Compound cesium ammonium fluoroborate, cesium ammonium fluoroborate nonlinear optical crystal, and preparation method and application of compound cesium ammonium fluoroborate nonlinear optical crystal

Abstract

The invention provides a preparation method and application of a compound cesium ammonium fluoborate and a cesium ammonium fluoborate nonlinear optical crystal. The chemical formula of the compound is CsNH4B8O12F2; the chemical formula of the crystal is CsNH4B8O12F2, the crystal belongs to a trigonal system, the space group is P321, and the unit cell parameters are as follows: a = b = 6.5858 (4) + / -0.02, c = 7.8163 (6) + / -0.02, alpha = beta = 90 degrees, gamma = 120 degrees and Z = 1. The crystal is grown by adopting a vacuum high-temperature solution method, a room-temperature solution method or a hydrothermal method, and the ultraviolet transmission cut-off edge of the crystal is lower than 190 nm. The nonlinear optical effect of the crystal is about 2.5 times of that of KH2PO4 (KDP), and the shortest I-type phase matching wavelength is 175.5 nm. The crystal has the advantages of simple preparation method, low toxicity of used initial raw materials, small harm to human bodies, stable physical and chemical properties, uniaxial crystal, easiness in application and the like. The method can be widely applied to nonlinear optical devices such as ultraviolet and deep ultraviolet all-solid-state lasers, optical parametric oscillators and the like.

Description

Technical Field

[0001] The present invention relates to a compound cesium ammonium fluoroborate and a cesium ammonium fluoroborate nonlinear optical crystal, as well as a preparation method and application thereof. Background Art

[0002] Lasers play an increasingly important role in scientific research, industry, transportation, national defense, and medical care. Due to the limitations of laser crystal excitation materials, only certain wavelengths of laser light can be output. Using nonlinear optical crystals to directly double the output light of existing laser crystals is the simplest means of obtaining ultraviolet / deep ultraviolet coherent light. In view of the strict requirements on the physical and chemical stability of materials when working under ultraviolet / deep ultraviolet high-power lasers, the current research on ultraviolet and deep ultraviolet nonlinear optical crystals is mainly focused on inorganic materials, and borate crystals with excellent performance are undoubtedly a system that has attracted much attention. Currently, the well-known ultraviolet / deep ultraviolet borate nonlinear optical crystals are KBe2BO3F2 (KBBF), LiB3O5 (LBO), β-BaB2O4 (β-BBO), CsLiB6O 10 KBBF is the only material practically suitable for direct sextupled all-solid-state lasers producing deep-ultraviolet coherent light. However, its long crystal growth cycle, the use of highly toxic BeO-containing raw materials, and its layered growth behavior significantly limit its application. Therefore, the search for novel deep-ultraviolet nonlinear optical crystals with superior performance is extremely urgent.

[0003] In previous studies, there have been ammonium fluoroborate compounds and ammonium fluoroborate nonlinear optical crystals (patent application number 201611128283.3), cesium fluoroborate compounds and cesium fluoroborate nonlinear optical crystals (patent application number 201710215337.8), rubidium fluoroborate compounds and rubidium fluoroborate nonlinear optical crystals (patent application number 201710536366.4), sodium tetraborate monofluoride compounds and sodium tetraborate monofluoride nonlinear optical crystals (patent application number 201710536366.5), and cesium fluoroborate compounds and cesium fluoroborate nonlinear optical crystals (patent application number 201710536366.6). Patent application number 201810001471.2), potassium cesium fluoroborate and potassium cesium fluoroborate nonlinear optical crystals (patent application number 201710845730.5), as well as compounds cesium rubidium fluoroborate and cesium rubidium fluoroborate nonlinear optical crystals and preparation methods and uses (patent application number 201710845438.3), compounds ammonium rubidium fluoroborate and ammonium rubidium fluoroborate nonlinear optical crystals (patent application number 202310154913.8) and other related patents.

[0004] Compared with ammonium fluoroborate NH4B4O6F, rubidium fluoroborate RbB4O6F, sodium tetraborate monofluoride NaB4O6F, and cesium fluoroborate CsB4O6F, ammonium fluoroborate (NH4)x Rb 2-x B8O 12 The main difference between F2(0<x<2) is that cesium ammonium fluoroborate CsNH4B8O 12 F2 crystallizes in the trigonal system, which is a high-order crystal system with a space group of P321. Its molecular formula, crystal structure and optical properties are completely different from the former. In the application of laser devices, cesium ammonium fluoroborate CsNH4B8O, which belongs to the trigonal system, 12 F2 is a uniaxial crystal, offering advantages such as easier processing, easier phase matching, and greater ease of use. Cesium ammonium fluoroborate can be grown using a self-fluxing agent. This not only mitigates the potential safety issues associated with excessive pressure and explosion during the growth of ammonium fluoroborate NH4B4O6F in a sealed system, but also addresses the potential for impurities introduced by the addition of a co-fluxing agent during the growth of rubidium fluoroborate (RbB4O6F) and cesium fluoroborate (CsB4O6F).

[0005] Compared with cesium potassium fluoroborate CsKB8O 12 F2, cesium rubidium fluoroborate CsRbB8O 12 The main difference between F2 and cesium ammonium fluoroborate CsNH4B8O 12 The ammonium cations in F2 connect to oxygen and fluorine atoms through hydrogen bonds. Compared to the ionic bonds formed by metal cations, hydrogen bonds are more powerful, improving the layered growth habit. Ammonium-containing raw materials have lower melting points and can also act as self-fluxing agents, further lowering the melting point of the system without introducing impurities, which is conducive to the growth of large, high-optical-quality single crystals. Summary of the Invention

[0006] The purpose of the present invention is to provide a compound cesium ammonium fluoroborate, the chemical formula of which is CsNH4B8O 12 F2 is made by vacuum high temperature solution method.

[0007] Another object of the present invention is to provide a cesium ammonium fluoroborate nonlinear optical crystal, the crystal chemical formula of which is CsNH4B8O 12 F2, belongs to the trigonal system, the space group is P321, and the unit cell parameters are α=β=90°, γ=120°, Z=1.

[0008] Another object of the present invention is to provide a method for preparing cesium ammonium fluoroborate nonlinear optical crystals, which comprises growing the crystals by using a vacuum high-temperature solution method, a room-temperature solution method or a hydrothermal method.

[0009] Another object of the present invention is to provide uses of cesium ammonium fluoroborate nonlinear optical crystals.

[0010] The compound of the present invention is cesium ammonium fluoroborate, the chemical formula of which is CsNH4B8O 12 F2, with a molecular weight of 467.43, was prepared using a vacuum high-temperature solution method.

[0011] The preparation method of the compound cesium ammonium fluoroborate adopts a vacuum high-temperature solution method, and the specific operation is carried out according to the following steps:

[0012] The molar ratio of Cs:NH4:B:F is 0.5-2:0.5-2:3-10:0.5-2. The Cs-containing compound, the B-containing compound and the F-containing compound are first mixed uniformly, and pre-calcined at 100°C in a muffle furnace. Then, the NH4-containing compound is added, mixed uniformly, and then loaded into a Φ40mm quartz tube. The quartz tube is evacuated to a vacuum degree of 1×10 -3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 300-500 ° C, kept warm for 3-168 hours, and slowly cooled to obtain the compound CsNH4B8O 12 F2, wherein the Cs-containing compound is CsCl, CsOH, CsNO3, Cs2CO3, CsHCO3, CH3COOCs, CsF or CsBF4, the B-containing compound is H3BO3, HBO2 or B2O3, the NH4-containing compound is NH4Cl, NH4BF4, NH4HF2, (NH4)2CO3, NH4HCO3 or NH4F, and the F-containing compound is LiBF4, HF, HBF4, NH4BF4, NH4F, NH4HF2, CsF or CsBF4.

[0013] A cesium ammonium fluoroborate nonlinear optical crystal, the chemical formula of the crystal is CsNH4B8O 12 F2, belongs to the trigonal system, the space group is P321, and the unit cell parameters are α=β=90°, γ=120°, Z=1.

[0014] The method for preparing the cesium ammonium fluoroborate nonlinear optical crystal adopts a vacuum high-temperature solution method, a room-temperature solution method or a hydrothermal method to prepare the crystal.

[0015] The vacuum high-temperature solution method for growing cesium ammonium fluoroborate nonlinear optical crystals is carried out according to the following steps:

[0016] a. In the molar ratio of Cs:NH4:B:F=0.5-2:0.5-2:3-10:0.5-2, the Cs-containing compound, the B-containing compound and the F-containing compound were first mixed uniformly, and pre-calcined at 100°C in a muffle furnace. Then, the NH4-containing compound was added, mixed uniformly, and then loaded into a Φ40mm quartz tube. The quartz tube was evacuated to a vacuum degree of 1×10 -3Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 300-500 ° C, kept warm for 3-168 hours, and slowly cooled to obtain the compound CsNH4B8O 12 F2, wherein the Cs-containing compound is CsCl, CsOH, CsNO3, Cs2CO3, CsHCO3, CH3COOCs, CsF or CsBF4, the B-containing compound is H3BO3, HBO2 or B2O3, the NH4-containing compound is NH4Cl, NH4BF4, NH4HF2, (NH4)2CO3, NH4HCO3 or NH4F, and the F-containing compound is LiBF4, HF, HBF4, NH4BF4, NH4F, NH4HF2, CsF or CsBF4;

[0017] b. Add the compound CsNH4B8O obtained in step a in a molar ratio of 1:0.1-1. 12 The polycrystalline powder of F2 is mixed evenly with flux LiBF4, NH4BF4, NH4HF2, NH4F, CsNO3, H3BO3, B2O3, PbO or PbF2, and then placed into a Φ40 mm quartz tube. The quartz tube is evacuated to a vacuum degree of 1×10 -3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 300-500°C, kept warm for 24-168 hours, slowly cooled, and cut the quartz tube to obtain cesium ammonium fluoroborate nonlinear optical crystal;

[0018] Alternatively, the Cs-containing compound, the B-containing compound and the F-containing compound are uniformly mixed in a molar ratio of Cs:NH4:B:F=0.5-2:0.5-2:3-10:0.5-2, pre-fired at 100°C in a muffle furnace, and then the NH4-containing compound and flux LiBF4, NH4BF4, NH4HF2, NH4F, CsNO3, H3BO3, B2O3, PbO or PbF2 are added and mixed uniformly, and then placed in a Φ40mm quartz tube, and the quartz tube is evacuated to a vacuum degree of 1×10 -3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 300-500°C, kept warm for 24-168 hours, slowly cooled, and cut the quartz tube to obtain cesium ammonium fluoroborate nonlinear optical crystal;

[0019] The room temperature solution method for growing cesium ammonium fluoroborate nonlinear optical crystals is specifically performed in the following steps:

[0020] a. Mix the Cs-containing compound, the B-containing compound and the F-containing compound in a molar ratio of Cs:NH4:B:F=0.5-2:0.5-2:3-10:0.5-2, pre-sinter them at 100°C in a muffle furnace, then add the ammonium-containing compound and flux LiBF4, NH4BF4, NH4HF2, NH4F, CsNO3, H3BO3, B2O3, PbO or PbF2, mix them evenly, put them into a Φ40mm quartz tube, and evacuate the quartz tube to a vacuum degree of 1×10 -3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 300-500 ° C, kept warm for 24-168 hours, slowly cooled, cut the quartz tube, and the compound CsNH4B8O was obtained. 12 Polycrystalline powder of F2, wherein the Cs-containing compound is CsCl, CsOH, CsNO3, Cs2CO3, CsHCO3, CH3COOCs, CsF or CsBF4, the B-containing compound is H3BO3, HBO2 or B2O3, the NH4-containing compound is NH4Cl, NH4BF4, NH4HF2, (NH4)2CO3, NH4HCO3 or NH4F, and the F-containing compound is LiBF4, HF, HBF4, NH4BF4, NH4F, NH4HF2, CsF or CsBF4;

[0021] b. Place the polycrystalline powder obtained in step a into a clean glass or polytetrafluoroethylene container, add 20-100 mL of deionized water, and then ultrasonicate for 5-30 minutes to fully mix and dissolve it, and then add HF to adjust the pH value of the solution to 1-10;

[0022] c. Seal the container containing the solution in step b with weighing paper, place it in a static environment without shaking, pollution, or air convection, pierce the seal with a small hole to control the evaporation rate to 0.2-2 mL / day, and let it stand for 5-40 days; wait for the solution to grow crystal particles at the bottom of the container until the crystal particle size no longer changes significantly, and the growth is completed to obtain seed crystals;

[0023] d. Filter the remaining solution with qualitative filter paper to remove the crystals and other impurities in the solution, select a seed crystal of good quality, fix the seed crystal with a platinum wire, suspend it in the filtered solution, pierce the seal with a small hole to control the evaporation rate to 0.2-2 mL / day, and let it stand at room temperature for 10-40 days to obtain a cesium ammonium fluoroborate nonlinear optical crystal;

[0024] The hydrothermal method for growing cesium ammonium fluoroborate nonlinear optical crystals is specifically performed in the following steps:

[0025] a. Mix the raw materials containing Cs compound, NH4 compound, B compound and F compound with flux LiBF4, NH4BF4, NH4HF2, NH4F, CsNO3, H3BO3, B2O3, PbO or PbF2 in a molar ratio of Cs:NH4:B:F=0.5-2:0.5-2:3-10:0.5-2, and put them into a quartz tube of Φ40 mm. Evacuate the quartz tube to a vacuum degree of 1×10 -3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 300-500 ° C, kept warm for 24-168 hours, slowly cooled, cut the quartz tube, and the compound CsNH4B8O was obtained. 12 Polycrystalline powder of F2, wherein the Cs-containing compound is CsCl, CsOH, CsNO3, Cs2CO3, CsHCO3, CH3COOCs, CsF or CsBF4, the B-containing compound is H3BO3, HBO2 or B2O3, the NH4-containing compound is NH4Cl, NH4BF4, NH4HF2, (NH4)2CO3, NH4HCO3 or NH4F, and the F-containing compound is LiBF4, HF, HBF4, NH4BF4, NH4F, NH4HF2, CsF or CsBF4;

[0026] b. Compound CsNH4B8O obtained in step a 12 Dissolve the F2 polycrystalline powder sample in 5-30 mL of deionized water. Treat the partially dissolved mixture in an ultrasonic bath at 20-40°C for 5-30 minutes to thoroughly mix it. Transfer the resulting mixed solution into the inner liner of a clean, uncontaminated autoclave with a volume of 50-100 mL, and tighten the autoclave to seal it.

[0027] Or directly mix the raw materials such as Cs compound, NH4 compound, B compound, F compound and flux LiBF4, NH4BF4, CsNO3, H3BO3, B2O3, PbO or PbF2 in a molar ratio of Cs:NH4:B:F=0.5-2:0.5-2:3-10:0.5-2, transfer them into the lining of a clean, pollution-free high-temperature and high-pressure reactor with a volume of 100 mL, and tighten the reactor to seal;

[0028] c. Place the autoclave in step b in a constant temperature box, heat it to 200-500°C at a rate of 20-50°C / h, keep it at this temperature for 2-10 days, then cool it down to room temperature at a rate of 0.1-2°C / day, open the autoclave, and obtain a cesium ammonium fluoroborate nonlinear optical crystal.

[0029] The cesium ammonium fluoroborate nonlinear optical crystal is used in preparing harmonic light output of 1064nm fundamental frequency light output by Nd:YAG laser for frequency doubling, tripling, quadrupling, quintupleting or sextupleting.

[0030] The cesium ammonium fluoroborate nonlinear optical crystal is used in preparing deep ultraviolet frequency-doubled light output with a wavelength lower than 200 nm.

[0031] The compound cesium ammonium fluoroborate nonlinear optical crystal is used in preparing a frequency doubling generator, an up or down frequency converter or an optical parametric oscillator.

[0032] The preparation method of the cesium ammonium fluoroborate nonlinear optical crystal of the present invention is as follows: the cesium ammonium fluoroborate polycrystalline powder used in the preparation of the mixed solution can also be replaced by directly weighed raw materials, that is, a Cs-containing compound, an NH4-containing compound, a B-containing compound, and a F-containing compound are uniformly mixed in a molar ratio of Cs:NH4:B:F=0.5-2:0.5-2:3-10:0.5-2, wherein the Cs-containing compound is CsCl, CsOH, CsNO3, Cs2CO3, CsHCO3, CH3COOCs, CsF, or CsBF4, the B-containing compound is H3BO3, HBO2, or B2O3, the NH4-containing compound is NH4Cl, NH4BF4, NH4HF2, (NH4)2CO3, NH4HCO3, or NH4F, and the F-containing compound is LiBF4, HF, HBF4, NH4BF4, NH4F, NH4HF2, CsF, or CsBF.

[0033] The present invention discloses a method for preparing cesium ammonium fluoroborate nonlinear optical crystals. The container used during the preparation process is a quartz tube, an Erlenmeyer flask, a polytetrafluoroethylene beaker, a plastic beaker, or a hydrothermal autoclave lined with polytetrafluoroethylene or a stainless steel lined with a platinum sleeve. When the quartz tube is used as the container, vacuuming is required before sealing to prevent volatilization of the raw materials during the reaction and the resulting rupture of the quartz tube. When the Erlenmeyer flask, polytetrafluoroethylene beaker, or plastic beaker is used as the container, it must first be cleaned with acid, rinsed with deionized water, and air-dried.

[0034] In the preparation method of the cesium ammonium fluoroborate nonlinear optical crystal of the present invention, the resistance furnace used in the preparation process is a muffle furnace, a single crystal furnace or a drying box.

[0035] The method for preparing cesium ammonium fluoroborate nonlinear optical crystals of the present invention is used to obtain CsNH4B8O with a size of centimeters. 12 F2 nonlinear optical crystal, using a large size container and extending the crystal growth cycle, can obtain a corresponding large size nonlinear optical crystal CsNH4B8O 12 F2, the CsNH4B8O 12The F2 nonlinear optical crystal is easy to grow and is transparent without wrapping during growth. It has the advantages of low cost and easy to obtain large-size crystals with high optical quality.

[0036] The large-sized CsNH4B8O 12 F2 nonlinear optical crystal, according to the crystallographic data of the crystal, the crystal blank is oriented, the crystal is cut according to the required angle, thickness and cross-sectional size, and the light-transmitting surface of the crystal is polished, and it can be used as a nonlinear optical device. 12 F2 nonlinear optical crystal has the advantages of a wide light transmission band, stable physical and chemical properties, high mechanical hardness, not easy to break and deliquesce, and easy to cut, polish and preserve. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is the powder X-ray diffraction pattern of the present invention;

[0038] Figure 2 CsNH4B8O of the present invention 12 Structural diagram of F2 crystal;

[0039] Figure 3 The working principle diagram of the nonlinear optical device made by the present invention is that the device uses direct frequency doubling to output laser light of the desired wavelength. In order to output vacuum deep ultraviolet frequency-doubled light below 200nm and avoid light absorption in the atmospheric environment, the device is equipped with a vacuum system, which includes (1) a frequency-tunable laser with an output laser wavelength range of 400-2000nm, (2) a fully converging lens, (3) and (5) cesium ammonium fluoroborate nonlinear optical crystals, (4) and (6) filters, ω is the frequency of the incident light, and the frequency of the output light is equal to or twice the frequency of the incident light.

[0040] Figure 4 The working principle diagram of the nonlinear optical device made by the present invention is that the device uses the sum frequency method to output laser light of the required wavelength. In order to output vacuum deep ultraviolet sum frequency light below 200nm and avoid light absorption in the atmospheric environment, the device is equipped with a vacuum system, which includes (1) a frequency-tunable laser that can output laser wavelengths in the range of 300-2000nm, (2) a fully converging lens, (3), (5), and (7) cesium ammonium fluoroborate nonlinear optical crystals, (4), (6), and (8) filters, ω is the frequency of the incident light, and the frequency of the output light is equal to the frequency of the incident light, or twice the frequency of the incident light, or the sum of the frequencies of the two beams of incident light. DETAILED DESCRIPTION

[0041] The present invention is described in detail below with reference to the accompanying drawings and examples: The present invention is further described below with reference to the examples. It should be noted that the present invention is not limited to the examples given, and any improvements made on the basis of the present invention do not violate the spirit of the present invention. The raw materials or equipment used in the present invention, unless otherwise specified, are all commercially available.

[0042] Example 1

[0043] Preparation of compounds:

[0044] The chemical reaction formula is CsF+NH4F+4B2O3→CsNH4B8O 12 F2 Preparation of compound CsNH4B8O 12 F2:

[0045] CsF and B2O3 were weighed and mixed according to the chemical formula, placed in a muffle furnace and pre-calcined at 100°C, then NH4F was added and mixed evenly, and then placed in a Φ40mm quartz tube, and the quartz tube was evacuated to a vacuum degree of 1×10 - 3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 330 ° C, kept warm for 24 hours, and slowly cooled to obtain the compound CsNH4B8O 12 F2.

[0046] Example 2

[0047] Preparation of compounds:

[0048] According to the chemical reaction formula CsF+NH4HF2+4B2O3→CsNH4B8O 12 F2+HF↑Preparation of compound CsNH4B8O 12 F2:

[0049] CsF and B2O3 were weighed and mixed evenly according to the chemical formula, and then pre-calcined in a muffle furnace at 100°C. NH4HF2 was then added and mixed evenly. The mixture was then placed in a Φ40 mm quartz tube, and the tube was evacuated to a vacuum degree of 1×10 - 3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 330 ° C, kept warm for 24 hours, and slowly cooled to obtain the compound CsNH4B8O 12 F2.

[0050] Example 3

[0051] Preparation of compounds:

[0052] The chemical reaction formula is CsBF4+NH4F+4B2O3→CsNH4B8O 12F2+BF3↑ prepares compound CsNH4B8O 12 F2:

[0053] CsBF4 and B2O3 were weighed and mixed according to the chemical formula, placed in a muffle furnace and pre-calcined at 100°C, then NH4F was added and mixed evenly, and then placed in a Φ40mm quartz tube, and the quartz tube was evacuated to a vacuum degree of 1×10 - 3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 330 ° C, kept warm for 24 hours, and slowly cooled to obtain the compound CsNH4B8O 12 F2.

[0054] Example 4

[0055] Preparation of compounds:

[0056] According to the chemical reaction formula CsBF4+NH4HF2+4B2O3→CsNH4B8O 12 Preparation of compound CsNH4B8O by F2+BF3↑+HF↑ 12 F2:

[0057] CsBF4 and B2O3 were weighed and mixed evenly according to the chemical formula, and then pre-calcined in a muffle furnace at 100°C. NH4HF2 was then added and mixed evenly. The mixture was then placed in a Φ40 mm quartz tube, and the tube was evacuated to a vacuum degree of 1×10 -3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 300 ° C, kept warm for 24 hours, and slowly cooled to obtain the compound CsNH4B8O 12 F2.

[0058] Example 5

[0059] Preparation of compounds:

[0060] The chemical reaction formula is CsF+NH4BF4+4B2O3→CsNH4B8O 12 F2+BF3↑ prepares compound CsNH4B8O 12 F2:

[0061] CsF and B2O3 were weighed and mixed evenly according to the chemical formula, placed in a muffle furnace and pre-calcined at 100°C, then NH4BF4 was added and mixed evenly, and then placed in a Φ40mm quartz tube, and the quartz tube was evacuated to a vacuum degree of 1×10 - 3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 400 ° C, kept warm for 48 hours, and slowly cooled to obtain the compound CsNH4B8O 12 F2.

[0062] Example 6

[0063] Preparation of compounds:

[0064] According to the chemical reaction formula CsF+NH4BF4+8H3BO3→CsNH4B8O 12 Preparation of compound CsNH4B8O by F2+BF3↑+12H2O↑ 12 F2:

[0065] CsF and H3BO3 were weighed and mixed evenly according to the chemical formula, placed in a muffle furnace and pre-calcined at 100°C, and then NH4BF4 was added and mixed evenly, and then placed in a Φ40mm quartz tube, and the quartz tube was evacuated to a vacuum degree of 1×10 -3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 320 ° C, kept warm for 24 hours, and slowly cooled to obtain the compound CsNH4B8O 12 F2.

[0066] Example 7

[0067] Preparation of compounds:

[0068] According to the chemical reaction formula CsBF4+NH4BF4+8H3BO3→CsNH4B8O 12 Preparation of compound CsNH4B8O by F2+2BF3↑+12H2O↑ 12 F2:

[0069] CsBF4 and H3BO3 were weighed and mixed evenly according to the chemical formula, and then pre-calcined in a muffle furnace at 100°C. Then NH4BF4 was added and mixed evenly. The mixture was placed in a Φ40mm quartz tube, and the quartz tube was evacuated to a vacuum degree of 1×10 -3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 320 ° C, kept warm for 24 hours, and slowly cooled to obtain the compound CsNH4B8O 12 F2.

[0070] Example 8

[0071] Preparation of compounds:

[0072] According to the chemical reaction formula CsF+NH4BF4+8HBO2→CsNH4B8O 12 Preparation of compound CsNH4B8O by F2+BF3↑+4H2O↑ 12 F2:

[0073] CsF and HBO2 were weighed and mixed evenly according to the chemical formula, and then pre-calcined in a muffle furnace at 100°C. NH4BF4 was then added and mixed evenly. The mixture was then placed in a Φ40 mm quartz tube, and the quartz tube was evacuated to a vacuum degree of 1×10 - 3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 350 ° C, kept warm for 48 hours, and slowly cooled to obtain the compound CsNH4B8O 12 F2.

[0074] Example 9

[0075] Growth of CsNH4B8O by Vacuum High-Temperature Solution Method 12 F2 crystal:

[0076] The compound CsNH4B8O obtained in Example 1 was added in a molar ratio of 1:0.2. 12 The F2 polycrystalline powder was mixed evenly with the flux B2O3 and placed in a Φ40 mm quartz tube. The quartz tube was evacuated to a vacuum degree of 1×10 -3 Pa, vacuum-sealed with a flame gun, placed in a muffle furnace, raised to 400°C at a rate of 10°C / h, kept constant for 4 days, then dropped to 200°C at a rate of 0.5°C / h, and then dropped to 40°C at a rate of 1°C / h. The quartz tube was cut open to obtain CsNH4B8O with a size of 8 mm × 14 mm × 9 mm. 12 F2 nonlinear optical crystal.

[0077] Example 10

[0078] Growth of CsNH4B8O by Vacuum High-Temperature Solution Method 12 F2 crystal:

[0079] The compound CsNH4B8O obtained in Example 2 was added in a molar ratio of 1:0.2. 12 F2 polycrystalline powder was mixed evenly with flux NH4BF4, and then placed into a Φ40mm quartz tube. The quartz tube was evacuated to a vacuum degree of 1×10 -3 Pa, vacuum-sealed with a flame gun, placed in a muffle furnace, raised to 400°C at a rate of 10°C / h, kept constant for 7 days, then dropped to 200°C at a rate of 0.5°C / day, and then dropped to 40°C at a rate of 1°C / h. The quartz tube was cut open to obtain CsNH4B8O with a size of 9mm×13mm×12mm. 12 F2 nonlinear optical crystal.

[0080] Example 11

[0081] Growth of CsNH4B8O by Vacuum High-Temperature Solution Method 12 F2 crystal:

[0082] The compound CsNH4B8O obtained in Example 1 was added in a molar ratio of 1:0.2. 12 The F2 polycrystalline powder was mixed evenly with the flux H3BO3 and placed in a Φ40 mm quartz tube. The quartz tube was evacuated to a vacuum degree of 1×10 -3 Pa, vacuum-sealed with a flame gun, placed in a muffle furnace, heated to 400°C at a rate of 10°C / h, kept constant for 5 days, then cooled to 200°C at a rate of 0.5°C / day, and then cooled to 40°C at a rate of 1°C / h. The quartz tube was cut open to obtain CsNH4B8O with a size of 11mm×13mm×7mm. 12 F2 nonlinear optical crystal.

[0083] Example 12

[0084] Growth of CsNH4B8O by Vacuum High-Temperature Solution Method 12 F2 crystal:

[0085] The compound CsNH4B8O obtained in Example 3 was added in a molar ratio of 1:0.2. 12 F2 polycrystalline powder was mixed evenly with flux NH4F, and placed in a Φ40 mm quartz tube. The quartz tube was evacuated to a vacuum degree of 1×10 -3 Pa, vacuum-sealed with a flame gun, placed in a muffle furnace, raised to 420°C at a rate of 10°C / h, kept constant for 5 days, then cooled to 250°C at a rate of 0.5°C / day, and then to 30°C at a rate of 1°C / h. The quartz tube was cut open to obtain CsNH4B8O with a size of 9mm×12mm×14mm. 12 F2 nonlinear optical crystal.

[0086] Example 13

[0087] Growth of CsNH4B8O by Vacuum High-Temperature Solution Method 12 F2 crystal:

[0088] The compound CsNH4B8O obtained in Example 3 was added in a molar ratio of 1:0.2. 12 F2 polycrystalline powder and flux CsNO3 were mixed evenly and placed in a Φ40 mm quartz tube. The quartz tube was evacuated to a vacuum degree of 1×10 -3 Pa, vacuum-sealed with a flame gun, placed in a muffle furnace, heated to 430°C at a rate of 10°C / h, kept constant for 4 days, then cooled to 200°C at a rate of 0.5°C / day, and then cooled to 40°C at a rate of 1°C / h. The quartz tube was cut open to obtain CsNH4B8O with a size of 10 mm × 13 mm × 8 mm. 12 F2 nonlinear optical crystal.

[0089] Example 14

[0090] Growth of CsNH4B8O by Vacuum High-Temperature Solution Method 12 F2 crystal:

[0091] The compound CsNH4B8O obtained in Example 2 was added in a molar ratio of 1:0.2:0.1. 12 F2 polycrystalline powder was mixed evenly with flux NH4BF4 and LiBF4, and placed in a Φ40 mm quartz tube. The quartz tube was evacuated to a vacuum degree of 1×10 - 3 Pa, vacuum-sealed with a flame gun, placed in a muffle furnace, raised to 400°C at a rate of 10°C / h, kept constant for 7 days, then cooled to 200°C at a rate of 0.5°C / day, and then to 40°C at a rate of 1°C / h. The quartz tube was cut open to obtain CsNH4B8O with a size of 8mm×11mm×10mm. 12 F2 nonlinear optical crystal.

[0092] Example 15

[0093] Synthesis of CsNH4B8O by Room Temperature Solution Method 12 F2 nonlinear optical crystal:

[0094] a. The polycrystalline powder obtained in Example 1 was placed in a clean polytetrafluoroethylene container, 100 mL of deionized water was added, and ultrasonic treatment was performed for 30 minutes to fully mix and dissolve the powder. HF was then added to adjust the pH value of the solution to 2.

[0095] b. Seal the container containing the solution in step a with weighing paper, place it in a static environment without shaking, pollution, or air convection, pierce the seal with a small hole to control the evaporation rate to 1 mL / day, and let it stand for 10 days; wait for the solution to grow crystal particles at the bottom of the container until the crystal particle size no longer changes significantly, and the growth is completed to obtain seed crystals;

[0096] c. Filter the remaining solution with qualitative filter paper to remove the crystals and other impurities in the solution. Select a seed crystal of good quality, fix it with a platinum wire, and suspend it in the filtered solution. Poke a small hole in the seal to control the evaporation rate to 0.2 mL / day. Let it stand at room temperature for 30 days to obtain a cesium ammonium fluoroborate nonlinear optical crystal with a size of 8 mm × 11 mm × 13 mm.

[0097] Example 16

[0098] Synthesis of CsNH4B8O by Room Temperature Solution Method 12 F2 nonlinear optical crystal:

[0099] a. The polycrystalline powder obtained in Example 5 was placed in a clean polytetrafluoroethylene container, 100 mL of deionized water was added, and ultrasonic treatment was performed for 30 minutes to fully mix and dissolve the powder. HF was then added to adjust the pH value of the solution to 5.

[0100] b. Seal the container containing the solution in step a with weighing paper, place it in a static environment without shaking, pollution, or air convection, pierce the seal with a small hole to control the evaporation rate to 0.5 mL / day, and let it stand for 30 days; wait for the solution to grow crystal particles at the bottom of the container until the crystal particle size no longer changes significantly, and the growth is completed to obtain seed crystals;

[0101] c. Filter the remaining solution with qualitative filter paper to remove the crystals and other impurities in the solution. Select a seed crystal of good quality, fix it with a platinum wire, and suspend it in the filtered solution. Poke a small hole in the seal to control the evaporation rate to 0.5 mL / day. Let it stand at room temperature for 40 days to obtain a 10 mm × 13 mm × 12 mm cesium ammonium fluoroborate nonlinear optical crystal.

[0102] Example 17

[0103] Synthesis of CsNH4B8O by Room Temperature Solution Method 12 F2 nonlinear optical crystal:

[0104] a. Weigh the raw materials CsF, NH4F, and H3BO3 in a molar ratio of 1:1:8, then place them in a clean glass beaker, add 100 mL of deionized water, and then ultrasonicate for 30 minutes to completely mix and dissolve them. Then add HF to adjust the pH value of the solution to 1;

[0105] b. Seal the container containing the solution with weighing paper and place it in a static environment without shaking, pollution, or air convection. Poke small holes in the sealed weighing paper to control the evaporation rate to 2 mL / day. Let it stand for 5 days; wait for the solution to grow crystal particles at the bottom of the container until the crystal particle size no longer changes significantly, indicating that the growth is complete, to obtain seed crystals;

[0106] c. Filter the crystals and other impurities in the remaining solution with qualitative filter paper, select seed crystals of good quality, fix them with platinum wire, suspend them in the filtered solution, pierce the seal with small holes, control the evaporation rate to 0.5 mL / day, and let it stand at room temperature for 35 days to obtain CsNH4B8O with a size of 10 mm × 13 mm × 11 mm. 12 F2 nonlinear optical crystal.

[0107] Example 18

[0108] Synthesis of CsNH4B8O by Room Temperature Solution Method 12 F2 nonlinear optical crystal:

[0109] a. Weigh the raw materials CsF, NH4Cl, and H3BO3 in a molar ratio of 1:1:8 and place them in a clean glass container. Add 100 mL of deionized water and ultrasonicate for 30 minutes to fully mix and dissolve them. Then add HF to adjust the pH value of the solution to 4.

[0110] b. Seal the container containing the solution with weighing paper, place it in a static environment without shaking, pollution, or air convection, pierce the seal with a small hole to control the evaporation rate to 2 mL / day, and let it stand for 5 days; wait for the solution to grow crystal particles at the bottom of the container until the crystal particle size no longer changes significantly, and the growth is completed to obtain seed crystals;

[0111] c. Filter the crystals and other impurities in the remaining solution with qualitative filter paper, select seed crystals of good quality, fix them with platinum wire, suspend them in the filtered solution, pierce the seal with small holes, control the evaporation rate to 0.5 mL / day, and let it stand at room temperature for 30 days to obtain CsNH4B8O with a size of 9 mm × 11 mm × 12 mm. 12 F2 nonlinear optical crystal.

[0112] Example 19

[0113] Synthesis of CsNH4B8O by Room Temperature Solution Method 12 F2 nonlinear optical crystal:

[0114] a. Weigh the raw materials CsF, NH4HCO3, and H3BO3 in a molar ratio of 1:1:8 and place them in a clean glass container. Add 100 mL of deionized water and ultrasonicate for 10 minutes to fully mix and dissolve them. Then add HF to adjust the pH value of the solution to 2.

[0115] b. Seal the container containing the solution with weighing paper, place it in a static environment without shaking, pollution, or air convection, pierce the seal with a small hole to control the evaporation rate to 2 mL / day, and let it stand for 5 days; wait for the solution to grow crystal particles at the bottom of the container until the crystal particle size no longer changes significantly, and the growth is completed to obtain seed crystals;

[0116] c. Filter the crystals and other impurities in the remaining solution with qualitative filter paper, select seed crystals of good quality, fix them with platinum wire, suspend them in the filtered solution, pierce the seal with small holes, control the evaporation rate to 0.5 mL / day, and let it stand at room temperature for 30 days to obtain CsNH4B8O with a size of 11 mm × 10 mm × 13 mm. 12 F2 nonlinear optical crystal.

[0117] Example 20

[0118] Synthesis of CsNH4B8O by Room Temperature Solution Method 12 F2 nonlinear optical crystal:

[0119] a. CsNH4B8O obtained in Example 2 12 The polycrystalline powder of the F2 compound was placed in a clean polytetrafluoroethylene container, 100 mL of deionized water was added, and ultrasonic treatment was performed for 30 minutes to fully mix and dissolve it. HF was then added to adjust the pH value of the solution to 2.

[0120] b. Seal the container containing the solution with weighing paper, place it in a static environment without shaking, pollution, or air convection, pierce the seal with a small hole to control the evaporation rate to 2 mL / day, and let it stand for 5 days; wait for the solution to grow crystal particles at the bottom of the container until the crystal particle size no longer changes significantly, and the growth is completed to obtain seed crystals;

[0121] c. Filter the crystals and other impurities in the remaining solution with qualitative filter paper, select seed crystals of good quality, fix them with platinum wire, suspend them in the filtered solution, pierce the seal with small holes, control the evaporation rate to 0.5 mL / day, and let it stand at room temperature for 30 days to obtain CsNH4B8O with a size of 8 mm × 10 mm × 12 mm. 12 F2 nonlinear optical crystal.

[0122] Example 21

[0123] Hydrothermal synthesis of CsNH4B8O 12 F2 nonlinear optical crystal:

[0124] a. Compound CsNH4B8O obtained in Example 3 12 The F2 polycrystalline powder was dissolved in 10 mL of deionized water, and the incompletely dissolved mixture was treated in an ultrasonic bath at 40°C for 30 minutes to allow for thorough mixing.

[0125] b. Transfer the obtained mixed solution into the liner of a clean, pollution-free autoclave with a volume of 100 mL, and tighten and seal the autoclave;

[0126] c. Place the autoclave in a constant temperature box, heat the temperature to 220°C at a rate of 20°C / h, keep the temperature constant for 7 days, then cool it down to room temperature at a rate of 1°C / day, open the autoclave, and obtain CsNH4B8O with a size of 6mm×8mm×5mm. 12 F2 nonlinear optical crystal.

[0127] Example 22

[0128] Hydrothermal synthesis of CsNH4B8O 12 F2 nonlinear optical crystal:

[0129] a. Compound CsNH4B8O obtained in Example 6 12The F2 polycrystalline powder was dissolved in 10 mL of deionized water, and the incompletely dissolved mixture was treated in an ultrasonic bath at 40°C for 30 minutes to allow for thorough mixing.

[0130] b. Transfer the obtained mixed solution into the liner of a clean, pollution-free autoclave with a volume of 100 mL, and tighten and seal the autoclave;

[0131] c. Place the autoclave in a constant temperature box, heat the temperature to 220°C at a rate of 10°C / h, keep the temperature constant for 7 days, then cool it down to room temperature at a rate of 1°C / day, open the autoclave, and obtain CsNH4B8O with a size of 6mm×9mm×6mm. 12 F2 nonlinear optical crystal.

[0132] Example 23

[0133] Hydrothermal synthesis of CsNH4B8O 12 F2 nonlinear optical crystal:

[0134] a. Compound CsNH4B8O obtained in Example 8 12 The F2 polycrystalline powder was dissolved in 20 mL of deionized water, and the incompletely dissolved mixture was treated in an ultrasonic bath at 40°C for 30 minutes to allow for thorough mixing.

[0135] b. Transfer the obtained mixed solution into the liner of a clean, pollution-free autoclave with a volume of 100 mL, and tighten and seal the autoclave;

[0136] c. Place the autoclave in a constant temperature box, heat the temperature to 300°C at a rate of 10°C / h, keep the temperature constant for 10 days, then cool it down to room temperature at a rate of 1°C / day, open the autoclave, and obtain CsNH4B8O with a size of 12 mm × 10 mm × 11 mm. 12 F2 nonlinear optical crystal.

[0137] Example 24

[0138] Hydrothermal synthesis of CsNH4B8O 12 F2 nonlinear optical crystal:

[0139] a. Compound CsNH4B8O obtained in Example 1 12 The F2 polycrystalline powder was dissolved in 10 mL of deionized water, and the incompletely dissolved mixture was treated in an ultrasonic bath at 40°C for 30 minutes to allow for thorough mixing.

[0140] b. Transfer the obtained mixed solution into the liner of a clean, pollution-free 50 mL autoclave and seal the autoclave tightly;

[0141] c. Place the autoclave in a constant temperature box, heat the temperature to 240°C at a rate of 10°C / h, keep the temperature constant for 9 days, then cool it down to room temperature at a rate of 1°C / day, open the autoclave, and obtain CsNH4B8O with a size of 5mm×3mm×6mm. 12 F2 nonlinear optical crystal.

[0142] Example 25

[0143] Hydrothermal synthesis of CsNH4B8O 12 F2 nonlinear optical crystal:

[0144] a. Weigh the raw materials CsF, NH4F, and H3BO3 in a molar ratio of 1:1:8, dissolve them in 20 mL of deionized water, and treat the partially dissolved mixture in an ultrasonic bath at 40°C for 20 minutes to fully mix.

[0145] b. Transfer the obtained mixed solution into the liner of a clean, pollution-free autoclave with a volume of 100 mL, and tighten and seal the autoclave;

[0146] c. Place the autoclave in a constant temperature box, heat it to 220°C at a rate of 20°C / h, keep it constant for 7 days, then cool it down to room temperature at a rate of 1°C / day, open the autoclave, and obtain CsNH4B8O with a size of 9mm×8mm×6mm. 12 F2 nonlinear optical crystal.

[0147] Example 26

[0148] Hydrothermal synthesis of CsNH4B8O 12 F2 nonlinear optical crystal:

[0149] a. Weigh the raw materials CsF, NH4F, and B2O3 in a molar ratio of 1:1:8, mix them evenly with the flux NH4BF4 in a molar ratio of 1:0.2, transfer them into the liner of a clean, pollution-free high-temperature and high-pressure reactor with a volume of 100 mL, and tighten the reactor to seal it;

[0150] b. Place the autoclave in a constant temperature box, heat it to 400°C at a rate of 20°C / h, keep it at this temperature for 5 days, then cool it down to room temperature at a rate of 1°C / day, open the autoclave, and obtain CsNH4B8O with a size of 10 mm × 7 mm × 8 mm. 12 F2 nonlinear optical crystal.

[0151] Example 27

[0152] Hydrothermal synthesis of CsNH4B8O 12 F2 nonlinear optical crystal:

[0153] a. Weigh the raw materials CsF, NH4HF, and B2O3 in a molar ratio of 1:1:8, mix them evenly with the flux B2O3 in a molar ratio of 1:0.2, put them into the liner of a clean, pollution-free high-temperature and high-pressure reactor with a volume of 100 mL, and tighten the reactor to seal it;

[0154] b. Place the autoclave in a constant temperature box, heat it to 420°C at a rate of 20°C / h, keep it constant for 7 days, then cool it down to room temperature at a rate of 1°C / day, open the autoclave, and obtain CsNH4B8O with a size of 9 mm × 11 mm × 12 mm. 12 F2 nonlinear optical crystal.

[0155] Example 28

[0156] Hydrothermal synthesis of CsNH4B8O 12 F2 nonlinear optical crystal:

[0157] a. Weigh the raw materials CsF, NH4HF, and B2O3 in a molar ratio of 1:1:8, mix them evenly with the flux LiBF4 in a molar ratio of 1:0.2, and put them into the lining of a clean, pollution-free high-temperature and high-pressure reactor with a volume of 100 mL, and tighten the reactor to seal it;

[0158] b. Place the autoclave in a constant temperature box, heat it to 400°C at a rate of 20°C / h, keep it constant for 7 days, then cool it down to room temperature at a rate of 1°C / day, open the autoclave, and obtain CsNH4B8O with a size of 10 mm × 8 mm × 12 mm. 12 F2 nonlinear optical crystal.

[0159] Example 29

[0160] Any of the cesium ammonium fluoroborate nonlinear optical crystals obtained in Examples 9-28 is processed in a matching direction, and the attached Figure 3 As shown, it is placed at position 3. At room temperature, a Q-switched Nd:YAG laser is used as the light source. The incident wavelength is 1064 nm. The infrared beam with a wavelength of 1064 nm emitted by the Q-switched Nd:YAG laser 1 is incident on the cesium ammonium fluoroborate single crystal 3, generating green frequency-doubled light with a wavelength of 532 nm. The output intensity is about 2.5 times that of KDP under the same conditions.

[0161] Example 30

[0162] Any of the cesium ammonium fluoroborate nonlinear optical crystals obtained in Examples 9-28 is processed in a matching direction, and the attached Figure 3As shown, it is placed at position 5. At room temperature, a Q-switched Nd:YAG laser is used as the light source. The incident wavelength is 532nm. The green light beam with a wavelength of 532nm emitted by the Q-switched Nd:YAG laser 1 is incident on the cesium ammonium fluoroborate single crystal 3, generating a frequency-doubled light with a wavelength of 266nm. The output intensity is about 0.6 times that of BBO under the same conditions.

[0163] Example 31

[0164] Any of the cesium ammonium fluoroborate nonlinear optical crystals obtained in Examples 9-28 is processed in a matching direction, and the attached Figure 3 As shown, it is placed at position 5. At room temperature, a Q-switched Nd:YAG laser is used as the light source, and the incident wavelength is 355nm. The light beam with a wavelength of 355nm emitted by the Q-switched Nd:YAG laser 1 is incident on the cesium ammonium fluoroborate single crystal 5, generating a deep ultraviolet frequency-doubled light output with a wavelength of 177.3nm.

[0165] Example 32

[0166] Any of the cesium ammonium fluoroborate nonlinear optical crystals obtained in Examples 9-28 is processed in a matching direction, and the attached Figure 4 As shown, it is placed at positions 3 and 5. At room temperature, a Q-switched Nd:YAG laser is used as the light source, and the incident wavelength is 1064nm. The light beam with a wavelength of 1064nm emitted by the Q-switched Nd:YAG laser 1 is incident on the cesium ammonium fluoroborate single crystal 3, generating a deep ultraviolet and frequency light output with a wavelength of 355nm.

[0167] Example 33

[0168] Any of the cesium ammonium fluoroborate nonlinear optical crystals obtained in Examples 9-28 is processed in a matching direction, and the attached Figure 4 As shown, it is placed at positions 3 and 7. At room temperature, a Q-switched Nd:YAG laser is used as the light source, and the incident wavelength is 355nm. The light beam with a wavelength of 355nm emitted by the Q-switched Nd:YAG laser 1 is incident on the cesium ammonium fluoroborate single crystal 3, generating a deep ultraviolet and frequency light output with a wavelength of 177.3nm.

Claims

1. A compound cesium ammonium fluoroborate, characterized in that The chemical formula of this compound is CsNH4B8O 12 F2, with a molecular weight of 467.43, was prepared using a vacuum high-temperature solution method.

2. The method for preparing the compound cesium ammonium fluoroborate according to claim 1, wherein It is made by vacuum high temperature solution method, and the specific operation is carried out according to the following steps: The molar ratio of Cs:NH4:B:F is 0.5-2:0.5-2:3-10:0.5-2. The Cs-containing compound, the B-containing compound and the F-containing compound are first mixed uniformly, and pre-calcined at 100°C in a muffle furnace. Then, the NH4-containing compound is added, mixed uniformly, and then loaded into a Φ40mm quartz tube. The quartz tube is evacuated to a vacuum degree of 1×10 −3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 300-500 ° C, kept warm for 3-168 hours, and slowly cooled to obtain the compound CsNH4B8O 12 F2, wherein the Cs-containing compound is CsCl, CsOH, CsNO3, Cs2CO3, CsHCO3, CH3COOCs, CsF or CsBF4, the B-containing compound is H3BO3, HBO2 or B2O3, the NH4-containing compound is NH4Cl, NH4BF4, NH4HF2, (NH4)2CO3, NH4HCO3 or NH4F, and the F-containing compound is LiBF4, HF, HBF4, NH4BF4, NH4F, NH4HF2, CsF or CsBF4.

3. A cesium ammonium fluoroborate nonlinear optical crystal, characterized in that The chemical formula of this crystal is CsNH4B8O 12 F2, belongs to the trigonal system, and its space group is P 321, the unit cell parameters are a = b = 6.5858(4)±0.02 Å, c = 7.8163(6)±0.02 Å, α = β =90 o , γ = 120 o , Z = 1.

4. The method for preparing the cesium ammonium fluoroborate nonlinear optical crystal according to claim 3, characterized in that Crystals are prepared using vacuum high-temperature solution method, room-temperature solution method or hydrothermal method; The vacuum high-temperature solution method for growing cesium ammonium fluoroborate nonlinear optical crystals is carried out according to the following steps: a. In the molar ratio of Cs:NH4:B:F=0.5-2:0.5-2:3-10:0.5-2, the Cs-containing compound, the B-containing compound and the F-containing compound were first mixed uniformly, and pre-calcined at 100°C in a muffle furnace. Then, the NH4-containing compound was added, mixed uniformly, and then loaded into a Φ40mm quartz tube. The quartz tube was evacuated to a vacuum degree of 1×10 −3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 300-500 ° C, kept warm for 3-168 hours, and slowly cooled to obtain the compound CsNH4B8O 12 F2, wherein the Cs-containing compound is CsCl, CsOH, CsNO3, Cs2CO3, CsHCO3, CH3COOCs, CsF or CsBF4, the B-containing compound is H3BO3, HBO2 or B2O3, the NH4-containing compound is NH4Cl, NH4BF4, NH4HF2, (NH4)2CO3, NH4HCO3 or NH4F, and the F-containing compound is LiBF4, HF, HBF4, NH4BF4, NH4F, NH4HF2, CsF or CsBF4; b. Add the compound CsNH4B8O obtained in step a in a molar ratio of 1:0.1-1. 12 The polycrystalline powder of F2 is mixed evenly with flux LiBF4, NH4BF4, NH4HF2, NH4F, CsNO3, H3BO3, B2O3, PbO or PbF2, and then placed into a Φ40 mm quartz tube. The quartz tube is evacuated to a vacuum degree of 1×10 −3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 300-500°C, kept warm for 24-168 hours, slowly cooled, and cut the quartz tube to obtain cesium ammonium fluoroborate nonlinear optical crystal; Alternatively, the Cs-containing compound, the B-containing compound and the F-containing compound are uniformly mixed in a molar ratio of Cs:NH4:B:F=0.5-2:0.5-2:3-10:0.5-2, pre-fired at 100°C in a muffle furnace, and then the NH4-containing compound and flux LiBF4, NH4BF4, NH4HF2, NH4F, CsNO3, H3BO3, B2O3, PbO or PbF2 are added and mixed uniformly, and then placed in a Φ40mm quartz tube, and the quartz tube is evacuated to a vacuum degree of 1×10 −3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 300-500°C, kept warm for 24-168 hours, slowly cooled, and cut the quartz tube to obtain cesium ammonium fluoroborate nonlinear optical crystal; The room temperature solution method for growing cesium ammonium fluoroborate nonlinear optical crystals is specifically performed in the following steps: a. Mix the Cs-containing compound, the B-containing compound and the F-containing compound in a molar ratio of Cs:NH4:B:F=0.5-2:0.5-2:3-10:0.5-2, pre-sinter them at 100°C in a muffle furnace, then add the ammonium-containing compound and flux LiBF4, NH4BF4, NH4HF2, NH4F, CsNO3, H3BO3, B2O3, PbO or PbF2, mix them evenly, put them into a Φ40mm quartz tube, and evacuate the quartz tube to a vacuum degree of 1×10 −3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 300-500 ° C, kept warm for 24-168 hours, slowly cooled, cut the quartz tube, and the compound CsNH4B8O was obtained. 12 Polycrystalline powder of F2, wherein the Cs-containing compound is CsCl, CsOH, CsNO3, Cs2CO3, CsHCO3, CH3COOCs, CsF or CsBF4, the B-containing compound is H3BO3, HBO2 or B2O3, the NH4-containing compound is NH4Cl, NH4BF4, NH4HF2, (NH4)2CO3, NH4HCO3 or NH4F, and the F-containing compound is LiBF4, HF, HBF4, NH4BF4, NH4F, NH4HF2, CsF or CsBF4; b. Place the polycrystalline powder obtained in step a into a clean glass or polytetrafluoroethylene container, add 20-100 mL of deionized water, and then ultrasonicate for 5-30 minutes to fully mix and dissolve it, and then add HF to adjust the pH value of the solution to 1-10; c. Seal the container containing the solution in step b with weighing paper, place it in a static environment without shaking, pollution, or air convection, pierce the seal with a small hole to control the evaporation rate to 0.2-2 mL / day, and let it stand for 5-40 days; wait for the solution to grow crystal particles at the bottom of the container until the crystal particle size no longer changes significantly, and the growth is completed to obtain seed crystals; d. Filter the remaining solution with qualitative filter paper to remove the crystals and other impurities in the solution. Select a seed crystal of good quality, fix it with a platinum wire, and suspend it in the filtered solution. Seal the solution with a small hole to control the evaporation rate to 0.2-2 mL / day. Let it stand at room temperature for 10-40 days to obtain a cesium ammonium fluoroborate nonlinear optical crystal. The hydrothermal method for growing cesium ammonium fluoroborate nonlinear optical crystals is specifically performed in the following steps: a. Mix the raw materials containing Cs compound, NH4 compound, B compound and F compound with flux LiBF4, NH4BF4, NH4HF2, NH4F, CsNO3, H3BO3, B2O3, PbO or PbF2 in a molar ratio of Cs:NH4:B:F=0.5-2:0.5-2:3-10:0.5-2, and put them into a quartz tube of Φ40 mm. Evacuate the quartz tube to a vacuum degree of 1×10 −3 Pa, sealed under high temperature flame, placed in a muffle furnace, heated to 300-500 ° C, kept warm for 24-168 hours, slowly cooled, cut the quartz tube, and the compound CsNH4B8O was obtained. 12 Polycrystalline powder of F2, wherein the Cs-containing compound is CsCl, CsOH, CsNO3, Cs2CO3, CsHCO3, CH3COOCs, CsF or CsBF4, the B-containing compound is H3BO3, HBO2 or B2O3, the NH4-containing compound is NH4Cl, NH4BF4, NH4HF2, (NH4)2CO3, NH4HCO3 or NH4F, and the F-containing compound is LiBF4, HF, HBF4, NH4BF4, NH4F, NH4HF2, CsF or CsBF4; b. Compound CsNH4B8O obtained in step a 12 Dissolve the F2 polycrystalline powder sample in 5-30 mL of deionized water. Treat the partially dissolved mixture in an ultrasonic bath at 20-40°C for 5-30 minutes to thoroughly mix it. Transfer the resulting mixed solution into the inner liner of a clean, uncontaminated 50-100 mL autoclave, and seal the autoclave tightly. Or directly mix the raw materials containing Cs compound, NH4 compound, B compound, and F compound with flux LiBF4, NH4BF4, CsNO3, H3BO3, B2O3, PbO or PbF2 in a molar ratio of Cs:NH4:B:F=0.5-2:0.5-2:3-10:0.5-2, transfer them into the lining of a clean, pollution-free high-temperature and high-pressure reactor with a volume of 100 mL, and tighten the reactor to seal; c. Place the autoclave in step b in a constant temperature box, heat it to 200-500°C at a rate of 20-50°C / h, keep it at this temperature for 2-10 days, then cool it down to room temperature at a rate of 0.1-2°C / day, open the autoclave, and obtain a cesium ammonium fluoroborate nonlinear optical crystal.

5. Use of the cesium ammonium fluoroborate nonlinear optical crystal according to claim 3 in preparing harmonic light output of a 1064 nm fundamental frequency light output by an Nd:YAG laser for frequency doubling, tripling, quadrupling, quintupleting or sextupleting.

6. Use of the cesium ammonium fluoroborate nonlinear optical crystal according to claim 3 in preparing a deep ultraviolet frequency-doubled light output having a wavelength below 200 nm.

7. Use of the cesium ammonium fluoroborate nonlinear optical crystal according to claim 3 in the preparation of a frequency doubling generator, an up- or down-frequency converter, or an optical parametric oscillator.

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