A device and method for precise thickness measurement based on quantum interferometer

Abstract

The present invention relates to the field of precision measurement technology, and discloses a device and method for precise thickness measurement based on a quantum interferometer, including an entangled photon source, a polarization beam splitter, a reflector group, and a single-mode optical fiber group. The present invention obtains the sample thickness according to the Hong‑Ou‑Mande l (HOM) interference curve. Specifically, by placing half of the sample within the coverage range of the light beam, two HOM depressions will be generated at the same time, and a bulge / depression will appear between the two HOM depressions. According to the spacing between the HOM depressions at both ends and the height / depth analysis of the middle bulge / depression, high-precision (within 4.24nm) thickness information is calculated. The measurement method of the present invention has the advantages of a large range and high precision. The large range is provided by two HOM depressions. Theoretically, the range can be any value, and the high precision is provided by the middle bulge / depression. The present device also has good stability. In addition, because the light source used in the present invention is ultra-weak light, it can be used to measure biological living samples and biomolecular films without damage.

Description

Technical Field

[0001] The present invention relates to the field of precision measurement technology, and in particular to a device and method for precision thickness measurement based on a quantum interferometer. Background Art

[0002] Quantum precision measurement methods have many advantages over classical thickness measurement methods. Quantum precision measurement uses quantum properties, especially the consistency of basic quantum systems, to measure some key physical quantities with high precision and high sensitivity. This method can break through the limits of classical technology and achieve unprecedented measurement accuracy. The following lists the technical background and principles of HOM interference and NOON state interference.

[0003] HOM interference distance measurement: HOM interference refers to the fact that when two identical photons are input from the two input ports of a 2×2 beam splitter, they will be output simultaneously from one of the two output ports, rather than one from each of the two output ports. This interference effect has been playing an important role in quantum optics since it was discovered by three scientists, Hong, Ou and Mandel, in 1987.

[0004] HOM interference is a manifestation of the photon bunching effect, which is a non-classical effect of photons as bosons. HOM interference is a phase-insensitive interference, which has a natural advantage over Mach-Zehnder (MZ) interference. Therefore, it is applied to precise measurement in the time domain and can achieve attosecond-level time measurement.

[0005] HOM interference is usually achieved using correlated photon pairs generated from the spontaneous parametric down-conversion (SPDC) process. In the SPDC process, a pump photon is converted into a signal photon and an idler photon with a certain probability. The signal photon and the idler photon are correlated in terms of degrees of freedom such as time, frequency, space, and orbital angular momentum. Taking the frequency degree of freedom as an example, this correlation can be expressed as follows:

[0006]

[0007] Where f(ω s ,ω i )=φ(ω s ,ω i )α(ω s +ω i ) is the joint spectral amplitude (JSA) function, φ(ω s ,ω i ) and α(ω s +ω i ) are the pump envelope function and phase matching function respectively. ω is the angular frequency, is the photon generation operator, and the subscripts s and i denote the signal light and the idler light, respectively.

[0008] The formula of the HOM interference curve can be expressed as:

[0009]

[0010] The interference visibility of the HOM depression can be expressed by the following formula:

[0011]

[0012] In the above formula (3), P(0) is the coincidence counting probability when the delay time τ=0, and P(∞) is the coincidence counting probability when the delay time is much greater than 0.

[0013] The thickness measurement technology similar to the market is mainly based on film thickness gauges: common film thickness gauge brands on the market include Germany's Fischer, the United States' Veeco, Japan's KLA-Tencor, etc. Globally, companies that have deployed in the film thickness gauge market mainly include international companies such as Germany's Nix, Germany's Electronic Press Kit, Germany's Fischer, the United States' Difsco, the United Kingdom's Yigao, and the United Kingdom's Oxford, as well as Chinese companies such as Cangzhou Oupu Testing Instruments, Beijing Times Huade Technology, Shenzhen Lingchuang Jichen Technology, Shanghai Huayang Testing Instruments, Jiangsu Yiliu Instruments, China Electronics Technology Group, Guangzhou Lantai Instruments, Guangzhou Xima Instruments, and Guangzhou Jingyi Optoelectronics Technology.

[0014] At present, thin film thickness measurement has a wide range of applications in various industries, including: silicon dioxide film and calcium fluoride film in the precision optics industry; quantum dot chips, photoresists, GaN coatings in the semiconductor industry; perovskites, ITO in the new energy / photovoltaic industry; coating films, microchannels in the display panel industry; surface coating layers in the tool industry; PI films in the polymer material industry, etc. The measurement accuracy of a film thickness meter is one of its most critical technical indicators. The following are two film thickness meter products based on classical optical interference and their technical indicators:

[0015] 1. Hamamatsu Optical NanoGauge C13027-12

[0016] Measuring range: 10nm to 100μm; Measuring accuracy: ±0.4%

[0017] Features: Support PLC connection, high-speed measurement (up to 200Hz, suitable for high-speed production lines.)

[0018] 2. Wuxi Jingji Vision Company: Jingji Vision Optical Interference Thickness Gauge

[0019] Measuring range: 1nm to 3000μm

[0020] Theoretical accuracy: <0.01nm or 0.01%; stable accuracy: <0.02nm or 0.03%

[0021] Features: Powerful software material library, powerful control software.

[0022] There are at least the following problems that have not been solved in the prior art: 1. Realization of distance measurement and control through HOM interferometer. However, in many scenarios, high-precision thickness measurement of a certain material is required, and this is no longer applicable. The existing HOM distance measurement accuracy is limited by the accuracy of the delay device and cannot be further improved; 2. The film thickness meter based on the principle of optical interference has high accuracy. Because its manufacturing process requires precise processes and high-quality materials, and the complex software system required for data processing, its cost is also high. For example, Taiyi Rui Technology's SR-C series reflective film thickness meter has an accuracy of 15nm-70μm and a price of 120,000 yuan. The thin film measurement system TF-168 of Shanghai Afei Electronic Technology Co., Ltd. has a measurement accuracy of 20nm-50μm and its price is 180,000 yuan. At the same time, the existing film thickness meter based on the principle of optical interference is difficult to achieve a large range when improving accuracy. For example, the film thickness meter range of the above-mentioned Wuxi Jingjing Vision Company can only reach 3mm. Summary of the invention

[0023] The purpose of the present invention is to achieve high-precision thickness measurement information.

[0024] The present invention obtains the sample thickness based on the Hong-Ou-Mandel (HOM) interference curve. Specifically, by placing half of the sample within the coverage range of the light beam, two HOM depressions will be generated at the same time, and a bulge / depression will appear between the two HOM depressions. According to the spacing between the HOM depressions at both ends and the height / depth analysis of the middle bulge / depression, high-precision (within 4.24nm) thickness information is calculated. The measurement method of the present invention has the advantages of a large range and high precision. The large range is provided by the two HOM depressions. Theoretically, the range can be any value, and the high precision is provided by the middle bulge / depression. The device also has good stability because the HOM interference fringes are insensitive to photon phase changes. In addition, because the light source used in the present invention is ultra-weak light, it can perform non-destructive measurements on biological living samples and biomolecular films.

[0025] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a device and method for precise thickness measurement based on quantum interferometer, comprising an entangled photon source, a polarization beam splitter, a reflector group, and a single-mode optical fiber group, wherein the reflector group comprises a first reflector, a second reflector, a third reflector, a fourth reflector, a fifth reflector, and a sixth reflector, wherein the single-mode optical fiber group comprises a first single-mode optical fiber and a second single-mode optical fiber, wherein the polarization beam splitter comprises a first polarization beam splitter and a second polarization beam splitter, each having four ports, wherein the vertical polarization component of the light input to the first polarization beam splitter is output through the fourth port, and the horizontal polarization component is output through the second port, and the two output ports are respectively connected to the first reflector and the second reflector. The second reflector is located on a movable stepper motor. The reflected light is respectively output from the third port of the first polarization beam splitter through the first 810nm quarter wave plate and the second 810nm quarter wave plate. An 810nm half wave plate and a second polarization splitter are placed in sequence after the third port of the first polarization splitter. The horizontal polarization component of the light incident on the second polarization beam splitter is output through the second port, and the vertical polarization component is output through the fourth port. The two output ends are connected to the third reflector and the fifth reflector respectively. The third reflector is connected to the fourth reflector and then connected to the first single-mode optical fiber. The fifth reflector is connected to the sixth reflector and then connected to the second single-mode optical fiber. The first single-mode optical fiber is electrically connected to the first single-photon detector, and the second single-mode optical fiber is electrically connected to the second single-photon detector.

[0026] Preferably, a sample to be tested is arranged after the first 810 nm quarter wave plate in the sample path.

[0027] Preferably, the stepper motor is used to compensate for the optical path difference introduced by the sample being measured.

[0028] Preferably, it also includes a coincidence counter, which is connected to the first single-photon detector and the second single-photon detector, and is used for measuring the coincidence count.

[0029] Preferably, it also includes a computer, wherein the computer is electrically connected to the coincidence counter, and the computer is electrically connected to the stepper motor, and the computer is used to control the movement of the stepper motor, data processing and image display.

[0030] Preferably, the horizontally polarized light output from the second port of the second polarization beam splitter is coupled into and transmitted through the second single-mode optical fiber, and the vertically polarized light output from the fourth port is coupled into and transmitted through the first single-mode optical fiber.

[0031] Preferably, the entangled photon source is used to provide a stable output of correlated photon pairs, that is, signal photons and idler photons with a quantum correlation relationship. The output end of the entangled photon source is connected to a first polarization beam splitter, which is used to split the light emitted by the entangled photon source into two transmission paths.

[0032] A method for using a thickness precision measurement device based on a quantum interferometer comprises the following steps:

[0033] S1. Build an entangled photon source and adjust the temperature to make the spectrum of signal photons and idler photons in the down-converted light degenerate;

[0034] S2. When no signal or idler photon filter is added to the entangled photon source, the coupling of spatial light to single-mode optical fiber is completed by relying on the residual pump light emitted from the entangled photon source;

[0035] S3. After S2 is completed, signal photons and idler photon filters are added to the entangled photon source to filter the residual pump light, so that only signal photons and idler photons with a central wavelength of 810 nm exist in the subsequent optical path of the entangled photon source;

[0036] S4, add an 810nm half-wave plate, take the optical path where the second reflector is located as the standard, adjust the third reflector, the fourth reflector, the fifth reflector, and the sixth reflector so that the single count and coincidence count observed on the computer end are maximized, and the single photon counts of the two paths are equally divided; adjust the first reflector so that the single count observed on the computer end is maximized;

[0037] S5, when the computer controls the stepper motor to move, the HOM interference curve is observed;

[0038] S6. Place the sample to be tested between the first 810nm quarter-wave plate and the first polarization beam splitter, and make sure that only about half of the light passes through the sample (Note: When the sample is placed in the light path, if it has only one thickness, then it is necessary to allow only half of the light to pass through the sample while the other half passes through free space. If it is a sample with multiple thicknesses, it is necessary to make the light spot hit the different thicknesses of the sample at the same time. For example: a sample with two thicknesses requires half of the light spot to hit one thickness of the sample and the other half of the light spot to hit the other thickness).

[0039] S7. Re-control the movement of the stepper motor under computer control and observe the HOM interference curve, which consists of two depressions at both ends and a bulge in the middle.

[0040] S8. Repeat S7 several times to obtain repeated measurement data, and process the data to obtain sample thickness information.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention obtains the sample thickness based on the Hong-Ou-Mandel (HOM) interference curve. Specifically, by placing half of the sample within the coverage range of the light beam, two HOM depressions will be generated at the same time, and a bulge / depression will appear between the two HOM depressions. According to the spacing between the HOM depressions at both ends and the height / depth analysis of the middle bulge / depression, high-precision (within 4.24nm) thickness information is calculated. The measurement method of the present invention has the advantages of a large range and high precision. The large range is provided by the two HOM depressions. Theoretically, the range can be any value, and the high precision is provided by the middle bulge / depression. The device also has good stability because the HOM interference fringes are insensitive to photon phase changes. In addition, because the light source used in the present invention is ultra-weak light, it can perform non-destructive measurements on biological living samples and biomolecular films. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of the structure of a thickness precision measurement device based on a quantum interferometer proposed by the present invention;

[0044] Figure 2 It is the main view of the sample to be tested in the optical path;

[0045] Figure 3 It is the HOM concave and convex data map;

[0046] Figure 4 This is a summary graph of the data from ten experiments;

[0047] Figure 5 Interference pattern diagrams for three thicknesses.

[0048] In the figure: 1. entangled photon source; 2. first polarization beam splitter; 3. first reflector; 4. first 810nm quarter-wave plate; 5. measured sample; 6. second 810nm quarter-wave plate; 7. second reflector; 8. 810nm half-wave plate; 9. second polarization beam splitter; 10. third reflector; 11. fourth reflector; 12. first single-mode optical fiber; 13. first single-photon detector; 14. fifth reflector; 15. sixth reflector; 16. second single-mode optical fiber; 17. second single-photon detector; 18. coincidence counter; 19. computer; 20. stepper motor. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] like Figure 1-Figure 5 As shown, the present invention provides a device and method for precise thickness measurement based on quantum interferometer, including an entangled photon source 1, a polarization beam splitter, a reflector group, and a single-mode optical fiber group. The reflector group includes a first reflector 3, a second reflector 7, a third reflector 10, a fourth reflector 11, a fifth reflector 14, and a sixth reflector 15. The single-mode optical fiber group includes a first single-mode optical fiber 12 and a second single-mode optical fiber 16. The polarization beam splitter includes a first polarization beam splitter 2 and a second polarization beam splitter 9, each of which has four ports, wherein the vertical polarization component of the light input by the first polarization beam splitter 2 is output through the fourth port, and the horizontal polarization component is output through the second port, and the two output ports are respectively connected to the first reflector 3 and the second reflector 7. The second reflector 7 is located on a movable stepping motor 20. The reflected light passes through the first 810nm quarter wave plate 4 and the second 810nm quarter wave plate 6 respectively, and is output from the third port of the first polarization beam splitter 2. An 810nm half-wave plate 8 and a second polarization splitter 9 are sequentially placed after the third port of the first polarization splitter. The horizontal polarization component of the light incident on the second polarization beam splitter 9 is output through the second port, and the vertical polarization component is output through the fourth port. The two output ends are respectively connected to the third reflector 10 and the fifth reflector 14. The third reflector 10 is connected to the fourth reflector 11 and then connected to the first single-mode optical fiber 12. The fifth reflector 14 is connected to the sixth reflector 15 and then connected to the second single-mode optical fiber 16. The first single-mode optical fiber 12 is electrically connected to the first single-photon detector 13, and the second single-mode optical fiber 16 is electrically connected to the second single-photon detector 17.

[0051] Since the sample to be measured is not limited to point-by-point scanning measurement of HOM, but a spatial area scanning method determined by the sample thickness characteristic information, this method makes the interference image appear with multiple HOM depressions and convex / concave information determined by the sample thickness characteristics, which can realize the measurement of a single thickness or even multiple thicknesses, and the accuracy is further improved due to the convex / concave information characteristics introduced by this method.

[0052] The following demonstrates the thickness measurement results of single / double thickness samples:

[0053] By inserting a sample in the sample path, the sample contains two regions of different thicknesses, and half of the light spot is hit on the two regions of different thicknesses, we can obtain a HOM interference fringe image including two HOM depressions and one convex information. We calculate the thickness information of the sample (at the micrometer level) based on the distance information between the two HOM depressions. At the same time, the convex information in the HOM interference fringe image can provide us with more accurate thickness information (at the nanometer level), thereby calculating more precise thickness information of the sample.

[0054] The data were obtained through ten experiments:

[0055] HOM concave and convex data graphs can be obtained from ten experiments, such as Figure 3 .

[0056] The relevant optical path information (related to the sample thickness) can be read out simply by fitting the experimental data, and the thickness of the sample can be inferred by combining the refractive index information of the sample material.

[0057] The data from the ten experiments are summarized as follows: Figure 4 (Dip refers to the depression of HOM, and Bump refers to the bulge in the middle):

[0058] We obtain two pieces of information about thickness from the data: one is the optical path difference between the two HOM depressions ( Figure 4 ), from which a rough thickness value information is calculated ( Figure 4 The fifth column in the figure shows that the average value is 2138.03 μm, and the standard deviation of the thickness d is 7.83 μm according to the HOM depression. The other is the height information of the middle bulge caused by the phase difference between the two parts of light passing through the sample to be tested ( Figure 4 ), from which a more accurate thickness information is calculated ( Figure 4 The average value is 106.14nm and the standard deviation is 4.24nm. Therefore, the thickness of the sample to be measured is about 2138.03μm+0.10614μm=2138.13614μm, ranging from 2138.1319μm to 2138.14038μm. The measurement accuracy can reach within 4.24nm.

[0059] Using the Monte Carlo method, we simulated the results of this experiment 100 times and calculated its theoretical accuracy. The following are the data results of 100 simulation experiments (the three lists are the center position of the first HOM depression, the center position of the second HOM depression, and the height value of the middle bulge):

[0060]

[0061] Through the calculation of the data of one hundred theoretical experiments, the mean value of the sample thickness information obtained through the HOM depression is: 2140.63μm, and the standard deviation is 3.22521μm. The precise thickness information of the sample calculated through the information of the middle bulge is: 0.102688μm, and the standard deviation is 0.000795751μm. The theoretical accuracy is 0.796nm.

[0062] This method is not limited to this, and is extended to multiple thicknesses to give interference patterns at three thicknesses (air, where the thickness is 0, two slides, and three slides):

[0063] exist Figure 5 In the figure, there are three HOM concave information and one convex information between every two HOM concave information, and when a part of the light is distributed in free space, two high-precision thickness information are calculated using the same method. Figure 5 In the marking, the first, second, and third depressions are marked as ①, ②, and ③ respectively, and the first and second protrusions are marked as ④ and ⑤ respectively. According to the positions of the first and second HOM depressions, the rough thickness difference between the air and the two glass slides is calculated, and according to the height of the first protrusion, the more detailed thickness difference information between the air and the two glass slides is obtained. Similarly, the rough thickness difference between two glass slides and three glass slides can be obtained from the second and third HOM depressions, and the more detailed thickness difference information between two glass slides and three glass slides can be obtained according to the height of the second protrusion. Figure 2 This is the main view of the sample to be tested in the optical path, which is used to illustrate the spatial distribution of the sample and the light beam. As shown in the figure, for a sample with two thickness information, the light beam should be able to pass through two different thickness areas in space at the same time (different colors represent different thickness areas). The proportion of light intensity passing through different thicknesses determines the visibility of the depression in the experiment. The ratio is 1:1, and appropriate deviation will not have a decisive impact on the final result.

[0064] Among them, the sample path also includes a sample 5 to be tested arranged behind the first 810nm quarter wave plate 4;

[0065] Wherein, the stepper motor 20 is used to realize the compensation of the optical path difference introduced by the sample under test;

[0066] The coincidence counter 18 is also included. The coincidence counter 18 is connected to the first single-photon detector 13 and the second single-photon detector 17. The coincidence counter 18 is used for measuring the coincidence count.

[0067] The computer 19 is also included. The computer 19 is electrically connected to the coincidence counter 18. The computer 19 is electrically connected to the stepping motor 20. The computer 19 is used to control the movement, data processing and image display of the stepping motor 20.

[0068] The horizontally polarized light output from the second port of the second polarization beam splitter 9 is coupled into and transmitted through the second single-mode optical fiber 16 , and the vertically polarized light output from the fourth port is coupled into and transmitted through the first single-mode optical fiber 12 .

[0069] Among them, the entangled photon source 1 is used to provide a stable output of correlated photon pairs, that is, signal photons and idler photons with a quantum correlation relationship. The output end of the entangled photon source 1 is connected to the first polarization beam splitter 2, and the first polarization beam splitter 2 is used to split the light emitted by the entangled photon source 1 into two transmission paths.

[0070] Among them, a method for using a precision measurement device based on a quantum interferometer comprises the following steps:

[0071] Step 1: The polarizations of the signal photons and idler photons emitted by the entangled photon source 1 are orthogonal. The signal photons and idler photons are separated after passing through the first polarization beam splitter 2, respectively passing through the sample path containing the sample and reflecting back to the fourth port of the first polarization beam splitter 2 and the second reflector 7 placed on the stepper motor 20 and reflecting back to the second port of the first polarization beam splitter 2. Since the first 810nm quarter wave plate 4 and the second 810nm quarter wave plate 6 change the polarization state of the light, the signal photons and idler photons will then be output through the third port of the first polarization beam splitter 2, and the polarization states of the signal photons and idler photons will be changed at the 810nm half-wave plate 8, so that they are mixed and each half of the number passes through the second polarization beam splitter 9 and is output from its fourth port and second port. Then, the third reflector 10 and the fourth reflector 11 are used to couple the photons into the first single-mode optical fiber 12 for transmission and then input into the first single-photon detector 13 for collection and detection. The photons are coupled into the second single-mode optical fiber 16 by using the fifth reflector 14 and the sixth reflector 15 and then transmitted to the second single-photon detector 17 for collection and detection.

[0072] Step 2: When the signal photons and idler photons of the entangled photon source 1 meet the requirements of merging at a specific temperature, the movement of the stepper motor 20 controlled by the computer 19 can compensate the optical path difference of the idler photons introduced by the sample insertion, so that the two photons interfere at the second polarization beam splitter 9, making the photons completely indistinguishable. At this time, the recorded coincidence count will show a significant decrease at a specific position due to the completely indistinguishable state of the photons. The computer 19 calculates the thickness of the sample information based on the position information of the stepper motor 20 recorded therein and the corresponding coincidence count value.

[0073] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A thickness precision measurement device based on a quantum interferometer, comprising an entangled photon source (1), a polarization beam splitter, a reflector group, and a single-mode optical fiber group, wherein the reflector group comprises a first reflector (3), a second reflector (7), a third reflector (10), a fourth reflector (11), a fifth reflector (14), and a sixth reflector (15), wherein the single-mode optical fiber group comprises a first single-mode optical fiber (12) and a second single-mode optical fiber (16), wherein the polarization beam splitter comprises a first polarization beam splitter (2) and a second polarization beam splitter (9), each having four ports, wherein the vertical polarization component of the light input into the first polarization beam splitter (2) is output through the fourth port, and the horizontal polarization component is output through the second port, wherein the two output ports are respectively connected to the first reflector (3) and the second reflector (7), wherein the second reflector (7) is located on a movable stepping motor (20), and the reflected light is respectively output through a first 810 nm quarter wave plate (4) and a second 810 nm quarter wave plate (5). The invention relates to a method for producing a polarization signal transmission device for transmitting the polarization signal of the optical fiber to the first polarization beam splitter (2). The polarization signal transmission device comprises a first polarization signal transmission device and a second polarization signal transmission device. The first polarization signal transmission device comprises a first polarization signal transmission device and a second polarization signal transmission device. The first polarization signal transmission device comprises a first polarization signal transmission device and a second polarization signal transmission device. The first polarization signal transmission device comprises a first polarization signal transmission device and a second polarization signal transmission device. The first polarization signal transmission device comprises a first polarization signal transmission device and a second polarization signal transmission device. The first polarization signal transmission device comprises a first polarization signal transmission device and a second polarization signal transmission device. The first polarization signal transmission device comprises a first polarization signal transmission device and a second polarization signal transmission device. The first polarization signal transmission device comprises a first polarization signal transmission device and a second polarization signal transmission device.

2. The device for precise thickness measurement based on quantum interferometer according to claim 1, characterized in that: The stepping motor (20) is used to compensate for the optical path difference introduced by the sample being measured.

3. The device for precise thickness measurement based on quantum interferometer according to claim 1, characterized in that: It also comprises a coincidence counter (18), the coincidence counter (18) being connected to the first single-photon detector (13) and the second single-photon detector (17), and the coincidence counter (18) being used for measuring coincidence counts.

4. The device for precise thickness measurement based on quantum interferometer according to claim 3, characterized in that: It also includes a computer (19), the computer (19) being electrically connected to the coincidence counter (18), the computer (19) being electrically connected to the stepping motor (20), and the computer (19) being used to control the movement, data processing and image display of the stepping motor (20).

5. The device for precise thickness measurement based on quantum interferometer according to claim 4, characterized in that: The horizontally polarized light output from the second port of the second polarization beam splitter (9) is coupled into and transmitted through the second single-mode optical fiber (16), and the vertically polarized light output from the fourth port is coupled into and transmitted through the first single-mode optical fiber (12).

6. The device for precise thickness measurement based on quantum interferometer according to claim 1, characterized in that: The entangled photon source (1) is used to provide a stable output of correlated photon pairs, that is, output of signal photons and idler photons having a quantum correlation relationship. The output end of the entangled photon source (1) is connected to a first polarization beam splitter (2). The first polarization beam splitter (2) is used to split the light emitted by the entangled photon source (1) into two transmission paths.

7. A method for using a precision thickness measurement device based on a quantum interferometer, based on the precision thickness measurement device based on a quantum interferometer according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Build an entangled photon source and adjust the temperature to make the spectrum of signal photons and idler photons in the down-converted light degenerate; S2. When no signal or idler photon filter is added to the entangled photon source, the coupling of the spatial light to the single-mode optical fiber group is completed by relying on the residual pump light emitted from the entangled photon source; S3. After S2 is completed, signal photons and idler photon filters are added to the entangled photon source to filter the residual pump light, so that only signal photons and idler photons with a central wavelength of 810 nm exist in the subsequent optical path of the entangled photon source; S4, adding an 810nm half-wave plate (8), taking the optical path where the second reflector (7) is located as the standard, adjusting the third reflector (10), the fourth reflector (11), the fifth reflector (14), and the sixth reflector (15) so that the single count and coincidence count observed on the computer (19) are maximized, and the single photon counts on the two paths are equally divided; adjusting the first reflector (3) so that the single count observed on the computer (19) is maximized; S5, the computer (19) controls the stepping motor (20) to move, and the HOM interference curve is observed; S6. Place the sample (5) to be tested between the first 810nm quarter wave plate (4) and the first polarization beam splitter (2). Note that only about half of the light should pass through the sample. When the sample is placed in the light path, if it has only one thickness, then only half of the light should pass through the sample while the other half passes through free space. If it is a sample with multiple thicknesses, the light spot should be simultaneously projected onto different thicknesses of the sample, that is, for a sample with two thicknesses, half of the light spot should be projected onto one thickness of the sample and the other half onto the other thickness. S7, the computer (19) controls the stepping motor (20) to move again, and the HOM interference curve can be observed, which is composed of two HOM depressions at both ends and a convexity / concavity in the middle; S8. Repeat S7 several times to obtain repeated measurement data, and process the data to obtain sample thickness information.

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