Diamond mid-infrared optical window with anti-reflection microstructure and preparation method of diamond mid-infrared optical window

Abstract

The invention provides a diamond mid-infrared optical window with an anti-reflection microstructure and a preparation method of the diamond mid-infrared optical window, belongs to the technical field of optical material preparation, and aims to solve the technical problem of low light transmittance of an infrared optical window of a diamond base material. The infrared optical window comprises a diamond substrate, wherein at least one surface of the diamond substrate is provided with an anti-reflection microstructure; the anti-reflection microstructure is a quadrangular frustum pyramid arranged in a two-dimensional matrix. The preparation method comprises the following steps: (1) carrying out horizontal grating processing on the surface of the diamond surface substrate by using femtosecond laser, and then carrying out laser cleaning; (2) performing vertical grating processing on the surface of the diamond substrate by using the femtosecond laser again; (3) the diamond substrate obtained in the step (2) is put into a mixed acid solution for wet etching, and a graphite layer on the surface of the diamond substrate is removed; and (4) annealing the diamond substrate to obtain the diamond substrate with the anti-reflection structure. The average transmittance of the diamond optical window with the anti-reflection structure at the infrared 10-12 [mu] m position reaches 93% and is improved by 23%, and the highest transmittance reaches 94.5%.

Description

Technical Field

[0001] The invention belongs to the technical field of optical material preparation, and in particular relates to a diamond mid-infrared optical window with an anti-reflection microstructure and a preparation method thereof. Background Art

[0002] The transmittance of diamond body material in the infrared band is 60%-65%, which cannot meet the requirements of high-precision optical windows. At present, coating the surface of diamond with an optical anti-reflection film is the most mainstream way to improve the transmittance. For example, patent publication number CN116752110A discloses a method for preparing diamond material for optical windows; the steps are: S1, preparing an optical grade polycrystalline diamond film, followed by cutting, grinding, polishing and cleaning it; S2, ICP etching the optical anti-reflection microstructure layer on the surface of the diamond film prepared in step S1, cleaning and drying after etching, and placing it in a vacuum dish for standby; S3, using magnetron sputtering technology, coating the surface of the optical anti-reflection microstructure layer of the diamond film prepared in step S2 with a rare earth oxide anti-reflection film, and setting the thickness of the coated rare earth oxide anti-reflection film according to the refractive index of the diamond film with an optical anti-reflection microstructure layer prepared in step S2 and the optical anti-reflection film theory; the magnetron sputtering technology is a combination of pre-plating and variable speed plating.

[0003] However, the application of optical anti-reflection films in infrared optical windows will face many problems, such as film shedding due to sand and gravel impact, stress mismatch between films caused by heat energy generated by high-speed operation, film damage caused by corrosion from rain, fog and seawater, etc., which ultimately lead to a serious decrease in the optical transmittance of diamond and affect the performance of optoelectronic devices.

[0004] Patent Publication No. CN114488362A discloses a sapphire window with a double-sided anti-reflection microstructure and a preparation method thereof, comprising a sapphire substrate layer, characterized in that a first microstructure array is prepared on the upper surface of the sapphire substrate layer, and a second microstructure array or a first optical film is prepared on the lower surface of the sapphire substrate layer, wherein the first microstructure array and the second microstructure array are one-dimensional grating structures, the groove depth is 140nm-220nm, and the transmittance in the wavelength range of 715nm-920nm is above 98%. Patent Publication No. CN 113740940A discloses a wide-bandwidth angle anti-reflection composite micro-nanostructure surface and a preparation method thereof, wherein a single-layer film is formed on the surface of an optical material substrate, a moth-eye micro-nanostructure of a certain depth is formed on the film layer, and a residual film layer is left, which is composed of three basic structures, including: a micro-nanostructure layer, an intermediate residual layer, and a substrate layer in sequence. Both of the above patents improve the transmittance of different bands by preparing a microstructure array on the substrate surface. However, since different combinations of substrates and structural arrays have different selectivities for wavelengths, the prior art does not disclose a micro-nano structure for improving the transmittance of diamond substrates in the mid-infrared band. Summary of the invention

[0005] In order to solve the technical problem of low light transmittance of infrared optical windows of diamond substrates, the present invention proposes a diamond mid-infrared optical window with an anti-reflection microstructure and a preparation method thereof. The prepared anti-reflection structure can significantly increase the optical transmittance of diamond in the mid-infrared band.

[0006] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A diamond mid-infrared optical window with an anti-reflection microstructure comprises a diamond substrate, at least one side of which is provided with an anti-reflection microstructure; the anti-reflection microstructure is a quadrangular pyramid arranged in a two-dimensional matrix.

[0008] The arrangement period of the tetrahedron is 3-4 μm, the height is 1.5-2 μm, and the top side length is 2-3 μm.

[0009] A method for preparing a diamond mid-infrared optical window with an anti-reflection microstructure comprises the following steps:

[0010] (1) Horizontal grating processing on the surface of diamond surface substrate using femtosecond laser, followed by laser cleaning;

[0011] (2) Using femtosecond laser again to perform vertical grating processing on the surface of the diamond substrate;

[0012] (3) placing the diamond substrate obtained in step (2) into a mixed acid solution for wet etching to remove the graphite layer on the surface of the diamond substrate;

[0013] (4) Annealing the diamond substrate to obtain a diamond substrate with an anti-reflection structure.

[0014] The processing parameters of the horizontal grating in step (1) are: laser power of 2.5-3.5 mW, exposure time of 1000-2000 μs, and laser focus located 0.5-1 μm below the diamond surface.

[0015] The laser cleaning is to shape the femtosecond laser beam into an elliptical spot, and focus the elliptical spot on the surface of the microstructure for laser cleaning.

[0016] The elliptical light spot has a major axis of 15-25 μm and a minor axis of 3-5 μm.

[0017] The processing parameters of the vertical grating laser in step (2) are: light power of 2.5-3.5 mW, exposure time of 1000-2000 μs, and laser focus located 0.5-1 μm below the diamond surface.

[0018] The mixed acid solution comprises concentrated sulfuric acid and concentrated nitric acid, and the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 8:1-10:1.

[0019] The temperature of the wet etching is 80-100° C. and the time is 5-10 hours.

[0020] The annealing treatment is performed at a temperature of 400-600° C. and for a time of 1-3 hours.

[0021] Beneficial effects of the present invention: The anti-reflection structure prepared by the method of the present invention can significantly increase the optical transmittance of diamond in the mid-infrared band. The quadrangular pyramid-shaped anti-reflection microstructure prepared on the surface of diamond can provide a gradual refractive index distribution for the incident light on both sides of the incident interface, that is, introduce a refractive index gradient, which can reduce the reflection of light and increase the transmittance of diamond. The intrinsic transmittance of diamond is about 70%, while the average transmittance of the diamond optical window with an anti-reflection structure of the present invention reaches 93% at the infrared 10-12μm, an increase of up to 23%, and the highest transmittance reaches 94.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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 these drawings without paying creative work.

[0023] Figure 1 Schematic diagram of the structure of a diamond infrared window with a double-sided anti-reflection microstructure.

[0024] Figure 2 Schematic diagram of the anti-reflection microstructure corresponding to any one of the two sides.

[0025] Figure 3 The transmittance curve of the double-sided anti-reflective diamond infrared optical window in Example 1 measured by Fourier transform infrared spectrometer.

[0026] Figure 4 The transmittance curve of the anti-reflective diamond infrared optical window in Example 2 measured by Fourier transform infrared spectrometer.

[0027] Figure 5 The transmittance curve of the anti-reflective diamond infrared optical window in Example 5 measured by Fourier transform infrared spectrometer. DETAILED DESCRIPTION

[0028] 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.

[0029] Example 1

[0030] A diamond mid-infrared optical window with an anti-reflective microstructure, such as Figure 1 As shown, it includes a diamond substrate, and both sides of the diamond substrate are provided with anti-reflection microstructures; the anti-reflection microstructures are four-sided pyramids arranged in a two-dimensional matrix. Figure 2 As shown, the arrangement period of the four-sided pyramid is 3.5 μm, the height is 1.6 μm, and the top side length is 2.5 μm; the transmittance curve of the anti-reflective diamond infrared optical window is as shown Figure 3 As shown in the figure, the curve below is the transmittance of a flat diamond that is double-sided polished and without any modification. Figure 3 It can be seen that the transmittance of the diamond infrared optical window with a double-sided anti-reflection structure of this embodiment is significantly higher than that of a flat diamond: in the 10-12 μm band, the average transmittance of the double-sided polished flat diamond is about 70%, while the average transmittance of the anti-reflection infrared optical window of this embodiment measured within this band reaches 93%, an increase of up to 23%, with the highest transmittance reaching 94.5%.

[0031] The method for preparing the diamond mid-infrared optical window with an anti-reflective microstructure comprises the following steps:

[0032] (1) Diamond surface treatment: The double-sided polished diamond substrate was ultrasonically cleaned for 15 minutes using alcohol and deionized water respectively, and then dried in an oven and cooled to 25°C.

[0033] (2) Preliminary processing of anti-reflection microstructure: A femtosecond laser with a wavelength of 515 nm was focused on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7 for horizontal grating processing. The wavelength of the femtosecond laser was 515 nm, the repetition rate was 25 kHz, the pulse width was 390 fs, the laser power was 2.8 mW, the exposure time was 1000 μs, and the laser focus was located 0.5 μm below the diamond surface.

[0034] (3) Laser cleaning of microstructures: The femtosecond laser is beam-shaped through a combined focusing system of a cylindrical lens and an objective lens to produce an elliptical spot with a major axis of 20 μm and a minor axis of 5 μm. The elliptical spot is focused on the surface of the microstructure for laser cleaning to remove debris generated during the initial laser processing.

[0035] (4) Secondary processing of anti-reflective microstructure: A femtosecond laser with a wavelength of 515 nm was focused on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7 for vertical grating processing. The repetition rate was 25 kHz, the pulse width was 390 fs, the laser power was 2.8 mW, the exposure time was 1000 μs, and the laser focus was located 0.5 μm below the diamond surface.

[0036] (5) Flip to the other side of the diamond and repeat steps (2-4) to prepare the same anti-reflection structure on the other side as on the first side, and the anti-reflection structures on the two sides are not required to be strictly aligned.

[0037] (6) Wet etching: After laser processing, the sample was placed in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 8:1 and heated to 80°C. Wet etching was performed for 5 hours to remove the graphite layer on the diamond surface.

[0038] (7) Diamond surface reprocessing: After etching, the diamond surface was ultrasonically cleaned with acetone, alcohol and deionized water for 15 minutes respectively, dried in an oven, and cooled to 25°C.

[0039] (8) The diamond with the anti-reflection structure is subjected to high temperature annealing at 500° C. for 2 hours.

[0040] Example 2

[0041] A diamond mid-infrared optical window with an anti-reflection microstructure comprises a diamond substrate, wherein a single surface of the diamond substrate is provided with an anti-reflection microstructure; the anti-reflection microstructure is a quadrangular pyramid arranged in a two-dimensional matrix. The arrangement period of the quadrangular pyramid is 3.5 μm, the height is 1.6 μm, and the top side length is 2.5 μm. The transmittance curve of the anti-reflection diamond infrared optical window is as follows: Figure 4 As shown, the upper curve is the transmittance of the single-sided anti-reflection diamond infrared optical window corresponding to this embodiment, and the lower curve is the transmittance of the double-sided polished and unmodified flat diamond. Figure 4 It can be seen that the transmittance of the diamond infrared optical window with a single-sided anti-reflection structure of this embodiment is significantly higher than that of a flat diamond: in the 10-12 μm band, the average transmittance of the flat diamond is about 70%, while the average transmittance of the single-sided anti-reflection infrared optical window of the present invention measured within this band reaches 82%, with the highest transmittance reaching 83%.

[0042] The method for preparing the diamond mid-infrared optical window with anti-reflection microstructure comprises the following steps:

[0043] (1) Diamond surface treatment: The double-sided polished diamond substrate was ultrasonically cleaned for 15 minutes using alcohol and deionized water respectively, and then dried in an oven and cooled to 25°C.

[0044] (2) Preliminary processing of anti-reflection microstructure: A femtosecond laser with a wavelength of 515 nm was focused on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7 for horizontal grating processing. The laser power was 3 mW, the exposure time was 1000 μs, and the laser focus was located 0.7 μm below the diamond surface.

[0045] (3) Laser cleaning of microstructures: The femtosecond laser is beam-shaped through a combined focusing system of a cylindrical lens and an objective lens to produce an elliptical spot with a major axis of 22 μm and a minor axis of 4 μm. The elliptical spot is focused on the surface of the microstructure for laser cleaning to remove debris generated during the initial laser processing.

[0046] (4) Secondary processing of anti-reflective microstructure: vertical grating processing is performed by focusing a femtosecond laser with a wavelength of 515 nm on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7. The laser power is 3 mW, the exposure time is 1000 μs, and the laser focus is located 0.7 μm below the diamond surface.

[0047] (5) Wet etching: After laser processing, the sample was placed in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 8:1 and heated to 80°C. Wet etching was performed for 5 hours to remove the graphite layer on the diamond surface.

[0048] (6) Diamond surface reprocessing: After etching, the diamond surface was ultrasonically cleaned with acetone, alcohol and deionized water for 15 minutes respectively, dried in an oven, and cooled to 25°C.

[0049] (7) The diamond with the anti-reflection structure is subjected to high temperature annealing at 500° C. for 2 hours.

[0050] Example 3

[0051] A diamond mid-infrared optical window with an anti-reflection microstructure comprises a diamond substrate, and both sides of the diamond substrate are provided with anti-reflection microstructures; the anti-reflection microstructures are four-sided pyramids arranged in a two-dimensional matrix. Figure 2 As shown, the arrangement period of the tetrahedron is 3 μm, the height is 1.5 μm, and the top side length is 2 μm; the transmittance curve of the anti-reflective diamond infrared optical window has an average transmittance of 91% in the 9-12 μm band, of which the highest transmittance reaches 93%, and the corresponding wavelength is 9.5 μm.

[0052] The method for preparing the diamond mid-infrared optical window with an anti-reflective microstructure comprises the following steps:

[0053] (1) Diamond surface treatment: The double-sided polished diamond substrate was ultrasonically cleaned for 15 minutes using alcohol and deionized water respectively, and then dried in an oven and cooled to 25°C.

[0054] (2) Preliminary processing of anti-reflection microstructure: A femtosecond laser with a wavelength of 515 nm was focused on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7 to perform horizontal grating processing. The laser power was 2.8 mW, the exposure time was 1000 μs, and the laser focus was located 0.5 μm below the diamond surface.

[0055] (3) Laser cleaning of microstructures: The femtosecond laser is beam-shaped through a combined focusing system of a cylindrical lens and an objective lens to produce an elliptical spot with a major axis of 20 μm and a minor axis of 5 μm. The elliptical spot is focused on the surface of the microstructure for laser cleaning to remove debris generated during the initial laser processing.

[0056] (4) Secondary processing of anti-reflective microstructure: vertical grating processing is performed by focusing a femtosecond laser with a wavelength of 515 nm on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7. The laser power is 2.8 mW, the exposure time is 1000 μs, and the laser focus is located 0.5 μm below the diamond surface.

[0057] (5) Flip to the other side of the diamond and repeat steps (2-4) to prepare the same anti-reflection structure on the other side as on the first side, and the anti-reflection structures on the two sides are not required to be strictly aligned.

[0058] (6) Wet etching: After laser processing, the sample was placed in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 8:1 and heated to 80°C. Wet etching was performed for 5 hours to remove the graphite layer on the diamond surface.

[0059] (7) Diamond surface reprocessing: After etching, the diamond surface was ultrasonically cleaned with acetone, alcohol and deionized water for 15 minutes respectively, dried in an oven, and cooled to 25°C.

[0060] (8) The diamond with the anti-reflection structure is subjected to high temperature annealing at 500° C. for 2 hours.

[0061] Example 4

[0062] A diamond mid-infrared optical window with an anti-reflection microstructure comprises a diamond substrate, and both sides of the diamond substrate are provided with anti-reflection microstructures; the anti-reflection microstructures are four-sided pyramids arranged in a two-dimensional matrix. Figure 2As shown, the arrangement period of the tetrahedron is 4μm, the height is 2μm, and the top side length is 3μm; the transmittance curve of the anti-reflective diamond infrared optical window has an average transmittance of 91% in the 11-13μm band, of which the highest transmittance reaches 92%, and the corresponding wavelength is 11μm.

[0063] The method for preparing the diamond mid-infrared optical window with an anti-reflective microstructure comprises the following steps:

[0064] (1) Diamond surface treatment: The double-sided polished diamond substrate was ultrasonically cleaned for 15 minutes using alcohol and deionized water respectively, and then dried in an oven and cooled to 25°C.

[0065] (2) Preliminary processing of anti-reflection microstructure: A femtosecond laser with a wavelength of 515 nm was focused on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7 to perform horizontal grating processing. The laser power was 2.8 mW, the exposure time was 1000 μs, and the laser focus was located 0.5 μm below the diamond surface.

[0066] (3) Laser cleaning of microstructures: The femtosecond laser is beam-shaped through a combined focusing system of a cylindrical lens and an objective lens to produce an elliptical spot with a major axis of 20 μm and a minor axis of 5 μm. The elliptical spot is focused on the surface of the microstructure for laser cleaning to remove debris generated during the initial laser processing.

[0067] (4) Secondary processing of anti-reflective microstructure: vertical grating processing is performed by focusing a femtosecond laser with a wavelength of 515 nm on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7. The laser power is 2.8 mW, the exposure time is 1000 μs, and the laser focus is located 0.5 μm below the diamond surface.

[0068] (5) Flip to the other side of the diamond and repeat steps (2-4) to prepare the same anti-reflection structure on the other side as on the first side, and the anti-reflection structures on the two sides are not required to be strictly aligned.

[0069] (6) Wet etching: After laser processing, the sample was placed in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 8:1 and heated to 80°C. Wet etching was performed for 5 hours to remove the graphite layer on the diamond surface.

[0070] (7) Diamond surface reprocessing: After etching, the diamond surface was ultrasonically cleaned with acetone, alcohol and deionized water for 15 minutes respectively, dried in an oven, and cooled to 25°C.

[0071] (8) The diamond with the anti-reflection structure is subjected to high temperature annealing at 500° C. for 2 hours.

[0072] Example 5

[0073] A diamond mid-infrared optical window with an anti-reflection microstructure comprises a diamond substrate, and both sides of the diamond substrate are provided with anti-reflection microstructures; the anti-reflection microstructures are four-sided pyramids arranged in a two-dimensional matrix. Figure 2 As shown, the arrangement period of the four-sided pyramid is 3.5 μm, the height is 1.6 μm, and the top side length is 2.5 μm; the transmittance curve of the anti-reflective diamond infrared optical window is as shown Figure 5 As shown in the figure, the curve below is the transmittance of a flat diamond with double-sided polishing and no modification. It can be seen from the figure that the transmittance of the diamond infrared optical window with double-sided anti-reflection structure in this embodiment is significantly higher than that of a flat diamond: the average transmittance in the 10-12μm band reaches 91%, of which the highest transmittance reaches 93.4%, and the corresponding wavelength is 10.5μm.

[0074] The method for preparing the diamond mid-infrared optical window with an anti-reflective microstructure comprises the following steps:

[0075] (1) Diamond surface treatment: The double-sided polished diamond substrate was ultrasonically cleaned for 15 minutes using alcohol and deionized water respectively, and then dried in an oven and cooled to 25°C.

[0076] (2) Preliminary processing of anti-reflection microstructure: A femtosecond laser with a wavelength of 515 nm was focused on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7 to perform horizontal grating processing. The laser power was 2.8 mW, the exposure time was 1000 μs, and the laser focus was located 0.5 μm below the diamond surface.

[0077] (3) Laser cleaning of microstructures: The femtosecond laser is beam-shaped through a combined focusing system of a cylindrical lens and an objective lens to produce an elliptical spot with a major axis of 20 μm and a minor axis of 5 μm. The elliptical spot is focused on the surface of the microstructure for laser cleaning to remove debris generated during the initial laser processing.

[0078] (4) Secondary processing of anti-reflective microstructure: vertical grating processing is performed by focusing a femtosecond laser with a wavelength of 515 nm on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7. The laser power is 2.8 mW, the exposure time is 1000 μs, and the laser focus is located 0.5 μm below the diamond surface.

[0079] (5) Flip to the other side of the diamond and repeat steps (2-4) to prepare the same anti-reflection structure on the other side as on the first side, and the anti-reflection structures on the two sides are not required to be strictly aligned.

[0080] (6) Wet etching: After laser processing, the sample was placed in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 8:1 and heated to 80°C. Wet etching was performed for 5 hours to remove the graphite layer on the diamond surface.

[0081] (7) Diamond surface reprocessing: After etching, the diamond surface was ultrasonically cleaned with acetone, alcohol and deionized water for 15 minutes respectively, dried in an oven, and cooled to 25°C.

[0082] Example 6

[0083] A diamond mid-infrared optical window with an anti-reflection microstructure comprises a diamond substrate, and both sides of the diamond substrate are provided with anti-reflection microstructures; the anti-reflection microstructures are four-sided pyramids arranged in a two-dimensional matrix. Figure 2 As shown, the arrangement period of the tetrahedron is 3.5 μm, the height is 1.6 μm, and the top side length is 2.5 μm.

[0084] The method for preparing the diamond mid-infrared optical window with an anti-reflective microstructure comprises the following steps:

[0085] (1) Diamond surface treatment: The double-sided polished diamond substrate was ultrasonically cleaned for 15 minutes using alcohol and deionized water respectively, and then dried in an oven and cooled to 25°C.

[0086] (2) Preliminary processing of anti-reflection microstructure: A femtosecond laser with a wavelength of 515 nm was focused on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7 for horizontal grating processing. The repetition rate was 25 kHz, the pulse width was 390 fs, the laser power was 2.5 mW, the exposure time was 1000 μs, and the laser focus was located 1 μm below the diamond surface.

[0087] (3) Laser cleaning of microstructures: The femtosecond laser is beam-shaped through a combined focusing system of a cylindrical lens and an objective lens to produce an elliptical spot with a major axis of 20 μm and a minor axis of 5 μm. The elliptical spot is focused on the surface of the microstructure for laser cleaning to remove debris generated during the initial laser processing.

[0088] (4) Secondary processing of anti-reflective microstructure: vertical grating processing is performed by focusing a 515 nm femtosecond laser on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7. The wavelength of the femtosecond laser is 515 nm, the repetition rate is 25 kHz, the pulse width is 390 fs, the laser power is 2.8 mW, the exposure time is 1000 μs, and the laser focus is located 0.5 μm below the diamond surface.

[0089] (5) Flip to the other side of the diamond and repeat steps (2-4) to prepare the same anti-reflection structure on the other side as on the first side, and the anti-reflection structures on the two sides are not required to be strictly aligned.

[0090] (6) Wet etching: After laser processing, the sample was placed in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 10:1 and heated to 100°C. Wet etching was performed for 10 hours to remove the graphite layer on the diamond surface.

[0091] (7) Diamond surface reprocessing: After etching, the diamond surface was ultrasonically cleaned with acetone, alcohol and deionized water for 15 minutes respectively, dried in an oven, and cooled to 25°C.

[0092] (8) The diamond with the anti-reflection structure is subjected to high temperature annealing at 400°C for 3 hours.

[0093] Example 7

[0094] A diamond mid-infrared optical window with an anti-reflection microstructure comprises a diamond substrate, and both sides of the diamond substrate are provided with anti-reflection microstructures; the anti-reflection microstructures are four-sided pyramids arranged in a two-dimensional matrix. Figure 2 As shown, the arrangement period of the tetrahedron is 3.5 μm, the height is 1.6 μm, and the top side length is 2.5 μm.

[0095] The method for preparing the diamond mid-infrared optical window with an anti-reflective microstructure comprises the following steps:

[0096] (1) Diamond surface treatment: The double-sided polished diamond substrate was ultrasonically cleaned for 15 minutes using alcohol and deionized water respectively, and then dried in an oven and cooled to 25°C.

[0097] (2) Preliminary processing of anti-reflection microstructure: A femtosecond laser with a wavelength of 515 nm was focused on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7 for horizontal grating processing. The repetition rate was 25 kHz, the pulse width was 390 fs, the laser power was 2.5 mW, the exposure time was 1000 μs, and the laser focus was located 1 μm below the diamond surface.

[0098] (3) Laser cleaning of microstructures: The femtosecond laser is beam-shaped through a combined focusing system of a cylindrical lens and an objective lens to produce an elliptical spot with a major axis of 20 μm and a minor axis of 5 μm. The elliptical spot is focused on the surface of the microstructure for laser cleaning to remove debris generated during the initial laser processing.

[0099] (4) Secondary processing of anti-reflective microstructure: vertical grating processing is performed by focusing a 515 nm femtosecond laser on the diamond surface through an objective lens (60×) with a numerical aperture of 0.7. The wavelength of the femtosecond laser is 515 nm, the repetition rate is 25 kHz, the pulse width is 390 fs, the laser power is 2.8 mW, the exposure time is 1000 μs, and the laser focus is located 0.5 μm below the diamond surface.

[0100] (5) Flip to the other side of the diamond and repeat steps (2-4) to prepare the same anti-reflection structure on the other side as on the first side, and the anti-reflection structures on the two sides are not required to be strictly aligned.

[0101] (6) Wet etching: After laser processing, the sample was placed in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 9:1 and heated to 90°C. Wet etching was performed for 8 hours to remove the graphite layer on the diamond surface.

[0102] (7) Diamond surface reprocessing: After etching, the diamond surface was ultrasonically cleaned with acetone, alcohol and deionized water for 15 minutes respectively, dried in an oven, and cooled to 25°C.

[0103] (8) The diamond with the anti-reflection structure is subjected to high temperature annealing at 600° C. for 1 hour.

[0104] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A diamond mid-infrared optical window with an anti-reflective microstructure, characterized in that: The invention comprises a diamond substrate, at least one side of which is provided with an anti-reflection microstructure; the anti-reflection microstructure is a quadrangular pyramid arranged in a two-dimensional matrix.

2. The diamond mid-infrared optical window with anti-reflection microstructure according to claim 1, characterized in that: The arrangement period of the tetrahedron is 3-4 μm, the height is 1.5-2 μm, and the top side length is 2-3 μm.

3. The method for preparing a diamond mid-infrared optical window with an anti-reflection microstructure according to claim 1 or 2, characterized in that: The following steps are involved: (1) Horizontal grating processing on the surface of diamond surface substrate using femtosecond laser, followed by laser cleaning; (2) Using femtosecond laser again to perform vertical grating processing on the surface of the diamond substrate; (3) placing the diamond substrate obtained in step (2) into a mixed acid solution for wet etching to remove the graphite layer on the surface of the diamond substrate; (4) Annealing the diamond substrate to obtain a diamond substrate with an anti-reflection structure.

4. The method for preparing a diamond mid-infrared optical window with an anti-reflection microstructure according to claim 3, characterized in that: The processing parameters of the horizontal grating in step (1) are: laser power of 2.5-3.5 mW, exposure time of 1000-2000 μs, and laser focus located 0.5-1 μm below the diamond surface.

5. The method for preparing a diamond mid-infrared optical window with an anti-reflection microstructure according to claim 4, characterized in that: The laser cleaning is to shape the femtosecond laser beam into an elliptical spot, and focus the elliptical spot on the surface of the microstructure for laser cleaning.

6. The method for preparing a diamond mid-infrared optical window with an anti-reflection microstructure according to claim 5, characterized in that: The elliptical light spot has a major axis of 15-25 μm and a minor axis of 3-5 μm.

7. The method for preparing a diamond mid-infrared optical window with an anti-reflection microstructure according to claim 3, characterized in that: The processing parameters of the vertical grating laser in step (2) are: light power of 2.5-3.5 mW, exposure time of 1000-2000 μs, and laser focus located 0.5-1 μm below the diamond surface.

8. The method for preparing a diamond mid-infrared optical window with an anti-reflection microstructure according to claim 3, characterized in that: The mixed acid solution comprises concentrated sulfuric acid and concentrated nitric acid, and the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 8:1-10:

1.

9. The method for preparing a diamond mid-infrared optical window with an anti-reflection microstructure according to claim 8, characterized in that: The temperature of the wet etching is 80-100° C. and the time is 5-10 hours.

10. The method for preparing a diamond mid-infrared optical window with an anti-reflection microstructure according to claim 3, characterized in that: The annealing treatment is performed at a temperature of 400-600° C. and for a time of 1-3 hours.

Images