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

Abstract

The invention relates to an on-chip photo-thermal gas sensor and an on-chip gas sensor assembly. According to the on-chip photo-thermal gas sensor, a photo-thermal gas sensor with a Mach-Zehnder interference structure is integrated on a chip, and compared with a traditional photo-thermal interference method in free space and optical fiber sensing, the on-chip photo-thermal gas sensor has the advantages that a detection arm and a reference arm are located on the same substrate; the influence of external vibration on the interference structure is far less than that of an optical fiber sensing system. Moreover, additional phase control units such as PZT and AOM are not needed, the detection system is simplified, and the possibility of miniaturization of the whole sensing detection system is created. Meanwhile, the refractive index of the upper waveguide material layer of the ridge-shaped waveguide layer of the detection arm is larger than that of the lower waveguide material layer, and pump light in a TM mode and detection light in a TE mode can be supported at the same time. The interaction between the pump light and the gas to be detected is greatly improved, the spot size of the pump light is reduced, and the length of the detection waveguide is greatly shortened while high sensitivity is ensured.

Description

Technical Field

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

[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. In trace gas detection, photothermal spectroscopy (PTS) is a commonly used method in fiber optic sensing. PTS technology is based on the absorption of light by the molecules to be measured, which causes the excitation of internal energy levels, and then the transfer of energy caused by collision relaxation leads to an increase in local temperature, and the change in temperature will cause a change in the refractive index of the material. Unlike the traditional direct absorption spectroscopy (DAS) method, this method is an indirect light absorption analysis method. It measures the effect caused by light absorption in the sample. The PTS device usually uses a pump light source to heat the sample and uses a detection laser light source to detect the change in refractive index caused by temperature change. The change in refractive index will cause the detection light passing through the heated sample to shift in phase, and high-sensitivity measurements are achieved through interferometer structures, such as Mach-Zehnder and Fabry–Pérot resonators.

[0004] Among them, Mach-Zehnder is a one-way interferometer, and the detection light is divided into two beams. One beam of light penetrates the heated sample area to form a sensing beam, and the other beam of light is not affected by the heated area to form a reference beam, which is then passed through a beam combiner to form an interference light. The light power received by the detector depends on the phase difference between the two beams of light. At present, in the fiber optic sensing system, trace gas detection at the ppb level can be achieved based on PTS technology. However, the detection device formed by the optical fiber system is easily interfered by the external environment and is difficult to apply in scenarios outside the laboratory. Summary of the invention

[0005] Based on this, it is necessary to provide an on-chip photothermal gas sensor and an on-chip gas sensor assembly to address the above problems, so as to eliminate the influence of the external environment on the interference structure through an integrated on-chip waveguide design.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] An on-chip photothermal gas sensor, comprising:

[0008] substrate;

[0009] An incident waveguide, the incident waveguide being arranged at one end of the substrate surface and used for receiving a detection laser;

[0010] A beam splitter, which is arranged on the surface of the substrate and is used to split the detection laser emitted by the incident waveguide into two beams;

[0011] A detection arm, which is arranged at a middle position of the substrate surface and is used to be filled with the gas to be measured and receive the detection laser split by the beam splitter;

[0012] A reference arm, which is arranged side by side with the detection arm at a middle position of the substrate surface and receives the detection laser split by the beam splitter, and the length of the reference arm is not equal to the length of the detection arm;

[0013] A beam combiner, the beam combiner is arranged on the surface of the substrate and is used to combine the detection lasers emitted by the detection arm and the reference arm into one beam;

[0014] An output waveguide is arranged at the other end of the substrate surface, and is used to receive the detection laser emitted by the beam combiner and emit the detection laser out of the on-chip photothermal gas sensor.

[0015] The on-chip photothermal gas sensor disclosed in the present invention integrates a photothermal gas sensor with a Mach-Zehnder interference structure on a chip. Compared with the photothermal interference method in traditional free space and fiber optic sensing, since the detection arm and the reference arm are both on the same substrate, the impact of external vibration on the interference structure is much smaller than that of the fiber optic sensing system. In addition, no additional phase control unit, such as PZT, AOM, etc., is required, which simplifies the detection system and creates the possibility of miniaturization of the entire sensing detection system.

[0016] In another embodiment, the detection laser includes TM mode pump light and TE mode detection light.

[0017] In another embodiment, the detection arm comprises:

[0018] A silicon oxide cladding layer, wherein the silicon oxide cladding layer is arranged on the surface of the substrate, and a lower air cladding layer is arranged in the middle of the silicon oxide cladding layer;

[0019] 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;

[0020] An upper air cladding layer is arranged on the surface of the ridge waveguide layer.

[0021] In this embodiment, the refractive index of the upper waveguide material layer of the detection arm 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. Therefore, the on-chip photothermal gas sensor disclosed in the present invention greatly improves the interaction between the pump light and the measured gas, and reduces the spot size of the pump light, while ensuring high sensitivity, greatly shortening the length of the detection waveguide, and realizing a highly compact photothermal gas sensor structure.

[0022] In another embodiment, the wavelength and intensity of the pump light are modulated by a periodic function.

[0023] In another embodiment, the wavelength of the pump light is the wavelength at the absorption peak of the gas being measured.

[0024] In another embodiment, the wavelength of the detection light corresponds to the wavelength at the orthogonal point of the Mach-Zehnder interference structure and at the non-absorption peak of the gas to be measured.

[0025] In another embodiment, the length difference between the reference arm and the detection arm is 1 micrometer to 1 centimeter.

[0026] This embodiment adopts a Mach-Zehnder interference structure, and the free spectrum range (FSR) of the interference fringes can be adjusted by adjusting the length of the reference arm and the detection arm, which has higher controllability, and the interference spectrum is not easily affected by the reflected light at each joint during the device processing. In another embodiment, a first wavelength division multiplexer is also provided in the incident waveguide.

[0027] In another embodiment, a second wavelength division multiplexer is further disposed in the output waveguide.

[0028] Yet another embodiment of the present invention discloses an on-chip gas sensor assembly, wherein the on-chip gas sensor assembly is the on-chip photothermal gas sensor described in any of the above embodiments.

[0029] The on-chip photothermal gas sensor assembly disclosed in the present invention integrates a photothermal gas sensor with a Mach-Zehnder interference structure on a chip. Compared with the photothermal interference method in traditional free space and fiber optic sensing, since the detection arm and the reference arm are both on the same substrate, the impact of external vibration on the interference structure is much smaller than that of the fiber optic sensing system. In addition, no additional phase control unit, such as PZT, AOM, etc., is required, which simplifies the detection system and creates the possibility of miniaturization of the entire sensing detection system.

[0030] In addition, the refractive index of the upper waveguide material layer of the detection arm 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, when the pump light is converted to TM mode by the first polarization controller and the detection light is converted to TE mode by the second polarization controller, the on-chip photothermal gas sensor assembly can simultaneously take into account the high absorption of the pump light by the gas to be measured and the weak effect on the detection light, thereby improving the detection accuracy of the gas. At the same time, the on-chip photothermal gas sensor assembly disclosed in the present invention adopts a Mach-Zehnder interference structure, and the free spectral region (FSR) of the interference fringes can be adjusted by adjusting the length of the reference arm and the detection arm, which has higher controllability, and the interference spectrum is not easily affected by the reflected light at each joint during the device processing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of an on-chip photothermal gas sensor disclosed in one embodiment of the present invention;

[0032] Figure 2 A schematic diagram of the structure of a detection arm in an on-chip photothermal gas sensor disclosed in one embodiment of the present invention;

[0033] Figure 3 A graph showing the relationship between the normalized power of the pump light after amplitude modulation and time disclosed in an embodiment of the present invention;

[0034] Figure 4 A graph showing the relationship between the transmittance of light after passing through the Mach-Zehnder interference structure and the wavelength disclosed in an embodiment of the present invention;

[0035] Figure 5 A graph showing the relationship between the transmittance after passing through the Mach-Zehnder interference structure and the wavelength at different refractive indices disclosed in an embodiment of the present invention;

[0036] Figure 6 A graph showing the relationship between the normalized detection signal after passing through the Mach-Zehnder interferometer structure and time according to an embodiment of the present invention;

[0037] Figure 7 A schematic diagram of another on-chip photothermal gas sensor disclosed in another embodiment of the present invention;

[0038] Figure 8 A schematic diagram of another on-chip photothermal gas sensor disclosed in another embodiment of the present invention;

[0039] Fig. 9 A schematic diagram of the structure of an on-chip sensor component disclosed in another embodiment of the present invention;

[0040] Fig.10 The figure is a schematic diagram of the structure of another on-chip sensor component disclosed in another embodiment of the present invention.

[0041] In the figure, 1, substrate; 2, incident waveguide; 3, beam splitter; 4, detection arm; 5, reference arm; 6, beam combiner; 7, output waveguide; 21, first wavelength division multiplexer; 71, second wavelength division multiplexer; 11, pump light emitter; 12, first polarization controller; 13, detection light emitter; 14, second polarization controller; 15, off-chip beam combiner; 16, on-chip photothermal gas sensor; 17, detector; 41, silicon oxide cladding; 42, lower air cladding; 43, upper waveguide material layer; 44, lower waveguide material layer; 45, upper air cladding. DETAILED DESCRIPTION

[0042] 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.

[0043] 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.

[0044] The embodiment of the present invention discloses an on-chip photothermal gas sensor, such as Figure 1 As shown, the on-chip photothermal gas sensor comprises:

[0045] A substrate 1, wherein the substrate 1 may be a silicon-based substrate;

[0046] An incident waveguide 2, the incident waveguide 2 being arranged at one end of the surface of the substrate 1 and being used for receiving a detection laser;

[0047] A beam splitter 3, the beam splitter 3 is arranged on the surface of the substrate 1, and is used to split the detection laser emitted by the incident waveguide 2 into two beams;

[0048] A detection arm 4, which is arranged at a middle position on the surface of the substrate 1 and is used to be filled with the gas to be measured and receive the detection laser split by the beam splitter 3;

[0049] A reference arm 5, which is arranged side by side with the detection arm 4 at the middle position of the surface of the substrate 1 and receives the detection laser split by the beam splitter 3, and the length of the reference arm 5 is not equal to the length of the detection arm 4;

[0050] A beam combiner 6, which is arranged on the surface of the substrate 1 and is used to combine the detection lasers emitted by the detection arm 4 and the reference arm 5 into one beam;

[0051] An output waveguide 7 is provided at the other end of the surface of the substrate 1 and is used for receiving the detection laser emitted by the beam combiner 6 and emitting the detection laser out of the on-chip photothermal gas sensor.

[0052] in, Figure 1 middle" " is the light transmission path, that is Figure 1 It shows the structure of the on-chip photothermal gas sensor and also shows the transmission of light.

[0053] In this embodiment, the detection laser is composed of detection light and pump light. When performing gas detection, the detection laser is injected through the incident waveguide 2, and then the detection laser is divided into two beams by the beam splitter 3, one of which is injected into the detection arm 4, and the other is injected into the reference arm 5. Among them, the pump light injected into the detection arm 4 will excite the gas to be measured filled in the detection arm 4, so that the temperature of the gas to be measured will increase, and the change in temperature will cause the refractive index of the detection arm 4 to change. The change in refractive index will cause the detection light passing through the detection arm 4 to shift in phase. The detection laser passing through the detection arm 4 and the reference arm 5 is combined by the beam combiner 6 and then exported by the output waveguide 7 to the outside of the on-chip photothermal gas sensor for subsequent processing.

[0054] The on-chip photothermal gas sensor disclosed in this embodiment integrates a photothermal gas sensor with a Mach-Zehnder interference structure on the chip. Compared with the photothermal interference method in traditional free space and fiber optic sensing, since the detection arm and the reference arm are both on the same substrate, the impact of external vibration on the interference structure is much smaller than that of the fiber optic sensing system. In addition, no additional phase control unit, such as PZT, AOM, etc., is required, which simplifies the detection system and creates the possibility of miniaturization of the entire sensing detection system.

[0055] In another embodiment, the detection laser includes TM mode pump light and TE mode detection light.

[0056] In this embodiment, the incident waveguide, beam splitter, detection arm and reference arm, beam combiner and output waveguide should all support the transmission of quasi-transverse electric (quasi-TE) and quasi-transverse magnetic (quasi-TM) modes. Specifically, the waveguide structures of the beam splitter and beam combiner include but are not limited to multi-mode interference (MMI) structures, directional coupler structures and other devices with similar beam splitting / combining functions.

[0057] Relatively speaking, the TM mode pump light has a better excitation effect on the gas being measured. In this regard, another embodiment of the present invention discloses a detection arm structure of an on-chip photothermal gas sensor, such as Figure 2 As shown, the detection arm comprises:

[0058] A silicon oxide cladding layer 41, wherein the silicon oxide cladding layer 41 is disposed on the surface of the substrate 1, and a lower air cladding layer 42 is disposed in the middle of the silicon oxide cladding layer 41;

[0059] A ridge waveguide layer, wherein the ridge waveguide layer is disposed on the surface of the silicon oxide cladding layer 41 and the lower air cladding layer 42, the ridge waveguide layer is composed of an upper waveguide material layer 43 and a lower waveguide material layer 44, and the refractive index of the upper waveguide material layer 43 of the ridge waveguide layer is greater than the refractive index of the lower waveguide material layer 44;

[0060] An upper air cladding layer 45 is provided on the surface of the ridge waveguide layer.

[0061] The on-chip photothermal gas sensor disclosed in this embodiment has a refractive index of the upper waveguide material layer of the detection arm ridge waveguide layer 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, it takes into account the high absorption of the measured gas on the pump light and the weak influence on the detection light, thereby improving the detection accuracy of the gas. Therefore, the on-chip photothermal gas sensor disclosed in the present invention greatly improves the interaction between the pump light and the measured gas, and reduces the spot size of the pump light, while ensuring high sensitivity. At the same time, it greatly shortens the length of the detection waveguide, and realizes a highly compact photothermal gas sensor structure.

[0062] In terms of specific material selection, the ridge waveguide layer should have low optical loss at both the pump light wavelength and the detection light wavelength, so its materials include but are not limited to silicon nitride, chalcogenide glass, lithium niobium oxide, hafnium oxide, and polymer macromolecules.

[0063] In this embodiment, the upper waveguide material layer and the lower waveguide material layer of the detection arm are made of chalcogenide glass, which has more obvious advantages for gas detection in the mid-infrared band. More specifically, the upper waveguide material layer is made of GeSbSe, and the lower waveguide material layer is made of GeSbS. 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 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 value 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. However, the setting of the thickness of the upper and lower waveguide material layers in the ridge waveguide layer must also be adapted to the wavelength of the pump light and the detection light, so it can be adjusted according to the wavelength of the pump light and the detection light in actual design.

[0064] In another embodiment, the thickness of the silicon oxide cladding in the detection arm 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 micrometers, or 2 micrometers, 3 micrometers, or 7 micrometers, 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.

[0065] In another embodiment, the limitation factor can be further improved by optimizing the width of the ridge waveguide, the total height of the waveguide, and the thickness of the slab waveguide region. More preferably, the width of the ridge 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 point, the limitation factor of the on-chip photothermal gas sensor disclosed in this embodiment is as high as 124%, which greatly improves the interaction between the pump light and the detected gas.

[0066] In another embodiment, the length difference between the reference arm and the detection arm is 1 micron to 1 centimeter. Under the action of the periodic function modulated pump light, the length difference between the reference arm and the detection arm actually reflects the phase difference of the detection laser signal after passing through the reference arm and the detection arm. This embodiment can adjust the free spectrum range (FSR) of the interference fringes by adjusting the length of the reference arm and the detection arm, has higher controllability, and the interference spectrum is not easily affected by the reflected light at various joints during the device processing process.

[0067] In another embodiment, the wavelength of the pump light is selected to be the wavelength at the absorption peak of the gas to be measured, so as to enhance the absorption of the wavelength by the gas to be measured, thereby converting more into heat energy.

[0068] In another embodiment, the wavelength and intensity of the pump light are modulated by a periodic function. Specifically, the periodic function is a trigonometric function, a periodic rectangular pulse function, or a periodic triangular function.

[0069] The relationship between the normalized power of the pump light after amplitude modulation and time is as follows: Figure 3 As shown. It can be seen that the amplitude of the pump light changes periodically under the modulation of the sine function, and the modulation of the pump light power can be expressed by the following formula (1):

[0070] P(t)=P avg +P m sinωt(1)

[0071] Wherein, Pavg and Pm are the average power and power modulation amplitude of the pump light, and ω is the modulation frequency of the pump light.

[0072] During the detection process, the photons of the pump light are absorbed by the molecules to be tested filled in the detection arm, generating a local heat source. After the heat is transmitted and diffused, the temperature of the waveguide changes, which in turn affects the refractive index of the waveguide. In the reference arm, since there are no molecules to be tested that absorb the pump light, the temperature and refractive index of the waveguide will not change. Therefore, the two detection laser beams transmitted in the detection arm and the reference arm will produce a phase difference before reaching the beam combiner. The combined light will cause the light intensity detected by the detector to change due to the existence of this phase difference. In this way, the influence of background light intensity changes on the test results can be eliminated.

[0073] In another embodiment, the wavelength of the detection light corresponds to the wavelength at the orthogonal point of the Mach-Zehnder interference structure and at the non-absorption peak of the gas to be measured.

[0074] The specific principles for selecting the detection light wavelength are as follows:

[0075] The relationship between the transmittance of light after passing through the Mach-Zehnder interference structure and the wavelength is as follows: Figure 4 As shown. The transmittance of the interference structure changes with the wavelength in a sinusoidal function, so the wavelength of the detection light is selected as the wavelength at the orthogonal point of the Mach-Zehnder interference structure and should meet the requirements that the waveguide material and the molecules to be measured have low optical absorption. Specifically, the wavelength of the detection light corresponds to the orthogonal point of the Mach-Zehnder interference structure and is the wavelength at the non-absorption peak of the gas to be measured. The wavelength of the detection light at the orthogonal point of the Mach-Zehnder interference structure is as follows: Figure 4 The middle arrow points to a point where theoretically the transmittance is half of the total transmittance.

[0076] The relationship between the transmittance after the Mach-Zehnder interference structure and the wavelength at different refractive indices is as follows: Figure 5As shown in the figure, when the effective refractive index of the detection arm of the Mach-Zehnder interference structure changes under the action of the pump light, the transmittance of the structure changes, and the spectrum shift can be seen from the spectrum. Among them, the black dotted line represents the spectral response when the effective refractive index of the detection arm is neff1, and the black solid line is the spectral response when the effective refractive index of the detection arm increases to neff2 under the influence of temperature. ΔT is the change in the detection light intensity at the detection wavelength.

[0077] The relationship between the normalized detection signal and time after the Mach-Zehnder interferometer structure is as follows: Figure 6 As shown. Among them, the dotted straight line represents the output signal of the detector when the phase difference between the two arms (detection arm and reference arm) in the Mach-Zehnder interference structure is 0. At this time, the constructive interference light is the strongest and the signal is the largest. The solid straight line represents the output signal of the detector when the phase difference between the two arms in the Mach-Zehnder interference structure is π. At this time, the destructive interference light is the strongest and the signal is the smallest. In this embodiment, the wavelength of the detection light corresponds to the wavelength at the orthogonal point of the Mach-Zehnder interference structure and the non-absorption peak of the gas to be measured. At this time, the detected signal is half of the difference between the maximum and minimum signals. Under the modulation of periodic pump light, the modulation component of the signal power measured at the output end of the Mach-Zehnder interference structure can be expressed by formula (2):

[0078]

[0079] Therefore, from the above analysis, it can be seen that under the drive of the periodic pump light modulation signal, the signal detected by the detector is a periodic signal. The two signals have the same modulation frequency. Through the Fourier transform technology, the 1f and 2f signals of the signal can be obtained. The signal is proportional to the concentration of the detected gas, and the strength of the signal does not change with the intensity of the detection light.

[0080] Another embodiment discloses another on-chip photothermal gas sensor, wherein the incident waveguide of the on-chip photothermal gas sensor can be an on-chip end face coupler plus a strip waveguide structure or a grating coupler plus a strip waveguide structure. Figure 7 As shown, a first wavelength division multiplexer 21 is also provided in the incident waveguide. Figure 8 As shown, a first wavelength division multiplexer 21 is further disposed in the incident waveguide, and a second wavelength division multiplexer 71 is further disposed in the output waveguide.

[0081] The above embodiments integrate an off-chip combiner or an off-chip beam splitter on-chip, which is specifically achieved through an on-chip wavelength division multiplexing structure. For example, a 2×2 MMI or a 2×2 directional coupler can be integrated on-chip. By designing a dedicated on-chip wavelength division multiplexing structure, the pump light can be transmitted only in the detection arm, and the detection light can be transmitted in the detection arm and the reference arm, further improving the optical power of the pump light in the detection arm.

[0082] Moreover, according to different detection schemes, the end coupler or grating coupler can be designed into the corresponding TE or (and) TM transmission mode. Figure 1 In the on-chip photothermal gas sensor structure shown in FIG, the incident waveguide and the output waveguide need to support both the TM and TE modes, that is, the end coupler or grating coupler used needs to support both the TM and TE modes; Figure 8 In the on-chip photothermal gas sensor structure shown, since the detection light and the pump light are separately injected into and emitted from the on-chip photothermal gas sensor, the end couplers or grating couplers of the incident waveguide port and the output waveguide port corresponding to the detection light can only support the TE mode, while the end couplers or grating couplers of the incident waveguide port and the output waveguide port corresponding to the pump light can only support the TM mode.

[0083] Yet another embodiment of the present invention discloses an on-chip gas sensor assembly, which includes the on-chip photothermal gas sensor described in any one of the above embodiments.

[0084] Among them, Fig. 9 As shown, the on-chip gas sensor assembly includes:

[0085] 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;

[0086] A first polarization controller 12, wherein the first polarization controller 12 is used to convert the pump light into a preset mode, such as a TM mode;

[0087] A detection light emitter 13, wherein the detection light emitter 13 is used to emit detection light;

[0088] A second polarization controller 14, wherein the second polarization controller 14 is used to convert the detection light into a preset mode, such as a TE mode;

[0089] An off-chip beam combiner 15, wherein the off-chip beam combiner 15 is used to combine the detection light and the pump light into a detection laser beam;

[0090] An on-chip photothermal gas sensor 16, wherein the incident waveguide and the output waveguide of the on-chip photothermal gas sensor 16 support both TE mode and TM mode detection lasers, and are used to receive the detection lasers emitted by the off-chip combiner 15;

[0091] The detector 17 is used to receive the laser signal emitted by the output waveguide of the on-chip photothermal gas sensor 16 and perform a series of processing on the laser signal to obtain corresponding parameters of the measured gas.

[0092] Or, if Fig.10As shown, the on-chip gas sensor assembly includes:

[0093] 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;

[0094] A first polarization controller 12, wherein the first polarization controller 12 is used to convert the pump light into a preset mode, such as a TM mode;

[0095] A detection light emitter 13, wherein the detection light emitter 13 is used to emit detection light;

[0096] A second polarization controller 14, wherein the second polarization controller 14 is used to convert the detection light into a preset mode, such as a TE mode;

[0097] An on-chip photothermal gas sensor 16, wherein the incident waveguide and the exit waveguide of the on-chip photothermal gas sensor 16 support detection lasers in both TE mode and TM mode, a first wavelength division multiplexer is provided in the incident waveguide, and a second wavelength division multiplexer is also provided in the exit waveguide, and the on-chip photothermal gas sensor 16 is used to receive the pump light emitted by the first polarization controller 12 and the detection light emitted by the second polarization controller 14;

[0098] The detector 17 is used to receive the laser signal emitted by the output waveguide of the on-chip photothermal gas sensor 16 and perform a series of processing on the laser signal to obtain corresponding parameters of the measured gas.

[0099] The on-chip photothermal gas sensor assembly disclosed in the embodiment of the present invention integrates a photothermal gas sensor with a Mach-Zehnder interference structure on a chip. Compared with the photothermal interference method in traditional free space and fiber optic sensing, since the detection arm and the reference arm are both on the same substrate, the impact of external vibration on the interference structure is much smaller than that of the fiber optic sensing system. In addition, no additional phase control unit, such as PZT, AOM, etc., is required, which simplifies the detection system and creates the possibility of miniaturization of the entire sensing detection system.

[0100] In addition, the refractive index of the upper waveguide material layer of the detection arm 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, when the pump light is converted to TM mode by the first polarization controller and the detection light is converted to TE mode by the second polarization controller, the on-chip photothermal gas sensor assembly can simultaneously take into account the high absorption of the pump light by the gas to be measured and the weak effect on the detection light, thereby improving the detection accuracy of the gas. At the same time, the on-chip photothermal gas sensor assembly disclosed in the present invention adopts a Mach-Zehnder interference structure, and the free spectral region (FSR) of the interference fringes can be adjusted by adjusting the length of the reference arm and the detection arm, which has higher controllability, and the interference spectrum is not easily affected by the reflected light at each joint during the device processing process.

[0101] 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.

[0102] 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 photothermal gas sensor, characterized in that: include: substrate; An incident waveguide, the incident waveguide being arranged at one end of the substrate surface and used for receiving a detection laser; A beam splitter, which is arranged on the surface of the substrate and is used to split the detection laser emitted by the incident waveguide into two beams; A detection arm, which is arranged at a middle position of the substrate surface and is used to be filled with the gas to be measured and receive the detection laser split by the beam splitter; A reference arm, which is arranged side by side with the detection arm at a middle position of the substrate surface and receives the detection laser split by the beam splitter, and the length of the reference arm is not equal to the length of the detection arm; A beam combiner, the beam combiner is arranged on the surface of the substrate and is used to combine the detection lasers emitted by the detection arm and the reference arm into one beam; An output waveguide is arranged at the other end of the substrate surface, and is used to receive the detection laser emitted by the beam combiner and emit the detection laser out of the on-chip photothermal gas sensor.

2. The on-chip photothermal gas sensor according to claim 1, characterized in that: The detection laser includes TM mode pump light and TE mode detection light.

3. The on-chip photothermal gas sensor according to claim 2, characterized in that: The detection arm comprises: A silicon oxide cladding layer, wherein the silicon oxide cladding layer is arranged on the surface of the 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 is arranged on the surface of the ridge waveguide layer.

4. The on-chip photothermal gas sensor according to claim 2, characterized in that: The wavelength and intensity of the pump light are modulated by a periodic function.

5. The on-chip photothermal gas sensor according to claim 2, characterized in that: The wavelength of the pump light is the wavelength at the absorption peak of the gas being measured.

6. The on-chip photothermal gas sensor according to claim 1, characterized in that: The wavelength of the detection light corresponds to the wavelength at the orthogonal point of the Mach-Zehnder interference structure and at the non-absorption peak of the gas to be measured.

7. The on-chip photothermal gas sensor according to claim 1, characterized in that: The difference between the length of the reference arm and the length of the detection arm is 1 micrometer to 1 centimeter.

8. The on-chip photothermal gas sensor according to claim 1, characterized in that: A first wavelength division multiplexer is also arranged in the incident waveguide.

9. The on-chip photothermal gas sensor according to claim 1, characterized in that: A second wavelength division multiplexer is also arranged in the output waveguide.

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

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