Fluorosulfonic acid melamine nonlinear optical crystal as well as growth method and application thereof

Abstract

The invention belongs to the technical field of optical crystal materials, and particularly relates to a melamine fluorosulfonate nonlinear optical crystal and a growth method and application thereof. The preparation method comprises the following steps: taking C3N6H6 and HSO3F as raw materials to prepare a melamine fluorosulfonate compound; and enabling the melamine fluorosulfonate crystal to directionally grow on the surface of the seed crystal by adopting a top seed crystal method to obtain the melamine fluorosulfonate nonlinear optical crystal. The spatial arrangement and the group density of a pi-conjugated [C3N6H8] group are effectively adjusted by using a fluorosulfonic acid group, and meanwhile, the compound has a relatively large frequency-doubled effect, a short ultraviolet cut-off edge and proper birefringence (0.064 at-1064nm), and can realize direct frequency-doubled output of short-wavelength ultraviolet laser. Compared with beta-barium borate, the birefringence of the material is reduced by about 44%, the walk-off effect is effectively avoided, and the material has application prospects in all-solid-state 266 nm ultraviolet lasers.

Description

Technical Field

[0001] This invention belongs to the field of optical crystal materials technology, specifically relating to a fluorosulfonic acid melamine nonlinear optical crystal, its growth method, and its applications. Background Technology

[0002] Due to their short wavelength and high photon energy, all-solid-state ultraviolet lasers have irreplaceable and wide-ranging applications in fields such as skin disease treatment, medical applications of biological tissue ablation, and commercial applications of precision photolithography, material surface modification, and ultraviolet detection.

[0003] In the realization of all-solid-state ultraviolet lasers, nonlinear optical crystals, as core components capable of altering laser wavelength, effectively extend the tunable range of the output laser wavelength and are key optical functional materials in the field of laser technology. Fourth harmonic or fourth-harmonic conversion using nonlinear optical crystals is an effective method to obtain high-power ultraviolet lasers shorter than 266nm. For example, using a nonlinear optical crystal, the 1064nm laser generated by the most widely used commercial Nd:YAG laser can be converted into 266nm ultraviolet light, and this nonlinear optical crystal is called a fourth-harmonic nonlinear optical crystal. In an all-solid-state 266nm ultraviolet laser, the fourth-harmonic nonlinear optical crystal is one of the core components of the laser, and its optical performance and quality directly affect the output power and beam quality of the ultraviolet laser.

[0004] Currently, commercially available fourth-harmonic nonlinear optical crystals mainly include barium β-borate, lithium cesium hexaborate, and potassium deuterium dihydrogen phosphate. Among them, barium β-borate is the most widely used commercial fourth-harmonic nonlinear optical crystal due to its wide transmission range, wide phase-matching interval, and large frequency doubling coefficient. However, barium β-borate has a relatively large birefringence Δn = 0.113@1064nm, which leads to severe walk-off effects, greatly reducing frequency conversion efficiency and limiting its development in high-power all-solid-state ultraviolet lasers. Summary of the Invention

[0005] To address the technical problem of excessively high birefringence in existing fourth-harmonic nonlinear optical crystals, leading to severe walk-off effects and reduced frequency conversion efficiency, this invention provides a melamine fluorosulfonic acid nonlinear optical crystal, its growth method, and its applications.

[0006] This invention uses C3N6H6 and HSO3F as raw materials and utilizes fluorosulfonic acid groups to effectively regulate π-conjugation of [C3N6H8]. 2+ The spatial arrangement and density of functional groups were used to synthesize (C3N6H8)(SO3F)2 crystals. In the resulting (C3N6H8)(SO3F)2 crystal structure, these anions and cations with high superconductivity are arranged according to non-centrosymmetry (space group...). PnaThe groups are arranged in a directional and orderly manner (21); this arrangement allows the microscopic nonlinear responses generated by each group to be superimposed in the same direction, thus exhibiting a strong frequency doubling effect on a macroscopic scale. Simultaneously, there is strong anisotropic π-conjugation [C3N6H8]. 2+ Groups and moderately anisotropic [SO3F] - The combination of tetrahedral groups, arranged optimally within an orthorhombic crystal framework, yields suitable birefringence. A suitable birefringence (0.064) is sufficient to compensate for the dispersion generated during the frequency transition from 532 nm to 266 nm, enabling critical phase matching. This, combined with phase matching and a large octave coefficient, ensures high energy conversion efficiency. Furthermore, the non-π-conjugated [SO3F]... - The introduction of the group, whose SF and S=O bonds have high bond energies, requires high-energy photons to excite, thus its intrinsic absorption edge is located in a very deep ultraviolet region. This effectively ensures that the entire crystal has a short ultraviolet cutoff edge, allowing efficient transmission of 266nm laser light.

[0007] The first objective of this invention is to provide a melamine fluorosulfonic acid nonlinear optical crystal, wherein the chemical formula of the melamine fluorosulfonic acid nonlinear optical crystal is (C3N6H8)(SO3F)2; the crystal structure belongs to the orthorhombic crystal system, and the space group is [missing information]. Pna 21, cell parameters are a =6.377Å, b =25.596Å, c =7.040Å, α = β = γ =90°, Z=4.

[0008] Preferably, the fluorosulfonic acid melamine nonlinear optical crystal structure is composed of (C3N6H8). 2+ Cations and (SO3F) - It is composed of anions arranged in a cross pattern; at the same time, there are electrostatic forces and hydrogen bond interactions in the nonlinear optical crystal structure of fluorosulfonic acid melamine, which form a three-dimensional network structure through ionic bonds and hydrogen bonds.

[0009] Preferably, the fluorosulfonic acid melamine nonlinear optical crystal has a birefringence of 0.064 at a wavelength of 1064 nm; this birefringence can compensate for the dispersion during the frequency conversion process from 532 nm to 266 nm, and achieve critical phase matching.

[0010] A second objective of this invention is to provide a method for growing a melamine fluorosulfonic acid nonlinear optical crystal, comprising the following steps: Using melamine and fluorosulfonic acid as raw materials, melamine and solvent are mixed evenly, fluorosulfonic acid is added and stirred evenly, and then allowed to stand for reaction to obtain fluorosulfonic acid melamine compound; the fluorosulfonic acid melamine compound is prepared into a saturated aqueous solution, and the top seed crystal method is used to make fluorosulfonic acid melamine crystals grow directionally on the surface of the seed crystal to obtain fluorosulfonic acid melamine nonlinear optical crystal.

[0011] It should be noted that during the synthesis of melamine fluorosulfonic acid, because melamine has low solubility, it is necessary to dissolve melamine in a solvent first before slowly adding fluorosulfonic acid, while avoiding vigorous stirring to prevent the fluorosulfonic acid from decomposing.

[0012] Preferably, the molar ratio of melamine to fluorosulfonic acid is 1:2 to 2.5. By adding an excess of fluorosulfonic acid, deviations from the stoichiometric ratio due to volatilization or decomposition of the fluorosulfonic acid during the preparation process are avoided.

[0013] Preferably, the total mass of the raw materials to the volume ratio of the solvent is 5g~6g:500mL.

[0014] Preferably, the solvent is deionized water.

[0015] Preferably, the temperature for static reaction is 30℃~48℃; and the time is 1 day~30 days.

[0016] Preferably, the specific method of the top seed crystal method is as follows: A saturated aqueous solution was prepared using melamine fluorosulfonic acid compound as a solute. The saturated aqueous solution was heated to 41°C and kept at a constant temperature for 6 to 10 hours. The seed crystal was immersed in the solution for preheating so that the seed crystal temperature reached the saturated solution temperature. Then the saturated solution was cooled to the saturation point so that the melamine fluorosulfonic acid crystal could grow directionally on the surface of the seed crystal. After the growth was completed, the crystal was lifted out of the liquid surface to obtain a melamine fluorosulfonic acid nonlinear optical crystal.

[0017] Preferably, during crystal growth, the crystal rotation speed is controlled at 3 rpm to 15 rpm, and the cooling rate is 0.1℃ / day to 1℃ / day.

[0018] A third objective of this invention is to provide the application of the above-mentioned fluorosulfonic acid melamine nonlinear optical crystal in the fabrication of nonlinear optical devices.

[0019] Preferably, the fluorosulfonic acid melamine nonlinear optical crystal is used as a fourth-harmonic nonlinear optical crystal in an all-solid-state 266nm ultraviolet laser.

[0020] The preferred and specific application methods are as follows: After the fluorosulfonic acid melamine nonlinear optical crystal is processed in a matching direction, it is placed in the optical path of an all-solid-state ultraviolet laser. An incident beam with an incident wavelength of 532nm is subjected to a fourth-harmonic conversion through the fluorosulfonic acid melamine nonlinear optical crystal. After filtering the fundamental frequency light, ultraviolet frequency-doubled light with a wavelength of 266nm is obtained.

[0021] Compared with the prior art, the present invention has the following technical effects: 1. This invention combines melamine, which has π-conjugated cations, with fluorosulfonic acid, which has anisotropic non-π-conjugated tetrahedral anions, and utilizes the fluorosulfonic acid groups to regulate π-conjugation [C3N6H8]. 2+ By optimizing the spatial arrangement and packing density of functional groups, a melamine fluorosulfonic acid nonlinear optical crystal was synthesized. A significant frequency doubling effect was achieved through the synergistic effect of π-conjugated and non-π-conjugated groups; its powder frequency doubling property is twice that of the commercially available crystal KDP, ensuring high conversion efficiency. Simultaneously, the melamine fluorosulfonic acid nonlinear optical crystal has an ultraviolet cutoff edge of less than 250 nm, meeting the transmittance requirements for deep ultraviolet laser output and potentially enabling direct frequency-doubled output of 266 nm ultraviolet laser.

[0022] 2. The fluorosulfonic acid melamine nonlinear optical crystal of the present invention has a suitable birefringence (0.064@1064nm), which is about 44% lower than the birefringence of commercial barium β-borate crystal (0.113@1064nm). This birefringence value can precisely meet the ultraviolet phase matching requirements. This characteristic greatly reduces the walk-off angle, allowing the fundamental frequency light and the frequency-doubled light to interact more fully in the crystal, thereby significantly improving the frequency conversion efficiency and output beam quality of the 266nm ultraviolet laser, laying the foundation for the realization of high-power all-solid-state ultraviolet lasers.

[0023] 3. The fluorosulfonic acid melamine nonlinear optical crystal of this invention has a single-crystal structure, is colorless and transparent, stable in air, has good thermal stability, is not synthesized using highly toxic raw materials, and does not exhibit layered growth characteristics. The fluorosulfonic acid melamine compound crystal can be used as a fourth-harmonic crystal to meet the requirements of ultraviolet all-solid-state laser output, and can be applied in fields such as large-capacity information storage, high-resolution spectral monitoring, and high-precision ultraviolet lithography. Attached Figure Description

[0024] Figure 1 The X-ray diffraction pattern of the fluorosulfonic acid melamine compound is shown.

[0025] Figure 2 This is a cell structure diagram of a fluorosulfonic acid melamine nonlinear optical crystal.

[0026] Figure 3 This is a typical schematic diagram of the nonlinear optical effects when the fluorosulfonic acid melamine nonlinear optical crystal is used as a frequency doubling crystal.

[0027] Figure labels: A1 - laser, A2 - incident beam, A3 - melamine fluorosulfonic acid nonlinear optical crystal, A4 - outgoing beam, A5 - filter. Detailed Implementation

[0028] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0029] Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0030] Example 1 A method for growing a fluorosulfonic acid melamine nonlinear optical crystal includes the following steps: Using melamine and fluorosulfonic acid as raw materials, 5.74 g of melamine was completely dissolved in deionized water, and then 5 L of fluorosulfonic acid with a concentration of 18.2051 mol / L was added. The mixture was stirred for 2 hours to obtain a mixed solution. The total mass of the raw materials and the volume ratio of deionized water were 6 g: 500 mL.

[0031] The mixed solution was placed in a beaker, the mouth of which was sealed with plastic wrap and micropores were punctured to control the evaporation rate. Then, it was transferred to a 40°C constant temperature oven and allowed to react for 5 days. Transparent crystals formed in the system. After filtration and drying, the fluorosulfonic acid melamine compound was obtained; the reaction formula is as follows: C3N6H6+2HSO3F=(C3N6H8)(SO3F)2.

[0032] The fluorosulfonic acid melamine compound was dissolved in deionized water to prepare a saturated aqueous solution at 40°C. The solution was then placed in a crystal growth furnace, heated to 41°C, and kept at a constant temperature for 6 hours.

[0033] A seed crystal was fixed at the lower end of a seed crystal rod in contact with the surface of the saturated solution and preheated for 15 minutes to bring the seed crystal temperature up to the saturated solution temperature. Then, the saturated solution was cooled to its saturation point of 40°C, initiating crystal growth on the seed crystal surface. A crystal rotation of 3 rpm was applied using a crystal growth controller, followed by slow cooling at a rate of 0.1°C / day. After cooling, the crystal was lifted from the liquid surface, yielding a melamine fluorosulfonic acid nonlinear optical crystal with dimensions of 3 mm × 3 mm × 3 mm.

[0034] Example 2 A method for growing a fluorosulfonic acid melamine nonlinear optical crystal includes the following steps: Using melamine and fluorosulfonic acid as raw materials, 4.59 g of melamine was completely dissolved in deionized water, and then 5 mL of fluorosulfonic acid with a concentration of 18.2051 mol / L was added. The mixture was stirred for 2 hours to obtain a mixed solution. The total mass of the raw materials and the volume ratio of deionized water were 5 g: 500 mL.

[0035] The mixed solution was placed in a beaker, the mouth of the beaker was sealed with plastic wrap and micropores were punctured to control the evaporation rate. Then, it was transferred to a constant temperature oven at 34°C and allowed to stand for 9 days to react. Transparent crystals were generated in the system. After filtration and drying, melamine fluorosulfonic acid compound was obtained.

[0036] The fluorosulfonic acid melamine compound was prepared into a saturated solution at 40°C, placed in a crystal growth furnace, heated to 41°C, and held at that temperature for 10 hours.

[0037] A seed crystal was fixed at the lower end of a seed crystal rod in contact with the surface of the saturated solution and preheated for 15 minutes to bring the seed crystal temperature up to the saturated solution temperature. Then, the saturated solution was cooled to its saturation point of 40°C, and crystal growth began on the seed crystal surface. A crystal rotation of 15 rpm was applied using a crystal growth controller, followed by slow cooling at a rate of 1°C / day. After cooling, the crystal was lifted from the liquid surface, yielding a melamine fluorosulfonic acid nonlinear optical crystal with dimensions of 3 mm × 3 mm × 3 mm.

[0038] Application Example 1 The fluorosulfonic acid melamine nonlinear optical crystal prepared in Example 1 was processed according to a matching direction, and then... Figure 3 As shown, the light source is placed at position A3. At room temperature, a Q-switched Nd:YAG laser is used as the light source with an incident wavelength of 532nm. The beam A2 with a wavelength of 532nm emitted by the Q-switched Nd:YAG laser A1 enters the fluorosulfonic acid melamine nonlinear optical crystal A3. The fundamental frequency light is eliminated by the filter A5, and ultraviolet frequency-doubled light with a wavelength of 266nm can be obtained.

[0039] Application Example 2 The fluorosulfonic acid melamine nonlinear optical crystal prepared in Example 2 was processed according to a matching direction. Figure 3 As shown, the light source is placed at position A3. At room temperature, a Q-switched Nd:YAG laser is used as the light source with an incident wavelength of 532nm. The beam A2 with a wavelength of 532nm emitted by the Q-switched Nd:YAG laser A1 enters the fluorosulfonic acid melamine nonlinear optical crystal A3. The fundamental frequency light is eliminated by the filter A5, and ultraviolet frequency-doubled light with a wavelength of 266nm can be obtained.

[0040] like Figure 1 As shown, the fluorosulfonic acid melamine compound prepared in Example 1 has a pure phase single crystal structure and is colorless and transparent.

[0041] like Figure 2 As shown, the crystal structure of the fluorosulfonic acid melamine nonlinear optical crystal belongs to the orthorhombic crystal system, and this crystal structure is composed of (C3N6H8). 2+ Cations and (SO3F) - It is composed of anions arranged in a cross pattern, and there are electrostatic forces and hydrogen bonds in the structure.

[0042] The optical properties of the fluorosulfonate melamine nonlinear optical crystal prepared in the embodiments of this invention were calculated using density functional theory. The powder frequency doubling property of the fluorosulfonate melamine nonlinear optical crystal is twice that of the commercial crystal KDP; the ultraviolet cutoff edge is less than 250 nm; it meets the transmittance requirements for deep ultraviolet laser output and is expected to achieve high-power output of 266 nm. Simultaneously, the fluorosulfonate melamine nonlinear optical crystal has a suitable birefringence (0.064@1064nm), which is about 44% lower than the birefringence of the commercial β-barium borate crystal (0.113@1064nm). This birefringence value precisely meets the ultraviolet phase matching requirements. This characteristic greatly reduces the walk-off angle, allowing the fundamental frequency light and the frequency-doubled light to interact more fully in the crystal, thereby significantly improving the frequency conversion efficiency and output beam quality of the 266 nm ultraviolet laser, laying the foundation for the realization of high-power all-solid-state ultraviolet lasers.

[0043] It should be noted that when numerical ranges are involved in this invention, it should be understood that the two endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described in this invention to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments, and all such changes and modifications fall within the scope of this invention.

[0044] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If these modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.

Claims

1. A melamine fluorosulfonic acid nonlinear optical crystal, characterized in that, The chemical formula of the fluorosulfonic acid melamine nonlinear optical crystal is (C3N6H8)(SO3F)2; the crystal structure belongs to the orthorhombic crystal system, and the space group is [missing information]. Pna 21, cell parameters are a =6.377Å, b =25.596Å, c =7.040Å, α = β = γ =90°, Z=4.

2. The fluorosulfonic acid melamine nonlinear optical crystal according to claim 1, characterized in that, The nonlinear optical crystal structure of melamine fluorosulfonic acid is composed of (C3N6H8). 2+ Cations and (SO3F) - Composed of anions arranged in a cross pattern.

3. A method for growing a melamine fluorosulfonic acid nonlinear optical crystal as described in claim 1 or 2, characterized in that, Includes the following steps: Using melamine and fluorosulfonic acid as raw materials, melamine and solvent are mixed evenly, fluorosulfonic acid is added and stirred evenly, and then allowed to stand to react to obtain fluorosulfonic acid melamine compound; A saturated aqueous solution of fluorosulfonic acid melamine compound was prepared, and the top seed crystal method was used to make fluorosulfonic acid melamine crystals grow directionally on the surface of the seed crystal to obtain fluorosulfonic acid melamine nonlinear optical crystals.

4. The method for growing a melamine fluorosulfonic acid nonlinear optical crystal according to claim 3, characterized in that, The molar ratio of melamine to fluorosulfonic acid is 1:2~2.

5.

5. The method for growing a fluorosulfonic acid melamine nonlinear optical crystal according to claim 3, characterized in that, The total mass of the raw materials to the volume ratio of the solvent is 5g~6g:500mL.

6. The method for growing a melamine fluorosulfonic acid nonlinear optical crystal according to claim 3, characterized in that, The solvent is water.

7. The method for growing a melamine fluorosulfonic acid nonlinear optical crystal according to claim 2, characterized in that, The static reaction temperature is 30℃~48℃, and the time is 1 day~30 days.

8. The application of a fluorosulfonic acid melamine nonlinear optical crystal in the fabrication of nonlinear optical devices, characterized in that, The fluorosulfonic acid melamine nonlinear optical crystal is the fluorosulfonic acid melamine nonlinear optical crystal according to claim 1 or 2.

9. The application of the fluorosulfonic acid melamine nonlinear optical crystal according to claim 8 in the fabrication of nonlinear optical devices, characterized in that, Fluorosulfonic acid melamine nonlinear optical crystal, as a fourth-harmonic nonlinear optical crystal, is used in an all-solid-state 266nm ultraviolet laser.

10. The application of the fluorosulfonic acid melamine nonlinear optical crystal according to claim 9 in the fabrication of nonlinear optical devices, characterized in that, The specific application methods are as follows: After the fluorosulfonic acid melamine nonlinear optical crystal is processed in a matching direction, it is placed in the optical path of an all-solid-state ultraviolet laser. An incident beam with an incident wavelength of 532nm is subjected to a fourth-harmonic conversion through the fluorosulfonic acid melamine nonlinear optical crystal. After filtering the fundamental frequency light, ultraviolet frequency-doubled light with a wavelength of 266nm is obtained.

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