A method for preparing a self-frequency doubling crystal with high rate efficiency and a visible laser device

Abstract

The present invention discloses a method for preparing a self-frequency doubling crystal with high magnification efficiency and a visible laser device, including using X-ray diffraction measurement, birefringence measurement, polarized light interferometry, first principles and finite element analysis to determine five directions that maximize the nonlinear optical coefficient of the crystal; comparing the energy loss of light propagating along the above five directions, determining that the direction with the lowest energy loss is the optimal direction of the non-principal plane; based on the determined optimal direction, using it as the non-principal plane direction for self-frequency doubling crystal processing; its beneficial effects are: 1. By combining multiple means such as X-ray diffraction measurement, birefringence measurement, polarized light interferometry, first principles and finite element analysis, the optimal direction that can maximize the nonlinear optical coefficient of the crystal, namely the non-principal plane direction, is comprehensively and accurately determined. Compared with the prior art, compared with the traditional processing method along the principal plane direction, the frequency doubling efficiency of the self-frequency doubling crystal is significantly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of laser crystal materials, and in particular relates to a method for preparing a self-frequency doubling crystal with high magnification efficiency and a visible laser device. Background Art

[0002] Self-frequency doubling laser crystals play an extremely important role in the field of laser technology. They can directly convert fundamental frequency light into frequency-doubled light and have great potential in realizing miniaturized and efficient laser light sources.

[0003] Traditional self-doubling crystal processing is mostly carried out along the principal plane direction. However, this traditional principal plane processing method has many disadvantages. Since the nonlinear optical coefficient of the crystal has significant differences in different directions, and the principal plane direction is not the direction that can maximize the nonlinear optical coefficient of the crystal, it is difficult for the self-doubling crystal to fully realize its performance potential in the nonlinear optical process and cannot meet the stringent requirements of modern laser technology for high magnification efficiency.

[0004] In order to solve the problems raised in the above background technology, the present invention provides a method for preparing a self-frequency doubling crystal with high magnification efficiency and a visible laser device.

[0005] To achieve the above object, the present invention provides the following technical solution: A method for preparing a self-frequency doubling crystal with high rate efficiency comprises the following steps:

[0006] S1. Use material analysis and simulation methods to determine several directions that maximize the nonlinear optical coefficient of the crystal;

[0007] S2, compare the energy loss of light propagating along several directions, and determine that the direction with the lowest energy loss is the optimal direction of the non-principal plane;

[0008] S3, according to the determined optimal direction, using it as a non-principal plane direction for self-frequency doubling crystal processing;

[0009] S4. According to the crystal characteristics, the crystal is cut along a non-planar direction to obtain a self-folding crystal.

[0010] Specifically: Material analysis and simulation methods include: X-ray diffraction measurement, birefringence measurement, polarized light interferometry, first principles and finite element analysis.

[0011] Step S1 includes: determining the optimal direction capable of maximizing the nonlinear optical coefficient of the crystal by X-ray diffraction measurement, birefringence measurement, polarized light interferometry, and first principle and finite element analysis;

[0012] Specifically: X-ray diffraction measurements are used to obtain the lattice parameters and crystallographic axis information of the crystal; the direction of the nonlinear optical coefficient is determined based on the symmetry and atomic arrangement of the crystal, and is used as the first direction that can maximize the nonlinear optical coefficient of the crystal

[0013] The X-ray diffraction measurement method is:

[0014] Use an X-ray diffractometer to scan the crystal;

[0015] According to Bragg's law nλ=2dsin(θ), by analyzing the position of the Bragg peak in the diffraction pattern, the crystal system, space group and directions of each crystallographic axis of the crystal are determined, thereby obtaining the crystallographic axis information of the crystal; according to the symmetry and atomic arrangement of the crystal, the first direction that can maximize the nonlinear optical coefficient of the crystal is determined; that is, the directions in which the crystal has the best nonlinear optical corresponding characteristics are determined; and guidance is provided for the application of crystals in the field of nonlinear optics, such as the application of self-doubling crystals in visible laser devices;

[0016] n is the diffraction order; λ is the wavelength of the incident X-ray; d is the interplanar spacing, whose value reflects the characteristics of the crystal microstructure; θ is the Bragg angle, that is, the angle between the incident X-ray and the crystal plane;

[0017] Specifically: Birefringence measurement is used to determine the direction with the maximum birefringence effect in the crystal, which is the optical axis direction of the crystal; and the optical axis direction is used as the second direction that can maximize the nonlinear optical coefficient of the crystal;

[0018] The birefringence measurement method is:

[0019] Use a birefringent instrument to measure the crystal;

[0020] By measuring the difference in propagation speed between ordinary light and extraordinary light in the crystal, according to the birefringence Δn1=n e -n o Obtaining the maximum value of the birefringence and its corresponding direction, thereby determining the direction with the maximum birefringence effect in the crystal, which is the optical axis direction of the crystal; and taking the optical axis direction of the crystal as the second direction that can maximize the nonlinear optical coefficient of the crystal;

[0021] n e is the extraordinary refractive index; n o is the ordinary light refractive index; Δn1 is the birefringence;

[0022] Specifically: Polarized light interferometry is used to observe the interference pattern of light in a crystal by using a polarized light interferometer, changing the angle and polarization state of the incident light, and recording the changes in the interference fringes, thereby deriving the direction of the optical axis of the crystal; and using the optical axis direction as the third direction that can maximize the nonlinear optical coefficient of the crystal;

[0023] Polarized light interferometry can further verify the results of birefringence measurement and achieve precise positioning of the optical axis;

[0024] The measurement method of polarization interferometry is:

[0025] Use polarization interferometer to observe the interference pattern of light in crystal;

[0026] By changing the angle and polarization state of the incident light, the changes in the interference fringes are recorded;

[0027] According to the recorded interference fringe movement and the geometric parameters of the interferometer, the phase difference formula is used: And the interference fringe movement formula: Calculate the phase difference δ under different incident conditions; Based on the calculation results, analyze the law of the phase δ difference changing with the incident light angle and polarization direction, determine the direction of the optical axis, further verify the birefringence measurement results and achieve accurate positioning of the optical axis; and use the optical axis direction as the third direction that can maximize the nonlinear optical coefficient of the crystal;

[0028] The direction of the optical axis is the direction in which the interaction between light and the crystal is strongest;

[0029] δ is the phase difference; d1 is the optical path difference; λ1 is the wavelength of the incident light; Δx is the movement of the interference fringes; L is the distance from the intersection of the two beams of light in the interferometer to the observation screen, and D is the distance between the two beams of light

[0030] The method for analyzing the law of phase difference changing with the incident light angle and polarization direction is as follows: by analyzing the phase difference, combining the birefringence characteristics of the crystal and the symmetry of the crystal structure, the direction of the optical axis of the crystal is deduced; in a crystal with a specific symmetry, the direction of the optical axis corresponds to the symmetry axis of the phase difference change. For example, in a uniaxial crystal, when the incident light propagates in a direction parallel or perpendicular to the optical axis, it will show a specific phase difference change law. By identifying these laws, the direction of the optical axis can be determined; at the same time, the derived optical axis direction is compared and verified with the results of the birefringence measurement to ensure the accuracy of the determination of the optical axis direction. In multi-axis crystals, it is necessary to comprehensively consider multiple phase difference change trends and the higher-order symmetry of the crystal to determine the direction of the optical axis; the above basic principles for determining the optical axis are all based on the relationship between the phase difference change when light propagates in the crystal and the crystal microstructure.

[0031] Specifically: First principles are used to assist in selecting the best crystal orientation for nonlinear optical performance; based on the calculation results, d eff The direction corresponding to the maximum angle is used as the fourth direction capable of maximizing the nonlinear optical coefficient of the crystal;

[0032] The first principle calculation method is:

[0033] The electronic structure of the crystal is calculated using quantum mechanics software, and the coefficients of the second harmonic generation are Using symmetry analysis and group theory to simplify d ijk Expression and optimize d eff , determine d eff The direction corresponding to the maximum angle is used as the fourth direction that can maximize the nonlinear optical coefficient of the crystal, thereby assisting in selecting the best nonlinear optical performance orientation of the crystal;

[0034] d eff is the second harmonic generation coefficient; d ijk is the nonlinear polarizability tensor element, E i and E j is the electric field component;

[0035] Specifically: Finite element analysis is used to select the direction with the least light propagation loss in the crystal as the fifth direction that can maximize the nonlinear optical coefficient of the crystal based on the simulation results; ensuring that the selected direction can achieve the best self-frequency doubling effect in practical applications;

[0036] The finite element analysis method is:

[0037] Use finite element analysis software to simulate the propagation path of light in the crystal;

[0038] Based on Maxwell's equations, obtain the distribution results of the electromagnetic field in the crystal;

[0039] Based on the distribution results, the propagation efficiency and conversion efficiency of light in different directions of the crystal are determined, and the stress distribution and thermal effects are analyzed at the same time; the direction with the smallest propagation loss of light in the crystal is taken as the fifth direction that can maximize the nonlinear optical coefficient of the crystal;

[0040] Since the electromagnetic field determines the propagation characteristics of light in the crystal, the propagation direction and intensity changes of light can be tracked by analyzing the electromagnetic field at different positions and times. Through simulation, the specific trajectory of light propagating in different directions inside the crystal can be obtained, and how the propagation behavior of light in the crystal is affected by the crystal orientation can be understood.

[0041] During the simulation, the energy of light before entering the crystal and the energy after propagating a certain distance in the crystal are calculated. The ratio of the two reflects the propagation efficiency. By simulating crystals with different orientations, the orientation that minimizes the energy loss of light propagation is found, that is, the orientation with the highest propagation efficiency.

[0042] During the simulation process, the optimal crystal orientation is determined by simulating different orientations to achieve higher conversion efficiency.

[0043] By analyzing and simulating stress distribution, the processing technology can be optimized, such as selecting the appropriate cutting direction, controlling processing parameters, etc., so that the stress inside the crystal is evenly distributed and damage to the crystal due to excessive stress can be avoided.

[0044] By analyzing the thermal effects, appropriate measures can be taken, such as heat dissipation measures, to prevent heat from adversely affecting crystal performance;

[0045] Finite element analysis software simulation is used to ensure that the selected fifth direction achieves the best self-frequency doubling effect in practical applications and optimizes the crystal orientation;

[0046] Specifically: by comparing the energy loss of light propagating along the first direction, the second direction, the third direction, the fourth direction and the fifth direction respectively; the direction with the lowest energy loss is taken as the optimal direction; the optimal direction is the non-principal plane direction that can maximize the nonlinear optical coefficient of the crystal;

[0047] Specifically: The method for judging the level of energy loss is to judge the level of energy loss by comparing the distances of light propagation in different directions; the direction in which the light propagates the farthest in the crystal is the direction with the lowest energy loss; the direction in which the light propagates the shortest in the crystal is the direction with the highest energy loss;

[0048] Specifically: step S2 includes:

[0049] According to the optimal direction determined in step S1, the optimal direction is used as the non-principal plane direction;

[0050] For self-frequency doubling crystals, the non-principal plane direction that can maximize the nonlinear optical coefficient of the crystal must be selected as the processing direction in order to significantly improve the self-frequency doubling efficiency.

[0051] Directional cutting of crystals along non-planar directions;

[0052] The method of directional cutting of crystals is to use high-precision cutting equipment to cut the crystal in a determined non-principal plane direction; when cutting, it is necessary to ensure that the path of the tool or laser beam is consistent with the optimal direction of the crystal to avoid introducing unnecessary stress or damage.

[0053] Obtain a flat, smooth and crack-free cutting surface through cutting to ensure the structural integrity of the crystal;

[0054] Specifically: A visible laser device, used to implement the above method, includes: a self-frequency doubling crystal, a coupler, an amplifier, a pump source, and a beam combiner.

[0055] Methods for cutting crystals include: cutting with diamond tools;

[0056] For hard crystalline materials, diamond tools are used for cutting. Diamond tools have extremely high hardness and wear resistance, suitable for precise cutting. The cutting speed and feed rate need to be controlled during the cutting process to avoid overheating or excessive stress that may cause the crystal to break.

[0057] High-precision cutting is achieved through diamond tool cutting to ensure the quality of the cut surface.

[0058] Methods for cutting crystals include: laser cutting;

[0059] For crystals that are sensitive to heat or difficult to cut mechanically, laser cutting technology is used; laser cutting can achieve precise cutting without excessive heat effects, and is particularly suitable for processing thin slices or crystals with complex shapes;

[0060] Laser cutting avoids thermal damage and ensures the flatness and smoothness of the cut surface.

[0061] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0062] 1. The high-efficiency self-frequency doubling crystal preparation method and visible laser device comprehensively and accurately determine the optimal direction that can maximize the nonlinear optical coefficient of the crystal, that is, the non-principal plane direction, by combining multiple methods such as X-ray diffraction measurement, birefringence measurement, polarized light interferometry, first principles and finite element analysis. Compared with the existing technology, compared with the traditional method of processing along the principal plane direction, the frequency doubling efficiency of the self-frequency doubling crystal is significantly improved.

[0063] 2. The high-rate efficiency self-frequency doubling crystal preparation method and visible laser device can achieve high-precision cutting when cutting hard crystals with diamond tools due to their extremely high hardness and wear resistance. In the cutting process, by reasonably controlling the cutting speed and feed rate, overheating or excessive stress can be effectively avoided, crystal breakage can be prevented, the quality of the cutting surface can be ensured, the integrity of the crystal structure can be maintained, and the excellent performance of the crystal can be maintained, thereby ensuring that its nonlinear optical effect can be stably exerted in subsequent applications.

[0064] 3. The high-rate efficiency self-doubling crystal preparation method and visible laser device are very useful for crystals that are sensitive to heat or difficult to cut by conventional mechanical methods. It can achieve precise cutting without excessive heat effects, and is particularly suitable for processing thin slices or crystals with complex shapes. This can avoid thermal damage, ensure the flatness and smoothness of the cut surface, and allow the crystal to still have good optical properties after processing, which helps to improve the actual effect of the entire self-doubling crystal in laser applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0066] Figure 1 It is a schematic diagram of the process of the present invention; DETAILED DESCRIPTION

[0067] The present invention will now be further described in detail with reference to the accompanying drawings and embodiments. These drawings are simplified schematic diagrams that only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0068] A method for preparing a self-frequency doubling crystal with high rate efficiency comprises the following steps:

[0069] S1. Use material analysis and simulation methods to determine several directions that maximize the nonlinear optical coefficient of the crystal;

[0070] S2, compare the energy loss of light propagating along several directions, and determine that the direction with the lowest energy loss is the optimal direction of the non-principal plane;

[0071] S3, according to the determined optimal direction, using it as a non-principal plane direction for self-frequency doubling crystal processing;

[0072] S4. According to the crystal characteristics, the crystal is cut along a non-planar direction to obtain a self-folding crystal.

[0073] Specifically: Material analysis and simulation methods include: X-ray diffraction measurement, birefringence measurement, polarized light interferometry, first principles and finite element analysis.

[0074] Step S1 includes: determining the optimal direction capable of maximizing the nonlinear optical coefficient of the crystal by X-ray diffraction measurement, birefringence measurement, polarized light interferometry, and first principle and finite element analysis;

[0075] Specifically: X-ray diffraction measurements are used to obtain the lattice parameters and crystallographic axis information of the crystal; the direction of the nonlinear optical coefficient is determined based on the symmetry and atomic arrangement of the crystal, and is used as the first direction that can maximize the nonlinear optical coefficient of the crystal

[0076] The X-ray diffraction measurement method is:

[0077] Use an X-ray diffractometer to scan the crystal;

[0078] According to Bragg's law nλ=2dsin(θ), by analyzing the position of the Bragg peak in the diffraction pattern, the crystal system, space group and directions of each crystallographic axis of the crystal are determined, thereby obtaining the crystallographic axis information of the crystal; according to the symmetry and atomic arrangement of the crystal, the first direction that can maximize the nonlinear optical coefficient of the crystal is determined; that is, the directions in which the crystal has the best nonlinear optical corresponding characteristics are determined; and guidance is provided for the application of crystals in the field of nonlinear optics, such as the application of self-doubling crystals in visible laser devices;

[0079] n is the diffraction order; λ is the wavelength of the incident X-ray; d is the interplanar spacing, whose value reflects the characteristics of the crystal microstructure; θ is the Bragg angle, that is, the angle between the incident X-ray and the crystal plane;

[0080] Specifically: Birefringence measurement is used to determine the direction with the maximum birefringence effect in the crystal, which is the optical axis direction of the crystal; and the optical axis direction is used as the second direction that can maximize the nonlinear optical coefficient of the crystal;

[0081] The birefringence measurement method is:

[0082] Use a birefringent instrument to measure the crystal;

[0083] By measuring the difference in propagation speed between ordinary light and extraordinary light in the crystal, according to the birefringence Δn1=n e -n o Obtaining the maximum value of the birefringence and its corresponding direction, thereby determining the direction with the maximum birefringence effect in the crystal, which is the optical axis direction of the crystal; and taking the optical axis direction of the crystal as the second direction that can maximize the nonlinear optical coefficient of the crystal;

[0084] n e is the extraordinary refractive index; n o is the ordinary light refractive index; Δn1 is the birefringence;

[0085] Specifically: Polarized light interferometry is used to observe the interference pattern of light in a crystal by using a polarized light interferometer, changing the angle and polarization state of the incident light, and recording the changes in the interference fringes, thereby deriving the direction of the optical axis of the crystal; and using the optical axis direction as the third direction that can maximize the nonlinear optical coefficient of the crystal;

[0086] Polarized light interferometry can further verify the results of birefringence measurement and achieve precise positioning of the optical axis;

[0087] The measurement method of polarization interferometry is:

[0088] Use polarization interferometer to observe the interference pattern of light in crystal;

[0089] By changing the angle and polarization state of the incident light, the changes in the interference fringes are recorded;

[0090] According to the recorded interference fringe movement and the geometric parameters of the interferometer, the phase difference formula is used: And the interference fringe movement formula: Calculate the phase difference δ under different incident conditions; Based on the calculation results, analyze the law of the phase δ difference changing with the incident light angle and polarization direction, determine the direction of the optical axis, further verify the birefringence measurement results and achieve accurate positioning of the optical axis; and use the optical axis direction as the third direction that can maximize the nonlinear optical coefficient of the crystal;

[0091] The direction of the optical axis is the direction in which the interaction between light and the crystal is strongest;

[0092] δ is the phase difference; d1 is the optical path difference; λ1 is the wavelength of the incident light; Δx is the movement of the interference fringes; L is the distance from the intersection of the two beams of light in the interferometer to the observation screen, and D is the distance between the two beams of light

[0093] The method for analyzing the law of phase difference changing with the incident light angle and polarization direction is as follows: by analyzing the phase difference, combining the birefringence characteristics of the crystal and the symmetry of the crystal structure, the direction of the optical axis of the crystal is deduced; in some crystals with specific symmetry, the direction of the optical axis corresponds to the symmetry axis of the phase difference change. For example, in a uniaxial crystal, when the incident light propagates in a direction parallel or perpendicular to the optical axis, it will show a specific phase difference change law. By identifying these laws, the direction of the optical axis can be determined; at the same time, the derived optical axis direction is compared and verified with the results of the birefringence measurement to ensure the accuracy of the determination of the optical axis direction. In multi-axis crystals, it is necessary to comprehensively consider multiple phase difference change trends and the higher-order symmetry of the crystal to determine the direction of the optical axis; the above basic principles for determining the optical axis are all based on the relationship between the phase difference change when light propagates in the crystal and the crystal microstructure.

[0094] Specifically: First principles are used to assist in selecting the best crystal orientation for nonlinear optical performance; based on the calculation results, d eff The direction corresponding to the maximum angle is used as the fourth direction capable of maximizing the nonlinear optical coefficient of the crystal;

[0095] The first principle calculation method is:

[0096] The electronic structure of the crystal is calculated using quantum mechanics software, and the coefficients of the second harmonic generation are Using symmetry analysis and group theory to simplify d ijk Expression and optimize d eff , determine d eff The direction corresponding to the maximum angle is used as the fourth direction that can maximize the nonlinear optical coefficient of the crystal, thereby assisting in selecting the best nonlinear optical performance orientation of the crystal;

[0097] d eff is the second harmonic generation coefficient; d ijk is the nonlinear polarizability tensor element, E i and E j is the electric field component;

[0098] Specifically: Finite element analysis is used to select the direction with the least light propagation loss in the crystal as the fifth direction that can maximize the nonlinear optical coefficient of the crystal based on the simulation results; ensuring that the selected direction can achieve the best self-frequency doubling effect in practical applications;

[0099] The finite element analysis method is;

[0100] Use finite element analysis software to simulate the propagation path of light in the crystal;

[0101] Based on Maxwell's equations, obtain the distribution results of the electromagnetic field in the crystal;

[0102] Based on the distribution results, the propagation efficiency and conversion efficiency of light in different directions of the crystal are determined, and the stress distribution and thermal effects are analyzed at the same time; the direction with the smallest propagation loss of light in the crystal is taken as the fifth direction that can maximize the nonlinear optical coefficient of the crystal;

[0103] Since the electromagnetic field determines the propagation characteristics of light in the crystal, the propagation direction and intensity changes of light can be tracked by analyzing the electromagnetic field at different positions and times. Through simulation, the specific trajectory of light propagating in different directions inside the crystal can be obtained, and how the propagation behavior of light in the crystal is affected by the crystal orientation can be understood.

[0104] During the simulation, the energy of light before entering the crystal and the energy after propagating a certain distance in the crystal are calculated. The ratio of the two reflects the propagation efficiency. By simulating crystals with different orientations, the orientation that minimizes the energy loss of light propagation is found, that is, the orientation with the highest propagation efficiency.

[0105] During the simulation process, the optimal crystal orientation is determined by simulating different orientations to achieve higher conversion efficiency.

[0106] By analyzing and simulating stress distribution, the processing technology can be optimized, such as selecting the appropriate cutting direction, controlling processing parameters, etc., so that the stress inside the crystal is evenly distributed and damage to the crystal due to excessive stress can be avoided.

[0107] By analyzing the thermal effects, appropriate measures, such as heat dissipation measures, can be taken to prevent heat from adversely affecting crystal performance.

[0108] Finite element analysis software simulation is used to ensure that the selected fifth direction achieves the best self-frequency doubling effect in practical applications and optimizes the crystal orientation;

[0109] Specifically: by comparing the energy loss of light propagating along the first direction, the second direction, the third direction, the fourth direction and the fifth direction respectively; the direction with the lowest energy loss is taken as the optimal direction; the optimal direction is the non-principal plane direction that can maximize the nonlinear optical coefficient of the crystal;

[0110] Specifically: The method for judging the level of energy loss is to judge the level of energy loss by comparing the distances of light propagation in different directions; the direction in which the light propagates the farthest in the crystal is the direction with the lowest energy loss; the direction in which the light propagates the shortest in the crystal is the direction with the highest energy loss;

[0111] Specifically: step S2 includes:

[0112] According to the optimal direction determined in step S1, the optimal direction is used as the non-principal plane direction;

[0113] For self-frequency doubling crystals, the non-principal plane direction that can maximize the nonlinear optical coefficient of the crystal must be selected as the processing direction in order to significantly improve the self-frequency doubling efficiency.

[0114] Directional cutting of crystals along non-planar directions;

[0115] The method of directional cutting of crystals is to use high-precision cutting equipment to cut the crystal in a determined non-principal plane direction; when cutting, it is necessary to ensure that the path of the tool or laser beam is consistent with the optimal direction of the crystal to avoid introducing unnecessary stress or damage.

[0116] Obtain a flat, smooth and crack-free cutting surface through cutting to ensure the structural integrity of the crystal;

[0117] Specifically: A visible laser device, used to implement the above method, includes: a self-frequency doubling crystal, a coupler, an amplifier, a pump source, and a beam combiner.

[0118] Methods for cutting crystals include: For hard crystal materials, diamond tools are used for cutting. Diamond tools have extremely high hardness and wear resistance, making them suitable for precise cutting. The cutting speed and feed rate need to be controlled during the cutting process to avoid overheating or excessive stress that may cause the crystal to break.

[0119] High-precision cutting is achieved through diamond tool cutting to ensure the quality of the cut surface.

[0120] Methods for cutting crystals include: laser cutting;

[0121] For crystals that are sensitive to heat or difficult to cut mechanically, laser cutting technology is used; laser cutting can achieve precise cutting without excessive heat effects, and is particularly suitable for processing thin slices or crystals with complex shapes;

[0122] Laser cutting avoids thermal damage and ensures the flatness and smoothness of the cut surface.

[0123] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0124] An embodiment of the present invention includes: in the field of laser crystal processing, this embodiment relates to an innovative 4.2 self-frequency doubling laser crystal processing technology.

[0125] First, we need to identify the crystal Direction of the nonlinear optical coefficient , based on which the correct processing direction of the self-frequency doubling crystal is determined. When processing along the main plane direction in the traditional way, the material performance has certain limitations. However, this embodiment adopts a unique processing method, and the processing direction is selected as the non-main plane direction.

[0126] During the processing, the material performance in the non-principal plane direction was significantly improved through precise process operation. Specifically, its nonlinear coefficient reached deff = 1.68pm / V, which is 3 times higher than that when processed along the principal plane direction, and the frequency doubling efficiency was increased by nearly an order of magnitude.

[0127] Finally, after this non-principal plane processing, the self-frequency doubling crystal has reached a practical state, successfully overcoming the performance bottleneck under traditional processing methods, and providing strong technical support for the promotion of self-frequency doubling laser crystals in practical applications. This processing technology has important application value in the laser crystal related industry and is expected to promote further development in related fields.

[0128] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example.

[0129] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a self-frequency doubling crystal with high rate efficiency, characterized in that: The following steps are involved: S1. Use material analysis and simulation methods to determine several directions that maximize the nonlinear optical coefficient of the crystal; S2, compare the energy loss of light propagating along several directions, and determine that the direction with the lowest energy loss is the optimal direction of the non-principal plane; S3, according to the determined optimal direction, using it as a non-principal plane direction for self-frequency doubling crystal processing; S4. According to the crystal characteristics, the crystal is cut along a non-planar direction to obtain a self-folding crystal.

2. The method for preparing a self-frequency doubling crystal with high rate efficiency according to claim 1, characterized in that: The material analysis and simulation methods include: X-ray diffraction measurement, birefringence measurement, polarized light interferometry, first principles and finite element analysis.

3. The method for preparing a self-frequency doubling crystal with high rate efficiency according to claim 1, characterized in that: The X-ray diffraction measurement method is: Use an X-ray diffractometer to scan the crystal; According to Bragg's law nλ=2dsin(θ), the crystal system, space group and directions of each crystallographic axis of the crystal are determined by analyzing the position of the Bragg peak in the diffraction pattern, thereby obtaining the crystallographic axis information of the crystal; based on the symmetry and atomic arrangement of the crystal, the first direction that can maximize the nonlinear optical coefficient of the crystal is determined.

4. The method for preparing a self-frequency doubling crystal with high rate efficiency according to claim 1, characterized in that: The birefringence measurement method is: Use a birefringent instrument to measure the crystal; By measuring the difference in propagation speed between ordinary light and extraordinary light in the crystal, according to the birefringence Δn1=n e -n o The maximum value of the birefringence and its corresponding direction are obtained to determine the direction with the maximum birefringence effect in the crystal, which is the optical axis direction of the crystal; and the optical axis direction of the crystal is used as the second direction that can maximize the nonlinear optical coefficient of the crystal.

5. The method for preparing a self-frequency doubling crystal with high rate efficiency according to claim 1, characterized in that: The measurement method of polarization interferometry is: Use polarization interferometer to observe the interference pattern of light in crystal; By changing the angle and polarization state of the incident light, the changes in the interference fringes are recorded; According to the recorded interference fringe movement and the geometric parameters of the interferometer, the phase difference formula is used: And the interference fringe movement formula: Calculate the phase difference δ under different incident conditions; based on the calculation results, analyze the law of how the phase δ difference changes with the incident light angle and polarization direction, determine the direction of the optical axis, further verify the birefringence measurement results and achieve precise positioning of the optical axis; and use the optical axis direction as the third direction that can maximize the nonlinear optical coefficient of the crystal.

6. The method for preparing a self-frequency doubling crystal with high rate efficiency according to claim 1, characterized in that: The first principle calculation method is: The electronic structure of the crystal is calculated using quantum mechanics software, and the coefficients of the second harmonic generation are Using symmetry analysis and group theory to simplify d ijk Expression and optimize d eff , determine d eff The direction corresponding to the maximum angle is used as the fourth direction that can maximize the nonlinear optical coefficient of the crystal, thereby assisting in selecting the best nonlinear optical performance orientation of the crystal.

7. The method for preparing a self-frequency doubling crystal with high rate efficiency according to claim 1, characterized in that: The finite element analysis method is: Use finite element analysis software to simulate the propagation path of light in the crystal; Based on Maxwell's equations, obtain the distribution results of the electromagnetic field in the crystal; Based on the distribution results, the propagation efficiency and conversion efficiency of light in different directions of the crystal are determined, and the stress distribution and thermal effects are analyzed at the same time; the direction in which the light propagation loss in the crystal is the smallest is taken as the fifth direction that can maximize the nonlinear optical coefficient of the crystal.

8. The method for preparing a self-frequency doubling crystal with high rate efficiency according to claim 1, characterized in that: The method for determining the optimal direction of a non-planar surface is: By comparing the energy loss of light propagating along the first direction, the second direction, the third direction, the fourth direction and the fifth direction respectively; the direction with the lowest energy loss is taken as the optimal direction; the optimal direction is the non-principal plane direction that can maximize the nonlinear optical coefficient of the crystal.

9. The method for preparing a self-frequency doubling crystal with high rate efficiency according to claim 1, characterized in that: The method for judging the energy loss is: The energy loss can be determined by comparing the distances that light travels in different directions. The direction in which light travels the farthest in the crystal has the lowest energy loss, while the direction in which light travels the shortest distance in the crystal has the highest energy loss.

10. A visible laser device, used to implement the method according to any one of claims 1 to 9, characterized in that: include: Self-frequency doubling crystals, couplers, amplifiers, pump sources, and beam combiners.

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