Sodium fluosilicate deep ultraviolet nonlinear optical crystal as well as preparation method and application thereof

Abstract

The invention relates to a sodium lithium fluosilicate deep ultraviolet nonlinear optical crystal and a preparation method and application thereof, the chemical formula of the crystal is Na2SiF6 or Na6Si3F18, the crystal does not have a symmetric center and belongs to a trigonal system, the space group is P321, the cell parameters are # imgabs0 # imgabs1 #, alpha is equal to 90 degrees, beta is equal to 90 degrees, gamma is equal to 120 degrees, Z is equal to 3, the unit cell volume is # imgabs2 #, and the unit cell molecular weight is 1128.33274. The sodium fluosilicate deep ultraviolet nonlinear optical crystal with the size larger than 0.8 * 0.5 * 0.1 mm < 3 > can be obtained by adopting a hydrothermal mineralizer method and a hydrothermal self-crystallization method; the sodium fluosilicate deep ultraviolet nonlinear optical crystal with a relatively large size can be obtained by using a relatively high growth temperature, adopting a relatively large growth lining and prolonging the growth time. The crystal has the advantages of wide band gap, no absorption in visible and ultraviolet bands, high nonlinear optical effect, good mechanical property, difficulty in fragmentation and deliquescence, easiness in processing, storage and growth, low cost, environment-friendly raw materials and the like, and can be used for manufacturing deep ultraviolet nonlinear optical devices.

Description

Technical Field

[0001] The invention relates to a sodium fluorosilicate deep ultraviolet nonlinear optical crystal and a preparation method and application thereof, belonging to the field of deep ultraviolet nonlinear optical crystals. Background Art

[0002] As key materials for laser frequency doubling, multiple frequency doubling, sum frequency, difference frequency, optical parametric oscillation and optical parametric amplification, nonlinear optical crystals can broaden the laser wavelength range and open up new laser light sources. They are widely used in ultraviolet laser lithography, precision instrument processing, laser medical treatment, photochemistry and other fields. Commonly used oxygen-based ultraviolet and deep ultraviolet nonlinear optical crystals include: LiB3O5 (LBO), CsB3O5 (CBO), RbBe2BO3F2 (RBBF), KBe2BO3F2 (KBBF), SrB4O7 (SBO). KBBF crystal is currently the only practical nonlinear optical crystal that can output deep ultraviolet laser by direct frequency doubling. The ultraviolet cutoff edge of KBBF crystal is 147nm, and the shortest laser output can only achieve 149nm. The ultraviolet cutoff edge of SBO crystal is 120nm, and the shortest laser output can only achieve 121nm. This type of crystal exhibits a large band gap and excellent nonlinear optical properties. However, due to the absorption of metal-oxygen bonds, the band gap of this type of crystal cannot be further extended to the deep ultraviolet field. At present, no deep ultraviolet nonlinear optical crystals that can achieve a band below 120nm have been found, which greatly limits the development of deep ultraviolet all-solid-state lasers. Therefore, it is necessary to explore deep ultraviolet nonlinear optical crystals with wide band gap, high frequency doubling effect, easy growth and low cost. Summary of the invention

[0003] The purpose of the present invention is to provide a sodium fluorosilicate deep ultraviolet nonlinear optical crystal.

[0004] Another object of the present invention is to provide a method for preparing a sodium fluorosilicate deep ultraviolet nonlinear optical crystal.

[0005] Another object of the present invention is to provide the use of sodium fluorosilicate deep ultraviolet nonlinear optical crystal.

[0006] The sodium fluorosilicate deep ultraviolet nonlinear optical crystal of the present invention has a chemical formula of Na2SiF6 or Na6Si3F 18 The crystal has no symmetry center and belongs to the trigonal system. The space group is P321 and the unit cell parameters are α=90°,β=90°,γ=120°,Z=3, the unit cell volume is The single cell molecular weight is 1128.33274.

[0007] The preparation method of the sodium fluorosilicate deep ultraviolet nonlinear optical crystal is prepared by a hydrothermal mineralizer method and a hydrothermal self-crystallization method:

[0008] The hydrothermal mineralizer method for growing sodium fluorosilicate deep ultraviolet nonlinear optical crystals is specifically performed in the following steps:

[0009] a. According to the chemical formula Na6Si3F 18 The raw materials are weighed in air with a molar ratio of Na:Si:F=2:1:3, and then the raw materials and the co-solvent are weighed in a mass ratio of raw materials: mineralizer NaF: mineralizer Pr(NO3)3·6H2O: mineralizer HIO3: mineralizer HIO4.·2H2O=1:2-4:1-2:5-15:3-8, and then the raw materials and the co-solvent are weighed and put into a polytetrafluoroethylene liner, and then deionized water is added at a filling degree of 20%-80%, the liner is covered, and the liner is put into the 304 stainless steel shell of the hydrothermal kettle and tightened. Among them, the raw material source of Na is NaF or NaOH, the raw material of Si is SiO2, and the raw material source of F is NaF.

[0010] b. Place the hydrothermal reactor in step a into a step temperature-controlled blast drying oven, heat to 240°C at 2-5°C / min, keep warm for 80-120h, and then crystallize at a cooling rate of 0.5-30°C / h to obtain a sodium fluorosilicate deep ultraviolet nonlinear optical crystal.

[0011] The hydrothermal self-crystallization method for growing sodium fluorosilicate deep ultraviolet nonlinear optical crystals is specifically performed in the following steps:

[0012] a. Place Na2SiF6 compound powder and deionized water in a ratio of 0.02-1.5 g / mL into a polytetrafluoroethylene liner, cover the liner tightly, and then install it into the 304 stainless steel shell of the hydrothermal kettle and tighten it.

[0013] b. Place the hydrothermal reactor in step a into a program-controlled box furnace, heat to 240°C at 0.5-1.5°C / min, keep warm for 20-72h, and then crystallize at a cooling rate of 0.5-10°C / h to obtain sodium fluorosilicate deep ultraviolet nonlinear optical crystals.

[0014] The use of the sodium fluorosilicate deep ultraviolet nonlinear optical crystal is to convert the frequency of laser output of a laser.

[0015] The use of the sodium fluorosilicate deep ultraviolet nonlinear optical crystal is to generate harmonic light outputs of 2-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold and 8-fold frequencies for a laser beam with a wavelength of 1064nm.

[0016] The use of the sodium fluorosilicate deep ultraviolet nonlinear optical crystal is to generate harmonic light output with a wavelength lower than 120nm.

[0017] The use of the sodium fluorosilicate deep ultraviolet nonlinear optical crystal is to prepare harmonic generators, optical parametric oscillators and optical parametric amplifiers and optical waveguide devices in the ultraviolet region.

[0018] The use of the sodium fluorosilicate deep ultraviolet nonlinear optical crystal is to prepare optical parametric oscillation and optical parametric amplifier devices from infrared to deep ultraviolet regions.

[0019] The sodium fluorosilicate deep ultraviolet nonlinear optical crystal, preparation method and use of the present invention can obtain a crystal with a size greater than 0.8×0.5×0.1 mm by using a hydrothermal mineralizer method and a hydrothermal self-crystallization method. 3 Sodium fluorosilicate deep ultraviolet nonlinear optical crystals; by using higher growth temperature, larger growth liner, and extending growth time, sodium fluorosilicate deep ultraviolet nonlinear optical crystals of correspondingly larger size can be obtained.

[0020] According to the crystallographic data of the crystal, the crystal blank is oriented, cut according to the required angle, thickness and light-transmitting cross-sectional size, the light-transmitting surface of the crystal is polished, and processed into a spatial periodic grating structure using a femtosecond laser, which can then be used as a nonlinear optical device.

[0021] The application of the sodium fluorosilicate deep ultraviolet nonlinear optical crystal in the field of laser technology includes the preparation of ultraviolet and deep ultraviolet laser frequency conversion crystals, ultraviolet and deep ultraviolet lasers, ultraviolet and deep ultraviolet electro-optical devices, ultraviolet and deep ultraviolet communication devices, laser medical treatment, ultraviolet and deep ultraviolet lithography devices, and ultraviolet and deep ultraviolet micro-nano processing devices.

[0022] The sodium fluorosilicate deep ultraviolet nonlinear optical crystal and optical device of the present invention have a wide band gap (10.45 eV), a relatively high frequency doubling effect (3×SiO2), good mechanical properties, are not prone to breakage and deliquescence, are easy to process and store, are easy to grow, have low cost, use environmentally friendly raw materials, and are convenient for industrial large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The P321 phase Na6Si3F 18 Schematic diagram of the crystal structure, showing the projection of Na, Si, and F along the b direction.

[0024] Figure 2 The P321 phase Na6Si3F 18 Schematic diagram of the crystal structure, showing the projection of Na, Si, and F along the c direction.

[0025] Figure 3 The P321 phase Na6Si3F 18 Schematic diagram of X-ray diffraction of a single crystal after it is ground into powder.

[0026] Figure 4 The P321 phase Na6Si3F 18 Schematic diagram of energy bands calculated by crystal theory

[0027] Figure 5 This is a schematic diagram of the energy band calculated theoretically for the P3121 phase SiO2 crystal in the ICSD standard database.

[0028] Figure 6 The P321 phase Na6Si3F 18 Crystal working principle diagram, where 1 is the Q-switched Nd:YAG laser, 2 is the incident laser beam, 3 is the convex lens, 4 is the incident laser beam after focusing, and 5 is the processed P321 phase Na6Si3F 18 6 is a crystal, 6 is an outgoing laser beam generated by 5, 7 is a prism, and 8 is an outgoing laser beam after passing through the prism.

[0029] Figure 7 The P321 phase Na6Si3F 18 A spatial periodic structure of a crystal that achieves efficient laser output. This structure uses femtosecond laser direct writing to etch a spatial periodic grating structure on the crystal surface, which can achieve phase matching of the compensation period of the input laser and achieve efficient laser output. DETAILED DESCRIPTION

[0030] The technical content, achieved objectives and effects of the present invention are described in detail below in conjunction with the implementation and drawings.

[0031] Example 1

[0032] Exploring deep ultraviolet nonlinear optical crystals using anion and cation regulation theory:

[0033] The present invention combines the guidance of anion and cation regulation theory with experimental design to obtain a sodium fluorosilicate deep ultraviolet nonlinear optical crystal. The crystal has no absorption in the visible and ultraviolet bands, a theoretical band gap of 10.45 eV, a corresponding cutoff edge of 118.76 nm, and a strong nonlinear relationship effect (3×SiO2). It meets the conditions for being an ultraviolet and deep ultraviolet nonlinear optical crystal. The basic content of the anion and cation regulation theory includes the following two parts:

[0034] Cation SP strategy: Cations are selected from elements that only contain s and p orbital electrons or whose d orbital electrons are empty, preferably alkali metals or alkaline earth metals. Existing optical crystals often use transition metals and rare earth metals as cations: transition metals have electrons in their d orbitals, which often produce dd transitions between metal electrons or dp transitions between metal and oxygen electrons, resulting in strong absorption in the visible or ultraviolet light bands, affecting the application of crystals in the visible or ultraviolet light bands; rare earth metals have electrons in both f and d orbitals, which not only produce dd or ff orbital transitions, but also dp or fd orbital transitions, resulting in strong absorption in the visible or ultraviolet light bands, which also seriously limits the application of related crystals in the visible or ultraviolet light bands. The present invention selects elements containing only s and p orbital electrons or empty d orbital electrons. This type of cation contains only s orbital and p orbital electrons, and there is no electron distribution in the d orbital and f orbital. No dd orbital transition or ff orbital transition of electrons will occur, and no absorption will be generated in the visible light and ultraviolet light bands, so it has a lower ultraviolet cutoff edge.

[0035] Fully fluorinated anionic groups: The anionic groups are fully fluorinated groups that do not contain oxygen. Such anionic groups are more electronegative than those containing oxygen, have a larger band gap for electronic transition, and have a higher frequency doubling efficiency in nonlinear optics. Moreover, such anionic groups are usually isolated and can produce larger frequency doubling coefficients through polyhedral asymmetric distortion of the anionic groups.

[0036] Example 2

[0037] Growth of Sodium Fluorosilicate Deep Ultraviolet Nonlinear Optical Crystals by Hydrothermal Mineralizer Method:

[0038] a. Raw materials by mass ratio: mineralizer NaF: mineralizer Pr(NO3)3·6H2O: mineralizer HIO3: mineralizer HIO4.·2H2O = 1:2:2:5:3. Under air conditions, weigh the raw materials and mineralizer 0.26g SiO2, 0.52g NaF, 0.52g Pr(NO3)3·6H2O, 1.3g HIO3, 0.78g HIO4.2(H2O), mix them evenly, put them into a polytetrafluoroethylene liner with a capacity of 25ml, then add 5ml deionized water, cover the liner tightly, put it into the 304 stainless steel shell of the hydrothermal autoclave and tighten it;

[0039] b. Place the hydrothermal reactor in step a into a step temperature-controlled blast drying oven, heat to 240°C at 300°C / h, keep warm for 80h, and then crystallize at a cooling rate of 30°C / h to obtain 3.2×1.2×0.4mm 3 Sodium fluorosilicate deep ultraviolet nonlinear optical crystal.

[0040] Example 3

[0041] Growth of Sodium Fluorosilicate Deep Ultraviolet Nonlinear Optical Crystals by Hydrothermal Mineralizer Method:

[0042] a. Raw materials by mass ratio: mineralizer NaF: mineralizer Pr(NO3)3·6H2O: mineralizer HIO3: mineralizer HIO4.·2H2O = 1:4:2:15:8. Weigh the raw materials and mineralizer 0.26g SiO2, 1.04g NaF, 0.52g Pr(NO3)3·6H2O, 3.9g HIO3, 2.08g HIO4.2(H2O) under air conditions, mix them evenly, put them into a polytetrafluoroethylene liner with a capacity of 25ml, then add 15ml deionized water, cover the liner tightly, put it into the 304 stainless steel shell of the hydrothermal autoclave and tighten it;

[0043] b. Place the hydrothermal reactor in step a into a step temperature-controlled blast drying oven, heat to 240°C at 120°C / h, keep warm for 120h, and then crystallize at a cooling rate of 0.5°C / h to obtain 2.1×1.1×0.4mm 3 Sodium fluorosilicate deep ultraviolet nonlinear optical crystal.

[0044] Example 4

[0045] Growth of Sodium Fluorosilicate Deep Ultraviolet Nonlinear Optical Crystals by Hydrothermal Mineralizer Method:

[0046] a. Raw materials by mass ratio: mineralizer NaF: mineralizer Pr(NO3)3·6H2O: mineralizer HIO3: mineralizer HIO4.·2H2O = 1:3:2:11:4. Weigh the raw materials and mineralizer 0.26g SiO2, 0.78g NaF, 0.52g Pr(NO3)3·6H2O, 2.86g HIO3, 1.04g HIO4.2(H2O) under air conditions, mix them evenly, put them into a polytetrafluoroethylene liner with a capacity of 25ml, then add 5ml deionized water, cover the liner tightly, put it into the 304 stainless steel shell of the hydrothermal autoclave and tighten it;

[0047] b. Place the hydrothermal reactor in step a into a step temperature-controlled blast drying oven, heat to 240°C at 300°C / h, keep warm for 96h, and then crystallize at a cooling rate of 0.83°C / h to obtain 3.2×1.5×0.6mm 3 Sodium fluorosilicate deep ultraviolet nonlinear optical crystal.

[0048] Example 5

[0049] Growth of sodium fluorosilicate deep ultraviolet nonlinear optical crystals by hydrothermal self-crystallization method:

[0050] a. The Na2SiF6 compound powder and deionized water were mixed at a ratio of 0.02g / mL. Under air conditions, 0.2g of Na2SiF6 compound powder was weighed and loaded into a 25ml polytetrafluoroethylene liner, then 10ml of deionized water was added, the liner was tightly covered, and then the 304 stainless steel housing of the hydrothermal autoclave was tightened;

[0051] b. Place the hydrothermal reactor in step a into a program-controlled box furnace, heat to 240°C at 30°C / h, keep warm for 20h, and then crystallize at a cooling rate of 10°C / h to obtain 1.5×0.5×0.1mm 3 Sodium fluorosilicate deep ultraviolet nonlinear optical crystal.

[0052] Example 6

[0053] Growth of sodium fluorosilicate deep ultraviolet nonlinear optical crystals by hydrothermal self-crystallization method:

[0054] a. Mix Na2SiF6 compound powder with deionized water at a ratio of 1g / mL, weigh 10gNa2SiF6 compound powder under air conditions, load it into a 25ml polytetrafluoroethylene liner, then load 10ml of deionized water, cover the liner, and then load it into the 304 stainless steel shell of the hydrothermal autoclave and tighten it;

[0055] b. Place the hydrothermal reactor in step a into a program-controlled box furnace, heat to 240°C at 60°C / h, keep warm for 40h, and then crystallize at a cooling rate of 5°C / h to obtain 1.3×0.8×0.2mm 3 Sodium fluorosilicate deep ultraviolet nonlinear optical crystal.

[0056] Example 7

[0057] Growth of sodium fluorosilicate deep ultraviolet nonlinear optical crystals by hydrothermal self-crystallization method:

[0058] a. The Na2SiF6 compound powder and deionized water were mixed at a ratio of 0.07g / mL. Under air conditions, 0.7g of Na2SiF6 compound powder was weighed and loaded into a 25ml polytetrafluoroethylene liner, then 10ml of deionized water was added, the liner was tightly covered, and then the 304 stainless steel housing of the hydrothermal autoclave was tightened;

[0059] b. Place the hydrothermal reactor in step a into a program-controlled box furnace, heat to 240°C at 90°C / h, keep warm for 72h, and then crystallize at a cooling rate of 0.5°C / h to obtain 2.5×1.1×0.4mm 3 Sodium fluorosilicate deep ultraviolet nonlinear optical crystal.

[0060] Example 8

[0061] Growth of sodium fluorosilicate deep ultraviolet nonlinear optical crystals by hydrothermal self-crystallization method:

[0062] a. Mix Na2SiF6 compound powder with deionized water at a ratio of 0.05g / mL, under air conditions, weigh 5gNa2SiF6 compound powder, load it into a 150ml polytetrafluoroethylene liner, then load 100ml of deionized water, cover the liner, and then load it into the 304 stainless steel shell of the hydrothermal autoclave and tighten it;

[0063] b. Place the hydrothermal reactor in step a into a program-controlled box furnace, heat to 240°C at 70°C / h, keep warm for 60h, and then crystallize at a cooling rate of 1.5°C / h to obtain 3.1×1.2×0.4mm 3 Sodium fluorosilicate deep ultraviolet nonlinear optical crystal.

[0064] Example 9

[0065] Any one of the sodium fluorosilicate deep ultraviolet nonlinear optical crystals of implementation 2-8, the obtained chemical formula is Na6Si3F 18 The crystal has no symmetry center and belongs to the trigonal system. The space group is P321 and the unit cell parameters are α=90°,β=90°,γ=120°,Z=3, the unit cell volume is The structure of the crystal is shown in Figure 1 and Figure 2 , X-ray diffraction diagram is shown in Figure 3 .

[0066] Example 10

[0067] Accurate calculation of the energy band of sodium fluorosilicate deep ultraviolet nonlinear optical crystal:

[0068] Implement any of 2-8 Na6Si3F 18 The crystal structure data obtained from deep ultraviolet nonlinear optical crystals were calculated using the Castep module of Material studio software in reciprocal space and modulus conservation pseudopotential conditions using ultra-high precision PEB0 hybrid functionals. The calculation results are shown in Figure 4 , Na6Si3F 18 The theoretical band gap obtained by crystal calculation is 10.34eV (corresponding to the deep ultraviolet absorption edge of 118.76nm), which can be used to generate deep ultraviolet harmonic light output below 120nm; however, due to the discontinuity of the electron wave function selected for theoretical calculation, the theoretical band gap is smaller than the actual band gap, and the corresponding cutoff edge is larger. The standard crystal structure data file of the known P3121 phase SiO2 crystal is derived from the ICSD standard database. Using the same theoretical parameters, the calculated P3121 phase SiO2 crystal band gap is compared. The calculation results are shown in Figure 5The theoretical band gap value is 8.831eV (corresponding to the deep ultraviolet absorption edge of 140.30nm), while the actual band gap value is 9.00eV (corresponding to the deep ultraviolet absorption edge of 137.67nm). The calculation error is only 1.9%, and the calculation result is relatively accurate. 18 The band theory calculations are accurate.

[0069] Embodiment 11

[0070] Sodium fluorosilicate deep ultraviolet nonlinear optical crystal realizes spatial periodic grating structure with high efficiency output:

[0071] Using the Na6Si3F 18 Deep ultraviolet nonlinear optical crystals, according to Figure 7 As shown, after femtosecond laser direct writing, a periodic grating structure is engraved on the crystal surface, which can achieve compensatory periodic phase matching of the input laser and realize efficient laser output.

[0072] Example 12

[0073] Implement any of 2-8 Na6Si3F 18 Deep ultraviolet nonlinear optical crystals, according to Figure 6 As shown in the figure, it is placed at position 5. At room temperature, the crystal sample is irradiated with a 1064nm Q-switched Nd:YAG laser as the light source, and 532nm double frequency light output can be observed, and the output intensity is three times that of SiO2 of P3121 phase under the same conditions. According to its band gap, the crystal can be used to achieve laser output of 355nm, 266nm, 213nm, 177nm, 152nm and 133nm of Nd:YAG laser triple frequency.

[0074] Embodiment 13

[0075] Implement any of 2-8 Na6Si3F 18 Deep ultraviolet nonlinear optical crystals, according to Figure 6 As shown in the figure, it is placed at the position 5, and the fundamental frequency laser beam 2 with a frequency w is emitted by the laser 1, and the incident laser beam 4 is focused by the convex lens 3 and then incident on the Na6Si3F 18 The deep ultraviolet nonlinear optical crystal 5 outputs a frequency-doubled laser beam with an output frequency of 2W and the remaining fundamental frequency light 6. The frequency-doubled light and the fundamental frequency light are separated into output light 8 through a prism 7, thereby obtaining the required frequency-doubled laser.

[0076] Embodiment 14

[0077] Using the Na6Si3F 18Deep ultraviolet nonlinear optical crystals are used to prepare harmonic generators, frequency doubling generators, optical parametric oscillators, optical parametric amplifiers, optical waveguides, and frequency up and down converters from the infrared to the deep ultraviolet region.

[0078] Embodiment 15

[0079] Using the Na6Si3F 18 Deep ultraviolet nonlinear optical crystals are used to generate harmonic light output with a wavelength as short as less than 120nm.

[0080] In summary, the sodium fluorosilicate deep ultraviolet nonlinear optical crystal, preparation method and use of the present invention have the following advantages:

[0081] 1. Select elements containing only s and p orbital electrons or empty d orbital electrons as cations, and select anions with completely fluorinated groups to prepare sodium fluorosilicate deep ultraviolet nonlinear optical crystals with very large band gaps, no absorption in the visible and ultraviolet bands, and strong nonlinear relationship effects.

[0082] 2. Sodium fluorosilicate deep ultraviolet nonlinear optical crystals are colorless and transparent, not easy to deliquesce in the air, have good mechanical properties and are easy to process.

[0083] 3. Sodium fluorosilicate deep ultraviolet nonlinear optical crystal can generate 2-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold and 8-fold harmonic light output for the laser beam with a wavelength of 1064nm.

[0084] 4. Sodium fluorosilicate deep ultraviolet nonlinear optical crystals can generate harmonic light output with a wavelength below 120nm.

[0085] 5. Sodium fluorosilicate deep ultraviolet nonlinear optical crystals can be used in harmonic generators, frequency doubling generators, optical parametric oscillators, optical parametric amplifiers, optical waveguides, and frequency up and down converters from infrared to deep ultraviolet regions.

[0086] Finally, it should be noted that the above-described embodiments are only for illustrating the technical content, objectives and effects achieved by the present invention, and are not intended to limit the patent scope of the present invention. Any modification or equivalent transformation using the specification and drawings of the present invention, or direct or indirect application in related technical fields, does not depart from the spirit and scope of the technical solution of the present invention, and is equally included in the patent protection scope of the present invention.

Claims

1. A sodium fluorosilicate deep ultraviolet nonlinear optical crystal, characterized in that: The chemical formula of the sodium fluorosilicate deep ultraviolet nonlinear optical crystal is Na2SiF6 or Na6Si3F 18 The sodium fluorosilicate deep ultraviolet nonlinear optical crystal has no symmetry center, belongs to the trigonal crystal system, has a space group of P321, and a unit cell parameter of =8.8384(2) Å, b =8.8384(2) Å, c =5.0117(2) Å, α =90°, β =90°, γ =120°, Z =3, V=339.05(2) Å 3 The molecular weight of the single cell is 1128.33274.

2. The method for preparing a sodium fluorosilicate deep ultraviolet nonlinear optical crystal according to claim 1, wherein: It is prepared by hydrothermal mineralizer method and hydrothermal self-crystallization method; The hydrothermal mineralizer method for growing sodium fluorosilicate deep ultraviolet nonlinear optical crystals is specifically performed in the following steps: a. According to the chemical formula Na6Si3F 18 The molar ratio of Na:Si:F=2:1:3 is used to weigh the raw materials under air conditions, and then the mass ratio of raw materials: mineralizer NaF: mineralizer Pr(NO3)36H2O: mineralizer HIO3: mineralizer HIO4.2H2O =1:2-4:1-2:5-15:3-8 is used; the raw materials and the co-solvent are weighed and put into a polytetrafluoroethylene liner, and then deionized water is added at a filling degree of 20%-80%, the liner is covered, and the liner is put into the 304 stainless steel shell of the hydrothermal kettle and tightened. Among them, the raw material source of Na is NaF or NaOH, the raw material of Si is SiO2, and the raw material source of F is NaF; b. Place the hydrothermal reactor in step a into a step temperature-controlled blast drying oven, heat to 240°C at 120-300°C / h, keep warm for 80-120h, and then crystallize at a cooling rate of 0.5~30°C / h to obtain a sodium fluorosilicate deep ultraviolet nonlinear optical crystal; The hydrothermal self-crystallization method for growing sodium fluorosilicate deep ultraviolet nonlinear optical crystals is specifically performed in the following steps: a. The Na2SiF6 compound powder and deionized water were loaded into a polytetrafluoroethylene liner at a ratio of 0.02-1 g / mL, the liner was tightly capped, and then loaded into the 304 stainless steel shell of the hydrothermal autoclave and tightened; b. Place the hydrothermal reactor in step a into a program-controlled box furnace, heat to 240°C at 30-90°C / h, keep warm for 20-72h, and then crystallize at a cooling rate of 0.5~10°C / h to obtain sodium fluorosilicate deep ultraviolet nonlinear optical crystals.

3. The method for preparing the sodium fluorosilicate deep ultraviolet nonlinear optical crystal according to claim 2, characterized in that: The addition ratio of the Na2SiF6 compound powder to deionized water is 0.02-1 g / mL.

4. The method for preparing the sodium fluorosilicate deep ultraviolet nonlinear optical crystal according to claim 2, characterized in that: The maximum temperature during the dissolution was 240°C.

5. The method for preparing the sodium fluorosilicate deep ultraviolet nonlinear optical crystal according to claim 2, characterized in that: The Na2SiF6 compound powder and deionized water are dissolved and crystallized in the lining of polytetrafluoroethylene material.

6. The use of the sodium fluorosilicate deep ultraviolet nonlinear optical crystal according to claim 1, characterized in that: The sodium fluorosilicate deep ultraviolet nonlinear optical crystal is used for frequency conversion of laser output of a laser.

7. The use of the sodium fluorosilicate deep ultraviolet nonlinear optical crystal according to claim 1, characterized in that: The sodium fluorosilicate deep ultraviolet nonlinear optical crystal is used to generate harmonic light outputs of 2-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold and 8-fold frequencies for a laser beam with a wavelength of 1064nm.

8. The use of the sodium fluorosilicate deep ultraviolet nonlinear optical crystal according to claim 1, characterized in that: The sodium fluorosilicate deep ultraviolet nonlinear optical crystal is used to generate harmonic light output with the shortest wavelength below 120nm.

9. The use of the sodium fluorosilicate deep ultraviolet nonlinear optical crystal according to claim 1, characterized in that: The sodium fluorosilicate deep ultraviolet nonlinear optical crystal is used for preparing harmonic generators, frequency doubling generators, optical parametric oscillators, optical parametric amplifiers, optical waveguides, and frequency up and down converters in the infrared to deep ultraviolet regions.

10. Use of the sodium fluorosilicate deep ultraviolet nonlinear optical crystal and device as claimed in claim 9, characterized in that: The sodium fluorosilicate deep ultraviolet nonlinear optical crystal and device are used for preparing all-solid-state lasers from infrared to deep ultraviolet regions, laser medical treatment, or short-wave laser micro-nano lithography.

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