 2 The image shows the theoretical intensity distribution of the third Gaussian Sher mode vortex beam at the focal plane after cross-phase coupling, as shown in the figure. Figure 2 As shown, after the third Gaussian Sher mode vortex beam couples with cross phase, the intensity distribution undergoes a mode conversion, transforming into a pattern of alternating bright and dark fringes. Furthermore, the number of dark fringes between two bright spots is equal to the magnitude of the topological charge. For example... Figure 2 In the (b1-b4) topological charge l = 3, regardless of the coherence level, the number of dark fringes distributed between the two bright spots is always equal to 3 when different cross phases are adjusted. Therefore, the magnitude of the topological charge can be obtained, and the measurement of the topological charge magnitude is realized. Furthermore, when the topological charge l = -3, the arrangement direction of the dark fringes will rotate by 90 degrees, and the sign of the topological charge can be obtained, thus realizing the resolution of the topological charge sign. Therefore, the embodiment of the present invention realizes the real-time synchronous measurement of the magnitude and sign of the topological charge of a partially coherent vortex beam constructed by using a non-eigenmode as the fundamental mode, such as a Gaussian Sher mode vortex beam, solely through the intensity distribution.

[0097] Figure 3 The figure shows the experimental results of the intensity distribution of the third Gaussian Sher mode vortex beam at the focal plane after cross-phase coupling, as shown in the figure. Figure 3 As shown, for example Figure 3 In the (f1-f4) topological charge l=3, after cross-phase coupling, the third Gaussian Shear mode vortex beam will split into a row of alternating bright and dark fringes at the focal plane, and the number of dark fringes between the upper and lower bright spots will always be equal to 3. Topological charge l=-3 Figure 3 (h1-h4), compared to the topological charge l=3, the distribution direction of the dark fringes rotates by 90 degrees. Therefore, the magnitude and sign of the topological charge can be clearly identified, and the experimental results are consistent with... Figure 2 The results are consistent with the theoretical results, proving the accuracy of the proposed method implementation.

[0098] Figure 4 This is a theoretical diagram showing the intensity distribution of a third Gaussian Sher mode vortex beam after cross-phase coupling at different propagation distances. The coherence is δ = 1ω. At different distances, the magnitude and sign of the topological charge can be identified by adjusting the cross-phase. Furthermore, the intensity rotates during propagation, and the direction of rotation depends on the sign of the topological charge. For example... Figure 4In the topological charge l = ±3, during the transmission process from the far focal plane (z = 0.3f) to the focal plane (z = f), the number of dark fringes between the two bright spots is equal to 3. Therefore, the magnitude of the topological charge can be determined, realizing the measurement of the magnitude of the topological charge. When the topological charge is positive, the light intensity rotates counterclockwise during transmission, and conversely, the light intensity rotates clockwise. The sign of the topological charge can be determined, realizing the resolution of the sign of the topological charge. Therefore, the detection plane of this embodiment is no longer limited to the focal plane, which improves the flexibility of our detection.

[0099] Figure 5 This is an experimental result showing the intensity distribution of the third Gaussian Sher mode vortex beam at different propagation distances after cross-phase coupling; coherence δ = 1ω, experimental results and... Figure 4 The results are consistent with the theoretical results, proving the accuracy of the proposed method implementation.

[0100] This embodiment also provides a method for measuring the topological charge of a partially coherent vortex beam based on intensity analysis, using any of the above-described technical solutions, such as... Figure 6 As shown, the method includes:

[0101] Step S101: Laser light is emitted by the solid-state laser 1, and the horizontally polarized light is selected by the linear polarizer 2 to obtain horizontally polarized light;

[0102] Step S102: The horizontally polarized light is focused by the first lens 3 to obtain focused light, and the focused light is dispersed by the frosted glass 4 to obtain incoherent light;

[0103] Step S103: The incoherent light is collimated by the second lens 5 to obtain the partially coherent light after transmission, and the collimated light is shaped by the Gaussian filter 6 to obtain a Gaussian Shear mode beam.

[0104] Step S104: Modulate the Gaussian Sher mode beam using the spatial light modulator 7 to obtain a first Gaussian Sher mode vortex beam; filter the first Gaussian Sher mode vortex beam using the filtering unit to obtain a second Gaussian Sher mode vortex beam; focus the second Gaussian Sher mode vortex beam using the fifth lens 12 to obtain a third Gaussian Sher mode vortex beam.

[0105] Step S105: The intensity map of the third Gaussian Scherrer mode vortex beam is acquired by the charge-coupled device 13, and the magnitude and sign of the topological charge are obtained based on the intensity map.

[0106] This invention also provides an electronic device, comprising:

[0107] It includes a processor, a memory, and a computer program stored in the memory and capable of running on the processor. When executed by the processor, the computer program implements the various processes of the above-described embodiment of the partially coherent vortex beam topological charge measurement method based on light intensity analysis and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0108] This invention also provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the various processes of the above-described embodiment of the partially coherent vortex beam topological charge measurement method based on light intensity analysis, and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0109] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware (such as a processor, controller, etc.), and the computer program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0110] The foregoing has provided a detailed description of the device and method for measuring the topological charge of a partially coherent vortex beam based on light intensity analysis provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A device for measuring the topological charge of a partially coherent vortex beam based on intensity analysis, characterized in that, include: Solid-state laser, linear polarizer, first lens, frosted glass, second lens, Gaussian filter, spatial light modulator, screening unit, fifth lens, charge-coupled device and processing unit; The solid-state laser is used to emit laser light; The linear polarizer is used to select horizontally polarized light from the laser to obtain horizontally polarized light; The first lens is used to focus the horizontally polarized light to obtain focused light; The frosted glass is used to disperse the focused light to obtain incoherent light; The second lens is used to collimate the partially coherent light obtained after the incoherent light has been transmitted, so as to obtain collimated light; The Gaussian filter is used to shape the collimated light to obtain a Gaussian Sherman mode beam; The spatial light modulator is used to modulate the Gaussian Scherrer mode beam to obtain a first Gaussian Scherrer mode vortex beam. The filtering unit is used to filter the first Gaussian Scherrer mode vortex beam to obtain the second Gaussian Scherrer mode vortex beam. The fifth lens is used to focus the second Gaussian Scherrer mode vortex beam to obtain the third Gaussian Scherrer mode vortex beam. The charge-coupled device is used to acquire the intensity map of the third Gaussian Scherrer mode vortex beam, and to obtain the magnitude and sign of the topological charge based on the intensity map. The processing unit is used to read the light intensity map and obtain the magnitude and sign of the topological charge from the number of dark stripes separated from the light intensity map and the direction of the dark stripe arrangement. The filtering unit includes a third lens, an aperture, and a fourth lens; The third lens is used to focus the first Gaussian Scherrer mode vortex beam to obtain a focused Gaussian Scherrer mode vortex beam. The aperture is used to select the first-order diffraction spot according to the focused Gauss-Scher mode vortex beam to obtain a target focused Gauss-Scher mode vortex beam without other diffraction orders. The focal plane of the fourth lens is the source surface of the Gauss-Scher mode vortex beam coupled with the cross phase, which is used to send the target focused Gauss-Scher mode vortex beam to the fifth lens to obtain the second Gauss-Scher mode vortex beam. It also includes: the first computer; The first computer generates a hologram containing vortex phase and cross phase, so that the spatial light modulator modulates the Gaussian Shear mode beam according to the hologram, loads the vortex phase and cross phase, and obtains a first Gaussian Shear mode vortex beam coupled with the cross phase. It also includes: a second computer; The second computer is used to control the exposure time of the charge coupler and the acquisition frequency of the light intensity map.

2. The device for measuring the topological charge of a partially coherent vortex beam based on intensity analysis according to claim 1, characterized in that, The charge-coupled device is used to obtain light intensity maps for different transmission distances based on its different positions and distances from the fifth lens.

3. The device for measuring the topological charge of a partially coherent vortex beam based on intensity analysis according to claim 1, characterized in that, The incoherent light generated by the frosted glass becomes partially coherent light after a certain transmission distance, and then becomes completely coherent light after another certain transmission distance. The degree of coherence is adjusted by controlling the distance between the first lens and the frosted glass, the roughness of the frosted glass, and the focal length of the second lens.

4. A method for measuring the topological charge of a partially coherent vortex beam based on intensity analysis, employing the topological charge measurement device for a partially coherent vortex beam based on intensity analysis as described in any one of claims 1-3, characterized in that... The method includes: Laser light is emitted by the solid-state laser, and horizontally polarized light is selected from the laser light by the linear polarizer to obtain horizontally polarized light. The horizontally polarized light is focused by the first lens to obtain focused light, and the focused light is dispersed by the frosted glass to obtain incoherent light; The incoherent light is collimated by the second lens to obtain partially coherent light after transmission, and then collimated light is shaped by the Gaussian filter to obtain a Gaussian Shear mode beam. The Gaussian Sher mode beam is modulated by the spatial light modulator to obtain a first Gaussian Sher mode vortex beam. The first Gaussian Sher mode vortex beam is then filtered by the filtering unit to obtain a second Gaussian Sher mode vortex beam. The second Gaussian Sher mode vortex beam is then focused by the fifth lens to obtain a third Gaussian Sher mode vortex beam. The intensity map of the third Gaussian Scherrer mode vortex beam is acquired by the charge-coupled device, and the magnitude and sign of the topological charge are obtained from the intensity map.

5. The method for measuring the topological charge of a partially coherent vortex beam based on intensity analysis according to claim 4, characterized in that, The step of modulating the Gaussian Sherman mode beam using the spatial light modulator to obtain a first Gaussian Sherman mode vortex beam includes: The Gauss-Sherman mode beam is modulated using a hologram containing vortex phase and cross phase generated by a first computer, and the vortex phase and cross phase are loaded to obtain a first Gauss-Sherman mode vortex beam coupled with the cross phase.

6. The method for measuring the topological charge of a partially coherent vortex beam based on intensity analysis according to claim 5, characterized in that, The second Gauss-Scher mode vortex beam and the third Gauss-Scher mode vortex beam are both Gauss-Scher mode vortex beams coupled with cross phases.

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