Method and system for generating partially coherent light field based on multi-core optical fiber

Abstract

The invention discloses a method and a system for generating a partially coherent light field based on a multi-core optical fiber. The method comprises the following steps: determining a plurality of electric field modes according to a cross spectrum density function of a target partially coherent light field and generating a hologram; measuring phase distortion among fiber cores of the multi-core optical fiber and generating a compensation diagram; after the two laser beams are superposed into a synthetic hologram, wavefront modulation is carried out on incident laser; and coupling the modulated light into a multi-core optical fiber and outputting a target light field. The system correspondingly comprises a mode and compensation diagram generation module, a hologram synthesis module, a wavefront modulation module and a coupling transmission module. The multi-core optical fiber is utilized to realize system miniaturization and strong environmental adaptability, a hologram sequence is combined with phase compensation, various partially coherent light with specific spatial coherent structures can be flexibly generated and transmitted, and the problems that in the prior art, regulation and control are not flexible, and application in a zigzag narrow environment is difficult are solved.

Description

Technical Field

[0001] This invention relates to the field of optical field manipulation technology, and in particular to a method and system for generating partially coherent optical fields based on multi-core optical fibers. Background Technology

[0002] Partially coherent light fields, existing between fully coherent and fully incoherent light, demonstrate significant application value in fields such as free-space optical communication, biomedical imaging, laser material processing, and adaptive optics. To generate such light fields, various technical approaches have been developed, broadly categorized into intracavity and extracavity methods. Intracavity methods primarily include mode selection methods, which generate partially coherent Gaussian-Sherlock modes by controlling modes within the laser cavity, and methods that directly generate partially coherent light within the cavity based on multimode fiber. Extracavity methods are more diverse. Pure digital holography generates light fields with specific spatial correlation structures by loading designed holograms onto a spatial light modulator; dynamic scatterer methods utilize random media such as rotating frosted glass to scatter coherent light, reducing its spatial coherence. In recent years, with the development of integrated photonics, a partially coherent light generation scheme based on metasurfaces has emerged. It utilizes subwavelength structure arrays to achieve flexible control of the amplitude or phase of the light field, thereby improving the compactness of the system. Another scheme is an ultrafast electro-optic modulation scheme based on lithium niobate crystals, which can dynamically control the coherent structure of the light field by applying an electrical signal.

[0003] Despite these limitations, existing technologies still have several significant limitations. Intracavity mode selection methods typically only generate Gaussian-Sherlock mode-like optical fields, making it difficult to flexibly control their spatial coherence structure. While multimode fiber methods have relatively simple structures, their mode controllability is poor, making it impossible to generate complex structured optical fields on demand. Extracavity methods, such as digital holography and dynamic scattering body schemes, often rely on complex external optical paths, resulting in large system sizes, cumbersome debugging, and difficulty in meeting the requirements of integrated and miniaturized applications. Moreover, most of these methods cannot achieve real-time dynamic reconstruction of the optical field. Emerging metasurface technologies have improved integration, but their degrees of freedom in control and flexibility in mode generation remain insufficient. Furthermore, modulation schemes based on lithium niobate are currently mostly limited to one-dimensional coherence control, making it difficult to arbitrarily construct two-dimensional spatial correlation structures. More importantly, all of the above existing schemes are designed for free-space optical paths and are not applicable to tortuous, narrow, non-free-space environments, such as imaging and detection scenarios in human cavities, industrial equipment interiors, or complex microstructures. This significantly limits the practical application scope of some coherent optical technologies. Therefore, developing a partially coherent light generation method and system that can adapt to complex environments and has both flexible control capabilities and system compactness has become a technical problem to be solved in this field. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problems of insufficient spatial coherence structure control flexibility, low system integration and difficulty in real-time dynamic reconstruction in some coherent light field generation methods in the prior art, as well as the inability to adapt to non-free space environments such as tortuous and narrow spaces.

[0005] To address the aforementioned technical problems, this invention provides a method for generating a partially coherent optical field based on a multi-core optical fiber, comprising: Based on the cross-spectral density function of the coherent optical field of the target part, determine the corresponding multiple electric field modes, and generate the corresponding hologram based on the multiple electric field modes; For a multi-core optical fiber used for optical field transmission, the phase distortion between each core of the multi-core optical fiber is measured, and a phase compensation map is generated based on the measurement results. The hologram and the phase compensation image are superimposed to generate a composite hologram; The incident laser is wavefront modulated using the synthesized hologram; The modulated laser is coupled to the multi-core optical fiber, and the target partial coherent optical field is output through the multi-core optical fiber.

[0006] In one embodiment of the present invention, the method for measuring the phase distortion between the cores of the multi-core optical fiber and generating a phase compensation map based on the measurement results is as follows: After a plane wave is incident on the multi-core optical fiber and transmitted, the output optical field is obtained. The output light field is interfered with the reference light to obtain an off-axis digital hologram; The off-axis digital hologram is processed to reconstruct the actual phase distribution of the far end face of the multi-core optical fiber; the phase conjugate of the actual phase distribution is calculated as a phase compensation map to compensate for the phase distortion between the cores of the multi-core optical fiber.

[0007] In one embodiment of the present invention, after generating the phase compensation map, the method further includes: establishing a coordinate mapping relationship from the target imaging plane to the hologram loading plane; transforming the phase compensation map according to the coordinate mapping relationship and superimposing it with a preset focusing phase; and iteratively optimizing the parameters of the coordinate mapping relationship so that the beam transmitted through the multi-core optical fiber forms a focused spot.

[0008] In one embodiment of the present invention, the method for wavefront modulation of incident laser using the synthetic hologram is as follows: spatially modulating the wavefront phase of the incident laser based on the synthetic hologram; spatially filtering the multi-level diffraction field generated after modulation, and extracting a preset specific diffraction order component from it to obtain the modulated laser.

[0009] In one embodiment of the present invention, the method for calculating the holograms of multiple electric field modes based on the cross-spectral density function of the coherent optical field of the target portion is as follows: the holograms of multiple electric field modes are generated based on the mode decomposition of the cross-spectral density function, wherein the cross-spectral density function is expressed as: , in, The cross spectral density function is used to describe the light field at any two points in space. and Statistical correlation at the location; Indicates the first An instantaneous scalar field with random fluctuations; For the first The normalized weighting coefficients of each electric field mode satisfy the following... ; This represents the total number of electric field modes involved in the superposition.

[0010] In one embodiment of the present invention, the target partially coherent optical field includes a Hermitian-Gaussian correlated Shear mode partially coherent optical field, and the electric field mode is: , in, Indicates the first A random fluctuation of instantaneous scalar electric field mode; Spatial domain coordinates; , For the light field along the frequency domain and Coordinates of direction; , respectively along and The beam width in the direction; , The order of the Hermitian polynomial determines the spatial distribution characteristics of the beam. It is a function generated by a zero-mean random process.

[0011] In one embodiment of the present invention, the target partially coherent optical field includes a Laguerre-Gaussian correlated Sher mode partially coherent optical field, with the electric field mode being: , in, Indicates the first A random fluctuation of instantaneous scalar electric field mode; Spatial domain coordinates; Represents the vector coordinates of the light field in the spatial frequency domain; It represents the width of the light beam in the spatial domain and determines the scale of the lateral distribution of the light field; The order of the Laguerre polynomial controls the complexity of the ring structure in which the light field is distributed in the spatial frequency domain; It is a function generated by a random process.

[0012] The present invention also provides a partially coherent optical field generation system based on multi-core optical fiber, comprising: The mode and compensation map generation module is used to determine multiple electric field modes based on the cross spectral density function of the coherent optical field of the target part, and generate corresponding holograms based on the multiple electric field modes; for multi-core optical fibers used for optical field transmission, the module measures the phase distortion between each core of the multi-core optical fiber, and generates a phase compensation map based on the measurement results. A hologram synthesis module is used to superimpose the hologram and the phase compensation map to generate a synthesized hologram; A wavefront modulation module is used to perform wavefront modulation on the incident laser using the synthesized hologram; The coupling and transmission module is used to couple the modulated laser to the multi-core optical fiber and output the target partial coherent optical field through the multi-core optical fiber.

[0013] In one embodiment of the present invention, the partially coherent optical field generation system based on multi-core optical fiber further includes an interferometric measurement unit for measuring the phase distortion of the multi-core optical fiber; the interferometric measurement unit includes a reference optical path and a detector, the reference optical path is used to provide reference light for interference with the output optical field, and the detector is used to record the interference pattern.

[0014] In one embodiment of the present invention, the wavefront modulation module includes a spatial light modulator for loading the synthetic hologram and performing wavefront phase modulation on the incident laser. The coupling optical components in the coupling and transmission module include a 4f system consisting of a lens and an objective lens, used to couple the modulated laser to the multi-core optical fiber.

[0015] The technical solution of the present invention has the following advantages compared with the prior art: This invention combines flexible optical field manipulation with flexible multi-core optical fibers, solving the problems of large volume and inability to enter narrow environments in traditional free-space optical paths. It achieves system miniaturization and strong environmental adaptability, expanding its application potential in fields such as in vivo imaging and industrial endoscopy. By loading holographic sequences and combining them with precise phase compensation, partially coherent light with various special structures such as Hermitian-Gaussian and Laguerre-Gaussian can be freely generated, overcoming the limitation of single manipulation modes in existing methods. Furthermore, the digital phase conjugation and iterative optimization techniques employed effectively correct phase distortion between fiber cores, ensuring the quality of the output optical field and system stability. This invention provides a compact, reliable, and flexible solution for the generation and application of structurally partially coherent light. Attached Figure Description

[0016] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0017] Figure 1 This is a flowchart illustrating the method for generating a partially coherent optical field based on a multi-core optical fiber provided in this embodiment of the invention. Figure 2 This is a schematic diagram illustrating the principle of using multi-core optical fibers to control structured light and measure the angular velocity of an object in an embodiment of the present invention. Figure 3 This is a schematic diagram of the core fiber phase iterative optimization compensation process in an embodiment of the present invention; Figure 4 This is a schematic diagram of the experimental results of generating Hermitian-Gaussian correlated partially coherent optical fields using multi-core optical fibers in an embodiment of the present invention. Figure 5 This is a schematic diagram of the experimental results of generating a Laguerre-Gaussian correlated partial coherent optical field using a multi-core optical fiber in an embodiment of the present invention.

[0018] Explanation of reference numerals in the accompanying drawings: 1. Laser; 2. Beam expander; 3. First beam splitter; 4. Spatial light modulator; 5. First lens; 6. Aperture; 7. Second lens; 8. Third lens; 9. First objective lens; 10. Multi-core optical fiber; 11. Second objective lens; 12. Fourth lens; 13. Second beam splitter; 14. Camera; 15. Mirror. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0020] Example 1: like Figure 1 As shown, the present invention provides a method for generating a partially coherent optical field based on a multi-core optical fiber, comprising: Based on the cross-spectral density function of the coherent optical field of the target part, multiple electric field modes are determined, and corresponding holograms are generated based on the multiple electric field modes; for the multi-core optical fiber used for optical field transmission, the phase distortion between each core of the multi-core optical fiber is measured, and a phase compensation map is generated based on the measurement results. The hologram and the phase compensation image are superimposed to generate a composite hologram; The incident laser is wavefront modulated using the synthesized hologram; The modulated laser is coupled to the multi-core optical fiber, and the target partial coherent optical field is output through the multi-core optical fiber.

[0021] This invention determines multiple electric field modes required for the target optical field through a cross-spectral density function and generates corresponding holograms. It measures the inter-core phase distortion of a multi-core optical fiber and generates a compensation map. These two maps are then superimposed to obtain a synthetic hologram, which is used to wavefront modulate the incident laser. The modulated light is coupled into the multi-core optical fiber to output the target partially coherent optical field. This method for generating a partially coherent optical field based on multi-core optical fibers not only allows for flexible control of the spatial coherence structure of the optical field but also utilizes multi-core optical fibers to achieve system miniaturization and strong environmental adaptability. It is particularly suitable for scenarios where traditional free-space optical paths cannot operate directly, such as those involving tortuous or narrow paths, thus expanding the application potential of partially coherent optical technology.

[0022] like Figure 2 As shown, the method for generating a partially coherent optical field based on a multi-core optical fiber 10 of the present invention first requires calculating and generating a corresponding hologram based on the cross-spectral density function of the target partially coherent optical field. For example, hologram design is performed for specific types such as Hermit-Gaussian correlated Sher mode partially coherent optical fields or Laguerre-Gaussian correlated Sher mode partially coherent optical fields. Secondly, the phase compensation information required by the random optical path difference between the cores of the multi-core optical fiber 10 is obtained through interferometry, and this phase compensation map is superimposed with the pre-calculated target optical field hologram to synthesize the final hologram used for loading. This synthesized hologram is loaded onto the spatial light modulator 4.

[0023] In the optical path implementation, the laser emitted from laser 1 is first collimated by beam expander 2. Then, the collimated beam is split into two paths by first beam splitter 3: one path serves as the signal light, incident on the surface of spatial light modulator 4 with a pre-loaded composite hologram for wavefront modulation; the other path can be used as reference light for subsequent interferometry if needed. The light field generated after modulation by spatial light modulator 4 contains multiple diffraction components, which are sequentially filtered through a 4f filter system consisting of first lens 5, second lens 7, and an aperture 6 placed at the confocal surface of the two lenses, thereby precisely filtering out the required first-order diffraction order. The filtered modulated light is further collimated or reduced by third lens 8 and efficiently coupled into the input end of multi-core fiber 10 by first objective lens 9. After transmission through multi-core fiber 10, the optical signal exits from its far end. The exited light field is collected by second objective lens 11 and then collected and collimated by fourth lens 12. To facilitate observation and recording, the optical path can be split by the second beam splitter 13, or it can be combined with the reference light guided by the reflector 15 for interference. Finally, the camera 14 receives and records the generated coherent light field of the target part, thus completing the entire process of light field generation, transmission and detection.

[0024] Specifically, to generate a partially coherent light field with the desired coherence characteristics, its statistical description method must first be determined. When characterizing a partially coherent light field, the cross-spectral density function is typically used to describe the statistical properties of the light field, i.e., the correlation of the light field between two spatial points in the frequency domain. When considering only quasi-monochromatic light, the spatial coherence characteristics of the partially coherent light field are usually expressed using the cross-spectral density function. To describe it, it is defined as the light field at two points in space. and Cross-correlation of complex amplitudes: ,in, It represents the instantaneous scalar complex amplitude of the light field.

[0025] To achieve flexible construction of the target light field, this invention adopts the principle of incoherent superposition of modes, expressing the cross spectral density function as several randomly fluctuating electric field modes. The incoherent superposition of the cross-spectral density is expressed as: , in, Indicates the first An instantaneous scalar field with random fluctuations; For the first The normalized weighting coefficients of each electric field mode satisfy the following... ; This represents the total number of electric field modes involved in the superposition.

[0026] The generation of the target coherent optical field is transformed into sequentially or proportionally loading different electric field modes onto the spatial light modulator 4. Hologram.

[0027] For example, for Gaussian Shermodal partially coherent light, it can be written in the following form: , in, The function is controlled by a Gaussian random process with zero mean, and its autocorrelation is a Gaussian function. Let be the waist radius of the Gaussian Sher mode beam.

[0028] The hologram loaded by the spatial light modulator 4 each time is mainly composed of the corresponding electric field mode. Encode and generate.

[0029] During the dynamic generation process of the entire venue, each [item]... Encoded holograms in probability The signals are sequentially and rapidly loaded onto spatial light modulator 4, achieving the statistical characteristics described by the cross-spectral density function through time averaging. Specifically, the total number of modes participating in the superposition... At this point, the system degenerates into generating a fully coherent optical field. For partially coherent Shermode optical fields with special structures such as Hermi-Gaussian or Laguerre-Gaussian correlations, their electric field modes have corresponding special functional forms, and the generation of holograms needs to be designed based on their specific expressions.

[0030] Phase distortion measurement and compensation were performed on the selected multi-core fiber 10. To overcome the random optical path difference between fiber cores introduced by the fiber manufacturing process, fine phase compensation correction was required first. For example... Figure 3 As shown, the specific steps are as follows: First, without loading any modulation pattern onto the spatial light modulator 4, the plane wave emitted from the laser 1, after beam expansion and collimation, is coupled into the input end of the multi-core fiber 10 through an objective lens. After the light is transmitted through the multi-core fiber 10, another objective lens is used at its output end to collect and export the light field. At this time, a camera 14 is placed in the output optical path to record the light intensity distribution. Simultaneously, a laser beam is split from the optical path before the spatial light modulator 4 as a reference beam, which interferes with the target light field emitted from the multi-core fiber 10. The camera 14 records the off-axis digital hologram formed after the interference of the two beams.

[0031] By performing a Fourier transform on the obtained off-axis digital hologram and accurately extracting its first-order diffraction term, the actual phase distribution of the far-end exit surface of the multi-core fiber 10 can be digitally reconstructed. Based on this reconstructed actual phase distribution, its phase conjugate value is calculated, which constitutes the initial compensation phase map used to compensate for random phase differences between fiber cores.

[0032] Subsequently, a precise coordinate mapping relationship needs to be established from the imaging plane of camera 14 to the loading plane of spatial light modulator 4. The specific method is as follows: coarse calibration patterns of known shapes, such as crosses or grids, are sequentially displayed on spatial light modulator 4 and imaged onto camera 14 via an optical system. By comparing the coordinates of the patterns on spatial light modulator 4 with their coordinates in the image on camera 14, a preliminary coordinate mapping transformation relationship F is determined. Next, the initial compensation phase map calculated above is transformed according to this mapping relationship F and superimposed with a preset focusing phase (e.g., Fresnel lens phase). The superimposed phase map is then loaded onto spatial light modulator 4. This operation aims to enable the light beam to form a focused spot at the far end after transmission through multi-core fiber 10.

[0033] To achieve optimal compensation, the peak-to-background ratio (PBR) is used as a quantification metric to evaluate the quality of the output focal spot. Based on this, key parameters in the coordinate mapping relationship F, including rotation angle, image scaling ratio, and lateral displacement in the x and y directions, are iteratively optimized to maximize the PBR value of the focal spot. The mapping transformation F is then corrected based on the PBR result obtained after each optimization. Through multiple iterations, high-precision coordinate mapping and phase compensation are finally achieved, ensuring the generation of a high-quality probe light field.

[0034] After optimizing the phase compensation map, it is superimposed on the target hologram, which is pre-generated based on the cross-spectral density function of the coherent optical field of the target portion and used to control the coherent structure, to generate the final synthetic hologram, which is then loaded onto the spatial light modulator 4. The laser emitted from the laser 1, after beam expansion and collimation, illuminates the surface of the spatial light modulator 4 onto which the synthetic hologram has been loaded, and performs wavefront phase modulation. The modulated beam then passes through a 4f spatial filter system composed of a lens and an aperture 6 to filter out unnecessary zero-order and other higher-order diffraction light, retaining only the required first-order diffraction light.

[0035] Then, the filtered modulated light is efficiently coupled into the input end of the multi-core optical fiber 10 via a coupling system consisting of a lens and an objective lens. After the optical signal is transmitted in the multi-core optical fiber 10, it is emitted from its far end, ultimately forming a partially coherent optical field with the desired spatial coherence structure.

[0036] In the experiment, the key components used to construct the system include: the multi-core optical fiber 10, which can be an HDIG10K model with 10,000 cores and an imaging surface diameter of approximately 350 μm; the spatial light modulator 4, which can be a reflective pure phase modulator, such as a PLUTO model with 1920×1080 pixels and a pixel size of 8 μm; and the photodetector, which can be a scientific-grade CCD, such as the ECO655MVGE model, with 2448×2050 pixels and a pixel size of 3.45 μm. These components are driven and controlled by computer software (such as MATLAB) to achieve holographic loading, image acquisition, and data processing.

[0037] Specifically, this will be explained in conjunction with two typical types of partially coherent light fields.

[0038] Taking the generation of a partially coherent optical field with Hermitian-Gaussian correlated Sherman modes as an example, the cross-spectral density function of the partially coherent optical field with Hermitian-Gaussian correlated Sherman modes can be decomposed into an incoherent superposition of a series of random electric fields. In implementation, the corresponding electric field modes need to be sequentially and rapidly loaded onto the spatial light modulator 4. A sequence of holograms, in which The specific form is: , in, , For the light field along the frequency domain and Directional coordinates , For the beam along in the spatial domain and Beam width in direction, , Let be the order of the Hermitian polynomial.

[0039] The resulting coherence distribution of the Hermitian-Gaussian correlated Sher mode partially coherent beam is as follows: , in, and respectively along and The lateral coherence width in the direction, For order is and Hermitian polynomials.

[0040] During transmission, its light intensity distribution will change, for example in At that time, the single Gaussian spot on the source plane will gradually split into four spots.

[0041] like Figure 4 As shown, during experimental verification, the light field emitted from the multi-core fiber 10 is coupled out through a 4f system and amplified to the source plane. After being focused by a lens in free space, the light field is acquired by camera 14 at different transmission distances. Since partially coherent light is generated by rapidly switching random modes in a time series, a large number (e.g., 2000) speckle images need to be acquired and statistically averaged to calculate the actual light intensity and coherence distribution. The measurement results are consistent with the theoretically expected transmission characteristics of Hermitian-Gaussian correlated partially coherent light, verifying the effectiveness of this method.

[0042] Taking the generation of a partially coherent optical field with Laguerre-Gaussian correlation Sher mode as an example, the corresponding electric field mode is explained. Represented as: , in, For the beam width, The order of the beam. Let be the radial coordinate of the light field in the spatial frequency domain.

[0043] The resulting coherence distribution of the Laguerre-Gaussian correlated Sher mode partially coherent beam is as follows: , in, The width of the horizontal coherence. For order is The associated Laguerre polynomial.

[0044] Its light intensity distribution exhibits unique evolutionary characteristics during transmission: when approaching the focal plane, it evolves from a Gaussian distribution to a dark hollow structure; after defocusing, it reverts to a Gaussian distribution. In the experiment, the camera 14 was fixed at a specific distance from the source plane, and the transmission of the light beam in free space was simulated by superimposing focusing phases of different focal lengths onto the hologram loaded on the spatial light modulator 4.

[0045] Similarly, as Figure 5 As shown, by acquiring a large number of speckle images and performing statistical analysis, the measured results of light intensity and coherence distribution conform to the theoretical transmission characteristics of Laguerre-Gaussian correlated partially coherent light, thus confirming the feasibility of this method for generating such special structured partially coherent light fields.

[0046] As can be seen from the above specific embodiments, the method and system of the present invention can flexibly and reliably generate and transmit partially coherent optical fields with specific spatial correlation structures.

[0047] It should be noted that the Hermite-Gaussian correlated Sher mode partially coherent optical fields and Laguerre-Gaussian correlated Sher mode partially coherent optical fields described above are only two specific embodiments used to illustrate the technical solution of the present invention, and do not constitute a limitation on the scope of protection of the present invention.

[0048] Example 2: Based on the same inventive principle as Embodiment 1, the present invention also provides a partially coherent optical field generation system based on a multi-core optical fiber 10, comprising: The mode and compensation map generation module is used to determine multiple electric field modes based on the cross spectral density function of the coherent optical field of the target part, and generate corresponding holograms based on the multiple electric field modes; for the multi-core optical fiber 10 used for optical field transmission, the phase distortion between each core of the multi-core optical fiber 10 is measured, and a phase compensation map is generated based on the measurement results. A hologram synthesis module is used to superimpose the hologram and the phase compensation map to generate a synthesized hologram; A wavefront modulation module is used to perform wavefront modulation on the incident laser using the synthesized hologram; The coupling and transmission module is used to couple the modulated laser to the multi-core optical fiber 10 and output the target partial coherent optical field through the multi-core optical fiber 10.

[0049] like Figure 2As shown, the mode and compensation map generation module is mainly used to determine multiple electric field modes based on the cross-spectral density function of the coherent optical field of the target part, and generate corresponding holograms based on these electric field modes. Simultaneously, for the multi-core fiber 10 used for optical field transmission, the module measures the phase distortion between each fiber core and generates a phase compensation map based on the measurement results. This module is mainly implemented in hardware using a computer and corresponding computational software (such as MATLAB), and completes the mode decomposition of the cross-spectral density function, the calculation of the electric field mode holograms, and subsequent phase distortion analysis through algorithms.

[0050] The interferometry unit is a key component of this module for measuring the phase distortion of the multi-core fiber 10, and specifically includes a reference optical path and a detector. The reference optical path is formed by reflecting a laser beam after the first beam splitter 3 through a mirror 15, and is used to provide reference light for interference with the output optical field of the multi-core fiber 10. The detector uses a scientific-grade CCD camera 14 to record the off-axis digital holographic pattern formed after interference.

[0051] The hologram synthesis module is used to superimpose the target light field hologram generated by the mode and compensation map generation module with the phase compensation map to generate the final synthesized hologram. This module is also implemented by computer software to perform the superposition operation of the two images.

[0052] The wavefront modulation module is used to modulate the incident laser wavefront using a synthesized hologram. The core hardware of this module is a reflective pure-phase spatial light modulator 4 (e.g., a PLUTO model), used to load the synthesized hologram and spatially modulate the wavefront phase of the incident laser. The resulting multi-order diffraction field is then passed through a 4f spatial filter system consisting of a first lens 5, a second lens 7, and an aperture 6 placed at the confocal surface of the two lenses to filter out the zeroth order and other higher-order diffraction light, accurately extracting the desired first-order diffraction component.

[0053] The coupling and transmission module is used to couple the modulated laser to the multi-core fiber 10 and transmit the output coherent optical field of the target portion. The coupling optical component in this module consists of a 4f system composed of a third lens 8 and a first objective lens 9, used to efficiently couple the filtered modulated light into the input end of the multi-core fiber 10. The selected multi-core fiber 10 can be, for example, a model characterized by a large number of cores, a small diameter, and good flexibility. After the optical signal is transmitted through the multi-core fiber 10, it exits from its far end. The exited light field is collected by the second objective lens 11, and then collected and collimated by the fourth lens 12, ultimately forming the coherent optical field of the target portion.

[0054] To facilitate observation and recording, the system is also equipped with a second beam splitter 13 and a camera 14. The outgoing light field can be split by the second beam splitter 13 and directly received by the camera 14, or when quantitative analysis is required, it can be combined with a reference light guided by another mirror 15 for interference, and then the camera 14 records the interference pattern for further analysis of the light field characteristics.

[0055] Through the coordinated operation of the aforementioned hardware modules, the system can fully realize the entire process of on-demand generation, phase compensation, wavefront modulation, fiber coupling and transmission of the target partial coherent optical field, as well as the detection and recording of the final optical field, providing a reliable systematic solution for the application of partial coherent optical fields in complex environments.

[0056] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0057] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0058] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0059] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0060] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for generating a partially coherent optical field based on a multi-core optical fiber, characterized in that, include: Based on the cross-spectral density function of the coherent optical field of the target part, determine the corresponding multiple electric field modes, and generate the corresponding hologram based on the multiple electric field modes; For a multi-core optical fiber used for optical field transmission, the phase distortion between each core of the multi-core optical fiber is measured, and a phase compensation map is generated based on the measurement results. The hologram and the phase compensation image are superimposed to generate a composite hologram; The incident laser is wavefront modulated using the synthesized hologram; The modulated laser is coupled to the multi-core optical fiber, and the target partial coherent optical field is output through the multi-core optical fiber.

2. The method for generating a partially coherent optical field based on a multi-core optical fiber according to claim 1, characterized in that: The method for measuring the phase distortion between the cores of the multi-core optical fiber and generating a phase compensation map based on the measurement results is as follows: After a plane wave is incident on the multi-core optical fiber and transmitted, the output optical field is obtained. The output light field is interfered with the reference light to obtain an off-axis digital hologram; The off-axis digital hologram is processed to reconstruct the actual phase distribution of the far end face of the multi-core optical fiber; Calculate the phase conjugate of the actual phase distribution, which serves as the phase compensation diagram for compensating the phase distortion between the cores of the multi-core optical fiber.

3. The method for generating a partially coherent optical field based on a multi-core optical fiber according to claim 2, characterized in that: After generating the phase compensation map, the process further includes: establishing a coordinate mapping relationship from the target imaging plane to the hologram loading plane; transforming the phase compensation map according to the coordinate mapping relationship and superimposing it with a preset focusing phase; and iteratively optimizing the parameters of the coordinate mapping relationship so that the beam transmitted through the multi-core optical fiber forms a focused spot.

4. The method for generating a partially coherent optical field based on a multi-core optical fiber according to claim 1, characterized in that: The method for wavefront modulation of incident laser using the synthetic hologram is as follows: spatially modulate the wavefront phase of the incident laser based on the synthetic hologram; spatially filter the multi-level diffraction field generated after modulation, and extract the preset specific diffraction order components to obtain the modulated laser.

5. The method for generating a partially coherent optical field based on a multi-core optical fiber according to claim 1, characterized in that: The method for calculating the holograms of multiple electric field modes based on the cross-spectral density function of the coherent optical field of the target region is as follows: the holograms of multiple electric field modes are generated based on the mode decomposition of the cross-spectral density function, which is expressed as: ， in, The cross spectral density function is used to describe the light field at any two points in space. and Statistical correlation at the location; Indicates the first An instantaneous scalar field with random fluctuations; For the first The normalized weighting coefficients of each electric field mode satisfy the following: ; This represents the total number of electric field modes involved in the superposition.

6. The method for generating a partially coherent optical field based on a multi-core optical fiber according to claim 1 or 5, characterized in that: The target coherent optical field includes the Hermitian-Gaussian correlated Sher mode coherent optical field, with the electric field mode being: ， in, Indicates the first A random fluctuation of instantaneous scalar electric field mode; Spatial domain coordinates; , For the light field along the frequency domain and Coordinates of direction; , respectively along and The beam width in the direction; , The order of the Hermitian polynomial determines the spatial distribution characteristics of the beam. It is a function generated by a zero-mean random process.

7. The method for generating a partially coherent optical field based on a multi-core optical fiber according to claim 1 or 5, characterized in that: The target coherent optical field includes the Laguerre-Gaussian correlated Sher mode coherent optical field, with the electric field mode being: ， in, Indicates the first A random fluctuation of instantaneous scalar electric field mode; Spatial domain coordinates; Represents the vector coordinates of the light field in the spatial frequency domain; It represents the width of the light beam in the spatial domain and determines the scale of the lateral distribution of the light field; The order of the Laguerre polynomial controls the complexity of the ring structure in which the light field is distributed in the spatial frequency domain; It is a function generated by a random process.

8. A partially coherent optical field generation system based on multi-core optical fiber, characterized in that, include: The pattern and compensation map generation module is used to determine multiple electric field modes based on the cross spectral density function of the coherent light field of the target part, and generate corresponding holograms based on the multiple electric field modes. For a multi-core optical fiber used for optical field transmission, the phase distortion between each core of the multi-core optical fiber is measured, and a phase compensation map is generated based on the measurement results. A hologram synthesis module is used to superimpose the hologram and the phase compensation map to generate a synthesized hologram; A wavefront modulation module is used to perform wavefront modulation on the incident laser using the synthesized hologram; The coupling and transmission module is used to couple the modulated laser to the multi-core optical fiber and output the target partial coherent optical field through the multi-core optical fiber.

9. The partially coherent optical field generation system based on multi-core optical fiber according to claim 8, characterized in that: The partially coherent optical field generation system based on multi-core optical fiber also includes an interferometric measurement unit for measuring the phase distortion of the multi-core optical fiber; the interferometric measurement unit includes a reference optical path and a detector, the reference optical path is used to provide reference light for interference with the output optical field, and the detector is used to record the interference pattern.

10. The partially coherent optical field generation system based on multi-core optical fiber according to claim 8, characterized in that: The wavefront modulation module includes a spatial light modulator for loading the synthesized hologram and performing wavefront phase modulation on the incident laser. The coupling optical components in the coupling and transmission module include a 4f system consisting of a lens and an objective lens, used to couple the modulated laser to the multi-core optical fiber.

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