Method and device for measuring absorption coefficient of transparent crystal

Abstract

The invention discloses a transparent crystal absorption coefficient measuring method and device, and the method comprises the steps: measuring the first transmissivity of two samples with different thicknesses corresponding to transparent crystals of the same type under first incident light, and calculating the absorption coefficient of the transparent crystals according to the thickness difference of the two samples and the first transmissivity, calculating a first absorption coefficient of the transparent crystal in an absorption process and first reflectivity corresponding to the two samples respectively; the total transmission amount and the total reflection amount of the samples in one or more absorption processes are kept unchanged and constrained, second absorption coefficients and second reflectivity corresponding to the two samples in N absorption processes corresponding to at least one N value are calculated, and N is an odd number larger than 1; and analyzing the change rule of the absorption coefficients and the reflectivity corresponding to different absorption processes, and determining the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light according to the second absorption coefficient in the target absorption process. The measurement accuracy of the absorption coefficient of transparent crystals such as gallium nitride crystals can be improved.

Description

Technical Field

[0001] This invention belongs to the field of intrinsic absorption coefficient measurement technology for crystals, and more specifically, relates to a method and apparatus for measuring the absorption coefficient of a transparent crystal. Background Technology

[0002] Transparent crystals are core materials in the modern optical industry, such as gallium nitride, calcium fluoride, sapphire, and various laser crystals. The absorption coefficient, especially the intrinsic absorption coefficient, is one of the most critical parameters for evaluating the optical quality of transparent crystals. It characterizes the degree of energy attenuation caused by light absorption within the crystal as it propagates. Accurate measurement of the absorption coefficient of transparent crystals is essential for assessing the purity of crystal materials, predicting the laser damage threshold of optical components, and designing high-performance optical systems.

[0003] Currently, the conventional method for measuring the absorption coefficient of transparent crystals is mainly based on the transmission method of spectrophotometers. However, for high-quality transparent crystals, their intrinsic absorption coefficient is extremely low, and conventional transmission methods face many insurmountable technical bottlenecks during measurement, resulting in severely distorted measurement results that fail to reflect the true intrinsic properties of the material. Existing technology lacks a method for rapidly, accurately, and non-destructively measuring the absorption coefficient of transparent crystals in industrial applications. Summary of the Invention

[0004] The main objective of this invention is to provide a method and apparatus for measuring the absorption coefficient of a transparent crystal, so as to overcome the shortcomings of the prior art.

[0005] An embodiment of the present invention provides a method for measuring the absorption coefficient of a transparent crystal, comprising: The first transmittance of two samples with different thicknesses corresponding to the same type of transparent crystal under the first incident light was measured respectively. Based on the thickness difference between the two samples and the measured first transmittance, the first absorption coefficient of the transparent crystal and the first reflectance of each of the two samples are calculated under an absorption process. Under the constraint that the total transmittance and total reflectance of the two samples remain unchanged under one or more absorption processes (corresponding to the total absorption of each sample remaining unchanged), based on the first absorption coefficient, the thickness of the two samples and the first transmittance, the second absorption coefficient and second reflectance of the two samples under N absorption processes corresponding to at least one value of N are calculated, where N is an odd number greater than 1.

[0006] The variation patterns of absorption coefficient and reflectance corresponding to different absorption processes are analyzed. The absorption coefficient of the above transparent crystal at the wavelength corresponding to the first incident light is determined based on the second absorption coefficient under the target absorption process; where the target absorption process corresponds to one value of N.

[0007] In a preferred embodiment, the first reflectivity is calculated as follows: The two first transmittances mentioned above are respectively used as the total transmittance of each sample. For each sample, the first reflectance of the current sample under one absorption process is calculated based on the first absorption coefficient, the thickness of the current sample, and the corresponding first transmittance, so as to obtain the first reflectance of each of the two samples mentioned above. Wherein, with the constraint that the total transmittance and total reflectance of the two aforementioned samples remain constant under one or more absorption processes, based on the aforementioned first absorption coefficient, the respective thicknesses of the two aforementioned samples, and their respective first transmittances, the second absorption coefficient and second reflectance corresponding to the two aforementioned samples under at least N absorption processes corresponding to at least one value of N are calculated, including: Based on the first reflectance, the first absorption coefficient, and the thickness of each of the two samples, calculate the total reflectance of each sample. With the constraint that the total transmittance and total reflectance of the two samples remain constant under one or more absorption processes, the second absorption coefficient and second reflectance of the two samples under N absorption processes corresponding to at least one value of N are calculated based on the total transmittance, the total reflectance, and the thickness of the two samples.

[0008] In a preferred embodiment, the variation patterns of absorption coefficient and reflectivity corresponding to different absorption processes are analyzed, and the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light is determined based on the second absorption coefficient under the target absorption process, including: Analyze the variation patterns of absorption coefficient and reflectance corresponding to different absorption processes. If the variation values ​​of absorption coefficient for M absorption processes and M+2 absorption processes are less than a first set threshold and the variation value of reflectance is less than a second set threshold, then the M absorption processes or M+2 absorption processes are determined as target absorption processes; where M+2 is a value of N. The absorption coefficient of the transparent crystal at the first incident light wavelength is determined based on the second absorption coefficient under the target absorption process described above.

[0009] In a preferred embodiment, it further includes: The second transmittance of two samples with different thicknesses corresponding to the transparent crystal under the second incident light was measured respectively. The wavelength of the second incident light was different from that of the first incident light. Based on the thickness difference between the two samples and the two measured second transmittances, the third absorption coefficient of the transparent crystal under an absorption process is calculated. Calculate the product of the third absorption coefficient and the set ratio, where the set ratio is equal to the ratio of the second absorption coefficient to the first absorption coefficient under the target absorption process. The absorption coefficient of the transparent crystal at the wavelength corresponding to the second incident light is determined based on the above product.

[0010] In a preferred embodiment, determining the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light based on the second absorption coefficient under the target absorption process includes one of the following: The second absorption coefficient under the target absorption process is determined to be the absorption coefficient of the aforementioned transparent crystal at the wavelength corresponding to the first incident light; or... The second absorption coefficient under the target absorption process is determined as the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light; the product of the above is determined as the absorption coefficient of the transparent crystal at the wavelength corresponding to the second incident light; or... Error measurement using a preset absorption coefficient right Error correction is performed, whereby... Before error correction, the above transparent crystal at wavelength The absorption coefficient was determined at a specific wavelength; the error correction result was used as the absorption coefficient of the aforementioned transparent crystal at a specific wavelength. The final absorption coefficient at the above error correction result is: Values ​​within the range; the above wavelengths It includes at least one wavelength corresponding to the first incident light and a wavelength corresponding to the second incident light.

[0011] In a preferred embodiment, it further includes: The transmittance of any transparent crystal sample under the same incident light was measured multiple times, and the average transmittance was calculated. The first transmittance is the average transmittance obtained from multiple measurements; optionally, the second transmittance is the average transmittance obtained from multiple measurements. Calculate the average transmittance above Limit error ; Based on the functional relationship between transmittance, thickness of transparent crystal sample, and absorption coefficient, the first limiting transmittance is calculated respectively. Second limit transmittance The corresponding absorption coefficient; Based on the first limiting transmittance Second limit transmittance The difference in the corresponding absorption coefficients is determined. ; Optional, The expression is as follows: This is half the difference in the absorption coefficients mentioned above. ; in, First limiting transmittance The corresponding absorption coefficient, Second limiting transmittance The corresponding absorption coefficient; Optionally, when the number of measurements is less than a set value, the limit error of the average transmittance is calculated. Specifically, this includes: the limiting error in calculating the mean transmittance value according to the t-distribution. .

[0012] In a preferred embodiment, the first absorption coefficient of the above-mentioned transparent crystal during an absorption process satisfies the following expression: ; in, The first absorption coefficient of a transparent crystal during an absorption process. and The thicknesses are those of two samples of the same type of transparent crystal but with different thicknesses. For thickness is The first transmittance of the sample, For thickness is The first transmittance of the sample, which is the result of a single measurement or the average transmittance of multiple measurements; Optionally, select one of the two samples with different thicknesses and a third sample with a different thickness, or for another set of two samples with different thicknesses, calculate the verification absorption coefficient at the wavelength corresponding to the first incident light. Based on the verification absorption coefficient, verify the second absorption coefficient under the target absorption process. After the verification is passed, output the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light.

[0013] In a preferred embodiment, the transparent crystal includes a gallium nitride crystal, wherein the gallium nitride crystal is undoped gallium nitride or silicon-doped gallium nitride; Optionally, the wavelength range of the incident light is 400nm~600nm; Optionally, for gallium nitride crystals, the value of N corresponding to the target absorption process is 3.

[0014] In a preferred embodiment, the total transmittance and total reflectance of the two samples described above during an absorption process satisfy the following set of equations: ; ; ; ; in, The total transmittance of the first sample in one absorption process is the first transmittance of the first sample, which is a known quantity for measurement. The first reflectance of the first sample under one absorption process is obtained by the first expression of the above equation set; The first absorption coefficient of a transparent crystal during an absorption process is calculated based on the thickness and first transmittance of the two samples. hour The quantity is known; The thickness of the first sample is given, and the known quantity is given. This represents the total reflectance of the first sample during one absorption process. The intensity of the incident light; Let be the total transmittance of the second sample in one absorption process among the two samples corresponding to the transparent crystal. The first transmittance of the second sample is taken as the total transmittance of the second sample, which is a known quantity. The thickness of the second sample is a known quantity; The first reflectance of the second sample under one absorption process is obtained by the third expression of the above equation set; This represents the total reflectance of the second sample during one absorption process. When N=3, the total transmittance and total reflectance of the two samples mentioned above under the three absorption processes satisfy the following expressions: ; ; ; ; in, The total transmittance of the first sample in the three absorption processes is the same as the total transmittance of the first sample in one absorption process; The second reflectance of the first sample was calculated under three absorption processes, by combining... and Solve the corresponding expression; The second absorption coefficient, calculated for the first sample under three absorption processes, is obtained by combining... and Solve the corresponding expression; The total reflectance of the first sample under three absorption processes is the same as the total reflectance of the first sample under one absorption process. The total transmittance of the second sample in the three absorption processes is the same as the total transmittance of the second sample in one absorption process; The total reflectance of the second sample under three absorption processes is the same as the total reflectance of the second sample under one absorption process. The second reflectance of the second sample was calculated under the three absorption processes, by combining... and Solve the corresponding expression; The second absorption coefficient, calculated for the second sample under three absorption processes, is obtained by combining... and Solve the corresponding expression.

[0015] Another embodiment of the present invention provides a measuring device for the absorption coefficient of a transparent crystal. The device is used to implement the method for measuring the absorption coefficient of a transparent crystal as described above, and includes: The transmittance measurement module is used to measure the first transmittance of two samples with different thicknesses corresponding to the same type of transparent crystal under the first incident light. The first calculation module is used to calculate the first absorption coefficient of the transparent crystal and the first reflectance of each of the two samples under an absorption process based on the thickness difference between the two samples and the measured first transmittance. The second calculation module is used to calculate the second absorption coefficient and second reflectance of the two samples under N absorption processes, with the constraint that the total transmittance and total reflectance of the two samples remain unchanged under one or more absorption processes, based on the first absorption coefficient, the thickness of the two samples and the first transmittance of the samples, and N is an odd number greater than 1. The absorption coefficient determination module is used to analyze the variation law of absorption coefficient and reflectivity corresponding to different absorption processes. Based on the second absorption coefficient under the target absorption process, the absorption coefficient of the above transparent crystal at the wavelength corresponding to the first incident light is determined; where the target absorption process corresponds to a value of N.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: It provides a method and apparatus for measuring the absorption coefficient of a transparent crystal, which measures and calculates the first absorption coefficient and the first reflectance under one absorption process, and calculates the second absorption coefficient and the second reflectance under N absorption processes with the constraint that the total transmittance and total reflectance of the sample remain unchanged under different numbers of absorption processes. It analyzes the variation law of the absorption coefficient and reflectance, selects the absorption coefficient of a certain multi-absorption process to determine the absorption coefficient of the transparent crystal, thereby obtaining a more accurate absorption coefficient and improving the measurement efficiency, realizing a fast, relatively accurate and non-destructive measurement of the absorption coefficient of a transparent crystal. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating a method for measuring the absorption coefficient of a transparent crystal, as provided in an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of different absorption processes within a transparent crystal.

[0020] Figure 3 This is a schematic diagram showing the relationship between the first transmittance and the incident light wavelength of different samples of undoped gallium nitride crystals.

[0021] Figure 4 This is a schematic diagram showing the relationship between the first transmittance and the incident light wavelength for different samples of silicon-doped gallium nitride crystals.

[0022] Figure 5 This embodiment of the invention calculates the absorption coefficient of an undoped gallium nitride crystal at 201 wavelength positions from 400nm to 600nm based on a set ratio calculated using an undoped gallium nitride crystal sample 1 with a thickness of 0.03cm at 400nm. The result is shown in the diagram.

[0023] Figure 6 The present invention provides a schematic diagram showing the calculation results and the absorption coefficients of an undoped gallium nitride crystal at 201 wavelength positions from 400nm to 600nm, based on a set ratio calculated using an undoped gallium nitride crystal sample 2 with a thickness of 0.26cm at 400nm.

[0024] Figure 7 The present invention provides a schematic diagram showing the calculation results and the absorption coefficients of a silicon-doped gallium nitride crystal at 201 wavelength positions from 400 nm to 600 nm, based on a set ratio calculated using a silicon-doped gallium nitride crystal sample 1 with a thickness of 0.03 cm at 400 nm.

[0025] Figure 8 The present invention provides a schematic diagram showing the calculation results and the absorption coefficients of a silicon-doped gallium nitride crystal at 201 wavelength positions from 400nm to 600nm, based on a set ratio calculated using a silicon-doped gallium nitride crystal sample 2 with a thickness of 0.26cm at 400nm.

[0026] Figure 9 The graph shows the transmittance curves for three tests.

[0027] Figure 10 This is a schematic diagram illustrating the limit error of the arithmetic mean of transmittance.

[0028] Figure 11 This is a schematic diagram illustrating the error of the absorption coefficient.

[0029] Figure 12 A block diagram of a device for measuring the absorption coefficient of a transparent crystal provided in an embodiment of the present invention. Detailed Implementation

[0030] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0031] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0032] Furthermore, in the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "horizontal," "vertical," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0033] In the description of this specification, the references to terms such as "an embodiment," "a particular embodiment," or "the embodiment" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0034] Please see Figure 1 , Figure 1 The flowchart is a method for measuring the absorption coefficient of a transparent crystal provided in an embodiment of the present invention. The method for measuring the absorption coefficient of a transparent crystal includes steps S100-S400.

[0035] Step S100: Measure the first transmittance of two samples with different thicknesses corresponding to the same type of transparent crystal under the first incident light.

[0036] Step S200: Based on the thickness difference between the two samples and the two measured first transmittances, calculate the first absorption coefficient of the transparent crystal and the first reflectance of each of the two samples under an absorption process.

[0037] Step S300: With the constraint that the total transmittance and total reflectance of the two samples remain unchanged under one or more absorption processes, calculate the second absorption coefficient and second reflectance of the two samples under N absorption processes corresponding to at least one value of N, based on the first absorption coefficient, the first reflectance, the thickness of the two samples and the first transmittance of the samples, where N is an odd number greater than 1.

[0038] Step S400: Analyze the variation of absorption coefficient and reflectivity corresponding to different absorption processes, and determine the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light based on the second absorption coefficient under the target absorption process; wherein the target absorption process corresponds to a value of N.

[0039] The method for measuring the absorption coefficient of transparent crystals provided in this invention is used to measure the intrinsic absorption coefficient of transparent crystals. The absorption coefficient is an intrinsic parameter of a crystalline material; samples of different thicknesses have the same absorption coefficient. A transparent crystal refers to a solid material with a crystal lattice structure and optical transparency; this method can be applied to any crystal with a transmittance value.

[0040] For the same sample, multiple absorptions occur due to the repeated reflections of a single incident light within the sample. The number of times the absorbed light path passes through the thickness corresponds to the number of absorption processes. (See also...) Figure 2 An example is shown with an intensity of The absorption process of incident light within the sample, where the incident light travels from surface A to surface B (the opposite surface of surface A), and the reflectivity of the sample is denoted as . The absorption coefficient is denoted as The thickness is recorded as Incident light The absorption process within the sample is as follows.

[0041] (1) After the incident light is incident on surface A of the sample, the intensity is The light rays are reflected by surface A, with an intensity of The light rays passing through surface A, after being absorbed inside the sample, have an intensity of... The light reaches surface B of the sample with an intensity of The light rays are reflected by surface B, with an intensity of It passes through surface B and exits, thus completing an absorption process.

[0042] (2) Strength is After the light is reflected by surface B and absorbed inside the sample, its intensity is... The light reaches surface A of sample A with an intensity of The light rays are reflected by surface A, with an intensity of The light rays pass through surface A and are reflected by surface A. After being absorbed inside the sample, the intensity is... The light reaches surface B of the sample with an intensity of The light rays are reflected by surface B, with an intensity of It passes through surface B and exits, thus completing the three absorption processes.

[0043] (3) By analogy, we can obtain 5, 7, 9, 11, ... and other odd-numbered absorption processes.

[0044] The method for measuring the absorption coefficient of transparent crystals provided in this invention measures and calculates the first absorption coefficient and the first reflectance under one absorption process. With the constraint that the total transmittance and total reflectance of the sample remain unchanged under different numbers of absorption processes, the second absorption coefficient and the second reflectance under N absorption processes are calculated. The variation law of absorption coefficient and reflectance is analyzed, and the absorption coefficient of a certain multi-absorption process is selected to determine the absorption coefficient of the transparent crystal. This improves the accuracy and precision of absorption coefficient measurement and realizes rapid, accurate and non-destructive measurement of the absorption coefficient of transparent crystals.

[0045] In some embodiments, the transparent crystal includes a gallium nitride crystal, wherein the gallium nitride crystal is undoped gallium nitride or silicon-doped gallium nitride.

[0046] In step S100, the first incident light is incident on sample 1 (thickness denoted as ). Sample 1 and Sample 2 (thickness denoted as) The first transmittance of sample 1 was measured accordingly. and the first transmittance of sample 2 .

[0047] Taking undoped gallium nitride (GaN) crystals as an example, Sample 1 is a 1-inch undoped GaN crystal with a thickness of 300 μm and double-sided polishing, while Sample 2 is a 1-inch undoped GaN crystal with a thickness of 2600 μm and double-sided polishing. The relationship between the first transmittance of Sample 1 and Sample 2 and the incident light wavelength is as follows: Figure 3 As shown, the first transmittance of undoped gallium nitride crystal sample 1 is between 400 nm and 600 nm. The transmittance of sample 2, an undoped gallium nitride crystal, increases with increasing wavelength. The trend increases with increasing wavelength.

[0048] Taking silicon-doped gallium nitride (GaN) crystals as an example, Sample 1 is a 1-inch silicon-doped GaN crystal with a thickness of 300 μm and double-sided polishing, while Sample 2 is a 1-inch silicon-doped GaN crystal with a thickness of 2600 μm and double-sided polishing. The relationship between the first transmittance of Sample 1 and Sample 2 of the silicon-doped GaN crystals and the incident light wavelength is as follows: Figure 4 As shown, the first transmittance of sample 1, a silicon-doped gallium nitride crystal, is between 400 nm and 600 nm for incident light wavelengths. The first transmittance of sample 2, a silicon-doped gallium nitride crystal, increases with increasing wavelength. The trend increases with increasing wavelength.

[0049] contrast Figure 4 and Figure 3 It can be seen that, compared with silicon-doped gallium nitride crystals, undoped gallium nitride crystals have a higher first transmittance at each wavelength. Second transmittance The difference is relatively small. In this embodiment of the application, when selecting a sample corresponding to a transparent crystal for testing, the thickness difference range between the two samples to be tested can be adapted according to the type of transparent crystal (corresponding to the magnitude of the difference in transmittance under different thicknesses) to improve the accuracy of the calculated absorption coefficient.

[0050] The first absorption coefficient in step S200 is calculated as follows: based on the thickness d of the transparent crystal and the absorption coefficient... Relationship with reflectivity T Combined with parameters , , and The first absorption coefficient of the transparent crystal under one absorption process is calculated. In this embodiment, the absorption coefficients of the two samples corresponding to the transparent crystal under one absorption process are calculated using the same formula and described as the first absorption coefficient of the transparent crystal without distinguishing between different samples. For multiple absorption processes (e.g., three or five absorption processes), the calculated absorption coefficients for different samples may differ slightly. Therefore, the same parameter with different subscripts is used to indicate the results for different samples.

[0051] In a preferred embodiment, the first absorption coefficient of the transparent crystal during an absorption process satisfies the following expression: (1) in, The first absorption coefficient of a transparent crystal during an absorption process. and The thicknesses of two samples of the same type of transparent crystal with different thicknesses, for example... < , For thickness is The first transmittance of the sample, For thickness is The first transmittance of the sample. Preferably, the first transmittance is the result of a single measurement or the average transmittance of multiple measurements. This is achieved by adjusting the relative ratio of the difference in transmittance between the two samples to the difference in their thicknesses: the thickness difference between the two samples... The larger the value, and / or the more significant the difference in the first transmittance between the two samples, the better the calculated first absorption coefficient. The higher the accuracy.

[0052] In a preferred embodiment, when the first absorption coefficient is obtained based on the above formula (1), the first reflectance of the transparent crystal under one absorption process is calculated in the following way: the two first transmittances are respectively used as the total transmittance of each sample. For each sample, the first reflectance of the current sample under one absorption process is calculated according to the first absorption coefficient, the thickness of the current sample and the corresponding first transmittance, so as to obtain the first reflectance of each of the two samples.

[0053] For the first of the two samples corresponding to the transparent crystal, the formula for calculating the first reflectance is as follows (2-1); for the second sample, the formula for calculating the first reflectance is as follows (2-3).

[0054] In some embodiments, the total transmittance and total reflectance of the two samples under one absorption process satisfy the following set of equations: (2-1) (2-2) (2-3) (2-4) in, For the two samples corresponding to the transparent crystal, the first sample has the total transmittance during one absorption process, and the first transmittance of the first sample (e.g., The total transmittance corresponding to the first sample is a known quantity measured. The first reflectance of the first sample under the first absorption process is calculated using the first expression (2-1) of the above equation set. and Substituting into the second expression (2-2), we get ; The first absorption coefficient of the transparent crystal under an absorption process is calculated based on the thickness and first transmittance of the two samples (formula (1) above). hour The quantity is known; The thickness of the first sample is given, and the known quantity is given. This represents the total reflectance of the first sample during one absorption process. The intensity of the incident light; For the two samples corresponding to the transparent crystal, the total transmittance of the second sample under one absorption process is given by the first transmittance of the second sample (e.g., The total transmittance corresponding to the second sample is a known quantity. The thickness of the second sample is a known quantity; The first reflectance of the second sample under one absorption process is calculated using the third expression (2-3) of the above equation set. and Substituting into the fourth expression (2-4), we get ; This represents the total reflectance of the second sample during one absorption process.

[0055] The calculation process for the first reflectance of the two samples and the total reflectance of the two samples under one absorption process is shown in steps 1-3.

[0056] Step 1: First, measure the transmittance of two samples of different thicknesses at a certain wavelength. and and thickness value and Substituting into expression (1), the first absorption coefficient of the transparent crystal under an absorption process is calculated. .

[0057] Step 2, for a thickness of The sample: As The result obtained in step 1 and known , and Substituting into expression (2-1), the thickness is obtained as The first reflectance of the sample .

[0058] For a thickness of The sample: As The result obtained in step 1 and known , and Substituting into expression (2-3), the thickness is obtained as The first reflectance of the sample The first reflectance of the two samples and It depends on the polishing state of the sample surface, and the two are not necessarily equal.

[0059] Step 3, for a thickness of The sample: the obtained , and known and Substituting into expression (2-2), the thickness is obtained as The total reflectance of the sample during an absorption process .

[0060] For a thickness of The sample: the obtained , and known and Substituting into expression (2-4), the thickness is obtained as The total reflectance of the sample during an absorption process .

[0061] In a preferred embodiment, step S300 specifically includes: calculating the total reflectance of each sample based on the first reflectance, the first absorption coefficient, and the thickness of each of the two samples (corresponding to the previous formulas (2-2) and (2-4)); with the constraint that the total transmittance and total reflectance of the two samples remain unchanged under one or more absorption processes, calculating the second absorption coefficient and second reflectance of the two samples under at least one N value corresponding to N absorption processes based on the total transmittance, total reflectance, and the thickness of each of the two samples.

[0062] Preferably, when N=3, the total transmittance and total reflectance of the two samples under the three absorption processes satisfy the following expressions: (3-1) (3-2) (3-3) (3-4) in, The total transmittance of the first sample (e.g., sample 1) in the three absorption processes is the same as the total transmittance of the first sample in one absorption process. The second reflectance of the first sample was calculated under three absorption processes, by combining... and Solve the corresponding expressions (3-1) and (3-2); The second absorption coefficient, calculated for the first sample under three absorption processes, is obtained by combining... and Solve the corresponding expressions (3-1) and (3-2); The total reflectance of the first sample under three absorption processes is the same as the total reflectance of the first sample under one absorption process. The total transmittance of the second sample (e.g., sample 2) in three absorption processes is the same as the total transmittance of the second sample in one absorption process. The total reflectance of the second sample under three absorption processes is the same as the total reflectance of the second sample under one absorption process. The second reflectance of the second sample was calculated under the three absorption processes, by combining... and Solve the corresponding expressions (3-3) and (3-4); The second absorption coefficient, calculated for the second sample under three absorption processes, is obtained by combining... and Solve the corresponding expressions (3-3) and (3-4).

[0063] Preferably, when N=5, the total transmittance and total reflectance of the two samples under the five absorption processes satisfy the following expressions: (4-1) (4-2) (4-3) (4-4) in, The total transmittance of the first sample (e.g., sample 1) in five absorption processes is the same as the total transmittance of the first sample in one absorption process. The second reflectance of the first sample was calculated under five absorption processes, by combining... and Solve the corresponding expressions (4-1) and (4-2); The second absorption coefficient, calculated for the first sample under five absorption processes, is obtained by combining... and Solve the corresponding expressions (4-1) and (4-2); The total reflectance of the first sample under five absorption processes is the same as the total reflectance of the first sample under one absorption process. The total transmittance of the second sample (e.g., sample 2) in five absorption processes is the same as the total transmittance of the second sample in one absorption process. The total reflectance of the second sample under five absorption processes is the same as the total reflectance of the second sample under one absorption process. The second reflectance of the second sample was calculated under five absorption processes, by combining... and Solve the corresponding expressions (4-3) and (4-4); The second absorption coefficient, calculated for the second sample under five absorption processes, is obtained by combining... and Solve the corresponding expressions (4-3) and (4-4).

[0064] Similarly, when N=7, 9, 11, ... and other odd numbers, we can obtain the expressions that the total transmittance and total reflectance of the two samples under N absorption processes are respectively satisfied. Based on the above expressions, we can calculate the second absorption coefficient and second reflectance of the two samples under multiple absorption processes.

[0065] In a preferred embodiment, step S400 specifically includes: analyzing the variation patterns of absorption coefficient and reflectance corresponding to different absorption processes; when the variation values ​​of absorption coefficients corresponding to M absorption processes and M+2 absorption processes (i.e., the difference between the calculation results corresponding to M absorption processes and M+2 absorption processes is very small) are less than a first set threshold, and the variation value of reflectance is less than a second set threshold, the M absorption processes or M+2 absorption processes are determined as target absorption processes; where M+2 is a value of N; and the absorption coefficient of the transparent crystal at the first incident light wavelength is determined according to the second absorption coefficient under the target absorption process.

[0066] Generally, the larger M is, the smaller the changes in absorption coefficient and reflectance for the M and M+2 absorption processes. The final value of M can be the smallest M that satisfies the condition that the changes in absorption coefficient for the M and M+2 absorption processes are less than a first set threshold, and the changes in reflectance are less than a second set threshold. Taking M=3 as an example, the changes in absorption coefficient for the three and five absorption processes are less than the first set threshold, and the changes in reflectance are less than the second set threshold. Based on the second absorption coefficient of transparent crystal sample 1 / sample 2 under the three absorption processes... / Or the second absorption coefficient of a transparent crystal under five absorption processes / Determine the absorption coefficient of the transparent crystal at the wavelength of the first incident light. " / " indicates "or".

[0067] In some embodiments, for gallium nitride crystals, the value of N corresponding to the target absorption process is 3. In step S400, the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light is determined based on the second absorption coefficient under the three absorption processes.

[0068] Taking undoped gallium nitride crystals as transparent crystals, with sample thicknesses of 0.03 cm and 0.26 cm, and an incident light wavelength of 400 nm as examples, the influence of the number of absorption processes on the absorption coefficient is analyzed. For the 0.03 cm thick undoped gallium nitride crystal sample, the influence of the number of absorption processes on the absorption coefficient under 400 nm incident light is shown in Table 1; for the 0.26 cm thick undoped gallium nitride crystal sample, the influence of the number of absorption processes on the absorption coefficient under 400 nm incident light is shown in Table 2.

[0069] In the table below, Asum% = 1 - Total Transmittance - Total Reflectance; ; ; ; ; ; ; ; ; .

[0070] Table 1. Absorption coefficients and related parameters of undoped gallium nitride crystal sample 1 under 400 nm incident light for different absorption processes.

[0071] Referring to Table 1, it can be seen that for an undoped gallium nitride crystal with a thickness of 0.03 cm (i.e., sample 1), the changes in absorption coefficient and reflectivity for one and three absorption processes are 0.0145 and 0.0051, respectively, both of which are relatively large. The changes in absorption coefficient and reflectivity for three and five absorption processes are 0.0006 and 0.0001, respectively, which are significantly reduced and close to 0, and are less than the corresponding set thresholds. Therefore, the absorption coefficients corresponding to three or five absorption processes can be used as the second absorption coefficients under the target absorption process.

[0072] Table 2. Absorption coefficients and related parameters of undoped gallium nitride crystal sample 2 under 400nm incident light for different absorption processes.

[0073] Referring to Table 2, it can be seen that for an undoped gallium nitride crystal with a thickness of 0.26 cm, the changes in absorption coefficient and reflectivity for one and three absorption processes are 0.0146 and 0.0050, respectively, both of which are relatively large. However, the changes in absorption coefficient and reflectivity for three and five absorption processes are 0.0006 and 0.0002, respectively, which are significantly reduced and close to 0, and are less than the corresponding set thresholds. Therefore, the absorption coefficients corresponding to three or five absorption processes can be used as the second absorption coefficients under the target absorption process.

[0074] Taking silicon-doped gallium nitride (GaN) crystals with transparent crystal thicknesses of 0.03 cm and 0.26 cm, and an incident light wavelength of 400 nm as examples, the influence of the number of absorption processes on the absorption coefficient is analyzed. For the 0.03 cm thick GaN crystal sample, the influence of the number of absorption processes on the absorption coefficient under 400 nm incident light is shown in Table 3; for the 0.26 cm thick GaN crystal sample, the influence of the number of absorption processes on the absorption coefficient under 400 nm incident light is shown in Table 4.

[0075] Table 3. Absorption coefficients and related parameters of silicon-doped gallium nitride crystal sample 1 under 400 nm incident light for different absorption processes. parameter One absorption process 3 absorption processes 5 absorption processes Incident light intensity 1 1 1 reflectivity 0.179 0.1946 0.1952 absorption coefficient 0.335 0.2773 0.2754 Sample thickness 0.03 0.03 0.03 Total transmittance 66.73% 66.73% 66.73% Total reflectance 32.45% 32.45% 32.45% Asum% 0.82% 0.82% 0.82% Ra 17.90% 19.46% 19.52% Rb 14.55% Rc 12.41% 12.44% Rd 0.58% Re 0.47% Rf 0.02% Ta 64.23% Tc 66.73% 64.33% 2.41% Te 2.40% 0.09%

[0076] Referring to Table 3, it can be seen that for a silicon-doped gallium nitride crystal with a thickness of 0.03 cm, the changes in absorption coefficient and reflectivity for one and three absorption processes are both relatively large (0.0577 and 0.0577 respectively). However, the changes in absorption coefficient and reflectivity for three and five absorption processes are significantly smaller and close to zero, which is less than the corresponding set threshold. Therefore, the absorption coefficients corresponding to three or five absorption processes can be used as the second absorption coefficient under the target absorption process.

[0077] Table 4. Absorption coefficients and related parameters of silicon-doped gallium nitride crystal sample 2 under 400 nm incident light for different absorption processes. parameter One absorption process 3 absorption processes 5 absorption processes Incident light intensity 1 1 1 reflectivity 0.1785 0.1978 0.1986 absorption coefficient 0.335 0.2797 0.2780 Sample thickness 0.26 0.26 0.26 Total transmittance 61.86% 61.86% 61.86% Total reflectance 31.29% 31.29% 31.29% Asum% 6.85% 6.85% 6.85% Ra 17.85% 19.78% 19.86% Rb 13.44% Rc 11.01% 11.04% Rd 0.50% Re 0.38% Rf 0.02% Ta 61.86% 59.84% 59.75% Tc 2.02% 2.04% Te 0.07%

[0078] Referring to Table 4, it can be seen that for a silicon-doped gallium nitride crystal with a thickness of 0.26 cm, the changes in absorption coefficient and reflectivity for one and three absorption processes are 0.0202 and 0.0553, respectively, both of which are relatively large. The changes in absorption coefficient and reflectivity for three and five absorption processes are 0.0008 and 0.0017, respectively, which are significantly reduced and close to 0, and are less than the corresponding set threshold. Therefore, the absorption coefficient corresponding to three absorption processes is taken as the second absorption coefficient under the target absorption process.

[0079] In a preferred embodiment, the method further includes the steps S1-S4.

[0080] Step S1: Measure the second transmittance of two samples with different thicknesses corresponding to the transparent crystal under the second incident light. The wavelength of the second incident light is different from the wavelength of the first incident light.

[0081] Step S2: Calculate the third absorption coefficient of the transparent crystal under an absorption process based on the thickness difference between the two samples and the two measured second transmittances.

[0082] Step S3: Calculate the product of the third absorption coefficient and the set ratio. The set ratio is equal to the ratio of the second absorption coefficient to the first absorption coefficient under the target absorption process.

[0083] Step S4: Determine the absorption coefficient of the transparent crystal at the wavelength corresponding to the second incident light based on the product.

[0084] The sample used in step S1 can be the sample used in step S100, or it can be a sample of the same type of crystal with a different thickness. Preferably, the second transmittance is the result of a single measurement or the average transmittance of multiple measurements.

[0085] The principle of calculating the third absorption coefficient of a transparent crystal under an absorption process in step S2 is the same as the principle of calculating the first absorption coefficient of a transparent crystal under an absorption process in step S200, and will not be repeated here.

[0086] In step S3, the set ratio can be obtained by calculating the ratio between the second absorption coefficient and the first absorption coefficient under the target absorption process based on sample 1, or by calculating the ratio between the second absorption coefficient and the first absorption coefficient under the target absorption process based on sample 2.

[0087] Preferably, the wavelength range of the incident light is 400 nm to 600 nm. This method can measure the absorption coefficient of transparent crystals in the 400 nm to 600 nm wavelength range.

[0088] In a first preferred embodiment, step S400, determining the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light based on the second absorption coefficient under the target absorption process, includes: determining the second absorption coefficient under the target absorption process as the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light. Step S4, determining the absorption coefficient of the transparent crystal at the wavelength corresponding to the second incident light based on the product of the third absorption coefficient and a set ratio, includes: determining the product of the third absorption coefficient and a set ratio as the absorption coefficient of the transparent crystal at the wavelength corresponding to the second incident light.

[0089] In the first preferred embodiment, the second absorption coefficient is directly used as the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light, and the product of the third absorption coefficient and a set ratio is used as the absorption coefficient of the transparent crystal at the wavelength corresponding to the second incident light.

[0090] In the second preferred embodiment, step S400 and the method for determining the absorption coefficient of the transparent crystal in step S4 include: measuring the error using a preset absorption coefficient. right Error correction is performed, whereby... For the transparent crystal before error correction at wavelength The absorption coefficient was determined at a specific wavelength; the error correction result was used as the absorption coefficient of the transparent crystal at a specific wavelength. The final absorption coefficient at the point, with error correction result as follows: Values ​​within a range; wavelength It includes at least one wavelength corresponding to the first incident light and a wavelength corresponding to the second incident light.

[0091] In the second preferred embodiment, the error is measured using a preset absorption coefficient. Error corrections were performed on the second and third absorption coefficients, and the resulting error corrections were used as the absorption coefficients of the transparent crystal at the wavelengths corresponding to the first and second incident light, respectively.

[0092] Preferably, the preset absorption coefficient measurement error The transmittance of any transparent crystal sample under the same incident light was determined by measuring it multiple times and calculating the average transmittance. ; Calculate the mean transmittance Limit error Based on the functional relationship between transmittance, thickness of transparent crystal sample, and absorption coefficient, the first limiting transmittance is calculated respectively. Second limit transmittance The corresponding absorption coefficient; based on the first limiting transmittance Second limit transmittance The difference in the corresponding absorption coefficients is determined. Further preferably, when the number of measurements is less than a set value, the limit error for calculating the average transmittance is... Specifically, this includes: the limiting error in calculating the mean transmittance according to the t-distribution. .

[0093] Preferred, It is half the difference in absorption coefficients, expressed as follows: (5) in, First limiting transmittance The corresponding absorption coefficient, Second limiting transmittance The corresponding absorption coefficient.

[0094] Figure 5 This embodiment of the invention calculates the absorption coefficient of an undoped gallium nitride crystal at 201 wavelength positions from 400nm to 600nm based on a set ratio calculated using an undoped gallium nitride crystal sample 1 with a thickness of 0.03cm at 400nm. The result is shown in the diagram. Figure 6 The present invention provides a schematic diagram showing the calculation results and the absorption coefficients of an undoped gallium nitride crystal at 201 wavelength positions from 400nm to 600nm, based on a set ratio calculated using an undoped gallium nitride crystal sample 2 with a thickness of 0.26cm at 400nm.

[0095] In an exemplary embodiment, for two undoped gallium nitride crystal samples 1 and 2 of different thicknesses, the above steps S100~S400 and S1~S4 are performed at wavelengths of 400nm, 401nm, 402nm, ..., 600nm, corresponding to 1nm intervals from 400nm to 600nm, respectively. This yields 201 values ​​for the first transmittance T1 and T2. Since the thicknesses d1 and d2 of the two samples are known, the 201 values ​​can be obtained using the above formula (1). The value of .

[0096] Subsequently, calculations show that the ratio of the absorption coefficients corresponding to multiple absorption processes to that corresponding to one absorption process in sample 1 (thickness 0.03 cm) at a wavelength of 400 nm can be obtained. The calculations show that A (absorption coefficients calculated from three absorption processes / absorption coefficients calculated from one absorption process) ≈ B (absorption coefficients calculated from five absorption processes / absorption coefficients calculated from one absorption process). Therefore, calculating only three absorption processes is sufficient to meet the accuracy requirements for calculating the absorption coefficient of transparent crystals. Here, the value of A corresponding to undoped gallium nitride crystal sample 1 is used as the set ratio. Similarly, the set ratio can also be calculated based on undoped gallium nitride crystal sample 2.

[0097] Therefore, the true absorption coefficient values ​​of the final undoped gallium nitride crystal at various wavelengths within the 400nm~600nm range were obtained using the 201 values ​​calculated earlier. Multiplying each value by a set ratio A yields the absorption coefficient values ​​for each wavelength. See [link to relevant documentation]. Figure 5 The black data points are shown in the middle.

[0098] Furthermore, due to the existence of various errors, and considering that the limiting errors for each wavelength have already been calculated, these are superimposed to obtain an interval value for the absorption coefficient at each wavelength, i.e., the corresponding... Figure 5 The red line segment indicates the fluctuation range.

[0099] Reference Figure 6 As shown, with Figure 5 The difference lies in the fact that the set ratio is calculated based on the undoped gallium nitride crystal sample 2 with a thickness of 0.26 cm at 400 nm. Then, the absorption coefficient of the undoped gallium nitride crystal at 201 wavelength positions from 400 nm to 600 nm and the results of the range are obtained.

[0100] Reference Figure 7 As shown, with Figure 5 The difference lies in the fact that the set ratio is calculated based on a silicon-doped gallium nitride crystal sample 1 with a thickness of 0.03 cm at 400 nm. Then, the absorption coefficient of the undoped gallium nitride crystal at 201 wavelength positions from 400 nm to 600 nm and the results of the range are obtained.

[0101] Reference Figure 8 As shown, with Figure 5 The difference lies in the fact that the set ratio is calculated based on a silicon-doped gallium nitride crystal sample 2 with a thickness of 0.26 cm at 400 nm. Then, the absorption coefficient of the undoped gallium nitride crystal at 201 wavelength positions from 400 nm to 600 nm and the results of the range are obtained.

[0102] In some embodiments, taking the number of measurements being less than three times as an example, the following explanation is provided. The calculation process involves taking samples of the same known thickness repeatedly, ensuring the same light incident point as much as possible, and repeating the test three times to obtain three different transmittance values. Figure 9 The transmittance curves for three tests are shown. The arithmetic mean of the three tests is calculated. and standard deviation Calculate the standard deviation of the arithmetic mean. The limit error of calculating the arithmetic mean according to the t-distribution. ,in, The confidence coefficient can be obtained from the table. , Figure 10 The limit error of the arithmetic mean is shown. According to... Calculate separately , absorption coefficient at time , ,but , Figure 11 The error in the absorption coefficient is shown.

[0103] In a preferred embodiment, the method for measuring the absorption coefficient of a transparent crystal further includes: selecting one sample from two samples with different thicknesses and a third sample with a thickness difference, or for another set of two samples with different thicknesses, calculating the verification absorption coefficient at the wavelength corresponding to the first incident light, verifying the second absorption coefficient under the target absorption process based on the verification absorption coefficient, and outputting the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light after the verification is passed.

[0104] Please see Figure 12 , Figure 12 This is a block diagram of a transparent crystal absorption coefficient measuring device 100 provided in an embodiment of the present invention. The transparent crystal absorption coefficient measuring device 100 includes a transmittance measuring module 110, a first calculation module 120, a second calculation module 130, and an absorption coefficient determining module 140.

[0105] Transmittance measurement module 110, for example, performs step S100 to measure the first transmittance of two samples with different thicknesses corresponding to the same type of transparent crystal under the first incident light.

[0106] For example, the first calculation module 120 executes step S200 to calculate the first absorption coefficient of the transparent crystal and the first reflectance of each of the two samples under an absorption process based on the thickness difference between the two samples and the two measured first transmittances.

[0107] For example, the second calculation module 130 executes step S300, which is used to calculate the second absorption coefficient and the second reflectance of the two samples under N absorption processes, based on the first absorption coefficient, the thickness of the two samples and the first transmittance of the samples, with N being an odd number greater than 1, under the constraint that the total transmittance and total reflectance of the two samples remain unchanged under one or more absorption processes.

[0108] The absorption coefficient determination module 140, for example, executes step S400 to analyze the variation law of absorption coefficient and reflectivity corresponding to different absorption processes, and determines the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light based on the second absorption coefficient under the target absorption process; wherein the target absorption process corresponds to a value of N.

[0109] The transparent crystal absorption coefficient measuring device 100 is used to implement the above-described transparent crystal absorption coefficient measuring method. Further functional descriptions of the above modules are the same as those in the corresponding method embodiments described above, and will not be repeated here.

[0110] In some embodiments, the transmittance measurement module 110, the first calculation module 120, the second calculation module 130, and the absorption coefficient determination module 140 in the above-described measuring device 100 are also used to perform the above-described steps S1 to S4.

[0111] Specifically, the transmittance measurement module 110 is also used to: measure the second transmittance of two samples with different thicknesses corresponding to the transparent crystal under the second incident light, wherein the wavelength of the second incident light is different from the wavelength of the first incident light.

[0112] The first calculation module 120 is further configured to: calculate the third absorption coefficient of the transparent crystal under an absorption process based on the thickness difference between the two samples and the two measured second transmittances.

[0113] The second calculation module 130 is further configured to: calculate the product of the third absorption coefficient and the set ratio, wherein the set ratio is equal to the ratio of the second absorption coefficient to the first absorption coefficient under the target absorption process.

[0114] The absorption coefficient determination module 140 is further configured to: determine the absorption coefficient of the transparent crystal at the wavelength corresponding to the second incident light based on the product.

[0115] In some embodiments, the measuring device 100 is further configured to: select one sample from the two samples with different thicknesses and a third sample with a thickness difference, or for another set of two samples with different thicknesses, calculate the verification absorption coefficient at the wavelength corresponding to the first incident light, verify the second absorption coefficient under the target absorption process based on the verification absorption coefficient, and output the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light after the verification is passed.

[0116] The implementation details of each functional module in the above-mentioned measuring device 100, or the corresponding functional modules or sub-modules that may be included, can be found in the relevant description of the above-mentioned measuring method, and will not be repeated here.

[0117] The method and apparatus for measuring the absorption coefficient of transparent crystals provided in this invention measure the transmittance and thickness of two identical transparent crystal samples of different thicknesses during one absorption process. The absorption coefficient and reflectance are calculated for that absorption process. With the constraint that the total transmittance and total reflectance of the samples remain constant across different numbers of absorption processes, the absorption coefficient and reflectance are calculated for N absorption processes. The variation patterns of the absorption coefficient and reflectance are analyzed, and the absorption coefficient of a specific multi-absorption process is selected to determine the absorption coefficient of the transparent crystal. This yields a more accurate absorption coefficient and improves measurement efficiency, achieving rapid, relatively accurate, and non-destructive measurement of the absorption coefficient of transparent crystals. Furthermore, measurement errors are considered, and an absorption coefficient measurement error correction is designed to correct the initially determined absorption coefficient, further improving the accuracy of the absorption coefficient measurement. When measuring the absorption coefficient at other wavelengths, the absorption coefficient measured during one absorption process is directly multiplied by a set ratio to obtain the absorption coefficient at that other wavelength, further improving measurement efficiency.

[0118] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for measuring the absorption coefficient of a transparent crystal, characterized in that, include: The first transmittance of two samples with different thicknesses corresponding to the same type of transparent crystal under the first incident light was measured respectively. Based on the thickness difference between the two samples and the measured first transmittance, calculate the first absorption coefficient of the transparent crystal and the first reflectance of each of the two samples during an absorption process. With the constraint that the total transmittance and total reflectance of the two samples remain constant under one or more absorption processes, the second absorption coefficient and second reflectance of the two samples under N absorption processes corresponding to at least one value of N are calculated based on the first absorption coefficient, the thickness of the two samples and the first transmittance of the samples, where N is an odd number greater than 1. Analyze the variation patterns of absorption coefficient and reflectance corresponding to different absorption processes, and determine the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light based on the second absorption coefficient under the target absorption process. The target absorption process corresponds to one of the values ​​of N.

2. The measurement method according to claim 1, characterized in that, The first reflectivity is calculated as follows: The two first transmittances are respectively used as the total transmittance of each sample. For each sample, the first reflectance of the current sample under one absorption process is calculated based on the first absorption coefficient, the thickness of the current sample and the corresponding first transmittance, so as to obtain the first reflectance of each of the two samples. Wherein, with the constraint that the total transmittance and total reflectance of the two samples remain constant under one or more absorption processes, based on the first absorption coefficient, the thickness of each of the two samples, and their respective first transmittance, the second absorption coefficient and second reflectance of the two samples under at least N absorption processes corresponding to at least one value of N are calculated, including: Calculate the total reflectance of each sample based on its first reflectance, first absorption coefficient, and thickness. With the constraint that the total transmittance and total reflectance of the two samples remain constant under one or more absorption processes, the second absorption coefficient and second reflectance of the two samples under N absorption processes corresponding to at least one value of N are calculated based on the total transmittance, the total reflectance, and the thickness of the two samples.

3. The measurement method according to claim 1, characterized in that, Analyze the variation patterns of absorption coefficient and reflectivity corresponding to different absorption processes, and determine the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light based on the second absorption coefficient under the target absorption process, including: Analyze the variation patterns of absorption coefficient and reflectance corresponding to different absorption processes. If the variation values ​​of absorption coefficient for M absorption processes and M+2 absorption processes are less than a first set threshold and the variation value of reflectance is less than a second set threshold, then the M absorption processes or M+2 absorption processes are determined as target absorption processes; where M+2 is a value of N. The absorption coefficient of the transparent crystal at the first incident light wavelength is determined based on the second absorption coefficient under the target absorption process.

4. The measurement method according to claim 1, characterized in that, Also includes: The second transmittance of two samples with different thicknesses corresponding to the transparent crystal under the second incident light was measured respectively, wherein the wavelength of the second incident light was different from the wavelength of the first incident light; Based on the thickness difference between the two samples and the two measured second transmittances, the third absorption coefficient of the transparent crystal under an absorption process is calculated. Calculate the product of the third absorption coefficient and the set ratio, where the set ratio is equal to the ratio of the second absorption coefficient to the first absorption coefficient under the target absorption process; The absorption coefficient of the transparent crystal at the wavelength corresponding to the second incident light is determined based on the product.

5. The measurement method according to any one of claims 1-4, characterized in that, Determining the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light based on the second absorption coefficient under the target absorption process includes one of the following: The second absorption coefficient under the target absorption process is determined as the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light; or... The second absorption coefficient under the target absorption process is determined as the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light; the product is determined as the absorption coefficient of the transparent crystal at the wavelength corresponding to the second incident light; or... Error measurement using a preset absorption coefficient right Error correction is performed, among which, The transparent crystal before error correction at wavelength The absorption coefficient was determined at a specific wavelength; the error correction result was used as the absorption coefficient of the transparent crystal at a specific wavelength. The final absorption coefficient at the point, the error correction result is Values ​​within the range; the wavelength It includes at least one wavelength corresponding to the first incident light and a wavelength corresponding to the second incident light.

6. The measurement method according to claim 5, characterized in that, Also includes: The transmittance of any transparent crystal sample under the same incident light was measured multiple times, and the average transmittance was calculated. Wherein, the first transmittance is the average transmittance obtained from multiple measurements; optionally, the second transmittance is the average transmittance obtained from multiple measurements. Calculate the mean transmittance Limit error ; Based on the functional relationship between transmittance, thickness of transparent crystal sample, and absorption coefficient, the first limiting transmittance is calculated respectively. Second limit transmittance The corresponding absorption coefficient; Based on the first limiting transmittance Second limit transmittance The difference in the corresponding absorption coefficients is determined. ; Optional, It is half of the difference in absorption coefficients, expressed as follows: ； in, First limiting transmittance The corresponding absorption coefficient, Second limiting transmittance The corresponding absorption coefficient; Optionally, when the number of measurements is less than a set value, the limit error of the average transmittance is calculated. Specifically, this includes: the limiting error in calculating the mean transmittance according to the t-distribution. .

7. The measurement method according to any one of claims 1-4, characterized in that, The first absorption coefficient of the transparent crystal under an absorption process satisfies the following expression: ； in, The first absorption coefficient of a transparent crystal during an absorption process. and The thicknesses are those of two samples of the same type of transparent crystal but with different thicknesses. For thickness is The first transmittance of the sample, For thickness is The first transmittance of the sample, which is the result of a single measurement or the average transmittance of multiple measurements; Optionally, one of the two samples with different thicknesses can be selected and a third sample with a different thickness can be selected, or for another set of two samples with different thicknesses, the verification absorption coefficient at the wavelength corresponding to the first incident light can be calculated. Based on the verification absorption coefficient, the second absorption coefficient under the target absorption process can be verified. After the verification is passed, the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light can be output.

8. The measurement method according to any one of claims 1-4, characterized in that, The transparent crystal includes: a gallium nitride crystal, wherein the gallium nitride crystal is undoped gallium nitride or silicon-doped gallium nitride; Optionally, the wavelength range of the incident light is 400nm~600nm; Optionally, for gallium nitride crystals, the value of N corresponding to the target absorption process is 3.

9. The measurement method according to any one of claims 1-4, characterized in that, The total transmittance and total reflectance of the two samples under one absorption process satisfy the following set of equations: ； ； ； ； in, The total transmittance of the first sample in one absorption process is the first transmittance of the first sample, which is a known quantity for measurement. The first reflectance of the first sample under one absorption process is obtained by the first expression of the above equation set; The first absorption coefficient of a transparent crystal during an absorption process is calculated based on the thickness and first transmittance of the two samples. hour The quantity is known; The thickness of the first sample is given, and the known quantity is given. This represents the total reflectance of the first sample during one absorption process. The intensity of the incident light; Let be the total transmittance of the second sample in one absorption process among the two samples corresponding to the transparent crystal. The first transmittance of the second sample is taken as the total transmittance of the second sample, which is a known quantity. The thickness of the second sample is a known quantity; The first reflectance of the second sample under one absorption process is obtained by the third expression of the above equation set; This represents the total reflectance of the second sample during one absorption process. When N=3, the total transmittance and total reflectance of the two samples under the three absorption processes satisfy the following expressions: ； ； ； ； in, The total transmittance of the first sample in the three absorption processes is the same as the total transmittance of the first sample in one absorption process; The second reflectance of the first sample was calculated under three absorption processes, by combining... and Solve the corresponding expression; The second absorption coefficient, calculated for the first sample under three absorption processes, is obtained by combining... and Solve the corresponding expression; The total reflectance of the first sample under three absorption processes is the same as the total reflectance of the first sample under one absorption process. The total transmittance of the second sample in the three absorption processes is the same as the total transmittance of the second sample in one absorption process; The total reflectance of the second sample under three absorption processes is the same as the total reflectance of the second sample under one absorption process. The second reflectance of the second sample was calculated under the three absorption processes, by combining... and Solve the corresponding expression; The second absorption coefficient, calculated for the second sample under three absorption processes, is obtained by combining... and Solve the corresponding expression.

10. A device for measuring the absorption coefficient of a transparent crystal, characterized in that, The apparatus is used to implement the method for measuring the absorption coefficient of a transparent crystal as described in any one of claims 1-9, comprising: The transmittance measurement module is used to measure the first transmittance of two samples with different thicknesses corresponding to the same type of transparent crystal under the first incident light. The first calculation module is used to calculate the first absorption coefficient of the transparent crystal and the first reflectance of each of the two samples under an absorption process, based on the thickness difference between the two samples and the measured first transmittance. The second calculation module is used to calculate the second absorption coefficient and second reflectance of the two samples under at least N absorption processes, based on the first absorption coefficient, the thickness of the two samples and the first transmittance of the samples, with N being an odd number greater than 1, under the constraint that the total transmittance and total reflectance of the two samples remain unchanged under one or more absorption processes. The absorption coefficient determination module is used to analyze the variation law of absorption coefficient and reflectivity corresponding to different absorption processes, and to determine the absorption coefficient of the transparent crystal at the wavelength corresponding to the first incident light based on the second absorption coefficient under the target absorption process; wherein the target absorption process corresponds to a value of N.

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