A method for fabricating curved grating elements on fused silica substrates using wet etching

Abstract

This invention discloses a method for fabricating a curved grating element on a fused silica substrate using wet etching, comprising: cleaning the fused silica substrate; coating the surface of the cleaned fused silica substrate with a photosensitive organic material film; exposing and developing the fused silica substrate surface coated with the photosensitive organic material film to generate a grating image; performing wet etching to transfer the grating image generated by the exposure and development onto the fused silica substrate, obtaining a fused silica substrate grating; and cleaning the fused silica substrate grating to remove the photosensitive organic material film remaining on the surface of the fused silica substrate grating after wet etching, thereby obtaining a curved fused silica substrate grating element. The method of this invention can fabricate fused silica substrate grating elements without subsurface defects, thereby improving the laser damage resistance of the fused silica substrate grating elements, extending the service life of the grating elements, and reducing the cost of using fused silica substrate grating elements.

Description

Technical Field

[0001] This invention belongs to the field of optical element manufacturing technology. More specifically, this invention relates to a method for fabricating a fused silica substrate curved grating element using wet etching. Background Technology

[0002] Fused silica substrate grating elements are widely used in high-power or high-energy laser devices as powerful laser beam modulation or energy diagnostic devices. During use, these grating elements must possess both beam modulation / energy diagnostic capabilities and the ability to withstand intense laser irradiation. This presents a series of technical challenges in the design and fabrication of fused silica substrate grating elements. Driven by application requirements, dry etching techniques have been developed.

[0003] Currently, dry etching techniques are used to fabricate gratings on quartz substrates. This method involves physically bombarding the surface of the fused silica substrate with a high-speed ion beam during the grating image transfer process. The image transfer is achieved by utilizing the difference in etching rate caused by structural differences on the substrate surface after masking and exposure. Existing dry etching methods can effectively transfer grating images to the fused silica substrate surface. However, because dry etching uses high-speed ion beam bombardment, subsurface defects are also generated in the shallow surface region of the grating element during the formation of the grating image on the fused silica substrate surface. Figure 1 As shown, these subsurface defects, under high-power or high-energy laser irradiation, will strongly absorb the laser energy, resulting in surface damage to the grating element. Ultimately, this leads to the failure of the grating element's function or performance. Summary of the Invention

[0004] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0005] To achieve these and other advantages according to the present invention, a method for fabricating a fused silica substrate curved grating element using wet etching is provided, comprising the following steps:

[0006] Step 1: Clean the fused silica substrate;

[0007] Step 2: Coat the cleaned fused silica substrate surface with a photosensitive organic material film;

[0008] Step 3: Expose and develop the fused silica substrate coated with a photosensitive organic material film to produce a raster image;

[0009] Step 4: Perform wet etching to transfer the grating image generated by exposure and development onto the fused silica substrate to obtain the fused silica substrate grating;

[0010] Step 5: Clean the fused silica substrate grating to remove the photosensitive organic material film layer remaining on the surface of the fused silica substrate grating after wet etching, and obtain the fused silica substrate curved grating element.

[0011] Preferably, the specific method for cleaning the fused silica substrate in step one includes:

[0012] S11. The fused silica substrate is fully immersed in a stainless steel tank containing high-purity water with a resistivity ≥15MΩ·cm. The water temperature is 50℃. An ultrasonic plate is placed at the bottom of the tank. During the cleaning process, the frequency of the ultrasonic plate changes sequentially from 28kHz, 40kHz, 80kHz, 108kHz to 120kHz, with each frequency lasting for 3 minutes.

[0013] S12. The fused silica substrate is fully immersed in a stainless steel tank containing a 5% sodium hydroxide solution at a temperature of 35°C. An ultrasonic transducer is placed at the bottom of the tank. During the cleaning process, the frequency of the ultrasonic transducer is changed sequentially from 28kHz, 40kHz, 80kHz, 108kHz to 120kHz, with each frequency lasting for 5 minutes.

[0014] Preferably, in step two, the specific method for coating the surface of the cleaned fused silica substrate with a photosensitive organic material film includes: immersing the fused silica substrate in a polyvinyl cinnamate reagent, with the reagent temperature controlled at 23°C; and then performing a lift coating at a speed of 80 mm / min to coat both sides of the fused silica substrate with a coating thickness of 2 micrometers.

[0015] Preferably, in step three, the specific method for exposing and developing the fused silica substrate coated with a photosensitive organic material film includes: placing the fused silica substrate coated with the photosensitive organic material film on the irradiation surface of two 351nm wavelength point light sources, one with a focal length of 10 meters and the other with a focal length of 2 meters; the fused silica substrate coated with the photosensitive organic material film is simultaneously irradiated by the two light beams for 10 minutes; then immersing the fused silica substrate in a stainless steel tank containing a 2% sodium hydroxide solution, with the solution temperature controlled at 23°C, for 10 minutes.

[0016] Preferably, in step four, the specific method for wet etching includes: immersing the fused silica substrate in a 2% hydrofluoric acid solution, wherein the hydrofluoric acid solution is contained in a polytetrafluoroethylene tank, the solution temperature is controlled at 30°C, and the immersion time is 5 minutes.

[0017] Preferably, in step five, the method for cleaning the fused silica substrate grating includes:

[0018] S51. Immerse the fused silica substrate grating completely in a mixed solution of concentrated sulfuric acid and hydrogen peroxide with a mass ratio of 3:1 for 15 minutes.

[0019] S52. The fused silica substrate is fully immersed in a stainless steel tank containing high-purity water with a resistivity ≥15MΩ·cm. The water temperature is 50℃. An ultrasonic plate is placed at the bottom of the tank. During the cleaning process, the frequency of the ultrasonic plate is changed sequentially from 28kHz, 40kHz, 80kHz, 108kHz to 120kHz, with each frequency lasting for 3 minutes.

[0020] S53. The fused silica substrate is fully immersed in a stainless steel tank containing high-purity water with a resistivity ≥15MΩ·cm. The water temperature is 50℃. A mega-sonic plate is installed at the bottom of the tank. During the cleaning process, the ultrasonic plate frequency is 750kHz and the duration is 10 minutes.

[0021] The present invention has at least the following beneficial effects: by using the method of wet etching to fabricate fused silica substrate curved gratings provided by the present invention, grating elements without subsurface defects can be fabricated, thereby improving the laser damage resistance of fused silica substrate grating elements, extending the service life of grating elements, and reducing the cost of using fused silica substrate grating elements.

[0022] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of microscopic defects on the surface of a grating element.

[0024] Figure 2 This is a schematic flowchart of a method for fabricating a fused silica substrate curved grating element using wet etching, according to an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of the surface of a fused silica substrate curved grating element without subsurface defects obtained by wet etching according to an embodiment of the present invention;

[0026] Figure 4 This is a magnified schematic diagram of a portion of the surface of a curved grating element fabricated on a fused silica substrate using wet etching, according to an embodiment of the present invention. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0028] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0029] Example

[0030] like Figure 3 As shown, this embodiment provides a method for fabricating a curved grating element on a fused silica substrate using wet etching, comprising the following steps:

[0031] Step 1: Clean the fused silica substrate. Specific methods include:

[0032] S11. The fused silica substrate is fully immersed in a stainless steel tank containing high-purity water with a resistivity ≥15MΩ·cm. The water temperature is 50℃. An ultrasonic plate is placed at the bottom of the tank. During the cleaning process, the frequency of the ultrasonic plate changes sequentially from 28kHz, 40kHz, 80kHz, 108kHz to 120kHz, with each frequency lasting for 3 minutes.

[0033] S12. The fused silica substrate is fully immersed in a stainless steel tank containing a 5% sodium hydroxide solution at a temperature of 35°C. An ultrasonic transducer is placed at the bottom of the tank. During the cleaning process, the frequency of the ultrasonic transducer is changed sequentially from 28kHz, 40kHz, 80kHz, 108kHz to 120kHz, with each frequency lasting for 5 minutes.

[0034] Step 2: Coat the cleaned fused silica substrate surface with a photosensitive organic material film. The specific method includes: immersing the fused silica substrate in a polyvinyl cinnamate reagent, with the reagent temperature controlled at 23°C; then performing a lift coating at a speed of 80 mm / min to ensure that both sides of the fused silica substrate are coated with the film, with a coating thickness of 2 micrometers.

[0035] Step 3: Expose and develop the fused silica substrate coated with a photosensitive organic material film to generate a raster image. The specific method includes: placing the fused silica substrate coated with the photosensitive organic material film on the irradiation surface of two 351nm wavelength point light sources, one with a focal length of 10 meters and the other with a focal length of 2 meters; the fused silica substrate coated with the photosensitive organic material film is simultaneously irradiated by the two light beams for 10 minutes; then immersing the fused silica substrate in a stainless steel tank containing a 2% sodium hydroxide solution, with the solution temperature controlled at 23°C, for 10 minutes.

[0036] Step 4: Perform wet etching to transfer the grating image generated by exposure and development onto the fused silica substrate to obtain the fused silica substrate grating. The specific method includes: immersing the fused silica substrate in a 2% hydrofluoric acid solution. The hydrofluoric acid solution is contained in a polytetrafluoroethylene tank, the solution temperature is controlled at 30°C, and the immersion time is 5 minutes.

[0037] Step 5: Clean the fused silica substrate grating to remove the residual photosensitive organic material film on the surface of the fused silica substrate grating after wet etching, thereby obtaining a fused silica substrate curved grating element. Specific methods include:

[0038] S51. Immerse the fused silica substrate grating completely in a mixed solution of concentrated sulfuric acid and hydrogen peroxide with a mass ratio of 3:1 for 15 minutes.

[0039] S52. The fused silica substrate is fully immersed in a stainless steel tank containing high-purity water with a resistivity ≥15MΩ·cm. The water temperature is 50℃. An ultrasonic plate is placed at the bottom of the tank. During the cleaning process, the frequency of the ultrasonic plate is changed sequentially from 28kHz, 40kHz, 80kHz, 108kHz to 120kHz, with each frequency lasting for 3 minutes.

[0040] S53. The fused silica substrate is fully immersed in a stainless steel tank containing high-purity water with a resistivity ≥15MΩ·cm. The water temperature is 50℃. A mega-sonic plate is installed at the bottom of the tank. During the cleaning process, the ultrasonic plate frequency is 750kHz and the duration is 10 minutes.

[0041] A simplified schematic diagram of the surface of the fused silica substrate curved grating element prepared in this embodiment is shown below. Figure 3 As shown, the obtained fused silica substrate curved grating element has no residual subsurface defects on its surface.

[0042] Figure 4 This is a partially enlarged schematic diagram of the surface of the fused silica substrate curved grating element fabricated by wet etching in this embodiment. The grating groove depth of the fused silica substrate curved grating element prepared in this embodiment is about 10 nm, the period is about 1 μm, and the grating aspect ratio is about 0.5.

[0043] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0044] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for fabricating a curved grating element on a fused silica substrate using wet etching, characterized in that, Includes the following steps: Step 1: Clean the fused silica substrate; Step 2: Coat the cleaned fused silica substrate surface with a photosensitive organic material film. Specific methods include: The fused silica substrate was immersed in polyvinyl cinnamate reagent at a temperature of 23 °C. Then, a coating process was performed at a speed of 80 mm / min to coat both sides of the fused silica substrate with a coating thickness of 2 micrometers. Step 3: Expose and develop the fused silica substrate coated with a photosensitive organic material film to generate a raster image. Specific methods include: A fused silica substrate coated with a photosensitive organic material film was placed on the irradiation surface of two 351 nm wavelength point light sources, one with a focal length of 10 meters and the other with a focal length of 2 meters. The fused silica substrate coated with the photosensitive organic material film was simultaneously irradiated by the two light beams for 10 minutes. Then, the fused silica substrate was immersed in a stainless steel tank containing a 2% sodium hydroxide solution at a mass concentration of 23°C for 10 minutes. Step 4: Perform wet etching to transfer the grating image generated by exposure and development onto the fused silica substrate to obtain the fused silica substrate grating; Step 5: Clean the fused silica substrate grating to remove the photosensitive organic material film layer remaining on the surface of the fused silica substrate grating after wet etching, and obtain the fused silica substrate curved grating element.

2. The method for fabricating a fused silica substrate curved grating element using wet etching as described in claim 1, characterized in that, The specific method for cleaning the fused silica substrate in step one includes: S11. The fused silica substrate is fully immersed in a stainless steel tank containing high-purity water with a resistivity ≥15 MΩ·cm. The water temperature is 50 ℃. An ultrasonic transducer is placed at the bottom of the tank. During the cleaning process, the frequency of the ultrasonic transducer changes sequentially from 28 kHz, 40 kHz, 80 kHz, 108 kHz to 120 kHz, with each frequency lasting for 3 minutes. S12. The fused silica substrate is fully immersed in a stainless steel tank containing a 5% sodium hydroxide solution at a temperature of 35°C. An ultrasonic transducer is placed at the bottom of the tank. During the cleaning process, the frequency of the ultrasonic transducer is changed sequentially from 28 kHz, 40 kHz, 80 kHz, 108 kHz to 120 kHz, with each frequency lasting for 5 minutes.

3. The method for fabricating a fused silica substrate curved grating element using wet etching as described in claim 1, characterized in that, In step four, the specific method for wet etching includes: immersing the fused silica substrate in a 2% hydrofluoric acid solution, with the hydrofluoric acid solution contained in a polytetrafluoroethylene tank, the solution temperature controlled at 30 ℃, and the immersion time being 5 minutes.

4. The method for fabricating a curved grating element on a fused silica substrate using wet etching as described in claim 1, characterized in that, The method for cleaning the fused silica substrate grating in step five includes: S51. Immerse the fused silica substrate grating completely in a mixed solution of concentrated sulfuric acid and hydrogen peroxide with a mass ratio of 3:1 for 15 minutes. S52. The fused silica substrate is fully immersed in a stainless steel tank containing high-purity water with a resistivity ≥15 MΩ·cm. The water temperature is 50℃. An ultrasonic transducer is placed at the bottom of the tank. During the cleaning process, the frequency of the ultrasonic transducer changes sequentially from 28 kHz, 40 kHz, 80 kHz, 108 kHz to 120 kHz, with each frequency lasting for 3 minutes. S53. The fused silica substrate is fully immersed in a stainless steel tank containing high-purity water with a resistivity ≥15 MΩ·cm. The water temperature is 50 ℃. A megasonite plate is installed at the bottom of the tank. During the cleaning process, the ultrasonic plate frequency is 750 kHz and the duration is 10 minutes.

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