A method and apparatus for measuring the thickness of optical chips based on the Fabry-Perot interferometry principle

Abstract

This invention provides a method and apparatus for measuring the thickness of an optical chip based on the Fabry-Perot interferometry principle. The apparatus includes an auxiliary light source, an optically connected light source and fiber optic circulator, a beam splitter optically connected to both the auxiliary light source and the fiber optic circulator, a beam collimator optically connected to the mother end of the beam splitter, a chip under test (DUT) positioned at the output end of the beam collimator, a three-dimensional micro-motion platform holding the DUT, and a testing device connected to the other end of the fiber optic circulator. Utilizing the Fabry-Perot interferometry principle as the measurement principle, optical signals are transmitted via optical fiber. A 1*2 beam splitter is added to introduce red light, enabling visible light-assisted adjustment and accelerating the chip's position adjustment speed, thus achieving rapid measurement of the thickness of transparent chips. This invention allows for miniaturization, low cost, and high speed. Users can clearly identify the measurement point based on the beam illumination point, and visible light also provides visualization of the reflected light entering the collimator.

Description

Technical Field

[0001] This invention relates to the field of measurement and testing technology, and specifically to a method and apparatus for measuring the thickness of an optical chip based on the Fabry-Perot interference principle. Background Technology

[0002] Chips play a vital role in modern technology and social life. As a high-tech industry, they possess high technological content and added value, and are of great significance to national economic development. Because chips are used in a wide range of environments, almost in all high-tech fields, their forms are diverse. For example, there are traditional silicon-based chips, and sapphire chips processed using MEMS technology, commonly used in the rapidly developing field of optics.

[0003] Chip thickness is an important physical indicator of a chip. Currently, measurement methods include using spectral confocal, white light confocal, and laser triangulation principles. However, due to the limitations of these principles, the equipment used is generally large, expensive, and slow.

[0004] Therefore, a rapid method for measuring chip thickness is needed. Summary of the Invention

[0005] This invention addresses the issue of slow chip thickness measurement speed by providing an optical chip thickness measurement method and apparatus based on the Fabry-Perot interferometry principle. The method includes an auxiliary light source, an optically connected light source and fiber optic circulator, a beam splitter optically connected to both the auxiliary light source and the fiber optic circulator, a beam collimator optically connected to the mother end of the beam splitter, a chip under test (DUT) positioned at the output end of the beam collimator, a three-dimensional micro-motion platform holding the DUT, and a testing device connected to the other end of the fiber optic circulator. This invention utilizes the Fabry-Perot interferometry principle as the measurement principle, transmitting optical signals via optical fiber. By incorporating a 1*2 beam splitter to introduce red light, visible light-assisted adjustment is achieved, accelerating the chip position adjustment speed. The accurate measurement position can be determined in real-time using the auxiliary red light, enabling rapid measurement of the thickness of transparent chips. This invention is miniaturized, cost-effective, and fast. Users can clearly identify the measurement point based on the beam illumination point, and visible light also provides visualization of the reflected light entering the collimator.

[0006] This invention provides a method for measuring the thickness of an optical chip based on the Fabry-Perot interferometry principle, comprising the following steps:

[0007] S1. Construct an optical chip thickness measurement device based on the Fabry-Perot interference principle. Establish optical connections between the sub-end of the beam splitter and the auxiliary light source and one port of the fiber optic circulator, respectively. Establish an optical connection between the other port of the fiber optic circulator and the light source. Establish an optical connection between the mother end of the beam splitter and the beam collimator. Establish an optical connection between the third port of the fiber optic circulator and the testing device. The auxiliary light source is a visible light source, and the light source is a broadband laser. The testing device includes a demodulation device.

[0008] S2. Place the chip under test on a three-dimensional micro-motion platform, located at the lower end of the beam collimator. The chip under test is a transparent chip that can undergo optical reflection on both its upper and lower surfaces.

[0009] S3. Turn on the auxiliary light source. The auxiliary light is output to the chip under test through the beam splitter and beam collimator. Adjust the position of the chip under test by adjusting the three-dimensional micro-motion platform so that the auxiliary light reflected by the chip under test enters the beam collimator.

[0010] S4. Turn on the light source. The output light from the light source passes sequentially through the fiber optic circulator and beam splitter into the beam collimator. After collimation, it is directed towards the chip under test (DUT). The DUT reflects the light and then passes sequentially through the beam collimator, beam splitter, and fiber optic circulator to the testing device. The testing device uses two-beam interference demodulation to obtain the reflection spectrum of the EFPI sensor. After Fourier transform, the EFPI cavity length d is obtained. Combined with the refractive index n of the DUT, the thickness D of the DUT is obtained.

[0011]

[0012] A method for measuring the thickness of optical chips based on the Fabry-Perot interferometry principle has been developed.

[0013] In the optical chip thickness measurement method based on the Fabry-Perot interferometry principle described in this invention, as a preferred embodiment, in step S4, the EFPI sensor reflectance spectrum is as follows:

[0014] I(v) = C1 + C2cos(4πdv);

[0015] in: C1 and C2 are constants, and λ is the wavelength of the light source;

[0016] After filtering out the DC portion of the EFPI sensor's reflectance spectrum:

[0017] I(v)=∫P(f)exp(i2πfv)df;

[0018] Where P is the frequency spectrum distribution corresponding to the interference spectrum, and f is the frequency;

[0019] The EFPI sensor reflectance spectrum after filtering out DC flow is subjected to Fourier transform to obtain the distribution of spectral energy as a function of EFPI cavity length. The cavity length d is obtained by reading the peak coordinates from the distribution of spectral energy as a function of EFPI cavity length.

[0020] In the preferred embodiment of the optical chip thickness measurement method based on the Fabry-Perot interference principle described in this invention, in step S1, one sub-end of the beam splitter is optically connected to an auxiliary light source, the other sub-end is optically connected to the PORT2 end of the fiber optic circulator, the PORT1 end of the fiber optic circulator is optically connected to the light source, and the PORT3 end of the fiber optic circulator is connected to the testing device.

[0021] The optical chip thickness measurement method based on the Fabry-Perot interference principle described in this invention, as a preferred method, involves wiping the FC / APC fiber end face of the splitter with 2ml of ethanol solution using a lint-free paper. Then, the protrusion of the splitter's encapsulation connector is aligned with the recess of the fiber circulator, and the fiber of the FC / APC ferrule is slowly inserted while maintaining parallel alignment with the white ceramic alignment piece of the fiber circulator. After insertion, the nut is tightened to the maximum tightness.

[0022] In the preferred embodiment of the optical chip thickness measurement method based on the Fabry-Perot interference principle described in this invention, in step S1, the beam collimator is fixed at a height of 5-15 cm in a direction perpendicular to the three-dimensional micro-motion platform. The fiber optic sleeve is removed at 1.5 cm from the end of the fiber optic pigtail, and the coating layer is removed at 1.2 cm. The fiber optic with the coating layer removed is cleaned with 2 ml of ethanol solution using a lint-free paper. The fiber optic is then cut flat at 1.0 cm from the end using a fiber optic cleaver, and the fiber end face is perpendicular to the axial transmission direction of the fiber.

[0023] Remove the fiber optic sleeve 1.5cm from the end of the pigtail at the female end of the splitter and the coating layer 1.2cm from the end. Clean the fiber with the coating removed using a 2ml ethanol solution on a lint-free paper. Use a fiber optic cleaver to cut the fiber flat at the end 1.0cm and make the fiber end face perpendicular to the fiber axial transmission direction.

[0024] Start the fiber optic fusion splicer, place the processed beam collimator fiber and splitter cable into the V-groove respectively, and cover the fusion splicer with the windproof cover. Then, use the fiber optic fusion splicer to discharge and remove dust from the fiber end face. The end face cutting status can be viewed on the display screen of the fiber optic fusion splicer. If the onboard detection of the fusion splicer issues an alarm, the end face needs to be recut. If the tilt angle between the plane and the cross-section of the fiber is less than 1°, the fiber optic fusion splicer assumes that the end face condition is good.

[0025] The optical chip thickness measurement method based on the Fabry-Perot interference principle described in this invention, as a preferred method, uses an LC / APC-FC / APC jumper to connect the demodulator of the test device to a PLC splitter connected to an optical fiber circulator.

[0026] The optical chip thickness measurement method based on the Fabry-Perot interference principle described in this invention, as a preferred method, involves connecting the other sub-end of the beam splitter to an auxiliary light source. The connection method is as follows: after opening the protective cover of the auxiliary light source, use a lint-free paper dipped in 2ml of ethanol solution to wipe and clean the fiber end face of the FC / APC. Then, slowly insert the fiber of the FC / APC ferrule into the white ceramic alignment piece of the fiber coupler while keeping it parallel to the fiber.

[0027] Connect the demodulator to the computer's network interface using an 8-core network cable, and open the accompanying software to read the spectral signal.

[0028] In step S4, open the LabVIEW software and call the demodulation calculation software to obtain the thickness of the chip under test.

[0029] This invention provides an optical chip thickness measurement device based on the Fabry-Perot interference principle, comprising an auxiliary light source, an optically connected light source and an optical fiber circulator, a beam splitter optically connected to both the auxiliary light source and the optical fiber circulator, a beam collimator optically connected to the mother end of the beam splitter, a chip under test disposed at the output end of the beam collimator, a three-dimensional micro-motion platform for holding the chip under test, and a testing device connected to the other end of the optical fiber circulator.

[0030] The auxiliary light source outputs visible light. The light source is a broadband light source. The light transmission band of the beam collimator includes the bands of the auxiliary light source and the light source. The beam collimator is perpendicular to the three-dimensional micro-motion platform. The chip under test is located at the center of the three-dimensional micro-motion platform.

[0031] The fiber optic circulator transmits the output light from the light source to the beam splitter and detects the thickness of the chip under test. The detection signal reflected back from the chip under test is then transmitted through the fiber optic circulator to the demodulation device of the test apparatus.

[0032] The optical chip thickness measurement device based on the Fabry-Perot interferometry principle described in this invention, in a preferred embodiment, includes a demodulation device and a computer that are sequentially optically connected to one port of an optical fiber circulator.

[0033] The fiber optic circulator includes a fiber optic circulator body and PORT1, PORT2, and PORT3 ports respectively connected to the fiber optic circulator body; PORT1 port is optically connected to the light source, PORT2 port is optically connected to one sub-end of the splitter, and PORT3 port is optically connected to the demodulation device.

[0034] The beam splitter is a 1*2 beam splitter consisting of two sub-ends and one female end;

[0035] The auxiliary light source and the fiber optic circulator are each connected to one of the sub-ends of the beam splitter.

[0036] The three-dimensional micro-motion platform can be adjusted in the x-direction, y-direction, and z-direction.

[0037] The optical chip thickness measurement device based on the Fabry-Perot interference principle described in this invention, as a preferred embodiment, uses a red light-emitting fiber optic test pen with a wavelength of 650nm as the auxiliary light source and is compatible with an FC fiber optic interface.

[0038] The splitter is a PLC splitter with a female end in the form of a pigtail and two female ends in the form of FC / APC ferrules.

[0039] The beam collimator is a fiber optic collimator with a collimation angle of 0.1°;

[0040] The refractive index of the chip under test is a known constant, and the chip under test is a transparent quartz chip or a sapphire chip;

[0041] The demodulation device is a spectral demodulator, or an MOI demodulator can be used to replace the light source, fiber optic circulator, and demodulation device. The computer includes a chassis, computer monitor, and computer host.

[0042] This invention discloses a method and apparatus for measuring the thickness of a transparent chip using optical means and with the assistance of visible red light. The apparatus utilizes the Fabry-Perot interferometry principle as its measurement principle, transmits optical signals via optical fiber, and introduces red light through a 1*2 beam splitter to achieve visible light-assisted adjustment, thereby accelerating the chip's position adjustment speed and enabling rapid measurement of the transparent chip's thickness.

[0043] This invention utilizes optical methods to achieve a method for measuring the thickness of transparent chips under the assistance of visible red light. Its key features include the following steps:

[0044] Step 1. Selection of light source, auxiliary light source, fiber collimator, and demodulation device: The light source should be selected to match the band identified by the demodulation module; the auxiliary light source should be a visible light band laser; the optical transmission band of the fiber collimator should include the bands of both the light source and the auxiliary light source; the demodulation device should be selected with tunable Fabry-Perot filtering function.

[0045] Step 2. Set up the signal collection and primary processing device: Connect one of the sub-ends of the 1*2 beam splitter to the auxiliary light source, and the other sub-end to the PORT2 end of the fiber optic circulator. Connect the PORT1 end of the circulator to the light source, and the PORT3 end to the demodulation device. Connect the female end of the 1*2 beam splitter to the collimator.

[0046] Step 3. Set up the test setup, which consists of the signal acquisition and primary processing unit connected in Step 2, a computer, and a three-dimensional micro-motion platform. This setup collects signals, performs primary processing via demodulation, and then transmits the data to the computer for software calculation and final measurement output.

[0047] Step 4. The relative positional relationship is that the beam collimator is perpendicular to the three-dimensional micro-motion platform, and the chip under test is placed at the center of the three-dimensional micro-motion platform.

[0048] This invention introduces a PLC beam splitter, which allows the fiber collimator to be connected to both a broadband light source and an auxiliary light source simultaneously. This enables rapid detection of the thickness of a chip at a specified location with the assistance of visible light. The auxiliary light source is also turned on when the broadband light source is turned on.

[0049] This invention employs a customized three-dimensional micro-displacement platform, which can precisely move the chip under test to achieve detection at different positions of the optical chip.

[0050] The auxiliary light emitted by the device manufactured by the present invention, together with the test light beam, is directed perpendicularly to the chip under test. The upper and lower surfaces of the chip under test reflect the light beam to form an FP cavity. After being transmitted through the device, the signal enters the demodulation device for signal processing to obtain the cavity length, and then the thickness of the chip.

[0051] This invention introduces an optical fiber circulator, which allows the light from the broadband light source to be transmitted to a 1*2 beam splitter for detection of the optical chip. Simultaneously, the reflected detection signal, after passing through the optical fiber circulator, reaches the demodulation device for signal demodulation.

[0052] The present invention has the following advantages:

[0053] (1) Existing devices for measuring the thickness of optical chips are developed based on the principles of spectral confocal, white light confocal, and laser triangulation. Due to the limitations of these principles, the devices are large and costly. All three principles calculate the chip thickness by the positional difference between the upper and lower surfaces, requiring a refocusing process during measurement, resulting in slow measurement speed. The principle and device used in this invention can be miniaturized and are less expensive. The thickness is measured directly by measuring the FP cavity length constructed from the chip, eliminating the need for repeated focusing steps. The measurement speed is determined solely by the signal acquisition speed of the signal transmission and demodulation device; the light transmission speed is 3 × 10⁻⁶. 8 With a demodulation rate of m / s, the computer can demodulate up to 50 times / second. Therefore, after placing the chip under test in a suitable position, the thickness information can be obtained within 0.02 seconds, which is very fast.

[0054] (2) By introducing auxiliary light in the visible light band, the measurement position is clear at a glance. Users can determine the measurement point position based on the beam illumination point. At the same time, visible light also provides a visualization means for reflected light to enter the collimator. Attached Figure Description

[0055] Figure 1 This is a flowchart of an optical chip thickness measurement method based on the Fabry-Perot interferometry principle.

[0056] Figure 2 This is a schematic diagram of an optical chip thickness measurement device based on the Fabry-Perot interference principle.

[0057] Figure 3 A flowchart illustrating the fabrication of an optical chip thickness measurement method and device based on the Fabry-Perot interferometry principle;

[0058] Figure 4 This is a schematic diagram of an optical chip thickness measurement method and device based on the Fabry-Perot interference principle.

[0059] Figure 5 A typical reflection spectrum of EFPI, an optical chip thickness measurement method and device based on the Fabry-Perot interferometry principle;

[0060] Figure 6 This is a schematic diagram showing the distribution of spectral energy as a function of the EFPI cavity length in an optical chip thickness measurement method and device based on the Fabry-Perot interference principle.

[0061] Figure label:

[0062] 1. Auxiliary light source; 2. Light source; 3. Fiber optic circulator; 31. Fiber optic circulator body; 32. PORT1 port; 33. PORT2 port; 34. PORT3 port; 4. Beam splitter; 5. Beam collimator; 6. Chip under test; 7. Three-dimensional micro-motion platform; 8. Testing device; 81. Demodulation device; 82. Computer. Detailed Implementation

[0063] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0064] Example 1

[0065] like Figures 1-4 As shown, an optical chip thickness measurement method and device based on the Fabry-Perot interference principle are presented.

[0066] One method for measuring the thickness of an optical chip based on the Fabry-Perot interferometry principle includes:

[0067] (1) Step 1: Selection of auxiliary light source 1, light source 2, fiber collimator 5, and demodulation device 81: The light source 2 should be selected to match the band identified by the demodulation module 81; the auxiliary light source 1 should be a visible light band laser; the optical band of the fiber collimator 5 should include the bands of light source 2 and auxiliary light source 1; the demodulation device 81 should be selected with tunable Fabry-Perot filtering function.

[0068] Selection of Laser 1, Collimator 5, and Demodulation Device 81: Laser 1 is selected as a visible light laser, such as a commonly used 650nm red light fiber optic test pen (hereinafter referred to as the red light pen). This device is compatible with FC fiber optic interfaces, providing convenience for subsequent use. Collimator 5 is selected as a wide-band collimator, requiring that it allows both the auxiliary visible light band and the test light source band to pass through. A commercially available MOI demodulator is selected as the demodulation device, which includes three parts: light source 2, fiber optic circulator 3, and demodulation device 81. The female end of the 1*2 beam splitter 4 adopts a pigtail form, and the two female ends adopt an FC / APC ferrule package. The chip under test 6 is a quartz chip.

[0069] (2) Step 2: Set up a signal collection and primary processing device: Connect one of the sub-ends of the 1*2 beam splitter 4 to the auxiliary light source 1, and the other sub-end to the fiber optic circulator PORT2 end 33. Connect the circulator PORT1 end 32 to the light source 2, and the PORT3 end 34 to the demodulation device 81. Connect the 1*2 beam splitter 4 to the collimator 5.

[0070] Purchase a broadband collimator 5 with a collimation angle of 0.1° from the market and fix it at a height of 10 cm in a direction perpendicular to the three-dimensional micro-motion platform 7. Remove the fiber optic sleeve 1.5 cm from the end of the collimator 5 and the coating layer 1.2 cm from the end. Clean the fiber with 2 ml of ethanol solution using lint-free paper. Use a fiber optic cleaver to cut the fiber flat at the end 1.0 cm, ensuring the end face is perpendicular to the fiber's axial transmission direction. Perform the same operation on the female end of the PLC 1-to-2 splitter 4. Start the fiber optic fusion splicer, place the two prepared fibers in the V-groove respectively, and cover the fusion splicer with its windproof cover. Then, use the fiber optic fusion splicer to discharge and remove dust from the fiber end faces. The end face cutting status can be viewed on the fusion splicer's display screen. If the fusion splicer's onboard detection issues an alarm, the end face needs to be recut; otherwise, if the angle between the plane and the fiber cross-section is less than 1°, the fiber optic fusion splicer assumes the end face condition is good.

[0071] Next, connect one of the sub-ends of the 1*2 splitter 4 to the fiber coupler 3. Before connecting, use a lint-free paper soaked in 2ml of ethanol solution to wipe and clean the fiber end face of the FC / APC. Then, align the protrusion of its encapsulation connector with the recess of the fiber coupler 3, and slowly insert the fiber of the FC / APC ferrule with the white ceramic alignment piece of the fiber coupler 3 while keeping them parallel. After insertion, tighten the nut to the tightest position.

[0072] Connect the MOI demodulator 81 to the PLC splitter 4 (connected to the fiber optic coupler in the previous step) using an LC / APC-FC / APC jumper cable. Insert the LC / APC jumper cable into the signal channel of the MOI demodulator until you hear a click, indicating a successful connection. Clean the FC / APC end of the jumper cable with a lint-free paper towel soaked in 2ml of ethanol solution. Then, insert the jumper cable into the other end of the fiber optic coupler using the same procedure as in the previous step and tighten it.

[0073] Connect the other end of the 1*2 splitter 4 to the red light pen 1. The connection method is as follows: open the protective cover of the red light pen 1, then use a lint-free paper dipped in 2ml of ethanol solution to wipe and clean the fiber end face of the FC / APC. After that, keep the fiber of the FC / APC ferrule parallel to the white ceramic alignment piece of the fiber coupler 3 and slowly insert it. The appropriate depth is when you feel the damping of the spring.

[0074] (3) Step 3: Set up the test device, which consists of the signal collection and primary processing device connected in step 2, the computer 82, and the three-dimensional micro-motion platform 7. Fix the beam collimator in a direction perpendicular to the three-dimensional micro-motion platform 7.

[0075] Connect the MOI demodulator 81 to the computer's network interface 82 using an 8-core network cable, and open the MOI software to read the MOI signal. Open LabVIEW software, call the corresponding demodulation calculation software, and the measured signal and the thickness information of the chip under test 6 will be displayed.

[0076] (4) Step 4: Place the transparent chip 6 to be tested on the three-dimensional micro-motion platform 7, and adjust the three-dimensional micro-motion platform 7 so that the light beam shines on the point to be tested, and at the same time confirm that the light beam reflected by the transparent chip 6 enters the collimator 5.

[0077] After the operator puts on the laser goggles, they turn on the red light pen 1 to the constant light state, place the sapphire chip 6 to be tested in the middle part of the three-dimensional micro-motion platform 7, observe the auxiliary light in the visible band, and select the position to be measured by adjusting the three-dimensional micro-motion platform 7 to ensure that the auxiliary light shines on the position to be measured and enters the collimator 5 after being reflected by the transparent chip 6.

[0078] (5) Step 5: After the primary processing of the demodulation device and the demodulation processing of the computer 82, the thickness of the chip under test 6 can be displayed in real time on the computer.

[0079] By inputting the refractive index of the chip 6 to be tested into the computer display interface, the thickness information of the chip 6 can be read, and the measurement can be completed.

[0080] The demodulation device uses two-beam interferometry demodulation. The typical reflection spectrum of the EFPI sensor obtained by the demodulation terminal is shown below, and its schematic diagram is as follows. Figure 5 As shown:

[0081] I(v)=C1+C2cos(4πdv) (1)

[0082] in: C1 and C2 are constants, λ is the wavelength, and d is the cavity length of the FP cavity. After filtering out the DC flow, equation (1) can be written as:

[0083] I(v)=∫P(f)exp(i2πfv)df (2)

[0084] Where P represents the frequency spectrum distribution corresponding to the interference spectrum, and f is the frequency. Performing a Fourier transform on this frequency yields the distribution of spectral energy as a function of the EFPI cavity length, as illustrated in the diagram below. Figure 6 As shown, the horizontal axis of the peak value is read, and its cavity length is 785 micrometers. Combined with the thickness conversion formula:

[0085]

[0086] Where d is the cavity length of the FP cavity, and n is the refractive index of the material of the chip under test. Since the chip in this example is made of quartz, its refractive index is 1.575, and its thickness is:

[0087]

[0088] After measurement, the computer interface showed a thickness of 0.4984 mm.

[0089] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for measuring the thickness of an optical chip based on the Fabry-Perot interferometry principle, characterized in that: Includes the following steps: S1. Construct an optical chip thickness measurement device based on the Fabry-Perot interference principle. Establish optical connections between the sub-end of the beam splitter (4) and one port of the auxiliary light source (1) and the fiber optic circulator (3), respectively. Establish an optical connection between the other port of the fiber optic circulator (3) and the light source (2). Establish an optical connection between the mother end of the beam splitter (4) and the beam collimator (5). Establish an optical connection between the third port of the fiber optic circulator (3) and the testing device (8). The auxiliary light source (1) is a visible light source, the light source (2) is a broadband laser, and the testing device (8) includes a demodulation device. S2. Place the chip under test (6) on the three-dimensional micro-motion platform (7) and below the beam collimator (5). The chip under test (6) is a transparent chip that can undergo optical reflection on both the upper and lower surfaces. S3. Turn on the auxiliary light source (1). The auxiliary light is output to the chip under test (6) via the beam splitter (4) and the beam collimator (5). Adjust the position of the chip under test (6) by adjusting the three-dimensional micro-motion platform (7) so that the auxiliary light reflected by the chip under test (6) enters the beam collimator (5). S4. Turn on the light source (2). The output light of the light source (2) passes through the fiber optic circulator (3) and the beam splitter (4) in sequence, enters the beam collimator (5), and is collimated before being directed toward the chip under test (6). The chip under test (6) reflects the light and then passes through the beam collimator (5), the beam splitter (4), and the fiber optic circulator (3) in sequence before being output to the test device (8). The test device (8) uses two-beam interference demodulation to obtain the reflection spectrum of the EFPI sensor, and then performs Fourier transform to obtain the EFPI cavity length d. Combined with the refractive index n of the chip under test (6), the thickness D of the chip under test (6) is obtained. A method for measuring the thickness of optical chips based on the Fabry-Perot interferometry principle has been developed.

2. The optical chip thickness measurement method based on the Fabry-Perot interferometry principle according to claim 1, characterized in that: In step S4, the reflectance spectrum of the EFPI sensor is: I(v) = C1 + C2cos(4πdv); in:

1. C2 is a constant, and λ is the wavelength of the light source (2); After filtering out the DC portion of the reflectance spectrum from the EFPI sensor: I(v)=∫P(f)exp(i2πfv)df; Where P is the frequency spectrum distribution corresponding to the interference spectrum, and f is the frequency; The reflection spectrum of the EFPI sensor after filtering out the direct current is subjected to Fourier transform to obtain the distribution of spectral energy as a function of the EFPI cavity length. The cavity length d is obtained by reading the peak coordinates from the distribution of spectral energy as a function of the EFPI cavity length.

3. The optical chip thickness measurement method based on the Fabry-Perot interferometry principle according to claim 1, characterized in that: In step S1, one sub-end of the beam splitter (4) is optically connected to the auxiliary light source (1), and the other sub-end is optically connected to the PORT2 end of the fiber optic circulator (3). The PORT1 end of the fiber optic circulator (3) is optically connected to the light source (2), and the PORT3 end of the fiber optic circulator (3) is connected to the test device (8).

4. The optical chip thickness measurement method based on the Fabry-Perot interferometry principle according to claim 3, characterized in that: Use a lint-free paper soaked in 2ml of ethanol solution to wipe and clean the FC / APC fiber end face of the splitter (4). Then align the protrusion of the splitter (4) encapsulation connector with the recess of the fiber circulator (3), and slowly insert the fiber of the FC / APC ferrule with the white ceramic alignment piece of the fiber circulator (3) while keeping them parallel. After insertion, tighten the nut to the tightest position.

5. The optical chip thickness measurement method based on the Fabry-Perot interferometry principle according to claim 1, characterized in that: In step S1, the beam collimator (5) is fixed at a height of 5-15cm in a direction perpendicular to the three-dimensional micro-motion platform (7). The fiber sleeve is stripped at 1.5cm from the end of the pigtail of the beam collimator (5), and the coating is stripped at 1.2cm. The fiber with the coating stripped is cleaned with 2ml of ethanol solution using a lint-free paper. The fiber is cut flat at 1.0cm from the end using a fiber optic cutter, and the fiber end face is perpendicular to the axial transmission direction of the fiber. Remove the fiber sleeve at 1.5cm from the end of the pigtail of the splitter (4) and the coating at 1.2cm. Clean the fiber with the coating removed using a 2ml ethanol solution soaked in lint-free paper. Cut the fiber flat at 1.0cm from the end with a fiber optic cutter and make the fiber end face perpendicular to the fiber axial transmission direction. Start the fiber optic fusion splicer, place the processed beam collimator (5) fiber and the splitter (4) pipeline into the V-groove respectively, and cover the fusion splicer with the windproof cover. Then, use the fiber optic fusion splicer to discharge and remove the dust from the fiber end face. The end face cutting status can be obtained on the display screen of the fiber optic fusion splicer. If the onboard detection of the fusion splicer issues an alarm, the end face needs to be recut. If the tilt angle between the plane and the cross-section of the fiber is less than 1°, the fiber optic fusion splicer assumes that the end face is in good condition.

6. The optical chip thickness measurement method based on the Fabry-Perot interferometry principle according to claim 5, characterized in that: Use an LC / APC-FC / APC jumper to connect the demodulator of the test device (8) to the PLC splitter connected to the fiber optic circulator (3).

7. The optical chip thickness measurement method based on the Fabry-Perot interferometry principle according to claim 6, characterized in that: Connect the other end of the splitter (4) to the auxiliary light source (1). The connection method is as follows: after opening the protective cover of the auxiliary light source (1), use a dust-free paper dipped in 2ml of ethanol solution to wipe and clean the fiber end face of the FC / APC. Then, slowly insert the fiber of the FC / APC ferrule into the white ceramic alignment piece of the fiber coupler while keeping them parallel. Connect the demodulator to the computer's network interface using an 8-core transmission cable, and open the accompanying software to read the spectral signal. In step S4, open the LABVIEW software and call the demodulation calculation software to obtain the thickness of the chip under test (6).

8. An optical chip thickness measuring device based on the Fabry-Perot interferometry principle according to any one of claims 1 to 6, characterized in that: Includes an auxiliary light source (1), an optically connected light source (2), an optical fiber circulator (3), a beam splitter (4) optically connected to both the auxiliary light source (1) and the optical fiber circulator (3), a beam collimator (5) optically connected to the mother end of the beam splitter (4), a chip under test (6) disposed at the output end of the beam collimator (5), a three-dimensional micro-motion platform (7) holding the chip under test (6), and a test device (8) connected to the other end of the optical fiber circulator (3); The auxiliary light source (1) outputs visible light, the light source (2) is a broadband light source, the light transmission band of the beam collimator (5) includes the bands of the auxiliary light source (1) and the light source (2), the beam collimator (5) is perpendicular to the three-dimensional micro-motion platform (7), and the chip under test (6) is located at the center of the three-dimensional micro-motion platform (7). The fiber optic circulator (3) transmits the output light from the light source (2) to the beam splitter (4) and detects the thickness of the chip under test (6). The detection signal reflected back from the chip under test (6) reaches the demodulation device of the test device (8) after passing through the fiber optic circulator (3).

9. The optical chip thickness measurement device based on the Fabry-Perot interferometry principle according to claim 8, characterized in that: The testing device (8) includes a demodulation device (81) and a computer (82) that are sequentially optically connected to one port of the fiber optic circulator (3); The fiber optic circulator (3) includes a fiber optic circulator body (31) and PORT1 port (32), PORT2 port (33), and PORT3 port (34) respectively connected to the fiber optic circulator body (31); PORT1 port (32) is optically connected to the light source (2), PORT2 port (33) is connected to one end of the beam splitter (4), and PORT3 port (34) is optically connected to the demodulation device (81); The beam splitter (4) is a 1*2 beam splitter including two sub-ends and one female end; The auxiliary light source (1) and the fiber optic circulator (3) are respectively optically connected to one sub-end of the beam splitter (4); The three-dimensional micro-motion platform (7) can be adjusted in the x direction, y direction, and z direction.

10. The optical chip thickness measurement device based on the Fabry-Perot interferometry principle according to claim 9, characterized in that: The auxiliary light source (1) is a red light-emitting fiber optic test pen with a wavelength of 650nm and is compatible with an FC fiber optic interface. The splitter (4) is a PLC splitter with a female end in the form of a pigtail and two female ends in the form of FC / APC ferrules. The beam collimator (5) is an optical fiber collimator with a collimation angle of 0.1°; The refractive index of the chip under test (6) is a known constant, and the chip under test (6) is a transparent quartz chip or a sapphire chip; The demodulation device (81) is a spectral demodulator, or an MOI demodulator can be used to replace the light source (2), the fiber optic circulator (3) and the demodulation device (81); The computer (82) includes a chassis, a computer monitor, and a computer host.

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