Compound potassium sodium fluorosilicate nonlinear optical crystal, preparation method and use thereof

Abstract

The application discloses a wide-bandgap K2Na2Si2F 12 The application discloses a nonlinear optical crystal, a hydrothermal preparation method and application thereof. The crystal is a non-centrosymmetric orthorhombic crystal, a space group is Pna21 (No. 33), a cell parameter is a=18.5598(5)Å, b=5.4545(2)Å, c=9.7146(3)Å, α=90°, β=90°, γ=90°, Z=8, and a unit cell volume is V=983.45(5)Å 3 The application uses Na2SiF6 and KCl as raw materials, adopts a hydrofluoric acid-free hydrothermal cation replacement crystallization method to grow a single crystal, and has the advantages of green low-toxicity, low cost, high single crystal crystallization quality and large-scale preparation of large-size crystals. The experimental ultraviolet absorption edge of the crystal is lower than 200 nm, the theoretical band gap reaches 10.199 eV, and the deep ultraviolet light transmission window is extremely wide, so that the crystal can be used for preparing frequency conversion devices such as a frequency-doubling generator and an optical parametric oscillator.

Description

Technical Field

[0001] This invention belongs to the field of deep ultraviolet nonlinear optical materials and crystal growth technology, specifically relating to a compound sodium potassium fluorosilicate nonlinear optical crystal, its preparation method, and its uses. Background Technology

[0002] Nonlinear optical (NLO) crystals, as key materials for solid-state laser frequency doubling, multiple frequency doubling, sum frequency, difference frequency, optical parametric oscillation, and optical parametric amplification, can broaden the laser wavelength range and open up new laser sources. They have irreplaceable application value in many fields such as deep ultraviolet lithography, semiconductor wafer inspection, vacuum ultraviolet spectroscopy detection, infrared spectroscopy analysis, terahertz imaging, and photochemical research.

[0003] Optical frequency conversion devices have key applications in several important fields, including: frequency doubling devices, used in DUV lithography and semiconductors, outputting 266 nm and 213 nm deep ultraviolet light as light sources for wafer defect detection, mask inspection, and laser scribing; sum-frequency devices, used in vacuum ultraviolet high-resolution spectrometers, generating 193 nm ultraviolet laser light through the sum-frequency interaction of two laser beams; difference-frequency devices, used in infrared spectroscopy analysis, terahertz imaging, and non-destructive testing equipment, utilizing the difference-frequency effect to generate mid-infrared and terahertz radiation; and optical parametric devices, used in tunable spectral analysis, photochemical research, lidar, and multifunctional scientific laser systems, enabling continuously tunable laser wavelength output, etc. Furthermore, laser frequency conversion devices play an irreplaceable role in laser pulse shaping and timing control, laser beam quality optimization and mode purification, and laser frequency stabilization and wavelength locking.

[0004] The NLO crystal material for laser frequency conversion must be a non-centrosymmetric structure. Centrosymmetric crystals have zero second-order nonlinear coefficients, making frequency conversion impossible. The K2Na2Si2F crystal provided in this invention... 12 The space group is Pna21 (No. 33). It has a non-centrosymmetric structure and exhibits second-order nonlinear optical effects. Experimentally measured ultraviolet absorption edge is below 200 nm, corresponding to a band gap greater than 6.2 eV. The theoretically calculated band gap is 10.199 eV, corresponding to an ultraviolet cutoff edge of approximately 121.58 nm, making it a promising candidate material for deep ultraviolet nonlinear optics. Traditional fluorosilicic acid crystal preparation relies on hydrofluoric acid (HF) solution, which generally suffers from complex processes, incomplete reaction conversion, and difficulty in controlling single-crystal quality. Furthermore, HF solution is highly corrosive and toxic, posing high operational risks and posing a significant threat to the safety of experimental personnel, thus limiting the further development and device application of this crystal. Therefore, it is necessary to break through the traditional hydrofluoric acid etching and precipitation method and develop a clean, environmentally friendly, simple, and easily growable large-size, high-quality single-crystal preparation process to promote the practical application of this crystal in deep ultraviolet optical devices. Summary of the Invention

[0005] The purpose of this invention is to provide a compound, potassium sodium fluorosilicate, with the chemical formula K₂Na₂Si₂F. 12 It has a molecular weight of 408.323 and is prepared by hydrothermal cation substitution crystallization.

[0006] Another object of the present invention is to provide a potassium sodium fluorosilicate nonlinear optical crystal with the chemical formula K₂Na₂Si₂F₂. 12 The molecular weight is 408.323. This crystal has a non-centrosymmetric structure, belongs to the orthorhombic crystal system, space group Pna21 (No. 33), and has the following unit cell parameters: a = 18.5598(5) Å, b = 5.4545(2) Å, c = 9.7146(3) Å, α = 90°, β = 90°, γ = 90°, Z = 8, and the unit cell volume is V = 983.45(5) Å. 3 .

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned sodium potassium fluorosilicate nonlinear optical crystal.

[0008] Another object of the present invention is to provide the use of sodium potassium fluorosilicate nonlinear optical crystals in the field of optics.

[0009] The aforementioned potassium sodium fluorosilicate nonlinear optical crystal was prepared using a hydrothermal cation substitution crystallization method, the specific steps of which are as follows:

[0010] a. Mix Na2SiF6 and KCl in a molar ratio of 1:2 to 2:1, and weigh out a certain amount of each to ensure the full progress of the ion substitution reaction;

[0011] b. Place the weighed raw material into a 25ml polytetrafluoroethylene liner, add deionized water to fill the liner to 10%-80%, cover the liner, and put the polytetrafluoroethylene liner into a 304 stainless steel shell and tighten it.

[0012] c. Place the hydrothermal autoclave into a stepped temperature-controlled forced-air drying oven, and heat it to 120℃-240℃ at a rate of 2-5℃ / min, and keep it at that temperature for 72h-120h.

[0013] d. Cool the product at a rate of 30℃ / h to room temperature, then open the PTFE liner. Rinse the product with deionized water, and dry the washed crystal product in a drying oven to obtain K2Na2Si2F. 12 Crystal.

[0014] The K2Na2Si2F 12Applications of nonlinear optical crystals in the fabrication of laser frequency conversion devices, frequency multipliers, up or down frequency converters, or optical parametric oscillators; this device utilizes the second-order nonlinear optical effect of the crystal to achieve frequency conversion of the incident laser under the conditions of phase matching and polarization matching, and outputs the target deep ultraviolet laser.

[0015] The sodium potassium fluorosilicate nonlinear optical crystal used in this invention is a novel nonlinear optical crystal that exhibits a large theoretical band gap and can be used as a class of deep ultraviolet nonlinear optical crystals with potential applications.

[0016] This invention breaks through the traditional hydrofluoric acid etching and precipitation method, and innovatively develops a hydrothermal cation substitution crystallization method to prepare sodium potassium fluorosilicate nonlinear optical crystals. This synthesis method is clean, environmentally friendly, simple to operate, and produces high-quality, large-sized crystals. It enables low-cost, large-scale synthesis of large-size, high-quality single crystals, providing a suitable material for deep-ultraviolet nonlinear optical devices. Attached Figure Description

[0017] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0018] Figure 1 The Pna21 phase K2Na2Si2F grown by the hydrothermal cation substitution crystallization method of this invention 12 Schematic diagram of a single crystal specimen;

[0019] Figure 2 The present invention is a Pna21 phase K2Na2Si2F 12 Schematic diagram of a crystal unit cell structure;

[0020] Figure 3 The present invention is a Pna21 phase K2Na2Si2F 12 Schematic diagram of X-ray diffraction after single crystal is ground into powder;

[0021] Figure 4 The present invention is a Pna21 phase K2Na2Si2F 12 Ultraviolet-visible-near-infrared transmission spectrum of the crystal;

[0022] Figure 5 The present invention is a Pna21 phase K2Na2Si2F 12 Fourier transform infrared spectrum of the crystal;

[0023] Figure 6 The present invention is a Pna21 phase K2Na2Si2F 12 Raman spectrum of the crystal;

[0024] Figure 7 The present invention is a Pna21 phase K2Na2Si2F 12Theoretical calculations of the band gap of the crystal; Detailed Implementation

[0025] The technical content, objectives, and effects of this invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0026] Example 1

[0027] Hydrothermal cation substitution crystallization method for growing sodium fluorosilicate crystals:

[0028] a. Weigh out 0.940g Na2SiF6 and 0.740g KCl in a molar ratio of 1:2;

[0029] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then fill it with 5ml of deionized water to a 20% filling degree, seal the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal reactor and tighten it.

[0030] c. Place the hydrothermal autoclave into a stepped temperature-controlled forced-air drying oven, heat it to 240℃ at 4℃ / min, and keep it at that temperature for 72 hours;

[0031] d. Cool the product at a rate of 30℃ / h to room temperature, then open the polytetrafluoroethylene liner, rinse the product with deionized water, and dry the cleaned crystal product in a drying oven to obtain sodium potassium fluorosilicate crystals.

[0032] Example 2

[0033] Hydrothermal cation substitution crystallization method for growing sodium fluorosilicate crystals:

[0034] a. Weigh out 0.940g Na2SiF6 and 0.740g KCl in a molar ratio of 1:2;

[0035] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then fill it with 10ml of deionized water to 40% capacity, seal the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal reactor and tighten it.

[0036] c. Place the hydrothermal autoclave into a stepped temperature-controlled forced-air drying oven, heat it to 240℃ at 4℃ / min, and keep it at that temperature for 72 hours;

[0037] d. Cool the product at a rate of 30℃ / h to room temperature, then open the polytetrafluoroethylene liner, rinse the product with deionized water, and dry the cleaned crystal product in a drying oven to obtain sodium potassium fluorosilicate crystals.

[0038] Example 3

[0039] Hydrothermal cation substitution crystallization method for growing sodium fluorosilicate crystals:

[0040] a. Weigh out 0.940g Na2SiF6 and 0.740g KCl in a molar ratio of 1:2;

[0041] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then fill it with 15ml of deionized water to 60% capacity, seal the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal reactor and tighten it.

[0042] c. Place the hydrothermal autoclave into a stepped temperature-controlled forced-air drying oven, heat it to 240℃ at 4℃ / min, and keep it at that temperature for 72 hours;

[0043] d. Cool the product at a rate of 30℃ / h to room temperature, then open the polytetrafluoroethylene liner, rinse the product with deionized water, and dry the cleaned crystal product in a drying oven to obtain sodium potassium fluorosilicate crystals.

[0044] Example 4

[0045] Hydrothermal cation substitution crystallization method for growing sodium fluorosilicate crystals:

[0046] a. Weigh out 0.940g Na2SiF6 and 0.740g KCl in a molar ratio of 1:2;

[0047] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then fill it with 20ml of deionized water to 80% capacity, seal the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal reactor and tighten it.

[0048] c. Place the hydrothermal autoclave into a stepped temperature-controlled forced-air drying oven, heat it to 240℃ at 4℃ / min, and keep it at that temperature for 72 hours;

[0049] d. Cool the product at a rate of 30℃ / h to room temperature, then open the polytetrafluoroethylene liner, rinse the product with deionized water, and dry the cleaned crystal product in a drying oven to obtain sodium potassium fluorosilicate crystals.

[0050] Example 5

[0051] Hydrothermal cation substitution crystallization method for growing sodium fluorosilicate crystals:

[0052] a. Weigh out 1.880g Na2SiF6 and 0.370g KCl at a molar ratio of 2:1;

[0053] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then fill it with 5ml of deionized water to a 20% filling degree, seal the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal reactor and tighten it.

[0054] c. Place the hydrothermal autoclave into a stepped temperature-controlled forced-air drying oven, heat it to 240℃ at 5℃ / min, and keep it at that temperature for 72 hours;

[0055] d. Cool the product at a rate of 30℃ / h to room temperature, then open the polytetrafluoroethylene liner, rinse the product with deionized water, and dry the cleaned crystal product in a drying oven to obtain sodium potassium fluorosilicate crystals.

[0056] Example 6

[0057] Hydrothermal cation substitution crystallization method for growing sodium fluorosilicate crystals:

[0058] a. Weigh out 0.940g Na2SiF6 and 0.370g KCl in a molar ratio of 1:1;

[0059] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then fill it with 10ml of deionized water to 40% capacity, seal the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal reactor and tighten it.

[0060] c. Place the hydrothermal autoclave into a stepped temperature-controlled forced-air drying oven, heat it to 240℃ at 5℃ / min, and keep it at that temperature for 72 hours;

[0061] d. Cool the product at a rate of 30℃ / h to room temperature, then open the polytetrafluoroethylene liner, rinse the product with deionized water, and dry the cleaned crystal product in a drying oven to obtain sodium potassium fluorosilicate crystals.

[0062] Example 7

[0063] Hydrothermal cation substitution crystallization method for growing sodium fluorosilicate crystals:

[0064] a. Weigh out 0.940g Na2SiF6 and 0.370g KCl in a molar ratio of 1:1;

[0065] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then fill it with 15ml of deionized water to 60% capacity, seal the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal reactor and tighten it.

[0066] c. Place the hydrothermal autoclave into a stepped temperature-controlled forced-air drying oven, heat it to 240℃ at 5℃ / min, and keep it at that temperature for 72 hours;

[0067] d. Cool the product at a rate of 30℃ / h to room temperature, then open the polytetrafluoroethylene liner, rinse the product with deionized water, and dry the cleaned crystal product in a drying oven to obtain sodium potassium fluorosilicate crystals.

[0068] Example 8

[0069] Hydrothermal cation substitution crystallization method for growing sodium fluorosilicate crystals:

[0070] a. Weigh out 0.940g Na2SiF6 and 0.370g KCl in a molar ratio of 1:1;

[0071] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then fill it with 20ml of deionized water to 80% capacity, seal the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal reactor and tighten it.

[0072] c. Place the hydrothermal autoclave into a stepped temperature-controlled forced-air drying oven, heat it to 240℃ at 5℃ / min, and keep it at that temperature for 72 hours;

[0073] d. Cool the product at a rate of 30℃ / h to room temperature, then open the polytetrafluoroethylene liner, rinse the product with deionized water, and dry the cleaned crystal product in a drying oven to obtain sodium potassium fluorosilicate crystals.

[0074] Single-crystal X-ray diffraction was performed on the crystal samples prepared in Examples 1-8. The single crystals were treated with quenching and collected at 150(2) K. The testing instrument was a Bruker D8 VENTURE dual-wavelength (Mo / Cu) three-circle diffractometer equipped with a micro-focal sealed X-ray tube, a mirror monochromator, and a Bruker PHOTON III detector. The diffractometer was equipped with an Oxford Cryostream 800 cryogenic instrument and used Mo Kα radiation (λ = 0.71073 Å). All data were integrated and restored using the SAINT program and corrected for multi-scan absorption using the SADABS program. The structure was solved directly using the SHELXT program and based on the F-scan using the SHELXL-2019 / 2 program. 2 Full-matrix least squares refinement was performed, and disordered structural fragments were refined using bond length constraints and displacement parameter constraints. The crystallographic data of this invention has been submitted to the Cambridge Crystallographic Data Centre (CCDC), CCDC number: 2551898, and includes supplemental crystallographic data for this invention. This data is freely available from the Cambridge Crystallographic Data Centre at www.ccdc.cam.ac.uk / structures. A schematic diagram of the unit cell structure of the crystal obtained through the crystal structure is shown below. Figure 2 As shown, a schematic diagram of theoretical X-ray diffraction (XRD) is as follows: Figure 3 As shown in the figure. The structural data of the tested crystals are shown in Table 1.

[0075] Table 1 Nonlinear Optics K2Na2Si2F 12 Crystal structure data of crystals

[0076]

[0077] Test case

[0078] Test Example 1

[0079] An unpolished piece of material, approximately 4.5 × 1 × 0.5 mm in size, was prepared as shown in Examples 1-8. 3 The crystal was subjected to transmission spectroscopy testing, and the test results are as follows: Figure 4 It can be seen that the ultraviolet cutoff edge of the test crystal is below 200nm, indicating that it has deep ultraviolet transmission capability and meets the requirements of deep ultraviolet nonlinear optical crystals.

[0080] Test Example 2

[0081] The band gaps of the crystals obtained in Examples 1-8 were evaluated through theoretical calculations, and the calculation results are as follows: Figure 7 As shown, the theoretical band gap of this crystal can reach 10.199 eV, corresponding to an ultraviolet cutoff edge of about 121.58 nm, indicating that the crystal has the ability to output deep ultraviolet second harmonics.

[0082] Test Example 3

[0083] The crystals prepared in Examples 1-8 were tested for the magnitude of the frequency doubling effect using the Kurtz-Perry method. The test was performed using a Q-switched Nd:YAG laser with an input wavelength of 1064 nm. The crystal samples obtained in Examples 1-8 showed significantly weaker green light.

[0084] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A potassium sodium fluorosilicate nonlinear optical crystal, characterized in that, The chemical formula is K2Na2Si2F 12 It has a non-centrosymmetric structure, belongs to the orthorhombic crystal system, space group Pna21 (No. 33), and cell parameters a=18.5598(5)Å, b=5.4545(2)Å, c=9.7146(3)Å, α=90°, β=90°, γ=90°, Z=8, and unit cell volume V=983.45(5)Å. 3 .

2. The method for preparing the potassium sodium fluorosilicate nonlinear optical crystal as described in claim 1, characterized in that, The K2Na2Si2F 12 The crystals were grown using a hydrothermal cation substitution method. Hydrothermal cation substitution method for growing K2Na2Si2F 12 Crystals, including the following steps: a. Mix Na2SiF6 and KCl in a molar ratio of 1:2 to 2:1, and weigh out a certain amount of each to ensure the full progress of the ion substitution reaction; b. Weigh the raw material and put it into the polytetrafluoroethylene liner. Then add deionized water to fill the liner to 10%-80% capacity. Cover the liner and put the polytetrafluoroethylene liner into the 304 stainless steel shell and tighten it. c. Place the hydrothermal autoclave into a stepped temperature-controlled forced-air drying oven, and heat it to 120℃-240℃ at a rate of 2-5℃ / min, and keep it at that temperature for 72 h~120 h. d. Cool the product at a rate of 30℃ / h to room temperature, then open the PTFE liner. Rinse the product with deionized water, and dry the washed crystal product in a drying oven to obtain K2Na2Si2F. 12 Crystal.

3. The preparation method according to claim 2, characterized in that, The molar ratio of Na2SiF6 to KCl in step a is 1:2 to 2:1, the filling degree in step b is 10%-80%, the heating rate in step c is 2-5℃ / min, the maximum reaction temperature is 240℃, and the holding time is 72h to 120h.

4. The potassium sodium fluorosilicate nonlinear optical crystal as described in claim 1, characterized in that, The crystal has a non-centrosymmetric structure, with an experimental absorption edge below 200 nm and a corresponding band gap greater than 6.2 eV.

5. The application of the potassium sodium fluorosilicate nonlinear optical crystal as described in claim 1 in the preparation of laser frequency conversion devices, frequency multipliers, up or down frequency converters, and optical parametric oscillators.

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