Niobium tantalum oxyfluoride acid ammonium salt second-order nonlinear optical crystalline material and preparation and application thereof

Abstract

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

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nonlinear optical crystal materials, and relates to an ammonium salt of niobium tantalum oxyfluoride, a second-order nonlinear optical crystal material, and a preparation and application thereof. BACKGROUND

[0002] Nonlinear optical crystal materials with second harmonic generation characteristics have important applications in precision manufacturing such as laser frequency conversion, microprocessing, photoelectric modulation, photolithography and semiconductor detection, because they can generate continuous tunable coherent light. An ideal nonlinear optical crystal should meet the following standards: strong second harmonic generation response, wide band gap, moderate birefringence, etc. However, these optical performance requirements are mutually restrictive, and it is difficult to achieve balance among the frequency doubling coefficient, the optical band gap and the birefringence in the same material. Therefore, it is an important direction in the field of inorganic functional materials to study new ultraviolet nonlinear optical crystal materials that can achieve balance among the frequency doubling coefficient, the optical band gap and the birefringence.

[0003] d 0 Metal oxyfluoride compounds are a kind of nonlinear optical crystal materials with practical application value. However, the existing d 0 The absorption cutoff edge of the metal oxyfluoride compound is often greater than 200 nm, which limits its application in the short-wave ultraviolet waveband. The present application provides an ammonium salt of niobium tantalum oxyfluoride, which has deep ultraviolet transmission, strong frequency doubling effect, moderate birefringence and can achieve phase matching in the ultraviolet and visible wavebands. SUMMARY

[0004] The application aims to provide an ammonium salt of niobium tantalum oxyfluoride, a second-order nonlinear optical crystal material, and a preparation and application thereof. The chemical formula of the crystal material is (NH4)5(NbOF4)(TaF7)2, which belongs to the tetragonal system and has a space group of I4cm. The structure contains a strongly distorted d 0 Metal oxyfluoride polyhedron, which is conducive to generating large microsecond-order polarizability and strong optical anisotropy, so that the material exhibits significant powder frequency doubling effect and birefringence. The powder frequency doubling intensity under 1064 nm laser irradiation can reach 3.5 times that of KH2PO4 (KDP) crystal, and the powder frequency doubling effect under 532 nm laser irradiation is about 0.35 times that of β-BaB2O4 (BBO) crystal, and both can achieve phase matching. In addition, the ultraviolet absorption cutoff edge of the crystal material is less than 195 nm and has moderate birefringence (0.095@546 nm), which has important application potential in the fields of solid-state lasers, precision laser processes, optical communications and the like.

[0005] The object of the application can be achieved by 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] Further, in the first step reaction, the molar ratio of ammonium ion to tantalum element 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] Further, in the first step reaction, the heating temperature of the reaction is 200 DEG C, and the time is not less than 48 hours.

[0014] Second step: synthesis of the target crystal (NH4)5(NbOF4)(TaF7)2. The (NH4)2TaF7, the niobium source, the fluorine source and water obtained in the first step are mixed in proportion and then placed in a reaction container, and after heating reaction and slow cooling to room temperature, colorless transparent (NH4)5(NbOF4)(TaF7)2 crystal is obtained.

[0015] Further, in the second step reaction, the niobium source is selected from niobium pentoxide or niobium pentachloride; and the fluorine source is 40% mass fraction hydrofluoric acid aqueous solution.

[0016] Further, in the second step reaction, the molar ratio of (NH4)2TaF7 to niobium element 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] Further, in the second step reaction, the heating temperature of the reaction is 200-220 DEG C, and the time is not less than 72 hours.

[0018] The third technical scheme of the present application provides application of the niobium tantalum oxyfluoride ammonium salt second-order nonlinear optical crystalline material in a laser frequency converter, an optical parametric oscillator, an optical parametric amplifier and an optical rectifier.

[0019] Further, the material is used in a laser frequency converter, and 532nm laser is outputted under 1064nm laser irradiation.

[0020] Further, the material is used in a laser frequency converter, and 266nm laser is outputted under 532nm laser irradiation.

[0021] Specifically, the (NH4)5(NbOF4)(TaF7)2 crystal as the second-order nonlinear optical crystalline material can output strong 532nm laser under 1064nm laser irradiation, and the powder frequency doubling intensity is 3.5 times that of KDP crystal; the (NH4)5(NbOF4)(TaF7)2 crystal can output 266nm laser under 532nm laser irradiation, and the powder frequency doubling intensity is 0.35 times that of BBO crystal, and phase matching can be realized.

[0022] The present application introduces d 0 The metal oxyfluoride polyhedron is synthesized, and one example containing two d 0A metal second-order nonlinear optical crystal (NH4)5(NbOF4)(TaF7)2. The crystalline material has a one-dimensional chain structure composed of metal oxyfluoride octahedral active units, and is uniformly arranged. The one-dimensional chain structure is conducive to generating large microsecond polarization rate and strong optical anisotropy. This makes the material exhibit strong powder frequency doubling effect (3.5 times of KDP) under 1064 nm laser irradiation, and can output 266 nm ultraviolet light (0.35 times of BBO) under 532 nm laser irradiation. At the same time, the material has moderate birefringence (0.095@546 nm) and short ultraviolet absorption cutoff edge (<195 nm).

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

[0024] (1) The present application provides a new second-order nonlinear optical crystalline material (NH4)5(NbOF4)(TaF7)2, which has a significant frequency doubling effect. The powder frequency doubling intensity under 1064 nm laser irradiation is 3.5 times of that of KDP crystal, and strong 266 nm laser can be outputted under 532 nm laser irradiation, and the powder frequency doubling intensity is 0.35 times of that of BBO crystal, and phase matching can be realized. In addition, the crystalline material has a short ultraviolet absorption cutoff edge (<195 nm) and moderate birefringence (0.095@546 nm). The crystalline material has a wide application prospect in the field of nonlinear optics.

[0025] (2) The present application also provides a preparation method of the second-order nonlinear optical crystalline material (NH4)5(NbOF4)(TaF7)2. A colorless transparent and high-quality (NH4)5(NbOF4)(TaF7)2 crystal is prepared by a two-step hydrothermal method. The synthesis method is simple, the synthesis conditions are mild, the yield is high, and millimeter-level single crystals are easy to obtain. BRIEF DESCRIPTION OF DRAWINGS

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

[0027] Figure 2 is a comparison between the X-ray diffraction spectrum of sample 1-1# obtained by fitting the crystal structure according to single crystal X-ray diffraction and the spectrum obtained by X-ray diffraction test after sample 1-1# is ground into powder;

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

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

[0030] Figure 5is a second harmonic phase matching diagram of sample 1-1# and standard sample KDP at a sample size in a 1064 nm waveband;

[0031] Figure 6 is a second harmonic phase matching diagram of sample 1-1# and standard sample BBO at a sample size in a 532 nm waveband;

[0032] Figure 7 is a birefringence test diagram of sample 1-1#. DETAILED DESCRIPTION

[0033] The present application will be described in detail below with reference to the drawings and specific examples. The present embodiment is implemented on the premise of the technical solution of the present application, and gives a detailed implementation and specific operation process, but the protection scope of the present application is not limited to the following examples.

[0034] Embodiment:

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

[0036] Embodiment 1:

[0037] Preparation of samples 1#-8#

[0038] The niobium source, (NH4)2TaF7 and fluorine source were mixed with water and added to a polytetrafluoroethylene lined autoclave, which was heated in an oven and then cooled to room temperature to obtain colorless transparent (NH4)5(NbOF4)(TaF7)2 crystals.

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

[0040] Table 1: Correspondence of samples with raw materials and synthesis conditions

[0041]

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

[0043] Single crystal X-ray diffraction and powder X-ray diffraction methods were used to analyze the structure of samples 1-1#-1-8#.

[0044] The single crystal X-ray diffraction test was performed on a D8 VENTURE CMOS X X-ray single crystal diffractometer of Bruker Company in Germany. The data collection temperature was 100 K, and the diffraction light source was graphite monochromatic Mo-Kα ray 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] The infrared spectrum test of sample 1-1# was performed on a Nicolet iS10 Fourier infrared spectrometer of Thermo Fisher Scientific Corporation. The results are shown in Figure 4 Figure 1, and the characteristic absorption peaks in the infrared spectrum confirm the existence 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 of sample 1-1# is as follows: a Q-switched Nd:YAG solid-state laser is used to generate laser light with a wavelength of 1064 nm and the laser light is used as the fundamental light to irradiate the crystal powder to be tested, and an Ocean Optics Maya2000 Pro spectrometer is used to detect the generated second harmonic intensity. The crystal sample is ground with a standard sample KDP crystal ammonium, and different particle sizes of the crystal are sieved out by a standard sieve, with the particle size range of the ammonium being 26-50, 50-74, 74-105, 105-150, and 150-200 μm. The change rule of the frequency doubling signal with the particle size is observed to determine whether phase matching can be achieved. Under the same test conditions, the second harmonic intensities generated by the sample and the standard sample KDP are compared to obtain the relative size of the frequency doubling effect of the sample. The same test method is used to irradiate the crystal powder to be tested with fundamental light with a wavelength of 532 nm, and an Ocean Optics Maya2000 Pro spectrometer is used to detect the generated second harmonic intensity. The change rule of the frequency doubling signal with the particle size is observed to determine whether phase matching can be achieved. Under the same test conditions, the second harmonic intensities generated by the sample and the standard sample BBO are compared to obtain the relative size of the frequency doubling effect of the sample.

[0055] The test results show that the compound (NH4)5(NbOF4)(TaF7)2 has a significant powder frequency doubling effect, and under 1064 nm laser irradiation, the frequency doubling signal intensity is 3.5 times that of a KDP crystal. The crystalline material can achieve phase matching under 1064 nm laser irradiation (as shown in Figure 5 ). Under 532 nm laser irradiation, the frequency doubling signal intensity is 0.35 times that of a BBO crystal. The crystalline material can achieve phase matching under 532 nm laser irradiation (as shown in Figure 6 ).

[0056] Birefringence test

[0057] The birefringence test of sample 1-1# was performed on a Zeiss AXIO Scope 5 polarizing microscope equipped with a Berek compensator, and the wavelength of the experimental light source was 546 nm. The experimental results are shown in Figure 7 Figure 2, and the optical path difference ΔR and the thickness T of the crystal 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] The ammonium source, the tantalum source and the fluorine source were mixed with water, added to a high-pressure vessel lined with polytetrafluoroethylene, and after heating in an oven, cooled to room temperature to obtain colorless transparent (NH4)2TaF7 crystals.

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

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

[0063]

[0064]

[0065] The foregoing description of the examples has been set forth to enable any person skilled in the art to make and use the invention. Modifications to these examples will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other examples without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the examples described herein and that modifications can be made by those skilled in the art without departing from the scope of the present invention.

Claims

1. An ammonium niobium tantalum oxyfluoride salt second order nonlinear optical crystalline material, characterized in that, The chemical formula of the crystal material is (NH4)5(NbOF4)(TaF7)2, the crystal material belongs to a tetragonal system, a space group is I4cm, and a cell parameter is 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 for preparing the millimeter-sized crystalline material.

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 comprises mixing an ammonium source, a tantalum source and a fluorine source with water in a certain proportion, and performing a hydrothermal reaction, and then performing a constant-temperature heating and cooling process to prepare an ammonium heptafluotantalate precursor with a chemical formula of (NH4)2TaF7.

4. The method for preparing the ammonium heptafluorotantalate precursor according to claim 3, characterized in that, The ammonium source is selected from one or more of carbonates, nitrates, sulfates or hydrochlorides of ammonium; 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 of claim 3 for preparing ammonium heptafluoroantimonate precursor, characterized in that, The molar ratio of ammonium ions to tantalum elements 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 ammonium fluorotantalate precursor according to claim 3, characterized in that, The heating temperature of the first-step hydrothermal reaction is 200°C, and the reaction time is not less than 48 hours.

7. The method for preparing the second-order nonlinear optical crystalline material of niobium tantalum oxyfluorate according to claim 2, characterized in that, The second step comprises mixing the ammonium heptafluotantalate precursor prepared in claim 3 with a niobium source, a fluorine source and water in a certain proportion, performing a hydrothermal reaction, and then performing a constant-temperature heating and cooling process to obtain colorless and transparent (NH4)5(NbOF4)(TaF7)2 crystals.

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; and 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 elements 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 ammonium fluorotantalate second-order nonlinear optical crystalline material according to claim 7, characterized in that, The heating temperature of the second-step hydrothermal reaction is 200-220°C, and the reaction time is not less than 72 hours.

11. Application of the niobium-tantalum-oxygen-fluorine ammonium salt second-order nonlinear optical crystalline material of claim 1 in a laser frequency converter, an optical parametric oscillator, an optical parametric amplifier and an optical rectifier.

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

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