Design and performance optimization method of silicic acid gallium lanthanum nonlinear optical crystal

Abstract

The invention relates to the technical field of crystal material design and modification, in particular to a design and performance optimization method of a silicic acid gallium lanthanum nonlinear optical crystal. According to the invention, Ti ions are introduced into a lanthanum gallium silicate family crystal to replace M < 5 + > and Ga < 3 + > ions in the lanthanum gallium silicate family La3M0. 5Ga5. 5O14 crystal, so that the lanthanum gallium titanate La3TiGa5O14 crystal is obtained; carrying out annealing treatment at 900-1400 DEG C in an oxygen atmosphere so as to oxidize Ti < 3 + > ions in the lanthanum gallium titanate crystals into Ti < 4 + > ions and reduce oxygen vacancy defects in the crystals; and cooling the crystal to room temperature to obtain the annealed lanthanum gallium titanate crystal. According to the method, the lanthanum gallium titanate crystal is annealed under the oxygen atmosphere, so that the concentration of Ti < 3 + > is reduced, oxygen vacancies are reduced or even eliminated, the optical performance is remarkably improved, and the performance defects of the LGTi crystal caused by Ti valence change and oxygen vacancies are effectively overcome.

Description

Technical Field

[0001] This invention relates to the field of crystal material design and modification technology, specifically to a method for designing and optimizing the performance of a lanthanum gallium silicate nonlinear optical crystal. Background Technology

[0002] Lanthanum gallium silicate crystals are an important class of functional crystal materials, with the general structural formula A3BC3D2O. 14 Its structure contains four different polyhedral groups: AO8 dodecahedron, BO6 octahedron, CO4 tetrahedron, and DO4 tetrahedron. Lanthanum gallium silicate crystals are widely used in surface acoustic wave devices, sensors, and frequency conversion elements in all-solid-state lasers due to their excellent piezoelectric, electro-optic, and nonlinear optical properties.

[0003] Lanthanum gallium niobate, a member of the lanthanum gallium silicate group, has proven its important application in nonlinear frequency conversion devices. However, existing research shows that the inherent cation position disorder at different lattice sites in lanthanum gallium silicate crystals often leads to the presence of residual oxygen vacancies. These oxygen vacancies, due to their high formation energy and low mobility in the lattice, are difficult to completely eliminate through conventional methods, thus hindering the full realization of the material's inherent properties. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for designing and optimizing the performance of lanthanum gallium silicate nonlinear optical crystals. This invention introduces Ti... 4+ By precisely controlling the oxygen annealing process, optimizing its nonlinear optical coefficient, and significantly improving its laser damage threshold, the problem of residual oxygen vacancies caused by the inherent cation position disorder in different lattice sites of gallium gallium silicate lanthanum group crystals was solved.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows.

[0006] This invention provides a method for designing and optimizing the performance of lanthanum gallium silicate nonlinear optical crystals, comprising the following steps: A lanthanum gallium silicate crystal is provided, wherein the lanthanum gallium silicate crystal is La3M. 0.5 Ga 5.5 O 14 Crystal, where M is Nb 5+ Or Ta 5+ ; through La3M 0.5 Ga 5.5 O 14 By introducing tetravalent Ti ions into the crystal to replace pentavalent Nb / Ta ions and trivalent Ga ions, the intrinsic oxygen vacancy defects are reduced, resulting in lanthanum gallium titanate crystals; the chemical formula of lanthanum gallium titanate crystals is La3TiGa5O. 14.

[0007] Lanthanum gallium titanate crystals were annealed at 900℃~1400℃ in an oxygen atmosphere to remove the Ti in the lanthanum gallium titanate crystals. 3+ Ion oxidation to Ti 4+ After cooling the ions to room temperature, lanthanum gallium titanate crystals with oxygen defects were obtained.

[0008] Based on La3M 0.5 Ga 5.5 O 14 The charge mismatch between pentavalent M ions and trivalent Ga ions in the crystal is Δ=+2, leading to more charge-compensating oxygen defects related to heterovalent disorder, resulting in deterioration of crystal performance. This invention addresses this by introducing Ti into the lanthanum gallium silicate crystal. 4+ The goal is to minimize the formation of oxygen vacancies. However, lanthanum gallium titanate crystals grown under oxygen-deficient conditions will exhibit a small amount of Ti ions. 4+ Ions are reduced to Ti 3+ A small amount of Ti 3+ The presence of ions and oxygen defects will degrade crystal properties, such as transmittance and damage threshold. In lanthanum gallium titanate crystals before annealing, Ti... 3+ There is absorption in the blue-green light band of 400nm to 500nm, which leads to a rapid decrease in transmittance.

[0009] Ti in lanthanum gallium titanate crystals 3+ Ions introduce oxygen vacancies, affecting the optical properties of crystals. This invention addresses this issue by annealing lanthanum gallium titanate crystals in an oxygen atmosphere to reduce the TiO2 content. 3+ Concentration, reducing oxygen vacancies, thereby reducing the concentration of Ti 3+ The intrinsic absorption induced by annealing increases the transmittance of the crystal in the visible and near-infrared bands, significantly improving the laser damage resistance of lanthanum gallium silicate crystals. Simultaneously, the regularization of the Ti valence state improves the electron cloud distribution and micro-polarization environment of the lanthanum gallium silicate crystal, optimizing its macroscopic nonlinear optical coefficients. In the annealed lanthanum gallium titanate crystal, the absorption of blue and green light is significantly reduced, and the transmittance is significantly increased. Furthermore, the transmittance in the ultraviolet band is significantly improved.

[0010] Preferably, the TiO2 crystal of lanthanum gallium titanate before annealing treatment. 3+ The absorption band is in the blue-green light band of 400nm to 500nm; the oxygen vacancy absorption band of the lanthanum gallium titanate crystal before annealing is in the ultraviolet band of 300nm to 400nm.

[0011] Preferably, the annealing time is 10h to 100h.

[0012] Preferably, the specific steps of the annealing process are as follows: Lanthanum gallium titanate crystals were heated to 900℃–1400℃ at a rate of 10℃ / h–120℃ / h under an oxygen atmosphere, annealed at 900℃–1400℃ for 10h–100h, and then cooled to below 200℃ at a rate of 10℃ / h–100℃ / h, followed by furnace cooling to room temperature, to obtain annealed lanthanum gallium titanate crystals. The purpose of this annealing treatment is to reduce the Ti content in the lanthanum gallium titanate crystals. 3+ -V O Composite defects.

[0013] The objective of this invention is to maximize the yield of La3TiGa5O 14 Ti in crystals 3+ Ions transform into Ti 4+ Reduce the presence of Ti in the crystal 3+ - V O Defective complexes. By controlling the temperature and time of the annealing treatment, the valence state conversion of Ti ions can be better achieved.

[0014] Preferably, the oxygen atmosphere for the annealing treatment is oxygen with a purity of 99.99% and an oxygen flow rate of 50 sccm.

[0015] In the lanthanum gallium titanate crystal before annealing, Ti 3+ The presence of Ti causes a rapid decrease in the transmittance of lanthanum gallium titanate crystals in the blue-green light band. Annealed lanthanum gallium titanate crystals show a significant increase in transmittance in both the ultraviolet and blue-green light bands, indicating that the presence of Ti in the lanthanum gallium titanate crystal... 3+ -V O The defect complex was reduced.

[0016] Preferably, the chemical formula of the lanthanum gallium titanate crystal is La3TiGa5O. 14 .

[0017] Preferably, the preparation method of lanthanum gallium titanate crystal is as follows: La2O3, TiO2 and Ga2O3 are used as raw materials. They are mixed, pressed into blocks, and sintered into polycrystalline materials. The polycrystalline materials are melted to form a melt. Lanthanum gallium titanate seed crystals are added to the melt, and single crystals are grown by the Czochralski method. After in-situ annealing and cooling, lanthanum gallium titanate crystals are obtained.

[0018] Preferably, the melting of the polycrystalline material is carried out under oxygen-deficient conditions; the oxygen-deficient conditions are: a mixed gas with an oxygen volume content of 0.5% to 2%.

[0019] It should be noted that during high-temperature growth under air conditions, iridium in the iridium crucible is prone to volatilization, while the growth of gallium lanthanum titanate crystals requires a certain oxygen environment. Therefore, in order to ensure the quality of gallium lanthanum titanate crystals during the growth process, the volume content of oxygen in the protective atmosphere is controlled at 0.5% to 2%.

[0020] In this invention, the method for preparing lanthanum gallium titanate crystals is under oxygen-deficient conditions using La3M... 0.5 Ga 5.5 O 14 Crystal as matrix, with Ti 4+ The ion source is a doped ion source, obtained through La3M 0.5 Ga 5.5 O 14 By introducing tetravalent Ti ions into the crystal to replace pentavalent Nb / Ta ions and trivalent Ga ions, the intrinsic oxygen vacancy defects are reduced, resulting in lanthanum gallium titanate crystal.

[0021] Preferably, the gallium lanthanum titanate seed crystal is a

[001] oriented gallium lanthanum titanate seed crystal.

[0022] Preferably, the molar ratio of La2O3, TiO2 and Ga2O3 is 3:1:4.9 to 5.

[0023] Preferably, the parameters for melting the chemical are: temperature of 1510℃~1520℃ and time of 4h~8h.

[0024] Preferably, the control conditions for growing single crystals using the Czochralski method are: a pulling rate of 0.4 mm / h to 0.8 mm / h and a rotation rate of 5 rpm to 8 rpm. In this invention, the method for growing single crystals using the Czochralski method is as follows: a lanthanum gallium titanate seed crystal is pulled and rotated simultaneously, with the pulling rate controlled at 0.4 mm / h to 0.8 mm / h and the rotation rate at 5 rpm to 8 rpm, allowing the single crystal to grow at a constant diameter until the single crystal diameter reaches the target size. The target single crystal diameter is 20 mm to 50 mm.

[0025] Preferably, the cooling operation after in-situ annealing is as follows: after the single crystal grown to the target size is removed from the melt surface, it is cooled to 1100℃~1200℃ and in-situ annealed at 1100℃~1200℃ for 5h~15h, then cooled to room temperature in the furnace to obtain lanthanum gallium titanate crystal. The purpose of in-situ annealing here is to prevent cracking of the lanthanum gallium titanate crystal.

[0026] The beneficial effects of this invention are: 1. This invention utilizes lanthanum gallium silicate crystal La3M 0.5 Ga 5.5 O 14By introducing tetravalent Ti ions into the crystal to replace pentavalent Nb / Ta ions and trivalent Ga ions, intrinsic oxygen vacancy defects are reduced, yielding lanthanum gallium titanate La3TiGa5O. 14 Crystal. Then, an annealing process is used to remove the small amount of Ti that was generated during the growth of the lanthanum gallium titanate crystal. 3+ Transform into Ti as much as possible 4 + By reducing or even eliminating oxygen vacancies, optical performance is significantly improved.

[0027] 2. This invention can reduce Ti through annealing treatment technology. 3+ Concentration, reducing oxygen vacancies, thereby reducing the concentration of Ti 3+ The intrinsic absorption caused by this process increases the transmittance of annealed lanthanum gallium titanate crystals in the ultraviolet to visible wavelength range.

[0028] 3. The reduction in absorption centers in this invention means that less energy is absorbed and converted into heat under strong laser irradiation, thereby significantly improving the laser damage resistance of annealed lanthanum gallium titanate crystals. Experiments show that the laser damage threshold of the annealed lanthanum gallium titanate crystals obtained after the annealing treatment of this invention can be increased by more than two times.

[0029] 4. This invention improves the electron cloud distribution and micro-polarization environment of lanthanum gallium titanate crystal by regularizing the Ti valence state, thereby optimizing the macroscopic nonlinear optical coefficient of the annealed lanthanum gallium titanate crystal. Attached Figure Description

[0030] Figure 1 This is a comparison of the ultraviolet-visible-near-infrared transmission spectra and infrared transmission spectra of lanthanum gallium titanate crystals before and after annealing in Example 1. In Figure a, there is a comparison of the ultraviolet-visible-near-infrared transmission spectra of the lanthanum gallium titanate crystals before and after annealing; the inset in Figure a is a magnified view of a portion of Figure a from 250 nm to 550 nm; and Figure b is a comparison of the infrared transmission spectra of the lanthanum gallium titanate crystals before and after annealing.

[0031] Figure 2 This is a comparison chart of the laser damage thresholds of the lanthanum gallium titanate crystal before and after annealing in Example 1.

[0032] Figure 3 This is a comparison diagram of the nonlinear coefficients of the lanthanum gallium titanate crystal before and after annealing in Example 1. In the diagram, a represents the nonlinear coefficient of the lanthanum gallium titanate crystal before annealing; b represents the nonlinear coefficient of the lanthanum gallium titanate crystal after annealing. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Based on lanthanum gallium silicate crystals, suppressing or even eliminating oxygen vacancies is an important way to improve the performance of this group of crystals, which is beneficial to further enhance their important applications in fields such as nonlinear frequency conversion.

[0036] The general structural formula of lanthanum gallium silicate crystals is A3BC3D2O 14 In this case, position A is usually represented by La. 3+ 、Nd 3+ and Pr 3+ Lanthanides or Y 3+ Large-radius trivalent cations occupy the B site, with a coordination number of 8, forming a twisted AO8 dodecahedron; medium-radius cations mainly occupy the B site, with a coordination number of 6, forming a BO6 octahedron; small-radius cations typically occupy the C site, with a coordination number of 4, forming a CO4 tetrahedron; and the D site has a coordination number of 4, forming a DO4 tetrahedron. The occupancy of the B, C, and D sites is mainly related to the ionic radius.

[0037] This invention introduces Ti into lanthanum gallium silicate crystals. 4+ Ions, Ti 4+ The ionic radius is r≈0.61Å, and the coordination number is CN=6; the cation Ga 3+ The ionic radius is r≈0.62 Å, and the coordination number is CN=6. This indicates that Ti... 4+ The ionic radius of the Ga cation 3+ The ionic radii are very close, which can minimize the formation of lattice defects.

[0038] However, during the Czochralski crystal growth process, due to the high temperature and the complexity of the crystal chemical environment, a small number of Ti ions may exist in the +3 valence state instead of the ideal +4 valence state. 3+ The presence of ions can bring about a series of problems, for example, Ti 3+ The presence of ions introduces optical absorption, specifically: Ti 3+ The presence of oxygen vacancies in lanthanum gallium titanate crystals can lead to oxygen vacancies, which may generate oxygen in the visible and near-infrared bands. d - d Transition absorption increases the optical loss of lanthanum gallium titanate crystals and reduces light transmittance.

[0039] Ti3+ As absorption centers, the presence of absorption centers makes lanthanum gallium titanate crystals more susceptible to local thermal effects and electron avalanche ionization under strong laser irradiation, resulting in optical damage and manifested as a reduction in the laser damage threshold.

[0040] Furthermore, the valence state and occupancy of Ti ions directly affect the electronic structure and frequency doubling polarization of lanthanum gallium titanate crystals. Non-ideal Ti ions... 3+ This may result in the macroscopic nonlinear optical coefficient of the gallium lanthanum titanate crystal not reaching its optimal value.

[0041] This invention introduces Ti 4+ Ions, reducing the formation of lattice defects, were designed to form La3TiGa5O 14 The crystal, denoted as LGTi crystal. This refers to the Ti crystal found in lanthanum gallium titanate crystals. 3+ This invention addresses the problem of oxygen vacancies introduced by ions affecting the optical properties of lanthanum gallium titanate (LGaTi) crystals. It provides a simple and effective post-processing method for LGaTi crystals to reduce oxygen vacancies. The invention utilizes an annealing process to successfully reduce some of the oxygen vacancies in LGaTi crystals. 3+ Ion oxidation to Ti 4+ This reduces oxygen defects in lanthanum gallium titanate crystals, ultimately leading to a significant improvement in the optical performance of lanthanum gallium titanate crystals.

[0042] This invention provides a method for introducing Ti into a lanthanum gallium silicate crystal. 4+ Ions, designed to become La3TiGa5O 14 Crystallization, reducing the generation of inherent crystal defects, specifically targeting the Ti-related defects in grown lanthanum gallium titanate crystals. 3+ The present invention addresses issues such as high optical absorption, low damage threshold, and suboptimal nonlinear coefficient in lanthanum gallium titanate (LGaTi) crystals. Annealing this LGaTi crystal significantly improves its optical performance. This invention offers a simple process, remarkable results, and the optimized LGaTi crystal design is particularly suitable for high-power nonlinear optical devices.

[0043] In the following embodiments of the present invention, the method for preparing the lanthanum gallium titanate crystal in step 1 is as follows: Using La2O3, TiO2, and Ga2O3 as raw materials, with a molar ratio of 3:1:4.9 to 5, the raw materials are mixed, pressed into blocks, and sintered. The mixture is then placed in a Φ70mm iridium crucible and placed in a single crystal furnace. After evacuation, a N2 mixed gas containing 0.5% to 2% O2 is introduced to atmospheric pressure. The temperature is then raised to 1510℃ to 1520℃ and held for 4 to 8 hours to allow the raw materials to fully melt and form a melt.

[0044] A

[001] -oriented lanthanum gallium titanate seed crystal was placed into the homogenized melt. After reaching thermal equilibrium, the temperature was slowly increased by 10℃ to 15℃ over 30 minutes to eliminate LaGaO3 impurities accumulated at the top of the seed crystal. The temperature was held for 30 minutes, and then the temperature was immediately and rapidly decreased by 15℃ to 20℃ for pulling. The pulling rate was controlled at 0.8 mm / h, and the crystal rotation rate was 6 rpm. After pulling for 3 hours, shoulder formation and constant diameter growth were performed, with the pulling rate controlled at 0.4 mm / h to 0.8 mm / h and the crystal rotation rate controlled at 5 rpm to 8 rpm.

[0045] After growth, the single crystal grown to the target size is lifted from the melt surface and cooled to 1100℃~1200℃ at a rate of 20℃ / h~50℃ / h. It is then annealed in situ at 1100℃~1200℃ for 5h~15h, and finally cooled in the furnace to room temperature for 36h~48h to obtain the lanthanum gallium titanate crystal before annealing.

[0046] Although the present invention is illustrated by the following embodiments, the amounts of each raw material and the ranges of preparation conditions in the design and performance optimization method for lanthanum gallium silicate nonlinear optical crystals provided by the present invention can all be within the above-mentioned ranges. Lanthanum gallium titanate crystals can be prepared using the above-mentioned amounts of raw materials and preparation conditions.

[0047] The technical solution of the present invention will be further described below through specific embodiments. Unless otherwise specified, the methods described in the following embodiments are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0048] Example 1 A method for designing and optimizing the performance of a lanthanum gallium silicate nonlinear optical crystal includes the following steps: Step 1, the chemical formula of lanthanum gallium niobate crystal is La3Nb 0.5 Ga 5.5 O 14 ; through lanthanum gallium niobate La3Nb 0.5 Ga 5.5 O 14 Introducing Ti into the crystal 4+ By replacing pentavalent Nb / Ta ions and trivalent Ga ions, intrinsic oxygen defects are reduced, yielding lanthanum gallium titanate crystals with the chemical formula La3TiGa5O. 14 , denoted as LGTi.

[0049] The preparation method of lanthanum gallium titanate crystal is as follows: using La2O3, TiO2 and Ga2O3 as raw materials, with a molar ratio of La2O3, TiO2 and Ga2O3 of 3:1:5, the raw materials are mixed, pressed into blocks and sintered, and then placed in an iridium crucible with a diameter of 70 mm and placed in a single crystal furnace; after evacuation, a N2 mixed gas containing 1% O2 is introduced to atmospheric pressure; the temperature is raised to 1520℃ and held for 8 hours to allow the raw materials to fully melt and form a melt.

[0050] A

[001] -oriented lanthanum gallium titanate seed crystal was placed into the homogenized melt. After reaching thermal equilibrium, the temperature was slowly increased by 10°C over 30 minutes to eliminate LaGaO3 impurities accumulated at the top of the seed crystal. The temperature was held for 30 minutes, and then immediately and rapidly cooled by 15°C for pulling. The pulling rate was controlled at 0.8 mm / h, and the crystal rotation rate was 6 rpm. After pulling for 3 hours, shoulder formation and constant diameter growth were performed, with the pulling rate controlled at 0.5 mm / h and the crystal rotation rate at 5 rpm. After growth, the single crystal grown to the target size was lifted from the melt surface and cooled to 1200°C at a rate of 20°C / h. In-situ annealing was performed at 1200°C for 10 hours, and finally, the crystal was cooled in the furnace to room temperature for 48 hours to obtain the lanthanum gallium titanate crystal.

[0051] Step 2: Under an oxygen atmosphere, the lanthanum gallium titanate crystal is annealed at 1400℃ for 48 hours to allow the Ti in the lanthanum gallium titanate crystal to be absorbed. 3+ Ion oxidation to Ti 4+ The ions were cooled to room temperature to obtain annealed lanthanum gallium titanate crystals. The preparation method for lanthanum gallium titanate crystals with oxygen defects eliminated is as follows:

[0052] Take a piece of lanthanum gallium titanate crystal obtained by the Czochralski method and

[001] orientation in step 1, and process it into a size of 10×10×1mm. 3 The optical components were polished on both sides. The polished samples were placed in a high-temperature tubular annealing furnace, sealed, and purged with 99.99% pure oxygen at a flow rate of 50 sccm for 20 minutes to remove air from the furnace. Then, the furnace temperature was increased from room temperature to 1400℃ at a rate of 120℃ / h, and annealed at 1400℃ for 48 hours with continuous oxygen purging. After annealing, the temperature was slowly reduced to below 200℃ at a rate of 60℃ / h, and then cooled to room temperature with the furnace. The samples were then removed, yielding annealed lanthanum gallium titanate crystals.

[0053] The performance of the lanthanum gallium titanate crystals prepared in Example 1 before and after annealing was tested. It should be noted that the lanthanum gallium titanate crystal before annealing is the lanthanum gallium titanate crystal obtained in step 1; the lanthanum gallium titanate crystal after annealing is the lanthanum gallium titanate crystal with oxygen defects eliminated in step 2.

[0054] Comparing the UV-Vis-NIR transmission spectra of lanthanum gallium titanate crystals before and after annealing, the results are as follows: Figure 1 As shown.

[0055] Figure 1 This is a comparison of the UV-Vis-NIR transmission spectra and infrared transmission spectra of lanthanum gallium titanate crystals before and after annealing in Example 1. In Figure a, there is a comparison of the UV-Vis-NIR transmission spectra of the lanthanum gallium titanate crystals before and after annealing; the inset in Figure a is a magnified view of a portion of Figure a from 250 nm to 550 nm; Figure b is a comparison of the infrared transmission spectra of the lanthanum gallium titanate crystals before and after annealing. The wavelength range of 400 nm to 500 nm is the blue-green light band. Figure 1 In the image, "before treatment" refers to the lanthanum gallium titanate crystal before annealing; "after treatment" refers to the lanthanum gallium titanate crystal after annealing.

[0056] Depend on Figure 1 The results show that the absorption band of the lanthanum gallium titanate crystal before annealing is in the blue-green light band of 400 nm to 500 nm. Because the lanthanum gallium titanate crystal is grown under oxygen-deficient conditions, a small amount of Ti... 4+ Ions are reduced to Ti 3+ A small amount of Ti 3+ The presence of ions and oxygen defects will degrade crystal properties, such as transmittance and damage threshold. Figure 1 As shown in Figure a, in the lanthanum gallium titanate crystal before annealing, Ti 3+ There is absorption in the blue-green light band of 400nm to 500nm, which leads to a rapid decrease in transmittance.

[0057] In the annealed lanthanum gallium titanate crystal, the absorption in the 400nm–500nm blue-green light band is significantly reduced, while the transmittance in this band is significantly increased. Furthermore, the 300nm–400nm band is the oxygen vacancy absorption band. The absorption peak at 338nm is eliminated in the annealed lanthanum gallium titanate crystal, indicating a reduction in oxygen vacancies and increased transmittance. The absorption peak near 4280nm is completely eliminated. This absorption peak near 4280nm is caused by hydroxyl groups.

[0058] The above analysis results show that, in Example 1 of the present invention, annealing lanthanum gallium titanate crystals under an oxygen atmosphere can reduce the Ti... 3+ Concentration, reducing oxygen vacancies, thereby reducing the concentration of Ti 3+ The intrinsic absorption caused by this process increases the transmittance of lanthanum gallium silicate crystals in the visible to near-infrared bands, significantly improving the laser damage resistance of lanthanum gallium silicate crystals.

[0059] Laser damage threshold testing was performed using a 1064nm Nd:YAG laser with a pulse width of 10ns and a frequency of 1Hz. The results are as follows: Figure 2 As shown.

[0060] Figure 2 This is a comparison chart of the laser damage thresholds of the lanthanum gallium titanate crystal before and after annealing in Example 1. Figure 2 In the image, "before treatment" refers to the lanthanum gallium titanate crystal before annealing; "after treatment" refers to the lanthanum gallium titanate crystal after annealing.

[0061] Figure 2 The results show that the laser damage threshold of the lanthanum gallium titanate crystal before annealing is 1.20 GW / cm. 2 The laser damage threshold of the annealed lanthanum gallium titanate crystal is 2.53 GW / cm². 2 Compared to the laser damage threshold of lanthanum gallium titanate crystals before annealing, the laser damage threshold of lanthanum gallium titanate crystals after annealing is improved.

[0062] This demonstrates that, according to Embodiment 1 of the present invention, annealing gallium lanthanum titanate crystals under an oxygen atmosphere can significantly improve the laser damage resistance of gallium lanthanum silicate crystals.

[0063] The nonlinear coefficients under type I phase matching were measured using the Maker fringe method, and the results are as follows: Figure 3 As shown.

[0064] Figure 3 This is a comparison diagram of the nonlinear coefficients of the lanthanum gallium titanate crystal before and after annealing in Example 1. In the diagram, a represents the nonlinear coefficient of the lanthanum gallium titanate crystal before annealing; b represents the nonlinear coefficient of the lanthanum gallium titanate crystal after annealing. Figure 3 In the image, "before treatment" refers to the lanthanum gallium titanate crystal before annealing; "after treatment" refers to the lanthanum gallium titanate crystal after annealing.

[0065] Depend on Figure 3 The test results show that the measured value of the nonlinear coefficient of the lanthanum gallium titanate crystal before annealing is 3.14 pm / V; the measured value of the nonlinear coefficient of the lanthanum gallium titanate crystal after annealing is 3.51 pm / V. Compared with the measured value of the nonlinear coefficient of the lanthanum gallium titanate crystal before annealing, the measured value of the nonlinear coefficient of the lanthanum gallium titanate crystal after annealing is improved.

[0066] This demonstrates that, by annealing the lanthanum gallium titanate crystal under an oxygen atmosphere, the Ti valence state can be regularized, thereby improving the electron cloud distribution and micro-polarization environment of the lanthanum gallium silicate crystal, and thus optimizing the macroscopic nonlinear optical coefficient of the lanthanum gallium silicate crystal.

[0067] Example 2 A method for designing and optimizing the performance of a lanthanum gallium silicate nonlinear optical crystal, differing from Example 1 in that, in step 2, the annealing temperature is adjusted to 900℃ and the annealing time is 48h; the specific preparation method includes the following steps: Step 2: Under an oxygen atmosphere, the lanthanum gallium titanate crystal is annealed at 900°C for 48 hours to allow the Ti in the lanthanum gallium titanate crystal to be absorbed. 3+ Ion oxidation to Ti 4+ The ions were cooled to room temperature to obtain annealed lanthanum gallium titanate crystals. The preparation method of annealed lanthanum gallium titanate crystals is as follows:

[0068] Take a piece of lanthanum gallium titanate crystal obtained by the Czochralski method and

[001] orientation in step 1, and process it into a size of 10×10×1mm. 3 The optical components were polished on both sides. The polished samples were placed in a high-temperature tubular annealing furnace, sealed, and purged with 99.99% pure oxygen at a flow rate of 50 sccm for 20 minutes to remove air from the furnace. Then, the furnace temperature was increased from room temperature to 900℃ at a rate of 120℃ / h, and annealed at 900℃ for 48 hours with continuous oxygen purging. After annealing, the temperature was slowly reduced to below 200℃ at a rate of 60℃ / h, and then cooled to room temperature with the furnace. The samples were then removed, yielding annealed lanthanum gallium titanate crystals.

[0069] Example 3 A method for designing and optimizing the performance of a lanthanum gallium silicate nonlinear optical crystal, differing from Example 1 in that, in step 2, the annealing temperature is adjusted to 1200℃ and the annealing time is 48h; the specific preparation method includes the following steps: Lanthanum gallium titanate crystals were annealed at 1200℃ for 48 hours in an oxygen atmosphere to allow the Ti in the lanthanum gallium titanate crystals to be reduced. 3+ Ion oxidation to Ti 4+ The ions were cooled to room temperature to obtain annealed lanthanum gallium titanate crystals. The preparation method of annealed lanthanum gallium titanate crystals is as follows:

[0070] Take a piece of lanthanum gallium titanate crystal obtained by the Czochralski method and

[001] orientation in step 1, and process it into a size of 10×10×1mm. 3The optical components were polished on both sides. The polished samples were placed in a high-temperature tubular annealing furnace, sealed, and purged with 99.99% pure oxygen at a flow rate of 50 sccm for 20 minutes to remove air from the furnace. Then, the furnace temperature was increased from room temperature to 1200℃ at a rate of 120℃ / h, and annealed at 1200℃ for 48 hours with continuous oxygen purging. After annealing, the temperature was slowly reduced to below 200℃ at a rate of 60℃ / h, and then cooled to room temperature with the furnace. The samples were then removed, yielding annealed lanthanum gallium titanate crystals.

[0071] Comparative Example 1 A design method for a lanthanum gallium silicate nonlinear optical crystal differs from Example 3 in that step 2 is not performed. The lanthanum gallium titanate crystal before annealing is obtained by following the steps in step 1.

[0072] Table 1. Properties of lanthanum gallium titanate crystals after annealing under different annealing parameters Note: "-" indicates that there is no relevant data.

[0073] In Examples 1 to 3 of this invention, the purpose of annealing is to reduce Ti. 3+ Theoretical studies have shown that, within a reasonable temperature range, longer annealing time is more conducive to ion valence state transformation, particularly for Ti ions. 3+ The less, the better for performance improvement.

[0074] Performance tests were conducted on the annealed lanthanum gallium titanate crystal from Example 2. The results showed that the damage threshold of the annealed lanthanum gallium titanate crystal increased to 1.75 GW / cm², and the nonlinear coefficient was optimized to 3.29 pm / V, demonstrating significant improvements. Local deformation of the lanthanum gallium titanate crystal was observed as the annealing temperature exceeded 1400℃. Therefore, the optimized annealing temperature range is 900℃ to 1400℃.

[0075] In summary, the embodiments of the present invention introduce Ti into lanthanum gallium silicate crystals. 4+ Ions were designed to form lanthanum gallium titanate crystals, reducing the generation of inherent defects in lanthanum gallium titanate crystals, specifically targeting Ti. 3+ The presence of oxygen vacancies provides a directional annealing process that effectively solves the performance defects of lanthanum gallium titanate crystals caused by Ti valence variation, laying a solid foundation for its application in high-power all-solid-state lasers.

[0076] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for designing and optimizing the performance of a lanthanum gallium silicate nonlinear optical crystal, characterized in that, Includes the following steps: A lanthanum gallium silicate crystal is provided, wherein the lanthanum gallium silicate crystal is La3M. 0.5 Ga 5.5 O 14 Crystal, where M is Nb 5+ Or Ta 5+ ; Through La3M 0.5 Ga 5.5 O 14 By introducing tetravalent Ti ions into the crystal to replace pentavalent Nb / Ta ions and trivalent Ga ions, the intrinsic oxygen vacancy defects are reduced, resulting in lanthanum gallium titanate crystals; the chemical formula of lanthanum gallium titanate crystals is La3TiGa5O. 14 ; Lanthanum gallium titanate crystals were annealed at 900℃~1400℃ in an oxygen atmosphere to remove the Ti in the lanthanum gallium titanate crystals. 3+ Ion oxidation to Ti 4+ After cooling the ions to room temperature, lanthanum gallium titanate crystals with oxygen defects were obtained.

2. The method for designing and optimizing the performance of lanthanum gallium silicate nonlinear optical crystals according to claim 1, characterized in that, The annealing time is 10h to 100h.

3. The method for designing and optimizing the performance of lanthanum gallium silicate crystals according to claim 2, characterized in that, The specific steps for annealing are as follows: In an oxygen atmosphere, lanthanum gallium titanate crystals are heated to 900℃ to 1400℃ at a rate of 10℃ / h to 120℃ / h, annealed at 900℃ to 1400℃ for 10h to 100h, and then cooled to below 200℃ at a rate of 10℃ / h to 100℃ / h, and then cooled to room temperature in the furnace to obtain lanthanum gallium titanate crystals with oxygen defects eliminated.

4. The method for designing and optimizing the performance of lanthanum gallium silicate nonlinear optical crystals according to claim 1, characterized in that, The oxygen atmosphere for the annealing process is 99.99% pure oxygen, and the oxygen flow rate is 50 sccm.

5. The method for designing and optimizing the performance of lanthanum gallium silicate nonlinear optical crystals according to claim 1, characterized in that, The preparation method of lanthanum gallium titanate crystal is as follows: La2O3, TiO2 and Ga2O3 are used as raw materials. They are mixed, pressed into blocks, and sintered into polycrystalline materials. The polycrystalline materials are melted to form a melt. Lanthanum gallium titanate seed crystals are added to the melt, and single crystals are grown by the Czochralski method. After in-situ annealing and cooling, lanthanum gallium titanate crystals are obtained.

6. The method for designing and optimizing the performance of lanthanum gallium silicate nonlinear optical crystals according to claim 5, characterized in that, The melting of polycrystalline materials is carried out under oxygen-deficient conditions; the oxygen-deficient conditions are: a mixed gas with an oxygen volume content of 0.5% to 2%.

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