Method for realizing real-time dynamic regulation and control of multi-station light field amplitude of high-power laser shutter

Abstract

The invention discloses a method for realizing the real-time dynamic regulation and control of the multi-station light field amplitude of a high-power laser shutter, and the method comprises the steps: embedding a long-period fiber grating into a QBH connector of the high-power laser shutter, and carrying out the regulation and control of the amplitude distribution of an output light field through the long-period fiber grating. Signal laser of a specific transverse mode, which is originally propagated in an optical fiber core, is coupled to other specific modes according to a modulation requirement of light field amplitude distribution to form laser output of specific amplitude distribution, and then a semiconductor cooler (TEC) is controlled by a computer to apply a temperature field to the long-period fiber grating. The purpose of regulating and controlling the structural parameters of the long-period fiber grating is achieved, and real-time dynamic regulation and control of high-power laser light fields output at different interfaces of the laser shutter are achieved. Compared with an existing method, diversified laser output modes can be achieved on the premise that complexity is not increased, and the method is suitable for the fields of precision machining, optical communication and the like.

Description

Technical Field

[0001] The present invention belongs to the field of high-power optical fiber laser equipment, and in particular relates to a method for realizing real-time dynamic control of multi-position light field amplitude of a high-power laser shutter. Background Art

[0002] Since its introduction, lasers have been widely used in the fields of optical fiber communication, sensor technology, medical biology and industrial processing due to their advantages of small size, high stability, low environmental impact and high conversion efficiency. In recent years, with the continuous development of the national economy, intelligent manufacturing has become an important direction for the optimization and upgrading of my country's manufacturing industry. Laser manufacturing, as the main manufacturing method of intelligent manufacturing, has been widely used in material processing. At the same time, high-power laser shutters have been vigorously developed and applied because they can enable a laser to have multiple laser output ends.

[0003] Since the amplitude distribution of the laser output light field (i.e., the transverse mode characteristics of the laser) has a profound impact on the processing and application of materials, for example, in laser cutting, the laser with Gaussian light energy structure has the advantages of fast cutting speed and high cutting surface finish when cutting thin plates, but in thick plate cutting, the laser with flat top or ring light energy structure is often used to obtain high-quality cutting side and improve cutting speed. In order to achieve high-quality processing effect and ensure processing efficiency, it is necessary to dynamically adjust the laser light field amplitude distribution according to the specific application scenario. Therefore, a laser that can dynamically adjust the laser light energy structure is needed to meet the processing needs of different materials. Therefore, with the continuous development of my country's intelligent manufacturing field, manufacturing applications have put forward new requirements for the amplitude distribution of the laser light field output by the laser. It is necessary to flexibly adjust the light field amplitude distribution of the output laser according to the application requirements, so as to promote the laser to achieve cutting, welding, cladding and other deep applications of various materials in a wider range of fields. Therefore, how to flexibly adjust the amplitude distribution of the laser light field output by the laser according to the actual application needs is one of the research frontiers in the laser field and the focus of attention in the field of intelligent manufacturing.

[0004] At present, there are two main methods for regulating the light field of laser output. One is the light field regulation method based on free space devices, and the other is the light field regulation method based on optical fiber micro-nano structures. The light field regulation method based on free space devices introduces free space structure devices outside the laser to regulate the light field of the laser output to form a new light field, and obtain a laser with a special light energy structure. However, the new light field regulated by this method has low energy utilization, low mode purity, and is not easy to withstand high-power lasers. In addition, the introduction of free space devices increases the complexity of the laser system, and the system stability is easily affected by external factors, which destroys the advantages of flexible output of optical fiber lasers and cannot meet the requirements of high-power, high-stability, flexible and free laser applications in the field of intelligent manufacturing. Therefore, the laser light field regulation method based on optical fiber micro-nano structures that can be easily integrated with optical fiber laser systems and has high stability has become a research hotspot in the field of optics.

[0005] Different from the light field control method based on free-space devices, the light field control method based on fiber micro-nano structure refers to a new light field control method that uses fiber devices with special micro-nano structures to control the laser light field of fiber lasers. Fiber micro-nano devices with special micro-nano structures refer to a new type of optical passive devices formed by etching specific micro-nano structures inside the fiber core or on the fiber end face by means of photolithography or chemical corrosion. Compared with the light field control method based on free-space devices, this type of device is fully compatible with optical fibers, which enables it to form a fully optical fiber whole with fiber lasers, thus becoming an ideal means for controlling laser light fields. By integrating this fiber device into the QBH output head of a high-power laser shutter, real-time dynamic control of multi-station laser amplitude distribution can be achieved. Summary of the invention

[0006] The purpose of the present invention is to provide a method for realizing real-time dynamic regulation of the multi-position light field amplitude of a high-power laser shutter, so that the amplitude distribution of the laser light field output by the high-power laser shutter can be flexibly regulated according to actual application requirements, thereby realizing the demand for real-time regulation of the output laser light field amplitude distribution in multiple fields.

[0007] The technical solution to achieve the purpose of the present invention is: a method for realizing real-time dynamic control of the amplitude of a high-power laser shutter multi-station light field, the steps are as follows:

[0008] Step 1, build a device, including a main control computer, a high-power laser, a high-power laser shutter, a first QBH connector, and a second QBH connector. The second QBH connector adopts a QBH connector that integrates a long-period fiber grating and a temperature-controlled TEC. The high-power laser is connected to the high-power laser shutter through the first QBH connector. The second QBH connector is connected to different output stations of the high-power laser shutter. The main control computer is connected to the TEC and the high-power laser shutter respectively to achieve time-sharing and energy-sharing output of lasers at different stations and dynamic regulation of laser amplitude at different stations; proceed to step 2.

[0009] Step 2: Establish a mathematical analysis model for the long-period fiber grating to control the amplitude distribution of the laser light field, as well as a function of the change in the structural parameters of the long-period fiber grating when it is subjected to the temperature field, and then proceed to step 3.

[0010] Step 3, start the high-power laser, couple the laser to the second QBH connector and output it after passing through the high-power laser shutter, and at the same time, according to the mathematical analysis model of the long-period fiber grating regulating the laser light field amplitude distribution, and the function of the change of the structural parameters of the long-period fiber grating when it is affected by the temperature field, the computer obtains the TEC control parameters required for the target laser light field amplitude distribution, and proceeds to step 4.

[0011] Step 4: The computer adjusts the TEC temperature according to the obtained TEC control parameters, applies a temperature field to the long-period fiber grating, realizes the regulation of the structural parameters, affects the spot distribution effect by changing the structural parameters, and finally achieves the target amplitude distribution.

[0012] Compared with the prior art, the present invention has the following significant advantages:

[0013] (1) A method for realizing real-time dynamic regulation of the light field amplitude output by a high-power laser shutter is provided, so as to flexibly regulate the light field amplitude distribution output by the high-power laser shutter according to actual application requirements.

[0014] (2) Use the special periodic micro-nanostructure based on fiber grating to flexibly control the amplitude distribution of the laser light field and maintain a stable and reliable structure at the output end of the high-power laser shutter.

[0015] (3) The dynamic temperature field is used to dynamically adjust the structural parameters of the fiber Bragg grating, so that the long-period fiber Bragg grating can couple the fundamental mode to different other modes according to application requirements, thereby achieving the purpose of real-time regulation of the laser light field amplitude distribution in multiple fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a flow chart of a method for realizing real-time dynamic control of the output light field amplitude of a high-power laser shutter.

[0017] Figure 2 The present invention is a schematic diagram of the structure for realizing real-time dynamic regulation of the output light field amplitude of a high-power laser shutter.

[0018] Figure 3 This is the effect diagram of the Gaussian amplitude distribution of the spot directly output by the high-power laser shutter output.

[0019] Figure 4 This is the effect diagram of the light spot with ring amplitude distribution output by the high-power laser shutter after regulation. DETAILED DESCRIPTION

[0020] The present invention will be described in further detail below with reference to the accompanying drawings.

[0021] Combination Figure 1 and Figure 2 , a method for realizing real-time dynamic control of the optical field amplitude of a fiber laser, integrating a long-period fiber grating capable of adjusting the amplitude distribution of a high-power laser into a QBH connector at the output end of a laser shutter, matching the different requirements of each station for the amplitude distribution, matching the resonant wavelengths of different amplitude distribution modes with the working wavelength of a high-power laser connected to the input end of the laser shutter, and coupling part of the fundamental mode of the laser output by the original laser to other modes by the long-period fiber gratings at different stations, realizing different laser amplitude outputs at multiple stations, and applying a temperature field to the long-period fiber grating by computer-controlled TEC, regulating the structural parameters of the long-period fiber grating, and finally realizing real-time dynamic control of the amplitude distribution of a high-power laser, the specific steps are as follows:

[0022] Step 1, build a device, including a main control computer, a high-power laser, a high-power laser shutter, a first QBH connector, and a second QBH connector. The second QBH connector adopts a QBH connector that integrates a long-period fiber grating and a temperature-controlled TEC. The high-power laser is connected to the high-power laser shutter through the first QBH connector. The second QBH connector is connected to different output stations of the high-power laser shutter. The main control computer is connected to the TEC and the high-power laser shutter respectively to achieve time-sharing and energy-sharing output of lasers at different stations and dynamic regulation of laser amplitude at different stations.

[0023] Long-period fiber gratings have unique mode coupling characteristics. According to the regulation requirements of the light field amplitude distribution, they can couple specific transverse modes propagating in the fiber core to other transmission modes in the fiber, thereby realizing laser output of a specific transverse mode combination. This process achieves precise modulation of the energy structure of the fiber laser light field. Since the period of long-period fiber gratings is usually at the sub-millimeter level, traditional ultraviolet lithography technology based on phase masks is not applicable. Therefore, this study uses a point-by-point scanning method to write long-period fiber gratings, using a continuous argon ion frequency-doubled laser with an output wavelength of 244nm and a power of 100mW as the writing light source. See Table 1 for specific parameter settings:

[0024] Table 1 Parameters of long period fiber grating

[0025]

[0026] Based on the experimental results of long-period fiber grating writing, a long-period fiber grating preparation process with the ability to control the amplitude distribution of the laser light field is summarized, such as precision writing process, heat treatment process, packaging process, etc. The heat treatment process is as follows: (1) Open the annealing furnace and set the annealing temperature to 60°C; (2) Place the long-period fiber grating after writing in the annealing furnace for annealing, and set the annealing time to 30 days. After 30 days, take out the annealed long-period fiber grating and protect the grating area of ​​the long-period fiber grating to prevent the fiber grating from breaking; (3) Open the high-temperature annealing furnace and place the grating area of ​​the long-period fiber grating in the heating zone of the high-temperature annealing furnace; first set the heating temperature of the high-temperature annealing furnace to 100°C, and stay for 1 minute after the heating zone temperature reaches 100°C; then set the temperature of the high-temperature annealing furnace to 120℃, stay for 1 minute after the temperature of the heating zone reaches 120℃; then repeat the operation, increase the temperature of the high-temperature annealing furnace by 20℃, and stay for 1 minute after each temperature reaches stability; when the temperature of the high-temperature annealing furnace is set to 200℃, stay for 3 minutes after the temperature of the heating zone reaches 200℃; then set the temperature of the high-temperature annealing furnace to 180℃, and stay for 1 minute after the temperature of the heating zone reaches 180℃; then repeat the operation, reduce the temperature of the high-temperature annealing furnace by 20℃, and stay for 1 minute after each temperature reaches stability, until the heating area returns to room temperature.

[0027] Go to step 2.

[0028] Step 2: Establish a mathematical analysis model for the long-period fiber grating to regulate the amplitude distribution of the laser light field, as well as a function of the change in the structural parameters of the long-period fiber grating when it is subjected to the temperature field.

[0029] In order to establish a mathematical model that can characterize the amplitude distribution of the laser light field regulated by the long-period fiber grating, it is necessary to analyze the energy exchange mechanism between the fundamental mode and other modes in the fiber core based on the structural characteristics and parameters of the long-period fiber grating. The specific process is as follows:

[0030] First, the wave vector of the fundamental mode is superimposed with the wave vector of the long-period fiber grating surface, and the wave vector of the coupled mode is determined by analyzing its phase matching conditions. Based on this, the structural parameters of the long-period fiber grating are introduced into the existing mode coupling equation. By improving the mode coupling theory, the coupling modes of the long-period fiber grating and their coupling relationships are obtained. On this basis, the proportion of the fundamental mode and other modes in the laser energy after long-period fiber grating modulation is calculated. Combining the characteristic equation of the electromagnetic field component vector solution in the optical fiber with the two-dimensional distribution formula of the optical fiber electric field, the two-dimensional light field amplitude distribution of the output laser is further calculated. These equations are combined to finally establish a mathematical model based on the mode coupling equation. This model provides a theoretical basis for the design of long-period fiber gratings with adjustable light fields and controllable modes, which helps to further improve the precision control capability of fiber laser systems.

[0031] According to the continuity conditions of the electromagnetic field at the cladding interface and the core, the relationship expression between the constants in the field expression can be obtained. The expression is written in matrix form. When the determinant of the coefficient matrix is ​​equal to zero, the system of equations has a non-zero solution, that is, det[M] = 0, so it can be concluded that:

[0032]

[0033] Where U is the normalized transverse phase parameter, W is the normalized transverse attenuation parameter, J represents the first-order Bessel function, K represents the second-order modified Bessel function, the subscript l represents the l-th order Bessel function, the value of l is the serial number in the circumferential direction, n1 is the core refractive index, and n2 is the cladding refractive index. After obtaining U or W, the corresponding propagation constant β can be obtained.

[0034] The core guided mode uses Bessel function to simplify the characteristic equations of EH mode and HE mode:

[0035]

[0036] Where U is the normalized lateral phase parameter, W is the normalized lateral attenuation parameter, J represents the first-kind Bessel function, K represents the second-kind modified Bessel function, the subscript l represents the l-th-order Bessel function, and the value of l is the serial number in the circumferential direction.

[0037] Weakly guided approximation is performed, n1≈n2, the fiber Bragg grating core fundamental mode (HE 11 or LP 01 )The dispersion equation of the effective refractive index is:

[0038]

[0039] Wherein, V is the normalized cutoff frequency, b is the normalized effective refractive index of the fiber guided mode, J and K represent the first-order Bessel function and the second-order modified Bessel function, respectively, and the subscripts 0 and 1 represent the 0th-order Bessel function and the 1st-order Bessel function, respectively.

[0040] The mathematical analysis model for regulating the amplitude distribution of the laser light field using long-period fiber grating is established as follows:

[0041]

[0042] Where E r represents the radial component of the core electric field, E φ represents the angular component of the electric field in the core, H r represents the radial component of the magnetic field, H φ represents the angular component of the magnetic field, I represents the radial intensity component of the cladding, It represents the normalized constant of the core guided mode characterized by a total energy of 1W, J0 is the first-kind Bessel function of order 0, V is the normalized cutoff frequency, b is the normalized effective refractive index of the fiber guided mode, β is the propagation constant, a is the core radius that meets the physical boundary conditions, φ is the phase value, ω is the frequency value, i is the imaginary unit, t is the time, and z represents the axial component of the fiber.

[0043] in, Its expression is:

[0044]

[0045] Where Z0 is the wave impedance of electromagnetic waves in vacuum, Δ is the normalized difference in refractive index between the core and cladding, J1 is the first-order Bessel function of the first kind, n2 is the refractive index of the cladding, V is the normalized cutoff frequency, and b is the normalized effective refractive index of the fiber guided mode.

[0046] Long-period fiber grating realizes the coupling between the fundamental mode and the first-order other modes of the same direction transmission, and its phase matching condition is:

[0047]

[0048] In the formula, are the propagation constants of the fundamental mode and the first-order mth mode respectively, and Λ is the grating period. eff / λ, the above formula becomes:

[0049]

[0050] In the formula, is the resonance peak wavelength of the grating, represents the effective refractive index of the fiber Bragg grating core, represents the effective refractive index of the fiber Bragg grating cladding, Λ is the grating period, n eff represents the effective refractive index of the optical fiber, and λ represents the operating wavelength of the optical fiber.

[0051] The influence of temperature field on the optical performance of long-period fiber grating is described by the following formula:

[0052]

[0053] In the formula, Δλ res is the wavelength shift of the long-period fiber grating, λ res is the original wavelength, is the rate of change of the effective refractive index difference with temperature, where n core,eff and n clad,eff denote the effective refractive index of the core and cladding respectively; is the rate of change of the grating period with respect to temperature, also known as the thermal expansion coefficient, Λ is the grating period, ΔT is the temperature change, and T represents the temperature.

[0054] In most cases, the influence of thermo-optic effect on the resonant wavelength drift is much greater than the thermal expansion effect, so the simplified formula is:

[0055] Δλ res ≈λ res α n ΔT

[0056] Among them, the thermal-optical effect coefficient

[0057] On the basis of clarifying the mechanism of long-period fiber Bragg grating regulation of laser transverse modes and establishing the corresponding mathematical analysis model, a corresponding simulation calculation program is compiled. Taking the various parameters of the fiber Bragg grating micro-nano structure (such as structural configuration, grating pitch, number of periods, grating surface inclination, central wavelength, refractive index modulation depth, etc.) as the variable domain, the influence of various fiber Bragg grating parameters on the laser light field amplitude distribution regulation performance is simulated and analyzed, thereby providing design principles, design methods and optimization evaluation of design results for long-period fiber Bragg gratings.

[0058] In order to ensure that the long-period fiber grating can accurately control the mixed mode characteristics of the fundamental mode and other modes when regulating the transverse mode characteristics of the laser light field, it is necessary to consider the grating parameters that are sensitive to the modulation effect of the long-period fiber grating, such as the length of the long-period fiber grating, the refractive index modulation depth, and the half-maximum full width. Using the established mathematical analysis model of the long-period fiber grating to regulate the laser transverse mode, the influence of the long-period fiber grating structural parameters (grating pitch and tilt angle) on the core transverse mode characteristics, cladding transverse mode characteristics, and the mixed mode characteristics of the two when modulating the laser transverse mode characteristics is quantitatively analyzed. Then, in this mathematical model, the grating parameters that are sensitive to the modulation effect (long-period fiber grating length, refractive index modulation depth, half-maximum full width, etc.) are used for analysis and calculation adjustment, so as to achieve the effect of accurately constructing the optical energy structure composed of the laser core transverse mode and the cladding transverse mode. Finally, the precise regulation of the laser mixed mode transverse mode characteristics is guaranteed, and the optimal structural parameters and physical parameters of the long-period fiber grating are obtained.

[0059] The above-mentioned function of the change of the structural parameters of the long-period fiber grating when subjected to the temperature field is a function of the change of the structural parameters (grating pitch and tilt angle) of the long-period fiber grating when subjected to the temperature field, which is calculated based on the thermal expansion coefficient of the optical fiber. It is necessary to calculate the influence of the temperature field on the optical fiber refractive index (core and cladding refractive index) according to the thermo-optical effect, and introduce the change of the structural parameters and the change of the optical fiber refractive index into the established mathematical analysis model of the long-period fiber grating regulating the amplitude distribution of the laser light field, and then establish the function of the change of the structural parameters of the long-period fiber grating when subjected to the temperature field. Then, according to the amplitude distribution regulation requirements of the laser light field, the temperature field parameters that need to be applied can be quantitatively calculated.

[0060] Go to step 3.

[0061] Step 3, start the high-power laser, couple the laser to the second QBH connector and output it after passing through the high-power laser shutter, and at the same time, according to the mathematical analysis model of the long-period fiber grating regulating the laser light field amplitude distribution, and the function of the change of the structural parameters of the long-period fiber grating when it is affected by the temperature field, the computer obtains the TEC control parameters required for the target laser light field amplitude distribution, and proceeds to step 4.

[0062] Step 4: The computer adjusts the TEC temperature according to the obtained TEC control parameters, applies a temperature field to the long-period fiber grating, realizes the regulation of the structural parameters, affects the spot distribution effect by changing the structural parameters, and finally achieves the target amplitude distribution.

[0063] In order to verify the effect of real-time dynamic regulation of the amplitude distribution of the laser light field output by the high-power laser shutter proposed in the present invention, it is necessary to build a test system and establish a specific application scheme of the laser two-dimensional light field amplitude distribution regulation method based on long-period fiber grating according to the laser light field amplitude distribution feedback from the CCD and the power results measured by the power meter. Figure 3 and Figure 4 It shows that after the control of this method, the final output beam successfully transforms from a Gaussian beam to a ring beam, which verifies the feasibility of this method and shows that the method of real-time dynamic control of the amplitude of the multi-station light field of the high-power laser light gate can successfully achieve the requirements of real-time control of the output laser light field amplitude distribution in multiple fields. In the later stage, it is necessary to optimize the proposed method of laser light field amplitude distribution control based on long-period fiber gratings according to the evaluation results, and evaluate the stability and reliability of the developed method of real-time dynamic control of the amplitude of the multi-station light field of the high-power laser light gate.

Claims

1. A method for realizing real-time dynamic control of the amplitude of a high-power laser shutter multi-station light field, characterized in that: The long-period fiber grating (FBG) capable of adjusting the amplitude distribution of high-power laser is integrated into the QBH connector at the output end of the laser shutter. By matching the different requirements of each workstation for amplitude distribution, the resonant wavelengths of different amplitude distribution modes are matched with the working wavelength of the high-power laser connected to the input end of the laser shutter. The long-period fiber gratings at different workstations couple part of the fundamental mode of the laser output by the original laser to other modes, realizing different laser amplitude outputs at multiple workstations. The temperature field is applied to the long-period fiber grating through computer-controlled TEC, and the structural parameters of the long-period fiber grating are regulated, ultimately achieving real-time dynamic regulation of the amplitude distribution of high-power laser.

2. A method for realizing real-time dynamic control of multi-station light field amplitude of high-power laser shutter according to claim 1, characterized in that: Here are the steps: Step 1, build a device, including a main control computer, a high-power laser, a high-power laser shutter, a first QBH connector, and a second QBH connector. The second QBH connector uses a QBH connector that integrates a long-period fiber grating and a temperature-controlled TEC. The high-power laser is connected to the high-power laser shutter through the first QBH connector. The second QBH connector is connected to different output stations of the high-power laser shutter. The main control computer is connected to the TEC and the high-power laser shutter respectively to achieve time-sharing and energy-sharing output of lasers at different stations and dynamic regulation of laser amplitude at different stations; proceed to step 2; Step 2: Establish a mathematical analysis model for the amplitude distribution of the laser light field regulated by the long-period fiber grating, and a function of the change of the structural parameters of the long-period fiber grating when it is subjected to the temperature field, and then proceed to step 3; Step 3, start the high-power laser, couple the laser to the second QBH connector after passing through the high-power laser shutter and output it, and at the same time, according to the mathematical analysis model of the long-period fiber grating regulating the laser light field amplitude distribution and the change function of the structural parameters of the long-period fiber grating when it is subjected to the temperature field, the computer obtains the TEC control parameters required for the target laser light field amplitude distribution, and then proceeds to step 4; Step 4: The computer adjusts the TEC temperature according to the obtained TEC control parameters, applies a temperature field to the long-period fiber grating, realizes the regulation of the structural parameters, affects the spot distribution effect by changing the structural parameters, and finally achieves the target amplitude distribution.

3. A method for realizing real-time dynamic control of optical fiber laser light field amplitude according to claim 1, characterized in that: In step 2, the mathematical analysis model of the long-period fiber grating regulating the laser light field amplitude distribution is as follows: In the formula, E r represents the radial component of the core electric field, E φ represents the angular component of the electric field in the core, H r represents the radial component of the magnetic field, H φ represents the angular component of the magnetic field, I represents the radial intensity component of the cladding, represents the normalized constant of the core guided mode characterized by a total energy of 1W, J0 is the first-order Bessel function of 0th order, V is the normalized cutoff frequency, b is the normalized effective refractive index of the fiber guided mode, β is the propagation constant, a is the core radius that meets the physical boundary conditions, φ is the phase value, ω is the frequency value, i is the imaginary unit, t is the time, z represents the fiber axial component; Re represents the real part of the result; in, Its expression is: Where Z0 is the wave impedance of electromagnetic waves in vacuum, Δ is the normalized refractive index difference between the core and cladding, J1 is the first-order Bessel function of the first kind, n2 is the cladding refractive index, V is the normalized cutoff frequency, and b is the normalized effective refractive index of the fiber guided mode; Long-period fiber grating realizes the coupling between the fundamental mode and the first-order other modes of the same direction transmission, and its phase matching condition is: In the formula, is the propagation constant of the fundamental mode, is the propagation constant of the first-order mth other mode, Λ is the grating period; from β = 2πn eff / λ, the above formula becomes: In the formula, is the resonance peak wavelength of the grating, represents the effective refractive index of the fiber Bragg grating core, represents the effective refractive index of the fiber Bragg grating cladding, Λ is the grating period, n eff represents the effective refractive index of the optical fiber, and λ represents the operating wavelength of the optical fiber.

4. The method for realizing real-time dynamic control of the optical fiber laser light field amplitude according to claim 1, characterized in that: When a long-period fiber grating is subjected to a temperature field, the functional form of the change in its structural parameters is calculated through the thermal expansion coefficient of the optical fiber, and then the change law of the grating pitch and tilt angle of the long-period fiber grating under the action of the temperature field is obtained; by introducing the change in the structural parameters and the temperature dependence of the optical fiber refractive index into the established mathematical model of the long-period fiber grating for regulating the amplitude distribution of the laser light field, the precise relationship between the amplitude distribution characteristics of the laser light field regulated by the long-period fiber grating and the externally imposed dynamic temperature field is established; based on the control requirements of the laser light field amplitude distribution, the mathematical model and its change function are used to quantitatively analyze and calculate the specific parameters for controlling the temperature field.

5. A method for realizing real-time dynamic control of optical fiber laser light field amplitude according to claim 4, characterized in that: The influence of temperature field on the optical performance of long-period fiber grating is described by the following formula: In the formula, Δλ res is the wavelength shift of the long-period fiber grating, λ res is the original wavelength, is the rate of change of the effective refractive index difference with temperature, where n core,eff and n clad,eff denote the effective refractive index of the core and cladding respectively; is the rate of change of the grating period to temperature, also known as the thermal expansion coefficient, Λ is the grating period, ΔT is the temperature change, and T represents the temperature; Since in most cases, the influence of the thermo-optic effect on the resonant wavelength drift is much greater than the thermal expansion effect, the formula is simplified: Dl res ≈λ res ·a n ·ΔT Among them, the thermal-optical effect coefficient

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