Guanidine nitrate nonlinear optical crystal as well as preparation method and application thereof

Abstract

The invention provides a guanidine nitrate nonlinear optical crystal and a preparation method and application thereof, and belongs to the technical field of crystal materials and the technical field of optics. The chemical formula of the guanidine nitrate nonlinear optical crystal is C (NH2) 3NO3, the guanidine nitrate nonlinear optical crystal belongs to a monoclinic system, the space group is Cm, and the cell parameters are as follows: a is equal to 12.69 + / -0.02, b is equal to 7.27 + / -0.02, c is equal to 3.63 + / -0.02, alpha is equal to 90 degrees, beta is equal to 120.85 + / -0.02 degrees, gamma is equal to 90 degrees, and Z is equal to 2.

Description

Technical Field

[0001] The present disclosure relates to the technical fields of crystal materials and optical technologies, and particularly relates to a guanidine nitrate nonlinear optical crystal, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of the modern optoelectronic industry, nonlinear optical materials, as the core material basis of optoelectronic technologies, exhibit irreplaceable important values in fields such as laser frequency doubling, electro-optic modulation, optical storage, optical limiting, and optical switching. Particularly worthy of attention is the research breakthrough of nonlinear optical materials in the ultraviolet solar blind region (210 - 280 nm). By realizing the extension of the output wavelength of solid-state lasers to the ultraviolet solar blind band, such materials provide a key solution for breaking through the technical bottlenecks of traditional optical systems.

[0003] Currently, nonlinear optical crystals applied to the ultraviolet solar blind band include β-BaB2O4, LiB3O5, CsLiB6O 10 , KBe2BO3F2, KH2PO4 (KDP) crystals, etc. Although the crystal growth technologies of these materials have become increasingly mature, there are still obvious deficiencies: such as easy deliquescence of crystals, long growth cycles, and serious layered growth habits. Summary of the Invention

[0004] In view of this, the present disclosure provides a guanidine nitrate nonlinear optical crystal, a preparation method thereof, and an application thereof.

[0005] According to an embodiment of one aspect of the present disclosure, a guanidine nitrate nonlinear optical crystal is provided, wherein the chemical formula of the guanidine nitrate nonlinear optical crystal is C(NH2)3NO3, belonging to the monoclinic system, with the space group Cm, and the unit cell parameters are: a = 12.69 ± 0.02 Å, b = 7.27 ± 0.02 Å, c = 3.63 ± 0.02 Å, alpha = 90°, beta = 120.85 ± 0.02°, gamma = 90°, Z = 2.

[0006] According to an embodiment of the present disclosure, the guanidine nitrate nonlinear optical crystal includes diffraction peaks at one or more of 14.6° ± 0.2°, 16.3° ± 0.2°, 24.6° ± 0.2°, 28.2° ± 0.2°, 29.5° ± 0.2°, 35.9° ± 0.2° in the X-ray powder diffraction pattern with 2θ as the diffraction angle.

[0007] According to an embodiment of the present disclosure, the size of the guanidine nitrate nonlinear optical crystal in the length direction is 5 - 30 mm.

[0008] According to an embodiment of the present disclosure, the phase matching direction of the guanidine nitrate nonlinear optical crystal includes the

[100] direction.

[0009] According to an embodiment of another aspect of the present disclosure, a method for preparing a guanidine nitrate nonlinear optical crystal is further provided, including: dissolving a guanidine group-containing compound and a nitrate group-containing compound in water to obtain an aqueous guanidine nitrate solution; crystallizing guanidine nitrate by a room temperature solution method or a hydrothermal method to obtain a guanidine nitrate nonlinear optical crystal; wherein, the above-mentioned room temperature solution method includes: placing the above-mentioned aqueous guanidine nitrate solution in a sealed container, and allowing the solvent in the solution to volatilize through a small hole at 15-40 °C to obtain the above-mentioned guanidine nitrate nonlinear optical crystal; the above-mentioned hydrothermal method includes: placing the above-mentioned aqueous guanidine nitrate solution in a sealed container, heating it to 50-180 °C at a rate of 20-60 °C / h, maintaining the temperature for 3-15 days, and then cooling it to room temperature at a rate of 10-100 °C / day to obtain the above-mentioned guanidine nitrate nonlinear optical crystal.

[0010] According to an embodiment of the present disclosure, the molar ratio of the above-mentioned guanidine group-containing compound to the above-mentioned nitrate group-containing compound is (0.8-1.2):(0.8-1.2).

[0011] According to an embodiment of the present disclosure, the above-mentioned guanidine group-containing compound includes at least one of guanidine carbonate, guanidine sulfate, guanidine phosphate, and guanidine chloride.

[0012] According to an embodiment of the present disclosure, the above-mentioned nitrate group-containing compound includes at least one of nitric acid, barium nitrate, calcium nitrate, strontium nitrate, and ammonium nitrate.

[0013] According to an embodiment of another aspect of the present disclosure, an application of a guanidine nitrate nonlinear optical crystal in an optical device is further provided.

[0014] According to an embodiment of the present disclosure, the above-mentioned optical device includes a frequency doubler, an up or down frequency converter, or an optical parametric oscillator.

[0015] According to an embodiment of the present disclosure, the above-mentioned guanidine nitrate nonlinear optical crystal is used for frequency-doubled light output in the ultraviolet solar blind band.

[0016] According to an embodiment of the present disclosure, the above-mentioned guanidine nitrate nonlinear optical crystal performs second harmonic, third harmonic, fourth harmonic, fifth harmonic, or sixth harmonic light output on the fundamental frequency light of 1064 nm output by a Nd:YAG laser.

[0017] According to an embodiment of the present disclosure, the frequency doubling effect of the guanidine nitrate nonlinear optical crystal can be 5-6 times that of KDP, the absorption cut-off edge is in the ultraviolet solar blind band (200-280 nm), phase matching in the target band is achieved through the birefringence regulation of the crystal, and combined with its strong frequency doubling response characteristics, frequency-doubled laser output in the ultraviolet solar blind band can be effectively generated.

[0018] According to an embodiment of the present disclosure, the guanidine nitrate nonlinear optical crystal grown by the room temperature solution method and the hydrothermal method has no obvious layered growth habit, and a guanidine nitrate nonlinear optical crystal with a size of millimeters can be obtained. The preparation method provided by the embodiment of the present disclosure has the advantages of simple operation method, low cost, short growth cycle, etc.

[0019] The guanidine nitrate nonlinear optical crystal provided by the embodiment of the present disclosure has a wide light transmission band, is easy to cut, polish and preserve, and can be used as an ultraviolet solar blind nonlinear optical crystal in a solid-state laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Shows the crystal structure diagram of the guanidine nitrate nonlinear optical crystal provided by the embodiment of the present disclosure;

[0021] Figure 2 Shows the X-ray powder diffraction spectrum of the guanidine nitrate nonlinear optical crystal provided by the embodiment of the present disclosure;

[0022] Figure 3 Shows the working principle diagram of the nonlinear optical device made of the nonlinear optical crystal provided by the embodiment of the present disclosure, where 1 is a laser, 2 is a convex lens, 3 is a nonlinear optical crystal, 4 is a prism, and 5 is a filter. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the following detailed description, for the sake of explanation, many specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. However, it is obvious that one or more embodiments can be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present disclosure.

[0024] The terms used herein are merely for describing specific embodiments and are not intended to limit the present disclosure. The term "including" used herein indicates the presence of features, steps, operations, but does not exclude the presence or addition of one or more other features.

[0025] In the case of using expressions such as "at least one of A, B, and C, etc.", generally, it should be interpreted according to the meaning that those skilled in the art usually understand this expression (for example, "a system having at least one of A, B, and C" should include, but not be limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", generally, it should be interpreted according to the meaning that those skilled in the art usually understand this expression (for example, "a system having at least one of A, B, or C" should include, but not be limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0026] In the field of nonlinear optics, the nonlinear optical properties of different compounds often show significant unpredictability, which is due to the extreme sensitivity of the nonlinear optical properties to material composition, electronic structure, and microscopic interactions, etc. Although a non-centrosymmetric crystal structure is a necessary condition for second-order nonlinear optical activity, the nonlinear optical properties (such as second harmonic generation efficiency, nonlinear susceptibility, etc.) are also subject to complex regulation by intra- / inter-molecular charge transfer characteristics, hyperconjugation effects, excited state energy level distributions, and the cooperativity of dipole orientations in the crystal lattice. There is a lack of a universal quantitative correlation between crystal form parameters (such as unit cell parameters, molecular packing patterns) and nonlinear optical properties (such as second harmonic generation efficiency, nonlinear susceptibility).

[0027] In addition, microscopic mechanisms such as local field correction factors, phase matching conditions, electron-phonon coupling strengths, and defect-induced local states can all significantly modulate nonlinear optical behavior, and these factors often cannot be directly obtained through conventional crystal form analysis, which further exacerbates the difficulty of predicting nonlinear optical properties.

[0028] Surprisingly, in the process of implementing the present disclosure, it is found that the guanidine nitrate nonlinear optical crystal with a special crystal structure can be applied in the ultraviolet solar blind region.

[0029] Specifically, according to an embodiment of one aspect of the present disclosure, a guanidine nitrate nonlinear optical crystal is provided, wherein the chemical formula of the guanidine nitrate nonlinear optical crystal is C(NH2)3NO3, belonging to the monoclinic system, the space group is Cm, and the unit cell parameters are: a = 12.69 ± 0.02 Å, b = 7.27 ± 0.02 Å, c = 3.63 ± 0.02 Å, alpha = 90°, beta = 120.85 ± 0.02°, gamma = 90°, Z = 2. Exemplarily, the unit cell parameters can be: a = 12.686(3) Å, b = 7.274(2) Å, c = 3.629(1) Å, β = 120.85(2), Z = 2; the unit cell volume is 287.496 Å3 。

[0030] According to an embodiment of the present disclosure, the molecular weight of the guanidine nitrate nonlinear optical crystal can be 122.10.

[0031] According to an embodiment of the present disclosure, the second harmonic generation (SHG) effect of the guanidine nitrate nonlinear optical crystal can reach 5-6 times that of KDP, and the absorption cut-off edge is in the ultraviolet solar blind region (200-280 nm). By adjusting the birefringence of the crystal, phase matching in the target wavelength band can be achieved. Combining its strong SHG response characteristics, the SHG laser output in the ultraviolet solar blind band can be effectively generated.

[0032] Figure 1 The crystal structure diagram of the guanidine nitrate nonlinear optical crystal provided by the embodiment of the present disclosure is shown.

[0033] According to an embodiment of the present disclosure, the X-ray powder diffraction pattern of the guanidine nitrate nonlinear optical crystal with 2θ as the diffraction angle may include diffraction peaks at one or more of 14.6°±0.2°, 16.3°±0.2°, and 28.2°±0.2°.

[0034] According to an embodiment of the present disclosure, the X-ray powder diffraction pattern of the guanidine nitrate nonlinear optical crystal with 2θ as the diffraction angle may further include diffraction peaks at one or more of 24.6°±0.2°, 29.5°±0.2°, and 35.9°±0.2°.

[0035] Exemplarily, the X-ray powder diffraction pattern of the guanidine nitrate nonlinear optical crystal with 2θ as the diffraction angle may include diffraction peaks at 14.6°±0.2°, 16.3°±0.2°, 24.6°±0.2°, 28.2°±0.2°, 29.5°±0.2°, and 35.9°±0.2°.

[0036] According to an embodiment of the present disclosure, a nonlinear optical crystal is a functional crystal material that can adjust the characteristics of a laser such as frequency, phase, and intensity through the nonlinear optical effect. A crystal can be a solid formed by the periodic and orderly arrangement of atoms, ions, or molecules in three-dimensional space. Different crystals can be identified and distinguished from each other through one or more characterization techniques, including, for example, X-ray powder diffraction (XRPD). According to an embodiment of the present disclosure, the X-ray powder diffraction pattern of the guanidine nitrate nonlinear optical crystal has one or more diffraction peaks at one or more specified 2θ diffraction angles.

[0037] According to an embodiment of the present disclosure, X-ray powder diffraction is a method in X-ray diffraction analysis for performing diffraction analysis on a powdered polycrystalline sample using monochromatic X-rays. An X-ray powder diffraction pattern refers to an experimentally obtained pattern that plots the signal position (abscissa) relative to the signal intensity (ordinate). For amorphous materials, the X-ray powder diffraction pattern may include one or more broad and flat diffraction peaks; for crystalline materials, the X-ray powder diffraction pattern may include one or more thin, tall, and sharp diffraction peaks, and each diffraction peak is identified by its angular value, which is measured in terms of the angle 2θ and depicted on the abscissa of the X-ray powder diffraction pattern.

[0038] According to an embodiment of the present disclosure, the repeatability of the measured angular value is within the range of ±0.2°, that is, the angular value can be the angular value + 0.2°, the angular value - 0.2°, or any value between these two endpoints (the angular value + 0.2° and the angular value - 0.2°). Optionally, the repeatability of the measured angular value is within the range of ±0.1°.

[0039] According to an embodiment of the present disclosure, the X-ray powder diffraction pattern of the guanidine nitrate nonlinear optical crystal is substantially as Figure 2 shown. "Substantially" means that with respect to the X-ray powder diffraction pattern, the positions and intensities of its diffraction peaks can vary. For example, the diffraction peak position (2θ) may show some variability between devices, typically up to 0.2°. Sometimes, due to differences in device calibration, the variability may be higher than 0.2°.

[0040] According to an embodiment of the present disclosure, the size of the guanidine nitrate nonlinear optical crystal in the length direction is 5 - 30 mm. Exemplarily, the size of the guanidine nitrate nonlinear optical crystal in the length direction can be 5 mm, 8 mm, 10 mm, 12 mm, 15 mm, 18 mm, 20 mm, 25 mm, 30 mm, or any range between any two of the above values.

[0041] The phase matching direction of a nonlinear optical crystal is an important factor for achieving efficient energy conversion, which is related to various factors such as the crystal birefringence characteristics, wavelength dispersion, temperature sensitivity, and nonlinear coefficient tensor components. For example, crystals of the same crystal form may have a shift in the matching direction due to differences in birefringence or defect-induced local field distortion, etc. Therefore, the phase matching direction of a nonlinear optical crystal is unpredictable.

[0042] According to an embodiment of the present disclosure, the phase matching direction of the guanidine nitrate nonlinear optical crystal may include the

[100] direction. The

[100] direction may represent the positive direction along the a-axis of the unit cell, that is, the direction from the origin (0, 0, 0) of the unit cell to the vertex (1, 0, 0).

[0043] According to an embodiment of another aspect of the present disclosure, a method for preparing a guanidine nitrate nonlinear optical crystal is further provided, which includes step S1 and step S2.

[0044] In step S1, a guanidine group-containing compound and a nitrate group-containing compound are dissolved in water to obtain an aqueous guanidine nitrate solution.

[0045] In step S2, the guanidine nitrate is crystallized by a room-temperature solution method or a hydrothermal method to obtain a guanidine nitrate nonlinear optical crystal. Among them, the room-temperature solution method includes: placing the aqueous guanidine nitrate solution in a sealed container, and allowing the solvent in the solution to volatilize through small holes at 15-40 °C to obtain a guanidine nitrate nonlinear optical crystal. The hydrothermal method includes: placing the aqueous guanidine nitrate solution in a sealed container, heating it to 50-180 °C at a rate of 20-60 °C / h, keeping it at a constant temperature for 3-15 days, and then cooling it to room temperature at a rate of 10-100 °C / day to obtain a guanidine nitrate nonlinear optical crystal.

[0046] According to the embodiment of the present disclosure, the guanidine nitrate nonlinear optical crystal grown by the room-temperature solution method and the hydrothermal method has no obvious layered growth habit, and a guanidine nitrate nonlinear optical crystal with a size of millimeters can be obtained. The preparation method provided by the embodiment of the present disclosure has the advantages of simple operation method, low cost, short growth cycle, etc. The second harmonic generation effect of the guanidine nitrate nonlinear optical crystal prepared by the embodiment of the present disclosure can reach 5-6 times that of KDP, and the absorption cut-off edge is in the ultraviolet solar blind region (200-280 nm). By adjusting the birefringence of the crystal to achieve phase matching in the target wavelength band, and combining its strong second harmonic generation response characteristics, the second harmonic laser output in the ultraviolet solar blind band can be effectively generated.

[0047] According to the embodiment of the present disclosure, in step S1, the guanidine group-containing compound may include at least one of guanidine carbonate, guanidine sulfate, guanidine phosphate, and guanidine chloride. The nitrate group-containing compound may include at least one of nitric acid, barium nitrate, calcium nitrate, strontium nitrate, and ammonium nitrate.

[0048] According to the embodiment of the present disclosure, in step S1, the molar ratio of the guanidine group-containing compound to the nitrate group-containing compound may be (0.8-1.2):(0.8-1.2). Exemplarily, the molar ratio of the guanidine group-containing compound to the nitrate group-containing compound may be 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1 or the range between any two of the above ratios. Optionally, the molar ratio of the guanidine group-containing compound to the nitrate group-containing compound may be 1:1.

[0049] Optionally, in step S2, in the room-temperature solution method, the solvent in the solution may volatilize through small holes at room temperature. Exemplarily, the solvent in the solution may volatilize through small holes at 15 °C, 18 °C, 20 °C, 22 °C, 25 °C, 28 °C, 30 °C, 32 °C, 35 °C, 38 °C, 40 °C or the range between any two of the above values.

[0050] Exemplarily, the room-temperature solution method may include: transferring an aqueous solution of guanidine nitrate into a beaker, treating it by ultrasonic waves to fully mix and dissolve it, adjusting the pH value of the solution to 1-11, filtering it with filter paper, then sealing it with a polyvinyl chloride film, placing it in a static environment without shaking, pollution, or air convection, piercing several small holes in the seal to adjust the evaporation rate of the solvent in the solution, and standing it at room temperature. After the growth is completed, a guanidine nitrate nonlinear optical crystal with a millimeter size is obtained.

[0051] Optionally, in step S2, in the hydrothermal method, the heating rate may be 20°C / h, 25°C / h, 30°C / h, 35°C / h, 40°C / h, 45°C / h, 50°C / h, 55°C / h, 60°C / h, or in the range between any two of the above values. The constant-temperature time may be 3 days, 4 days, 5 days, 6 days, 7 days, 8 days, 9 days, 10 days, 11 days, 12 days, 13 days, 14 days, 15 days, or in the range between any two of the above values. The cooling rate may be 10°C / day, 20°C / day, 30°C / day, 40°C / day, 50°C / day, 60°C / day, 70°C / day, 80°C / day, 90°C / day, 100°C / day, or in the range between any two of the above values.

[0052] Exemplarily, the hydrothermal method may include: transferring an aqueous solution of guanidine nitrate into the polytetrafluoroethylene liner of a high-pressure reactor and tightly screwing and sealing the mouth of the reactor; placing the high-pressure reactor in an incubator, heating it to 50-180°C at a rate of 20-60°C / h, maintaining the temperature for 3-15 days, and then cooling it to room temperature at a cooling rate of 10-100°C / day; opening the high-pressure reactor to obtain a guanidine nitrate nonlinear optical crystal with a millimeter size in a colorless clear solution.

[0053] According to an embodiment of another aspect of the present disclosure, an application of a guanidine nitrate nonlinear optical crystal in an optical device is also provided.

[0054] The guanidine nitrate nonlinear optical crystal provided by the embodiment of the present disclosure has a wide light transmission band, is easy to cut, polish, and preserve, and can be used as an ultraviolet solar-blind nonlinear optical crystal in a solid-state laser.

[0055] The guanidine nitrate nonlinear optical crystal provided by the embodiment of the present disclosure can cut the crystal according to the required angle, thickness, and cross-sectional size, polish the light-transmitting surface of the crystal and coat it with a dielectric film, and then it can be used as a nonlinear optical device.

[0056] According to an embodiment of the present disclosure, the optical device includes a frequency doubler, an up or down frequency converter, or an optical parametric oscillator.

[0057] According to an embodiment of the present disclosure, the guanidine nitrate nonlinear optical crystal is used for the second harmonic light output in the ultraviolet solar blind band.

[0058] According to an embodiment of the present disclosure, the guanidine nitrate nonlinear optical crystal performs second harmonic, third harmonic, fourth harmonic, fifth harmonic or sixth harmonic light output on the fundamental light of 1064 nm output by a Nd:YAG laser.

[0059] The following lists multiple specific embodiments to elaborate on the technical solutions of the present disclosure. It should be noted that the specific embodiments below are only for illustration and do not limit the present disclosure.

[0060] Embodiment 1

[0061] This embodiment provides a guanidine nitrate nonlinear optical crystal and a preparation method thereof.

[0062] The guanidine nitrate nonlinear optical crystal is grown by a room temperature solution method and includes the following steps:

[0063] (1) Mix guanidine carbonate and nitric acid evenly at a molar ratio of 1:1, and add 100 mL of deionized water to make them fully mixed and dissolved.

[0064] (2) Transfer the mixed solution in step (1) into a 200 mL beaker, treat it with ultrasonic waves to make it fully mixed and dissolved, adjust the pH value of the solution to 7, filter it with filter paper, seal it with a polyvinyl chloride film, and place it in a static environment without shaking, pollution, and air convection. Make several small holes in the seal to adjust the evaporation rate of the solvent in the solution, and let it stand at room temperature. After the growth is completed, a guanidine nitrate nonlinear optical crystal with a size of Φ12 mm × 15 mm × 9 mm is obtained.

[0065] Embodiment 2

[0066] This embodiment provides a guanidine nitrate nonlinear optical crystal and a preparation method thereof.

[0067] The guanidine nitrate nonlinear optical crystal is grown by a room temperature solution method and includes the following steps:

[0068] (1) Mix guanidine sulfate and barium nitrate evenly at a molar ratio of = 1:0.8, and add 10 mL of deionized water to make them fully mixed and dissolved.

[0069] (2) Transfer the mixed solution in step (1) into a 50 mL beaker, and treat it with ultrasonic waves to make it fully mixed and dissolved. Adjust the pH value of the solution to 1, filter it with filter paper, seal it with a polyvinyl chloride film, and place it in a static environment without shaking, pollution, or air convection. Make several small holes in the seal to adjust the evaporation rate of the solvent in the solution, and let it stand at room temperature. After the growth is completed, a guanidine nitrate nonlinear optical crystal with dimensions of Φ9 mm × 7 mm × 7 mm is obtained.

[0070] Example 3

[0071] This example provides a guanidine nitrate nonlinear optical crystal and its preparation method.

[0072] The guanidine nitrate nonlinear optical crystal is prepared by solution growth at room temperature, and the method includes the following steps:

[0073] (1) Mix guanidine sulfate and calcium nitrate evenly at a molar ratio of 1.2:1, and add 75 mL of deionized water to make it fully mixed and dissolved.

[0074] (2) Transfer the mixed solution in step (1) into a 150 mL beaker, and treat it with ultrasonic waves to make it fully mixed and dissolved. Adjust the pH value of the solution to 11, filter it with filter paper, seal it with a polyvinyl chloride film, and place it in a static environment without shaking, pollution, or air convection. Make several small holes in the seal to adjust the evaporation rate of the solvent in the solution, and let it stand at room temperature. After the growth is completed, a guanidine nitrate nonlinear optical crystal with dimensions of Φ19 mm × 17 mm × 12 mm is obtained.

[0075] Example 4

[0076] This example provides a guanidine nitrate nonlinear optical crystal and its preparation method.

[0077] The guanidine nitrate nonlinear optical crystal is prepared by solution growth at room temperature, and the method includes the following steps:

[0078] (1) Mix guanidine phosphate and strontium nitrate evenly at a molar ratio of 0.8:1, and add 120 mL of deionized water to make it fully mixed and dissolved.

[0079] (2) Transfer the mixed solution in step (1) into a 250 mL beaker, and treat it with ultrasonic waves to make it fully mixed and dissolved. Adjust the pH value of the solution to 3, filter it with filter paper, seal it with a polyvinyl chloride film, and place it in a static environment without shaking, pollution, or air convection. Make several small holes in the seal to adjust the evaporation rate of the solvent in the solution, and let it stand at room temperature. After the growth is completed, a guanidine nitrate nonlinear optical crystal with dimensions of Φ21 mm × 16 mm × 15 mm is obtained.

[0080] Example 5

[0081] This embodiment provides a guanidine nitrate nonlinear optical crystal and a preparation method thereof.

[0082] The guanidine nitrate nonlinear optical crystal is grown by the room temperature solution method and comprises the following steps:

[0083] (1) Mix guanidine chloride and ammonium nitrate evenly according to a molar ratio of 1:1.2, and add 200 mL of deionized water to make them fully mixed and dissolved;

[0084] (2) Transfer the mixed solution in step (1) into a beaker with a volume of 300 mL, and process it by ultrasonic waves to make them fully mixed and dissolved. Adjust the pH value of the solution to 9, filter it with filter paper, then seal it with a polyvinyl chloride film, and place it in a static environment without shaking, pollution, and air convection. Make several small holes in the seal to adjust the evaporation rate of the solvent in the solution, and let it stand at room temperature. After the growth is completed, a guanidine nitrate nonlinear optical crystal with a size of Φ25mm×20mm×14mm can be obtained;

[0085] Example 6

[0086] This embodiment provides a guanidine nitrate nonlinear optical crystal and a preparation method thereof.

[0087] The guanidine nitrate nonlinear optical crystal is grown by the hydrothermal method and comprises the following steps:

[0088] (1) Mix guanidine carbonate and ammonium nitrate-containing evenly according to a molar ratio of =1:1, and add 50 mL of deionized water to make them fully mixed and dissolved;

[0089] (2) Transfer the mixed solution in step (1) into the polytetrafluoroethylene liner of a high-pressure reactor with a volume of 100 mL, and tighten the mouth of the reactor to seal it. Place the high-pressure reactor in an incubator, heat it to 120 °C at a rate of 20 °C / h, keep it at a constant temperature for 3 days, and then cool it to room temperature at a cooling rate of 20 °C / day. Open the high-pressure reactor, and a guanidine nitrate nonlinear optical crystal with a size of Φ30mm×20mm×16mm can be obtained in the colorless clear solution.

[0090] Example 7

[0091] This embodiment provides a guanidine nitrate nonlinear optical crystal and a preparation method thereof.

[0092] The guanidine nitrate nonlinear optical crystal is grown by the hydrothermal method and comprises the following steps:

[0093] (1) Mix guanidine phosphate and nitric acid-containing evenly according to a molar ratio of 1:0.8, and add 20 mL of deionized water to make them fully mixed and dissolved.

[0094] (2) Transfer the mixed solution in step (1) into the PTFE liner of a 50 mL high-pressure reactor, and tightly seal the reactor opening. Place the high-pressure reactor in an incubator, heat it to 160 °C at a rate of 40 °C / h, keep it at a constant temperature for 10 days, and then cool it to room temperature at a rate of 60 °C / day. Open the high-pressure reactor to obtain a guanidine nitrate nonlinear optical crystal with dimensions of Φ17 mm × 16 mm × 13 mm in the colorless clear solution.

[0095] Example 8

[0096] This example provides a guanidine nitrate nonlinear optical crystal and its preparation method.

[0097] The guanidine nitrate nonlinear optical crystal is prepared by hydrothermal growth, including the following steps:

[0098] (1) Mix guanidine sulfate and calcium nitrate-containing in a molar ratio of 1:1 evenly, and add 25 mL of deionized water to make it fully mixed and dissolved.

[0099] (2) Transfer the mixed solution in step (1) into the PTFE liner of a 50 mL high-pressure reactor, and tightly seal the reactor opening. Place the high-pressure reactor in an incubator, heat it to 180 °C at a rate of 60 °C / h, keep it at a constant temperature for 7 days, and then cool it to room temperature at a rate of 100 °C / day. Open the high-pressure reactor to obtain a guanidine nitrate nonlinear optical crystal with dimensions of Φ22 mm × 14 mm × 12 mm in the colorless clear solution.

[0100] Example 9

[0101] This example provides a guanidine nitrate nonlinear optical crystal and its preparation method.

[0102] The guanidine nitrate nonlinear optical crystal is prepared by hydrothermal growth, including the following steps:

[0103] (1) Mix guanidine sulfate and barium nitrate-containing in a molar ratio of 0.8:1 evenly, and add 5 mL of deionized water to make it fully mixed and dissolved.

[0104] (2) Transfer the mixed solution in step (1) into the PTFE liner of a 25 mL high-pressure reactor, and tightly seal the reactor opening. Place the high-pressure reactor in an incubator, heat it to 50 °C at a rate of 25 °C / h, keep it at a constant temperature for 15 days, and then cool it to room temperature at a rate of 10 °C / day. d. Open the high-pressure reactor to obtain a guanidine nitrate nonlinear optical crystal with dimensions of Φ15 mm × 13 mm × 10 mm in the colorless clear solution.

[0105] Example 10

[0106] This embodiment provides a guanidine nitrate nonlinear optical crystal and a preparation method thereof.

[0107] The guanidine nitrate nonlinear optical crystal is grown by a hydrothermal method, including the following steps:

[0108] (1) Mix guanidine chloride and strontium nitrate in a molar ratio of 1.2:1 evenly, and add 30 mL of deionized water to make them fully mixed and dissolved.

[0109] (2) Transfer the mixed solution in step (1) into the polytetrafluoroethylene liner of a high-pressure reactor with a volume of 50 mL, and tighten the mouth of the reactor to seal it. Place the high-pressure reactor in an incubator, heat it to 150 °C at a rate of 30 °C / h, keep it at a constant temperature for 10 days, and then cool it to room temperature at a cooling rate of 70 °C / day. Open the high-pressure reactor, and a guanidine nitrate nonlinear optical crystal with dimensions of Φ21 mm × 16 mm × 12 mm is obtained in the colorless clear solution.

[0110] Perform X-ray powder diffraction detection on the guanidine nitrate nonlinear optical crystals provided in Examples 1 to 10. The X-ray powder diffraction patterns are basically as Figure 2 shown.

[0111] Process the guanidine nitrate nonlinear optical crystals provided in Examples 1 to 10 in the phase-matching direction, place them at the position of 3 as shown in the appendix Figure 3 shown. At room temperature, use a Q-switched Nd:YAG laser as the light source, with an incident wavelength of 532 nm. The infrared beam with a wavelength of 532 nm emitted by the Q-switched Nd:YAG laser 1 is focused by the convex lens 2 and then enters the nonlinear optical crystal 3, generating a second harmonic generation light with a wavelength of 266 nm. After being split by the prism 4 and filtered by the filter 5, the output intensity is about 5 to 6 times that of KDP under the same conditions.

[0112] As mentioned above, it is only a preferred embodiment of the present disclosure and is not used to limit the present disclosure. Any person skilled in the art, within the spirit and principle of the present disclosure, any modification, equivalent replacement, improvement, etc. made to the technical method are still included within the protection scope of the technical solution of the present disclosure.

Claims

1. A guanidine nitrate nonlinear optical crystal, wherein: The chemical formula of the guanidine nitrate nonlinear optical crystal is C(NH2)3NO3, it belongs to the monoclinic crystal system, the space group is Cm, and the unit cell parameters are: a=12.69±0.02Å, b=7.27±0.02Å, c=3.63±0.02Å, alpha=90°, beta=120.85±0.02°, gamma=90°, and Z=2.

2. The guanidine nitrate nonlinear optical crystal according to claim 1, wherein: The guanidine nitrate nonlinear optical crystal includes one or more diffraction peaks at 14.6°±0.2°, 16.3°±0.2°, and 28.2°±0.2° in an X-ray powder diffraction spectrum with 2θ as the diffraction angle.

3. The guanidine nitrate nonlinear optical crystal according to claim 1 or 2, wherein: The length of the guanidine nitrate nonlinear optical crystal is 5 to 30 mm; The phase matching direction of the guanidine nitrate nonlinear optical crystal includes the [100] direction.

4. The method for preparing a guanidine nitrate nonlinear optical crystal according to any one of claims 1 to 3, comprising: Dissolving a guanidine group-containing compound and a nitrate group-containing compound in water to obtain a guanidine nitrate aqueous solution; guanidine nitrate is crystallized by a room temperature solution method or a hydrothermal method to obtain a guanidine nitrate nonlinear optical crystal; The room temperature solution method comprises: placing the guanidine nitrate aqueous solution in a sealed container, allowing the solvent in the solution to volatilize through a small hole at 15-40° C., to obtain the guanidine nitrate nonlinear optical crystal; The hydrothermal method comprises: placing the guanidine nitrate aqueous solution in a sealed container, heating it to 50-180°C at a rate of 20-60°C / h, keeping the temperature constant for 3-15 days, and then cooling it to room temperature at a rate of 10-100°C / day to obtain the guanidine nitrate nonlinear optical crystal.

5. The preparation method according to claim 4, wherein The molar ratio of the guanidine-containing compound to the nitrate-containing compound is (0.8-1.2): (0.8-1.2).

6. The preparation method according to claim 4 or 5, wherein: The guanidine group-containing compound includes at least one of guanidine carbonate, guanidine sulfate, guanidine phosphate and guanidine chloride; The nitrate-containing compound includes at least one of nitric acid, barium nitrate, calcium nitrate, strontium nitrate and ammonium nitrate.

7. Use of the guanidine nitrate nonlinear optical crystal according to any one of claims 1 to 3 in an optical device.

8. The use according to claim 7, wherein: The optical device includes a frequency doubling generator, an up or down frequency converter or an optical parametric oscillator.

9. The use according to claim 7, wherein: The guanidine nitrate nonlinear optical crystal is used for frequency-doubled light output in the ultraviolet solar-blind band.

10. The use according to claim 7, wherein: The guanidine nitrate nonlinear optical crystal performs frequency doubling, frequency tripling, frequency quadrupling, frequency quintupleting or frequency sextupleting harmonic light output on the 1064nm fundamental frequency light output by the Nd:YAG laser.

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