Method for accurate measurement of ion exchange refractive index

Abstract

The application discloses a kind of accurate measurement methods of ion exchange refractive index, by making test device, and the corresponding wavelength scanning diagram can be calculated out the refractive index of the wafer where the device is, it is convenient to measure and calculate the refractive index of other devices on the wafer, relative to traditional refractive index measurement method, the measurement method uses spectrometer to measure, the precision of the used spectrometer is 0.1nm, rely on the accuracy of spectrometer, can accurately obtain the effective refractive index after ion exchange is completed, has very high reference significance to other devices under this process, it is convenient for subsequent design optimization improvement.

Description

Technical Field

[0001] This invention belongs to the field of optical technology, specifically, it relates to a method for accurately measuring ion-exchange refractive index. Background Technology

[0002] Existing ion exchange technologies mostly use prism scanning methods to measure refractive index, which has certain limitations in measurement range and cannot test higher refractive indices, hindering the exploration and improvement of actual production processes. Based on this situation, there is a need for a refractive index testing method with a larger measurement range and more accurate measurement results. In order to solve the above problems and further expand the application scenarios of ion exchange methods, this invention proposes the following solutions. Summary of the Invention

[0003] The purpose of this invention is to provide a precise method for measuring ion-exchange refractive index, which solves the problem that the existing prism scanning method for measuring refractive index has certain limitations in measurement range and cannot test higher refractive indices.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A precise method for measuring ion-exchange refractive index, comprising:

[0006] The first step is to transfer the pattern on the photomask onto the glass substrate using photolithography.

[0007] The second step involves exchanging the required test devices based on the photolithographic pattern using an ion exchange process.

[0008] The test device includes a curved waveguide and a straight waveguide arranged side by side, wherein the length of the straight waveguide is a fixed value;

[0009] The third step is to perform light scanning based on a spectrometer and a broadband light source. This involves connecting the input end of the test device to a broadband light source and the output end to a spectrometer via a coupled light method. This completes the wavelength scan of the device, obtaining the output optical power at different light wavelengths, and thus the effective refractive index of the test device.

[0010] As a further aspect of the present invention, in the third step, the input end of the test device divides the input light into two parts with equal energy through a Y-brancher. The two parts of the light field are represented as E1=E2=0.5*sin x, where the total energy of the input light is, one part of the light is transmitted through a straight waveguide, and the other part is transmitted through a curved waveguide.

[0011] As a further aspect of the present invention, in the second step, the radius of the curved waveguide is adjusted so that the length difference between the curved waveguide and the straight waveguide is a fixed value.

[0012] As a further aspect of the present invention, the length difference between the curved waveguide and the straight waveguide is accurate to the micrometer level.

[0013] As a further aspect of the present invention, taking the geometric path difference between the two light paths in the curved waveguide and the straight waveguide as L, and the refractive index as n, the optical path difference between the two channels in the curved waveguide and the straight waveguide can be expressed as n*L; for different input light wavelengths λ, the phase difference is... The % symbol represents the remainder, which indicates that the energy of the transmitted light changes periodically with the phase difference, and is represented as a cosine curve in the energy-wavelength relationship graph on the spectral scan.

[0014] As a further aspect of the present invention, for an energy peak, its corresponding wavelength satisfies n*L=mλ, where m=1,2,3…, then for adjacent energy peaks, the wavelength correspondence is obtained as n*L=m0λ1=(m0+1)λ2, calculated as follows: Where λ1 and λ2 are the wavelengths corresponding to adjacent energy peaks;

[0015] That is, the effective refractive index of the test device is determined by the wavelength of the adjacent energy peaks.

[0016] As a further aspect of the present invention, the geometric path difference L between the two optical paths in the curved waveguide and the straight waveguide is calculated as follows: the length of the straight waveguide is a fixed value, the length of the curved waveguide is obtained by calculating the radius angle of the arc, and the difference between the lengths of the curved waveguide and the straight waveguide is the geometric path difference L between the two optical paths.

[0017] The beneficial effects of this invention are:

[0018] (1) By fabricating a test device and testing its corresponding wavelength scan, the refractive index of the wafer on which the device is located can be calculated. This makes it convenient to calculate the refractive index of other devices on the wafer. Compared with the traditional refractive index measurement method, this measurement method uses a spectrometer with an accuracy of 0.1 nm. Relying on the accuracy of the spectrometer, the effective refractive index after ion exchange can be accurately obtained, which has a high reference value for other devices in this process and facilitates the optimization and improvement of subsequent designs.

[0019] (2) The optical path difference control method and test device design concept based on the Mach-Zehnder interference principle of this invention are not limited to dual-path, shape, or length, and have good versatility. Attached Figure Description

[0020] The invention will now be further described with reference to the accompanying drawings.

[0021] Figure 1 This is a schematic diagram of the structure of the test device of the present invention;

[0022] Figure 2This is a schematic diagram of the wavelength scanning spectrum.

[0023] In the diagram: 1. Bent waveguide; 2. Straight waveguide; 3. Y-splitter. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] A precise method for measuring ion-exchange refractive index, comprising:

[0026] The first step is to transfer the pattern on the photomask onto the glass substrate using photolithography.

[0027] The second step involves exchanging the required test devices based on the photolithographic pattern using an ion exchange process.

[0028] The test device is designed based on the Mach-Zehnder principle. The main content of the Mach-Zehnder principle is that after a beam emitted from a single source is split into two beams, the relative phase shift changes after passing through different length paths. The interference of the two beams with different phases causes a change in the intensity of the output light. The amount of intensity change depends on the phase difference between the two beams. When the length difference is fixed, the phase difference changes with the refractive index.

[0029] like Figure 1 As shown, the test device includes a curved waveguide 1 and a straight waveguide 2 arranged in parallel. The length of the straight waveguide 2 is a fixed value, and the length of the curved waveguide 1 can be adjusted by the radius of the curved waveguide 1 so that the length difference between the curved waveguide 1 and the straight waveguide 2 is a fixed value.

[0030] The third step is to perform light scanning based on a spectrometer and a broadband light source. This involves connecting the input end of the test device to a broadband light source and the output end to a spectrometer via a coupled light method. This completes the wavelength scan of the device, obtains the output optical power at different light wavelengths, and then obtains the effective refractive index of the test device.

[0031] The specific method in the third step is as follows:

[0032] The input light is divided into two parts with equal energy by Y-branch 3. The two light fields can be expressed as E1 = E2 = 0.5 * sin x, where the total energy of the input light is 1.

[0033] A portion of the light is transmitted through a straight waveguide 2 of fixed length, and the other portion is transmitted through a bent waveguide 1;

[0034] By adjusting the radius of the curved waveguide 1, the distance between the curved waveguide 1 and the straight waveguide 2 is made to a fixed value.

[0035] It should be noted that the length difference between the curved waveguide 1 and the straight waveguide 2 needs to be accurate to the micrometer level;

[0036] Let L be the geometric path difference between the two light paths in the curved waveguide 1 and the straight waveguide 2, and let n be the refractive index. Then, the optical path difference between the two channels in the curved waveguide 1 and the straight waveguide 2 can be expressed as n*L. For different input light wavelengths λ, the phase difference is... The % symbol represents the remainder, indicating that the energy of the transmitted light changes periodically with the phase difference, which is represented as a cosine curve in the energy-wavelength relationship graph on its spectral scan.

[0037] The geometric path difference L between the two light paths in the curved waveguide 1 and the straight waveguide 2 is calculated as follows: the length 2 of the straight waveguide is a fixed value, and the length of the curved waveguide 1 can be obtained by calculating its arc radius angle. The difference between the lengths of the curved waveguide 1 and the straight waveguide 2 is the geometric path difference L between the two light paths.

[0038] For an energy peak, its corresponding wavelength satisfies n*L=mλ, where m=1,2,3… Then, for adjacent energy peaks, their wavelength correspondence can be obtained as n*L=m0λ1=(m0+1)λ2, from which we can calculate… The effective refractive index of the test device can be determined by the wavelength of adjacent energy peaks.

[0039] Where λ1 and λ2 are the wavelengths corresponding to adjacent energy peaks;

[0040] like Figure 2 As shown, in one embodiment of the present invention, L is a known design value, specifically, L = 38252.74 nm, and λ1 = 1273 nm, λ2 = 1301 nm, so n*L = 59149.0357. According to the above calculation method, the refractive index n = 1.546.

[0041] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for accurately measuring ion-exchange refractive index, characterized in that, include: The first step is to transfer the pattern on the photomask onto the glass substrate using photolithography. The second step involves exchanging the required test devices based on the photolithographic pattern using an ion exchange process. The test device includes a curved waveguide (1) and a straight waveguide (2) arranged in parallel, wherein the length of the straight waveguide (2) is a fixed value; The third step is to perform light scanning based on a spectrometer and a broadband light source. This involves connecting the input end of the device to a broadband light source and the output end to a spectrometer via optical coupling to complete the wavelength scan of the device. Let L be the geometric path difference between the two light paths in the curved waveguide (1) and the straight waveguide (2), and let n be the refractive index. Then the optical path difference between the two channels of the curved waveguide (1) and the straight waveguide (2) can be expressed as: For different input light wavelengths The phase difference is , where % is the remainder symbol, thus the energy of the transmitted light changes periodically with the phase difference, which is represented as a cosine curve in the energy-wavelength relationship graph on the spectral scan. For the energy peak, the corresponding wavelength satisfies Where m = 1, 2, 3…, then the wavelength correspondence between adjacent energy peaks can be obtained. Calculated Where λ1 and λ2 are the wavelengths corresponding to adjacent energy peaks; The units for L, λ1, and λ2 are all nm; That is, the effective refractive index of the test device is determined by the wavelength of the adjacent energy peaks.

2. The method for accurately measuring ion-exchange refractive index according to claim 1, characterized in that, In the third step, the input light at the input end of the test device is divided into two parts with equal energy by a Y-brancher (3). The total energy of the input light is 1. One part of the light is transmitted through a straight waveguide (2), and the other part is transmitted through a curved waveguide (1).

3. The method for accurately measuring ion-exchange refractive index according to claim 1, characterized in that, In the second step, the radius of the curved waveguide (1) is adjusted so that the length difference between the curved waveguide (1) and the straight waveguide (2) is a fixed value.

4. The method for accurately measuring ion-exchange refractive index according to claim 3, characterized in that, The length difference between the curved waveguide (1) and the straight waveguide (2) is accurate to the micrometer level.

5. The method for accurately measuring ion-exchange refractive index according to claim 1, characterized in that, The geometric path difference L between the two light paths in the curved waveguide (1) and the straight waveguide (2) is calculated as follows: the length of the straight waveguide (2) is a fixed value, and the length of the curved waveguide (1) is obtained by calculating the radius angle of the arc. The difference between the lengths of the curved waveguide (1) and the straight waveguide (2) is the geometric path difference L between the two light paths.

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