A method for processing a multi-focal microlens array

Abstract

The application discloses a kind of processing methods of multi-focal microlens array, belong to laser application technical field.The purpose of the present application is to solve the problem of traditional plane microlens array only single focal length, low processing efficiency and great processing difficulty;The method is obtained by spatial shaping to ultrafast laser in the quartz inside different focal depth multi-focal array, realize different depth in quartz glass inside ablation.After being ablated quartz glass is etched by hydrofluoric acid solution, utilize the characteristics of ablation point depth in quartz, prepare the microlens array of different focal length on quartz surface.The advantage of the method is high processing efficiency, structure morphology controllable, high processing quality, and the ratio of maximum focal length and minimum focal length of sub-lens can satisfy the demand of microlens array in different application occasions.

Description

Technical Field

[0001] This invention relates to a method for fabricating a multifocal microlens array, belonging to the field of laser application technology. Background Technology

[0002] Planar microlens arrays are integrated, miniaturized, and lightweight optical components with important applications in optical imaging, wavefront sensing, refractive index detection, and parallel laser processing. However, traditional planar microlens arrays have identical optical parameters for each sub-lens, resulting in imaging on the same focal plane, making it difficult to achieve imaging on multiple focal planes. Furthermore, regarding beam homogenization, the coherence of the laser beam leads to interference issues when using traditional microlens arrays to homogenize Gaussian beams, reducing beam uniformity. This method typically requires the use of diffusers to reduce beam coherence and improve beam uniformity.

[0003] Multifocal-length microlens arrays show promising applications in tilt detection, microfluidic chips, and high-quality beam homogenization. By using multifocal-length planar microlens arrays, changes in the longitudinal position of objects can be observed, overcoming the limitation of traditional microlens arrays having a single observation surface. Furthermore, existing literature reports that random microlenses with multiple focal lengths are more effective in improving the uniformity of homogenized beams. Therefore, multifocal-length planar microlens arrays can further broaden the applications of traditional planar microlens arrays.

[0004] Traditional fabrication methods for planar microlens arrays mainly include mechanical grinding, inkjet printing, soft lithography, thermal reflow, and ultrafast laser processing. Mechanical grinding and thermal reflow are primarily used for fabricating microlens arrays with a single focal length and are difficult to apply to multifocal microlens arrays. While inkjet printing and soft lithography can efficiently fabricate multifocal microlens arrays, they are mainly designed for processing polymer materials, and polymer-based microlens arrays are difficult to use under harsh conditions.

[0005] For high-temperature resistant fused silica-based planar microlens arrays, ultrafast laser processing is a highly precise and flexible method. For high-temperature resistant fused silica, there are two main ultrafast laser processing methods: ultrafast laser ablation and ultrafast laser-assisted chemical etching (LAC). Ultrafast laser ablation utilizes a focused Gaussian beam for point-by-point scanning to control the surface shape of the microlenses. Ultrafast LAC, on the other hand, uses an ultrafast laser to locally ablate the fused silica, followed by chemical etching to fabricate the microlenses. However, both methods primarily rely on a single Gaussian beam, resulting in low processing efficiency and hindering the simultaneous control of multiple microlens surfaces. Furthermore, traditional methods struggle to fabricate multi-focal-length microlens arrays with large focal length ratios on a single substrate. Summary of the Invention

[0006] (I) Existing Problems

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to solve the problems of low processing efficiency and surface shape control in traditional quartz-based planar microlens arrays, and to achieve the integration of microlens arrays with multiple focal lengths on the same quartz substrate.

[0008] (II) Technical Solution

[0009] This invention proposes a spatially shaped ultrafast laser-assisted chemical etching method. A Gaussian beam is shaped into a multifocal array with different focal depths using a spatial light modulator. This shaped beam is then used to ablate at different depths within the quartz. Subsequently, the ablated sample is placed in a hydrofluoric acid solution for ultrasonic-assisted etching. Because the ablation regions are located at different depths within the quartz, the internal ablation is only exposed on the quartz surface when the quartz thickness is reduced to a certain value. By utilizing the time difference in etching at each ablation point, the final morphology of each sub-lens can be controlled. This allows for the integration of microlens arrays with different focal lengths on the same quartz substrate. This method offers high processing precision, high efficiency, and a wide adjustable focal length range for each sub-lens.

[0010] A method for fabricating a multifocal microlens array, the technical solution of which is as follows:

[0011] S1: Determine the number of focal points for the ultrafast laser in shaping, and the focusing depth z. i The spacing d of multiple focal points i The refractive index n of the quartz glass, and the focal length f of the beam-constricting system lenses f1 and f2, and the focal length f of the objective lens. objective The desired phase hologram is obtained by iteratively calculating the target light field using a computational holographic algorithm, such as the Optimal Rotation Angle (ORA) algorithm. To control the depth of focus at each focal point, a spherical phase is superimposed on each focal point during the iteration process. The focal depth (FD) of each focal point can be represented as follows:

[0012]

[0013] Where k represents the wave number and ρ represents the radius of the polar coordinates.

[0014]

[0015] Spacing d between multiple focal points i This can be expressed by the following formula:

[0016]

[0017] Where λ represents the wavelength of the ultrafast laser, N represents the number of pixels in the computed hologram, and p represents the physical pixel spacing of the spatial light modulator.

[0018] S2: Superimpose the divergent spherical wave phase onto the hologram described in S1 to achieve separation of the target light field from the zero-order light.

[0019] S3: Construct a processing system consisting of an ultrafast laser, an optical chopper, a beam expander, a half-wave plate, a mechanical shutter, a spatial light modulator, a beam shrinking system, a focusing objective, and a three-dimensional motion platform.

[0020] S4: The phase hologram obtained in S2 is loaded into the spatial light modulator in S3 to shape the Gaussian beam into a multifocal light field. The shaped light field is then focused inside the quartz crystal by the beam-shrinking system and focusing objective.

[0021] S5: The energy and repetition frequency of the shaping beam are adjusted using the ultrafast laser system, and the frequency of the ultrafast laser is further reduced using an optical chopper. Rapid ablation of the quartz interior is achieved through the rapid movement of the motion platform. The pulse energy of a single focal point used for ablation is E. Let the frequency of the optical chopper be f, and the speed of the three-dimensional motion platform be v. Then, by controlling the scanning speed of the motion platform, the quasi-period L of the ablation point array can be controlled. The quasi-period of the ablation point array can be expressed as:

[0022]

[0023] The efficiency of large-area ablation by shaping ultrafast laser can be improved by simultaneously increasing the optical chopper frequency v and the speed f of the three-dimensional motion platform.

[0024] S6: The fused silica sample is placed in a hydrofluoric acid solution, and ultrasonic-assisted etching is used to ensure a complete reaction between the sample and the hydrofluoric acid. During the etching process, the thickness of the fused silica changes by 2z. i At that time, only if the depth inside the quartz before etching does not exceed z i Only the ablation zone is exposed on the upper surface of the quartz. Therefore, ablation points at different depths within the quartz are exposed to the hydrofluoric acid solution only after different etching times. By utilizing the difference in etching time, the morphology of each lens can be controlled. This is achieved by controlling the multifocal focusing depth z described in S1. i By controlling the etching time of each ablation point, the final shape of each sub-lens can be controlled, thereby controlling the focal length of each sub-lens.

[0025] Optical Path: The ultrafast laser system generates pulsed laser light. This pulsed laser light passes perpendicularly through an optical chopper, then incident on the center of a beam expander, a half-wave plate, and a mechanical shutter, at an angle of less than 5° onto the center of a spatial light modulator. The emitted, shaped ultrafast laser light passes through the center of a beam-shrinking system and a focusing objective. The pulse energy and repetition frequency of the ultrafast laser, the frequency of the optical chopper, the motion speed of the three-dimensional motion platform, and the hologram loading and refresh frequency of the spatial light modulator are all controlled by a computer. A dichroic mirror is located between the beam-shrinking system and the objective lens. It illuminates the fused silica from behind using a multi-source light source, feeding back the surface morphology of the fused silica during processing to a charge-coupled device (CCD), enabling real-time monitoring of the processing.

[0026] (III) Beneficial Effects

[0027] The above-described technical solution of the present invention has the following advantages:

[0028] (1) This invention shapes a single Gaussian beam into a multifocal array with different focal depths. By controlling the focal depth of the multifocal points, ablation can be performed at any location inside the quartz. By utilizing the time difference between the etching of each ablation point and the etching with hydrofluoric acid solution, the morphology of each sub-lens can be controlled, thereby integrating a multifocal microlens array on the same quartz substrate. This method offers high processing precision, high flexibility, and high efficiency.

[0029] (2) This invention improves processing efficiency by simultaneously using an optical chopper, a motion platform, and multiple focal points. The improvement in processing efficiency is directly proportional to the frequency of the optical chopper, the speed of the motion platform, and the number of focal points. When the frequency of the optical chopper, the speed of the motion platform, and the number of focal points are appropriate, the processing efficiency can be improved by one to two orders of magnitude.

[0030] (3) The present invention allows for the control of the surface shape of each sub-lens. When the etching time is short, by controlling the depth of focus and etching time of the multi-focal point, concave lenses with different surface shapes, such as spherical lenses, elliptical lenses, parabolic lenses, and hyperboloid lenses, can be integrated on the same quartz substrate. When the etching time is long, spherical lenses with different focal lengths can be integrated on the same surface.

[0031] (4) The present invention can adjust the focal length of each sub-lens over a wide range, from 10.0μm to 130μm as needed, and the focal length is larger than the adjustment range.

[0032] (5) The present invention can adjust the focal distance. When the multifocal distance is small enough, a multifocal microlens array with a filling rate of 100% can be integrated on the quartz surface to improve the light utilization rate of the multifocal microlens array.

[0033] (6) The present invention can encode the depth of each multifocal point to realize the patterning of the multifocal microlens array.

[0034] (7) This invention is not limited to fused silica materials, but can be applied to transparent hard and brittle materials that can be etched by isotropic chemicals, such as K9 glass, borosilicate glass and sulfide glass, and has a wide range of applications. Attached Figure Description

[0035] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0036] Figure 1 This is a schematic diagram of the ultrafast laser processing system for shaping according to the present invention;

[0037] Figure 2 This is a process flow diagram of the present invention;

[0038] Figure 3 This is a schematic diagram of the etching principle of the present invention;

[0039] Figure 4 Microscopic images of the sample at different etching times;

[0040] Figure 5 (a) is a microscope image of an example, (b1) cross-sectional morphology of lens 1, (b2) cross-sectional morphology of lens 2, (b3) cross-sectional morphology of lens 3, and (b4) cross-sectional morphology of lens 4.

[0041] Figure 6 Multifocal length microlens array imaging system.

[0042] Figure 7 Optical imaging diagram of Example 1.

[0043] Figure 8 (a) shows the relationship between the diameter of the four sub-lenses of fused silica after 120 min of etching and the multifocal depth of field spacing Δz. (b) shows the relationship between the height of the four sub-lenses of fused silica after 120 min of etching and the multifocal depth of field spacing Δz.

[0044] Figure 9 (a) shows the relationship between the conicity of the four sub-lenses of fused silica and the multifocal depth of focus Δz after 120 min of etching. (b) shows the relationship between the vertex focal length of the four sub-lenses of fused silica and the multifocal depth of focus Δz after 120 min of etching.

[0045] Figure 10 (a) Multifocal microlens array with 100% fill rate when Δz = 5μm, (b) Multifocal microlens array with 100% fill rate when Δz = 5μm.

[0046] in, Figure 1 1-Ultrafast laser, 21-Optical chopper 1, 22-Optical chopper 2, 3-Beam expander, 4-Mechanical shutter, 5-Half-wave plate, 61-Dielectric mirror 1, 62-Dielectric mirror 2, 7-Phase-type spatial light modulator, 8-Convex lens 1, 9-Convex lens 2, 10-Dichroic mirror, 11-Focusing objective lens, 12-Three-dimensional motion platform, 13-White light source, 14-Convex lens 3, 15-Charge-coupled device.

[0047] in, Figure 6 1-Illumination source, 2-Mask, 3-Multifocal microlens array, 4-Microscopic objective lens, 5-Charge-coupled device. Detailed Implementation

[0048] Example 1

[0049] A method for fabricating a multifocal microlens array based on fused silica includes the following steps:

[0050] S1: Construct the optical path for ultrafast laser shaping, as shown in the attached diagram. Figure 1 As shown, the ultrafast laser 1 has a center wavelength of 532 nm, a pulse width of 10 ps, ​​a repetition frequency of 50 kHz, and a beam waist radius of approximately 1 mm. The 50 kHz is divided into 2.5 kHz by the ultrafast laser. The rotation frequencies of optical choppers 21 and 22 are set, and the phase of the optical choppers is locked, further reducing the ultrafast laser repetition frequency to 50 Hz. After passing through beam expander 3, the ultrafast laser beam radius is expanded to approximately 4.3 mm. The optical path is controlled by mechanical shutter 4. Half-wave plate 5 modulates the polarization direction of the ultrafast laser to horizontal polarization. After passing through mirrors 61 and 62, the ultrafast laser is incident on phase-type spatial light modulator 7 at an angle of less than 5°. After being modulated by spatial light modulator 7, the shaped ultrafast laser passes through lens 8 with a focal length of f1 = 250 mm and lens 9 with a focal length of f2 = 150 mm, and is focused by dichroic mirror 10 to f2 = 250 mm. objective The sample is focused by an 8.126mm objective lens 11. A white light source 13 illuminates the sample, and the sample surface is observed through the objective lens 11, lens 14, and charge-coupled device 15. Precise positioning of the fused silica sample is achieved by controlling the displacement and speed of the three-dimensional motion platform 12.

[0051] S2: Multi-focus design, as shown in the attached image. Figure 2 As shown, the spacing d inside the quartz crystal is designed for a 4×1 multifocal array. i and focus depth z i As attached Figure 2As shown, the distances between the foci are d1 = 100 μm, d2 = 75 μm, and d3 = 50 μm respectively, and the focusing depths of the respective foci are 0, z1 = 15 μm, z2 = 30 μm, and z3 = 45 μm in sequence. △z is the distance between the focal depths of the respective foci, with a size of 15 μm. Based on the focal lengths of the lens and the objective lens described in S1, and the refractive index n = 1.45 of quartz, the corresponding computer-generated hologram is obtained based on the ORA algorithm.

[0052] S3: Load the calculated hologram onto the spatial light modulator 7 described in S1, set the single-pulse energy of each focus to E = 3.0 μJ, and achieve precise ablation of the multi-focus array inside the quartz. The position of the ablation area inside the fused quartz is consistent with the position of the designed multi-foci. The three-dimensional motion platform 12 described in S1 moves at a speed of 5000 μm / s, and the quasi-period of the ablation point array is 100 μm. Through the reciprocating motion of the three-dimensional motion platform 12, the ablation of 1 cm 2 area of fused quartz can be completed within 1 minute.

[0053] S4: Wash the ablated fused quartz glass described in S3 with alcohol and distilled water respectively to remove the dirt on the surface. Place the ablated fused quartz glass in a 20% by mass hydrofluoric acid solution for ultrasonic-assisted etching. After 120 minutes of etching, a microlens array with different morphologies is fabricated on the surface of the fused quartz.

[0054] S5: Attach Figure 3 Further elaborate on the specific process of chemical etching. When the sample etching time 0 < t ≤ t1 = 30 min, structure 1 is etched by hydrofluoric acid; when the sample etching time t1 < t ≤ t2 = 60 min, structure 1 and structure 2 are etched simultaneously by hydrofluoric acid; when the sample etching time t2 < t ≤ t3 = 90 min, structure 1, structure 2, and structure 3 are etched simultaneously by hydrofluoric acid; when the sample etching time t3 < t ≤ t4 = 120 min, structure 1, structure 2, structure 3, and structure 4 are etched simultaneously by hydrofluoric acid. Finally, microlenses with different morphologies are formed on the surface of the fused quartz. Let the diameter of each sub-lens be D i , and the height be H i , then D1 > D2 > D3 > D4 and H1 ≈ H2 ≈ H3 ≈ H4. To further prove the process described in Attach Figure 3 Attach Figure 4 shows the morphology of the sample during the etching process. Among them, structure 1 is etched by hydrofluoric acid from beginning to end, and when t is 30, 60, and 90 min respectively, structures 2, 3, and 4 are successively exposed on the surface of the fused quartz and etched by hydrofluoric acid. Therefore, the etching times of the 4 structures are approximately 120 min, 90 min, 60 min, and 30 min in sequence.

[0055] S6: The morphology of the microlens structure can be fitted using the following formula:

[0056]

[0057] Where K represents the conic coefficient and c represents the vertex curvature, the vertex radius of curvature R can be estimated using the following formula:

[0058]

[0059] The vertex focal length is estimated using the following formula:

[0060]

[0061] Surface morphology was observed using a laser scanning confocal microscope. Figure 5 The display shows a microlens array that integrates four different structures. Figure 5 (b1) to (b4) represent the cross-sectional morphologies of structures 1 to 4, respectively. The conicity coefficients of the four structures are 0.15, -0.55, -1.11, and -1.59, respectively. Structure 1 is closer to a sphere, structure 2 is an ellipsoid, structure 3 is closer to a parabola, and structure 4 is a hyperboloid. The diameters D of these four structures are 87.60, 83.70, 60.16, and 38.12 μm, respectively, and the heights H are 23.02, 27.57, 24.43, and 19.51 μm, respectively. According to formula (6), the vertex radii of curvature are calculated to be 52.26, 34.65, 13.14, and 5.21 μm, respectively, and the corresponding vertex focal lengths are -116.14, -77.00, -29.20, and -11.57 μm, respectively. Therefore, the present invention enables the integration of microlens arrays with different surface shapes and focal lengths on the same fused silica substrate, and the ratio of the maximum focal length to the minimum focal length can reach 10.01.

[0062] S7: Microscopic imaging is performed using the multifocal microlens array described in S3. (Appendix) Figure 6 The optical path for microscopic imaging is shown. Illumination source 1 illuminates mask 2, and the image is observed through multifocal microlens array 3 and microscope objective 4 (10× objective, Nikon). The image is then captured by charge-coupled device 5. (See attached image.) Figure 7 The microscopic imaging effect based on the multifocal length microlens array described in S3 is demonstrated. The imaging system can achieve imaging on multiple focal planes.

[0063] Example 2

[0064] A method for processing multifocal microlens arrays based on fused silica is described, the main steps of which are the same as in Example 1, with the only difference being S2.

[0065] The difference from Example 1 S2 is that the focal depths of each focal point are sequentially 0, z1 = Δz, z2 = 2Δz, and z3 = 3Δz. Δz represents the distance between the focal depths of each focal point, ranging from 0 to 45 μm. (Appendix) Figure 8 This demonstrates the diameter and height of four microlenses with different values ​​of Δz. By changing Δz, the diameter of each microlens can be adjusted, while the height of each microlens remains within a certain range. (Appendix) Figure 9 This demonstrates the conic coefficient and focal length of four microlenses with different values ​​of Δz. By changing Δz, the conic coefficient of each sub-lens can be adjusted, thereby controlling the surface shape of each sub-lens. Simultaneously, the focal length at its vertex can also be adjusted. The adjustment range is 11μm–130μm. Depending on the requirements, as long as Δz is selected appropriately, the surface shape of the microlens can be adjusted to a sphere, ellipsoid, parabola, or hyperboloid.

[0066] Example 3

[0067] The method for achieving a 100% fill rate multifocal microlens array is the same as that in Example 1, with the only difference being S2 and S3:

[0068] S2: Multifocal design, designing a 4×1 multifocal array with a spacing d inside the quartz. i and focus depth z i The focal lengths are d1 = 25 μm, d2 = 25 μm, and d3 = 25 μm, respectively. The focal depths of each focal point are 0, z1 = Δz, z2 = 2Δz, and z3 = 3Δz, respectively. Δz represents the spacing between the focal depths, with values ​​of 5 μm and 10 μm. Based on the focal lengths of the lens and objective lens described in Example 1 S1, and the refractive index of quartz n = 1.45, the corresponding computational hologram is obtained using the ORA algorithm.

[0069] S3: The calculated hologram is loaded into the spatial light modulator 7 described in S1, and the single-pulse energy of each focal point is set to E = 3.5 μJ to achieve precise ablation of the multi-focal array inside the quartz. The position of the ablation area inside the molten quartz coincides with the position of the designed multi-focal points. In Example 1, the three-dimensional motion platform 12 described in S3 moves at a speed of 1250 μm / s, and the quasi-period of the ablation point array is 25 μm. Through the reciprocating motion of the three-dimensional motion platform 12, an ablation of 1 cm can be completed within 53 minutes. 2 Ablation of surface-fused quartz. (See attached image) Figure 10 The image shows a 100% multifocal microlens array prepared in Example 3, wherein... Figure 10 (a) represents the processing result of Δz = 5μm, with appendix. Figure 10 (b) represents the processing result of Δz = 10 μm.

[0070] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating a multifocal microlens array, characterized in that, The specific steps are as follows: S1: Determine the number i of the ultrafast laser multifocal points for shaping, and the focusing depth. Horizontal spacing of multifocal points The refractive index n of the fused silica and the focal lengths of the lens group in the beam-constricting system are respectively... , The focal length of the focusing objective is The required phase hologram is generated using an optimal rotation angle algorithm. To control the depth of focus at each focal point, a spherical phase is superimposed on each focal point during the iteration process. The spherical phase corresponding to each focal point... It can be represented as: (1) Where k represents the wave number and ρ represents the radius of the polar coordinates; Horizontal spacing between multiple focal points This can be expressed by the following formula: (2) Where λ represents the wavelength of the ultrafast laser, N represents the number of pixels in the computed hologram, and p represents the physical pixel spacing of the spatial light modulator; S2: Superimpose the divergent spherical wave phase onto the hologram described in step S1 to achieve separation of the target light field from the zero-order light; S3: Construct a processing system consisting of an ultrafast laser, an optical chopper, a beam expander, a half-wave plate, a mechanical shutter, a spatial light modulator, a beam shrinking system, a focusing objective, and a three-dimensional motion platform; S4: The phase hologram obtained in step S2 is loaded into the spatial light modulator to shape the Gaussian beam into a multifocal light field; the shaped light field is focused inside the fused silica after passing through the beam shrinking system and focusing objective. S5: The energy and repetition frequency of the shaping beam are adjusted using an ultrafast laser system, and the frequency of the ultrafast laser is further reduced using an optical chopper; rapid ablation of the molten silica is achieved by rapidly moving a motion platform; the pulse energy of a single focal point used for ablation is E; assuming the frequency of the optical chopper is f and the speed of the three-dimensional motion platform is v, the quasi-period L of the ablation point array can be controlled by controlling the scanning speed of the motion platform. The quasi-period of the ablation point array can be expressed as: (3) By simultaneously increasing the frequency of the optical chopper and the speed of the three-dimensional motion platform This can improve the efficiency of large-area ablation using ultrafast lasers in plastic surgery. S6: The molten quartz sample to be shaped by ultrafast laser ablation is placed in a hydrofluoric acid solution, and ultrasonic-assisted etching is used to ensure a full reaction between the sample and the hydrofluoric acid; during the etching process, if the change in the thickness of the molten quartz is... Only when the ablation zone is located within the fused silica at a depth not exceeding [a certain value] before etching. Only when the location is specified will the area be exposed to the fused silica surface after etching; therefore, ablation points at different depths within the lens are exposed to the hydrofluoric acid solution only after different etching times; by utilizing the difference in etching time, the morphology of each lens can be controlled; by controlling the multifocal focusing depth described in step S1... By controlling the etching time of each ablation point, the final shape of each sub-lens can be controlled, thereby controlling the focal length of each sub-lens.

2. The fabrication method for a multifocal microlens array according to claim 1, characterized in that, The processing system includes an ultrafast laser system, an optical chopper, a beam expander, a half-wave plate, a mechanical shutter, a spatial light modulator, a beam shrinking system, a focusing objective, a three-dimensional motion platform, a dichroic mirror, a charge-coupled device, a white light source, and a computer control system. The ultrafast laser system generates pulsed lasers, which pass perpendicularly through the optical chopper, incident on the center of the beam expander, half-wave plate, and mechanical shutter, and are incident on the center of the spatial light modulator at an angle of less than 5°. The emitted shaped ultrafast laser passes through the center of the beam shrinking system and the focusing objective. The pulse energy and repetition frequency of the ultrafast laser, the frequency of the optical chopper, the motion speed of the three-dimensional motion platform, and the hologram and hologram refresh frequency of the loaded spatial light modulator are controlled by a computer. A dichroic mirror is located between the beam-shrinking system and the focusing objective lens. A white light source provides back illumination to the molten quartz sample. During the processing, the surface morphology of the sample is fed back to the charge-coupled device via the dichroic mirror to achieve real-time monitoring.

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