A calibration-free gas sensing chip based on infrared absorption spectroscopy technology

Abstract

The present invention discloses a calibration-free gas sensing chip based on infrared absorption spectroscopy technology, which includes 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 optical 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 the light in the waveguides contacts the ambient gas through the evanescent field; the on-chip optical detector is arranged at the optical output end of the gas sensing waveguide array, and is used to receive the optical signal and convert it into an electrical signal, and inversely calculate the gas concentration through the electrical signal and control the switching state of the on-chip optical switch. This gas sensing chip has advantages in gas concentration measurement such as high precision and self-calibration, laying a foundation for the application of miniaturized gas sensors.

Description

Technical Field

[0001] The present invention relates to the field of integrated optoelectronics, and particularly to a calibration-free gas sensing 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, non-contact measurement, etc., and are widely used in the fields of industrial production, environmental monitoring, medical health, military security, etc. 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 sensing chip has the advantages of high integration, good portability, low power consumption, etc., overcoming the limitations of the relatively large volume and difficult integration of discrete sensing systems. However, most of them are based on single-channel light transmission, which is not conducive to achieving high-precision and self-calibrated sensing. Therefore, it is of great value to develop a calibration-free gas sensing chip based on infrared absorption spectroscopy technology.

[0003] In terms of papers, in 2012, Qi Wang et al. from Northeastern University developed a small and 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 with a limited chip size. In 2017, L. Tombez et al. from IBM in the United States proposed a gas sensing chip based on a 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 et al. from the Arctic University of Norway developed an on-chip gas sensor for detecting C2H2 using Ta2O5 as the core layer material of the sensing chip (Light: Science & Applications 10, 26, 2021), achieving gas concentration detection with a lower detection limit of 7 ppm. In 2023, Xueying Wang et al. from Jilin University studied a suspended photonic crystal waveguide sensor and a suspended ridge waveguide sensor based on the 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 works all use a single-channel on-chip optical path to achieve gas sensing, lacking anti-interference ability and being not conducive to improving detection sensitivity and signal-to-noise ratio.

[0004] In terms of patents, in 2015, Sun Xuhui et al. from Jiangsu Zhiwen Intelligent Sensing Technology Co., Ltd. designed a preparation method for a multi-channel array gas sensor, which can flexibly drop different sensitive materials on the same substrate or different substrates, and applied for a Chinese invention patent (201510329597.9). In 2020, Li Na et al. from China National Petroleum Corporation invented a multi-parameter gas sensing microchip and its preparation method, which can realize the function of detecting complex atmospheres, has the advantages of reducing volume, power consumption and improving integration, and applied for a Chinese invention patent (202010281584.X). In 2023, Zheng Shaonan et al. from Shanghai University invented and disclosed a micro infrared gas sensing device based on a hollow waveguide chip, which realized 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 et al. from Xinlianxin (Xiongan, Hebei) Technology Co., Ltd. invented and disclosed an integrated gas sensing chip, which solved the problems of complex manufacturing process, high cost and large volume of gas sensing chips, and applied for a Chinese invention patent (202311044176.2)

[0005] In summary, the sensing chip has the advantages of miniaturization, low power consumption and easy integration compared with the discrete sensing system, but its detection accuracy is poor and the detection lower limit is high. The optical gas sensor using the infrared absorption spectroscopy technology can improve the sensitivity, selectivity and response speed. However, its measured spectrum is affected by the change of the input light intensity, lacks the anti-aging ability and cannot achieve self-calibration. Therefore, it is of great significance to develop a gas sensing chip that can simultaneously achieve high precision and self-calibration for realizing a high-performance chip-level sensing system. Summary of the Invention

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

[0007] The purpose of the present invention is achieved by the following technical solutions:

[0008] A calibration-free gas sensing chip based on infrared absorption spectroscopy technology, which consists of 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 optical input end of the transmission waveguide; the on-chip optical switch is arranged between the transmission waveguide and the gas sensing waveguide array, and is used to select and connect the light in the transmission waveguide to any waveguide in the gas sensing waveguide array; the gas sensing waveguide array is composed of several waveguides with different structural parameters, and the light in the waveguide contacts the ambient gas through the evanescent field; the on-chip optical detector is arranged at the optical output end of the gas sensing waveguide array, and is used to receive the optical signal and convert it into an electrical signal, and inversely calculate the gas concentration through the electrical signal and control the switching state of the on-chip optical switch.

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

[0010] Further, 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] Further, 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] Further, the gas sensing waveguide array includes two or more waveguides.

[0013] Further, the differences between the waveguides with different structural parameters in the gas sensing waveguide array are any one or a combination of length difference, thickness difference, width difference, material difference, whether to retain the buried oxide layer, and whether to retain the oxide cladding.

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

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

[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] While light propagates in the waveguides of the gas sensing waveguide array, it interacts with the gas in the environment through the evanescent field, resulting in the absorption of light energy in a certain wavelength band. The degree of absorption is proportional to the gas concentration in the environment.

[0019] The absorption spectrum signal carrying the gas information in the environment is received by the on-chip optical detector at the light output end and transmitted to the single-chip microcomputer. The single-chip microcomputer determines 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 make the light enter other waveguides in the gas sensing waveguide array, and the process of propagating in the gas sensing waveguide array and being detected by the on-chip optical detector for the absorption spectrum signal is repeated.

[0021] The single-chip microcomputer completes the decoding of all output absorption spectrum information, eliminates abnormal data, fits the relationship between the output optical power and the waveguide length, and finally inversely calculates the gas concentration in the environment to complete the measurement.

[0022] Compared with the prior art, the beneficial effects brought by the technical solution of the present invention are as follows:

[0023] 1. The calibration-free gas sensing chip based on the 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 adopted to improve the accuracy, specificity and response speed of gas detection; on the other hand, based on the calibration-free gas sensing waveguide array, the truncation method measurement of the output light energy is realized, and the gas concentration reading is obtained by fitting the slope at the measurement point, further improving the detection sensitivity and enhancing the anti-interference ability.

[0024] 2. The calibration-free gas sensing chip based on the infrared absorption spectroscopy technology involved in the present invention does not require calibration, improving 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 problems caused by the fluctuation of the input light intensity, the aging of the laser or the decrease of the output optical power of the laser are avoided. There is no need for shutdown or manual intervention, greatly prolonging the service life of the sensing chip, reducing the maintenance cost, and improving the applicability in various complex environments.

[0025] 3. The calibration-free gas sensing chip based on the infrared absorption spectroscopy technology involved in the present invention can realize the automatic and intelligent selection and management of optical channels. By using the on-chip integrated optical switch, any faulty channel can be isolated, reducing the impact of a single-channel problem on the entire system and significantly improving the stability of the system operation.

[0026] 4. The calibration-free gas sensing chip based on the infrared absorption spectroscopy technology involved in the present invention can achieve targeted optical channel selection and connection. The on-chip integrated optical switch accurately selects and connects the optical paths one by one, avoiding the decrease of the input waveguide optical power and energy loss caused by the simultaneous splitting of multiple waveguides, and improving the detection performance of the gas sensing chip.

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

[0028] In summary, the present invention has achieved an overall improvement in the accuracy, sensitivity, stability, and applicability of the optical gas sensing chip, and is of great significance for the sensing requirements in the fields of industry, environment, medical treatment, etc. Description of the Drawings

[0029] Figure 1 It is a schematic structural diagram of a calibration-free gas sensing chip based on the infrared absorption spectroscopy technology;

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

[0031] Figure 3 It is a functional principle flow chart of Specific Embodiment 1 of the present invention;

[0032] Figure 4 It is a schematic structural diagram of the gas sensing waveguide cross-section of Specific Embodiment 1 of the present invention;

[0033] Figure 5 It is a relationship diagram of the lower limit of the gas concentration detection of the gas sensing waveguide array and the waveguide length in Specific Embodiment 1 of the present invention when the input waveguide optical power is 1 mW, 0.25 mW, 0.125 mW, and 0.0675 mW;

[0034] Figure 6 It is a simulation result of the output optical power varying with the waveguide length in Specific Embodiment 1 of the present invention when the input waveguide optical power is 1 mW and the methane gas concentration is 500 ppm;

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

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

[0037] Figure 9 Schematic diagram of the cross-section of the gas sensing waveguide in Specific Embodiment 3 of the present invention;

[0038] Figure 10 Simulation result of the output optical power varying with the waveguide length in Specific Embodiment 3 of the present invention, with the input waveguide optical power being 1 mW and the methane gas concentration being 1000 ppm;

[0039] Reference numerals: 1, on-chip laser light source; 2, transmission waveguide; 3, on-chip optical switch; 4, gas sensing waveguide array; 5, on-chip optical detector. Specific embodiments

[0040] The present invention will be further described in detail below with reference to 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] As shown in Figure 1 is a calibration-free gas sensing chip based on infrared absorption spectroscopy technology protected by the present invention, wherein the on-chip laser light source 1 is arranged at the optical input end of the transmission waveguide 2; the on-chip optical switch 3 is integrated between the transmission waveguide 2 and the gas sensing waveguide array 4; the gas sensing waveguide array 4 is composed of waveguide clusters with different structural parameters and is in contact with the external gas; the on-chip optical detector 5 is arranged at the optical output end of the gas sensing waveguide array.

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

[0043]

[0044] Wherein, P and P 0 respectively represent the optical powers of the output waveguide and the input waveguide, 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 region, and C is the concentration of the gas to be measured. This indicates that by measuring the optical powers of the output waveguide and the input waveguide, based on the intrinsic transmission loss factor α int of the optical waveguide obtained from the determined waveguide structure, the waveguide length L, and the external confinement factor Γ, and at the same time according to the absorption coefficient α gas of the corresponding 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 35000 ppm at a wavelength of 1651 nm as an example, when the atmospheric pressure is 1 atm, when α gas = 1.512×10 -20 cm 2 / molecule, α int= 5 dB / cm, Γ = 74%, when the waveguide lengths are 0.5 cm, 1.0 cm, 1.5 cm, and 2.0 cm respectively, the spectral response in this band is as Figure 2 shown.

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

[0046]

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

[0048]

[0049] Furthermore, by converting the power unit in formula (1) to dBm, formula (5) can be obtained:

[0050]

[0051] where P dB and represent the output waveguide optical power and the input waveguide optical power in units of dBm respectively.

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

[0053]

[0054] where P noise represents the noise power of the on-chip detector.

[0055] Example 1

[0056] As Figure 3The implementation process of Specific Embodiment 1 shown is as follows. First, the on-chip laser light source operates and emits initial light, and the initial light is coupled into the transmission waveguide. Next, the light carrying energy enters the on-chip photonic circuit along the transmission waveguide and propagates to the on-chip optical switch area. Then, the on-chip optical switch selectively accesses one of the waveguides in the gas sensing waveguide array, enabling the light to enter the gas sensing waveguide array from the transmission waveguide through the on-chip optical switch. After that, while the light propagates in the waveguides of the gas sensing waveguide array, it interacts with the gas in the environment through the evanescent field, resulting in the absorption of light energy in a specific wavelength band, 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 photodetector located at the light output end. At this time, 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 will be sent to the single-chip microcomputer for processing; otherwise, the on-chip optical switch is adjusted to make the light enter other waveguides in the gas sensing waveguide array, and the process of propagating in the gas sensing waveguide array and being detected by the on-chip photodetector for the absorption spectrum signal is repeated. Finally, the single-chip microcomputer completes the decoding of all output absorption spectrum information, eliminates abnormal data, fits the relationship between the output optical power and the waveguide length, and finally inversely calculates 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 70-nm-thick top silicon layer and a 2-μm-thick buried oxide layer. The waveguide is a subwavelength strip waveguide, the core layer material is silicon, the waveguide width is 1 μm, the subwavelength grating cladding width is 3 μm, the air cladding is above the waveguide, and the buried oxide layer below the waveguide is removed with hydrofluoric acid to form a suspended structure, as Figure 4 shown. According to theoretical calculations, the above waveguide structure can support the propagation of the TE 0 mode of mid-infrared light with a wavelength of 1651 nm. The simulation results show that the external confinement factor Γ of this structure is 74%. In a specific embodiment, a gas sensing waveguide array is composed of eight waveguides with waveguide lengths of 0.0675 cm, 0.125 cm, 0.25 cm, 0.5 cm, 1 cm, 1.5 cm, 2 cm, and 2.5 cm respectively. And, through the selective connection of the on-chip optical switch, the light energy will only enter the connected waveguide, avoiding the decrease in the input waveguide light energy caused by the simultaneous splitting of multiple waveguides, and further improving the detection performance of the gas sensing chip. When the on-chip laser light source provides a light energy of 1 mW, the input waveguide optical power is 1 mW (using the on-chip optical switch), 0.25 mW (evenly split into 4 paths), 0.125 mW (evenly split into 8 paths), and 0.0675 mW (evenly split into 16 paths). According to formula (6), the relationship between the lower limit of gas concentration detection of the gas sensing waveguide array and the waveguide length can be calculated, as Figure 5As shown, it indicates that the lower limit of gas concentration detection of the gas sensing waveguide array adopting the on-chip optical switch scheme is lower. When the concentration C is 500 ppm of methane molecules, the on-chip laser light source operates and emits the initial light in the 1651 nm band, and the gas absorption cross-section α gas = 1.512×10 -20 cm 2 / molecule, the input waveguide optical power P 0 is 1 mW, and the intrinsic transmission loss factor α 0 of the sub-wavelength strip waveguide propagating the TE int mode based on the suspended insulator-silicon wafer platform is estimated to be 5.0000 dB / cm. According to formula (5), the output waveguide optical power P of 8 channels can be simulated and calculated, and a function image of the output optical power varying with the waveguide length as shown in Figure 6 can be drawn. The calculation results show that the output waveguide optical power P dB shows a linear decreasing trend with the waveguide length L. By performing a linear fit on it, it can be known that the slope k of the fit line is -5.0065 dB / cm. It is easy to know that the gas absorption loss per unit length is 0.0065 dB / cm. From formula (7), the gas concentration C = 500 ppm in the environment can be calculated.

[0058]

[0059] Among them, the 8 channels are sampled respectively, and the concentration readings are inversely deduced by fitting the slope according to multiple measured points of the sampling. By comparing with the method of deducing the concentration readings only based on the single output optical power of a single channel, the detection sensitivity 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 factors such as aging, dust or dirt with the increase of the working time, the optical waveguide has the advantages of stable intrinsic transmission loss and being not easily poisoned and aged. Therefore, taking Figure 6 as an example, the function image only has an intercept offset in the up and down direction without affecting the slope. By comparing with the single-channel gas absorption sensing scheme that is easily affected by the aging of the laser, the drift or accuracy problem caused by the decrease of the output optical power of the laser is avoided. There is no need for shutdown or manual intervention, which greatly prolongs the service life of the sensing chip and reduces the maintenance cost. In addition, considering the possible accidental failure problem of the gas sensing waveguide array, through the on-chip integrated optical switch, any faulty channel can be isolated, reducing the impact of a single-channel problem on the entire system, improving the stability of the system operation, and realizing automatic and intelligent optical channel selection and connection.

[0060] Embodiment 2

[0061] The implementation process is the same as that in Embodiment 1. This embodiment is developed based on a silicon nitride waveguide, and its structural parameters are as follows: The insulator-silicon nitride wafer has a 400-nm-thick top silicon nitride layer and a 4-μm-thick buried oxide layer. The waveguide is a strip waveguide, the core layer material is silicon nitride, the waveguide width is 1 μm, and the air cladding is above the waveguide, as Figure 7 shown. According to theoretical calculations, the above waveguide structure can support the propagation of TE 0 mode of mid-infrared light with a wavelength of 1651 nm. The simulation results show that the external confinement factor Γ of this structure is 10%. In a specific embodiment, a gas sensing waveguide array is composed of four waveguides with waveguide lengths of 0.5 cm, 1 cm, 1.5 cm, and 2 cm respectively. And, through the on-chip optical switch selectively turned on, the optical energy will only enter the turned-on waveguide. The on-chip laser light source works and emits the initial light in the 1651-nm band. The gas absorption cross-section α gas = 1.512×10 -20 cm 2 / molecule, the input waveguide optical power P 0 is 1 mW. The intrinsic transmission loss factor α 0 of the strip waveguide based on the silicon nitride wafer platform propagating the TE int mode is estimated to be 3.00000 dB / cm. When methane gas with a volume fraction of 1000 ppm is introduced, according to formula (5), the output waveguide optical powers P dB of the 4 channels can be simulated and calculated, and a function image of the output optical power varying with the waveguide length as shown in Figure 8 can be drawn. The calculation results show that the output waveguide optical power P dB shows a linear decreasing trend with the waveguide length L. By performing a linear fit on it, it can be known that the slope k of the fitting straight line is -3.00018 dB / cm. It is easy to know that the gas absorption loss per unit length is 0.00018 dB / cm. From formula (7), the gas concentration C in the environment can be calculated to be 1000 ppm.

[0062] Embodiment 3

[0063] The implementation process is the same as that in Embodiment 1. This embodiment is developed based on a silicon-on-insulator waveguide, and its structural parameters are as follows: The wafer has a 220-nm-thick top silicon layer and a 2-μm-thick buried oxide layer. The waveguide is a strip waveguide, the core layer material is silicon, the core width of the waveguide is 1 μm, and the air cladding is above the waveguide. According to theoretical calculations, the above waveguide structure can support the TM 0Mode propagation, and the simulation results show that the external confinement factor Γ of this structure is 60%. In a specific embodiment, a gas sensing waveguide array is composed of four waveguides with waveguide lengths of 0.5 cm, 1 cm, 1.5 cm, and 2 cm respectively. And, through the selective connection of the on-chip optical switch, the optical energy will only enter the connected waveguide. The on-chip laser source operates and emits the initial light in the 1651 nm band, and the gas absorption cross-section α gas = 1.512×10 -20 cm 2 / molecule, the input waveguide optical power P 0 is 1 mW, and the intrinsic transmission loss factor α 0 of the strip waveguide propagating the TE int mode based on the silicon wafer platform is estimated to be 5.00000 dB / cm. When methane gas with a volume fraction of 1000 ppm is introduced, according to formula (5), the output waveguide optical power P dB of the 4 channels can be simulated and calculated, and a function image of the output optical power varying with the waveguide length as shown in Figure 7 can be drawn. The calculation results show that the output waveguide optical power P dB shows a linear decreasing trend with the waveguide length L. By performing a linear fit on it, it can be known that the slope k of the fitting line is -5.00106 dB / cm. It is easy to know that the gas absorption loss per unit length is 0.00106 dB / cm. From formula (3), the gas concentration C in the environment can be calculated, and it can be expressed as the gas concentration C = 1000 ppm can be calculated from formula (7).

[0064] Finally, the method of the above embodiment is only a preferred implementation, and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within 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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