An ammonium salt of niobium tantalum oxyfluoride, a second-order nonlinear optical crystalline material, preparation and application thereof

Abstract

The application relates to a kind of ammonium salt of niobium tantalum oxyfluoride, preparation and application of second-order nonlinear optical crystalline material, the chemical formula of the material is (NH4)5(NbOF4)(TaF7)2, the crystalline material belongs to tetragonal system, space group is I4cm, and cell parameter is alpha=beta=gamma=90°, Z=2.Under the irradiation of 1064nm laser, the powder frequency doubling effect of the nonlinear optical crystal (NH4)5(NbOF4)(TaF7)2 in the application can reach 3.5 times of KH2PO4 (KDP) crystal, under the irradiation of 532nm laser, the powder frequency doubling effect is 0.35 times of beta-BaB2O4 (BBO) crystal, and phase matching can be realized.In addition, the ultraviolet absorption cutoff edge of the crystalline material is less than 195nm and shows moderate birefringence (0.095@546nm).The crystalline material provided by the application has important application value in the field of optoelectronics such as solid-state laser, spectral analysis, precision manufacturing and optical communication.

Description

Technical Field

[0001] This invention belongs to the field of nonlinear optical crystalline materials technology, and relates to a second-order nonlinear optical crystalline material of niobium tantalum oxyfluoride ammonium salt, its preparation and application. Background Technology

[0002] Nonlinear optical crystal materials with second-harmonic generation characteristics have important applications in precision manufacturing such as laser frequency conversion, micromachining, optoelectronic modulation, photolithography, and semiconductor detection because they can generate continuously tunable coherent light. An ideal nonlinear optical crystal should meet the following criteria: strong second-harmonic generation response, wide bandgap, and moderate birefringence. However, these optical performance requirements are mutually restrictive and difficult to achieve simultaneously in a single material. Therefore, researching novel ultraviolet nonlinear optical crystal materials that can achieve a balance between frequency doubling coefficient, optical bandgap, and birefringence is an important direction in the field of inorganic functional materials.

[0003] d 0 Metal oxyfluoride compounds are a class of nonlinear optical crystal materials with practical applications. However, existing d... 0 The absorption cutoff edge of metal oxyfluoride compounds is often greater than 200 nm, limiting their application in the short-wave ultraviolet band. This patent application provides a second-order nonlinear optical crystal of niobium tantalum oxyfluoride salt with deep ultraviolet transmission, strong frequency doubling effect, moderate birefringence, and phase matching in both ultraviolet and visible light bands. Summary of the Invention

[0004] The purpose of this invention is to provide a second-order nonlinear optical crystalline material of niobium tantalum oxyfluorate ammonium salt, its preparation, and its application. The chemical formula of the crystalline material is (NH4)5(NbOF4)(TaF7)2, belonging to the tetragonal crystal system with a space group of I4cm, and its structure contains strongly distorted d... 0 Metal-oxygen-fluorine polyhedra, as nonlinear optically active building blocks, are conducive to generating large microscopic second-order polarizability and strong optical anisotropy, resulting in significant powder frequency doubling and birefringence. The powder frequency doubling intensity under 1064 nm laser irradiation is 3.5 times that of KH₂PO₄ (KDP) crystal, and the powder frequency doubling effect under 532 nm laser irradiation is approximately 0.35 times that of β-BaB₂O₄ (BBO) crystal, with phase matching achieved in both cases. Furthermore, this crystalline material has an ultraviolet absorption cutoff edge of less than 195 nm and a moderate birefringence (0.095@546 nm), making it a promising candidate for applications in optoelectronic fields such as solid-state lasers, precision laser processing, and optical communication.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] One of the technical solutions of this invention provides a second-order nonlinear optical crystalline material of niobium tantalum oxyfluorate, with the chemical formula (NH4)5(NbOF4)(TaF7)2. This crystalline material belongs to the tetragonal crystal system, with a space group of I4cm and cell parameters of... α=β=γ=90°, Z=2.

[0007] Furthermore, the unit cell parameters are: α = β = γ = 90°, Z = 2. More preferably, the cell parameters are: α = β = γ = 90°, Z = 2. More preferably, the unit cell parameters are: α = β = γ = 90°, Z = 2. Most preferably, the cell parameters are... α=β=γ=90°, Z=2.

[0008] The crystal structure of the inorganic crystalline material (NH4)5(NbOF4)(TaF7)2 described in this invention is as follows: Figure 1 As shown, each Nb atom is coordinated with two O atoms and four F atoms to form a [NbO₂F₄] polyhedron. Each [NbO₂F₄] octahedron is interconnected via shared Nb-O bonds, forming a one-dimensional chain. This chain is perpendicular to the ab plane and parallel to each other, providing a large net dipole moment for the crystal material. Each Ta atom is connected to seven F atoms, forming a [TaF₇] polyhedron. Ammonium ions, acting as filler cations, connect the [TaF₇] polyhedra to the one-dimensional chains formed by the [NbO₂F₄] octahedrons via hydrogen bonds.

[0009] The second technical solution of the present invention provides a method for preparing a second-order nonlinear optical crystalline material of niobium tantalum oxyfluoride ammonium salt, wherein the chemical formula of the material is (NH4)5(NbOF4)(TaF7)2, characterized in that it is synthesized by a two-step hydrothermal method.

[0010] Step 1: Synthesis of the precursor (NH4)2TaF7. Ammonium source, tantalum source, fluorine source and water were mixed in proportion and placed in a reaction vessel. After heating and reacting, the mixture was slowly cooled to room temperature to obtain colorless and transparent (NH4)2TaF7 crystals.

[0011] Furthermore, in the first step reaction, the ammonium source is selected from one or more of the carbonate, nitrate, sulfate or hydrochloride of ammonium; the tantalum source is selected from tantalum pentoxide or tantalum pentachloride; and the fluorine source is a 40% hydrofluoric acid aqueous solution.

[0012] Furthermore, in the first step of the reaction, the molar ratio of ammonium ions to tantalum is (1.8-2.2):(0.9-1.1), and the volume ratio of the fluorine source to water is (1-3):(1-3).

[0013] Furthermore, in the first step of the reaction, the heating temperature is 200°C and the time is not less than 48 hours.

[0014] Step 2: Synthesis of the target crystal (NH4)5(NbOF4)(TaF7)2. The (NH4)2TaF7 obtained in Step 1, niobium source, fluorine source and water were mixed in proportion and placed in a reaction vessel. After heating and reacting, the mixture was slowly cooled to room temperature to obtain colorless and transparent (NH4)5(NbOF4)(TaF7)2 crystals.

[0015] Furthermore, in the second step of the reaction, the niobium source is selected from niobium pentoxide or niobium pentachloride; the fluorine source is a 40% hydrofluoric acid aqueous solution.

[0016] Furthermore, in the second step of the reaction, the molar ratio of (NH4)2TaF7 to niobium is (1.8-2.2):(0.8-1.2), and the volume ratio of the fluorine source to water is (1-3):(1-3).

[0017] Furthermore, in the second step of the reaction, the heating temperature is 200–220°C, and the time is no less than 72 hours.

[0018] The third technical solution of the present invention provides the application of niobium tantalum oxyfluorate ammonium salt second-order nonlinear optical crystalline material in laser frequency converters, optical parametric oscillators, optical parametric amplifiers and photoelectric rectifiers.

[0019] Furthermore, this material is used in laser frequency converters to output 532nm laser light under 1064nm laser irradiation.

[0020] Furthermore, this material is used in laser frequency converters to output 266nm laser light under 532nm laser irradiation.

[0021] Specifically, (NH4)5(NbOF4)(TaF7)2 crystal, as a second-order nonlinear optical crystalline material, outputs a strong 532nm laser under 1064nm laser irradiation, and its powder frequency doubling intensity is 3.5 times that of KDP crystal. Under 532nm laser irradiation, it can output a 266nm laser, and its powder frequency doubling intensity is 0.35 times that of BBO crystal, both of which can achieve phase matching.

[0022] This invention introduces d into perfluoride 0 A metal-oxygen-fluorine polyhedron containing two d-type elements was synthesized. 0A second-order nonlinear optical crystal of metal (NH4)5(NbOF4)(TaF7)2. This crystalline material possesses a uniformly arranged one-dimensional chain structure composed of metal-oxygen-fluorine octahedral active units. This one-dimensional chain structure is conducive to generating a large microscopic second-order polarizability and strong optical anisotropy. This results in a strong powder frequency doubling effect (3.5 × KDP) under 1064 nm laser irradiation and the ability to output 266 nm ultraviolet light (0.35 × BBO) under 532 nm laser irradiation. Simultaneously, the material exhibits a moderate birefringence (0.095@546 nm) and a short ultraviolet absorption cutoff edge (<195 nm).

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) This application provides a novel second-order nonlinear optical crystalline material (NH4)5(NbOF4)(TaF7)2, which exhibits a significant frequency doubling effect. Under 1064 nm laser irradiation, its powder frequency doubling intensity is 3.5 times that of KDP crystal. Under 532 nm laser irradiation, it outputs a strong 266 nm laser, with a powder frequency doubling intensity 0.35 times that of BBO crystal, and it can achieve phase matching. Furthermore, this crystalline material has a short ultraviolet absorption cutoff edge (<195 nm) and a moderate birefringence (0.095@546 nm). This crystalline material has broad application prospects in the field of nonlinear optics.

[0025] (2) This application also provides a method for preparing the second-order nonlinear optical crystalline material (NH4)5(NbOF4)(TaF7)2, which uses a two-step hydrothermal method to prepare colorless, transparent, high-quality (NH4)5(NbOF4)(TaF7)2 crystals. The synthesis method is simple, the synthesis conditions are mild, the yield is high, and it is easy to obtain millimeter-scale single crystals. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the crystal structure of (NH4)5(NbOF4)(TaF7)2;

[0027] Figure 2 The X-ray diffraction pattern of sample 1-1# obtained by fitting the crystal structure resolved by single-crystal X-ray diffraction is compared with the X-ray diffraction pattern obtained by grinding sample 1-1# into powder.

[0028] Figure 3 This is the ultraviolet-visible-near-infrared transmission spectrum of sample 1-1#;

[0029] Figure 4 This is the infrared spectrum of sample 1-1#;

[0030] Figure 5These are the second harmonic phase matching diagrams of sample 1-1# and standard KDP sample size in the 1064nm band;

[0031] Figure 6 This is a second harmonic phase matching diagram of sample 1-1# and standard BBO sample size in the 532nm band.

[0032] Figure 7 This is the birefringence test diagram of sample 1-1#. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0034] Example:

[0035] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0036] Example 1:

[0037] Preparation of samples 1# to 8#

[0038] Niobium source, (NH4)2TaF7 and fluorine source are mixed with water and added to a high-pressure autoclave lined with polytetrafluoroethylene. After heating in an oven and cooling to room temperature, colorless and transparent (NH4)5(NbOF4)(TaF7)2 crystals can be obtained.

[0039] The relationship between the types and proportions of raw materials, constant temperature, constant temperature time and sample number in the initial mixture is shown in Table 1.

[0040] Table 1. Correspondence between samples and raw materials and synthesis conditions.

[0041]

[0042] Crystal structure analysis of samples 1-1# to 1-8#

[0043] The structures of samples 1-1# to 1-8# were analyzed using single-crystal X-ray diffraction and powder X-ray diffraction methods.

[0044] Single-crystal X-ray diffraction measurements were performed on a Bruker D8 VENTURE CMOS X-ray single-crystal diffractometer (Germany). Data was collected at 100 K, and the diffraction source was graphite-monochromatic Mo-Kα rays. The scanning mode was ω; the data underwent absorption correction processing using the Multi-Scan method. Structural analysis was performed using the SHELXTL-2018 package; the positions of heavy atoms were determined using a direct method, and the coordinates of the remaining atoms were obtained using difference Fourier synthesis; F-based... 2 The full matrix least squares method is used to refine the coordinates and anisotropic thermal parameters of all atoms.

[0045] Powder X-ray diffraction tests were performed on a Bruker D8 X-ray powder diffractometer from Bruker GmbH, Germany. The test conditions were a fixed target, a monochromatic Cu-Kα light source, and a wavelength of [missing information]. The voltage and current are 40kV / 20A, the slits DivSlit / RecSlit / SctSlit are 2.00deg / 0.3mm / 2.00deg, the scanning range is 5~70°, and the scanning step size is 0.02°.

[0046] The single-crystal X-ray diffraction results show that samples 1-1# to 1-8# have the same chemical and crystal structures, with the chemical formula (NH4)5(NbOF4)(TaF7)2, belonging to the tetragonal crystal system, space group I4cm, and cell parameters of [missing information]. α=β=γ=90°, Z=2. Taking sample 1-1# as a typical example, its crystal structure data is as follows: α = β = γ = 90°, Z = 2. Its crystal structure is as follows: Figure 1 As shown.

[0047] The powder X-ray diffraction test results show that on the XRD patterns of samples 1-1# to 1-8#, the diffraction peaks of the samples and the diffraction peaks fitted by the single crystal data are in the same position, but the peak intensities are slightly different.

[0048] Taking sample 1-1# as a typical example, such as Figure 2 As shown, the X-ray diffraction pattern obtained by fitting the crystal structure obtained by single-crystal X-ray diffraction analysis is consistent with the X-ray diffraction pattern obtained by grinding sample 1-1# into powder. The peak positions are consistent, indicating that the obtained sample has high purity.

[0049] Ultraviolet-Visible-NearInfrared Transmission Spectroscopy Test

[0050] The UV-Vis-NIR transmission spectroscopy of samples 1-1# was measured using an Agilent Technologies Carry 5000 UV-Vis-NIR spectrophotometer. The results are as follows: Figure 3 As shown, by Figure 3 It can be seen that the ultraviolet absorption cutoff edge of this compound is less than 195 nm.

[0051] Infrared spectroscopy test

[0052] Infrared spectroscopy measurements of samples 1-1# were performed using a Nicoleti S10 Fourier transform infrared spectrometer from Thermo Fisher Scientific, Inc., USA. The results are as follows: Figure 4 As shown, the characteristic absorption peaks in the infrared spectrum confirm the presence of metal-oxygen-fluorine bonds and ammonium ions in the crystal structure.

[0053] Frequency doubling test experiment and results

[0054] The frequency doubling test experiment for sample 1-1# is as follows: A Q-switched Nd:YAG solid-state laser with a wavelength of 1064 nm was used as the fundamental frequency light to irradiate the test crystal powder. The generated second harmonic intensity was detected using an Ocean Optics Maya2000 Pro spectrometer. The crystal sample and the standard sample KDP ammonium crystal were ground together, and crystals of different sizes were separated using a standard sieve. The particle size range of ammonium ammonium ammonium was 26–50, 50–74, 74–105, 105–150, and 150–200 μm. The variation of the frequency doubling signal with particle size was observed to determine whether phase matching could be achieved. Under the same test conditions, the second harmonic intensity generated by the sample and the standard sample KDP was compared to obtain the relative magnitude of the sample's frequency doubling effect. Using the same test method, the test crystal powder was irradiated with a fundamental frequency light with a wavelength of 532 nm, and the generated second harmonic intensity was detected using an Ocean Optics Maya2000 Pro spectrometer. The variation of the frequency doubling signal with particle size was observed to determine whether phase matching could be achieved. Under the same test conditions, the intensity of the second harmonic generated by the sample and the standard sample BBO is compared to obtain the relative magnitude of the frequency doubling effect of the sample.

[0055] Test results show that compound (NH4)5(NbOF4)(TaF7)2 exhibits a significant powder frequency doubling effect, with the frequency doubling signal intensity being 3.5 times that of KDP crystal under 1064 nm laser irradiation. This crystalline material can achieve phase matching (e.g., ...) under 1064 nm laser irradiation. Figure 5 Under 532nm laser irradiation, the frequency doubling signal intensity is 0.35 times that of the BBO crystal. This crystalline material can achieve phase matching under 532nm laser irradiation (e.g., ...). Figure 6 ).

[0056] Birefringence test

[0057] Birefringence tests on samples 1-1# were performed on a Zeiss AXIO Scope 5 polarizing microscope equipped with a Berek compensator, using a light source with a wavelength of 546 nm. The experimental results are as follows: Figure 7 As shown, the optical path difference ΔR and crystal thickness T were measured. The test results show that the birefringence of sample 1-1# at 546 nm is 0.095.

[0058] Example 2

[0059] Preparation of (NH4)2TaF7 precursor.

[0060] Ammonium source, tantalum source and fluorine source are mixed with water and added to a high-pressure autoclave lined with polytetrafluoroethylene. After heating in an oven and cooling to room temperature, colorless and transparent (NH4)2TaF7 crystals can be obtained.

[0061] The relationship between the types and proportions of raw materials, constant temperature, constant temperature time and sample number in the initial mixture is shown in Table 2.

[0062] Table 2. Correspondence between samples and raw materials and synthesis conditions.

[0063]

[0064]

[0065] The description of the above embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A second-order nonlinear optical crystalline material of niobium tantalum oxyfluorate, characterized in that, With the chemical formula (NH4)5(NbOF4)(TaF7)2, this crystalline material belongs to the tetragonal crystal system, space group I4cm, and has cell parameters a = 14.0~17.0 Å, b = 14.0~17.0 Å, c = 7.0~8.0 Å, and V = 1700~2000 Å. 3 , α = β = γ = 90°, Z = 2.

2. The method for preparing the second-order nonlinear optical crystalline material of niobium-tantalum oxyfluorate according to claim 1, characterized in that, The method is a two-step hydrothermal method used to prepare the crystalline material with millimeter-scale dimensions.

3. The method for preparing the second-order nonlinear optical crystalline material of niobium tantalum oxyfluorate salt according to claim 2, characterized in that, The first step includes: Ammonium source, tantalum source and fluorine source are mixed with water in a certain proportion and subjected to hydrothermal reaction. After constant temperature heating and cooling process, ammonium heptafluorotantalate precursor with chemical formula (NH4)2TaF7 is prepared.

4. The method for preparing the second-order nonlinear optical crystalline material of niobium tantalum oxyfluorate according to claim 3, characterized in that, The ammonium source is selected from one or more of ammonium carbonates, nitrates, sulfates, or hydrochlorides; the tantalum source is selected from tantalum pentoxide or tantalum pentachloride; and the fluorine source is a 40% hydrofluoric acid aqueous solution.

5. The method for preparing the second-order nonlinear optical crystalline material of niobium tantalum oxyfluorate according to claim 3, characterized in that, The molar ratio of ammonium ions to tantalum is (1.8~2.2): (0.9~1.1), and the volume ratio of the fluorine source to water is (1~3): (1~3).

6. The method for preparing the second-order nonlinear optical crystalline material of niobium tantalum oxyfluorate salt according to claim 3, characterized in that, The heating temperature for the first hydrothermal reaction is 200 ℃, and the reaction time is no less than 48 hours.

7. The method for preparing the second-order nonlinear optical crystalline material of niobium tantalum oxyfluorate salt according to claim 3, characterized in that, The second step includes: mixing the ammonium heptafluorotantalate precursor with a niobium source, a fluorine source and water in a certain proportion, carrying out a hydrothermal reaction, and obtaining colorless and transparent (NH4)5(NbOF4)(TaF7)2 crystals through a constant temperature heating and cooling process.

8. The method for preparing the second-order nonlinear optical crystalline material of niobium tantalum oxyfluorate salt according to claim 7, characterized in that, The niobium source is selected from niobium pentoxide or niobium pentachloride; the fluorine source is a 40% hydrofluoric acid aqueous solution.

9. The method for preparing the second-order nonlinear optical crystalline material of niobium tantalum oxyfluorate according to claim 7, characterized in that, The molar ratio of (NH4)2TaF7 to niobium is (1.8~2.2): (0.8~1.2), and the volume ratio of the fluorine source to water is (1~3): (1~3).

10. The method for preparing the second-order nonlinear optical crystalline material of niobium tantalum oxyfluorate salt according to claim 7, characterized in that, The second step of the hydrothermal reaction is heated at a temperature of 200~220 ℃ for a time of not less than 72 hours.

11. The application of the niobium tantalum oxyfluoride ammonium salt second-order nonlinear optical crystalline material according to claim 1 in laser frequency converters, optical parametric oscillators, optical parametric amplifiers and photoelectric rectifiers.

12. The application of the niobium-tantalum oxyfluorate ammonium salt second-order nonlinear optical crystalline material according to claim 11, characterized in that, The material is used in a laser frequency converter to achieve the output of 532 nm laser under 1064 nm laser irradiation, and to output 266 nm laser under 532 nm laser irradiation.

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