A dual resonance enhanced high sensitivity miniaturized resonant gas sensor

Abstract

A dual-resonance enhanced high-sensitivity miniaturized resonant gas sensor is based on a silicon cantilever beam combined with a silicon dioxide probe to detect sound waves. The silicon cantilever beam is small in size and can achieve a particularly wide frequency response. It matches the first-order resonant frequency corresponding to the size of the buffer chamber and the resonant cavity to achieve a dual resonance effect, so that confined spaces can be detected with high sensitivity. This miniaturized gas sensor does not require a large-volume temperature control device and has a simple structure, a very small volume, a fast response speed, and convenient installation. The unique design of the pores allows the entire sensor to fully penetrate the gas into the sensor during detection without occupying excess space. The silicon cantilever beam is combined with the silicon dioxide sensor head to form an F-P cavity, which further reduces the excess volume. In addition, the highly sensitive detection of trace gases is not affected when the volume is reduced, which provides a new idea for miniaturized resonant photoacoustic sensors and has great application prospects in the field of photoacoustic spectroscopy.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber sensing and trace gas detection, and relates to a dual resonance enhanced high-sensitivity miniaturized resonant gas sensor Background Art

[0002] Trace gas detection plays an important role in atmospheric environmental monitoring, industrial process control and life sciences. With the development of laser technology, photoacoustic spectroscopy has become a gas detection method with high sensitivity, fast response time and strong selectivity, and is widely used in trace gas detection. Photoacoustic spectroscopy is a spectral calorimetric technology that directly measures the heat energy generated by the gas due to the absorption of light energy. It is a background-free absorption spectroscopy technology. For traditional photoacoustic spectroscopy systems, since the sound waves are generated in a closed photoacoustic cell, and the traditional photoacoustic cell must be matched with a microphone and an excitation light source, the entire photoacoustic spectroscopy system is large in size, and it is difficult to achieve high-sensitivity detection in places with limited space. Based on this, the literature Y.Cao, W.Jin, HLHo, J.Ma, Miniature fiber-tip photoacoustic spectrometer for trace gas detection, Opt.Lett.38(4)(2013)434-436.K.Chen et al.Fiber-optic photoacoustic sensor for remote monitoring of gas micro-leakage.Optics Express27(4)(2019)434-436. respectively designed a miniaturized photoacoustic spectroscopy gas detection system, which greatly reduced the volume. However, since the system uses a non-resonant photoacoustic cell as the place to generate photoacoustic signals, the gas detection sensitivity is several orders of magnitude different from that of the resonant photoacoustic spectroscopy system. Based on this, the document Z. Gong et al. All-optical high-sensitivity resonant photoacoustic sensor for remote CH4 gas detection [J]. Optics Express, 2021, 29 (9): 13600-13609 designed an all-optical resonant gas sensor for high-sensitivity detection of trace gases. However, since the cantilever beam is made of stainless steel, it is not possible to perform high-sensitivity detection of trace gases at high frequencies, which further limits the length and diameter of the resonant cavity and buffer chamber, and the overall volume needs to be further optimized.

[0003] In the system for detecting trace gases using photoacoustic spectroscopy, a photoacoustic cell is generally used as the sound wave generating unit. Existing photoacoustic cells are divided into two types, one is a resonant photoacoustic cell and the other is a non-resonant photoacoustic cell. The characteristics of the non-resonant photoacoustic cell are small size and good portability, but the non-resonant photoacoustic cell also has some disadvantages. The most prominent disadvantage is that the gas detection sensitivity is several orders of magnitude different from that of the resonant photoacoustic spectroscopy system. The advantages of the resonant photoacoustic cell are high sensitivity and strong noise suppression ability, but the volume of the resonant photoacoustic cell is generally several times or even hundreds or thousands of times that of the non-resonant photoacoustic cell, which also limits the use of the resonant photoacoustic cell. In summary, it is of great application value to design a resonant photoacoustic spectroscopy gas sensor that can be comparable to the volume of a non-resonant photoacoustic cell and can achieve high-sensitivity detection of trace gases. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a dual resonance enhanced high-sensitivity miniaturized resonant gas sensor. The overall volume of the gas sensor is comparable to that of a non-resonant sensor, and it can achieve high-sensitivity detection of trace gases, providing a new idea for miniaturized resonant photoacoustic sensors and having great application prospects in the field of photoacoustic spectroscopy.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A double resonance enhanced high-sensitivity miniaturized resonant gas sensor. On the basis of a traditional double resonance enhanced resonant gas sensor (K. Chen, H. Deng, M. Guo, C. Luo, S. Liu, B. Zhang, F. Ma, F. Zhu, Z. Gong, W. Peng, Q. Yu, Tube-cantilever double resonance enhanced fiber-optic photoacoustic spectrometer, Opt. Laser Technol. 123 (2020), 105894.), the length and diameter of the buffer chamber and the resonant cavity are further determined: the length of the buffer chamber 2 and the resonant cavity 3 are both 18 mm, the diameter of the buffer chamber 2 is 12 mm, and the diameter of the resonant cavity 3 is 4 mm; the acoustic sensor head is designed as an integrated sensor probe 4, which is mainly composed of a single-mode optical fiber 9, a silica sensor head 10 and a silicon cantilever beam 13; the diameter of the silica sensor head 10 is 3.5 mm, and a conical cavity is provided inside it and the volume of the cavity is 6.2 mm 3 The length of the silicon cantilever beam 13 is 1.1 mm, the width is 0.4 mm, and the thickness is 4.1 um. The silicon cantilever beam based on this special design combined with the silicon dioxide probe makes the cantilever beam have a particularly wide frequency response.

[0007] The upper radius of the conical cavity is 1.6 mm, the lower radius is 0.1 mm, and the height is 2.16 mm.

[0008] Compared with the conventional dual resonance enhanced resonant gas sensor, the optimized dual resonance enhanced high-sensitivity miniaturized resonant gas sensor can achieve the dual resonance enhancement effect without the need for a large temperature control device.

[0009] Beneficial effects of the present invention:

[0010] The present invention provides a dual-resonance enhanced high-sensitivity miniaturized resonant gas sensor. Because a silicon cantilever beam processed by MEMS technology is used and combined with a specially designed conical cavity, the cantilever beam can achieve a particularly wide frequency response while maintaining a very high sensitivity, and it is easy to achieve a dual resonance effect by matching the resonant frequency corresponding to the resonant cavity. The acoustic sensor is based on a silicon cantilever beam combined with a silicon dioxide probe to detect sound waves. In addition, the silicon cantilever beam is small in size, can achieve a particularly wide frequency response, and match the first-order resonant frequency corresponding to the size of the buffer chamber and the resonant cavity to achieve a dual resonance effect, so that high-sensitivity detection can be performed on confined spaces.

[0011] Compared with the traditional dual-resonance enhanced resonant gas sensor, this miniaturized gas sensor does not require a large-volume temperature control device, has a simple structure, a volume of up to cubic centimeters, is easy to install, and has a unique pore design so that the gas fully penetrates into the sensor during detection without occupying excess space. The silicon cantilever beam is combined with the silicon dioxide sensor head to form an FP cavity, which further reduces the excess volume. Moreover, the highly sensitive detection of trace gases is not affected when the volume is reduced, which provides a new idea for miniaturized resonant photoacoustic sensors and has great application prospects in the field of photoacoustic spectroscopy. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of a dual resonance enhanced high-sensitivity miniaturized resonant gas sensor of the present invention.

[0013] Figure 2 It is a schematic diagram of the sensor probe of the present invention.

[0014] Figure 3 It is a schematic diagram of the cantilever beam diaphragm of the present invention.

[0015] Figure 4 It is the broadband response diagram of the cantilever beam of the present invention.

[0016] Figure 5 This is the sensitivity diagram of the cantilever beam corresponding to 4700Hz to 5000Hz.

[0017] In the figure: 1 shell; 2 buffer chamber; 3 resonant cavity; 4 sensor probe; 5 sealing cover; 6 air hole; 7 collimator; 8 gap 9 single-mode optical fiber; 10 silica sensor head; 11 F-P cavity; 12 silicon wafer 13 cantilever beam. DETAILED DESCRIPTION

[0018] 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.

[0019] Figure 1 Schematic diagram of a dual resonance enhanced high sensitivity miniaturized resonant gas sensor of the present invention. Figure 1 As shown, the dual resonance enhanced high-sensitivity miniaturized resonant gas sensor provided by the embodiment of the present invention includes a housing 1, a buffer chamber 2, a resonant cavity 3, a sensor probe 4, a sealing cover 5, an air hole 6, and a collimator 7.

[0020] The shell 1 is made of metal, and a buffer chamber 2 and a resonant cavity 3 are provided inside the shell;

[0021] A sealing cover 5 is provided at the end of the resonant cavity 3, and the sensing probe 4 is located at the center of the sealing cover 5 at the end of the resonant cavity 3 and is connected by gluing;

[0022] A sealing cover is provided at the end of the buffer chamber 2;

[0023] The collimator 7 is connected to the sealing cover 5 at the end of the buffer chamber 2 by gluing, and is used for calibration of the excitation light source;

[0024] The housing 1 and the ends of the resonance cavity 3 and the sealing cover 5 at the end of the buffer chamber 2 are provided with air holes 6, and a gap 8 is provided between the sealing cover 5 and the housing 1 for gas exchange.

[0025] The sizes of the buffer chamber 2 and the resonant cavity 3 are in the sub-centimeter level.

[0026] Furthermore, the lengths of the buffer chamber 2 and the resonant cavity 3 described in the embodiment of the present invention are both 18 mm, the diameter of the buffer chamber 2 is 12 mm, and the diameter of the resonant cavity 3 is 4 mm.

[0027] Furthermore, the first-order resonance frequency corresponding to the buffer chamber 2 and the resonance cavity 3 described in the embodiment of the present invention is 4740 Hz.

[0028] The sensor probe is composed of a silicon cantilever beam 13 made based on MEMS technology, a silicon dioxide probe 10, and a single-mode optical fiber 9. The single-mode optical fiber 9 and the silicon cantilever beam form an FP cavity 11, which further reduces the size of the sensor. The specific structural diagram is shown in FIG. Figure 2 and Figure 3 shown.

[0029] Furthermore, the length of the FP cavity 11 should be controlled between 0.5-0.1 mm in order to obtain higher sensitivity.

[0030] The diameter of the silica probe 10 is 3.5 mm, which is smaller than the diameter of the resonant cavity 3. There is a conical cavity inside the silica probe 10 and the volume of the cavity is 6.2 mm. 3 .

[0031] The upper radius of the conical cavity is 1.6 mm, the lower radius is 0.1 mm, and the height is 2.16 mm.

[0032] The silicon cantilever beam 13 manufactured based on MEMS technology has a length of 1.1 mm, a width of 0.4 mm, and a thickness of 4.1 um.

[0033] The size of the silicon cantilever beam 13 can only be combined with the conical cavity to obtain a high sensitivity with a resonance frequency of 4850 Hz and a particularly wide frequency response. The specific wide frequency response diagram of the cantilever beam is as follows: Figure 4 .

[0034] Furthermore, the particularly wide frequency response can ensure that the sensitivity is between 4740nm / Pa-4760nm / Pa under the premise of a frequency of 4700Hz to 5000Hz, and the fluctuation is not large. The sensitivity diagram of the cantilever beam corresponding to 4700Hz to 5000Hz is as follows: Figure 5 .

[0035] The specially designed silicon cantilever beam 13 has a particularly wide frequency response, so it is easy to match the first-order resonance frequency corresponding to the size of the buffer chamber 2 and the resonant cavity 3 to achieve a double resonance effect, thereby achieving high-sensitivity detection of trace gases.

[0036] Furthermore, the double resonance effect is based on the superposition of the photoacoustic signal of the cantilever beam and the photoacoustic signal corresponding to the size of the buffer chamber and the resonant cavity. Since the sensitivity of the silicon cantilever beam combined with the conical cavity at this size is nearly an order of magnitude higher than that of the cantilever beam made of ordinary material, the double resonance effect is nearly an order of magnitude higher than that of the single resonance.

[0037] Example 1

[0038] The traditional double resonance enhanced resonant gas sensor can refer to the literature K. Chen, H. Deng, M. Guo, C. Luo, S. Liu, B. Zhang, F. Ma, F. Zhu, Z. Gong, W. Peng, Q. Yu, Tube-cantilever double resonance enhanced fiber-optic photoacoustic spectrometer, Opt. Laser Technol. 123 (2020), 105894. The volume of the buffer chamber and the resonant cavity reaches 25 cubic centimeters, and the sensitivity of the cantilever beam at the resonant frequency is 2223.8 nm / Pa. The normalized equivalent noise coefficient applied to acetylene gas detection is 4×10 -10 cm -1 WHz -1 / 2 .

[0039] Example 2

[0040] Based on the conventional dual resonance enhanced resonant gas sensor of Example 1, the buffer chamber and the resonant cavity are optimized, the length of the buffer chamber 2 and the resonant cavity 3 are both 18 mm, the diameter of the buffer chamber 2 is 12 mm, and the diameter of the resonant cavity 3 is 4 mm. The volume of the optimized buffer chamber 2 and the resonant cavity 3 reaches 2.3 cubic centimeters, which is one tenth of the volume of the conventional buffer chamber and the resonant cavity.

[0041] Example 3

[0042] Based on the conventional dual resonance enhanced resonant gas sensor of Example 1, the acoustic sensor head is optimized into an integrated sensor probe 4, which is mainly composed of a single-mode optical fiber 9, a silica sensor head 10 and a silicon cantilever beam 13; the diameter of the silica sensor head 10 is 3.5 mm, and a conical cavity is provided inside it, and the volume of the cavity is 6.2 mm 3 The length of the silicon cantilever beam 13 is 1.1 mm, the width is 0.4 mm, and the thickness is 4.1 um. The optimized silicon cantilever beam has a particularly wide frequency response, and can ensure that the sensitivity is between 4740 nm / Pa and 4760 nm / Pa at a frequency of 4700 Hz to 5000 Hz, and the fluctuation is not large. In addition, the sensitivity of the optimized cantilever beam at the resonant frequency is twice the sensitivity of the cantilever beam in the literature at the resonant frequency.

[0043] Example 4

[0044] The optimization schemes of Example 2 and Example 3 are combined to form a dual resonance enhanced high-sensitivity miniaturized resonant gas sensor of the present invention, which has a normalized equivalent noise coefficient of 3.35×10 -10 cm -1 WHz -1 / 2 .

[0045] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A dual resonance enhanced high sensitivity miniaturized resonant gas sensor, characterized in that: The dual resonance enhanced high-sensitivity miniaturized resonant gas sensor comprises a shell (1), a buffer chamber (2), a resonant cavity (3), a sensing probe (4), a sealing cover (5), an air hole (6), and a collimator (7). The buffer chamber (2) and the resonant cavity (3) are provided inside the shell, and a sealing cover (5) is provided at the end of the resonant cavity (3); the sensing probe (4) is located at the center of the sealing cover (5) at the end of the resonant cavity (3) and is connected by gluing; a sealing cover is provided at the end of the buffer chamber (2); the collimator (7) is connected to the sealing cover (5) at the end of the buffer chamber (2) by gluing; the shell (1) ) and the resonant cavity (3), and the sealing cover (5) at the end of the buffer chamber (2) are provided with air holes (6), and a gap (8) is provided between the sealing cover (5) and the shell (1) for gas exchange; the lengths of the buffer chamber (2) and the resonant cavity (3) are both 18 mm, the diameter of the buffer chamber (2) is 12 mm, and the diameter of the resonant cavity (3) is 4 mm; the acoustic sensor head is designed as an integrated sensor probe (4), which is composed of a single-mode optical fiber (9), a silica sensor head (10) and a silicon cantilever beam (13); the diameter of the silica sensor head (10) is 3.5 mm, and a conical cavity is provided therein, and the volume of the cavity is 6.2 mm 3 The length of the silicon cantilever beam (13) is 1.1 mm, the width is 0.4 mm, and the thickness is 4.1 um; the upper radius of the conical cavity is 1.6 mm, the lower radius is 0.1 mm, and the height is 2.16 mm.

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