A wide-range multi-parameter vacuum measuring device and method

Abstract

The application relates to the technical field of vacuum measurement, in particular to a wide-range multi-parameter vacuum measurement device and method. The device comprises a tunable diode laser, an electro-optic modulator, a Fabry-Perot cavity, a PDH frequency locking unit, an optical frequency comb light source, a beat frequency unit, a gas absorption cell and a pressure inversion calculation unit. The optical frequency comb light source comprises a first optical frequency comb light source and a second optical frequency comb light source. The outgoing light of the tunable diode laser enters the Fabry-Perot cavity for transmission. The PDH frequency locking unit locks the frequency of the probe laser. The first optical frequency comb light source emits reference light comb. The second optical frequency comb light source emits probe light comb. Part of the probe light comb passes through the gas absorption cell for interference, and the other part directly interferes. The pressure inversion calculation unit inversely obtains the gas pressure in the gas absorption cell. The application realizes full-pressure measurement of non-polar gas and full-pressure measurement and partial-pressure measurement of polar gas.

Description

Technical Field

[0001] This application relates to the field of vacuum measurement technology, and more specifically, to a wide-range, multi-parameter vacuum measurement device and method. Background Technology

[0002] The aerospace, semiconductor, atmospheric environment, and life sciences industries have all placed new demands on vacuum metrology, such as the continuous expansion of measurement ranges, the sustained increase in accuracy requirements, and the growing need for comprehensive parameter integration. While focusing on solving the accuracy problems of in-situ and special environments, the development of vacuum metrology also places higher demands on expanding the limits of existing vacuum measurements, integrating parameters, and improving accuracy.

[0003] Currently, the most common vacuum measuring instruments are mass spectrometers and capacitive thin-film vacuum gauges. However, mass spectrometers have drawbacks such as difficulty in calibration, alteration of gas composition, low resolution, and inability to directly measure rough low vacuum. Capacitive thin-film vacuum gauges measure pressure per unit area, but in some practical vacuum systems, directional flow and non-isothermal states exist, disrupting thermodynamic equilibrium. In such cases, pressure can no longer characterize the properties of the vacuum. In recent years, facing the historic transformation of the international metrology system, many metrological parameters have evolved from physical standards based on classical physics to "natural standards," i.e., quantum standards. New methods and concepts for reproducing vacuum values ​​based on the intrinsic physical properties of matter, such as optical interferometry and absorption spectroscopy, have the potential to break through the limits of traditional technical performance and have become a new research hotspot internationally.

[0004] Among them, optical interferometry uses PDH frequency locking and beat frequency technology to accurately measure the change in resonant laser frequency before and after gas filling in the Fabry-Perot cavity to obtain the gas refractive index, and then inversely calculates the total pressure of the nonpolar gas. Laser absorption spectroscopy determines the gas density by measuring the absorption loss of the target gas to light radiation, and further inversely calculates the total / partial pressure of the polar gas. However, vacuum measurements based on optical methods are limited to single-parameter measurements of total vacuum pressure or vacuum partial pressure, and cannot use a single instrument to simultaneously achieve wide-range, multi-parameter, high-precision, and rapid measurements of both total vacuum pressure and vacuum partial pressure. Summary of the Invention

[0005] This application provides a wide-range, multi-parameter vacuum measurement device and method, which can simultaneously measure the total pressure of non-polar gases and the total / partial pressure of polar gases.

[0006] To achieve the above objectives, this application provides a wide-range, multi-parameter vacuum measurement device, including a tunable diode laser, an electro-optic modulator, a Fabry-Perot cavity, a PDH frequency-locking unit, an optical frequency comb source, a beat frequency unit, a gas absorption cell, and a pressure inversion calculation unit. The optical frequency comb source includes a first optical frequency comb source and a second optical frequency comb source, with a self-reference unit disposed between them. The emitted light from the tunable diode laser is split into a probe laser and a reference laser by a first beam splitter. The probe laser, after being modulated by the electro-optic modulator, passes through the second beam splitter again and enters the Fabry-Perot cavity. Part of the laser is transmitted and received by a first photodetector, while the other part is reflected, passes through the second beam splitter and the first reflector, and is then received by a second photodetector. The PDH frequency-locking unit operates according to the modulation of the electro-optic modulator. The reflected signal received by the first and second photodetectors is used to lock the frequency of the probe laser. The first optical frequency comb source emits a reference optical comb, which is coupled with the reference laser and then subjected to beat frequency detection by the beat frequency unit. The second optical frequency comb source emits a probe optical comb. After passing through the seventh beam splitter, part of the probe optical comb enters the gas absorption cell as a spectral detection branch. After interacting with the sample gas in the gas absorption cell, it couples with the reflected reference optical comb and interferes, generating a beat frequency signal that is received by the third photodetector. The other part acts as a light intensity monitoring branch and couples directly with the reflected reference optical comb without passing through the gas absorption cell, generating a beat frequency signal that is received by the fourth photodetector. The pressure inversion calculation unit can obtain the spectral absorption curve of the sample gas in the gas absorption cell based on the signals received by the third and fourth photodetectors, thereby inverting the gas pressure in the gas absorption cell.

[0007] Furthermore, the wavelength tuning range of the tunable diode laser is 765-805nm, and the linewidth is <10KHz.

[0008] Furthermore, the Fabry-Perot chamber is a vacuum chamber used to introduce the non-polar gas to be measured; the gas absorption cell is a multi-pass vacuum chamber used to introduce the polar gas to be measured.

[0009] Furthermore, the optical frequency comb light source is formed by the difference frequency of a 1555 nm erbium-doped fiber optical frequency comb and a 1064 nm laser, with a comb tooth linewidth of 10 kHz and an output energy of 30 mW.

[0010] Furthermore, it also includes a temperature measurement and control unit, which is connected to the Fabry-Perot cavity and the gas absorption cell respectively, and is used to control and measure the temperature inside the Fabry-Perot cavity and the gas absorption cell.

[0011] Furthermore, this application also provides a method for using a wide-range multi-parameter vacuum measurement device, comprising the following steps: Step 1: Locking the probe laser frequency within the Fabry-Perot cavity using a PDH frequency-locking unit, and controlling the temperature within the Fabry-Perot cavity at the zero expansion point of the cavity material using a temperature control unit; Step 2: Evacuating the Fabry-Perot cavity, and measuring the initial state frequency of the probe laser and the initial state beat frequency of the reference laser and the reference optical comb within the cavity; Step 3: Filling the Fabry-Perot cavity with the gas to be measured, and measuring the final state frequency of the probe laser and the initial state beat frequency of the reference laser and the reference optical comb within the cavity. Step 4: Obtain the gas refractive index based on the change in the beat frequency of the reference laser and the reference optical comb before and after gas filling, thereby obtaining the vacuum degree in the Fabry-Perot cavity; Step 5: Evacuate the gas absorption cell and obtain the background spectrum and the light intensity distribution of the light intensity monitoring branch in the absorption cell; Step 6: Fill the gas absorption cell with the sample gas and obtain the sample spectrum of the sample gas to be tested and the light intensity distribution of the light intensity monitoring branch in the absorption cell; Step 7: Compare the sample spectrum with the background spectrum to obtain the characteristic absorption peak data of the sample gas, and calculate the target gas pressure value after performing linear fitting on the absorption peak data.

[0012] Furthermore, in step 3, the gas to be tested is a non-polar pure gas.

[0013] Furthermore, in step 6, the sample gas is either a polar pure gas or a polar mixed gas. When the sample gas is a polar pure gas, the measurement result is the total pressure of the sample gas; when the sample gas is a polar mixed gas, the measurement result is the partial pressure of the target gas in the polar mixed gas.

[0014] Furthermore, in step 4, the nonpolar gas vacuum measurement range based on the gas refractive index is 10 Pa - 10 Pa. 5 Pa.

[0015] Furthermore, in step 7, the absorption peak data are fitted with a line shape using Gauss, Voigt, or Lorentz line shape functions; the measurement range for the total pressure of polar pure gas or the partial pressure of polar mixed gas based on the laser absorption spectrum is 10. -4 Pa-10 5 Pa.

[0016] The present invention provides a wide-range, multi-parameter vacuum measurement device and method, which has the following beneficial effects: 1. This application uses the same optical frequency comb light source as the frequency reference, which saves costs and space. By measuring the change in resonant laser frequency before and after the Fabry-Perot cavity is filled with gas, the gas refractive index information can be obtained. By measuring the attenuation of the optical comb intensity after passing through the gas absorption cell, the absorption spectrum information of the nonpolar gas can be obtained. It can simultaneously realize the full pressure measurement of nonpolar gas and the full / partial pressure measurement of polar gas. 2. This application uses an optical method to measure the vacuum level by measuring the gas density, eliminating the influence of macroscopic parameter instability. While reducing measurement uncertainty, it can realize the flat transmission of vacuum value and provide a new traceability method for vacuum value. 3. This application uses a light intensity monitoring branch to obtain light intensity fluctuation information and uses the light source intensity distribution curve to correct the spectral intensity error caused by light intensity fluctuation, thereby realizing the accurate measurement of gas characteristic absorption peaks. By utilizing the advantage of the optical frequency comb to broaden the spectral coverage, multiple absorption peaks can be used to invert the partial pressure of each gas. Averaging the multiple partial pressure values ​​obtained by inversion can effectively suppress random errors in the measurement process and also enable parallel measurement of multiple gases. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application. In the drawings: Figure 1 This is a schematic diagram of a wide-range multi-parameter vacuum measuring device provided according to an embodiment of this application; In the diagram: 1-Tunable diode laser, 2-First beam splitter, 4-Second beam splitter, 11-Third beam splitter, 12-Fourth beam splitter, 16-Fifth beam splitter, 19-Sixth beam splitter, 22-Seventh beam splitter, 24-Eighth beam splitter, 3-Electro-optic modulator, 5-Fabry-Perot cavity, 6-First photodetector, 8-Second photodetector, 25-Third photodetector, 20-Fourth photodetector, 7-First mirror, 15-Second mirror, 17-Third mirror, 18-Fourth mirror, 9-PDH frequency locking unit, 10-First optical frequency comb source, 21-Second optical frequency comb source, 13-Beat frequency unit, 14-Self-reference unit, 23-Gas absorption cell, 26-Pressure inversion calculation unit. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0021] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0022] In addition, the term "multiple" should mean two or more.

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] like Figure 1As shown, this application provides a wide-range multi-parameter vacuum measurement device, including a tunable diode laser 1, an electro-optic modulator 3, a Fabry-Perot cavity 5, a PDH frequency-locking unit 9, an optical frequency comb light source, a beat frequency unit 13, a gas absorption cell 23, and a pressure inversion calculation unit 26. The optical frequency comb light source includes a first optical frequency comb light source 10 and a second optical frequency comb light source 21, with a self-reference unit 14 disposed between the first optical frequency comb light source 10 and the second optical frequency comb light source 21. The emitted light from the tunable diode laser 1 is split into a probe laser and a reference laser by a first beam splitter 2. The probe laser, after being modulated by the electro-optic modulator 3, passes through a second beam splitter 4 and enters the Fabry-Perot cavity 5. Part of it is transmitted and received by a first photodetector 6, while the other part is reflected and passes through the second beam splitter 4 and a first reflector 7 before being received by a second photodetector 8. The PDH frequency-locking unit 9 operates according to the modulation signal of the electro-optic modulator 3. The reflected signal received by the second photodetector 8 is used to lock the frequency of the probe laser; the first optical frequency comb source 10 emits a reference optical comb, which is coupled with the reference laser and then subjected to beat frequency detection by the beat frequency unit 13; the second optical frequency comb source 21 emits a probe optical comb, which, after passing through the seventh beam splitter 22, is used as a spectral detection branch to enter the gas absorption cell 23. After interacting with the sample gas in the gas absorption cell 23, it is coupled with the reflected reference optical comb and interferes, and the resulting beat frequency signal is received by the third photodetector 25; the other part is used as a light intensity monitoring branch and is directly coupled with the reflected reference optical comb without passing through the gas absorption cell 23 and interferes, and the resulting beat frequency signal is received by the fourth photodetector 20; the pressure inversion calculation unit 26 can obtain the spectral absorption curve of the sample gas in the gas absorption cell 23 based on the signals received by the third photodetector 25 and the fourth photodetector 20, thereby inverting the gas pressure in the gas absorption cell 23.

[0025] Specifically, the wide-range multi-parameter vacuum measurement device provided in this application uses the same optical comb as the frequency reference for optical vacuum measurement. It accurately measures the change in resonant laser frequency before and after gas filling in the Fabry-Perot cavity 5 using PDH frequency locking and beat frequency technology to obtain the gas refractive index. Simultaneously, it obtains the spectral absorption curve by measuring the absorption loss of the target gas to light radiation, achieving both total pressure measurement of non-polar gases and total / partial pressure measurement of polar gases. The tunable diode laser 1 emits a narrow-linewidth laser with tunable wavelength, which is split into two beams by the first beam splitter 2. One beam serves as the probe laser, entering the Fabry-Perot cavity 5 for gas refractive index measurement, while the other beam serves as the reference laser, beating with the reference optical comb. The optical frequency comb light source includes a first optical frequency comb light source 10 and a second optical frequency comb light source 21. The first optical frequency comb light source 10 emits the reference optical comb, and the second optical frequency comb light source 21 emits the probe optical comb. The reference optical comb beats with both the reference laser and the probe optical comb, while the probe optical comb enters the gas absorption cell 23 for gas absorption spectrum measurement. The self-reference unit 14 is used to achieve optical comb locking, that is, locking the repetition rate and offset frequency of the optical comb to the frequency standard, which can ensure the precise positioning of the optical comb teeth. The reference optical frequency comb light source can be used to beat the reference laser, obtain the beat signal, and measure the refractive index within the Fabry-Perot cavity 5. It can also interfere with the light intensity monitoring branch to monitor the light intensity fluctuations of the optical comb light source, and can be used to perform dual-comb nonlinear asynchronous optical sampling and recording of interferograms with the spectral detection branch, thereby obtaining the background spectrum and gas absorption spectrum information of the sample gas in the gas absorption cell 23. The electro-optic modulator 3 is used to modulate the probe laser to generate sidebands. The Fabry-Perot cavity 5 is used to introduce the nonpolar gas to be detected. Multiple photodetectors are used to receive the probe light signal and reference light signal passing through the Fabry-Perot cavity 5 and the gas absorption cell 23, and synchronously measure the spectral intensity of the light source through the reference optical comb, using it as a reference signal for baseline correction of the absorption spectrum signal. The PDH frequency-locking unit 9 is mainly used to lock the probe laser onto the longitudinal mode of the Fabry-Perot cavity 5 through feedback control. Specifically, the process includes: mixing the modulation signal from the electro-optic modulator 3 with the reflection signal from the Fabry-Perot cavity 5 to generate an error signal; after adjusting the error signal, sending it to a proportional-integral-differential (PID) feedback controller; and adjusting the PID feedback bandwidth and gain to apply the signal to the piezoelectric ceramic and current control of the laser, thereby compensating for the laser's output frequency and ultimately achieving frequency locking. The beat frequency unit 13 is used to measure the beat frequency between the reference laser and the reference optical comb. The gas absorption cell 23 is used to introduce the polar gas to be detected. The pressure inversion calculation unit 26 obtains the spectral absorption curve of the gas to be tested by comparing the spectral data before and after gas introduction into the gas absorption cell 23, and then inverts the gas pressure.

[0026] Furthermore, the wavelength tuning range of the tunable diode laser 1 is 765-805nm, and the linewidth is <10kHz. The wavelength tuning range and linewidth of the tunable diode laser 1 can be selected according to actual conditions. In the embodiments of this application, the wavelength tuning of the tunable diode laser 1 is preferably 780nm, which has relatively superior performance, while the linewidth is <10kHz, and the narrow linewidth is beneficial to improving measurement accuracy.

[0027] Furthermore, Fabry-Perot chamber 5 is a vacuum chamber used to introduce the non-polar gas to be measured; gas absorption cell 23 is a multi-pass vacuum chamber used to introduce the polar gas to be measured.

[0028] Specifically, Fabry-Perot cavity 5 is a vacuum cavity, mainly used for measuring the pressure of non-polar gases. The measurement process is as follows: Fabry-Perot cavity 5 is evacuated to a vacuum, and the initial frequency of the laser and the initial beat frequency between the laser and the reference optical comb are obtained; the non-polar gas to be measured is filled into Fabry-Perot cavity 5, and the final frequency of the laser and the final beat frequency between the laser and the reference optical comb are obtained; the gas refractive index is obtained based on the change in the beat frequency between the laser and the reference optical comb before and after filling, and then the vacuum level in Fabry-Perot cavity 5 is obtained by inversion. Gas absorption cell 23 is a multi-pass vacuum cavity, mainly used for measuring the pressure of polar gases. The measurement is mainly divided into two parts: background spectrum measurement (without sample gas) and sample spectrum measurement. The characteristic absorption curve of the polar gas to be measured is obtained by comparing the sample spectrum with the background spectrum, and finally the gas pressure is obtained through the pressure inversion calculation unit 26.

[0029] Furthermore, the optical frequency comb light source is formed by differential frequency conversion of a 1555 nm erbium-doped fiber optical frequency comb and a 1064 nm laser, with a comb tooth linewidth of 10 kHz and an output energy of 30 mW. The optical frequency comb light source can be either a near-infrared optical frequency comb or a mid-infrared optical frequency comb, depending on the actual situation. In this embodiment, the optical frequency comb light source is preferably formed by differential frequency conversion of a 1555 nm erbium-doped fiber optical frequency comb and a 1064 nm laser, which has superior performance. The preferred comb tooth linewidth is 10 kHz, as the narrow linewidth is beneficial for improving measurement accuracy. The output energy of 30 mW meets the measurement requirements, and the differential frequency conversion of these two lasers can obtain a 3.3-micron mid-infrared optical frequency comb, achieving beat frequency conversion.

[0030] Furthermore, it also includes a temperature control unit, which is connected to both the Fabry-Perot cavity 5 and the gas absorption cell 23, and is used to control and measure the temperature inside the Fabry-Perot cavity 5 and the gas absorption cell 23. The temperature control unit can perform dual-layer temperature control on the Fabry-Perot cavity 5 and the gas absorption cell 23, and after temperature control, the temperature fluctuation is less than 1 mK.

[0031] Furthermore, embodiments of this application also provide a method for using a wide-range multi-parameter vacuum measuring device, comprising the following steps: Step 1: Use the PDH frequency locking unit 9 to lock the probe laser frequency in the Fabry-Perot cavity 5, and use the temperature control unit to control the temperature in the Fabry-Perot cavity 5 at the zero expansion point of the cavity material; Step 2: Evacuate Fabry-Perot cavity 5 and measure the initial frequency of the probe laser and the initial beat frequency of the reference laser and the reference optical comb within the cavity; Step 3: Fill the Fabry-Perot cavity 5 with the gas to be tested, and measure the final state frequency of the probe laser and the final state beat frequency of the reference laser and the reference optical comb in the cavity; wherein, the gas to be tested is a non-polar pure gas; Step 4: Obtain the gas refractive index based on the beat frequency changes of the reference laser and reference optical comb before and after gas filling, thereby obtaining the vacuum level within the Fabry-Perot cavity 5; the non-polar gas vacuum measurement range based on the gas refractive index is 10 Pa - 10 Pa. 5 Pa; Step 5: Evacuate the gas absorption cell 23 to obtain the background spectrum and light intensity distribution of the light intensity monitoring branch in the absorption cell; Step 6: Fill the gas absorption cell 23 with the sample gas and obtain the sample spectrum and light intensity distribution of the light intensity monitoring branch of the sample gas to be tested in the absorption cell; wherein, the sample gas is a polar pure gas or a polar mixed gas. When the sample gas is a polar pure gas, the measurement result is the total pressure of the sample gas; when the sample gas is a polar mixed gas, the measurement result is the partial pressure of the target gas in the polar mixed gas. Step 7: Compare the sample spectrum with the background spectrum to obtain the characteristic absorption peak data of the sample gas. Use the Gauss, Voigt, or Lorentz line shape function to perform line fitting on the absorption peak data. Calculate the target gas pressure value after fitting. The measurement range for the total pressure of polar pure gas or the partial pressure of polar mixed gas based on the laser absorption spectrum is 10. -4 Pa-10 5 Pa.

[0032] Specifically, combining the device itself and the application method, the measurement process of this application embodiment is as follows: The Fabry-Perot cavity is first subjected to double-layer temperature control by the temperature measurement and control unit. After temperature control, the temperature fluctuation is less than 1mK. The output light of the tunable diode laser 1 is split into two beams by the first beam splitter 2. One beam is used as the probe laser and the other is used as the reference laser. The probe laser enters the electro-optic modulator 3 for phase modulation to generate sidebands. After passing through the second beam splitter 4, it enters the Fabry-Perot cavity 5. After 5% of the laser is transmitted, it is received by the first photodetector 6. After 95% of the laser is reflected, it is reflected by the second beam splitter 4 and the first reflector 7 and then received by the second photodetector 8. The PDH frequency locking unit 9 locks the frequency of the probe laser according to the modulation signal of the electro-optic modulator 3 and the reflection signal received by the second photodetector 8. The reference optical comb emitted by the first optical frequency comb light source 10 is split into two beams by the third beam splitter 11. One beam is coupled with the reference laser through the fourth beam splitter 12 and then the beat frequency is detected by the beat frequency unit 13. After evacuating the Fabry-Perot cavity 5, the initial frequency of the probe laser and the initial beat frequency of the reference laser and the reference optical comb are measured. After filling the Fabry-Perot cavity 5 with non-polar pure gas to a predetermined pressure, the final frequency of the probe laser and the final beat frequency of the reference laser and the reference optical comb are measured. The gas refractive index is obtained based on the change in the beat frequency of the laser and the reference optical comb before and after filling the cavity with gas, and then the vacuum degree of the gas in the Fabry-Perot cavity 5 is obtained by inversion. The detector light comb emitted by the second optical frequency comb source 21, after passing through the seventh beam splitter 22, has two parts. One part serves as a spectral detection branch, entering the gas absorption cell 23 and interacting fully with the sample gas (polar pure gas or polar mixed gas). This interacts with the reference light comb reflected by the second mirror 15, the fifth beam splitter 16, and the third mirror 17 via the eighth beam splitter 24, generating a beat frequency signal which is received by the third photodetector 25. The other part serves as a light intensity monitoring branch, bypassing the gas absorption cell 23 and directly passing through the fourth mirror 18 and the sixth beam splitter 19. It then interacts with the reference light comb reflected by the second mirror 15 and the fifth beam splitter 16, generating a beat frequency signal which is received by the fourth photodetector 20. The output of the fourth photodetector 20 is the reference light intensity signal without sample gas absorption attenuation. This spectral signal is used as a reference signal for baseline correction of the absorption spectral signal. The output of the third photodetector 25 is the sampled light intensity signal after sample gas absorption. The pressure inversion calculation unit 26 corrects the heterodyne interference signal based on the signal received by the third photodetector and the light intensity received by the fourth photodetector, compares the spectral data before and after the gas absorption cell is filled, obtains the spectral absorption curve of the sample gas in the gas absorption cell, and uses Gauss, Voigt or Lorentz line shape functions to perform line fitting on the absorption peak data, thereby inverting and calculating the gas pressure in the gas absorption cell.

[0033] More specifically, the wide-range multi-parameter vacuum measurement device and method provided in this application uses an optical method to achieve precise measurement of gas density, and then inversely derives the vacuum value. While reducing measurement uncertainty, it can achieve flattened transmission of vacuum value, providing a new traceability path for vacuum value. At the same time, it uses the same optical frequency comb light source as the frequency reference for vacuum measurement by refractive index method and laser absorption spectroscopy method, which can simultaneously realize full pressure measurement of non-polar gases and full / partial pressure measurement of polar gases over a wide range, thereby achieving wide-range, multi-parameter, high-precision, and low-cost vacuum measurement.

[0034] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A wide-range, multi-parameter vacuum measuring device, characterized in that, It includes a tunable diode laser, an electro-optic modulator, a Fabry-Perot cavity, a PDH frequency-locking unit, an optical frequency comb source, a beat frequency unit, a gas absorption cell, and a pressure inversion calculation unit, wherein: The optical frequency comb light source includes a first optical frequency comb light source and a second optical frequency comb light source, and a self-reference unit is provided between the first optical frequency comb light source and the second optical frequency comb light source. The emitted light from the tunable diode laser is split into a probe laser and a reference laser by the first beam splitter. The probe laser is modulated by the electro-optic modulator and then enters the Fabry-Perot cavity after passing through the second beam splitter. Part of it is transmitted and received by the first photodetector, and the other part is reflected and passed through the second beam splitter and the first reflector and received by the second photodetector. The PDH frequency-locking unit locks the frequency of the probe laser based on the modulation signal of the electro-optic modulator and the reflected signal received by the second photodetector. The first optical frequency comb light source emits a reference optical comb, which is coupled with a reference laser and then subjected to beat frequency detection through the beat frequency unit; The second optical frequency comb source emits a probe optical comb. After passing through the seventh beam splitter, part of the probe optical comb enters the gas absorption cell as a spectral detection branch. After interacting with the sample gas in the gas absorption cell, it couples with the reflected reference optical comb and interferes. The resulting beat frequency signal is received by the third photodetector. The other part, as a light intensity monitoring branch, couples directly with the reflected reference optical comb without passing through the gas absorption cell and interferes. The resulting beat frequency signal is received by the fourth photodetector. The pressure inversion calculation unit can obtain the spectral absorption curve of the sample gas in the gas absorption cell based on the signals received by the third photodetector and the fourth photodetector, thereby inverting the gas pressure in the gas absorption cell.

2. The wide-range multi-parameter vacuum measuring device according to claim 1, characterized in that, The wavelength tuning range of the tunable diode laser is 765-805nm, and the linewidth is <10KHz.

3. The wide-range multi-parameter vacuum measuring device according to claim 1, characterized in that, The Fabry-Perot chamber is a vacuum chamber used to introduce the non-polar gas to be measured; the gas absorption cell is a multi-pass vacuum chamber used to introduce the polar gas to be measured.

4. The wide-range multi-parameter vacuum measuring device according to claim 1, characterized in that, The optical frequency comb light source is formed by the difference frequency of a 1555 nm erbium-doped fiber optical frequency comb and a 1064 nm laser, with a comb tooth linewidth of 10 kHz and an output energy of 30 mW.

5. The wide-range multi-parameter vacuum measuring device according to claim 3, characterized in that, It also includes a temperature measurement and control unit, which is connected to the Fabry-Perot cavity and the gas absorption cell respectively, and is used to control and measure the temperature inside the Fabry-Perot cavity and the gas absorption cell.

6. A method for using the wide-range multi-parameter vacuum measuring device according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Use the PDH frequency locking unit to lock the probe laser frequency in the Fabry-Perot cavity, and use the temperature control unit to control the temperature in the Fabry-Perot cavity at the zero expansion point of the cavity material; Step 2: Evacuate the Fabry-Perot cavity and measure the initial frequency of the probe laser and the initial beat frequency of the reference laser and the reference optical comb within the cavity; Step 3: Fill the Fabry-Perot cavity with the gas to be tested, and measure the final state frequency of the probe laser and the final state beat frequency of the reference laser and the reference optical comb in the cavity; Step 4: Obtain the gas refractive index based on the beat frequency changes of the reference laser and reference optical comb before and after gas filling, thereby obtaining the vacuum level inside the Fabry-Perot cavity; Step 5: Evacuate the gas absorption cell and obtain the background spectrum and light intensity distribution of the light intensity monitoring branch in the absorption cell; Step 6: Fill the gas absorption cell with the sample gas and obtain the sample spectrum of the sample gas to be tested and the light intensity distribution of the light intensity monitoring branch in the absorption cell. Step 7: Compare the sample spectrum with the background spectrum to obtain the characteristic absorption peak data of the sample gas. After performing linear fitting on the absorption peak data, calculate the target gas pressure value.

7. The method for using a wide-range multi-parameter vacuum measuring device according to claim 6, characterized in that, In step 3, the gas to be tested is a non-polar pure gas.

8. The method for using a wide-range multi-parameter vacuum measuring device according to claim 6, characterized in that, In step 6, the sample gas is either a polar pure gas or a polar mixed gas. When the sample gas is a polar pure gas, the measurement result is the total pressure of the sample gas; when the sample gas is a polar mixed gas, the measurement result is the partial pressure of the target gas in the polar mixed gas.

9. The method for using a wide-range multi-parameter vacuum measuring device according to claim 7, characterized in that, In step 4, the vacuum measurement range for nonpolar gases based on gas refractive index is 10 Pa - 10 Pa. 5 Pa.

10. The method for using a wide-range multi-parameter vacuum measuring device according to claim 8, characterized in that, In step 7, the absorption peak data are fitted with a Gaussian, Voigt, or Lorentz line shape function; the measurement range for the total pressure of polar pure gas or the partial pressure of polar mixed gas based on the laser absorption spectrum is 10. -4 Pa-10 5 Pa.

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