A chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material, a preparation method and application thereof

Abstract

This invention discloses a chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material, its preparation method, and its applications. The crystal material comprises an organic component and an inorganic component. The inorganic component is germanium and a halogen, and the organic component is a chiral 1,2,3,4-tetrahydro-1-naphthylamine cation, with the general chemical formula (…). R / S -THNA)GeX3, where Ge is a divalent germanium ion and X is a halide anion; this crystalline material crystallizes in chiral space group 1. P2 1. It has a non-centrosymmetric molecular structure, with the inorganic components having a polar trigonal pyramidal configuration, and the polar trigonal pyramids are discretely distributed. The crystal material of this invention completely severs the connection of secondary coordination bonds, inducing germanium ions to form a zero-dimensional discrete low-coordination trigonal pyramidal configuration with extremely strong dipole moments, fundamentally breaking the octahedral coordination network of germanium halides based on corner or edge sharing, and exhibiting extremely high SHG overtone response intensity.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic functional materials technology, specifically relating to a chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material, its preparation method, and its application. Background Technology

[0002] Nonlinear optical (NLO) materials are those whose polarization intensity exhibits a nonlinear relationship with the intensity of the incident photoelectric field under strong light (such as laser). These materials are the core components of modern laser technology and optoelectronics, playing an irreplaceable and crucial role in cutting-edge fields such as laser frequency conversion (e.g., frequency doubling, sum-frequency conversion, difference-frequency conversion, optical parametric oscillation), photoelectric modulation, optical signal processing, high-density optical storage, and quantum communication. Among these applications, second harmonic generation (SHG, often referred to as the frequency doubling effect) is one of the most fundamental and important applications of nonlinear optical materials. It can convert lower-frequency (longer wavelength) incident laser light into higher-frequency (shorter wavelength) output laser light, thereby significantly broadening the output wavelength range of commercial solid-state lasers.

[0003] Currently, nonlinear optical crystals are mainly classified into inorganic materials, organic materials, and organic-inorganic hybrid halide materials. Inorganic materials, such as KDP and LiNbO3, are widely used commercially due to their good physicochemical stability, but they suffer from limitations such as low birefringence, limited overtone response, or difficulty in achieving molecular-level structural control. Pure organic nonlinear crystals, while exhibiting strong overtone effects, often suffer from poor thermal stability and mechanical properties. In recent years, organic-inorganic hybrid halide materials have rapidly become a research hotspot and breakthrough in the field of nonlinear optical functional materials due to their combination of the high stability and excellent thermal properties of inorganic components with the structural flexibility and high tunability of organic components. The basic building block of organic-inorganic hybrid halide nonlinear optical materials is an octahedral structure formed by metal atoms and halogen atoms through ionic bonds. Organic components are interspersed within the octahedral framework of metal halides. Among these, germanium halides, due to the divalent germanium ions (Ge... 2+ The outer layer has stereochemical activity 4 s 2 Lone pairs of electrons readily induce microstructural distortions, thereby breaking spatial inversion symmetry and favoring the formation of non-centrosymmetric structures. Their optical and defect properties have attracted widespread attention from researchers. During their research, the inventors discovered that in conventional germanium halides, Ge... 2+ It often forms [GeX6] with surrounding halide ions. 4- Octahedrons, further connected by sharing corners or edges to form one-dimensional chains, two-dimensional layers, or three-dimensional networks, this strong coordination bonding limits the development of Ge2+ 4 s 2 The stereochemical activity of lone pairs of electrons limits the SHG harmonic signal.

[0004] Providing a nonlinear optical crystal material with ultra-high SHG frequency doubling response is one of the main ways to solve the above problems. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material, its preparation method, and its applications. By introducing a chiral 1,2,3,4-tetrahydro-1-naphthylamine cation with large steric hindrance, which synergistically interacts with the lone pair electrons of germanium ions, a discrete polar trigonal pyramidal configuration is successfully constructed. This completely severs the connection of secondary coordination bonds, inducing germanium ions to form a zero-dimensional discrete low-coordination trigonal pyramidal configuration with extremely strong dipole moments. This fundamentally breaks the octahedral coordination network of germanium halides based on shared corners or edges. This chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material exhibits extremely high SHG overtone response intensity.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: On one hand, a chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material is provided, comprising an organic component and an inorganic component, wherein the inorganic component is germanium and a halogen, and the organic component is a chiral 1,2,3,4-tetrahydro-1-naphthylamine cation with the general chemical formula (…). R / S -THNA)GeX3, where R / S -THAN represents the chiral 1,2,3,4-tetrahydro-1-naphthylamine cation, Ge represents divalent germanium ion, and X represents halide anion; The chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material crystallizes in the chiral space group. P2 1. It has a non-centrosymmetric molecular structure; the inorganic component has a polar trigonal pyramidal configuration, and the polar trigonal pyramids are discretely distributed.

[0007] Furthermore, a method for preparing the above-mentioned chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material is provided, comprising: Germanium dioxide and chiral 1,2,3,4-tetrahydro-1-naphthylamine were mixed with hypophosphoric acid solution and hydrohalic acid solution, and heated and stirred until the solution became clear to obtain the precursor solution. A chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material was obtained by a slow cooling crystallization method.

[0008] On the other hand, this invention provides an application of the aforementioned chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material as a second harmonic generation material in laser frequency conversion devices within the field of nonlinear optics.

[0009] Compared with the prior art, the present invention has the following advantages: 1. The chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material of the present invention introduces a chiral 1,2,3,4-tetrahydro-1-naphthylamine cation with large steric hindrance, which cooperates with the lone pair electrons of germanium ions to construct a discrete polar trigonal pyramidal configuration, completely severing the connection of secondary coordination bonds, and inducing germanium ions to form a zero-dimensional discrete low-coordination trigonal pyramidal configuration with extremely strong dipole moments. This fundamentally breaks the octahedral coordination network of germanium halides based on corner or edge sharing, and has extremely high SHG overtone response intensity.

[0010] 2. The method for preparing the above-mentioned chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material of the present invention includes a slow cooling crystallization method. The resulting chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material has a complete crystal face development, high surface optical flatness, and no optical defects such as cracks, bubbles and solvent inclusions inside the crystal, thus endowing the material with the ability to withstand strong femtosecond laser bombardment.

[0011] 3. Preferably, the volume ratio of I-liquid to Br-liquid in this invention is 0.5:1, resulting in a chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material (…). R -THNA)GeI 1.75 Br 1.25 It has the highest harmonic response signal strength, reaching 23.6 times that of the reference KDP crystal.

[0012] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0013] Figure 1 As in Example 1 ( R / S -THNA)GeI3 and Example 2 ( R / S X-ray diffraction structure of single crystal GeBr3 (THNA), where: 1 represents germanium atom, 2 represents carbon atom, 3 represents iodine atom, and 4 represents bromine atom.

[0014] Figure 2 As in Example 1 ( R -THNA)GeI3, Example 2 ( R -THNA)GeBr3 and Example 3 ( R -THNA)GeI 1.75 Br 1.25 Powder X-ray diffraction (PXRD) pattern of the crystal.

[0015] Figure 3 Example 2 ( R Polarization optical microscopy image of -THNA)GeBr3, where A and B represent different cross angles.

[0016] Figure 4 A schematic diagram of the optical path of a femtosecond laser device for testing the frequency doubling response of SHG.

[0017] Figure 5 As in Example 1 ( R -THNA)GeI3, Example 2 ( R -THNA)GeBr3 and Example 3 ( R -THNA)GeI 1.75 Br 1.25 Comparison of the overtone response intensity of powder SHG with reference material KDP under laser excitation at 1000 nm, 1020 nm and 1040 nm.

[0018] Figure 6 For the calculation of Example 1 ( R -THNA)GeI3, Example 2 ( R -THNA)GeBr3 and the ( ) in Example 3 R -THNA)GeI 1.75 Br 1.25 Frequency-dependent SHG coefficient.

[0019] Figure 7 As in Example 1 ( R -THNA)GeI3 and Example 2 ( R A graph showing the change in polarization SHG intensity of -THNA)GeBr3 with the rotation angle of a linear polarizer.

[0020] Figure 8 As in Example 1 ( R -THNA)GeI3 and Example 2 ( R Logarithmic plot of the power-dependent second harmonic generation octave intensity of -THNA)GeBr3. Detailed Implementation

[0021] The technical solution will now be clearly and completely described with reference to the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0022] In the following description, the term "and / or" is used to describe the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. A and B can be singular or plural.

[0023] In the following description, the terms “including,” “containing,” “having,” and “containing” are open-ended terms, meaning that they include but are not limited to.

[0024] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0025] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0027] On one hand, a chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material is provided, comprising an organic component and an inorganic component, wherein the organic component is a chiral 1,2,3,4-tetrahydro-1-naphthylamine cation (C 10 H 14 N + The inorganic components are germanium and halogen, and the general chemical formula is ( R / S -THNA)GeX3, where R / S -THAN represents the chiral 1,2,3,4-tetrahydro-1-naphthylamine cation, and Ge represents the divalent germanium ion Ge. 2+ X is a halide anion; The chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material crystallizes in the chiral space group. P2 1. It has a non-centrosymmetric molecular structure; the inorganic components have a polar trigonal pyramidal configuration, and the polar trigonal pyramids are discretely distributed.

[0028] The chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material of the present invention crystallizes in the chiral space group. P2 1. Based on the lattice stress of sterically hindered organic cations and the 4-dimensionality of germanium ions s 2 The synergistic effect of the lone pair electrons' stereochemical activity, coupled with a non-centrosymmetric molecular structure, causes a strong eccentric shift in the germanium ion center, blocking the bonding between the germanium ion and the three surrounding secondary halide ions, resulting in a discrete [GeX3] inorganic component. - It features a polar trigonal pyramidal configuration, rather than the traditional [GeX6] design. 4- Octahedral configuration.

[0029] In some embodiments, in the polar trigonal pyramidal configuration, the inorganic component germanium ions form chemical bonds with only three halide anions.

[0030] In some embodiments, the halide anion X is a bromide ion and / or an iodide ion. In some preferred embodiments, the halide anion is a bromide ion and an iodide ion, and the general chemical formula of the chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material is ( R / S -THNA)GeI x Br 3-x Where 0 < x < 3. In some further preferred embodiments, the chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material has the chemical formula ( R / S -THNA)GeI 1.75 Br 1.25 .

[0031] During the research process, the inventors discovered that the halogen anions in the hybrid germanium halide nonlinear optical crystal material are bromide ions and / or iodide ions, which can enable the halogen anions to enter the germanium-halogen coordination polyhedron and achieve lattice doping of the hybrid system, thus obtaining a nonlinear optical crystal in which the above-mentioned non-centrosymmetric inorganic components present a discrete polar trigonal pyramidal configuration.

[0032] During their research, the inventors further discovered that the type of halogen has a significant impact on the structure and optical properties of chiral organic-inorganic hybrid germanium halide nonlinear optical crystal materials. When a mixed halogen of bromide and iodide ions is used as the halide anion, lattice distortion and polarizability can be effectively controlled. Furthermore, when the iodine / bromine atomic ratio (I / Br) is 1.49087 (approximately 1.5), i.e., the material's chemical formula is (… R / S -THNA)GeI 1.75 Br 1.25 At that time, the octave response intensity of the crystalline material was the highest, which was 23.6 times that of the reference KDP crystal and 1.66 to 9.45 times that of the pure halogen crystal.

[0033] Secondly, a method for preparing the above-mentioned chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material is provided, comprising the following steps: 1) Germanium dioxide and chiral 1,2,3,4-tetrahydro-1-naphthylamine are mixed with hypophosphoric acid solution and hydrohalic acid solution, and heated and stirred until the solution is clear to obtain a precursor solution; the hydrohalic acid is hydroiodic acid, hydrobromic acid or a mixture thereof; hypophosphoric acid is used to reduce germanium oxide and prevent oxidation of iodide ions and bromide ions; 2) A chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material was obtained by using a slow cooling crystallization method.

[0034] The chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material prepared by the slow cooling crystallization method of the present invention can reach the centimeter scale in macroscopic single crystal size, with complete crystal face development and high surface optical flatness. The crystal is free of optical defects such as cracks, bubbles and solvent inclusions, and has high optical uniformity, giving the material the ability to withstand strong femtosecond laser bombardment.

[0035] The slow cooling crystallization process upon which this invention is based has an extremely high spontaneous impurity removal capability. During the lattice self-assembly process, impurity molecules cannot enter the target lattice. This synthesis route has an extremely high tolerance for the purity of raw materials, which lays a solid material foundation for the low-cost, large-scale industrial production of this nonlinear optical material in the future.

[0036] In some embodiments, the cooling rate in the slow cooling crystallization method is 0.5~2 °C / h, and the cooling range is from 80~100 °C to room temperature.

[0037] In this invention, by controlling the cooling rate, the solubility of the system decreases as the temperature decreases. After reaching the supersaturation threshold, crystal nuclei begin to precipitate spontaneously and grow slowly and densely around the crystal nuclei. At a cooling rate of 0.5~2 ℃ / h, the supersaturation of the solution remains mild and stable, and the crystal growth rate is greater than the secondary nucleation rate, avoiding the explosion of a large number of microcrystals and ensuring that the material is continuously and stably deposited on the surface of the formed crystal nuclei, resulting in the growth of large-sized single crystals.

[0038] In some embodiments, the molar ratio of germanium dioxide to chiral 1,2,3,4-tetrahydro-1-naphthylamine is 1:2.

[0039] When the molar ratio of germanium dioxide to chiral 1,2,3,4-tetrahydro-1-naphthylamine is 1:2, a sufficiently concentrated chiral coordination template can be formed in a strongly acidic environment composed of a hydrohalic acid solution containing hypophosphoric acid. The excess chiral cations effectively encapsulate the inorganic polyhedron, fully transferring its microscopic chiral asymmetry to the inorganic framework. During the subsequent slow cooling crystallization process, the crystal is induced to grow in a non-centrosymmetric space group, resulting in a highly optically homogeneous crystal.

[0040] In some embodiments, the volume ratio of the hydrohalic acid solution to the hypophosphite solution is 1 to 3:1, the mass percentage of the hypophosphite solution is 37%, and the mass percentage of the hydrohalic acid solution is 45 to 60%; the volume molar ratio of the hydrohalic acid solution (mL) to germanium dioxide (mmol) is 10:1.

[0041] In a strongly acidic system formed by hypophosphoric acid solution and hydrohalic acid solution, organic amines undergo complete protonation to form... R -THNA + Cationic hypophosphoric acid, acting as an in-situ reducing agent and reducing protectant, on the one hand, reduces Ge... 4+ Restore to Ge 2+ On the other hand, it strongly inhibits oxygen in the air from I - Ions are oxidized to I₂, ensuring that the solution remains in a non-oxidized state.

[0042] In some preferred embodiments, the halide anions are bromide ions and iodide ions, and the chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material has the general chemical formula ( R / S -THNA)GeI x Br 3-x Where 0 < x < 3, the hydrohalic acid solution is a hydrobromic acid solution and a hydroiodic acid solution, and the preparation method of the precursor solution includes: Germanium dioxide and chiral 1,2,3,4-tetrahydro-1-naphthylamine were mixed with hypophosphite solution and hydroiodic acid solution, and heated and stirred until the solution became clear to obtain I- solution; the volume ratio of hydroiodic acid solution to hypophosphite solution was 1:1; the molar ratio of hydroiodic acid solution (mL) to germanium dioxide (mmol) was 10:1. Germanium dioxide and chiral 1,2,3,4-tetrahydro-1-naphthylamine were mixed with hypophosphite solution and hydrobromic acid solution, and the mixture was heated and stirred until the solution became clear to obtain Br- solution; the volume ratio of the hydrobromic acid solution to the hypophosphite solution was 3:1; the molar ratio of the hydrobromic acid solution (mL) to germanium dioxide (mmol) was 10:1; The above I-liquid and Br-liquid are mixed at a volume ratio of 1~3:3~1, heated and stirred until clear to obtain a precursor solution; preferably, the volume ratio of the I-liquid and Br-liquid is 0.5:1.

[0043] In some embodiments, the heating temperature for heating and stirring until the solution becomes clear is 80-90°C, and the heating and stirring time is 2-3 hours.

[0044] Thirdly, the application of the aforementioned chiral organic-inorganic hybrid germanium halide nonlinear optical crystal materials in the field of nonlinear optics is provided.

[0045] As a further preferred embodiment of the second aspect of the present invention, the application specifically refers to its use as a second-order nonlinear optical-second harmonic generation (SHG) material in a laser frequency converter. In some preferred embodiments, the wavelength of the excitation light of the laser frequency converter is 1020 nm. The chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material at 1020 nm (… R The harmonic response intensity of (-THNA)GeI3) is at least 14.2 times that of KDP, of which ( R -THNA)GeI 1.75 Br 1.25 Its octave response intensity is at least 23.6 times that of KDP.

[0046] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0047] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0048] The hydroiodic acid aqueous solution (HI, 57 wt%), hypophosphite aqueous solution (H3PO2, 37 wt%), and hydrobromic acid aqueous solution (HBr, 48 wt%) used in the following embodiments of the present invention R / S -1,2,3,4-Tetrahydro-1-naphthylamine ( R / S Both THNA and germanium dioxide (GeO2) powders are available from standard commercial channels. To ensure the universality and industrial application value of the technology of this invention, all purchased chemical reagents were used directly in their original packaging specifications without any further recrystallization or distillation purification.

[0049] Prior to the application for this invention, a series of experiments were conducted. Some of the experimental results are listed below to provide a more detailed description of the invention. The following is a detailed description in conjunction with the embodiments.

[0050] Example 1 This embodiment provides a method for growing germanium halide single crystals in a pure iodine system using a slow cooling method. R / S The specific process steps for -THNA)GeI3) are as follows: 1. Feeding and material mixing: Accurately weigh 1 mmol (approximately 0.1046 g) of germanium dioxide (GeO2) powder and 2 mmol (approximately 0.2944 g) of... R -1,2,3,4-Tetrahydro-1-naphthylamine ( R-THNA), and put it into a clean 40 mL glass reaction flask with a polytetrafluoroethylene liner; 2. Solvent preparation and addition: Add the mixed acid to the above reaction flask. The mixed acid is prepared by mixing 57% hydroiodic acid aqueous solution (HI) and 37% hypophosphorous acid aqueous solution (H3PO2) in a volume ratio of 1:1. In this step, 10 mL of the above hydroiodic acid aqueous solution and 10 mL of the above hypophosphorous acid aqueous solution are slowly added dropwise using a pipette. 3. Heating and solvation process: Place a magnetic stir bar in the reaction flask, seal the container and place it in a heat-collecting constant-temperature magnetic stirring oil bath. Turn on the heating program to raise and stabilize the system temperature to 90 ℃. At this temperature, turn on the magnetic stirring and continue stirring for about 2-3 hours until the solution is clear and transparent, and a bright yellow mother liquor is obtained. As the temperature rises and the reaction proceeds, the undissolved white GeO2 powder at the bottom gradually disappears, and the solution gradually changes from the initial turbid state to a clear, transparent, bright yellow mother liquor. 4. Controlled Crystallization (Slow Cooling Method): After confirming that the solution is absolutely clear and free of undissolved solids, tightly seal the reaction vessel containing the mother liquor and quickly and steadily place it in a high-precision programmable temperature control chamber preheated to 90 ℃. Set the cooling program curve: starting temperature approximately 90 ℃, and continuously cooling at an ultra-low constant cooling rate of 1 ℃ / h (i.e., 1 K / h) for approximately 65 hours to reduce the system temperature to room temperature (approximately 25 ℃). In this step, an oven can be used instead of the high-precision programmable temperature control chamber. 5. Product Collection and Post-processing: After the cooling process, the reaction flask was removed, and a large number of white transparent single crystals were observed to have precipitated at the bottom and on the walls. The upper mother liquor was poured off, and the crystals were separated by vacuum filtration. The residual acid on the crystal surface was then quickly washed 2-3 times with a small amount of diethyl ether. Finally, the crystals were dried in a 60 ℃ vacuum drying oven to constant weight, yielding high-purity, high-crystallinity (…). R -THNA)GeI3 single crystal material.

[0051] The three-dimensional configuration has symmetry, which allows the organic precursors in the above steps to be combined. R -THNA is replaced with moles of 1 / 2 THNA S -THNA enantiomers, using the exact same operating and cooling parameters, yield enantiomers with opposite chiral directions. (S -THNA)GeI3 single crystal material.

[0052] Example 2 This embodiment provides a method for growing germanium halide single crystals in a pure bromine system using a slow cooling method. R / S The specific process steps and preparation method of (-THNA)GeBr3) are basically the same as those in Example 1, with the only difference being: In step 1, the volume of the glass reaction flask is 20 mL; In step 2, the mixed acid is prepared by mixing a 48% hydrobromic acid aqueous solution (HBr) and a 37% hypophosphoric acid aqueous solution (H3PO2) in a volume ratio of 3:1. In this step, 10 mL of hydrobromic acid aqueous solution and 3 mL of hypophosphoric acid aqueous solution are slowly added dropwise using a pipette. The three-dimensional configuration has symmetry, and the above... R -THNA is replaced with equimolar S -THNA, the same steps can be used to obtain the enantiomer ( S -THNA)GeBr3 single crystal material.

[0053] The crystal structures of the four germanium halide single crystals in Examples 1 and 2 were confirmed by X-ray single-crystal diffraction. Figure 1 As shown, 1 represents a germanium atom, 2 represents a carbon atom, 3 represents an iodine atom, and 4 represents a bromine atom. It can be seen that the lattice stress of a sterically hindered organic cation is related to the 4s² lattice stress of the germanium ion. 2 Under the synergistic effect of lone pairs of electrons, all four single crystals have non-centrosymmetric molecular structures. Germanium atoms form chemical bonds with only three halide anions, forming a discretely distributed polar trigonal pyramidal structure.

[0054] Example 3 This embodiment provides a method for growing germanium halide crystals in a mixed halogen system using a slow cooling method. R -THNA)GeI 1.75 Br 1.25 The specific process steps include: Step 1: Following steps 1-3 of Example 1, provide the mother liquor as I-liquid; following steps 1-3 of Example 2, provide the mother liquor as Br-liquid; Step 2, precise volume mixing: Under constant temperature stirring conditions at 90 ℃, use a preheated pipette to measure the prepared I-liquid and Br-liquid and transfer them into the same constant temperature reaction vessel at a volume ratio of 0.5:1. Step 3, Homogenization reaction: Stir vigorously with a magnetic force at 90 °C for about 1 hour to allow the iodine- and bromine-based germanium complexes to undergo sufficient ligand exchange and homogenization at the molecular level, forming a single homogeneous, clear, bright yellow mixed mother liquor. Step 4, Co-crystallization growth: Seal the reaction vessel containing the mixed mother liquor and immediately place it in a programmed cooling device, continuing to control the nucleation rate at an extremely low rate: slowly and steadily cool from 90 ℃ to room temperature at a cooling rate of 1 ℃ / h (i.e. 1 K / h). 5. Product Acquisition: The large transparent single crystals precipitated at the bottom were collected by filtration and subjected to the same washing and drying process as in Example 1 to obtain the target mixed halogen crystals. R -THNA)GeI 1.75 Br 1.25 .

[0055] Examples 4-8 This series of embodiments provides a series of mixed halogen crystals ( R -THNA)GeI x Br 3-x The preparation method involves adjusting the mixing ratio of I-liquid and Br-liquid to prepare a series of mixed halogen crystals. The preparation method is the same as in Example 3, except that the volume ratio of I-liquid to Br-liquid in step two is as shown below. The actual elemental composition of each crystal is supported by XRF test results: 1) When the volume ratio of I-liquid / Br-liquid is 1 / 1, the XRF measured I / Br ratio of the obtained crystal is 8.01259; 2) When the volume ratio of I-liquid / Br-liquid is 1.2 / 1, the XRF measured I / Br ratio of the obtained crystal is 9.48662; 3) When the volume ratio of I-liquid to Br-liquid is 2 / 1, the XRF measured I / Br ratio of the obtained crystal is 18.01487; 4) When the volume ratio of I-liquid / Br-liquid is 3 / 1, the XRF measured I / Br ratio of the obtained crystal is 26.48394 (which is close to the pure iodine phase boundary). 5) When the ratio of I-liquid to Br-liquid precursor is 1 / 3, the XRF measured I / Br ratio of the resulting crystal is 0.50105.

[0056] PXRD of each single crystal (R-type) in Examples 1-3 are as follows: Figure 2 As shown, the spectra of each embodiment are free of impurity peaks, indicating good crystal quality and high purity. The halogen ratio I / Br of each single crystal in Examples 1 to 8, measured by X-ray fluorescence spectroscopy (XRF), is shown in Table 1.

[0057] Table 1. Halogen ratios of single crystals in Examples 1-8 as measured by X-ray fluorescence spectroscopy (XRF). It can be seen that iodide ions (I - ) and bromide ions (Br - All of these readily enter the lattice of this hybrid system. In Example 3, the actual iodine / bromine atom ratio (I / Br) is 1.49087 (approximately 1.5), corresponding to the chemical formula (…). R -THNA)GeI 1.75 Br 1.25As can be seen from Table 1, the I-liquid / Br-liquid volume ratio is not equal to the I / Br ratio of the final lattice precipitate product. By continuously adjusting the precursor feed ratio, the doping ratio of iodine and bromine in the crystal can be precisely controlled, thus achieving control over (…). R -THNA)GeI x Br 3-x (0 ≤ x ≤ 3) Continuous control of components and their nonlinear optical properties.

[0058] Structural and performance evaluation Example 2: Germanium halide single crystal in pure bromine system (( R -THNA)GeBr3 or ( S -THNA)GeBr3) macroscopic single crystals can reach centimeter-scale size, with well-developed crystal faces and high surface optical smoothness. Observation under a polarizing microscope, such as... Figure 3 As shown, crystals with different intersection angles exhibit periodic changes in brightness under different rotation angles, and no obvious macroscopic cracks, bubbles, solvent inclusions, or other optical defects are observed inside the crystals.

[0059] To verify the nonlinear optical properties of the chiral organic-inorganic hybrid germanium halide crystals prepared in this invention, a femtosecond laser device was used to systematically test the single crystals and reference standards of the above embodiments and comparative examples. The specific test conditions and verification steps are as follows: 1. Test instrument and optical configuration setup A commercial femtosecond laser (model: Mai Tai HP) was used as the excitation source, with a wavelength tuning range of 690~1040 nm, a pulse width of about 100 fs, and a repetition frequency of 80 MHz.

[0060] The test employed a reflection mode configuration: both the incident angle of the laser and the collection angle of the SHG signal were fixed at 45°, and the optical path was as follows: Figure 4 As shown, SHG response data is obtained by detecting the signal reflected from the front surface of the crystal, and the results are as follows. Figure 5 As shown in the figure. Using KDP (potassium dihydrogen phosphate, KH2PO4) high-purity optical-grade crystal powder—the most authoritative and widely used commercial nonlinear optics benchmark material recognized in the industry—as the absolute standard reference, the single crystals of each embodiment were compared with this KDP standard reference material under an extremely fair environment without changing any optical path environment or adjusting any detector sensitivity gain. The SHG response data (the multiples of the SHG response intensity of the reference KDP crystal) for Examples 1-8 are summarized in Table 2.

[0061] Test results show that, at various excitation wavelengths, the overtone response signal intensity excited by the single crystal in the example is significantly higher than that of KDP. When the excitation wavelength is tuned to 1020 nm, by quantitatively comparing the intensity of the collected front surface reflected SHG signal, the intensity of the pure iodine single crystal ( R The overtone response signal intensity excited by GeI3 (Example 1) was 14.2 times that of the KDP crystal; while the specific ratio of mixed halogen crystals obtained through component control ( R -THNA)GeI 1.75 Br 1.25 (Example 3) The overtone response intensity excited by it reached 23.6 times that of the reference KDP crystal. The overtone response intensity excited by the mixed halogen crystals in Examples 4-8 was 0.1-7 times that of the reference KDP crystal, which is significantly lower than that of Example 3. R -THNA)GeI 1.75 Br 1.25 .

[0062] Table 2 SHG response data for Examples 1-8 Figure 6 The dispersive spectra of the frequency-dependent SHG coefficients of each embodiment as a function of photon energy are shown in the near-infrared to visible light range of 0-2 eV. Embodiments 1-3 all exhibit nonlinear responses, with Embodiment 3 showing a significant nonlinear resonance enhancement effect. It is evident that mixed halogen crystals ( R -THNA)GeI 1.75 Br 1.25 Due to the presence of a specific ratio of halogens, the lattice distortion and polarizability achieve the most perfect balance.

[0063] 2. Polarization dependence test Linear polarization dependence: A half-wave plate (λ / 2 plate) was introduced into the optical path. By rotating the half-wave plate in 10° increments, the changes in the SHG signal at different polarization angles were recorded to verify the anisotropy of the crystal's macroscopic polarizability. The results are as follows: Figure 7 As shown, it can be seen that it conforms to cos 4 The characteristic dumbbell-shaped pattern of the θ function confirms the dipole nature of the NLO response.

[0064] 3. Determination of Laser-Induced Damage Threshold (LDT) The resistance of crystals to optical damage is a crucial indicator for the practical application of nonlinear optical materials. This invention defines and calculates the laser-induced damage threshold (LDT) using the following formula: LDT = P (F × πr 2 )-1 In the formula: • P represents the critical damaging incident power (when the curve of SHG signal intensity changing with power begins to deviate from the quadratic dependence, it is determined that the crystal structure is damaged, and the corresponding power is the critical power P). • F represents the laser emission time characteristic frequency (using the laser's repetitive emission frequency, which is a constant of 80 MHz in this test); •r represents the radius of the laser spot at the laser focus (measured by microscopic optical path, the diameter of the circular laser spot focused on the crystal surface in this experiment is about 20 μm, i.e., r ≈ 10 μm).

[0065] The results are as follows Figure 8 As shown, the laser damage thresholds for Example 1 and Example 2 are 1.08 and 1.71 GW·cm, respectively. -2 It can be seen that the hybrid crystal material of the present invention has good optical stability and damage resistance under strong laser irradiation.

[0066] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material, comprising an organic component and an inorganic component, wherein the inorganic component is germanium and a halogen, characterized in that, The organic component is a chiral 1,2,3,4-tetrahydro-1-naphthylamine cation, with the general chemical formula ( R / S -THNA)GeX3, where R / S -THAN represents the chiral 1,2,3,4-tetrahydro-1-naphthylamine cation, Ge represents divalent germanium ion, and X represents halide anion; The chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material crystallizes in the chiral space group. P2 1. It has a non-centrosymmetric molecular structure; the inorganic component has a polar trigonal pyramidal configuration, and the polar trigonal pyramids are discretely distributed.

2. The chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material according to claim 1, characterized in that, In the polar trigonal pyramidal configuration, germanium ions form chemical bonds with three halide ions.

3. The chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material according to claim 1, characterized in that, The halide anion is a bromide ion and / or an iodide ion.

4. The chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material according to claim 3, characterized in that, The halogen anions are bromide ions and iodide ions.

5. The chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material according to claim 4, characterized in that, The general chemical formula of the chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material is ( R / S -THNA)GeI x Br 3-x , where 0 < x < 3.

6. A method for preparing a chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Germanium dioxide and chiral 1,2,3,4-tetrahydro-1-naphthylamine were mixed with hypophosphoric acid solution and hydrohalic acid solution, and heated and stirred until the solution became clear to obtain the precursor solution. A chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material was obtained by a slow cooling crystallization method.

7. The preparation method according to claim 6, characterized in that, The molar ratio of germanium dioxide to chiral 1,2,3,4-tetrahydro-1-naphthylamine is 1:2; and / or the volume ratio of the hydrohalic acid solution to the hypophosphite solution is 1~3:1, the mass percentage of the hypophosphite solution is 37%, and the mass percentage of the hydrohalic acid solution is 45~60%.

8. The preparation method according to claim 6, characterized in that, The hydrohalic acid solution is a hydrobromic acid solution and a hydroiodic acid solution.

9. The preparation method according to claim 6, characterized in that, In the slow cooling crystallization method, the cooling rate is 0.5~2 ℃ / h, and the cooling range is from 80~100 ℃ to room temperature.

10. The application of a chiral organic-inorganic hybrid germanium halide nonlinear optical crystal material as described in any one of claims 1 to 5 as a second harmonic generation material in laser frequency conversion devices in the field of nonlinear optics.

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