Method and device for carrying out back wet etching on fused quartz by using laser with wave band of 300-600nm

Abstract

The invention discloses a method and a device for carrying out back wet etching on fused quartz by using laser with the wave band of 300-600nm, and belongs to the technical field of laser micro-nano processing. According to the method, 532nm laser pulses are focused on the back surface of a transparent fused quartz sample, a light damage area is generated in a contact area of the sample and an acid red No.1 aqueous solution, and the characteristic that the acid red No.1 aqueous solution has high absorptivity on 532nm wavelength laser is utilized, so that local etching of a material is realized under the condition that an absorption layer does not need to be additionally arranged; and finally, forming a circular microstructure on the surface of the fused quartz by taking the light destruction region as the center. The device is made of a polytetrafluoroethylene material and has chemical corrosion resistance, stable liquid level control is achieved through the high-position liquid injection channel, and etching uniformity and repeatability are guaranteed. Compared with a traditional infrared laser etching mode, the method has the advantages that the process is simpler, the microstructure array with clear edges and low surface roughness can be prepared, and the method is suitable for micro-nano machining of optical devices.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laser micro-nano processing, and particularly relates to a method and device for back wet etching of fused quartz by using 300-600 nm waveband laser. BACKGROUND

[0002] Laser-induced back wet etching (LIBWE) is an advanced etching process combining laser heating and chemical reaction, which is widely used in micro-nano processing of high transparent and hard brittle materials such as fused quartz. This technology irradiates laser from the back of the material, which penetrates through the transparent medium and focuses on the front surface, locally generates high temperature heat field, thereby accelerating the reaction of specific area with etching liquid, and realizes high-precision and selective etching of the material. Compared with traditional front irradiation or mechanical etching method, LIBWE has the advantages of non-contact, high resolution and low thermal damage, and has important value in the field of optical device microstructure processing.

[0003] At present, the solution holding device used for LIBWE in experiments is mostly a general container or a simply modified reaction tank. These devices are usually not specially designed for the characteristics of LIBWE process, and have many problems. First, the liquid level is unstable, and the liquid shaking during processing will cause uneven contact between the sample and the etching liquid, thereby affecting the etching depth and pattern consistency. Second, the traditional device often needs to disassemble the sample or the device body when changing the solution, which is complicated and easy to introduce pollution, and the efficiency and repeatability are difficult to guarantee. Third, the material versatility of some devices is poor, and it is difficult to resist the strong corrosive liquid of acid and alkali, which leads to short service life and even leakage or damage during the experiment, increasing the safety risk.

[0004] When using laser to etch, the laser with proper wavelength should be selected to make the sample absorb the incident laser energy well. However, the transmittance of common optical materials, such as calcium fluoride and fused silica, is very high in the near-ultraviolet to near-infrared band, and a high power is needed to remove the sample material, which is often accompanied by severe ablation phenomenon, and the quality of the sample surface after action is poor. Therefore, ultra-short pulse laser or deep / extreme ultraviolet laser can be used. These lasers are usually expensive, so the back surface of the transparent material can be in contact with another medium with high absorption coefficient at the action laser wavelength, thereby increasing the energy deposition of the laser energy at the material surface. According to the state of the medium, it can be divided into: laser-induced plasma assisted ablation (LIPAA), laser etching at a surface-adsorbed layer (LESAL), LIBWE and laser-induced backside dry etching (LIBDE), among which LIBWE and LIBDE are the most studied, and each has its own advantages and disadvantages. When LIBWE uses pure hydrocarbon liquid or mixed solution of hydrocarbon liquid as the absorbing medium (also known as H-LIBWE), it has the advantage of high etching surface quality, but it is affected by the incubation effect, which is not conducive to the accurate control of etching depth, and the device used is relatively complex, and the liquid used is often harmful to human health. In addition, LIBWE can also use liquid metal as the absorbing medium (referred to as M-LIBWE), and the metals used include gallium, mercury, tin, etc. These metals are also harmful to human health, and the sample surface and subsurface layer after action inevitably contain metal elements, which is more troublesome to remove subsequently. Although LIBDE has a high etching rate, its etching depth will be saturated with the consumption of the thickness of the thin film on the back surface.

[0005] For LIBWE, there is no report of using non-toxic solution as absorption medium and using visible light band laser. The acid red No. 1 solution is used in the application, and the etching of the fused quartz sample is carried out by using visible light band laser. The acid red No. 1 solution is non-toxic and harmless, and will not pose a threat to human health. It has good absorption performance in the known 300nm-600nm band, and can be used as an absorption medium in LIBWE. In addition, a solution holding device specially used for LIBWE experiment is also designed. The device is made of polytetrafluoroethylene (PTFE) material, which has excellent chemical corrosion resistance and can adapt to various etching liquids including strong acid or strong base. On the structure, by setting a high solution injection channel at the back of the reaction tank, combined with the principle of height difference, the etching liquid can be replaced and supplemented without disturbing the sample or liquid surface, which fundamentally improves the operation convenience and liquid surface stability. At the same time, the double-layer adjustable clamping structure supports the flexible change of sample thickness, and the sample clamping is firm and reliable, which is convenient for repeated use in multiple experiments. Through integral molding and bonding design, the device has good sealing performance and mechanical stability, which avoids the risk of leakage and system interference in the experiment. SUMMARY

[0006] The application aims at a method and device for LIBWE using 300nm-600nm band laser in acid red solution, to solve the problems of high transmittance of fused quartz under 300nm-600nm band laser, most of the existing etching liquids being harmful to the environment, insufficient contact between the sample and the solution during etching, and shaking of the solution surface.

[0007] In order to achieve the purpose of the application, a method for back wet etching of fused quartz by using 300-600nm band laser is disclosed, which comprises the following steps:

[0008] Step 1, fix the fused quartz sample in the device containing the solution, inject the acid red No. 1 aqueous solution with a temperature of 15-30℃ and a concentration of 1.6-2.0g / L, and make the solution fully contact with the back surface of the sample;

[0009] Step 2, use a nanosecond laser with a pulse width of 6-8ns to output 1064nm laser, convert it to 532nm laser by frequency doubler, and adjust the energy density to 3.569-4.497J / cm 2 ;

[0010] Step 3, the laser is vertically focused on the interface between the back surface of the fused quartz and the solution by a full mirror and a convex lens with a focal length of 100mm;

[0011] Step 4: Control the number of laser pulses to 20 per point, and move the sample at 2mm intervals using a two-dimensional moving platform to process and form a 5×5 rectangular dot matrix microstructure array;

[0012] Step 5: Clean the etched sample with ultrasonic in ethanol for 5 minutes.

[0013] Furthermore, the fused silica is JGS2 fused silica, and the temperature of the Acid Red 1 aqueous solution is 25°C.

[0014] Furthermore, in step 4, the laser energy density is achieved by adjusting the deflection angle of the half-wave plate. The microstructure is circular with a diameter of 105-216 μm, a depth of 0.84-1.08 μm, and a surface roughness of ≤12 nm rms.

[0015] To achieve the objectives of this invention, this invention also discloses an apparatus for wet etching of fused silica on the back side using a laser in the 300-600nm band, comprising a solution holding device and a laser etching device; the solution holding device is used to hold the solution and fix the fused silica sample, and the laser etching device is used to emit laser pulses to etch the fused silica sample, thereby forming a microstructure array on the fused silica sample.

[0016] Furthermore, the solution holding device includes a reaction tank and a base plate; the reaction tank is used to hold the etching solution; the bottom of the reaction tank is provided with a base plate, and the back of the reaction tank is provided with a high-level solution injection channel, the inlet of which is higher than the liquid level in the reaction tank; the upper end of the reaction tank is provided with a double-layer adjustable clamping structure, which includes a clamping plate A and a clamping plate B with a square through hole. Both clamping plate A and clamping plate B are rectangular components with a square opening in the middle, which are fixed to the screw holes around the reaction tank by screws to expose and clamp the fused silica sample. The distance between clamping plate A and clamping plate B is adjustable to accommodate samples of different thicknesses.

[0017] Furthermore, the laser etching device includes a YAG nanosecond laser, a frequency doubler, a dichroic mirror, a tunable continuous attenuator, a total reflection mirror assembly, and a convex lens. The beam emitted by the YAG nanosecond laser is doubled to obtain laser light with half the wavelength, and then selected by the dichroic mirror to obtain visible light in the 300-600nm band. The visible light in the 300-600nm band has its laser energy adjusted by the tunable continuous attenuator composed of a half-wave plate and a beam splitter, and then reflected by the total reflection mirror assembly and vertically focused onto the surface of the fused silica sample by the convex lens. The focused laser pulse acts on the back of the fused silica sample and the surface in contact with the solution, ultimately forming a microstructure array on the fused silica sample.

[0018] Furthermore, the solution holding device is positioned above the two-dimensional moving platform, which can move back and forth and left and right. By moving the two-dimensional moving platform at 2mm intervals, the solution holding device and the fused silica sample are moved, thereby forming a microstructure array on the fused silica sample.

[0019] Furthermore, the spacing between clamping plate A and clamping plate B can be adjusted by replacing the fixing screws with different lengths.

[0020] Furthermore, a corrosion-resistant adhesive is used to seal the reaction tank, bottom plate, and solution injection channel.

[0021] Furthermore, the drain outlet is located on the side of the solution holding device, tangent to the bottom of the solution being held, and is filled with a piston of the same material.

[0022] Compared with existing technologies, the significant advancements of this invention are: 1) This invention utilizes a 532nm laser for laser-induced wet etching of fused silica on the back side, overcoming the problem that fused silica is difficult to process using traditional laser processing due to its high transmittance and low absorption in the visible light band, thus achieving processing of fused silica under a 532nm laser; 2) This invention uses an environmentally friendly Acid Red No. 1 aqueous solution as the etching solution, which, while having a high absorption rate for 532nm laser, overcomes the problem of toxicity in traditional wet etching solutions; 3) The device of this invention raises the liquid level at the water inlet, using the height difference to balance the pressure. The etching solution surface is kept in constant contact with the etched sample to maintain the stability of the etching process and avoid uneven etching caused by surface fluctuations or poor contact, thereby improving the etching quality and consistency; 4) This invention uses an acidic red 1 aqueous solution at a certain temperature with high absorption of 532nm laser to etch fused silica, thereby removing material from the back of the fused silica and forming a circular microstructure; Compared with other methods, this method utilizes the crystallographic wet etching characteristics of fused silica to process a circular microstructure on its back, and obtains an array of microstructures with well-defined edges and low roughness in a relatively simple way.

[0023] To more clearly illustrate the functional characteristics and structural parameters of the present invention, further explanation is provided below in conjunction with the accompanying drawings and specific embodiments. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0025] Figure 1 Optical path diagram of 532nm laser-induced wet etching on the back side;

[0026] Figure 2This is a morphological image of a single microstructure processed in Example 2;

[0027] Figure 3 The edge roughness is characterized for a single microstructure processed in Example 2;

[0028] Figure 4 A side cross-sectional view of the apparatus holding the etching solution;

[0029] Figure 5 A schematic diagram of the structure of a device for holding etching solution.

[0030] The figures are labeled as follows: 1. YAG nanosecond laser; 2. Frequency doubler; 3. Dichroic mirror; 4. Tunable continuous attenuator; 5. Total reflection mirror assembly; 501. First total reflection mirror; 502. Second total reflection mirror; 503. Third total reflection mirror; 6. Convex lens; 7. Solution container; 8. Two-dimensional moving platform; 9. Fused silica sample; 10. Etching solution; 11. Reaction tank; 12. High-level solution injection channel; 13. Screw hole; 14. Base plate; 1501. Clamping plate A; 1502. Clamping plate B; 16. Drain outlet. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] A method for wet etching of fused silica on the back side using a 300–600 nm wavelength laser, comprising:

[0033] Step 1: Fix the fused silica sample in the device containing the solution, and inject an aqueous solution of Acid Red No. 1 with a temperature of 15-30℃ and a concentration of 1.6-2.0g / L to ensure that the solution is in full contact with the back of the sample.

[0034] Step 2: A nanosecond laser with a pulse width of 6-8 ns outputs 1064 nm laser light, which is then converted to 532 nm laser light by a frequency doubler. The energy density is then adjusted to 3.569-4.497 J / cm² by a tunable continuous attenuator 4 composed of a half-wave plate and a beam splitter. 2 ;

[0035] Step 3: The laser is vertically focused onto the interface between the back of the fused silica and the solution by a total reflection mirror and a convex lens with a focal length of 100mm.

[0036] Step 4: Control the number of laser pulses to 20 per point, and move the sample at 2mm intervals using a two-dimensional moving platform to process and form a 5×5 rectangular dot matrix microstructure array;

[0037] Step 5: Clean the etched sample with ultrasonic in ethanol for 5 minutes.

[0038] Preferably, the fused silica is JGS2 fused silica, and the temperature of the Acid Red No. 1 aqueous solution is 25°C.

[0039] Preferably, in step 4, the laser energy density is achieved by adjusting the deflection angle of the half-wave plate. The microstructure is circular with a diameter of 105-216 μm, a depth of 0.84-1.08 μm, and a surface roughness of ≤12 nm rms.

[0040] Preferably, the concentration of Acid Red No. 1 solution is 1.6 g / L to 2.0 g / L.

[0041] Preferably, the number of nanosecond laser pulses is 15 to 25.

[0042] Preferably, the number of nanosecond laser pulses is 20.

[0043] Preferably, the single-pulse laser power density is 4.325 J / cm². 2 Up to 4.497 J / cm 2 between.

[0044] Preferably, the single-pulse laser power density is 4.404 J / cm². 2 .

[0045] An apparatus for wet etching of fused silica using a 300-600 nm wavelength laser on the back side includes a solution holding device 7 and a laser etching device; the solution holding device 7 is used to hold the solution and fix the fused silica sample 9, and the laser etching device is used to emit laser pulses to etch the fused silica sample 9 to form a microstructure array on the fused silica sample 9.

[0046] Specifically, in one embodiment, such as Figure 4 , Figure 5As shown, the solution holding device 7 includes a reaction tank 11 and a base plate 14. The reaction tank 11 is integrally formed from polytetrafluoroethylene (PTFE) and is used to hold the etching solution 10. The bottom of the reaction tank 11 is provided with the base plate 14, and the back of the reaction tank 11 is provided with a high-level solution injection channel 12. The inlet of the high-level solution injection channel 12 is higher than the liquid level of the reaction tank, and the liquid level is maintained by hydraulic balance. The upper end of the reaction tank 11 is provided with a double-layer adjustable clamping structure, which includes a clamping plate A1501 with a square through hole and a clamping plate B1502. Both clamping plates A1501 and B1502 are rectangular components with a square opening in the middle. They are fixed to the screw holes 13 around the reaction tank 11 by screws to expose and clamp the fused silica sample 9. The distance between clamping plates A1501 and B1502 is adjustable to accommodate samples of different thicknesses.

[0047] Specifically, in one embodiment, the laser etching apparatus includes a YAG nanosecond laser 1, a frequency doubler 2, a dichroic mirror 3, a tunable continuous attenuator 4, a total reflection mirror assembly 5, and a convex lens 6. The beam emitted by the YAG nanosecond laser 1 is doubled by the frequency doubler 2 to obtain laser light with half the wavelength, but some of the original wavelength laser light is still retained. Then, the visible light in the 300-600nm band is selected by the dichroic mirror 3. The visible light in the 300-600nm band has its laser energy adjusted by the tunable continuous attenuator 4, which is composed of a half-wave plate and a beam splitter prism. Then, it is reflected by the total reflection mirror assembly 5 and vertically focused onto the surface of the fused silica sample 9 by the convex lens 6. The focused laser pulse acts on the back of the fused silica sample 9 and the surface in contact with the solution, and finally forms a microstructure array on the fused silica sample 9.

[0048] Specifically, in one embodiment, the solution holding device 7 is disposed above the two-dimensional moving platform 8, which can move back and forth and left and right. By moving the two-dimensional moving platform 8 at intervals of 2mm, the solution holding device 7 and the fused silica sample 9 are moved, thereby forming a microstructure array on the fused silica sample 9.

[0049] Specifically, in one embodiment, the spacing between clamping plate A1501 and clamping plate B1502 is adjusted by replacing fixing screws of different lengths.

[0050] Specifically, in one embodiment, the reaction tank 11, the bottom plate 14, and the high-level solution injection channel are sealed with a corrosion-resistant adhesive.

[0051] Specifically, in one embodiment, the drain outlet 16 is located on the side of the solution holding device 7, tangent to the bottom of the solution being held, and is filled with a piston of the same material.

[0052] Specifically, in one embodiment, the reaction tank 11 is used to hold the etching solution 10, and a high-level solution injection channel 12 is provided at its rear to facilitate timely replenishment or replacement of the solution during the etching process, avoiding the impact on the continuity and stability of the etching due to sample movement. The high-level solution injection channel 12 is positioned higher than the liquid surface inside the reaction tank 11. The pressure balance generated by the height difference effectively maintains continuous contact between the etching liquid surface and the surface of the fused silica sample 9, preventing liquid surface sloshing or fluctuation and ensuring etching uniformity.

[0053] Specifically, in one embodiment, the upper end of the reaction tank 11 is provided with a clamping plate assembly, including clamping plates A1501 and B1502 set vertically. Both clamping plates are rectangular frames with a square opening in the center for exposing and fixing the fused silica sample 9. Screw holes 13 are provided at the four corners of clamping plates A1501 and B1502, which are fixed to the upper part of the reaction tank by screws to ensure the sample is clamped tightly and does not slip. Clamping plate B1502 is adjustable to accommodate samples of different thicknesses; it is connected to the reaction tank 11 by screws, facilitating quick sample replacement without disassembling the entire device.

[0054] This device preferably uses polytetrafluoroethylene (PTFE) material for all components, which has good chemical stability and corrosion resistance, making it suitable for various corrosive solutions required in the LIBWE process. The base plate 14 and the reaction tank 11 are bonded together in a single process and cannot be separated, ensuring the overall structure's sealing and stability and preventing solution leakage.

[0055] In actual operation, the etching solution 10 is injected into the reaction tank 11 through the high-level solution injection channel 12. Then, the fused silica sample 9 is placed in the clamping plate and locked to ensure that the back side of the fused silica sample 9 is stably in contact with the liquid surface. Subsequently, laser irradiation can be performed to achieve efficient and stable back-side etching.

[0056] This device simplifies the etching solution addition process by incorporating a water inlet, allowing for solution addition or replacement without removing the sample after the device is fixed on the mobile platform. By raising the liquid level at the water inlet and using the height difference to balance pressure, the device ensures that the etching solution surface remains in constant contact with the etched sample, maintaining the stability of the etching process and preventing uneven etching caused by liquid level fluctuations or poor contact. This, in turn, improves etching quality and consistency.

[0057] A method for laser back-side wet etching of fused silica using a 300nm–600nm wavelength laser, comprising the following steps:

[0058] (1) As Figure 1 As shown, construct the processing optical path, adjust the total reflection mirror, and ensure that the laser incident direction is perpendicular to the surface of the fused silica being processed.

[0059] (2) By adjusting the tunable continuous attenuator composed of a half-wave plate and a prism, the energy density of the 532nm laser pulse acting on the fused silica surface is made to be between 3.569 and 4.497 J / cm². 2 ;

[0060] (3) Adjust the movement path of the two-dimensional translation stage so that it processes a light-damaging zone every 2 mm, and control the number of pulses between 15 and 25 to process a 5×5 rectangular dot array on the fused silica surface. Furthermore, when the number of pulses is 20, the energy of the sample surface reaches the threshold and the roughness can be ensured to be within an acceptable range.

[0061] Specifically, in one embodiment, reference is made to Figure 1 To implement this invention, the optical path for LIBWE processing using a 532nm laser in an Acid Red I aqueous solution must first be constructed. A beam emitted from a YAG nanosecond laser 1 with a center wavelength of 1064nm is multiplied by a frequency doubler 2 to obtain both a 532nm and a 1064nm laser. The 532nm laser is then obtained through a dichroic mirror 3. A tunable continuous laser attenuator 4, composed of a half-wave plate and a beam splitter prism, adjusts the laser energy. The laser energy is then focused vertically onto the sample surface by a first total reflection mirror 501, a second total reflection mirror 502, and a third total reflection mirror 503, and finally by a convex lens 6. A solution holding device 7 is fixed on a two-dimensional moving platform 8. After focusing, the energy density ranges from 3.569 J / cm². 2 Up to 4.497 J / cm 2 The laser pulse is applied to the back of the fused silica sample 9 and the surface in contact with the solution. The focused laser pulse is applied to the back of the material and the surface in contact with the solution, which can remove the material from the target material and finally form a microstructure array on the fused silica sample 9.

[0062] Specifically, in one embodiment, the Acid Red 1 solution refers to an Acid Red 1 solution with a temperature of 15-30°C and a concentration of 1.6-2.0 g / L. Different concentrations and temperatures of the Acid Red 1 solution affect the etching rate of fused silica. If the solution concentration is too low, a higher energy density is required to reach the threshold, thus increasing the surface roughness of the sample; if the solution concentration is too high, the sample surface morphology becomes severely uneven. Because the etching rate of the photodestruction zone differs from that of other areas, microstructures will form centered on the photodestruction zone.

[0063] Specifically, in one embodiment, the fused silica is JGS2. Different fused silica spectra have different application ranges, which will affect its etching effect.

[0064] Example 1

[0065] In this embodiment, the laser is a nanosecond YAG laser with a center wavelength of 1064nm and a pulse width of 6–8ns. A frequency doubler 2 is used to obtain a laser with a wavelength of 532nm, and the number of laser pulses is set to 20. The laser is focused by a convex lens onto the interface between the back of a 50mm × 50mm × 1mm fused silica sample and the Acid Red No. 1 solution. The sample is then fixed to a designed solution container and placed on a two-dimensional moving platform.

[0066] During the processing, the laser was always incident perpendicularly to the fused silica surface, with the back of the sample positioned at the focal point of the convex lens. Wet etching of the fused silica was performed using an aqueous solution of Acid Red No. 1 at 25°C and a concentration of 1.6 g / L. The laser energy was adjusted using a tunable continuous attenuator composed of a half-wave plate and a beam splitter prism, achieving a single-pulse energy density of 4.497 J / cm² on the fused silica surface. 2 The two-dimensional moving platform 8 moves along a preset trajectory, creating a light-damaging zone at 2mm intervals, ultimately forming a 5×5 rectangular dot array on the fused silica surface.

[0067] After etching, the sample is ultrasonically cleaned in ethanol for 5 minutes to remove residual reaction products.

[0068] In this embodiment, the characterization was performed using scanning electron microscopy (SEM) as follows: Figure 2 As shown, the microstructure obtained after processing is circular with a diameter of 105 μm; characterization by white light interference microscopy is as follows. Figure 3 As shown, the microstructure obtained after processing has well-defined edges and low roughness, with a depth of 0.84 μm and a roughness of 10 nm rms.

[0069] Example 2

[0070] The laser source remains the same as in Example 1, a nanosecond YAG laser with a center wavelength of 1064 nm and a pulse width of 6–8 ns. The material specifications are also the same as in Example 1, consisting of 50 mm × 50 mm × 1 mm fused silica. It is fixed to the moving platform in the same manner as in Example 1. The pulse energy density used in this example is 4.497 J / cm². 2 The number of laser pulses was set to 20, and acid red No. 1 solution with a temperature of 25℃ and a concentration of 2.0 g / L was used to perform wet etching on the fused silica. The two-dimensional translation stage moved along a preset trajectory, so that a photodestruction zone was formed at intervals of 2 mm, and finally a 5×5 rectangular dot array was formed on the surface of the fused silica.

[0071] Following the exact same method as in Example 1, after etching, the sample was ultrasonically cleaned in ethanol and characterized by scanning electron microscopy (SEM). Figure 2 As shown, the microstructure obtained after processing is circular with a diameter of 216 μm; characterization by white light interference microscopy is as follows. Figure 3As shown, the microstructure obtained after processing has well-defined edges and low roughness, with a depth of 1.08 μm and a roughness of 12 nm rms.

[0072] Example 3

[0073] The laser source remains the same as in Example 1, a nanosecond YAG laser with a center wavelength of 1064 nm and a pulse width of 6–8 ns. The material specifications are also the same as in Example 1, consisting of 50 mm × 50 mm × 1 mm fused silica. It is fixed to the moving platform in the same manner as in Example 1. The pulse energy density used in this example is 4.404 J / cm². 2 The number of laser pulses was set to 20, and acid red No. 1 solution with a temperature of 25℃ and a concentration of 2.0 g / L was used to perform wet etching on the fused silica. The two-dimensional translation stage moved along a preset trajectory, so that a photodestruction zone was formed at intervals of 2 mm, and finally a 5×5 rectangular dot array was formed on the surface of the fused silica.

[0074] Following the exact same method as in Example 1, after etching, the sample was ultrasonically cleaned in ethanol and characterized by scanning electron microscopy (SEM). Figure 2 As shown, the microstructure obtained after processing is circular with a diameter of 186 μm; characterization by white light interference microscopy is as follows. Figure 3 As shown, the microstructure obtained after processing has well-defined edges and low roughness, with a depth of 0.96 μm and a roughness of 10 nm rms.

[0075] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for wet etching of fused silica on the back side using a 300-600 nm wavelength laser, characterized in that, Includes the following steps: Step 1: Fix the fused silica sample in the device containing the solution, and inject an aqueous solution of Acid Red No. 1 with a temperature of 15-30℃ and a concentration of 1.6-2.0g / L to ensure that the solution is in full contact with the back of the sample. Step 2: A nanosecond laser with a pulse width of 6-8 ns outputs 1064 nm laser light, which is then converted to 532 nm laser light by a frequency doubler. The energy density is then adjusted to 3.569-4.497 J / cm² using a tunable continuous attenuator composed of a half-wave plate and a beam splitter. 2 ; Step 3: The laser is vertically focused onto the interface between the back of the fused silica and the solution by a total reflection mirror and a convex lens with a focal length of 100mm. Step 4: Control the number of laser pulses to 20 per point, and move the sample at 2mm intervals using a two-dimensional moving platform to process and form a 5×5 rectangular dot matrix microstructure array; Step 5: Clean the etched sample with ultrasonic in ethanol for 5 minutes.

2. The method for wet etching of fused silica back surface using a 300-600nm wavelength laser according to claim 1, characterized in that, The fused silica is JGS2 fused silica, and the temperature of the Acid Red No. 1 aqueous solution is 25°C.

3. The method for wet etching of fused silica on the back side using a 300-600 nm wavelength laser according to claim 1, characterized in that, In step 4, the laser energy density is achieved by adjusting the deflection angle of the half-wave plate. The microstructure is circular with a diameter of 105-216 μm, a depth of 0.84-1.08 μm, and a surface roughness of ≤12 nm rms.

4. An apparatus for wet etching of fused silica on the back side using a laser in the 300-600 nm wavelength band, the apparatus being applicable to the method described in any one of claims 1-3, characterized in that, It includes a solution holding device (7) and a laser etching device; the solution holding device (7) is used to hold the solution and fix the fused silica sample (9), and the laser etching device is used to emit laser pulses to etch the fused silica sample (9) to form a microstructure array on the fused silica sample (9).

5. The apparatus for wet etching of fused silica back surface using a 300-600 nm wavelength laser according to claim 4, characterized in that, The solution holding device (7) includes a reaction tank (11) and a base plate (14); the reaction tank (11) is used to hold the etching solution (10); the bottom of the reaction tank (11) is provided with a base plate (14), and the back of the reaction tank (11) is provided with a high-level solution injection channel (12), the inlet of the high-level solution injection channel (12) is higher than the liquid level of the reaction tank; the upper end of the reaction tank (11) is provided with a double-layer adjustable clamping structure, the double-layer adjustable clamping structure includes a clamping plate A (1501) and a clamping plate B (1502) with a square through hole, both clamping plate A (1501) and clamping plate B (1502) are rectangular components with a square opening in the middle, and are fixed to the screw holes (13) around the reaction tank (11) by screws, for exposing and clamping the fused silica sample (9).

6. The apparatus for wet etching of fused silica back surface using a 300-600 nm wavelength laser according to claim 4, characterized in that, The laser etching device includes a YAG nanosecond laser (1), a frequency doubler (2), a dichroic mirror (3), a tunable continuous attenuator (4), a total reflection mirror assembly (5), and a convex lens (6). The beam emitted by the YAG nanosecond laser (1) is doubled by the frequency doubler (2) to obtain laser light with half the wavelength, and then selected by the dichroic mirror (3) to obtain visible light in the 300-600nm band. The visible light in the 300-600nm band is adjusted by the tunable continuous attenuator (4) composed of a half-wave plate and a beam splitter, and then reflected by the total reflection mirror assembly (5) and vertically focused onto the surface of the fused silica sample (9) by the convex lens (6). The focused laser pulse acts on the back of the fused silica sample (9) and the surface in contact with the solution, and finally forms a microstructure array on the fused silica sample (9).

7. The apparatus for wet etching of fused silica back surface using a 300-600 nm wavelength laser according to claim 4, characterized in that, The solution holding device (7) is positioned above the two-dimensional moving platform (8). The two-dimensional moving platform (8) can move forward, backward, left, and right. By moving the two-dimensional moving platform (8) at intervals of 2 mm, the solution holding device (7) and the fused silica sample (9) are moved, thereby forming a microstructure array on the fused silica sample (9).

8. The apparatus for wet etching of fused silica back surface using a 300-600 nm wavelength laser according to claim 5, characterized in that, The spacing between clamping plates A (1501) and B (1502) can be adjusted by replacing the fixing screws of different lengths.

9. The apparatus for wet etching of fused silica back surface using a 300-600 nm wavelength laser according to claim 5, characterized in that, The reaction tank (11), the bottom plate (14), and the solution injection channel (12) are sealed with a corrosion-resistant adhesive.

10. The apparatus for wet etching of fused silica back surface using a 300-600 nm wavelength laser according to claim 4, characterized in that, The drain outlet (16) is located on the side of the solution holding device (7), tangent to the bottom of the solution being held, and is filled with a piston of the same material.

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