Sum-frequency crystal for ultraviolet laser

Abstract

The present application relates to the technical field of sum frequency crystal of laser ultraviolet laser, and specifically relates to a sum frequency crystal of ultraviolet laser, a protective film is coated on the light transmission surface of the light emitting side of the sum frequency crystal, the protective film comprises at least one high dielectric constant metal oxide film layer and at least one photocatalytically active metal oxide film layer, and the high dielectric constant metal oxide film layer and the photocatalytically active metal oxide film layer are alternately stacked. By coating the high dielectric constant metal oxide film layer and the photocatalytically active metal oxide film layer as the protective film on the light transmission surface of the light emitting side of the sum frequency crystal of the ultraviolet laser, the photocatalytically active particles can completely decompose the organic matter on the surface into CO2 and H2O under ultraviolet photon irradiation, and the incomplete reaction of the organic matter under pure ultraviolet light irradiation to form solid compounds adsorbed on the light transmission surface is slowed down, and the high dielectric constant metal oxide can ensure that the decomposed water molecules do not pollute the crystal end face and affect the output characteristics.

Description

Technical Field

[0001] This invention relates to the field of sum-frequency crystal technology for ultraviolet lasers, and specifically to a sum-frequency crystal for ultraviolet lasers. Background Technology

[0002] Fundamental frequency lasers are converted into lasers of different frequencies through frequency doubling and sum-frequency conversion techniques, expanding the application fields of lasers. However, lasers that have undergone frequency doubling and sum-frequency conversion have higher photon energies. During prolonged operation, the light-transmitting surface of the sum-frequency crystal in frequency-doubled and ultraviolet lasers can suffer damage and contamination, affecting the stable output performance of the laser. Particularly in industrial applications, under 24 / 7 operation conditions, without protective films, the lifespan of the sum-frequency crystal in ultraviolet lasers is often only 2000 hours. Frequent replacement of the sum-frequency crystal causes excessively long production line downtime. Summary of the Invention

[0003] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a sum-frequency crystal for ultraviolet lasers, which can effectively solve the problems of easy damage to the light transmission surface of the sum-frequency crystal of existing ultraviolet lasers and the need for frequent replacement of the sum-frequency crystal.

[0004] To achieve the above objectives, the technical solution of the present invention is a sum-frequency crystal for an ultraviolet laser. The sum-frequency crystal for the ultraviolet laser has an incident light-transmitting surface and an output light-transmitting surface. A protective film is deposited on the output light-transmitting surface. The protective film includes at least one high-dielectric-constant metal oxide film layer and at least one photocatalytically active metal oxide film layer, and the high-dielectric-constant metal oxide film layer and the photocatalytically active metal oxide film layer are alternately stacked.

[0005] As one embodiment, the high dielectric constant metal oxide film is any one of HfO2 film, ZrO2 film, and Ta2O5 film, and the photocatalytically active metal oxide film is any one of TiO2 film and Fe3O4 film.

[0006] As one embodiment, the high dielectric constant metal oxide film is an HfO2 film, and the photocatalytically active metal oxide film is a TiO2 film.

[0007] As one embodiment, the protective film at the end near the light-emitting side of the light-transmitting surface is a high dielectric constant metal oxide film layer, and the protective film at the end away from the light-emitting side of the light-transmitting surface is a photocatalytically active metal oxide film layer.

[0008] As one embodiment, the thickness of the protective film is less than 20 nm, the thickness of the single-layer high dielectric constant metal oxide film is less than 5 nm, and the thickness of the single-layer photocatalytically active metal oxide film is less than 5 nm.

[0009] As one embodiment, the protective film at the end near the light-emitting side of the light-transmitting surface is a photocatalytically active metal oxide film layer, and the protective film at the end away from the light-emitting side of the light-transmitting surface is a photocatalytically active metal oxide film layer.

[0010] As one embodiment, the thickness of the protective film is no greater than 1.5 times the wavelength, the thickness of a single layer of the high dielectric constant metal oxide film is 1 / 4 of the wavelength, the thickness of a single layer of the photocatalytically active metal oxide film is 1 / 4 of the wavelength, and the thickness of the photocatalytically active metal oxide film at the end away from the light-emitting side is less than 5 nm.

[0011] As one embodiment, the high dielectric constant metal oxide film and the photocatalytically active metal oxide film are prepared by chemical vapor deposition or physical vapor deposition.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] (1) In this invention, a protective film composed of a high dielectric constant metal oxide film and a photocatalytically active metal oxide film is deposited on the light-transmitting surface of the sum-frequency crystal of an ultraviolet laser. The high dielectric constant metal oxide film has a high dielectric constant, which can effectively isolate the external gas from contacting the light-transmitting surface of the crystal, avoid damage to the light-transmitting surface, and effectively improve the service life of the sum-frequency crystal. The photocatalytically active metal oxide film has photocatalytic activity. When external organic volatiles are adsorbed onto the photocatalytically active metal oxide film, the photocatalytically active metal oxide has a highly efficient catalytic decomposition ability under the assistance of high-energy photons, which can completely decompose organic matter into CO2 and H2O molecules, reducing carbon accumulation and causing film damage.

[0014] (2) The protective film of the present invention has a thin overall thickness, has little impact on the light spot pattern, and the protective film is simple to manufacture;

[0015] (3) The present invention is simple in design and has strong versatility for various types and shapes of sum-frequency crystals. Only the fixture used for coating needs to be changed. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1This is a schematic diagram of the protective film on the light-transmitting surface of the sum-frequency crystal provided in Embodiment 1 of the present invention;

[0018] Figure 2 This is a schematic diagram of the protective film on the light-transmitting surface of the sum-frequency crystal provided in Embodiment 2 of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0020] This embodiment provides a sum-frequency crystal for an ultraviolet laser. The sum-frequency crystal for the ultraviolet laser has an incident light-transmitting surface and an output light-transmitting surface. A protective film is deposited on the output light-transmitting surface. The protective film includes at least one high-dielectric-constant metal oxide film layer and at least one photocatalytically active metal oxide film layer, and the high-dielectric-constant metal oxide film layer and the photocatalytically active metal oxide film layer are alternately stacked.

[0021] This embodiment uses a protective film, composed of a high dielectric constant metal oxide film and a photocatalytically active metal oxide film, deposited on the light-emitting side of the sum-frequency crystal of an ultraviolet laser. This film blocks the contact between the crystal surface and external organic volatiles. When organic matter is adsorbed onto the surface of the photocatalytically active metal oxide film, the nano-photocatalytically active metal oxide exhibits high catalytic activity under ultraviolet photon irradiation, which can completely decompose the organic matter into CO2 and H2O. This mitigates the formation of solid compounds due to incomplete reaction of organic matter under pure ultraviolet light irradiation, which are then adsorbed onto the light-emitting surface of the crystal. At the same time, the high dielectric constant metal oxide film ensures that the decomposed water molecules will not contaminate the crystal end face and affect the output characteristics. It also effectively isolates external gases from contacting the light-emitting surface of the crystal, avoiding damage to the light-emitting surface and effectively improving the service life of the sum-frequency crystal.

[0022] Furthermore, the high dielectric constant metal oxide film is any one of HfO2 film, ZrO2 film, and Ta2O5 film, and the photocatalytically active metal oxide film is any one of TiO2 film and Fe3O4 film.

[0023] Ideally, the high dielectric constant metal oxide film is an HfO2 film, and the photocatalytically active metal oxide film is a TiO2 film.

[0024] The protective film fabrication method in this embodiment is simple. Both the high dielectric constant metal oxide film and the photocatalytically active metal oxide film are prepared using chemical vapor deposition (CVD) or physical vapor deposition (PEVD). Optimally, both the high dielectric constant metal oxide film and the photocatalytically active metal oxide film are prepared using CVD, resulting in better uniformity. Specific CVD methods include CVD, PECVD, MOCVD, ALD, and PEALD, and the use of these techniques to prepare the aforementioned high dielectric constant metal oxide film and photocatalytically active metal oxide film are existing technologies in this field. Taking the preparation of HfO2 and TiO2 films using ALD as an example, when preparing HfO2 films, hafnium organometallic compounds and water vapor / oxygen are generally used as precursors. Hafnium organometallic compounds can be such as hafnium tetrachloride, tetra(diethylamino)hafnium, etc. When preparing TiO2 films, titanium organometallic compounds and water vapor / oxygen are generally used as precursors. Titanium organometallic compounds can be such as titanium tetrachloride, isopropyl titanate, etc.

[0025] Example 1

[0026] like Figure 1 As shown, this embodiment provides a sum-frequency crystal for an ultraviolet laser. The sum-frequency crystal has an incident light-transmitting surface and an output light-transmitting surface. A protective film is deposited on the output light-transmitting surface. The protective film includes at least one high-dielectric-constant metal oxide film layer and at least one photocatalytically active metal oxide film layer. The high-dielectric-constant metal oxide film layer and the photocatalytically active metal oxide film layer are alternately stacked. The end of the protective film closer to the output light-transmitting surface is the high-dielectric-constant metal oxide film layer, and the end of the protective film away from the output light-transmitting surface is the photocatalytically active metal oxide film layer.

[0027] Taking the high dielectric constant metal oxide film layer using HfO2 film layer and the photocatalytic active metal oxide film layer using TiO2 film layer as an example, the specific coating method of the protective film is as follows: on the light-emitting side of the sum-frequency crystal, first deposit a layer of HfO2 film layer, then deposit a layer of TiO2 film layer, repeating this process multiple times until the protective film reaches the preset thickness.

[0028] Furthermore, the protective film has a thickness of less than 20 nm, resulting in a thin overall thickness and minimal impact on the light spot pattern. The thickness of each single-layer HfO2 film is less than 5 nm, and the thickness of each single-layer TiO2 film is also less than 5 nm. Common lasers operate in the ultraviolet (UV) band between 200 nm and 380 nm. In this embodiment, an ultrathin film layer is used as the protective film. The thicknesses of the single-layer HfO2 and single-layer TiO2 films are chosen to be much lower than λ / 4, and the overall thickness is also lower than λ / 4. When light propagates through the film layer, no coherent destructive phenomenon occurs. Simultaneously, both the HfO2 and TiO2 films exhibit good transmittance in the UV band, thus maintaining high transmittance in the UV range.

[0029] Example 2

[0030] like Figure 2 As shown, this embodiment provides a sum-frequency crystal for an ultraviolet laser. The sum-frequency crystal for the ultraviolet laser has an incident light-transmitting surface and an output light-transmitting surface. A protective film is deposited on the output light-transmitting surface. The protective film includes at least one high-dielectric-constant metal oxide film layer and at least one photocatalytically active metal oxide film layer. The high-dielectric-constant metal oxide film layer and the photocatalytically active metal oxide film layer are alternately stacked. The end of the protective film closer to the output light-transmitting surface is the photocatalytically active metal oxide film layer, and the end of the protective film away from the output light-transmitting surface is the photocatalytically active metal oxide film layer.

[0031] Taking the high dielectric constant metal oxide film layer using HfO2 film layer and the photocatalytic active metal oxide film layer using TiO2 film layer as an example, the specific coating method of the protective film is as follows: on the light-emitting side of the sum-frequency crystal, first coat a TiO2 film layer, then coat a HfO2 film layer, repeat this process multiple times until the protective film is about the preset thickness, and finally coat a thinner TiO2 film layer on the outermost HfO2 film layer.

[0032] Furthermore, the thickness of the protective film is no greater than 1.5 times the wavelength, the thickness of a single HfO2 film layer is 1 / 4 of the wavelength, the thickness of a single TiO2 film layer is 1 / 4 of the wavelength, and the thickness of the TiO2 film layer at the end furthest from the light-emitting side of the light-transmitting surface is less than 5 nm. This embodiment uses a multilayer antireflection film as the protective film. The refractive index of HfO2 is 1.96, and the refractive index of TiO2 is 2.87. When light travels from a medium with a lower refractive index to a medium with a higher refractive index, a half-wave loss occurs. This half-wave loss occurs when light propagates between the λ / 4 thick HfO2 film layer and the λ / 4 thick TiO2 film layer, resulting in coherent destructive reflection, reduced reflectivity, and increased transmittance. Therefore, the antireflectivity of the film layer is improved. The composite stacking of multiple films can enhance the transmission bandwidth and transmittance of the film layer. Using a TiO2 film layer with a thickness of <5nm at the outermost edge of the protective film does not affect the overall transmittance of the film. Simultaneously, the photocatalytic activity of TiO2 can be utilized; when external volatile organic compounds are adsorbed onto the TiO2 film layer, TiO2 has a highly efficient catalytic decomposition capability under the assistance of high-energy photons, completely decomposing organic matter into CO2 and H2O molecules, reducing carbon buildup and film damage. The total thickness of the protective film is controlled within 1.5 times λ; excessive thickness reduces the quality of the film and increases its intrinsic absorption, therefore, it should not be too thick.

[0033] 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 principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A sum-frequency crystal for an ultraviolet laser, the sum-frequency crystal having an incident light-side transmission surface and an output light-side transmission surface, characterized in that: A protective film is deposited on the light-emitting side light-transmitting surface. The protective film includes at least one high dielectric constant metal oxide film layer and at least one photocatalytically active metal oxide film layer, and the high dielectric constant metal oxide film layer and the photocatalytically active metal oxide film layer are alternately stacked. The high dielectric constant metal oxide film layer is any one of HfO2 film layer, ZrO2 film layer, and Ta2O5 film layer.

2. The sum-frequency crystal of the ultraviolet laser as described in claim 1, characterized in that: The photocatalytically active metal oxide film is either a TiO2 film or an Fe3O4 film.

3. The sum-frequency crystal of the ultraviolet laser as described in claim 2, characterized in that: The high dielectric constant metal oxide film is an HfO2 film, and the photocatalytically active metal oxide film is a TiO2 film.

4. The sum-frequency crystal of the ultraviolet laser as described in any one of claims 1-3, characterized in that: The protective film is a high dielectric constant metal oxide film layer at the end closest to the light-emitting side of the light-transmitting surface, and a photocatalytically active metal oxide film layer at the end furthest from the light-emitting side of the light-transmitting surface.

5. The sum-frequency crystal of the ultraviolet laser as described in claim 4, characterized in that: The thickness of the protective film is less than 20 nm, the thickness of the single-layer high dielectric constant metal oxide film is less than 5 nm, and the thickness of the single-layer photocatalytic active metal oxide film is less than 5 nm.

6. The sum-frequency crystal of the ultraviolet laser as described in any one of claims 1-3, characterized in that: The protective film is a photocatalytically active metal oxide film layer at the end closest to the light-emitting side of the light-transmitting surface, and a photocatalytically active metal oxide film layer at the end furthest from the light-emitting side of the light-transmitting surface.

7. The sum-frequency crystal of the ultraviolet laser as described in claim 6, characterized in that: The thickness of the protective film is no greater than 1.5 times the wavelength, the thickness of a single layer of the high dielectric constant metal oxide film is 1 / 4 of the wavelength, the thickness of a single layer of the photocatalytically active metal oxide film is 1 / 4 of the wavelength, and the thickness of the photocatalytically active metal oxide film at the end away from the light-emitting side of the light-transmitting surface is less than 5 nm.

8. The sum-frequency crystal of the ultraviolet laser as described in claim 1, characterized in that: The high dielectric constant metal oxide film and the photocatalytically active metal oxide film are prepared by chemical vapor deposition or physical vapor deposition.

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