Calibration-free gas sensing chip based on infrared absorption spectrum technology

Abstract

The invention discloses a calibration-free gas sensing chip based on an infrared absorption spectrum technology. The calibration-free gas sensing chip comprises an on-chip laser light source, a transmission waveguide, an on-chip optical switch, a gas sensing waveguide array and an on-chip optical detector, the on-chip laser light source is arranged at the light input end of the transmission waveguide; the on-chip optical switch is arranged between the transmission waveguide and the gas sensing waveguide array; the gas sensing waveguide array is composed of a series of waveguides with different structural parameters, and light in the waveguides is in contact with environment gas through an evanescent field; and the on-chip optical detector is arranged at the light output end of the gas sensing waveguide array and is used for receiving the optical signal, converting the optical signal into an electric signal, inversely calculating the gas concentration through the electric signal and regulating and controlling the switching condition of the on-chip optical switch. The gas sensing chip has the gas concentration measurement advantages of high precision, self-calibration and the like, and lays a foundation for realizing the application of a miniaturized gas sensor.

Description

Technical Field

[0001] The invention relates to the field of integrated optoelectronics, and in particular to a calibration-free gas sensor chip based on infrared absorption spectroscopy technology. Background Art

[0002] Optical gas sensors have the advantages of high stability, fast response speed, strong anti-interference ability, and non-contact measurement. They are widely used in industrial production, environmental monitoring, medical health, military security and other fields. Among them, optical gas sensors based on infrared absorption spectroscopy can achieve high sensitivity and selective measurement of gas concentration in the environment according to the change in the absorption of light intensity by gas molecules. At the same time, the on-chip integrated optical sensor chip has the advantages of high integration, good portability, and low power consumption. It overcomes the limitations of discrete sensing systems that are large in size and difficult to integrate, but they are basically based on single-channel light transmission, which is not conducive to achieving high-precision, self-calibrated sensing. Therefore, it is of great value to develop a calibration-free gas sensor chip based on infrared absorption spectroscopy technology.

[0003] In terms of papers, in 2012, Wang Qi and others from Northeastern University developed a small sensitive gas sensor based on a slot-type photonic crystal waveguide (Sensors and Actuators B: Chemical 173, 505-509, 2012), which can achieve high-precision gas sensing under limited chip size. In 2017, L. Tombez and others from IBM Corporation of the United States proposed a gas sensor chip based on silicon-based spiral waveguide (Optica 4, 1322-1325, 2017), which can detect the concentration of ambient methane gas using infrared tunable diode laser absorption spectroscopy technology. In 2021, M. Vlk and others from the Arctic University of Norway used Ta2O5 as the core material of the sensor chip to develop an on-chip gas sensor for detecting C2H2 (Light: Science & Applications 10, 26, 2021), achieving gas concentration detection with a detection limit of 7ppm. In 2023, Wang Xueying and others from Jilin University studied suspended photonic crystal waveguide sensors and suspended ridge waveguide sensors based on InGaAs-InP platform (Acta Photonica Sinica 52, 1052414, 2023), and compared and discussed the possibility of integrating these two types of waveguide sensors with TM polarization devices and the influence of waveguide transmission loss on waveguide sensing performance. However, the gas concentration sensors proposed in the above work all use a single-channel on-chip optical path to realize gas sensing, which lacks anti-interference ability and is not conducive to improving detection sensitivity and signal-to-noise ratio.

[0004] In terms of patents, in 2015, Sun Xuhui and others from Jiangsu Zhiwen Intelligent Sensing Technology Co., Ltd. designed a method for preparing a multi-channel array gas sensor, which can flexibly drip different sensitive materials on the same substrate or on different substrates, and applied for a Chinese invention patent (201510329597.9). In 2020, Li Na and others from China Petrochemical Corporation invented a multi-parameter gas sensing microchip and its preparation method, which can realize complex atmosphere detection functions, with the advantages of reduced size, reduced power consumption, and improved integration, and applied for a Chinese invention patent (202010281584.X). In 2023, Zheng Shaonan and others from Shanghai University invented and disclosed a miniature infrared gas sensing device based on a hollow waveguide chip, which achieved more compact, better performance, and lower cost non-dispersive infrared gas sensing, and applied for a Chinese invention patent (202310634362.5). In the same year, Hou Chongguang and others from Xinlianxin (Hebei Xiong'an) Technology Co., Ltd. invented and disclosed an integrated gas sensor chip, which solved the problems of complex manufacturing process, high cost and large size of gas sensor chips, and applied for a Chinese invention patent (202311044176.2)

[0005] In summary, compared with discrete sensor systems, sensor chips have advantages such as miniaturization, low power consumption, and easy integration, but their detection accuracy is poor and the detection limit is high. Optical gas sensors using infrared absorption spectroscopy technology can improve sensitivity, selectivity, and response speed. However, their measured spectra are affected by changes in input light intensity, lack anti-aging capabilities, and cannot achieve self-calibration. Therefore, the development of a gas sensor chip that can achieve both high precision and self-calibration is of great significance for realizing high-performance chip-level sensing systems. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of low accuracy, poor stability and great calibration difficulty of traditional gas sensor chips, and to propose and manufacture a calibration-free gas sensor chip based on infrared absorption spectroscopy technology.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] A calibration-free gas sensor chip based on infrared absorption spectroscopy technology consists of an on-chip laser light source, a transmission waveguide, an on-chip optical switch, a gas sensor waveguide array and an on-chip optical detector; the on-chip laser light source is arranged at the light input end of the transmission waveguide; the on-chip optical switch is arranged between the transmission waveguide and the gas sensor waveguide array, and is used to select the light in the transmission waveguide to any waveguide in the gas sensor waveguide array; the gas sensor waveguide array consists of a plurality of waveguides with different structural parameters, and the light in the waveguide contacts with the ambient gas through an evanescent field; the on-chip optical detector is arranged at the light output end of the gas sensor waveguide array, and is used to receive the optical signal and convert it into an electrical signal, and invert the electrical signal to infer the gas concentration and regulate the switching condition of the on-chip optical switch.

[0009] Furthermore, the waveguide material in the calibration-free gas sensor chip is composed of one of silicon, germanium, a silicon-germanium mixture, silicon nitride, silicon carbide, indium phosphide, gallium arsenide, and lithium niobate.

[0010] Furthermore, the on-chip laser light source is any one of a nonlinear laser, a monolithic integrated laser, a hybrid integrated laser, and a heterogeneous integrated laser.

[0011] Furthermore, the on-chip optical switch is any one of a thermo-optical switch type, an electro-optical switch type, an acousto-optical switch type, a mechanical optical switch type, and a semiconductor optical amplifier optical switch type.

[0012] Furthermore, the gas sensing waveguide array includes two or more waveguides.

[0013] Furthermore, the difference between the waveguides with different structural parameters in the gas sensing waveguide array is any one or more combinations of length difference, thickness difference, width difference, material difference, whether the buried oxide layer is retained, and whether the oxide cladding is retained.

[0014] Furthermore, the transmission waveguide and gas sensing waveguide array can be used to propagate light fields in transverse electric mode or transverse magnetic mode.

[0015] The present invention also provides a method for measuring gas concentration in an environment, based on the calibration-free gas sensor chip and single-chip microcomputer, comprising:

[0016] The on-chip laser light source works and emits initial light, and the initial light is coupled into the transmission waveguide;

[0017] The light carries energy and propagates along the transmission waveguide to the on-chip optical switch, and selectively accesses one of the waveguides in the gas sensing waveguide array through the on-chip optical switch, so that the light enters the gas sensing waveguide array from the transmission waveguide through the on-chip optical switch;

[0018] When light propagates in the waveguide of the gas sensor waveguide array, it interacts with the gas in the environment through the evanescent field, causing the light energy in a certain wavelength band to be absorbed. The degree of absorption is proportional to the gas concentration in the environment.

[0019] The absorption spectrum signal carrying the information of the gas in the environment is received by the on-chip photodetector at the light output end and transmitted to the single-chip microcomputer; the single-chip microcomputer will determine whether the on-chip optical switch controls the light to traverse each waveguide in the sensing waveguide array;

[0020] If each waveguide has been traversed and the absorption spectrum information has been received, the spectrum information of all waveguides is sent to the single-chip microcomputer for processing; otherwise, the on-chip optical switch is adjusted to allow the light to enter other waveguides in the gas sensing waveguide array, and repeatedly propagate in the gas sensing waveguide array and be detected by the on-chip optical detector for the absorption spectrum signal;

[0021] The single-chip computer decodes all the output absorption spectrum information, eliminates abnormal data, fits the relationship between the output optical power and the waveguide length, and finally inverts and calculates the gas concentration in the environment and completes the measurement.

[0022] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0023] 1. The calibration-free gas sensor chip based on infrared absorption spectroscopy technology involved in the present invention has the advantages of high precision and high sensitivity. On the one hand, the infrared absorption spectroscopy technology is used to improve the accuracy, specificity and response speed of gas detection; on the other hand, the calibration-free gas sensor waveguide array is used to realize the truncation method measurement of the output light energy, and the gas concentration reading is obtained according to the slope of the measurement point fitting, which further improves the sensitivity of detection and enhances the anti-interference ability.

[0024] 2. The calibration-free gas sensor chip based on infrared absorption spectroscopy technology involved in the present invention does not require calibration, which improves the accuracy and reliability of the sensor in various environments. By measuring the slope of the output light energy changing with the waveguide length, the drift or accuracy problem caused by input light intensity fluctuation, laser aging or laser output light power decline is avoided. There is no need for downtime or manual intervention, which greatly extends the service life of the sensor chip, reduces maintenance costs, and improves applicability in a variety of complex environments.

[0025] 3. The calibration-free gas sensor chip based on infrared absorption spectroscopy technology involved in the present invention can realize automatic and intelligent optical channel selection and management. The on-chip integrated optical switch can isolate any faulty channel, reduce the impact of a single channel problem on the entire system, and significantly improve the stability of system operation.

[0026] 4. The calibration-free gas sensor chip based on infrared absorption spectroscopy technology involved in the present invention can realize targeted optical channel selection. The on-chip integrated optical switch is used to accurately select the optical path one by one, avoiding the decrease in input waveguide optical power and energy loss caused by the simultaneous splitting of multiple waveguides, thereby improving the detection performance of the gas sensor chip.

[0027] 5. The manufacturing process of the device of the present invention is compatible with the existing CMOS process, which is conducive to the large-scale mass production of the device and reduces the manufacturing cost. It provides technical support for the industrial application of high-performance integrated optoelectronic sensor chips, promotes the development of on-chip gas sensing technology, and is of great significance to promoting the application of integrated optoelectronic chips.

[0028] In summary, the present invention achieves a comprehensive improvement in the accuracy, sensitivity, stability and applicability of optical gas sensor chips, which is of great significance to the sensing needs in the fields of industry, environment, and medicine. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the structure of a calibration-free gas sensor chip based on infrared absorption spectroscopy technology;

[0030] Figure 2 A schematic diagram of the spectral response of a calibration-free gas sensor chip based on infrared absorption spectroscopy technology;

[0031] Figure 3 This is a functional principle flow chart of specific embodiment 1 of the present invention;

[0032] Figure 4 It is a schematic structural diagram of a gas sensing waveguide cross section according to a specific embodiment 1 of the present invention;

[0033] Figure 5 This is a graph showing the relationship between the gas concentration detection lower limit and the waveguide length of the gas sensor waveguide array when the input waveguide optical power is 1 mW, 0.25 mW, 0.125 mW and 0.0675 mW in specific embodiment 1 of the present invention;

[0034] Figure 6 This is a simulation result of the output optical power changing with the waveguide length when the input waveguide optical power is 1mW and the methane gas concentration is 500ppm in the specific embodiment 1 of the present invention;

[0035] Figure 7 It is a structural schematic diagram of the gas sensing waveguide cross section of specific embodiment 2 of the present invention;

[0036] Figure 8 This is a simulation result of the output optical power changing with the waveguide length when the input waveguide optical power is 1 mW and the methane gas concentration is 1000 ppm in the specific embodiment 2 of the present invention;

[0037] Fig. 9 It is a schematic structural diagram of a gas sensing waveguide cross section according to a specific embodiment 3 of the present invention;

[0038] Fig.10 This is a simulation result of the output optical power changing with the waveguide length when the input waveguide optical power is 1 mW and the methane gas concentration is 1000 ppm in the specific embodiment 3 of the present invention;

[0039] Figure numerals: 1. On-chip laser light source; 2. Transmission waveguide; 3. On-chip optical switch; 4. Gas sensing waveguide array; 5. On-chip photodetector. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] like Figure 1 The figure shows a calibration-free gas sensor chip based on infrared absorption spectroscopy technology protected by the present invention, wherein an on-chip laser light source 1 is arranged at the light input end of a transmission waveguide 2; an on-chip optical switch 3 is integrated between the transmission waveguide 2 and a gas sensor waveguide array 4; the gas sensor waveguide array 4 is composed of waveguide clusters with different structural parameters and is in contact with external gas; an on-chip light detector 5 is arranged at the light output end of the gas sensor waveguide array.

[0042] To illustrate the proposed technology, the sensing principle of the optical waveguide gas sensor is first calculated based on the Lambert-Beer law, as shown in formula (1):

[0043]

[0044] Where P and P0 represent the output waveguide and input waveguide optical powers, respectively, α gas is the absorption coefficient of the gas, α int is the intrinsic transmission loss factor of the optical waveguide, L is the waveguide length of the sensing area, and C is the concentration of the gas to be measured. This shows that by measuring the optical power of the output waveguide and the input waveguide, the intrinsic transmission loss factor α of the optical waveguide obtained according to the determined waveguide structure int , waveguide length L and external confinement factor Γ, and according to the absorption coefficient α of the corresponding gas gas The concentration C of the gas to be measured in the environment can be calculated. Taking the absorption of methane gas molecules with a concentration of 35000ppm at a wavelength of 1651nm as an example, when the gas pressure is 1atm, when α gas =1.512×10 -20 cm 2 / molecule, α int=5dB / cm, Γ=74%, and the waveguide lengths are 0.5cm, 1.0cm, 1.5cm, and 2.0cm respectively. The spectral response of this band is as follows Figure 2 shown.

[0045] Furthermore, the molecular concentration is expressed by formula (2), Avogadro constant NA = 6.02214076 × 10 23 :

[0046]

[0047] Furthermore, the gas absorption loss and intrinsic transmission loss can be expressed by formula (3) and formula (4) respectively. gas is the absorption coefficient per unit gas concentration and absorption path, so it needs to be multiplied by the actual gas concentration C and the waveguide length L. Compared with the light absorption in free space, only the light in the evanescent field of the waveguide is absorbed by the gas to be measured, so it needs to be multiplied by the power ratio occupied by the evanescent field in the transmission cross section, that is, the external confinement factor Γ in the upper cladding of the waveguide, in dB:

[0048]

[0049] Furthermore, by changing the power unit in formula (1) to dBm, we can obtain formula (5):

[0050]

[0051] Among them, P dB and They represent the output waveguide optical power and input waveguide optical power in dBm respectively.

[0052] Furthermore, when the concentration of the gas to be measured reaches the lower limit of detection LOD, that is, at the lowest detectable gas concentration level, the waveguide output power is reduced to the on-chip detector noise level, which can be expressed by formula (6):

[0053]

[0054] Among them, P noise represents the noise power of the on-chip detector.

[0055] Example 1

[0056] like Figure 3The implementation process of the specific embodiment 1 shown is as follows: first, the on-chip laser light source works and emits initial light, which is coupled into the transmission waveguide; then, the light carries energy along the transmission waveguide into the on-chip photonic circuit and propagates to the on-chip optical switch area; then, the on-chip optical switch selectively connects to one of the waveguides in the gas sensor waveguide array, so that the light enters the gas sensor waveguide array from the transmission waveguide through the on-chip optical switch; then, while the light propagates in the waveguide of the gas sensor waveguide array, it interacts with the gas in the environment through the evanescent field, causing the light energy in a specific band to be absorbed, and the degree of absorption is proportional to the gas concentration in the environment; next, the absorption spectrum signal carrying the gas information in the environment is received by the on-chip optical detector located at the light output end. At this point, the single-chip microcomputer will determine whether the on-chip optical switch controls the light to traverse each waveguide in the sensor waveguide array. If each waveguide has been traversed and the absorption spectrum information has been received, the spectrum information of all waveguides is sent to the microcontroller for processing; otherwise, the on-chip optical switch is adjusted to allow the light to enter other waveguides in the gas sensor waveguide array, and repeatedly propagate in the gas sensor waveguide array and be detected by the on-chip optical detector for absorption spectrum signals. Finally, the microcontroller completes the decoding of all output absorption spectrum information, removes abnormal data, fits the relationship between output optical power and waveguide length, and finally inverts and infers the gas concentration in the environment and completes the measurement.

[0057] Specific embodiment 1 is developed based on a suspended silicon-based waveguide, and its structural parameters are as follows: the insulator-silicon wafer has a 70nm thick top silicon layer and a 2μm thick oxide buried layer, the waveguide is a subwavelength strip waveguide, the core material is silicon, the waveguide width is 1μm, the subwavelength grating cladding width is 3μm, the waveguide is above the air cladding, and the oxide buried layer under the waveguide is removed with hydrofluoric acid to form a suspended structure, such as Figure 4 As shown. According to theoretical calculations, the above waveguide structure can support the propagation of TE0 mode of mid-infrared light with a wavelength of 1651nm. The simulation results show that the external confinement factor of the structure is Γ = 74%. In a specific embodiment, eight waveguides with waveguide lengths of 0.0675cm, 0.125cm, 0.25cm, 0.5cm, 1cm, 1.5cm, 2cm, and 2.5cm are used to form a gas sensing waveguide array. In addition, by selectively turning on the on-chip optical switch, the light energy will only enter the turned-on waveguide, avoiding the decrease of the input waveguide light energy caused by the simultaneous splitting of multiple waveguides, and further improving the detection performance of the gas sensor chip. When the on-chip laser light source provides 1 mW of light energy, and the input waveguide light power is 1 mW (using an on-chip optical switch), 0.25 mW (average split into 4 paths), 0.125 mW (average split into 8 paths), and 0.0675 mW (average split into 16 paths), the relationship between the gas concentration detection lower limit of the gas sensing waveguide array and the waveguide length can be calculated according to formula (6), as follows: Figure 5As shown in Figure 2, it is shown that the gas concentration detection limit of the gas sensing waveguide array using the on-chip optical switch scheme is lower. When the concentration C is 500ppm of methane molecules, the on-chip laser light source works and emits initial light in the 1651nm band, and the gas absorption cross section α gas =1.512×10 -20 cm 2 / molecule, the input waveguide optical power P0 is 1mW, and the intrinsic transmission loss factor α of the TE0 mode propagated in the subwavelength strip waveguide based on the suspended insulator-silicon wafer platform int It is estimated to be 5.0000dB / cm. According to formula (5), the output waveguide optical power P of 8 channels can be simulated and calculated, which can be plotted as follows: Figure 6 The output optical power is shown as a function of the waveguide length. The calculation results show that the output waveguide optical power P dB It shows a linear downward trend with the waveguide length L. A linear fit shows that the slope of the fitting line k = -5.0065 dB / cm. It is easy to know that the gas absorption loss per unit length is 0.0065 dB / cm. The gas concentration in the environment C = 500 ppm can be calculated from formula (7).

[0058]

[0059] Among them, the eight channels are sampled separately, and the concentration readings are inverted based on the slope fitting of the multiple measurement points sampled. Compared with the concentration readings calculated based on the single output optical power of a single channel, the sensitivity of the detection is further improved and the anti-interference ability is enhanced. Although the output optical power of the on-chip laser light source will decrease due to aging, dust or dirt as the working time increases, the optical waveguide has the advantage of stable intrinsic transmission loss and is not easy to be poisoned and aged. Therefore, Figure 6 For example, the function graph only has an intercept shift in the up and down directions without affecting the slope. Compared with the single-channel gas absorption sensing solution that is easily affected by laser aging, it avoids drift or accuracy problems caused by the decrease in laser output optical power. There is no need for downtime or manual intervention, which greatly extends the service life of the sensor chip and reduces maintenance costs. In addition, considering the possible unexpected failure of the gas sensor waveguide array, the on-chip integrated optical switch can isolate any faulty channel, reduce the impact of a single channel problem on the entire system, improve the stability of the system operation, and realize automatic and intelligent optical channel selection.

[0060] Example 2

[0061] The implementation process is the same as that in Example 1. This embodiment is based on the development of silicon nitride waveguides, and its structural parameters are as follows: the insulator-silicon nitride wafer has a 400nm thick top silicon nitride layer and a 4μm thick buried oxide layer, the waveguide is a strip waveguide, the core material is silicon nitride, the waveguide width is 1μm, and the waveguide is an air cladding layer, such as Figure 7 As shown. According to theoretical calculations, the above waveguide structure can support the propagation of TE0 mode of mid-infrared light with a wavelength of 1651nm. The simulation results show that the external confinement factor of the structure is Γ = 10%. In a specific embodiment, four waveguides with waveguide lengths of 0.5cm, 1cm, 1.5cm, and 2cm are used to form a gas sensing waveguide array. Moreover, by selectively turning on the on-chip optical switch, the light energy will only enter the turned-on waveguide. The on-chip laser light source works and emits initial light in the 1651nm band, and the gas absorption cross section α gas =1.512×10 -20 cm 2 / molecule, the input waveguide optical power P0 is 1mW, the intrinsic transmission loss factor α of the TE0 mode propagated in the strip waveguide based on the silicon nitride wafer platform int It is estimated to be 3.00000dB / cm. When the volume fraction of methane gas is 1000ppm, the output waveguide optical power P of the four channels can be simulated and calculated according to formula (5): dB , can be drawn as Figure 8 The output optical power is shown as a function of the waveguide length. The calculation results show that the output waveguide optical power P dB It shows a linear downward trend with the waveguide length L. A linear fit shows that the slope of the fitting line k = -3.00018 dB / cm. It is easy to know that the gas absorption loss per unit length is 0.00018 dB / cm. The gas concentration in the environment C = 1000 ppm can be calculated from formula (7).

[0062] Example 3

[0063] The implementation process is the same as that in Example 1. This embodiment is developed based on a silicon-insulator waveguide, and its structural parameters are as follows: the wafer has a 220nm thick top silicon layer and a 2μm thick buried oxide layer, the waveguide is a strip waveguide, the core material is silicon, the waveguide core width is 1μm, and there is an air cladding above the waveguide. According to theoretical calculations, the above waveguide structure can support the TM0 mode propagation of mid-infrared light with a wavelength of 1651nm. The simulation results show that the external confinement factor of the structure is Γ=60%. In a specific embodiment, four waveguides with waveguide lengths of 0.5cm, 1cm, 1.5cm, and 2cm are used to form a gas sensing waveguide array. Moreover, by selectively turning on the on-chip optical switch, light energy will only enter the turned-on waveguide. The on-chip laser light source works and emits initial light in the 1651nm band, and the gas absorption cross section αgas =1.512×10 -20 cm 2 / molecule, the input waveguide optical power P0 is 1mW, and the intrinsic transmission loss factor α of the TE0 mode propagated in the strip waveguide based on the silicon wafer platform int It is estimated to be 5.00000dB / cm. When a methane gas with a volume fraction of 1000ppm is introduced, the output waveguide optical power P of the four channels can be simulated and calculated according to formula (5): dB , can be drawn as Figure 7 The output optical power is shown as a function of the waveguide length. The calculation results show that the output waveguide optical power P dB It shows a linear downward trend with the waveguide length L. A linear fit shows that the slope of the fitting line k = -5.00106dB / cm. It is easy to know that the gas absorption loss per unit length is 0.00106dB / cm. The gas concentration C in the environment can be calculated by formula (3), which can be expressed as: The gas concentration C in the environment can be calculated by formula (7) = 1000ppm.

[0064] Finally, the method of the above embodiment is only a preferred implementation scheme and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A calibration-free gas sensor chip based on infrared absorption spectroscopy technology, characterized in that: The invention comprises an on-chip laser light source (1), a transmission waveguide (2), an on-chip optical switch (3), a gas sensor waveguide array (4) and an on-chip optical detector (5); the on-chip laser light source (1) is arranged at the light input end of the transmission waveguide (2); the on-chip optical switch (3) is arranged between the transmission waveguide (2) and the gas sensor waveguide array (4) and is used for selectively connecting the light in the transmission waveguide (2) to any waveguide in the gas sensor waveguide array (4); the gas sensor waveguide array (4) is composed of a plurality of waveguides with different structural parameters, and the light in the waveguide contacts with the ambient gas through the evanescent field; the on-chip optical detector (5) is arranged at the light output end of the gas sensor waveguide array (4) and is used for receiving the optical signal and converting it into an electrical signal, inverting and inferring the gas concentration through the electrical signal and regulating the switching condition of the on-chip optical switch (3).

2. The calibration-free gas sensor chip based on infrared absorption spectroscopy technology according to claim 1, characterized in that: The waveguide material in the calibration-free gas sensor chip is composed of one of silicon, germanium, a silicon-germanium mixture, silicon nitride, silicon carbide, indium phosphide, gallium arsenide, and lithium niobate.

3. The calibration-free gas sensor chip based on infrared absorption spectroscopy technology according to claim 1, characterized in that: The on-chip laser light source (1) is any one of a nonlinear laser, a monolithic integrated laser, a hybrid integrated laser, and a heterogeneous integrated laser.

4. The calibration-free gas sensor chip based on infrared absorption spectroscopy technology according to claim 1, characterized in that: The on-chip optical switch (3) is any one of a thermo-optical switch type, an electro-optical switch type, an acousto-optical switch type, a mechanical optical switch type, and a semiconductor optical amplifier optical switch type.

5. The calibration-free gas sensor chip based on infrared absorption spectroscopy technology according to claim 1, characterized in that: The gas sensing waveguide array (4) comprises two or more waveguides.

6. The calibration-free gas sensor chip based on infrared absorption spectroscopy technology according to claim 1, characterized in that: The difference between the waveguides with different structural parameters in the gas sensing waveguide array (4) is any one or more combinations of length difference, thickness difference, width difference, material difference, whether the buried oxide layer is retained, and whether the oxide cladding layer is retained.

7. The calibration-free gas sensor chip based on infrared absorption spectroscopy technology according to claim 1, characterized in that: The transmission waveguide (2) and the gas sensor waveguide array (4) can be used to propagate a light field in a transverse electric mode or a transverse magnetic mode.

8. A method for measuring gas concentration in an environment, based on the calibration-free gas sensor chip according to any one of claims 1 to 7, further comprising a single-chip microcomputer, characterized in that: include: The on-chip laser light source works and emits initial light, and the initial light is coupled into the transmission waveguide; The light carries energy and propagates along the transmission waveguide to the on-chip optical switch, and selectively accesses one of the waveguides in the gas sensing waveguide array through the on-chip optical switch, so that the light enters the gas sensing waveguide array from the transmission waveguide through the on-chip optical switch; When light propagates in the waveguide of the gas sensor waveguide array, it interacts with the gas in the environment through the evanescent field, causing the light energy in a certain wavelength band to be absorbed. The degree of absorption is proportional to the gas concentration in the environment. The absorption spectrum signal carrying the information of the gas in the environment is received by the on-chip photodetector at the light output end and transmitted to the single-chip microcomputer; the single-chip microcomputer will determine whether the on-chip optical switch controls the light to traverse each waveguide in the sensing waveguide array; If each waveguide has been traversed and the absorption spectrum information has been received, the spectrum information of all waveguides is sent to the single-chip microcomputer for processing; otherwise, the on-chip optical switch is adjusted to allow the light to enter other waveguides in the gas sensing waveguide array, and repeatedly propagate in the gas sensing waveguide array and be detected by the on-chip optical detector for the absorption spectrum signal; The single-chip computer decodes all the output absorption spectrum information, eliminates abnormal data, fits the relationship between the output optical power and the waveguide length, and finally inverts and calculates the gas concentration in the environment and completes the measurement.

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