On-chip multi-component gas sensing system and detection method

Abstract

The present application belongs to the technical field of infrared analyte detection, and particularly relates to a multi-component gas sensing system on a chip, which comprises a near-infrared narrow linewidth probe laser, a near-infrared tunable pump laser module, a near-infrared broadband photonic crystal slow light waveguide, a Mach-Zehnder interferometer on a chip, a fiber coupler, a fiber beam splitter, a fiber filter, a low-pass filter module, a phase adjustment module and a signal processing module. By optimizing the structure of the photonic crystal, eight modes are generated, and the eight modes have a slow light bandwidth of about 200 nm. The probe laser can excite the even mode of the near-infrared broadband photonic crystal slow light waveguide at 1550 nm. The pump laser can excite the even mode or the odd mode of the near-infrared broadband photonic crystal slow light waveguide at the wavelength of the gas absorption peak, and these modes can cover the range of 1500-1700 nm to generate a slow light effect and realize multi-component gas detection.

Description

Technical Field

[0001] This invention belongs to the field of infrared analyte detection technology, specifically relating to an on-chip multi-component gas sensing system and detection method. Background Technology

[0002] Photothermal interferometry utilizes minute heat changes generated by the photothermal effect to detect the light absorption characteristics of gases. When laser light is absorbed by a gas, the gas molecules generate heat through relaxation, causing changes in the material's temperature and refractive index. These changes induce phase changes in the laser light, resulting in an interference effect. By measuring the changes in the interference signal, the gas's light absorption characteristics and concentration information can be obtained. The sensitivity of waveguide-based gas sensors is limited by weak evanescent fields and short optical path lengths. Photonic crystal waveguides can achieve slow light effects, effectively reducing the group velocity of light, increasing the optical path length, and improving the detection performance of waveguide-based gas sensors.

[0003] Existing patent "202210051808.7" entitled "A Photothermal Interference Spectroscopy Gas Sensing Device and Detection Method Based on Near-Infrared Dual-Wavelength Photonic Crystal Slow Waveguide" discloses a dual-wavelength photonic crystal slow waveguide sensor based on photothermal interference spectroscopy technology. This sensor simultaneously generates a slow light effect in both the near-infrared probe and pump light bands, increasing the effective optical path of the device, enhancing the absorption of the pump light by the analyte and the phase accumulation of the near-infrared probe light, thereby improving the sensor's sensitivity and response speed. However, the detection bandwidth of photonic crystal waveguides is typically only tens of nanometers, limiting its application to the detection of only one specific gas.

[0004] There is also patent "201610874377.9" entitled "A photonic crystal slow light waveguide device and a method for obtaining slow light effect". This waveguide device achieves the slow light effect by filling the first and second rows of holes on both sides of the defect of the photonic crystal waveguide with photofluid. However, the bandwidth of this device is only tens of nanometers and the implementation method is complicated.

[0005] In addition, many gases exhibit characteristic absorption in the near-infrared wavelength range of 1500 nm to 1700 nm, and the aforementioned devices all face the problem of detecting only a limited range of gases. Summary of the Invention

[0006] To address the problems of short effective optical path, low sensitivity, and single-component detection in existing optical waveguide gas sensing systems, this invention discloses an on-chip multi-component gas sensing system. By introducing three rows of defective holes within a conventional photonic crystal and optimizing the size and spacing of these holes, the photonic crystal waveguide generates eight modes, forming a near-infrared broadband photonic crystal slow-light waveguide. These eight modes possess a slow-light bandwidth approaching 200 nm. A probe laser at 1550 nm excites even modes in the near-infrared broadband photonic crystal slow-light waveguide. A pump laser at the gas absorption peak wavelength excites either even or odd modes in the near-infrared broadband photonic crystal slow-light waveguide. These modes cover the 1500-1700 nm range, generating a slow-light effect that covers the absorption peaks of various gases, enabling the detection of multiple gas components.

[0007] The technical solution adopted in this invention is as follows:

[0008] An on-chip multi-component gas sensing system includes a near-infrared narrow-linewidth detection laser, a near-infrared tunable pump laser module, an on-chip Mach-Zehnder interferometer, an optical fiber coupler, an optical fiber beam splitter, an optical fiber filter, a low-pass filter module, a phase adjustment module, and a signal processing module.

[0009] The output of the near-infrared narrow linewidth probe laser is connected to one input of the fiber coupler, and the output of the near-infrared tunable pump laser module is connected to the other input of the fiber coupler.

[0010] The output of the fiber optic coupler is connected to the input of the on-chip Mach-Zehnder interferometer;

[0011] The input of the fiber optic filter is connected to the output of the on-chip Mach-Zehnder interferometer;

[0012] The output of the fiber optic filter is connected to the input of the fiber optic beam splitter.

[0013] One output of the fiber optic beam splitter is connected to the signal processing module, and the other is connected to the low-pass filter module.

[0014] The output of the low-pass filter module is connected to the input of the phase adjustment module.

[0015] Preferably, the near-infrared tunable pump laser module includes a near-infrared tunable laser, an acousto-optic modulator, a signal generator, and a polarization controller. The acousto-optic modulator has an optical fiber input, an optical fiber output, and a voltage input. The optical fiber input of the acousto-optic modulator is connected to the output of the near-infrared tunable laser, the optical fiber output of the acousto-optic modulator is connected to the input of the polarization controller, and the voltage input of the acousto-optic modulator is connected to the output of the signal generator. The near-infrared tunable laser generates near-infrared pump laser light that is absorbed by the gas, with a wavelength tuning range of 1500-1700 nanometers.

[0016] Preferably, the on-chip Mach-Zehnder interferometer includes a near-infrared broadband photonic crystal slow waveguide, an input waveguide, an output waveguide, a first beam splitter waveguide, a second beam splitter waveguide, a beam combiner waveguide, a first multimode waveguide, a second multimode waveguide, a first single-mode waveguide, a second single-mode waveguide, and metal electrodes;

[0017] One arm of the on-chip Mach-Zehnder interferometer has a near-infrared broadband photonic crystal slow waveguide, and the other arm has a first single-mode waveguide, which is used to realize the interference of near-infrared detection laser;

[0018] The input waveguide serves as the input terminal of the on-chip Mach-Zehnder interferometer, used for coupling the input near-infrared detection laser and the near-infrared pump laser; the output waveguide serves as the output terminal of the on-chip Mach-Zehnder interferometer, used for coupling the output near-infrared detection laser and the near-infrared pump laser.

[0019] The first beam splitter waveguide is used for beam splitting, and the beam combiner waveguide is used for beam combining; the first single-mode waveguide can simultaneously conduct near-infrared probe laser and near-infrared pump laser.

[0020] The second beam splitter waveguide, the second single-mode waveguide, and the first multimode waveguide together constitute a mode converter, which is used to convert the fundamental mode of the second beam splitter waveguide into a higher-order mode of the first multimode waveguide. The first multimode waveguide contains both a fundamental mode and a higher-order mode. The fundamental mode is used to excite the even mode of the near-infrared broadband photonic crystal slow waveguide, and the higher-order mode is used to excite the odd mode of the near-infrared broadband photonic crystal slow waveguide.

[0021] The second multimode waveguide is connected to the beam combiner waveguide and is used to output the mode of the near-infrared broadband photonic crystal slow waveguide;

[0022] The metal electrode is located on top silicon and three micrometers away from the first single-mode waveguide, and is used to adjust the effective refractive index of the first single-mode waveguide.

[0023] The substrates of the input waveguide, output waveguide, first beam splitter waveguide, first single-mode waveguide, second beam splitter waveguide, second single-mode waveguide, first multimode waveguide, second multimode waveguide, and beam combiner waveguide are silicon, the core layer is silicon, the lower cladding is silicon dioxide, and the upper cladding is air.

[0024] Preferably, the near-infrared broadband photonic crystal slow waveguide simultaneously conducts near-infrared probe lasers and near-infrared pump lasers. The near-infrared broadband photonic crystal slow waveguide has three rows of defect holes and eight modes, exhibiting a slow light effect in the 1500-1700 nm wavelength range. The eight modes cover multiple gas absorption bands within the 1500-1700 nm wavelength range. The near-infrared broadband photonic crystal slow waveguide is a suspended air bridge structure with a silicon substrate, a silicon core layer, an air lower cladding, an air upper cladding, and a silicon dioxide support layer.

[0025] Preferably, the phase adjustment module includes a current source and a probe station. The positive output terminal of the current source is connected to one input terminal of the probe station, and the negative output terminal of the current source is connected to the other input terminal of the probe station. The probe station has two output terminals, which are respectively connected to two pads of the metal electrode.

[0026] Preferably, the fabrication method of the on-chip Mach-Zehnder interferometer is as follows:

[0027] Step 1: A photoresist mask is formed using electron beam exposure. Near-infrared broadband photonic crystal slow waveguide, input waveguide, output waveguide, first beam splitter waveguide, second beam splitter waveguide, beam combiner waveguide, first multimode waveguide, second multimode waveguide, first single-mode waveguide, and second single-mode waveguide with silicon dioxide as the cladding layer are prepared by dry etching. The photoresist is then removed using a photoresist remover.

[0028] Step 2: Fabricate metal electrodes. Use ultraviolet exposure to form a photoresist mask on top of the silicon layer in the metal electrode area. Use thermal evaporation to fabricate metal electrodes. Remove the photoresist using a stripper solution.

[0029] Step 3: Etching silicon dioxide. A photoresist mask is formed in the slow waveguide region of the near-infrared broadband photonic crystal using ultraviolet exposure. Hydrofluoric acid is used to etch the silicon dioxide under the slow waveguide of the near-infrared broadband photonic crystal to form an air bridge structure. The photoresist is removed by stripping solution, and finally all the structures of the on-chip Mach-Zehnder interferometer are formed.

[0030] A multi-component gas detection device includes an on-chip multi-component gas sensing system.

[0031] An on-chip multi-component gas sensing system includes:

[0032] Step 1: Adjust the emission wavelength of the near-infrared tunable laser so that the pump light wavelength is aligned with the absorption peak of the gas to be measured, and adjust the signal generator to achieve intensity modulation of the near-infrared pump laser.

[0033] Step 2: The near-infrared probe laser output from the near-infrared narrow linewidth probe laser and the near-infrared pump light output from the near-infrared tunable pump laser module are coupled into the input of the on-chip Mach-Zehnder interferometer via an optical fiber coupler.

[0034] Step 3: Adjust the fiber optic filter and beam splitter to enable the near-infrared detection laser to conduct through the low-pass filter module and signal processing module, while disabling the near-infrared pump laser;

[0035] Step 4: Based on the signal output by the low-pass filter module, adjust the phase adjustment module to stabilize the phase difference between the two arms of the on-chip Mach-Zehnder interferometer at 90°.

[0036] Step 5: Record the output signal of the second near-infrared detector in real time, and demodulate the photothermal interference signal using a lock-in amplifier;

[0037] Step 6: Analyze the detection performance of the device based on the photothermal interference signals measured at different gas concentrations.

[0038] Preferably, the near-infrared broadband photonic crystal slow waveguide of the on-chip Mach-Zehnder interferometer exhibits a slow light effect at 1500-1700 nm.

[0039] Preferably, the near-infrared broadband photonic crystal slow waveguide generates eight modes to form a near-infrared broadband photonic crystal slow waveguide, and the eight modes cover multiple gas absorption bands in the wavelength range of 1500-1700 nanometers.

[0040] The beneficial effects of this invention are:

[0041] 1. An on-chip multi-component gas sensing system can simultaneously generate a slow-light effect in both the near-infrared probe and pump light bands, enhancing gas absorption of the pump light and increasing phase accumulation of the probe light. Since silicon dioxide has a higher thermal conductivity than air, an air bridge structure is created by etching the silicon dioxide beneath the slow-light waveguide of the near-infrared broadband photonic crystal. This reduces heat diffusion, increases heat accumulation, amplifies the photothermal signal, and improves the sensitivity of the gas sensor.

[0042] 2. By introducing three rows of defect holes into a conventional photonic crystal and optimizing the size of the three rows of defect holes and the distance between them, a broadband photonic crystal slow waveguide is constructed, which has eight slow light modes. The probe laser can excite the even mode of the near-infrared broadband photonic crystal slow waveguide at 1550 nm, and the pump laser can excite the even mode or odd mode of the broadband photonic crystal slow waveguide at the gas absorption peak wavelength in the wavelength range of 1500-1700 nm. The slow light band can cover the absorption bands of various gases, and multi-component gas detection can be realized in the near-infrared band. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a system diagram of an on-chip multi-component gas sensing system according to the present invention;

[0045] Figure 2 The diagram shows the structure of a near-infrared broadband photonic crystal slow waveguide. After optimization, the radius of the large aperture is R = 0.35a, the radius of the central aperture is r0 = 0.6R, the radius of the center of the first row of small apertures adjacent to the central aperture is r1 = 0.7R, and the distance between the centers of the first row of small apertures on both sides of the central aperture is W1 = ×a, the distance between the centers of the second row of small holes on both sides of the central hole is W2.1 = 2.1. ×a, lattice constant a = 530 nm;

[0046] Figure 4 The dispersion diagram of the near-infrared broadband photonic crystal slow waveguide is given, where k is the wave vector, a is the lattice constant of the near-infrared broadband photonic crystal slow waveguide, n=1 is the refractive index of the air cladding of the near-infrared broadband photonic crystal slow waveguide, ω is the angular frequency, and c is the speed of light in vacuum.

[0047] Figure 5 The graph shows the group refractive index, absorbance of different gases, and emission spectrum of a near-infrared broadband photonic crystal slow waveguide as a function of wavelength.

[0048] Figure 6 A flowchart illustrating the measurement of gases using this invention.

[0049] The attached figures are labeled as follows:

[0050] 100. Near-infrared narrow-linewidth detector laser; 101. Near-infrared tunable pump laser module; 102. Fiber coupler; 103. On-chip Mach-Zehnder interferometer; 104. Fiber filter; 105. Fiber beam splitter; 106. Signal processing module; 107. Low-pass filter module; 108. Phase adjustment module;

[0051] 01. Near-infrared broadband photonic crystal slow waveguide; 02. Input waveguide; 03. Output waveguide; 04. First beam splitter waveguide; 05. Beam combiner waveguide; 06. First single-mode waveguide; 07. Metal electrode; 08. Second beam splitter waveguide; 09. Second single-mode waveguide; 10. First multimode waveguide; 11. Second multimode waveguide. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0053] This embodiment provides an on-chip multi-component gas sensing system, such as Figure 1 As shown, it includes:

[0054] Near-infrared narrow-linewidth detection laser 100, near-infrared tunable pump laser module 101; fiber coupler 102, on-chip Mach-Zehnder interferometer 103, fiber filter 104, fiber beam splitter 105, signal processing module 106, low-pass filter module 107, phase adjustment module 108.

[0055] Specifically, the output of the near-infrared narrow linewidth detection laser 100 is connected to one input of the fiber optic coupler 102 to generate a near-infrared detection laser with a wavelength of 1550nm and a linewidth of 25KHz. After being coupled into the on-chip Mach-Zehnder interferometer 103 through the fiber optic coupler 102, it generates a photothermal interference signal.

[0056] The near-infrared tunable pumped laser module 101 includes a near-infrared tunable laser, an acousto-optic modulator, a signal generator, and a polarization controller.

[0057] The near-infrared tunable laser is used to generate near-infrared pump lasers that can be absorbed by gas, with a wavelength tuning range of 1500-1700nm.

[0058] The acousto-optic modulator has an optical fiber input, an optical fiber output, and a voltage input. The optical fiber input of the acousto-optic modulator is connected to the output of a near-infrared tunable laser, the optical fiber output of the acousto-optic modulator is connected to the input of a polarization controller, and the voltage input of the acousto-optic modulator is connected to the output of a signal generator, for the purpose of intensity modulation of the near-infrared pump laser.

[0059] The output terminal of the signal generator is connected to the voltage input terminal of the acousto-optic modulator to generate a high-frequency square wave modulation signal.

[0060] The input end of the polarization controller is connected to the optical fiber output end of the acousto-optic modulator. The output end of the polarization controller serves as the output end of the near-infrared tunable pump laser module 101. The output end of the polarization controller is connected to the input end of the optical fiber coupler 102 to control the polarization state of the near-infrared pump laser.

[0061] The fiber coupler 102 has two input terminals and one output terminal. The output terminal of the near-infrared pump laser module 101 is connected to one input terminal of the fiber coupler 102. The output terminal of the near-infrared narrow linewidth probe laser 100 is connected to the other input terminal of the fiber coupler 102. The output terminal of the fiber coupler 102 is connected to the input terminal of the on-chip Mach-Zehnder interferometer 103, which is used to simultaneously couple the near-infrared probe laser output from the near-infrared probe laser and the near-infrared pump laser output from the near-infrared tunable pump laser module 101 into the on-chip Mach-Zehnder interferometer 103.

[0062] like Figure 3 The image shows a top view of the structure of an on-chip Mach-Zehnder interferometer 103. The on-chip Mach-Zehnder interferometer 103 includes a near-infrared broadband photonic crystal slow light waveguide 01, an input waveguide 02, an output waveguide 03, a first beam splitter waveguide 04, a second beam splitter waveguide 08, a beam combiner waveguide 05, a first multimode waveguide 10, a second multimode waveguide 11, a first single-mode waveguide 06, a second single-mode waveguide 09, and a metal electrode 07.

[0063] Figure 2 The diagram shows the structure of a near-infrared broadband photonic crystal slow waveguide. After optimization, the radius of the large aperture is R = 0.35a, the radius of the central aperture is r0 = 0.6R, the radius of the center of the first row of small apertures adjacent to the central aperture is r1 = 0.7R, and the distance between the centers of the first row of small apertures on both sides of the central aperture is W1 = ×a, the distance between the centers of the second row of small holes on both sides of the central hole is W2.1 = 2.1. ×a, lattice constant a = 530 nm.

[0064] One arm of the on-chip Mach-Zehnder interferometer 103 has a near-infrared broadband photonic crystal slow waveguide 01, and the other arm has a first single-mode waveguide 06, which is used to realize the interference of near-infrared detection laser.

[0065] The input waveguide 02 serves as the input terminal of the on-chip Mach-Zehnder interferometer 103 and is connected to the output terminal of the fiber coupler 102 for coupling the input near-infrared detection laser and the near-infrared pump laser; the output waveguide 03 serves as the output terminal of the on-chip Mach-Zehnder interferometer 103 and is connected to the input terminal of the fiber filter 104 for coupling the output near-infrared detection laser and the near-infrared pump laser.

[0066] The first beam splitter waveguide 04 is used for beam splitting, and the beam combiner waveguide 05 is used for beam combining.

[0067] The first single-mode waveguide 06 can simultaneously conduct near-infrared detection laser and near-infrared pump laser.

[0068] The second beam splitter waveguide 08, the second single-mode waveguide 09, and the first multimode waveguide 10 together constitute a mode converter, which is used to convert the fundamental mode of the second beam splitter waveguide 08 into a higher-order mode of the first multimode waveguide. The first multimode waveguide 10 contains both a fundamental mode and a higher-order mode. The fundamental mode is used to excite the even mode of the near-infrared broadband photonic crystal slow waveguide 01, and the higher-order mode is used to excite the odd mode of the near-infrared broadband photonic crystal slow waveguide 01.

[0069] The second multimode waveguide 11 is connected to the beam combiner waveguide 05 and is used to output the mode of the near-infrared broadband photonic crystal slow waveguide 01.

[0070] The substrates of the input waveguide, output waveguide, first beam splitter waveguide, first single-mode waveguide, second beam splitter waveguide, second single-mode waveguide, first multimode waveguide, second multimode waveguide, and beam combiner waveguide are silicon, the core layer is silicon, the lower cladding is silicon dioxide, and the upper cladding is air.

[0071] The metal electrode 07 is located on top silicon and three micrometers away from the first single-mode waveguide 06, and is used to adjust the effective refractive index of the first single-mode waveguide 06.

[0072] See Figure 4 The figure shows the dispersion diagram of the near-infrared broadband photonic crystal slow waveguide of the present invention, where k is the wave vector, a is the lattice constant of the near-infrared broadband photonic crystal slow waveguide, n=1 is the refractive index of the cladding of the near-infrared broadband photonic crystal slow waveguide, ω is the angular frequency, and c is the speed of light in vacuum. Eight modes appear in the band gap, and these eight modes can be used to guide near-infrared pump light of different wavelengths and near-infrared probe light with a wavelength of 1550nm.

[0073] The near-infrared broadband photonic crystal slow waveguide 01 has three rows of defective holes. By optimizing the size of the three rows of defective holes in the center, when the radius of the large non-defective hole R = 0.35a, the radius of the central hole r0 = 0.6R, and the radius of the center of the first row of small holes on both sides of the central hole r1 = 0.7R, the waveguide generates eight modes. By optimizing the distance between the three rows of defective holes, the distribution of the waveguide's dielectric constant changes, causing the wavelength spacing of the eight modes to change accordingly. When the distance W1 between the centers of the first row of small holes on both sides of the central hole... ×a, the distance between the centers of the second row of small holes on both sides of the central hole is W2.1 = 2.1. When the lattice constant a = 530 nm, the eight modes do not overlap and are uniformly distributed at the absorption wavelengths of gases such as NH3, C2H2, CO2, H2S, and CH4. (See...) Figure 5 .

[0074] The near-infrared broadband photonic crystal slow waveguide 01 serves as one arm of the on-chip Mach-Zehnder interferometer 103, and can simultaneously conduct near-infrared probe lasers and near-infrared pump lasers, exhibiting a slow light effect in the 1500-1700 nm range. The near-infrared broadband photonic crystal slow waveguide 01 has a suspended aperture structure, with a silicon substrate, a silicon core layer, an air lower cladding, an air upper cladding, and a silicon dioxide support layer.

[0075] The input end of the fiber optic filter 104 is connected to the output end of the on-chip Mach-Zehnder interferometer 103, and the output end of the fiber optic filter 104 is connected to the input end of the fiber optic beam splitter 105, which is used to conduct near-infrared detection laser and filter out near-infrared pump laser; one output end of the fiber optic beam splitter 105 is connected to the signal processing module 106, and the other output end is connected to the low-pass filter module 107, which is used to split the near-infrared detection laser into two paths.

[0076] The low-pass filter module 107 includes a first near-infrared detector and a low-pass filter; the output of the low-pass filter is connected to the input of the phase adjustment module 108 as the output of the low-pass filter module 107.

[0077] The first near-infrared detector is used to detect the interference signal of the near-infrared detection laser and realize photoelectric conversion.

[0078] The low-pass filter has a cutoff frequency of 10Hz and is used to generate the feedback signal for the phase adjustment module.

[0079] The signal processing module 106 includes a second near-infrared detector, a lock-in amplifier, and a data acquisition unit. The input terminal of the second near-infrared detector serves as the input terminal of the signal processing module 106. The output terminal of the second near-infrared detector is connected to the input terminal of the lock-in amplifier, and the output terminal of the lock-in amplifier is connected to the input terminal of the data acquisition unit.

[0080] The second near-infrared detector is used to detect the interference signal of the near-infrared detection laser and realize photoelectric conversion.

[0081] The lock-in amplifier is used to realize the first harmonic signal of the interference signal.

[0082] The data acquisition unit is used to acquire the output signal of the lock-in amplifier.

[0083] The phase adjustment module 108 includes a current source and a probe station. The positive output terminal of the current source is connected to one input terminal of the probe station, and the negative output terminal of the current source is connected to the other input terminal of the probe station. The probe station has two output terminals, which are respectively connected to two pads of the metal electrode.

[0084] The current source is used to generate a current signal.

[0085] The probe station is used to transmit the current signal generated by the current source to the metal electrode.

[0086] The input terminal of the phase adjustment module 108 is connected to the output terminal of the low-pass filter module 107, and is used to adjust the phase of the near-infrared detection laser in the first single-mode waveguide 06 so that the phase difference between the two arms of the on-chip Mach-Zehnder interferometer 103 is stabilized at 90°.

[0087] The fabrication method of the on-chip Mach-Zehnder interferometer is as follows:

[0088] Step 1: A photoresist mask is formed using electron beam exposure. Near-infrared broadband photonic crystal slow waveguide, input waveguide, output waveguide, first beam splitter waveguide, second beam splitter waveguide, beam combiner waveguide, first multimode waveguide, second multimode waveguide, first single-mode waveguide, and second single-mode waveguide with silicon dioxide as the cladding layer are prepared by dry etching. The photoresist is then removed using a photoresist remover.

[0089] Step 2: Fabricate metal electrodes. Use ultraviolet exposure to form a photoresist mask on top of the silicon layer in the metal electrode area. Use thermal evaporation to fabricate metal electrodes. Remove the photoresist using a stripper solution.

[0090] Step 3: Etching silicon dioxide. A photoresist mask is formed in the slow waveguide region of the near-infrared broadband photonic crystal using ultraviolet exposure. Hydrofluoric acid is used to etch the silicon dioxide under the slow waveguide of the near-infrared broadband photonic crystal to form an air bridge structure. The photoresist is removed by stripping solution, and finally all the structures of the on-chip Mach-Zehnder interferometer are formed.

[0091] A multi-component gas detection device includes a photothermal interference spectroscopy multi-component gas sensing system.

[0092] Figure 6 A flowchart illustrating the gas measurement process using this invention. Detailed description:

[0093] Step 1: Adjust the emission wavelength of the near-infrared tunable laser so that the pump light wavelength is aligned with the absorption peak of the gas to be measured, and adjust the signal generator to achieve intensity modulation of the near-infrared pump laser.

[0094] Step 2: The near-infrared probe laser output from the near-infrared narrow linewidth probe laser and the near-infrared pump light output from the near-infrared tunable pump laser module are coupled into the input of the on-chip Mach-Zehnder interferometer via an optical fiber coupler.

[0095] Step 3: Adjust the fiber optic filter and beam splitter to enable the near-infrared detection laser to conduct through the low-pass filter module and signal processing module, while disabling the near-infrared pump laser;

[0096] Step 4: Based on the signal output by the low-pass filter module, adjust the phase adjustment module to stabilize the phase difference between the two arms of the on-chip Mach-Zehnder interferometer at 90°.

[0097] Step 5: Record the output signal of the second near-infrared detector in real time, and demodulate the photothermal interference signal using a lock-in amplifier;

[0098] Step 6: Analyze the detection performance of the device based on the photothermal interference signals measured at different gas concentrations.

[0099] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the spirit and scope of the technical solution of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. An on-chip multi-component gas sensing system, characterized in that: It includes a near-infrared narrow-linewidth detector laser, a near-infrared tunable pump laser module, an on-chip Mach-Zehnder interferometer, fiber couplers, fiber beam splitters, fiber filters, low-pass filter modules, phase adjustment modules, and signal processing modules; The output of the near-infrared narrow linewidth probe laser is connected to one input of the fiber coupler, and the output of the near-infrared tunable pump laser module is connected to the other input of the fiber coupler. The output of the fiber optic coupler is connected to the input of the on-chip Mach-Zehnder interferometer; The input of the fiber optic filter is connected to the output of the on-chip Mach-Zehnder interferometer; The output of the fiber optic filter is connected to the input of the fiber optic beam splitter. One output of the fiber optic beam splitter is connected to the signal processing module, and the other is connected to the low-pass filter module. The output of the low-pass filter module is connected to the input of the phase adjustment module; One arm of the on-chip Mach-Zehnder interferometer has a near-infrared broadband photonic crystal slow waveguide, and the other arm has a first single-mode waveguide, which is used to realize the interference of near-infrared detection laser; The near-infrared broadband photonic crystal slow waveguide has three rows of defective apertures. By optimizing the size of the three rows of defective apertures in the center, when the radius of the large non-defective aperture R = 0.35a, the radius of the central aperture r0 = 0.6R, and the radius of the center of the first row of small apertures adjacent to the central aperture r1 = 0.7R, the waveguide generates eight modes. By optimizing the distance between the three rows of defective apertures, the distribution of the waveguide's dielectric constant changes, resulting in a change in the wavelength spacing of the eight modes. When the distance W1 between the centers of the first row of small apertures on both sides of the central aperture... ×a, the distance between the centers of the second row of small holes on both sides of the central hole is W2.1 = 2.

1. When the lattice constant a = 530 nm, the eight modes do not overlap and can be uniformly distributed at the absorption wavelengths of NH3, C2H2, CO2, H2S, and CH4 gases.

2. The on-chip multi-component gas sensing system according to claim 1, characterized in that: The near-infrared tunable pumped laser module includes a near-infrared tunable laser, an acousto-optic modulator, a signal generator, and a polarization controller. The acousto-optic modulator has an optical fiber input, an optical fiber output, and a voltage input. The optical fiber input of the acousto-optic modulator is connected to the output of the near-infrared tunable laser, the optical fiber output of the acousto-optic modulator is connected to the input of the polarization controller, and the voltage input of the acousto-optic modulator is connected to the output of the signal generator. The near-infrared tunable laser generates near-infrared pumped laser light that is absorbed by the gas, with a wavelength tuning range of 1500-1700 nanometers.

3. The on-chip multi-component gas sensing system according to claim 2, characterized in that: The on-chip Mach-Zehnder interferometer includes a near-infrared broadband photonic crystal slow waveguide, an input waveguide, an output waveguide, a first beam splitter waveguide, a second beam splitter waveguide, a beam combiner waveguide, a first multimode waveguide, a second multimode waveguide, a first single-mode waveguide, a second single-mode waveguide, and metal electrodes. The input waveguide serves as the input terminal of the on-chip Mach-Zehnder interferometer, used for coupling the input near-infrared detection laser and the near-infrared pump laser; the output waveguide serves as the output terminal of the on-chip Mach-Zehnder interferometer, used for coupling the output near-infrared detection laser and the near-infrared pump laser. The first beam splitter waveguide is used for beam splitting, and the beam combiner waveguide is used for beam combining; the first single-mode waveguide can simultaneously conduct near-infrared probe laser and near-infrared pump laser. The second beam splitter waveguide, the second single-mode waveguide, and the first multimode waveguide together constitute a mode converter, which is used to convert the fundamental mode of the second beam splitter waveguide into a higher-order mode of the first multimode waveguide. The first multimode waveguide contains both a fundamental mode and a higher-order mode. The fundamental mode is used to excite the even mode of the near-infrared broadband photonic crystal slow waveguide, and the higher-order mode is used to excite the odd mode of the near-infrared broadband photonic crystal slow waveguide. The second multimode waveguide is connected to the beam combiner waveguide and is used to output the mode of the near-infrared broadband photonic crystal slow waveguide; The metal electrode is located on top silicon and three micrometers away from the first single-mode waveguide, and is used to adjust the effective refractive index of the first single-mode waveguide. The substrates of the input waveguide, output waveguide, first beam splitter waveguide, first single-mode waveguide, second beam splitter waveguide, second single-mode waveguide, first multimode waveguide, second multimode waveguide, and beam combiner waveguide are silicon, the core layer is silicon, the lower cladding is silicon dioxide, and the upper cladding is air.

4. The on-chip multi-component gas sensing system according to claim 3, characterized in that: The near-infrared broadband photonic crystal slow waveguide simultaneously conducts near-infrared probe lasers and near-infrared pump lasers. The near-infrared broadband photonic crystal slow waveguide has three rows of defect holes and eight modes, exhibiting a slow light effect in the 1500-1700 nm wavelength range. The eight modes cover multiple gas absorption bands in the 1500-1700 nm wavelength range. The near-infrared broadband photonic crystal slow waveguide is a suspended air bridge structure with a silicon substrate, a silicon core layer, an air lower cladding, an air upper cladding, and a silicon dioxide support layer.

5. The on-chip multi-component gas sensing system according to claim 4, characterized in that: The phase adjustment module includes a current source and a probe station. The positive output terminal of the current source is connected to one input terminal of the probe station, and the negative output terminal of the current source is connected to the other input terminal of the probe station. The probe station has two output terminals, which are respectively connected to two pads of the metal electrode.

6. The on-chip multi-component gas sensing system according to claim 5, characterized in that: The fabrication method of the on-chip Mach-Zehnder interferometer is as follows: Step 1: A photoresist mask is formed using electron beam exposure. Near-infrared broadband photonic crystal slow waveguide, input waveguide, output waveguide, first beam splitter waveguide, second beam splitter waveguide, beam combiner waveguide, first multimode waveguide, second multimode waveguide, first single-mode waveguide, and second single-mode waveguide with silicon dioxide as the cladding layer are prepared by dry etching. The photoresist is then removed using a photoresist remover. Step 2: Fabricate metal electrodes. Use ultraviolet exposure to form a photoresist mask on top of the silicon layer in the metal electrode area. Use thermal evaporation to fabricate metal electrodes. Remove the photoresist using a stripper solution. Step 3: Etching silicon dioxide. A photoresist mask is formed in the slow waveguide region of the near-infrared broadband photonic crystal using ultraviolet exposure. Hydrofluoric acid is used to etch the silicon dioxide under the slow waveguide of the near-infrared broadband photonic crystal to form an air bridge structure. The photoresist is removed by stripping solution, and finally all the structures of the on-chip Mach-Zehnder interferometer are formed.

7. A multi-component gas detection device, characterized in that: It includes the on-chip multi-component gas sensing system according to any one of claims 1-6.

8. The detection method of an on-chip multi-component gas sensing system as described in any one of claims 1-6, characterized in that: include: Step 1: Adjust the emission wavelength of the near-infrared tunable laser so that the pump light wavelength is aligned with the absorption peak of the gas to be measured, and adjust the signal generator to achieve intensity modulation of the near-infrared pump laser. Step 2: The near-infrared probe laser output from the near-infrared narrow linewidth probe laser and the near-infrared pump light output from the near-infrared tunable pump laser module are coupled into the input of the on-chip Mach-Zehnder interferometer via an optical fiber coupler. Step 3: Adjust the fiber optic filter and beam splitter to enable the near-infrared detection laser to conduct through the low-pass filter module and signal processing module, while disabling the near-infrared pump laser; Step 4: Based on the signal output by the low-pass filter module, adjust the phase adjustment module to stabilize the phase difference between the two arms of the on-chip Mach-Zehnder interferometer at 90°. Step 5: Record the output signal of the second near-infrared detector in real time, and demodulate the photothermal interference signal using a lock-in amplifier; Step 6: Analyze the detection performance of the device based on the photothermal interference signals measured at different gas concentrations.

9. The detection method of an on-chip multi-component gas sensing system according to claim 8, characterized in that: The near-infrared broadband photonic crystal slow waveguide of the on-chip Mach-Zehnder interferometer exhibits a slow light effect in the 1500-1700 nm range.

10. The detection method of an on-chip multi-component gas sensing system according to claim 9, characterized in that: Near-infrared broadband photonic crystal slow waveguide generates eight modes, forming a near-infrared broadband photonic crystal slow waveguide. The eight modes cover multiple gas absorption bands in the wavelength range of 1500-1700 nanometers.

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