Femtosecond laser multi-focus parallel processing method, device and fiber grating writing method

Abstract

The present invention provides a femtosecond laser multi-focus parallel processing method, device and fiber grating writing method, which superimposes multiple blazed grating template holograms on a spatial light modulator to divide a beam of femtosecond laser into multiple beams of femtosecond laser with the same characteristics, and each split beam of light has the same phase, diameter and other information as the femtosecond laser before splitting. After focusing through an objective lens, the focus of each femtosecond laser on the focal plane also has the same size and focal depth as the original femtosecond laser focus. In addition, each femtosecond laser is only affected by the corresponding blazed grating template. By adjusting the corresponding blazed grating template, the phase information of a certain femtosecond laser can be adjusted separately, thereby changing the phase, position, morphology and other parameters of a single femtosecond laser, realizing the processing of a micro-nano structure with a long uniform modified area along the propagation direction of the femtosecond laser, realizing multi-focus parallel processing, and can be applied to the processing of fiber gratings, etc.

Description

Technical Field

[0001] The present invention mainly relates to the field of optical fiber laser technology, in particular to a femtosecond laser multi-focus parallel processing method and device and an optical fiber grating writing method. Background Art

[0002] Femtosecond laser processing technology is widely used in the processing of micro-nano structures and micro-devices because it can process with high precision and high resolution and can process almost any material. However, traditional femtosecond laser micro-nano processing technology has only one focus, which is huge in time cost and low production efficiency when preparing large-scale micro-nano structure arrays.

[0003] The femtosecond laser can be divided into multiple beams by using a microlens array or a diffractive optical element. After being focused by an objective lens or a lens, a focus array can be obtained in the focal plane, thereby processing multiple micro-nano structures at the same time, which is an effective way to process efficiently. However, the disadvantages of this method are that the focus distribution form is fixed, the processing structure is single, and the flexibility is poor. The spatial light modulator (SLM) is a diffractive optical element that can modulate the light wavefront. The liquid crystal unit modulates the phase delay of each pixel to simulate various optical elements. It can flexibly control the phase, amplitude and other parameters of the spatial light field. Therefore, the use of SLM can easily achieve flexible and adjustable multi-focus parallel processing.

[0004] At present, multi-focus parallel processing technology based on spatial light modulator (SLM) has been widely used in the field of additive manufacturing. The Gerchberg-Saxton algorithm and its derivative algorithms are used to generate multi-focus. The algorithm uses the focus array image of the target to reversely calculate the hologram loaded on the spatial light modulator. Although this method can produce an array with a large number of focuses, it is essentially to produce a dot matrix inside or on the surface of the material to be processed by coherent superposition. Therefore, the phase of each beam of split light is disordered, and the phase of each beam of light cannot be controlled. It is difficult to process micro-nano structures with a long uniform modified area along the propagation direction of the femtosecond laser, which limits the application of multi-focus parallel processing. Summary of the invention

[0005] In view of the technical problems existing in the prior art, the present invention provides a femtosecond laser multi-focus parallel processing method, device and fiber grating writing method.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] In one aspect, the present invention provides a femtosecond laser multi-focus parallel processing method, comprising the following steps:

[0008] Determine the materials to be processed;

[0009] Determine the number of focal points required , superimposed on the spatial light modulator A blazed grating template hologram, which produces the The period of the blazed grating template hologram with a focal point With The distance of each focal point from the initial focal point Negatively correlated; Rotation angle of the blazed grating template with 1 focus By The deflection angle of each focus relative to the initial focus is determined;

[0010] Determine the position, size range and distribution characteristics of the modified area array in the material to be processed inside or on the surface of the material to be processed, and determine the size and shape of each array unit constituting the modified area array;

[0011] Determine the displacement speed of the material to be processed according to the shape of each array unit in the modified zone array and displacement path ;

[0012] According to the properties of the material to be processed and the modified area array along Axial length Determining the average power of the femtosecond laser and the beam diameter of the femtosecond laser ;

[0013] determining an initial processing position of an array of modified regions of a material to be processed;

[0014] Average Power , beam diameter The horizontally polarized femtosecond laser is incident into the spatial light modulator from the horizontal direction for phase modulation, and the femtosecond laser reflected from the spatial light modulator is reflected to Axis direction, from The material to be processed is incident in the axial direction and focused on the inside or surface of the material to be processed, so that the initial focus is focused on the initial processing position; the material to be processed is controlled at a speed Along the displacement path The movement is performed to complete the processing having the shape of the modified area array.

[0015] In one embodiment, a spatial light modulator is superimposed on the A blazed grating template hologram is created as follows:

[0016] The period of the blazed grating template hologram according to each focus and the rotation angle of the blazed grating template Generate all the blazed grating template holograms waiting to be superimposed ;

[0017] All the shining grating template holograms waiting to be superimposed Superposition, the phase distribution of the hologram obtained after superposition It is expressed as:

[0018] ;

[0019] ;

[0020] in Indicates Blazed grating template hologram to ensure that the power of each focus is equal.

[0021] In one embodiment, a spatial light modulator is superimposed on the A blazed grating template hologram is created as follows:

[0022] The period of the blazed grating template hologram according to each focus and the rotation angle of the blazed grating template Generate all the blazed grating template holograms waiting to be superimposed ;

[0023] All the shining grating template holograms waiting to be superimposed Superposition, the phase distribution of the hologram obtained after superposition It is expressed as:

[0024] ;

[0025] ;

[0026] in Indicates Blazed grating template hologram to ensure that the power of each focus is equal.

[0027] On the other hand, the present invention provides a device for implementing the above-mentioned femtosecond laser multi-focus parallel processing method, comprising:

[0028] A femtosecond laser, used for outputting femtosecond laser;

[0029] An attenuator, used for controlling the femtosecond laser power output by the femtosecond laser;

[0030] Polarization beam splitter prism, used to modulate femtosecond laser into horizontal linear polarized light;

[0031] A collimator and beam expander is used to collimate and expand the femtosecond laser output from the polarization beam splitter prism, so that the femtosecond laser can occupy the modulation area of ​​the spatial light modulator to the maximum extent while ensuring that the light spot does not overflow the modulation area of ​​the spatial light modulator;

[0032] A reflecting mirror, used for reflecting the femtosecond laser output from the collimating beam expander to the spatial light modulator;

[0033] A spatial light modulator is used to phase modulate the incident femtosecond laser and simulate a hologram obtained by superimposing multiple blazed grating template holograms to generate multiple beams of phase-controllable femtosecond lasers to form multiple focal points;

[0034] A dichroic mirror, used to reflect the femtosecond laser emitted by the spatial light modulator;

[0035] An aperture, used to filter out stray light in the femtosecond laser emitted by the spatial light modulator and control the beam diameter of the femtosecond laser;

[0036] The objective lens is used to focus the femtosecond laser emitted through the aperture on the inside or surface of the material to be processed. The material to be processed is fixedly mounted on the electric displacement platform, and the electric displacement platform controls the material to be processed to move precisely.

[0037] Furthermore, the above device also includes a camera, which is arranged on the transmission light path of the dichroic mirror. The illumination light of the camera is transmitted through the dichroic mirror, and the processing process of the femtosecond laser multi-focus parallel processing is observed in real time through the camera.

[0038] Compared with the prior art, the technical effect of the present invention is: superimposing a spatial light modulator A blazed grating template hologram is used to split a femtosecond laser beam into multiple femtosecond laser beams with the same characteristics. Each laser beam has the same parameters as the femtosecond laser before beam splitting except for power, and each split beam will not interfere with other split beams in the back focal plane, that is, each split beam has the same phase, diameter and other information as the femtosecond laser before beam splitting. After focusing through the objective lens, the focus of each femtosecond laser beam on the focal plane also has the same size and focal depth as the original femtosecond laser focus. In addition, each femtosecond laser beam is only affected by the corresponding blazed grating template. By adjusting the corresponding blazed grating template, the phase information of a femtosecond laser beam can be adjusted separately, thereby changing the phase, position, morphology and other parameters of a single femtosecond laser beam, realizing the processing of micro-nano structures with a long uniform modified area along the propagation direction of the femtosecond laser, and realizing multi-focus parallel processing, which can be applied to the processing of fiber gratings, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0040] Figure 1 This is a schematic diagram of the structure of a femtosecond laser multi-focus parallel processing device according to an embodiment;

[0041] Figure 2 A schematic diagram of superimposing multiple blazed grating templates;

[0042] Numbers in the figure:

[0043] 1. Femtosecond laser; 2. Attenuator; 3. Polarization beam splitter; 4. Collimation beam expander; 5. Reflector; 6. Spatial light modulator; 7. Camera; 8. Dichroic mirror; 9. Aperture; 10. Objective lens; 11. Electric displacement platform.

[0044] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Reference Figure 1 , is a schematic structural diagram of a femtosecond laser multi-focus parallel processing device provided by an embodiment, comprising:

[0047] A femtosecond laser 1, used for outputting femtosecond laser;

[0048] Attenuator 2 is used to control the femtosecond laser power output by the femtosecond laser. Specifically, the average power of the femtosecond laser is determined according to the properties of the material to be processed and the length of the modified area along the z-axis direction. ;

[0049] A polarization beam splitter prism 3, used for modulating the femtosecond laser into horizontal linear polarized light;

[0050] The collimator and beam expander 4 is used to collimate and expand the femtosecond laser output from the polarization beam splitter prism, so that the femtosecond laser can occupy the modulation area of ​​the spatial light modulator to the maximum extent under the premise of ensuring that the light spot does not overflow the modulation area of ​​the spatial light modulator;

[0051] A reflector 5, used for reflecting the femtosecond laser outputted by the collimating beam expander to the spatial light modulator 6;

[0052] The spatial light modulator 6 is used to phase modulate the incident femtosecond laser and simulate a hologram obtained by superimposing multiple blazed grating template holograms to generate multiple beams of phase-controllable femtosecond lasers to form multiple focal points. n In the case of n A blazed grating template hologram, which produces the i The period of the blazed grating template hologram with a focal point By i The distance of each focal point from the initial focal point Negatively correlated; i Rotation angle of the blazed grating template with 1 focus By i The angle of deviation of each focus relative to the initial focus is determined.

[0053] The dichroic mirror 8 is used to reflect the femtosecond laser emitted by the spatial light modulator 6 .

[0054] The camera 7 is arranged on the transmission light path of the dichroic mirror 8. The illumination light of the camera 7 is transmitted through the dichroic mirror 8. The processing process of the femtosecond laser multi-focus parallel processing is observed in real time through the camera 7.

[0055] Aperture 9, the femtosecond laser reflected by the dichroic mirror 8 is emitted through the aperture 9, and the aperture 9 is used to filter out stray light in the femtosecond laser emitted by the spatial light modulator, and at the same time control the beam diameter of the femtosecond laser;

[0056] The objective lens 10 is used to focus the femtosecond laser emitted through the aperture 9 on the inside or surface of the material to be processed. The material to be processed is fixedly mounted on the electric displacement platform 11, and the electric displacement platform 11 controls the material to be processed to move precisely.

[0057] In one embodiment, a femtosecond laser multi-focus parallel processing method is provided, comprising:

[0058] Determine the materials to be processed;

[0059] Determine the number of focal points required , superimposed on the spatial light modulator A blazed grating template hologram, which produces the The period of the blazed grating template hologram with a focal point With The distance of each focal point from the initial focal point Negatively correlated; Rotation angle of the blazed grating template with 1 focus By The deflection angle of each focus relative to the initial focus is determined;

[0060] Determine the position, size range and distribution characteristics of the modified area array in the material to be processed inside or on the surface of the material to be processed, and determine the size and shape of each array unit constituting the modified area array;

[0061] Determine the displacement speed of the material to be processed according to the shape of each array unit in the modified zone array and displacement path ;

[0062] According to the properties of the material to be processed and the modified area array along Axial length Determining the average power of the femtosecond laser and the beam diameter of the femtosecond laser ;

[0063] determining an initial processing position of an array of modified regions of a material to be processed;

[0064] Average Power , beam diameter The horizontally polarized femtosecond laser is incident on the spatial light modulator from the horizontal direction. Due to the characteristics of the spatial light modulator, the smaller the incident angle, the stronger the modulation ability of the light beam. Generally, the incident angle is required to be less than 5°. After phase modulation by the spatial light modulator, the femtosecond laser reflected from the spatial light modulator is reflected to Axis direction, from The material to be processed is incident in the axial direction and focused on the inside or surface of the material to be processed, so that the initial focus is focused on the initial processing position; the material to be processed is controlled at a speed Along the displacement path The movement is performed to complete the processing having the shape of the modified area array.

[0065] Blazed grating is a grating with a periodic structure that can diffract the incident light to higher-order directions. By superimposing blazed grating template holograms with different periods and inclinations on the spatial light modulator, the incident light can be divided into multiple beams and diffracted to different positions and directions. At the same time, since each split beam is only modulated by the corresponding blazed grating, each split beam can be independently controlled.

[0066] In one embodiment, the following scheme is adopted to realize superposition on the spatial light modulator A blazed grating template hologram is created as follows:

[0067] The period of the blazed grating template hologram according to each focus and the rotation angle of the blazed grating template Generate all the blazed grating template holograms waiting to be superimposed ;

[0068] All the shining grating template holograms waiting to be superimposed Superposition, the phase distribution of the hologram obtained after superposition It is expressed as:

[0069] (1)

[0070] in Indicates Blazed grating template hologram to ensure that the power of each focus is equal.

[0071] In another embodiment, the following scheme is adopted to realize superposition on the spatial light modulator: A blazed grating template hologram is created as follows:

[0072] The period of the blazed grating template hologram according to each focus and the rotation angle of the blazed grating template Generate all the blazed grating template holograms waiting to be superimposed ;

[0073] All the shining grating template holograms waiting to be superimposed Superposition, the phase distribution of the hologram obtained after superposition It is expressed as:

[0074] (2)

[0075] in Indicates Blazed grating template hologram to ensure that the power of each focus is equal.

[0076] Figure 2 Schematic diagram of superimposing multiple blazed grating templates. In one embodiment, the same set of blazed grating template holograms to be superimposed are superimposed based on formula (1) and formula (2), respectively, wherein the number of blazed grating templates involved in the superposition is 3. Formula (1) indicates that the phase distribution of the hologram after superposition can be obtained by linearly superimposing each blazed grating template hologram. A typical example of the superposition effect is shown in Figure 2 Formula (2) indicates that the phase distribution of the hologram after superposition can be obtained by superimposing each blazed grating template hologram. A typical example of the superposition effect is shown in Figure 2 Shown on the right.

[0077] The femtosecond laser multi-focus parallel processing method and device provided in the above embodiments can realize the writing of fiber gratings.

[0078] In one embodiment, a first fiber grating writing method is provided, comprising:

[0079] Determine the material to be processed, the material to be processed is the optical fiber on which the optical fiber Bragg grating is to be written, the optical fiber is along The axis is fixed horizontally on the electric displacement platform;

[0080] Determine the number of focal points required , superimposed on the spatial light modulator A blazed grating template hologram, which produces the The period of the blazed grating template hologram with a focal point With The distance of each focal point from the initial focal point Negatively correlated; Rotation angle of the blazed grating template with 1 focus By The deflection angle of each focus relative to the initial focus is determined;

[0081] Determine the shape of the refractive index modulation area of ​​the fiber grating to be written, the shape of the refractive index modulation area is rectangular, and the refractive index modulation area of ​​the fiber grating is along The length in the axial direction is , the length along the radial direction of the optical fiber is The length in the axial direction is ;

[0082] Determine the displacement speed of the optical fiber v and a displacement path S, wherein the displacement path S is the refractive index modulation region of the fiber grating along y Length in the axial direction ;

[0083] According to the threshold of the nonlinear effect of the fiber material, the energy distribution of the femtosecond laser beam, and the refractive index modulation area of ​​the fiber Bragg grating, Length in the axial direction , determine the average power of the femtosecond laser and the beam diameter of the femtosecond laser ;

[0084] Determine the position of the refractive index modulation region of the fiber grating to be written in the optical fiber and the initial writing position inside the optical fiber, and move the initial focus to the initial writing position;

[0085] Writing process: (a) Adjusting the period of each blazed grating template hologram , so that the distance between two adjacent focal points in the optical fiber DEqual to the grating period of the written fiber grating ; (b) Turn on the femtosecond laser, average power , beam diameter The horizontally polarized femtosecond laser is incident into the spatial light modulator from the horizontal direction for phase modulation, and the femtosecond laser reflected from the spatial light modulator is reflected to Axis direction, from The incident beam is incident along the axis direction and focused into the inside of the optical fiber, so that the initial focus is focused to the initial writing position, and the remaining focuses are along the The axes are distributed on one or both sides of the initial focus, and the distance between two adjacent foci is , while controlling the fiber along The speed in the negative direction of the axis Moving length , you can write inside the optical fiber The refractive index modulation area, the distance between two adjacent refractive index modulation areas is the grating period ; (c) Turn off the femtosecond laser and control the fiber to move along the positive direction of the y-axis at a speed of v Moving length l 2. Then control the optical fiber to move along the x-axis (i.e. the length direction of the optical fiber) n indivual D length, and return to step (b) until the desired fiber grating is written.

[0086] In the above embodiment of writing fiber grating, a spatial light modulator is superimposed The method of forming a blazed grating template hologram can also be implemented by any of the aforementioned superposition methods, which will not be repeated here.

[0087] In another embodiment, a second fiber grating writing method is provided, comprising the following steps:

[0088] Determine the material to be processed, the material to be processed is the optical fiber on which the optical fiber Bragg grating is to be written, the optical fiber is along The axis is fixed horizontally on the electric displacement platform;

[0089] Determine the number of focal points required , superimposed on the spatial light modulator A blazed grating template hologram, which produces the The period of the blazed grating template hologram with a focal point With The distance of each focal point from the initial focal point Negatively correlated; Rotation angle of the blazed grating template with 1 focus By The deflection angle of each focus relative to the initial focus is determined;

[0090] Determine the shape of the refractive index modulation area of ​​the fiber grating to be written, the shape of the refractive index modulation area is rectangular, and the refractive index modulation area of ​​the fiber grating is along The length in the axial direction is , the length along the radial direction of the optical fiber is The length in the axial direction is ;

[0091] Determine the displacement speed of the optical fiber v and a displacement path S, wherein the displacement path S is the refractive index modulation region of the fiber grating along y Length in the axial direction l 2;

[0092] According to the threshold of the nonlinear effect of the fiber material, the energy distribution of the femtosecond laser beam, and the refractive index modulation area of ​​the fiber Bragg grating, Length in the axial direction , determine the average power of the femtosecond laser and the beam diameter of the femtosecond laser ;

[0093] Determine the position of the refractive index modulation region of the fiber grating to be written in the optical fiber and the initial writing position inside the optical fiber, and move the initial focus to the initial writing position;

[0094] Writing process: (a) Adjusting the period of each blazed grating template hologram L i , so that the distance between two adjacent focal points in the optical fiber D Greater than m The grating period of the written fiber Bragg grating ,in ; (b) Turn on the femtosecond laser, average power , beam diameter The horizontally polarized femtosecond laser is incident into the spatial light modulator from the horizontal direction for phase modulation, and the femtosecond laser reflected from the spatial light modulator is reflected to Axis direction, from The incident beam is incident along the axis direction and focused into the inside of the optical fiber, so that the initial focus is focused to the initial writing position, and the remaining focuses are along the The axes are distributed on one or both sides of the initial focus, and the distance between two adjacent foci is , while controlling the fiber along The speed in the negative direction of the axis Moving length , you can write inside the optical fiber The refractive index modulation area, the distance between two adjacent refractive index modulation areas is the grating period ; (c) Turn off the femtosecond laser and control the fiber to move along the positive direction of the y-axis at a speed ofv move l 2. Then control the fiber to move along the x-axis (i.e. the length direction of the fiber) , return to step (b) until completion m (d) Control the movement of the optical fiber along the x-axis n indivual D length, and return to step (b) until the desired fiber grating is written.

[0095] In the above embodiment of writing fiber grating, a spatial light modulator is superimposed The method of forming a blazed grating template hologram can also be implemented by any of the aforementioned superposition methods, which will not be repeated here.

[0096] The fiber Bragg grating writing methods provided by the above two embodiments are essentially different in terms of the control of the spacing between the focal points. The first fiber Bragg grating writing method is to accurately control the focal spacing to the period of the grating, that is, D= ; The second fiber Bragg grating writing method is to increase the spacing between the focal points, that is, D> , so that multiple grating periods can be accommodated in it. Since the spatial light modulator is provided with phase delay by the liquid crystal molecules therein, the period of the blazed grating is discrete, so the focal spacing is also discrete, so it is impossible to take into account the needs of all grating periods (but by adjusting the working distance, focal length and other parameters of the focusing objective, or adding a lens template to the spatial light modulator, the focal spacing can be scaled to accurately match the grating period, but this will increase the complexity of the system). Therefore, for the case where the grating period just matches the discrete focal spacing, it is more appropriate to use the first fiber Bragg grating writing method. For writing chirped gratings and the grating period does not match the discrete focal spacing, it is more appropriate to use the second fiber Bragg grating writing method.

[0097] As in one embodiment, refer to Figure 2 The number of blazed grating templates involved in the superposition is 3, with periods of 0, 30 and 50 respectively, where the blazed grating template with a period of 0 is the initial focus; the rotation angles are 90°, 90° and 90° respectively. The hologram after superposition using formula (1) is as follows: Figure 2 As shown in the hologram on the left, after the femtosecond laser reflected from the spatial light modulator is focused by a 50-fold long working distance objective lens, three focal points distributed along the x-axis can be introduced inside the 20 / 400 optical fiber, one of which is the initial focus, and the other two focal points are on the same side of the initial focus, and the distance between two adjacent focal points is 2.3 μm. At this time, the first fiber grating writing method provided in the above embodiment can be selected to write periodic fiber gratings.

[0098] For example, in one embodiment, the number of blazed gratings involved in the superposition is 2, with periods of 96 and 96, respectively, and rotation angles of 90° and -90°, respectively. Formula (2) is used to superimpose the hologram. At this time, the initial focus is at the midpoint of the two foci, the energy is 0, and the two foci are distributed on both sides of the initial focus. After the femtosecond laser reflected from the spatial light modulator is focused by a 50-fold long working distance objective lens, two foci distributed along the x-axis can be introduced into the 20 / 400 optical fiber, and the distance between the two foci is 1.5 μm. At this time, the second fiber grating writing method provided in the above embodiment can be selected to write periodic fiber gratings.

[0099] Matters not covered by the present invention are known technologies.

[0100] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0101] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A femtosecond laser multi-focus parallel processing method, characterized in that: include: Determine the materials to be processed; Determine the number of focal points required , superimposed on the spatial light modulator A blazed grating template hologram, which produces the The period of the blazed grating template hologram with a focal point With The distance of each focal point from the initial focal point Negatively correlated; Rotation angle of the blazed grating template with 1 focus By The deflection angle of each focus relative to the initial focus is determined; Determine the position, size range and distribution characteristics of the modified area array in the material to be processed inside or on the surface of the material to be processed, and determine the size and shape of each array unit constituting the modified area array; Determine the displacement speed of the material to be processed according to the shape of each array unit in the modified zone array and displacement path ; According to the properties of the material to be processed and the modified area array along Axial length Determining the average power of a femtosecond laser and the beam diameter of the femtosecond laser ; determining an initial processing position of an array of modified regions of a material to be processed; Average Power , beam diameter The horizontally polarized femtosecond laser is incident on the spatial light modulator from the horizontal direction for phase modulation, and the femtosecond laser reflected from the spatial light modulator is reflected to Axis direction, from The material to be processed is incident in the axial direction and focused on the inside or surface of the material to be processed, so that the initial focus is focused on the initial processing position; the material to be processed is controlled at a speed Along the displacement path The movement is performed to complete the processing having the shape of the modified area array.

2. The femtosecond laser multi-focus parallel processing method according to claim 1, characterized in that: Superposition on the spatial light modulator A blazed grating template hologram is created as follows: The period of the blazed grating template hologram according to each focus and the rotation angle of the blazed grating template Generate all the blazed grating template holograms waiting to be superimposed ; All the shining grating template holograms waiting to be superimposed Superposition, the phase distribution of the hologram obtained after superposition It is expressed as: ； ； in Indicates Blazed grating template hologram to ensure that the power of each focus is equal.

3. The femtosecond laser multi-focus parallel processing method according to claim 1, characterized in that: Superposition on the spatial light modulator A blazed grating template hologram is created as follows: The period of the blazed grating template hologram according to each focus and the rotation angle of the blazed grating template Generate all the blazed grating template holograms waiting to be superimposed ; All the shining grating template holograms waiting to be superimposed Superposition, the phase distribution of the hologram obtained after superposition It is expressed as: ； ； in Indicates Blazed grating template hologram to ensure that the power of each focus is equal.

4. A device for implementing the femtosecond laser multi-focus parallel processing method as claimed in claim 1, characterized in that: include: A femtosecond laser, used for outputting femtosecond laser; An attenuator, used for controlling the femtosecond laser power output by the femtosecond laser; Polarization beam splitter prism, used to modulate femtosecond laser into horizontal linear polarized light; A collimator and beam expander is used to collimate and expand the femtosecond laser output from the polarization beam splitter prism, so that the femtosecond laser can occupy the modulation area of ​​the spatial light modulator to the maximum extent while ensuring that the light spot does not overflow the modulation area of ​​the spatial light modulator; A reflecting mirror, used for reflecting the femtosecond laser output from the collimating beam expander to the spatial light modulator; A spatial light modulator is used to phase modulate the incident femtosecond laser and simulate a hologram obtained by superimposing multiple blazed grating template holograms to generate multiple beams of phase-controllable femtosecond lasers to form multiple focal points; A dichroic mirror, used to reflect the femtosecond laser emitted by the spatial light modulator; An aperture, used to filter out stray light in the femtosecond laser emitted by the spatial light modulator and control the beam diameter of the femtosecond laser; The objective lens is used to focus the femtosecond laser emitted through the aperture on the inside or surface of the material to be processed. The material to be processed is fixedly mounted on the electric displacement platform, and the electric displacement platform controls the material to be processed to move precisely.

5. The device according to claim 4, characterized in that It also includes a camera, which is arranged on the transmission light path of the dichroic mirror. The illumination light of the camera is transmitted through the dichroic mirror, and the processing process of the femtosecond laser multi-focus parallel processing is observed in real time through the camera.

6. A fiber Bragg grating writing method, characterized in that: The following steps are involved: Determine the material to be processed, the material to be processed is the optical fiber on which the optical fiber Bragg grating is to be written, the optical fiber is along The axis is fixed horizontally on the electric displacement platform; Determine the number of focal points required , superimposed on the spatial light modulator A blazed grating template hologram, which produces the The period of the blazed grating template hologram with a focal point With The distance of each focal point from the initial focal point Negatively correlated; Rotation angle of the blazed grating template with 1 focus By The deflection angle of each focus relative to the initial focus is determined; Determine the shape of the refractive index modulation area of ​​the fiber grating to be written, the shape of the refractive index modulation area is rectangular, and the refractive index modulation area of ​​the fiber grating is along The length in the axial direction is , the length along the radial direction of the optical fiber is The length in the axial direction is ; Determine the displacement speed of the optical fiber v and a displacement path S, wherein the displacement path S is the refractive index modulation region of the fiber grating along y Length in the axial direction ; According to the threshold of the nonlinear effect of the fiber material, the energy distribution of the femtosecond laser beam, and the refractive index modulation area of ​​the fiber Bragg grating, Length in the axial direction , determine the average power of the femtosecond laser and the beam diameter of the femtosecond laser ; Determine the position of the refractive index modulation region of the fiber grating to be written in the optical fiber and the initial writing position inside the optical fiber, and move the initial focus to the initial writing position; Writing process: (a) Adjusting the period of each blazed grating template hologram , so that the distance between two adjacent focal points in the optical fiber D Equal to the grating period of the written fiber grating ; (b) Turn on the femtosecond laser, average power , beam diameter The horizontally polarized femtosecond laser is incident on the spatial light modulator from the horizontal direction for phase modulation, and the femtosecond laser reflected from the spatial light modulator is reflected to Axis direction, from The incident beam is incident along the axis direction and focused into the inside of the optical fiber, so that the initial focus is focused to the initial writing position, and the remaining focuses are along the The axes are distributed on one or both sides of the initial focus, and the distance between two adjacent foci is , while controlling the fiber along The speed in the negative direction of the axis Moving length , you can write inside the optical fiber The refractive index modulation area, the distance between two adjacent refractive index modulation areas is the grating period ; (c) Turn off the femtosecond laser and control the fiber to move along the positive direction of the y-axis at a speed of v Moving length , and then control the fiber along x Axis movement n indivual D length, and return to step (b) until the desired fiber grating is written.

7. The fiber Bragg grating writing method according to claim 6, characterized in that: Superposition on the spatial light modulator A blazed grating template hologram is created as follows: The period of the blazed grating template hologram according to each focus and the rotation angle of the blazed grating template Generate all the blazed grating template holograms waiting to be superimposed ; All the shining grating template holograms waiting to be superimposed Superposition, the phase distribution of the hologram obtained after superposition It is expressed as: ； ； in Indicates Blazed grating template hologram to ensure that the power of each focus is equal.

8. The fiber Bragg grating writing method according to claim 6, characterized in that: Superposition on the spatial light modulator A blazed grating template hologram is created as follows: The period of the blazed grating template hologram according to each focus and the rotation angle of the blazed grating template Generate all the blazed grating template holograms waiting to be superimposed ; All the shining grating template holograms waiting to be superimposed Superposition, the phase distribution of the hologram obtained after superposition It is expressed as: ； ； in Indicates Blazed grating template hologram to ensure that the power of each focus is equal.

9. A fiber Bragg grating writing method, characterized in that: The following steps are involved: Determine the material to be processed, the material to be processed is the optical fiber on which the optical fiber Bragg grating is to be written, the optical fiber is along The axis is fixed horizontally on the electric displacement platform; Determine the number of focal points required , superimposed on the spatial light modulator A blazed grating template hologram, which produces the The period of the blazed grating template hologram with a focal point With The distance of each focal point from the initial focal point Negatively correlated; Rotation angle of the blazed grating template with 1 focus By The deflection angle of each focus relative to the initial focus is determined; Determine the shape of the refractive index modulation area of ​​the fiber grating to be written, the shape of the refractive index modulation area is rectangular, and the refractive index modulation area of ​​the fiber grating is along The length in the axial direction is , the length along the radial direction of the optical fiber is The length in the axial direction is ; Determine the displacement speed of the optical fiber v and a displacement path S, wherein the displacement path S is the refractive index modulation region of the fiber grating along y Length in the axial direction ; According to the threshold of the nonlinear effect of the fiber material, the energy distribution of the femtosecond laser beam, and the refractive index modulation area of ​​the fiber Bragg grating, Length in the axial direction , determine the average power of the femtosecond laser and the beam diameter of the femtosecond laser ; Determine the position of the refractive index modulation region of the fiber grating to be written in the optical fiber and the initial writing position inside the optical fiber, and move the initial focus to the initial writing position; Writing process: (a) Adjusting the period of each blazed grating template hologram , so that the distance between two adjacent focal points in the optical fiber D Greater than m The grating period of the written fiber Bragg grating ,in ; (b) Turn on the femtosecond laser, average power , beam diameter The horizontally polarized femtosecond laser is incident on the spatial light modulator from the horizontal direction for phase modulation, and the femtosecond laser reflected from the spatial light modulator is reflected to Axis direction, from The incident beam is incident along the axis direction and focused into the inside of the optical fiber, so that the initial focus is focused to the initial writing position, and the remaining focuses are along the The axes are distributed on one or both sides of the initial focus, and the distance between two adjacent foci is , while controlling the fiber along The speed in the negative direction of the axis Moving length , you can write inside the optical fiber The refractive index modulation area, the distance between two adjacent refractive index modulation areas is the grating period ; (c) Turn off the femtosecond laser and control the fiber to move along the positive direction of the y-axis at a speed of v move , and then control the fiber to move along the x-axis , return to step (b) until completion m (d) Control the movement of the optical fiber along the x-axis n indivual D length, and return to step (b) until the desired fiber grating is written.

10. The fiber Bragg grating writing method according to claim 9, characterized in that: Superposition on the spatial light modulator A blazed grating template hologram is created as follows: The period of the blazed grating template hologram according to each focus and the rotation angle of the blazed grating template Generate all the blazed grating template holograms waiting to be superimposed ; All the shining grating template holograms waiting to be superimposed Superposition, the phase distribution of the hologram obtained after superposition It is expressed as: ； ； in Indicates Blazed grating template hologram to ensure that the power of each focus is equal.

11. The fiber Bragg grating writing method according to claim 9, characterized in that: Superposition on the spatial light modulator A blazed grating template hologram is created as follows: The period of the blazed grating template hologram according to each focus and the rotation angle of the blazed grating template Generate all the blazed grating template holograms waiting to be superimposed ; All the shining grating template holograms waiting to be superimposed Superposition, the phase distribution of the hologram obtained after superposition It is expressed as: ； ； in Indicates Blazed grating template hologram to ensure that the power of each focus is equal.

Images