On-chip gas sensor and on-chip gas sensor assembly

Abstract

According to the on-chip gas sensor and the on-chip gas sensor assembly, the refractive index of an upper waveguide material layer of a ridge waveguide layer of the sensor is larger than that of a lower waveguide material layer, and pump light in a TM mode and probe light in a TE mode can be supported at the same time. Namely, high absorption of the to-be-detected gas to the pump light and weak influence of the to-be-detected gas to the detection light are considered at the same time, and the detection precision of the gas is improved. Moreover, a simpler waveguide structure is adopted, the waveguide preparation process is simple, and the loss of the waveguide is relatively low. Compared with a photo-thermal interference method in optical fiber sensing, the device has the advantages that the interaction between the pump light and the gas to be detected is greatly improved, the length of the detection waveguide is greatly shortened while high sensitivity is guaranteed, and the size of the device can be reduced to the micron dimension. In addition, the waveguide structure of the on-chip gas sensor disclosed by the invention is prepared from chalcogenide glass, so that the on-chip gas sensor has more obvious advantages when being correspondingly applied to gas detection of a middle-infrared band.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated photon biosensor devices, and in particular to an on-chip gas sensor and an on-chip gas sensor assembly. Background Art

[0002] High-precision gas detection plays a very important role in environmental quality testing, industrial production, disease diagnosis and other fields. It is an important technology related to national people's livelihood, economic development, and national defense security.

[0003] With the advent of the 5G era, the miniaturization, intelligence and chipization of sensors have gradually become a new generation of innovative technologies that all countries must compete for. Among them, on-chip gas sensors have attracted widespread attention due to their low power consumption, low cost, compact structure, and easy integration with other devices.

[0004] At present, there are two main types of on-chip gas sensors. One is the direct absorption spectral sensor (DAS), whose working mechanism is to use the evanescent field in the waveguide to interact with the gas to be measured, thereby achieving the absorption of light of a specific frequency. However, due to the weak absorption of light by molecules, it is difficult to apply to low-concentration environments. The other is a photothermal spectrometer (PTS) based on the laser photothermal effect, which uses a pump-probe method to generate thermal disturbances through the absorption of pump light by the gas to be measured, thereby changing the effective refractive index during waveguide transmission, and then changing the phase of the detection light to achieve high-precision detection of the gas. The two sensing technologies have different principles, but the core key lies in how to improve the interaction between light and the gas to be measured.

[0005] The current mainstream solution is to use a series of methods to enhance the evanescent field of the waveguide to achieve improvements in direct absorption spectral sensors. Specifically, the slit waveguide solution is used to concentrate the light field at the slit, which can greatly improve the interaction between light and matter. However, the slits and sub-wavelength gratings prepared on the chip will significantly increase the loss of the waveguide while having a field enhancement effect. Sensors designed using these structures cannot effectively improve the sensing sensitivity.

[0006] Therefore, there is an urgent need for an optical waveguide structure with simple structure, low optical loss, easy preparation and high confinement factor (CF) in air to achieve high-precision detection of low-concentration gases. Summary of the invention

[0007] Based on this, it is necessary to provide an on-chip gas sensor and an on-chip gas sensor assembly to address the above problems, so as to optimize the waveguide structure and greatly improve the distribution of the light field in the air envelope without increasing the difficulty of the waveguide preparation process, thereby achieving easy preparation and high-precision detection of low-concentration gases.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] An on-chip gas sensor comprising:

[0010] Silicon substrate;

[0011] A silicon oxide cladding layer, wherein the silicon oxide cladding layer is arranged on surfaces of both ends of the silicon substrate, and a lower air cladding layer is arranged in the middle of the silicon oxide cladding layer;

[0012] A ridge waveguide layer, wherein the ridge waveguide layer is disposed on the surface of the silicon oxide cladding layer and the lower air cladding layer, and the refractive index of the upper waveguide material layer of the ridge waveguide layer is greater than the refractive index of the lower waveguide material layer;

[0013] An upper air cladding layer, wherein the upper air cladding layer is arranged on the surface of the ridge waveguide layer;

[0014] The pump light of the on-chip gas sensor is in TM mode, and the detection light is in TE mode.

[0015] In another embodiment, the upper waveguide material layer and the lower waveguide material layer are made of chalcogenide glass.

[0016] In another embodiment, the upper waveguide material layer is made of GeSbSe.

[0017] In another embodiment, the lower waveguide material layer is made of GeSbS.

[0018] In another embodiment, the thickness of the lower waveguide material layer is 1 / 4-1 / 2 of the thickness of the ridge waveguide layer.

[0019] In another embodiment, the thickness of the ridge waveguide layer is 100 nanometers to 300 nanometers.

[0020] In another embodiment, the wavelength of the pump light is the wavelength at the absorption peak of the gas to be measured, and the wavelength of the detection light is the wavelength at the non-absorption peak of the gas to be measured.

[0021] In another embodiment, the wavelength and intensity of the pump light are modulated by a periodic function.

[0022] In another embodiment, the periodic function is a trigonometric function, a periodic rectangular pulse function or a periodic triangular function.

[0023] Yet another embodiment discloses an on-chip gas sensor assembly, which includes the on-chip gas sensor disclosed in any of the above embodiments.

[0024] The on-chip gas sensor disclosed in the present invention has a ridge waveguide layer whose upper waveguide material layer has a refractive index greater than that of the lower waveguide material layer, and can simultaneously support TM mode pump light and TE mode detection light. That is, the high absorption of the measured gas on the pump light and the weak influence on the detection light are taken into account at the same time, thereby improving the detection accuracy of the gas. Moreover, a simpler waveguide structure is adopted, the waveguide preparation process is simple, and the loss of the waveguide is relatively low. Compared with the photothermal interferometry method in optical fiber sensing, it not only greatly improves the interaction between the pump light and the measured gas, but also greatly shortens the length of the detection waveguide while ensuring high sensitivity, and the device size can be reduced to the micron level.

[0025] In addition, compared with the on-chip optical waveguide structure made of traditional optical fiber or silicon material, the waveguide structure of the on-chip gas sensor disclosed in the present invention is made of chalcogenide glass, which has more obvious advantages for gas detection in the mid-infrared band. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the structure of an on-chip gas sensor provided by an embodiment of the present invention;

[0027] Figure 2 A graph showing the relationship between the confinement factor and the waveguide structure provided in one embodiment of the present invention;

[0028] Figure 3 A TM mode field distribution diagram provided by an embodiment of the present invention;

[0029] Figure 4 A graph showing the temperature variation over time under TM mode pump light (1kHz) provided in one embodiment of the present invention;

[0030] Figure 5 A graph showing the temperature variation over time under TM mode pump light (100kHz) provided in one embodiment of the present invention;

[0031] Figure 6 A graph showing the variation of the TE detection light phase difference with the pump light frequency provided in one embodiment of the present invention;

[0032] Figure 7 A temperature distribution diagram of the pump light at the initial action provided by an embodiment of the present invention;

[0033] Figure 8 A temperature distribution diagram of the pump light at 0.05ms provided in one embodiment of the present invention;

[0034] Fig. 9 A TE mode field distribution diagram provided by another embodiment of the present invention;

[0035] Fig.10A graph showing the change of temperature over time under TE mode pump light (1kHz) provided in another embodiment of the present invention;

[0036] Fig.11 A graph showing the temperature variation over time under TE mode pump light (100kHz) provided in another embodiment of the present invention;

[0037] Fig.12 A graph showing a change in the phase difference of the TE mode detection light as a function of the pump light frequency provided by another embodiment of the present invention;

[0038] Fig.13 A schematic diagram of the structure of an on-chip sensor component provided in yet another embodiment of the present invention.

[0039] In the figure, 1, silicon substrate; 2, silicon oxide cladding; 3, lower air cladding; 41, upper waveguide material layer; 42, lower waveguide material layer; 5, upper air cladding; 11, pump light emitter; 12, first polarization controller; 13, detection light emitter; 14, second polarization controller; 15, beam splitter; 16, first beam combiner; 17, on-chip gas sensor; 18, second beam combiner; 19, acousto-optic modulator; 20, detector. DETAILED DESCRIPTION

[0040] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific implementation methods or embodiments, and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, and the combinations include any two related listed items, any more related listed items, or all related listed items.

[0042] like Figure 1 As shown, one embodiment of the present invention discloses an on-chip gas sensor, comprising:

[0043] Silicon substrate 1;

[0044] A silicon oxide cladding layer 2, wherein the silicon oxide cladding layer 2 is arranged on surfaces of both ends of the silicon substrate 1, and a lower air cladding layer 3 is arranged in the middle of the silicon oxide cladding layer 2;

[0045] A ridge waveguide layer, wherein the ridge waveguide layer is arranged on the surface of the silicon oxide cladding layer 2 and the lower air cladding layer 3, the ridge waveguide layer is composed of an upper waveguide material layer 41 and a lower waveguide material layer 42, and the refractive index of the upper waveguide material layer 41 of the ridge waveguide layer is greater than the refractive index of the lower waveguide material layer 42;

[0046] An upper air cladding layer 5, wherein the upper air cladding layer 5 is arranged on the surface of the ridge waveguide layer;

[0047] The pump light of the on-chip gas sensor is in TM mode, and the detection light is in TE mode.

[0048] The on-chip gas sensor disclosed in this embodiment has a refractive index of the upper waveguide material layer of the ridge waveguide layer that is greater than the refractive index of the lower waveguide material layer, and can simultaneously support TM mode pump light and TE mode detection light. That is, the high absorption of the measured gas on the pump light and the weak influence on the detection light are taken into account at the same time, thereby improving the detection accuracy of the gas. Moreover, a simpler waveguide structure is adopted, the waveguide preparation process is simple, and the loss of the waveguide is relatively low. Compared with the photothermal interferometry method in optical fiber sensing, it not only greatly improves the interaction between the pump light and the measured gas, but also greatly shortens the length of the detection waveguide while ensuring high sensitivity, and the device size can be reduced to the micron level.

[0049] In another embodiment, the ridge waveguide layer should have low optical loss at both the pump light wavelength and the detection light wavelength, so its material includes but is not limited to silicon nitride, chalcogenide glass, lithium niobium oxide, hafnium oxide, and polymer.

[0050] In another embodiment, when selecting a waveguide material, the following conditions need to be met: (1) the waveguide material should be transparent in the sensing wavelength range to reduce the absorption loss of the material; (2) the refractive index difference between the core layer and the cladding layer should be as large as possible. Reducing the refractive index of the cladding material can reduce the light distributed in the cladding and the substrate. When the refractive index difference between the core layer and the cladding layer is large, reducing the size of the core layer can allow more light to be distributed in the analyte cladding to obtain a large ECF and meet the guided mode condition; (3) the preparation process of the core material needs to be compatible with the properties of the cladding material. For example, it is difficult to prepare crystalline silicon (Si) or bond it to other materials except silicon dioxide (SiO2).

[0051] Commonly used waveguide materials include silicon, silicon dioxide, silicon nitride, silicon fluoride, etc. At the same optical path, mid-infrared gas sensors have better performance. Silicon-On-Insulator (SOI) waveguides are not suitable for mid-infrared sensing because SiO2 has greater absorption loss in the mid-infrared band. Silicon-On-Nitride (SON) waveguides and Silicon On-Sapphire (SOS) waveguides have very small absorption losses. In addition to Si, germanium (Ge) and chalcogenide glass (ChG) have a large refractive index in the mid-infrared band and are suitable as waveguide core layers. ChG mainly includes chalcogen elements sulfur (S), selenium (Se) and tellurium (Te), as well as arsenic (As), gallium (Ga), antimony (Sb) and Ge. Since the conversion temperature of ChG is low (150-500°C), in addition to the etching method, ChG waveguides can also be prepared using the stripping method without destroying the structure of the photoresist mask. Different optical properties can be obtained by changing the ChG composition, among which the transparent wavelength of telluride glass can reach 20μm. According to the conditions of the waveguide mode, materials with a refractive index lower than ChG can be used as the lower cladding material of the ChG waveguide. Although SiO2 is not suitable for application in the mid-infrared band, its low refractive index makes it suitable as the lower cladding material of the near-infrared waveguide. The ChG (ChG-On-Oxide, COO) waveguide on SiO2 and SOI waveguide are more suitable for near-infrared gas sensing.

[0052] In this embodiment, the on-chip gas sensor is realized based on ChG on SiO2. Specifically, the upper waveguide material layer and the lower waveguide material layer are made of chalcogenide glass. More specifically, the upper waveguide material layer is made of GeSbSe, and the lower waveguide material layer is made of GeSbS.

[0053] Compared with the on-chip optical waveguide structure made of traditional optical fiber or silicon material, the waveguide structure of the on-chip gas sensor disclosed in this embodiment is made of chalcogenide glass, which has more obvious advantages for gas detection in the mid-infrared band.

[0054] In another embodiment, in order to achieve TM mode transmission, the thickness of the lower waveguide material layer of the ridge waveguide layer should be thin enough, but not too thin to support the cantilever beam structure. Therefore, considering the above conditions comprehensively, the minimum thickness of the lower waveguide material layer should not be less than 1 / 4 of the thickness of the ridge waveguide layer, and the maximum thickness should not exceed 1 / 2 of the thickness of the ridge waveguide layer, that is, the thickness of the lower waveguide material layer is 1 / 4-1 / 2 of the thickness of the ridge waveguide layer. Figure 2As shown, the thickness of the lower waveguide material layer is 1 / 4 of the thickness of the ridge waveguide layer. However, the thickness of the upper and lower waveguide material layers in the ridge waveguide layer must also be adapted to the wavelengths of the pump light and the probe light, so they can be adjusted according to the wavelengths of the pump light and the probe light in actual design.

[0055] In another embodiment, since the on-chip gas sensor disclosed in the present invention adopts a simpler waveguide structure and the waveguide preparation process is simple, the device size can be reduced to the micron level. In this embodiment, the thickness of the silicon oxide cladding is only a few microns, while the thickness of the ridge waveguide layer is 100 nanometers to 300 nanometers. Specifically, the thickness of the silicon oxide cladding can be 5 microns, or 2 microns, 3 microns or 7 microns, etc. The thickness of the ridge waveguide layer can be 100 nanometers, 150 nanometers, 200 nanometers, 250 nanometers and 300 nanometers, etc. In this embodiment, the thickness of the ridge waveguide layer is selected to be 260 nanometers. At this time, the thickness of the lower waveguide material layer is 65 nanometers, and the thickness of the upper waveguide material layer is 195 nanometers.

[0056] It can be seen that the size of the on-chip gas sensor disclosed in this embodiment can be reduced to the micron level. As its size is reduced, it can be used in a wider range of applications and is easier to integrate with other devices.

[0057] In another embodiment, the pump light of the on-chip gas sensor is in TM mode, and the detection light is in TE mode, that is, the waveguide in this embodiment is designed to support both TE and TM modes.

[0058] Among them, the limitation factor, as an important parameter in the waveguide transmission system, plays a vital role in the design and performance analysis of the waveguide. In practical applications, the size and distribution of the limitation factor will directly affect the transmission efficiency and performance stability of the waveguide system.

[0059] In this embodiment, the confinement factor distribution of the pump light in the upper and lower air envelopes in the TM mode is as follows: Figure 2 shown. Figure 2 In the embodiment, the thickness of the ridge waveguide layer is 200 nm-300 nm, and the width is 800 nm-100 nm. Further, the confinement factor Γ of light in air is calculated by formula (1):

[0060]

[0061] From the simplified expression of the confinement factor, it can be seen that the confinement factor in air can be defined as the product of the waveguide group refractive index and the electric field energy density in air.

[0062] Figure 3The electric field distribution of the TM mode optical pump light under this structural size is shown. It can be seen that the light of this mode accounts for a large proportion in the air, and most of it propagates in the air, with only a small part of the light confined in the optical waveguide. The effective refractive index of this mode is ~1.15, which is very close to the refractive index of the air cladding (~1).

[0063] This embodiment can further improve the limitation factor by optimizing the width of the waveguide, the total height of the waveguide, and the thickness of the slab waveguide region. More preferably, the width of the waveguide is 865 nanometers, the total height of the waveguide is 260 nanometers, and the thickness of the slab waveguide region is 65 nanometers. At this time, the limitation factor of the on-chip gas sensor disclosed in this embodiment is as high as 124%, which greatly improves the interaction between the pump light and the detected gas.

[0064] In one embodiment, the wavelength and intensity of the pump light are modulated by a periodic function, and the periodic function is a trigonometric function, a periodic rectangular pulse function, or a periodic triangular function.

[0065] After the pump light is periodically modulated, its wavelength or intensity will have a periodic change. Taking intensity modulation as an example, when the light intensity changes with time as a sine function, the temperature of the optical waveguide caused by the pump light also changes periodically. This periodic temperature change will cause the refractive index of the waveguide to change periodically, and then cause the waveguide phase to be periodically modulated. This method can eliminate the influence of background light intensity changes on the test results.

[0066] In another embodiment, the above-mentioned on-chip gas sensor is used to detect 1% concentration C2H2 gas. The pump light of the on-chip gas sensor described in this embodiment is periodically modulated by a sine function, and the modulation frequencies are 1kHz and 100kHz respectively. During detection, the substance to be tested (C2H2) will flow in the air envelope. When the pump light irradiates the substance to be tested (C2H2), the substance to be tested (C2H2) will absorb part of the energy of the pump light to generate heat, thereby increasing the temperature of the ridge waveguide. Among them, the temperature change over time under the TM mode pump light is as follows: Figure 4 (1kHz) and Figure 5 (100kHz). It can be seen that under the action of periodic pump light, the time and temperature difference when the waveguide reaches the quasi-steady state are related to the frequency of the pump light. If the frequency of the pump light is too high, the system cannot conduct away the heat in time within one cycle, resulting in a longer time to reach the quasi-steady state and a smaller temperature difference. The temperature difference in the waveguide at a frequency of 1kHz can reach 43.9mK, while when the frequency is 100kHz, the temperature difference in the waveguide is only 9.6mK.

[0067] Figure 6is a graph showing the relationship between the waveguide phase shift and the pump light frequency. Since the refractive index of the waveguide is related to temperature (the thermo-optic coefficient of the waveguide material in the embodiment of the present invention is 13.7×10 -6 ), so the change of pump light frequency will cause the change of waveguide refractive index. When the probe light is coupled into the waveguide in TE mode for transmission, because the TE mode light has a high confinement factor in the waveguide, a slight change in the refractive index of the waveguide material can cause a change in the effective refractive index of the waveguide, resulting in a larger phase change in the waveguide. Since the temperature difference in the waveguide decreases with the increase of pump light frequency, Figure 6 It can be seen that when the frequency of the pump light is below 1kHz, the phase shift of the structure remains basically unchanged due to the equilibrium state of heat accumulation and heat conduction. As the pump light frequency increases, the phase shift of the structure decreases sharply. When the pump light frequency decreases from 1MHz to 100Hz, the phase shift of the device increases by 50 times.

[0068] Figure 7 and Figure 8 is the temperature distribution of the structure at different times when the pump light frequency is 1kHz. Figure 7 This is the temperature distribution when the pump light is initially applied. It can be seen that the heat source comes from the air envelope on the upper and lower surfaces of the waveguide. After a period of heat conduction, the heat is gradually transferred to the waveguide. Figure 8 The temperature distribution at a time of 0.05ms. When the highest temperature is reached, the temperature distribution in the waveguide is still relatively uniform. Through experiments, it can be found that the difference between the highest temperature in the waveguide and the average temperature in the waveguide is less than 1mK.

[0069] In another embodiment, the polarization of the pump light is TE mode, and its electric field distribution is as follows: Fig. 9 When the pump light adopts TE mode, the electric field is mostly confined in the waveguide core layer, and the confinement factor in the upper and lower air claddings is only 9%. Fig.10 and Fig.11 As shown in FIG. 1 , if the modulation is performed at the same frequency, the maximum temperature obtained will be much lower than that in the TM mode. When the pump light is transmitted in the TE mode, the maximum temperature obtained is only 6% of that in the previous embodiment. As a result, the change in the waveguide phase caused by temperature is also only about 6% of that in the previous embodiment (e.g. Fig.12 shown).

[0070] In some embodiments, the wavelength of the pump light is selected to be the wavelength at the absorption peak of the gas to be measured to enhance the absorption of the wavelength by the gas to be measured, thereby converting more into heat energy. The detection light is the wavelength at the non-absorption peak of the gas to be measured to reduce the impact of the gas to be measured on the detection signal intensity.

[0071] It can be seen that the pump light of the on-chip gas sensor disclosed in this embodiment adopts the TM mode and the detection light adopts the TE mode, taking into account the high absorption of the pump light by the gas to be measured and the weak influence on the detection light, thereby improving the detection accuracy of the gas. Compared with the photothermal interferometry method in optical fiber sensing, the interaction between the pump light and the gas to be measured is greatly improved, and the length of the detection waveguide is greatly shortened while ensuring high sensitivity, and the device size can be reduced to the micron level.

[0072] Another embodiment of the present invention discloses an on-chip gas sensor assembly, wherein the on-chip gas sensor assembly includes the on-chip gas sensor described in any of the above embodiments. Fig.13 As shown, including:

[0073] A pump light transmitter 11, which is used to transmit pump light, wherein the wavelength and intensity of the pump light are modulated by a periodic function;

[0074] A first polarization controller 12, wherein the first polarization controller 12 is used to convert the pump light into a TM mode;

[0075] A detection light emitter 13, wherein the detection light emitter 13 is used to emit detection light;

[0076] A second polarization controller 14, wherein the second polarization controller 14 is used to convert the detection light into a TE mode;

[0077] A beam splitter 15, the beam splitter 15 is used to split the TE mode detection light into two;

[0078] A first beam combiner 16, wherein the first beam combiner 16 is used to receive TM mode pump light and TE mode detection light and transmit them to an on-chip gas sensor 17;

[0079] A second beam combiner 18, wherein the second beam combiner 18 is used to receive the TE mode detection light processed by the acousto-optic modulator 19 and the light coupled by the on-chip gas sensor 17;

[0080] The detector 20 is used to receive the laser signal emitted by the second beam combiner 18 and perform a series of processing on the laser signal to obtain corresponding parameters of the measured gas.

[0081] The on-chip gas sensor in the on-chip gas sensor assembly is the on-chip gas sensor described in any of the above embodiments, and the refractive index of the upper waveguide material layer of the ridge waveguide layer is greater than the refractive index of the lower waveguide material layer, and can simultaneously support TM mode pump light and TE mode detection light. That is, the high absorption of the measured gas on the pump light and the weak influence on the detection light are taken into account at the same time, thereby improving the detection accuracy of the gas. Moreover, a simpler waveguide structure is adopted, the waveguide preparation process is simple, and the loss of the waveguide is relatively low. Compared with the photothermal interference method in optical fiber sensing, it not only greatly improves the interaction between the pump light and the measured gas, but also greatly shortens the length of the detection waveguide while ensuring high sensitivity, and the device size can be reduced to the micron level.

[0082] In addition, compared with the on-chip optical waveguide structure made of traditional optical fiber or silicon material, the waveguide structure of the on-chip gas sensor disclosed in the present invention is made of chalcogenide glass, which has more obvious advantages for gas detection in the mid-infrared band.

[0083] The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The "first" and "second" mentioned in the text are only for distinction and are not intended to limit the content of the present invention.

[0084] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An on-chip gas sensor, characterized in that: include: Silicon substrate; A silicon oxide cladding layer, wherein the silicon oxide cladding layer is arranged on surfaces of both ends of the silicon substrate, and a lower air cladding layer is arranged in the middle of the silicon oxide cladding layer; A ridge waveguide layer, wherein the ridge waveguide layer is disposed on the surface of the silicon oxide cladding layer and the lower air cladding layer, and the refractive index of the upper waveguide material layer of the ridge waveguide layer is greater than the refractive index of the lower waveguide material layer; An upper air cladding layer, wherein the upper air cladding layer is arranged on the surface of the ridge waveguide layer; The pump light of the on-chip gas sensor is in TM mode, and the detection light is in TE mode.

2. The on-chip gas sensor according to claim 1, characterized in that: The upper waveguide material layer and the lower waveguide material layer are made of chalcogenide glass.

3. The on-chip gas sensor according to claim 2, characterized in that: The upper waveguide material layer is made of GeSbSe.

4. The on-chip gas sensor according to claim 2, characterized in that: The lower waveguide material layer is made of GeSbS.

5. The on-chip gas sensor according to claim 1, characterized in that: The thickness of the lower waveguide material layer is 1 / 4-1 / 2 of the thickness of the ridge waveguide layer.

6. The on-chip gas sensor according to claim 5, characterized in that: The thickness of the ridge waveguide layer is 100 nanometers to 300 nanometers.

7. The on-chip gas sensor according to claim 1, characterized in that: The wavelength of the pump light is the wavelength at the absorption peak of the gas to be measured, and the wavelength of the detection light is the wavelength at the non-absorption peak of the gas to be measured.

8. The on-chip gas sensor according to claim 1, characterized in that: The wavelength and intensity of the pump light are modulated by a periodic function.

9. The on-chip gas sensor according to claim 8, characterized in that: The periodic function is a trigonometric function, a periodic rectangular pulse function or a periodic triangular function.

10. An on-chip gas sensor assembly, characterized in that: The on-chip gas sensor assembly comprises the on-chip gas sensor according to any one of claims 1-9.

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