A programmable structured fiber laser and its modulation method

Abstract

This invention discloses a programmable structured fiber laser and its modulation method in the field of laser technology. The laser combines in-cavity mode dynamic shaping with temporal optical field manipulation. A wavefront shaper is embedded inside the resonant cavity, and the phase distribution of the wavefront shaper is controlled by programming to modulate the phase of the laser within the cavity, achieving stable output of continuous and pulsed structured light. A phase compensation algorithm is used to control the wavefront phase loaded by the wavefront shaper, restoring the generated structured light portion of the optical field to a Gaussian beam that continues oscillation within the cavity. This scheme avoids the unavoidable mode degradation, beam quality deterioration, and energy loss problems of traditional external cavity shaping, significantly improving the beam quality factor and mode purity of the output structured light. This laser integrates laser generation and structured light modulation functions into a compact system, dynamically generating various structured light patterns without replacing any components.

Description

Technical Field

[0001] This invention relates to the field of fiber lasers, and more specifically to a programmable structured light fiber laser and its modulation method. Background Technology

[0002] Structured light (such as vortex beams, Bessel beams, Airy beams, multifocal arrays, etc.) has wide applications in three-dimensional imaging, optical manipulation, quantum communication, laser processing, and other fields. The mainstream methods for generating structured light currently fall into two categories: extracavity modulation and intracavity modulation.

[0003] The current mainstream generation method is "extracavity modulation" technology, which involves converting the laser output into a beam with a specific phase, amplitude, or polarization structure using optical elements (such as spiral phase plates, gratings, spatial light modulators (SLMs), digital micromirrors (DMDs), and metasurfaces). This method facilitates post-modulation, but it is limited by surface defects and phase interruptions in the modulation elements, resulting in scattered light, instability, and structured light purity typically below 90%. Furthermore, the diffraction efficiency of the beam modulated outside the cavity is limited, and the introduction of additional losses by multiple optical elements leads to a significant attenuation of output power.

[0004] To overcome the defects of external modulation, a few studies have attempted to embed modulation devices directly into the laser resonant cavity: directly inserting phase / amplitude modulation elements (such as SLM, DMD, microrings, metasurfaces, etc.) into the laser resonant cavity, making the desired structured light part of the resonant mode and serving as the characteristic mode output of the cavity. However, most of these methods use fixed or preset structured modes, which have the following shortcomings: the control methods are not flexible enough and lack dynamic reconstruction capabilities; they do not support structured light mode switching, and after "strong shaping" of the fundamental Gaussian beam, the most stable fundamental Gaussian beam cannot continue to propagate in the cavity; they rely on precision beam expanders, filters, and Fourier transform optical systems, which impose stringent requirements on optical path stability; and spatial optical path loss has a significant impact on laser gain efficiency and laser stability. Summary of the Invention

[0005] The purpose of this invention is to provide a programmable structured light fiber laser and a modulation method, which solves the problems of low purity and unavoidable energy loss of the external modulation mode of existing lasers, the degradation of structured light beam quality, the complexity of internal modulation mode selection, and the insufficient real-time programmable control capability of the structured light field.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] A programmable structured light fiber laser includes an optical fiber resonator for time-frequency domain optical field modulation and a spatial structured light mode conversion composite device embedded in the optical fiber resonator for dynamic shaping of spatial modes. The spatial structured light mode conversion composite device includes a first wavefront shaper and a second wavefront shaper. The first wavefront shaper is used to convert an incident Gaussian beam into structured light and output a portion of it. The second wavefront shaper is used to perform phase compensation on the remaining structured light to convert it into a Gaussian beam and couple it back into the resonator to maintain laser oscillation.

[0008] As a preferred embodiment of the present invention, the fiber resonant cavity includes a pump source for generating a fundamental mode Gaussian beam and providing pump energy, and also includes a wavelength division multiplexer, a gain medium, a three-ring polarization controller, a fiber collimator, and a polarization-dependent isolator.

[0009] As a preferred embodiment of the present invention, the optical path includes a wavelength division multiplexer, a gain medium, a three-ring polarization controller, a collimator, and a polarization-dependent isolator. The optical path of the fiber resonator is as follows: a first wavelength division multiplexer, a gain medium, a second wavelength division multiplexer, a three-ring polarization controller, a first collimator, a spatial optical path, a second collimator, a polarization-dependent isolator, and a first wavelength division multiplexer. Two pump sources are used to input laser energy to the two wavelength division multiplexers respectively.

[0010] As a preferred embodiment of the present invention, the first wavefront shaper and the second wavefront shaper are one of a spatial light modulator, a deformable mirror array, a liquid crystal phase plate, or a metasurface.

[0011] The fiber resonant cavity is either a linear cavity or a ring cavity;

[0012] The fiber resonant cavity supports continuous light, Q-switched, or mode-locked structured light laser output.

[0013] To apply the above-mentioned programmable structured light laser, this invention also proposes a modulation method based on any of the above-mentioned lasers, comprising the following steps:

[0014] The fundamental mode Gaussian beam oscillating in the fiber resonant cavity is input into the spatial structured light mode conversion composite device, and the phase-modulated optical field required for the spatial structured light mode conversion composite device is obtained based on Fresnel propagation and phase compensation algorithms.

[0015] The fundamental mode Gaussian beam is first phase-modulated using a spatial structured light mode conversion composite device to obtain the target structured light and output it.

[0016] The spatial structured light mode conversion composite device, which loads the phase-modulated light field, performs a second phase modulation on the remaining light field after the first phase modulation, so as to restore it to the fundamental mode Gaussian beam and return it to the fiber resonator cavity to continue oscillating.

[0017] As a preferred embodiment of the present invention, the step of obtaining the phase-modulated optical field required for the spatial structured light mode conversion composite device based on Fresnel propagation and phase compensation algorithm includes:

[0018] Initialization: The oscillating fundamental mode Gaussian beam is input into the modulation plane of the spatial structured light mode conversion composite device to generate initial structured light on the target plane of the spatial structured light mode conversion composite device; the amplitude and phase of the initial structured light are used as the initial modulation complex amplitude and loaded into the modulation plane of the spatial structured light mode conversion composite device.

[0019] Forward propagation: The modulated complex amplitude is transmitted to the target plane via the Fresnel diffraction propagation operator to obtain the target plane complex amplitude. The amplitude of the target plane complex amplitude is replaced by the amplitude of the target fundamental mode Gaussian beam to form a new target plane complex amplitude.

[0020] Backpropagation: The new target plane complex amplitude is propagated back to the modulation plane using the Fresnel propagation operator to obtain the modulation plane complex amplitude. The amplitude of the modulation plane complex amplitude is then replaced with the amplitude of the initial structured light complex amplitude to form a new modulation complex amplitude.

[0021] The forward and reverse propagation processes are iterated, and when the difference between the amplitude of the complex amplitude of the target plane and the amplitude of the Gaussian beam of the target base film converges to a preset threshold, the modulated complex amplitude is output, and the phase-controlled optical field is obtained based on the modulated complex amplitude.

[0022] As a preferred embodiment of the present invention, the structured light is one of the following: vortex light, Laguerre-Gaussian beam, Bessel beam, Airy beam, or vector beam.

[0023] As a preferred embodiment of the present invention, when the target structured light is a vortex light, the light field of the modulation plane of the input spatial structured light mode conversion composite device is expressed as follows:

[0024] ;

[0025] in, It is the complex amplitude of the incident fundamental mode Gaussian beam; It is the amplitude constant; The waist radius; Spatial coordinates;

[0026] The light field modulated by the spatial structured light mode conversion composite device and propagated by Fresnel is:

[0027] ;

[0028] in, It is the modulated complex amplitude; for k represents the beam; The wavelength of light; It is the attenuation factor; To start from the initial plane point The coordinates of the observation point.

[0029] As a preferred embodiment of the present invention, the initial modulation complex amplitude includes an initial amplitude and an initial phase, wherein the initial phase is expressed as:

[0030]

[0031] in, This is the initial phase; For vortex topological charges; It is the azimuth angle;

[0032] The initial amplitude is expressed as:

[0033] ;

[0034] in, .

[0035] As a preferred embodiment of the present invention, the complex amplitude of the target fundamental mode Gaussian beam is expressed as:

[0036] ;

[0037] The complex amplitude of the target plane is expressed as:

[0038] ;

[0039] in, The phase is obtained by phase constraint during the iteration process.

[0040] The beneficial effects of this invention are as follows:

[0041] This invention provides a laser cavity programming adjustment method, which is based on the combination of dynamic shaping of the resonant cavity mode and temporal optical field modulation. By controlling the phase distribution of the wavefront shaper through computer programming, the phase of the laser in the cavity is modulated. A portion is directly output as a high-purity structured light laser beam, while the other portion recovers the base film mode and continues to propagate back into the cavity, thus achieving oscillation in the resonant cavity.

[0042] This invention places a spatial structured light generating device inside the laser resonant cavity and uses a phase compensation algorithm to control the wavefront phase loaded by the wavefront shaper. This ensures stable output of the target structured light mode (such as Laguerre-Gaussian LG, Hermitian-Gaussian HG, etc.), and the remaining optical field is restored to a Gaussian beam that can continue to oscillate inside the cavity. This avoids the unavoidable mode degradation, beam quality deterioration, and energy loss problems in traditional external cavity shaping schemes, and significantly improves the beam quality factor (M) of the output structured light.2 Factors), model purity;

[0043] By directly embedding computer programmable control components into the laser resonant cavity, it is possible to switch structured light patterns in real time or according to a program, ensuring mode purity and stability, such as the output of vortex beams, holographic beams, etc. Under the condition of ensuring stable structured light output, a special phase diagram can be designed to restore the most stable fundamental mode Gaussian beam to continue propagating in the cavity, improving laser stability and ensuring stable laser start-up and mode-locking operation.

[0044] The optical path design saves optical components and optical path length to the greatest extent, simplifies the system structure, improves integration, and reduces debugging complexity. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the laser structure of the present invention;

[0046] Figure 2 This is a schematic diagram of the modulation method of the present invention;

[0047] Figure 3 The laser output specifications of this invention;

[0048] Figure 4 A phase hologram loaded for the second wavefront shaper (spatial light modulator-SLM) of the present invention;

[0049] Figure 5 The structured light field generated by the first wavefront shaper of this invention;

[0050] Figure 6 The phase hologram and corresponding light field intensity map loaded for the second wavefront shaper of the present invention;

[0051] In the diagram: 1. Pump source; 2. Wavelength division multiplexer; 3. Gain medium; 4. Three-ring polarization controller; 5. Collimator; 6. Spatial structured light mode conversion composite device; 7. First wavefront shaper; 8. Second wavefront shaper; 9. Polarization-dependent isolator. Detailed Implementation

[0052] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0053] Example 1

[0054] like Figure 1As shown, a programmable structured light fiber laser includes an optical fiber resonator for time-frequency domain optical field modulation and a spatial structured light mode conversion composite device 6 embedded in the optical fiber resonator for dynamic shaping of spatial modes. The spatial structured light mode conversion composite device 6 includes a first wavefront shaper 7 and a second wavefront shaper 8. The first wavefront shaper 7 is used to convert the incident Gaussian beam into structured light and output part of it. The second wavefront shaper 8 is used to perform phase compensation on the remaining structured light to convert it into a Gaussian beam and couple it back into the resonator to maintain laser oscillation.

[0055] The fiber resonant cavity includes a pump source 1 for generating a fundamental mode Gaussian beam and providing pump energy, as well as a wavelength division multiplexer 2, a gain medium 3, a three-ring polarization controller 4, a fiber collimator 5, and a polarization-dependent isolator 9.

[0056] Working principle: Pump source 1 provides external energy to the fiber resonator. After coupling and amplification through the fiber optical path, a fundamental mode Gaussian beam is formed and enters the spatial optical path. Then, the first wavefront shaper 7 modulates the fundamental mode Gaussian beam to form a stable structured light beam output. The second wavefront shaper 8 loads a phase-controlled optical field obtained based on Fresnel propagation and phase compensation algorithm. The remaining optical field is modulated by the second wavefront shaper 8 to restore the fundamental mode Gaussian beam and maintain oscillation in the fiber resonator.

[0057] Preferably, the optical path of the fiber resonator is as follows: first wavelength division multiplexer 2, gain medium 3, second wavelength division multiplexer 2, three-ring polarization controller 4, first fiber collimator 5, spatial optical path, second fiber collimator 5, polarization correlation isolator 9, and first wavelength division multiplexer 2. Two pump sources 1 are used to input laser energy to the two wavelength division multiplexers 2 respectively.

[0058] Among them, pump source 1 provides external energy to the gain medium; wavelength division multiplexer 2 can efficiently combine and couple pump light and signal light of different wavelengths, allowing them to enter the gain medium simultaneously, thereby amplifying the signal light by the pump energy and outputting the optical signal of the required wavelength; gain medium 3 can be a single-mode erbium-doped fiber, which provides stimulated amplification in the required wavelength band; three-ring polarization controller 4 adjusts the polarization state by mechanically twisting the fiber to achieve polarization control and mode matching, and adjusts to achieve mode locking; fiber collimator 5 is used to collimate the diverging beam in the fiber into parallel light or to efficiently couple free space light into the fiber; polarization correlation isolator 9 is used to achieve unidirectional light transmission and suppress reflection.

[0059] Traditional laser resonators naturally tend to oscillate in the fundamental mode or low-order modes. It is extremely difficult to stably generate high-order modes or complex structured optical fields within the cavity, which easily leads to mode competition, mode instability, and low efficiency. In this embodiment, by setting a first wavefront shaper 7, the optical field can be controlled in real time within the cavity and then output outside the fiber resonator. At the same time, the second wavefront shaper 8 is used to return the fundamental mode Gaussian beam, ensuring that the cavity still oscillates mainly in the fundamental mode, thus achieving a balance between mode selection and cavity stability.

[0060] Preferably, the first wavefront shaper 7 and the second wavefront shaper 8 are one of a spatial light modulator, a deformable mirror array, a liquid crystal phase plate, or a metasurface.

[0061] Preferably, the fiber resonant cavity is either a linear cavity or a ring cavity. In a specific implementation, an arbitrary first wavefront shaper 7 with programmable phase (such as a spatial light modulator-SLM or its equivalent functional device) is directly inserted into the fiber resonant cavity as a component of the laser.

[0062] Preferably, the fiber resonator supports continuous light, Q-switched, or mode-locked structured light laser output.

[0063] Working principle:

[0064] This embodiment employs a dual-pump source design. The pump light output from the pump source 1 enters the first port of the first wavelength division multiplexer 2, the third port of the first wavelength division multiplexer 2 enters the first port of the gain medium 3, and the second port of the gain medium 3 enters the second wavelength division multiplexer 2. The first port of the second wavelength division multiplexer 2 receives the pump light from the second pump source 1, and together they propagate through the gain medium 3 to the second port of the second wavelength division multiplexer 2, and then to the first port of the three-ring polarization controller 4. From the second port of the three-ring polarization controller 4, the light enters the spatial structured light mode conversion composite device 6 through the first port of the fiber collimator 5. After the structured light mode is generated, it is output from the second port of the spatial structured light mode conversion composite device 6. The fundamental mode Gaussian beam then re-enters the fiber optic path through another fiber collimator 5, continues to propagate through the first port of the fiber collimator 5, propagates through the first port of the polarization correlation isolator 9 to the second port, and returns to the second port of the first wavelength division multiplexer 2, thereby forming an oscillation in the resonant cavity.

[0065] Among them, the dual-pump source 1 is designed to provide pump energy to the mode-locked laser, enabling fine and optimized control of output power, repetition rate and stability, and is especially suitable for cutting-edge applications with extremely high performance requirements.

[0066] like Figure 2-6As shown, in order to apply the above-mentioned programmable structured optical fiber laser, the present invention also proposes a modulation method based on any of the above-mentioned fiber lasers, comprising the following steps:

[0067] S1: Embed a first wavefront shaper 7 and a second wavefront shaper 8 in the fiber resonant cavity. In this embodiment, the first wavefront shaper 7 is a spatial light modulator (SLM), and the second wavefront shaper 8 is a spatial light modulator (SLM).

[0068] S2: The fundamental mode Gaussian beam oscillating within the fiber optic resonant cavity is input into the first wavefront shaper 7. This fundamental mode Gaussian beam is generated by the pump source 1, processed by the fiber optic path, and then input into the first wavefront shaper 7. Subsequently, the returning fundamental mode Gaussian beam couples with the new energy input from the pump source 1 to generate the fundamental mode Gaussian beam for the next cycle, which then oscillates within the fiber optic resonant cavity. Specifically, step S2 includes:

[0069] S21: Initialization: Input the oscillating fundamental mode Gaussian beam into the modulation plane of the first wavefront shaper 7 to generate an initial structured beam on the target plane of the first wavefront shaper 7; use the amplitude and phase of the initial structured beam as the initial modulation complex amplitude and load it into the modulation plane of the first wavefront shaper 7.

[0070] S22: Forward propagation: The modulated complex amplitude is transmitted to the target plane via the Fresnel diffraction propagation operator to obtain the target plane complex amplitude. The amplitude of the target plane complex amplitude is replaced by the amplitude of the target fundamental mode Gaussian beam to form a new target plane complex amplitude.

[0071] S23: Backpropagation: The new target plane complex amplitude is propagated back to the modulation plane using the Fresnel propagation operator to obtain the modulation plane complex amplitude. The amplitude of the modulation plane complex amplitude is replaced by the amplitude of the initial structured light complex amplitude to form a new modulation complex amplitude.

[0072] S24: Iteration: Iterate S22-S23. When the difference between the amplitude of the complex amplitude of the target plane and the amplitude of the Gaussian beam of the target base film converges to a preset threshold, output the modulated complex amplitude. Based on the modulated complex amplitude, obtain the phase-controlled optical field. The preset threshold is an empirical parameter.

[0073] Through the above iterative process, the optimal phase distribution of the first wavefront shaper 7 can be obtained, so that the incident structured light can be restored to a Gaussian beam distribution on the target plane after phase modulation.

[0074] S3: Based on the first wavefront shaper 7, the fundamental mode Gaussian beam is phase-modulated for the first time to obtain the target structured light and output it;

[0075] S4: The second wavefront shaper 8, which loads the phase-modulated optical field, performs a second phase modulation on the remaining optical field after the first phase modulation, so as to restore it to the fundamental mode Gaussian beam and return it to the fiber resonator cavity to continue oscillating.

[0076] Preferably, the structured light can be any type of light field mode, including vortex light, Laguerre-Gaussian beam, Bessel beam, Airy beam, or vector beam.

[0077] In this embodiment, taking vortex light as the target structured light as an example, the fundamental mode Gaussian beam input to the modulation plane of the first wavefront shaper 7 is represented as:

[0078] ;

[0079] in, It is the complex amplitude of the incident fundamental mode Gaussian beam; It is the amplitude constant; The waist radius; Spatial coordinates;

[0080] The light field propagated by Fresnel after modulation by the first wavefront shaper 7 is:

[0081] ;

[0082] in, It is the modulated complex amplitude; for k represents the beam; The wavelength of light; It is the attenuation factor; To start from the initial plane point Coordinates to the observation point;

[0083] In step S22, initializing the modulation complex amplitude includes the initial amplitude and the initial phase, and the initial phase is expressed as:

[0084] ;

[0085] in, This is the initial phase; For vortex topological charges; It is the azimuth angle;

[0086] The initial amplitude is expressed as:

[0087] ;

[0088] in, .

[0089] The target structured light is returned as a fundamental Gaussian beam by the second wavefront shaper 8, and the fundamental Gaussian beam that needs to be returned is used as the target fundamental Gaussian beam, which is the target of the iteration in step S2. Its complex amplitude is expressed as:

[0090] ;

[0091] The complex amplitude of the target plane is expressed as:

[0092] ;

[0093] in, The phase is obtained by phase constraint during the iteration process.

[0094] The simulation diagram provided in this embodiment is as follows: Figure 3-6 As shown, where, Figure 3 The laser output parameters, from left to right, are the continuous laser spectrum, pulsed laser spectrum, and pulsed laser pulse sequence. The spatial structured light generation method is as follows: an algorithm is written using Matlab to generate... Figure 4 The high-precision hologram shown is used for structured light generation. By loading the hologram onto the second wavefront shaper 8, the structured light can be generated. Figure 5 The structured light field shown.

[0095] Figure 4 Phase hologram loaded for a spatial light modulator (SLM), i.e., phase-controlled light field: from left to right, a vortex light with orbital angular momentum of 10, the letter A, and the coordinate plane of the box. Figure 5 The structured light field generated by the first wavefront shaper 7, from left to right, is a vortex light with an orbital angular momentum of 10, the letter A, and the box coordinate guide.

[0096] The method for recovering the Gaussian beam from the base film is shown in the figure below: An algorithm written in Matlab is used to generate a high-precision phase hologram, which is then loaded into the second wavefront shaper 8 to generate a Gaussian light field. Example diagrams of the phase hologram and light field intensity are shown below. Figure 6 As shown, Figure 6 From left to right: the phase hologram loaded by the second wavefront shaper 8 and the corresponding light field intensity map.

[0097] This invention places a spatial structured light mode conversion composite device 6 inside the laser resonant cavity and uses a phase compensation algorithm to control the wavefront phase of the SLM loading, enabling the stable output of the target structured light mode (such as vortex light, Laguerre-Gaussian LG, Hermitian-Gaussian HG, etc.). The Gaussian beam can then return to the cavity to continue oscillating, avoiding the unavoidable mode degradation, beam quality deterioration, and energy loss problems inherent in traditional external cavity shaping schemes. This significantly improves the beam quality factor (M) of the output structured light. 2 Factors), pattern purity.

[0098] This invention achieves real-time, mechanically motion-free switching between arbitrary structured light modes (including vortex beams and arbitrary light field distributions) and the fundamental Gaussian beam, enabling stable oscillation within the resonant cavity. This method not only improves the purity and stability of structured light modes but also achieves real-time multi-mode switching, high integration, and improved output efficiency, fundamentally solving the problems of poor mode reconfigurability, high energy loss, and high system complexity in traditional structured light lasers. Direct intracavity oscillation generates the target mode, fully utilizing the energy extraction efficiency of the laser gain medium. Compared to the typical 30-50% or even higher energy loss in external shaping schemes due to mode matching losses and the absorption / scattering / diffraction efficiency of optical components, this scheme can improve the overall light-to-light conversion efficiency of the structured light output to a level close to the output efficiency of the laser's fundamental Gaussian beam.

[0099] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A modulation method for a programmable structured light fiber laser, the laser comprising a fiber resonator for time-frequency domain optical field modulation, and a spatial structured light mode conversion composite device (6) embedded in the fiber resonator for dynamic shaping of spatial modes, the spatial structured light mode conversion composite device (6) comprising a first wavefront shaper (7) and a second wavefront shaper (8), the first wavefront shaper (7) being used to convert an incident Gaussian beam into structured light and partially output it, and the second wavefront shaper (8) being used to perform phase compensation on the remaining structured light to convert it into a Gaussian beam coupled back into the resonator to maintain laser oscillation, characterized in that, Modulation methods include: The fundamental mode Gaussian beam oscillating in the fiber resonant cavity is input into the spatial structured light mode conversion composite device (6). Initialization: The oscillating fundamental mode Gaussian beam is input into the modulation plane of the spatial structured light mode conversion composite device (6) to generate initial structured light on the target plane of the spatial structured light mode conversion composite device (6); the amplitude and phase of the initial structured light are used as the initial modulation complex amplitude and loaded into the modulation plane of the spatial structured light mode conversion composite device (6); Forward propagation: The modulated complex amplitude is transmitted to the target plane via the Fresnel diffraction propagation operator to obtain the target plane complex amplitude. The amplitude of the target plane complex amplitude is replaced by the amplitude of the target fundamental mode Gaussian beam to form a new target plane complex amplitude. Backpropagation: The new target plane complex amplitude is propagated back to the modulation plane using the Fresnel propagation operator to obtain the modulation plane complex amplitude. The amplitude of the modulation plane complex amplitude is then replaced with the amplitude of the initial structured light complex amplitude to form a new modulation complex amplitude. The forward and reverse propagation processes are iterated, and the modulated complex amplitude is output when the difference between the amplitude of the complex amplitude of the target plane and the amplitude of the Gaussian beam of the target base film converges to a preset threshold. The phase-controlled optical field is obtained based on the modulated complex amplitude. The fundamental mode Gaussian beam is first phase modulated based on the spatial structured light mode conversion composite device (6) to obtain the target structured light and perform partial output; The spatial structured light mode conversion composite device (6) based on the phase-modulated light field load performs a second phase modulation on the remaining structured light after the first phase modulation, so as to restore it to the fundamental mode Gaussian beam and return it to the fiber resonator cavity to continue oscillating.

2. The modulation method for a programmable structured optical fiber laser according to claim 1, characterized in that, The fiber resonant cavity includes a pump source (1) for generating a fundamental mode Gaussian beam and providing pump energy, and also includes a wavelength division multiplexer (2), a gain medium (3), a three-ring polarization controller (4), a fiber collimator (5), and a polarization-dependent isolator (9).

3. The modulation method for a programmable structured optical fiber laser according to claim 2, characterized in that, The optical path of the fiber resonator is as follows: first wavelength division multiplexer (2), gain medium (3), second wavelength division multiplexer (2), three-ring polarization controller (4), first fiber collimator (5), spatial optical path, second fiber collimator (5), polarization correlation isolator (9), first wavelength division multiplexer (2), and two pump sources (1) are used to input laser energy to the two wavelength division multiplexers (2) respectively.

4. The modulation method for a programmable structured optical fiber laser according to claim 1, characterized in that, The first wavefront shaper (7) and the second wavefront shaper (8) are one of the following: spatial light modulator, deformable mirror array, liquid crystal phase plate or metasurface; The fiber resonant cavity is either a linear cavity or a ring cavity; The fiber resonant cavity supports continuous light, Q-switched, or mode-locked structured light laser output.

5. The modulation method for a programmable structured optical fiber laser according to claim 1, characterized in that, The structured light is one of the following: vortex light, Laguerre-Gaussian beam, Bessel beam, Airy beam, or vector beam.

6. The modulation method for a programmable structured optical fiber laser according to claim 5, characterized in that, When the target structured light is a vortex light, the light field of the modulation plane of the input spatial structured light mode conversion composite device (6) is expressed as follows: ； in, It is the complex amplitude of the incident fundamental mode Gaussian beam; It is the amplitude constant; The waist radius; Spatial coordinates; The light field modulated by the spatial structured light mode conversion composite device (6) and propagated by Fresnel is: ； in, It is the modulated complex amplitude; for k represents the beam; The wavelength of light; It is the attenuation factor; To start from the initial plane point The coordinates of the observation point.

7. The modulation method for a programmable structured optical fiber laser according to claim 6, characterized in that, The initialization modulation complex amplitude includes an initial amplitude and an initial phase, the initial phase being expressed as: ； in, This is the initial phase; For vortex topological charges; It is the azimuth angle; The initial amplitude is expressed as: ； in, .

8. The modulation method for a programmable structured optical fiber laser according to claim 7, characterized in that, The complex amplitude of the target fundamental mode Gaussian beam is expressed as: ； The complex amplitude of the target plane is expressed as: ； in, The phase is obtained by phase constraint during the iteration process.

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