A hafnium fluorosulfate deep ultraviolet frequency doubling crystal material, its preparation and application

Abstract

The present invention relates to a hafnium fluorosulfate deep ultraviolet frequency doubling material and its preparation and application. The chemical formula of the crystal material is Hf(SO4)F2, which belongs to the orthorhombic system, with the space group of Pca21. The unit cell parameters are #imgabs0##imgabs1#α = β = γ = 90°, Z = 4, and the unit cell volume is #imgabs2#. The powder frequency doubling effect of the crystal Hf(SO4)F2 of the present invention under the irradiation of 1064 nm laser is 2.5 times that of KH2PO4 (KDP), and phase matching can be achieved under the irradiation of 1064 nm laser. Compared with the prior art, the d 0 Transition metal sulfates have a wide light transmission range in the deep ultraviolet-visible light band, with an ultraviolet absorption cut-off edge less than 190 nm, and have broad application prospects in the field of deep ultraviolet lasers.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical crystal materials, and relates to a hafnium fluorosulfate deep ultraviolet frequency doubling crystal material and its preparation and application. Background Art

[0002] Nonlinear optical crystal materials with second harmonic generation (SHG) properties have important applications in precision manufacturing such as laser frequency conversion, microfabrication, optoelectronic modulation, lithography, and semiconductor detection because they can generate continuously tunable coherent light. Frequency doubling crystal materials with second harmonic generation (SHG) properties have important applications in precision manufacturing such as laser frequency conversion, microfabrication, optoelectronic modulation, lithography, and semiconductor detection because they can generate continuously tunable coherent light. An ideal frequency doubling crystal should meet the following criteria: strong SHG response, large bandgap, and good physical and chemical stability, etc. However, these factors restrict each other and it is difficult to achieve a balance in the same material. At the same time, to test the basic physical properties (including nonlinear optical properties) of a frequency doubling crystal, the size of the crystal needs to reach the millimeter level. The frequency doubling crystals grown in the laboratory are often small in size and it is difficult to reach this specification, thus hindering the characterization of their related optical properties and practical applications. Therefore, developing a method to grow large-size nonlinear optical crystals is also a very important task. At the same time, there have been no research reports on deep ultraviolet hafnium fluorosulfate-based frequency doubling materials. Summary of the Invention

[0003] The purpose of the present invention is to provide a hafnium fluorosulfate deep ultraviolet frequency doubling crystal material and its preparation and application.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] One of the technical solutions of the present invention provides a hafnium fluorosulfate deep ultraviolet frequency doubling crystal material, characterized in that the chemical formula of the crystal material is Hf(SO4)F2, belonging to the orthorhombic system, with its space group being Pca21, and the unit cell parameters are α = β = γ = 90°, Z = 4, and the unit cell volume is

[0006] Furthermore, the absorption cut-off edge of the crystal material is less than 190 nm and is in the deep ultraviolet band.

[0007] The crystal structure of Hf(SO4)F2 of the present invention is as follows: Hf 4+The cations are coordinated with four O atoms and four F atoms to form [HfF4O4] polyhedra. Each [HfF4O4] polyhedron is connected to four adjacent polyhedra through corner-sharing F atoms. The further connectivity of [HfF4O4] polyhedra forms a [HfF2O4] layered structure in the ac plane, and the oxygen atoms in the [SO4] groups connect between the layers, constructing a layer-columnar three-dimensional framework.

[0008] The second technical solution of the present invention provides a preparation method of a hafnium fluorosulfate deep ultraviolet frequency doubling crystal material. A hafnium source, a fluorine source, sulfuric acid and water are mixed to obtain an initial mixed raw material, and hydrothermal crystallization is carried out to obtain the target product.

[0009] Further, the hafnium source is hafnium dioxide.

[0010] Further, the fluorine source is hydrofluoric acid.

[0011] Further, the molar ratio of hafnium element, fluorine element, sulfuric acid and water in the initial mixed raw material is 1:(0.5 - 50):(0.5 - 50):(1 - 50).

[0012] Further, the temperature of hydrothermal crystallization is 200 - 230 °C, and the time is not less than 24 h. Preferably, the temperature of hydrothermal conditions is 215 - 230 °C, and the crystallization time is not less than 48 h.

[0013] Further, after the hydrothermal crystallization is completed, it is cooled to room temperature at a rate of 0.5 - 15 °C / h. Preferably, the cooling rate is 0.5 - 6 °C / h.

[0014] The third technical solution of the present invention provides an application of a hafnium fluorosulfate deep ultraviolet frequency doubling crystal material. This crystal material is used for deep ultraviolet laser frequency conversion output. This Hf(SO4)F2 crystal material has a large frequency doubling effect. Under the irradiation of 1064 nm laser, its powder frequency doubling effect is about 2.5 times that of KH2PO4 crystal, and it is type I phase matching. In addition, the ultraviolet absorption cut-off edge of this crystal material is less than 190 nm, located in the deep ultraviolet band. Therefore, this crystal material has broad application prospects in the field of deep ultraviolet nonlinear optics.

[0015] Specifically, this crystal material has broad application prospects in the fields of laser frequency conversion, photoelectric modulation, laser signal holographic storage, etc., such as it can be used in a laser frequency converter from deep ultraviolet to visible light band.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The present invention provides a new inorganic crystal material, Hf(SO4)F2, which has a large second harmonic generation (SHG) effect. Under 1064 nm laser irradiation, it is about 2.5 times the SHG intensity of KH2PO4 crystal and can achieve type-I phase matching. In addition, the ultraviolet absorption cut-off edge of this crystal material is less than 190 nm, showing broad application prospects in the fields of laser frequency conversion, electro-optical modulation, laser signal holographic storage, etc.;

[0018] (2) The present invention provides a preparation method for the millimeter-scale Hf(SO4)F2 crystal. By using the hydrothermal method with mild reaction conditions, high-purity crystalline samples can be obtained in high yield through hydrothermal crystallization at a temperature of 200 - 230 °C, and the length of the produced crystal can reach 1.2 mm. The method is simple and the conditions are mild, which is conducive to large-scale industrial production;

[0019] (3) The Hf(SO4)F2 crystal material of the present invention can be applied to a laser frequency converter and can be used to output deep ultraviolet, ultraviolet, and visible light laser beams as second-harmonic and fourth-harmonic waves. Description of the Drawings

[0020] Figure 1 is a crystal photograph of Hf(SO4)F2;

[0021] Figure 2 is a schematic diagram of the crystal structure of Hf(SO4)F2;

[0022] Figure 3 is a comparison of X-ray diffraction patterns; where (a) is the pattern obtained by X-ray diffraction testing after grinding sample 1# into powder; (b) is the X-ray diffraction pattern simulated according to the crystal structure analyzed from the single-crystal X-ray diffraction data of sample 1#;

[0023] Figure 4 is the ultraviolet-visible-near-infrared transmission spectrum of sample 1#;

[0024] Figure 5 is the infrared spectrum (2.5 - 25 μm) of sample 1#;

[0025] Figure 6 is the thermogravimetric analysis pattern of sample 1#;

[0026] Figure 7 is the second harmonic signal diagram of sample 1# and the KH2PO4 sample with dimensions in the range of 105 - 150 μm;

[0027] Figure 8 is the second harmonic phase matching diagram of sample 1# in the 1.064 μm band. Detailed Embodiments

[0028] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0029] In the following embodiments, unless otherwise specified for raw materials or processing techniques, it means that they are all conventional commercially available raw materials or conventional processing techniques in the art.

[0030] Example 1:

[0031] A hafnium source, a fluorine source, sulfuric acid and water are mixed in a certain proportion to form a starting material, which is sealed in a hydrothermal reaction kettle with a polytetrafluoroethylene liner. The temperature is raised to the crystallization temperature, and after maintaining a constant temperature for a period of time, the temperature of the reaction system is slowly lowered to room temperature at a certain rate, followed by filtration and washing, and then Hf(SO4)F2 crystals with a length of 1.2 mm and a transparent block shape can be obtained (as Figure 1 shown).

[0032] The relationship between the types and ratios of raw materials in the initial mixture, the crystallization temperature, the crystallization time and the sample numbers is shown in Table 1.

[0033] Table 1 Correspondence between samples and raw materials used and synthesis conditions

[0034]

[0035] Example 2 Crystal Structure Analysis

[0036] Single crystal X-ray diffraction and powder X-ray diffraction methods are used to analyze the structures of samples 1# to 6#.

[0037] Among them, the single crystal X-ray diffraction test is carried out on a D8 VENTURE CMOS X type X-ray single crystal diffractometer of Bruker Company in Germany. The crystal size is 0.12×0.19×0.15 mm 3 ; the data collection temperature is 293 K, and the diffraction light source is graphite-monochromatized Mo-Kα ray The scanning mode is ω; the data is subjected to absorption correction processing by the Multi-Scan method. The structure analysis is completed using the SHELXTL-97 program package; the positions of heavy atoms are determined by the direct method, and the coordinates of the remaining atoms are obtained by the difference Fourier synthesis method; the coordinates of all atoms and the anisotropic thermal parameters are refined by the full matrix least squares method based on F 2 .

[0038] The powder X-ray diffraction test is carried out on a Bruker D8 type X-ray powder diffractometer of Bruker Company in Germany. The test conditions are a fixed target monochromatic light source Cu-Kα, and the wavelength The voltage and current are 40 kV / 20 A, the slits DivSlit / RecSlit / SctSlit are 2.00 deg / 0.3 mm / 2.00 deg respectively, the scanning range is 5–70°, and the scanning step is 0.02°.

[0039] Among them, the single-crystal X-ray diffraction test results show that Samples 1# to 6# have the same chemical structural formula and crystal structure. The chemical formula is Hf(SO4)F2, which belongs to the orthorhombic system, and its space group is Pca21. The unit cell parameters are α = β = γ = 90°, Z = 4, and the unit cell volume is

[0040] Taking Sample 1# as a typical representative, its crystal structure data are α = β = γ = 90°, Z = 4, and the unit cell volume is Its crystal structure is as Figure 2 shown.

[0041] The powder X-ray diffraction test results show that on the XRD spectra of Samples 1# to 6#, the peak positions of each sample are basically the same, and the peak intensities are slightly different.

[0042] Taking Sample 1# as a typical representative, as Figure 3 shown. Figure 3 The spectrum obtained by X-ray diffraction test after grinding Sample 1# into powder in (a) is consistent with the X-ray diffraction spectrum simulated according to the crystal structure analyzed by its single-crystal X-ray diffraction in Figure 3 (b) in terms of peak position and peak intensity, indicating that the obtained sample has a high purity.

[0043] Example 3 Ultraviolet Transmission Spectrum Test

[0044] The transmission spectrum test of Sample 1# was carried out on an Agilent Cary 5000 ultraviolet-visible-near-infrared spectrophotometer. The results are as Figure 4 shown. It can be seen from Figure 4 that this compound has a wide optical transmission range, the ultraviolet absorption cut-off edge is less than 190 nm, and the corresponding optical band gap is greater than 6.53 eV.

[0045] Example 4 Infrared Spectrum Test

[0046] The infrared spectrum test of Sample 1# was carried out on a Thermo Fisher Scientific Nicolet iS10 Fourier transform infrared spectrometer. The results are as Figure 5 shown. It can be seen from Figure 5 that this compound has a wide optical transmission range.

[0047] Example 5 Thermogravimetric Test

[0048] The thermogravimetric test of Sample 1# was carried out on a Netzsch STA 409PC thermogravimetric analyzer manufactured by Netzsch Gerätebau GmbH in Germany. The results are as Figure 6 shown, and it can be seen from Figure 6 this that the compound can be stable up to 630 °C and has good thermal stability.

[0049] Example 6 Second-Harmonic Generation Test Experiment and Results

[0050] The second-harmonic generation test experiment of Sample 1# is as follows: The laser with a wavelength of 1064 nm generated by a Q-switched Nd:YAG solid-state laser was used as the fundamental frequency light to irradiate the tested crystal powder. A photomultiplier tube was used to detect the generated second harmonic, and an oscilloscope was used to display the harmonic intensity. The crystal sample and the control sample KH2PO4 crystal were ground separately, and crystals with different particle sizes were screened out using a standard sieve. The particle size ranges were less than 26, 26 - 50, 50 - 74, 74 - 105, 105 - 150, 150 - 200, and 200 - 280 μm respectively. Observe the trend of the second-harmonic signal intensity changing with the particle size to judge whether it can achieve phase matching. Under the same test conditions, compare the intensities of the second harmonics generated by the sample and the KH2PO4 sample to obtain the relative magnitude of the second-harmonic generation effect of the sample.

[0051] The test results show that the compound Hf(SO4)F2 crystal has a large second-harmonic generation effect. Under the irradiation of a 1064 nm wavelength laser, the second-harmonic signal intensity is 2.5 times that of the control sample KH2PO4 crystal (as Figure 7 shown), and type-I phase matching can be achieved (as Figure 8 shown).

[0052] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. Those skilled in the art can obviously make various modifications to these embodiments easily and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. Application of a hafnium fluorosulfate deep ultraviolet frequency doubling crystal material, characterized in that, This crystal material is used for deep ultraviolet laser frequency conversion output; The chemical formula of the crystal material is Hf(SO4)F2, belonging to the orthorhombic system, and its space group is Pca 21, and the unit cell parameters are a a = 7.70~7.90 Å, b b = 5.87~6.07 Å, c c = 7.72~7.92 Å, α α = β β = γ γ = 90°, Z Z = 4, and the unit cell volume is V V = 381.07 Å 3 ; The absorption cut-off edge of this crystal material is less than 190 nm and is within the deep ultraviolet band; This crystal material is prepared by the following method: Take a hafnium source, a fluorine source, sulfuric acid and water and mix them to obtain an initial mixed raw material, and perform hydrothermal crystallization to obtain the target product; The hafnium source is hafnium dioxide; The fluorine source is hydrofluoric acid; The molar ratio of hafnium element, fluorine element, sulfuric acid and water in the initial mixed raw material is 1: (0.5~50): (0.5~50): (1~50); The temperature of hydrothermal crystallization is 200 - 230 °C and the time is not less than 24 h; After hydrothermal crystallization is completed, it is cooled to room temperature at a rate of 0.5~15 °C / h.

2. The application of the hafnium fluorosulfate deep ultraviolet frequency doubling crystal material according to claim 1, characterized in that, This crystal material is used in a laser frequency converter in the range from deep ultraviolet to visible light band.

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