Multi-dimensional detection multi-species gas infrared sensing chip
By integrating an on-chip broadband light source and a micro-ring resonant cavity array, the problems of large size, high cost, and difficulty in resolving multiple groups of traditional mid-infrared gas sensors are solved, achieving high reliability and stability in the detection of multi-component gases.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2026-05-28
- Publication Date
- 2026-07-21
AI Technical Summary
Traditional mid-infrared gas sensors are large in size, expensive, and have poor stability. They also have difficulty distinguishing the absorption peaks of multi-component gases, resulting in redundant systems and low reliability.
By combining an on-chip broadband light source and a micro-ring resonant cavity array, multi-dimensional gas detection is achieved through the integration of a micro-ring sensing unit, an on-chip tunable filter, and an on-chip photodetector array. The light-gas interaction is enhanced by precisely aligning the wavelength of the micro-ring resonant peak with the gas absorption peak and matching the free spectral range.
It achieves high reliability and stability detection of multi-component gases, reduces system complexity, and improves sensor sensitivity and gas type identification capabilities.
Smart Images
Figure CN122430271A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optical sensing technology, specifically to an infrared sensing chip for multi-dimensional detection of various gases. Background Technology
[0002] In recent years, mid-infrared gas sensing technology has attracted much attention due to its inclusion of vibrational frequencies of most organic functional groups, and it can be applied in fields such as environmental monitoring, food safety, and healthcare. However, traditional detection equipment contains numerous precision displacement platforms and collimation optical paths, and its testing stability is often affected by the surrounding environment. Furthermore, it is expensive and lacks portability. With the gradual maturation of silicon-based optoelectronic technology, on-chip photonics technology provides a new approach and method for developing low-cost, portable infrared sensing chips. Integrating optical chips can significantly reduce the size, weight, and power consumption of traditional sensors. Moreover, since displacement platforms and optical path collimation are not required, system stability can be significantly improved. On-chip photonics technology also enables applications such as reduced system costs and intelligent operation.
[0003] However, traditional absorption waveguides are extremely long, which places very high demands on waveguide loss. More importantly, current technologies mainly rely on the correspondence between the spectrum of a narrowband laser and the absorption peaks of a single dimension in the molecular fingerprint region. This approach suffers from key problems such as difficulty in identifying the absorption peaks of interfering gases and the need for multiple laser sources for multi-component measurements, resulting in system redundancy and low reliability. Summary of the Invention
[0004] To address the aforementioned key issues, this invention innovatively proposes a multi-dimensional detection mid-infrared gas sensing chip. It proposes a novel method combining on-chip broadband light source and micro-ring resonant cavity array with multi-dimensional parameters, which can effectively solve key problems in mid-infrared gas sensing such as large volume, difficulty in identifying absorption peaks of interfering gases, and the need for multiple laser light sources for multi-component measurement.
[0005] The technical solution adopted in this invention is as follows: I. A multi-dimensional infrared sensor chip for detecting various gases The infrared sensing chip for various gases includes an on-chip broadband light source, a micro-ring sensing array, an on-chip tunable filter array, and an on-chip photodetector array. The micro-ring sensing array, the on-chip tunable filter array, and the on-chip photodetector array each have the same number of units, and each micro-ring sensing unit, on-chip tunable filter, and on-chip photodetector corresponds one-to-one. Three corresponding units form a sensing channel, and each sensing channel corresponds to a specific target gas.
[0006] In each sensing channel, the micro-ring sensing unit receives the mid-infrared light signal emitted by the on-chip broadband light source, forms a detection light signal, and couples it to the corresponding on-chip tunable filter. The on-chip tunable filter filters the detection light signal to generate a filtered light signal. The on-chip photodetector collects the filtered light signal and converts it into an electrical signal carrying the detection result of the corresponding target gas.
[0007] The resonant peak wavelength of the micro-ring sensing unit is aligned with the characteristic absorption peak wavelength of the target gas, and the free spectral range (FSR) matches the periodic spacing of the absorption spectral line clusters of the target gas. The on-chip tunable filter possesses spectral tunability.
[0008] The microring sensing unit adopts a chalcogenide glass groove waveguide microring structure. The waveguide material of the chalcogenide glass groove waveguide microring structure is chalcogenide glass material, and the waveguide structure is a groove waveguide microring structure. The central air groove of the groove waveguide microring structure is exposed to the ambient gas.
[0009] The on-chip broadband light source, micro-ring sensor array, on-chip tunable filter array, and on-chip photodetector array are integrated on the same chip using heterogeneous integration technology. The on-chip tunable filters are all made of chalcogenide glass. The on-chip broadband light source is optically coupled to the micro-ring sensor array through a power divider. The output terminal of the power divider corresponds one-to-one with the micro-ring sensor unit in the micro-ring sensor array, and each output terminal of the power divider is optically coupled to the input terminal of a corresponding micro-ring sensor unit.
[0010] The upper cladding of the micro-ring sensing unit is ambient gas, which exposes the central air slot of the slot waveguide micro-ring structure to the ambient gas.
[0011] The groove waveguide microring structure adopts a circular microring, and the chalcogenide glass material is As2Se3.
[0012] II. A gas detection method using an infrared sensor chip for multiple types of gases with multi-dimensional detection. The gas detection method includes the following steps: Step S1: Obtain the infrared absorption spectrum of each target gas and determine the center wavelength of the absorption peak of all target gases.
[0013] Step S2: Calculate the refractive index of the micro-ring sensing unit using the intrinsic mode finite difference method.
[0014] Step S3: Based on the center wavelength of the absorption peak of the target gas, combined with the pre-set resonance order, the effective refractive index of the micro-ring sensing unit, and the wavelength of the target resonance peak, calculate and determine the micro-ring radius of the micro-ring sensing unit.
[0015] In step S3, the center radius of the slot waveguide microring structure is determined by the microring resonance equation, so that the resonant peak wavelength, transmission intensity, free spectral range (FSR) of the microring sensing unit are matched with the infrared fingerprint absorption spectrum in the gas.
[0016] Step S4: Under the stated micro-ring radius, with the goal of optimizing the evanescent field fraction, calculate the waveguide width and slot width of the slot waveguide micro-ring structure using the intrinsic mode finite difference method.
[0017] Step S5: Determine the target filtering wavelength of the on-chip tunable filter based on the center wavelength of the absorption peak of the target gas, and then calculate the corresponding applied voltage based on the target filtering wavelength.
[0018] Step S6: Fabricate multiple types of gas infrared sensor chips and use the multiple types of gas infrared sensor chips to detect the concentration of each target gas in the ambient gas.
[0019] In step S6, for each sensing channel, the on-chip tunable filter generates an optical signal at the target filtering wavelength as a filtered optical signal. The on-chip photodetector collects the filtered optical signal and converts it into an electrical signal carrying the corresponding target gas detection result. The host computer obtains the light intensity of the target filtering wavelength from the electrical signal and then calculates the gas concentration using the Lambert-Beer law.
[0020] In step S6, the spectral tunability of the on-chip tunable filter is used to dynamically screen narrowband spectral signals at multiple target filtering wavelengths in the target gas absorption band.
[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a novel method for high-reliability on-chip sensing and detection of multi-component gases. By enhancing the light absorption effect through microring resonance and utilizing the multi-dimensional parameter mapping relationship between the microring resonance characteristics and the gas absorption spectrum, the reliability and stability of gas type identification and concentration detection are significantly improved. Simultaneously, on-chip fully integrated multi-component gas sensing, comprising an on-chip broadband light source, a microring sensing unit, and an on-chip photodetector, can be achieved without increasing system complexity.
[0022] 2. This invention uses chalcogenide glass as the waveguide layer material, and utilizes its extremely low loss characteristics in the mid-infrared band to ensure that the on-chip broadband light source can cover the fingerprint absorption area of various gases.
[0023] 3. This invention, by introducing a slotted waveguide structure, significantly increases the contact area between the mid-infrared light field and the gas to be measured inside the micro-ring sensing unit, thereby enhancing the light-gas interaction intensity. Compared to traditional strip waveguide micro-ring structures, this invention significantly improves the sensor's sensitivity.
[0024] 4. This invention utilizes the high refractive index difference between chalcogenide materials and silicon dioxide materials to significantly shorten the size of the micro-ring sensing unit, realize the large-scale integration of the micro-ring sensing unit array, and, together with the on-chip tunable filter, achieve parallel detection of multiple types of gases under monolithic integration. Attached Figure Description
[0025] Figure 1 This is a schematic diagram of the principle structure of an infrared sensing chip for multi-dimensional detection of various gases according to the present invention.
[0026] Figure 2 This is a schematic diagram of the transmission spectrum of a microring resonator.
[0027] Figure 3 This is a schematic diagram of a gas absorption spectrum.
[0028] Figure 4 This is the specific structure of the chalcogenide glass trench waveguide of the present invention.
[0029] Figure 5 The present invention describes the specific structure of the chalcogenide glass groove waveguide microring resonator.
[0030] Figure 6 This is a field distribution diagram of the slot waveguide of the present invention.
[0031] Figure 7 The transmission and reflection spectra of the microring resonator of the present invention are shown.
[0032] The components include: 1. On-chip broadband light source; 2. Micro-ring sensing unit; 3. On-chip tunable filter; 4. On-chip photodetector; 5. Chalcogenide glass trench waveguide; 6. Chalcogenide glass trench waveguide micro-ring; 7. Dielectric buried oxide layer; 8. Silicon substrate layer. Detailed Implementation
[0033] The present invention will be described in detail below with reference to specific implementation examples. These examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way.
[0034] This invention provides a mid-infrared sensing chip for multi-dimensional detection of multi-component gases. Leveraging the broad spectral characteristics of an on-chip integrated broadband light source, the chip covers the mid-infrared fingerprint absorption region of multi-component gases. Combined with the dynamic frequency selection capability of an on-chip tunable filter, selective synchronous detection of multi-component gases is achieved. A multi-dimensional feature matching relationship is established between the resonant spectral characteristics of the micro-ring sensing unit and the mid-infrared fingerprint absorption spectrum of the gas, providing a core sensing mechanism for the qualitative identification and quantitative demodulation of multi-component gases.
[0035] The multi-type gas sensing proposed in this invention refers to the use of multiple chalcogenide glass groove waveguide microrings to form high-density... QThis invention utilizes a resonator array, leveraging the high refractive index difference of chalcogenide materials in the mid-infrared band, to confine the light field within a nanoscale air groove region, thereby enhancing the interaction between light and gas. The core mechanism of this invention lies in spatial dimensional matching between the free spectral range (FSR) of the microring resonator and the periodic intervals of the absorption spectral line clusters of the target gas molecules. By precisely calculating and adjusting the physical structural parameters such as the radius, groove width, and waveguide width of each microring, the effective refractive index of the mode is controlled, enabling the resonance peaks of specific microrings in the array to achieve spectral coincidence and phase matching with the characteristic absorption lines of the target gas (such as carbon dioxide, methane, etc.). Each groove waveguide microring specifically maps the fingerprint spectrum of a particular gas molecule. When a mixed gas enters the groove region causing effective absorption loss, by monitoring the intensity attenuation or extinction ratio change of the resonance peak in the transmission spectrum of the corresponding microring, qualitative identification of the gas types in the complex mixture and quantitative real-time demodulation of gas concentration are achieved.
[0036] The multi-dimensional parameter combination proposed in this invention refers to using the center wavelength position of the microring resonance peak to correspond to the absorption peak wavelength of the gas, matching the free spectral range (FSR) with the interval of the fingerprint absorption spectral lines of various gases, and by real-time monitoring of the transmission intensity attenuation of the resonance peak under the gas absorption effect, combined with the high evanescent field fraction of the chalcogenide waveguide, the intensity change is converted into quantitative gas concentration information, thereby realizing the elimination of cross-induction of gases with similar properties, gas type identification, and concentration measurement.
[0037] This invention relates to an infrared sensing chip for various gases, comprising an on-chip broadband light source 1, a micro-ring sensing array, an on-chip tunable filter array, and an on-chip photodetector array. The micro-ring sensing array, the on-chip tunable filter array, and the on-chip photodetector array each have the same number of units, and the micro-ring sensing units 2, the on-chip tunable filter 3, and the on-chip photodetector 4 correspond one-to-one. These three corresponding units form a single-dimensional sensing channel, and each sensing channel corresponds to a target gas. The target gases for each sensing channel can be configured independently, and can be the same or different.
[0038] Among them, the micro-ring resonant unit of the micro-ring sensing array includes a straight waveguide and a ring waveguide, both of which are groove-type waveguide structures.
[0039] The on-chip photodetector 4 is located at the optical output end of its corresponding on-chip tunable filter 3. It is used to receive optical signals and convert them into electrical signals. The concentration of the corresponding target gas can be calculated by inverting the electrical signals.
[0040] The working principle of this invention is as follows: The sensor chip couples a mid-infrared broadband light signal from an on-chip broadband light source 1 to each micro-ring sensing unit 2. The light signal interacts with the target gas within the sensing unit, outputting a detection light signal carrying gas characteristic information. After being frequency-selectively filtered by an on-chip tunable filter 3, the signal is converted into an electrical signal by an on-chip photodetector 4. Based on the dual-dimensional signal demodulation of resonant peak wavelength and free spectral range (FSR) matching and light intensity attenuation, the qualitative identification of the target gas type and the quantitative detection of its concentration are realized respectively.
[0041] Specifically, in each sensing channel, after the micro-ring sensing unit 2 receives the mid-infrared light signal emitted by the on-chip broadband light source 1, the photons in the micro-ring sensing unit 2 interact with the target gas that may be contained in the ambient gas, forming a detection light signal and coupling it to the corresponding on-chip tunable filter 3. The on-chip tunable filter 3 filters the detection light signal to generate a filtered light signal. The on-chip photodetector 4 collects the filtered light signal and converts it into an electrical signal carrying the detection result of the corresponding target gas. For each sensing channel, the on-chip tunable filter 3 generates a light signal at the target filtering wavelength as the filtered light signal. The on-chip photodetector 4 collects the filtered light signal and converts it into an electrical signal carrying the detection result of the corresponding target gas. The host computer receives the electrical signal and obtains the light intensity of the target filtering wavelength from the electrical signal, and then calculates the gas concentration using the Lambert-Beer law.
[0042] Mid-infrared light signals are broadband light signals, meaning their wavelength range covers the absorption peaks of all target gases. The on-chip broadband light source 1 operates in the mid-infrared band, and its wavelength range covers the strong absorption fingerprint region of the multi-component gases to be measured in the mid-infrared band, providing a broadband light source signal to the sensing unit. Therefore, multiple narrowband lasers do not need to be connected in parallel when detecting multi-component gases, making the system scalable.
[0043] The output spectrum of the micro-ring sensing unit 2 possesses dual characteristics: resonant peak wavelength and free spectral range (FSR). Its transmission spectrum diagram is shown below. Figure 2 As shown, the micro-ring sensing unit 2 selectively enhances the resonance of specific wavelengths that meet the phase-matching condition, forming a characteristic transmission spectrum with a fixed resonance peak wavelength and a free spectral range (FSR). Simultaneously, the micro-ring resonant structure significantly enhances the interaction intensity between the mid-infrared light field and the gas, effectively reducing the physical size of the sensing unit while improving the absorption response. The mid-infrared absorption spectra of the target gas and the interfering gas are shown below. Figure 3As shown. Traditional sensing schemes often use single-wavelength narrowband lasers, corresponding to a single absorption peak of the target gas with only a single laser wavelength. However, adjacent absorption peaks of interfering gases often exist near the target absorption peak. This method places extremely high demands on the laser's linewidth and wavelength stability; even a slight wavelength shift can cause detection errors, leading to a significant decrease in system reliability and stability. This places extremely high demands on the laser and reduces the reliability and stability of the detection. To solve the above problems, this invention establishes a two-dimensional synchronous mapping relationship between the microring resonant transmission spectrum and the infrared absorption spectrum in the gas by precisely designing the microring structure parameters: Wavelength dimension mapping: precisely aligning the wavelength of the micro-ring resonance peak with the characteristic absorption peak wavelength of the target gas to achieve qualitative matching of gas types; Periodic dimension mapping: The free spectral range (FSR) of microrings is precisely matched with the periodic intervals of the target gas absorption spectral line clusters to form a unique correspondence of spectral line periodic characteristics.
[0044] By synchronously matching and detecting the resonant peak wavelength and FSR in two dimensions, the target gas and interfering gas can be distinguished from both wavelength position and spectral period, fundamentally suppressing cross-interference and ultimately achieving highly reliable and stable sensing and detection of gas type and concentration.
[0045] Preferably, the microring sensing unit 2 adopts a chalcogenide glass groove waveguide microring structure. The waveguide material of the chalcogenide glass groove waveguide microring structure is chalcogenide glass material, and the waveguide structure adopts a groove waveguide microring structure. The central air groove of the groove waveguide microring structure is exposed to the ambient gas, and the interior is filled with ambient gas.
[0046] Groove waveguide microring structures refer to microring structures constructed using groove waveguides, such as... Figure 5 As shown, the micro-ring sensing unit 2 mainly consists of two parallel chalcogenide glass trough waveguides 5 and a chalcogenide glass trough waveguide micro-ring 6, with the chalcogenide glass trough waveguide micro-ring 6 disposed between the two chalcogenide glass trough waveguides 5.
[0047] like Figure 4 As shown, the slot waveguide structure consists of two high-refractive-index chalcogenide glass waveguides and a low-refractive-index nanogroove region sandwiched between them. Based on the continuity condition of Maxwell's equations at the dielectric boundary, when quasi-transverse magnetic (TM) or quasi-transverse electric (TE) mode components exist at the interface of the high-refractive-index difference medium, the discontinuity of the normal component of the optical field electric displacement vector causes a sudden change in the electric field intensity in the low-refractive-index slot region. This results in the optical field energy being strongly confined and enhanced within the nanoscale low-refractive-index slot space. This structure enables direct overlap between the gas under test and the high-intensity confined optical field. By utilizing a large proportion of the evanescent field to interact with gas molecules, the response sensitivity of the resonant cavity to changes in the ambient refractive index and absorption coefficient is significantly improved.
[0048] The slot waveguide structure significantly enhances the evanescent field fraction by introducing a nanoscale low-refractive-index region at the waveguide center. This allows the gas molecules to directly fill the slot region with the highest optical field intensity, thereby physically strengthening the interaction between the mid-infrared light field and the gas molecules. The evanescent field fraction... η Defined as: in, P y The component of the Poynting vector at the target wavelength in the propagation direction is determined by... P y By integrating the area of the cross section of the slot region, the effective light power flowing through the space can be accurately obtained. η The value directly characterizes the distribution of light field energy within the low-refractive-index slot. When η As the volume of light interacting with gas increases, the resonant cavity's ability to capture characteristic absorption signals from gas molecules is significantly enhanced. This energy confinement mechanism fundamentally strengthens the interaction intensity between light and gas within the microring, thereby achieving a substantial improvement in sensor sensitivity.
[0049] Preferably, the on-chip broadband light source 1, the micro-ring sensing array, the on-chip tunable filter array, and the on-chip photodetector array are integrated on the same chip using a heterogeneous integration process. The waveguide layers of the micro-ring sensing units 2 in the micro-ring sensing array and the on-chip tunable filter 3 in the on-chip photodetector array are both made of chalcogenide glass. The on-chip broadband light source 1 adopts a mid-infrared emitting structure based on III-V semiconductor materials, and the on-chip photodetector 4 adopts a mid-infrared absorption structure based on III-V semiconductor materials. The on-chip broadband light source 1 is optically coupled to the micro-ring sensing array through a power divider. The output of the power divider corresponds one-to-one with the micro-ring sensing units 2 in the micro-ring sensing array, and each output of the power divider is optically coupled to the input of its corresponding micro-ring sensing unit 2, thereby distributing the broadband mid-infrared light signal to multiple micro-ring array sensing channels.
[0050] Specifically, the chip consists of a silicon substrate layer 8, a buried oxide layer 7, a waveguide layer, and a top cladding layer from bottom to top. The micro-ring sensing array, on-chip tunable filter array, and on-chip photodetector array are all located on the waveguide layer. The top cladding layer of the micro-ring sensing unit 2 is ambient gas, exposing the central air slot of the slotted waveguide micro-ring structure to the ambient gas. Top cladding layers are also required above the on-chip broadband light source 1, on-chip tunable filter 3, and on-chip photodetector 4 to isolate environmental interference and ensure optical performance stability. The silicon substrate layer 8 is made of silicon, the buried oxide layer 7 is made of silicon dioxide, and the top cladding layer is made of silicon dioxide.
[0051] Preferably, the groove waveguide microring structure adopts a circular microring, and the chalcogenide glass material is As2Se3.
[0052] like Figure 5 As shown, the micro-ring sensing unit 2 is composed of a silicon substrate layer 8, a dielectric buried oxide layer 7, and a waveguide layer stacked from bottom to top. The waveguide layer is made of chalcogenide glass, which forms a high refractive index difference with the silicon dioxide dielectric buried oxide layer 7, generating a strong total internal reflection confinement effect at the interface, thereby confining the energy flow very compactly within the waveguide core layer. This high-contrast refractive index distribution not only effectively enhances the mode confinement capability but also significantly suppresses the bending radiation loss of the micro-ring structure under small radius conditions by deeply locking the light field propagation path, significantly shortening the bending radius of the micro-ring structure. This provides a structural basis for achieving a high quality factor in the resonant cavity, high chip integration, and compact arrangement of the micro-ring array.
[0053] In the micro-ring sensing unit 2, the micro-ring structure exhibits wavelength-selective resonance characteristics for the incident light wavelength. Through waveguide total internal reflection constraint and phase resonance conditions, it enhances resonance at specific wavelengths that satisfy phase matching, thereby forming characteristic resonance peaks in the output spectrum. Different wavelengths of resonant light correspond to different spatial physical resonance orders, and their resonance peak wavelengths... λ It follows the following resonance equation: In the formula, R The radius of the microring in microring sensing unit 2 is given. n eff The effective refractive index of the mode in the microring, m It is an integer resonant series.
[0054] When the phase change generated by the light field circulating once within the microring is an integer multiple of 2π, coherent constructive interference causes energy to accumulate rapidly within the cavity. By adjusting the size of the microring, the optical path length of the light field can be changed. Combined with the effective refractive index of the mode, the resonant peak position can be precisely aligned with the absorption spectral line of the target gas, providing a physical basis for subsequent gas identification using intensity modulation.
[0055] quality factor of microrings Q The value is used to characterize the relative relationship between the accumulation of optical field energy and the attenuation of losses within the resonant cavity. From a physical mechanism perspective, Q The magnitude of the value directly determines the spectral line shape of the resonance peak; higher values result in higher spectral line shapes. Q A higher value means a sharper resonance peak, which can create a stronger optical field enhancement effect within the cavity and achieve a narrower resonance bandwidth. Q The value is defined as: In the formula, λ m For the first m Wavelength of the resonant peak. λ FWHMThe full width at half maximum (FWHM) of the transmission spectrum corresponding to this resonance order is given.
[0056] high Q The achievement of this value significantly enhances the number of light field cycles within the microring, enabling photons to interact with gas molecules filling the groove region at higher frequencies. This narrow bandwidth characteristic not only improves spectral resolution but also ensures the sensor has extremely high response sensitivity to the slight absorption losses caused by the gas, thereby effectively reducing the system's detection limit.
[0057] The sensing performance of the micro-ring sensing unit 2 is measured by its sensitivity. S i Quantitative characterization is performed to describe the response of the output port signal to fluctuations in the concentration of the analyte gas. Its sensitivity... S i It can be calculated using the following formula: In the formula, This represents the normalized change in light intensity at the output port of the slot waveguide microring at a specific resonant peak wavelength. This indicates the change in concentration of the characteristic gas corresponding to the microring resonance peak.
[0058] From a sensing mechanism perspective, this sensitivity depends on the degree of interaction between the high-intensity confined light field within the slot waveguide and the gas molecules being measured. When the gas concentration fluctuates within the nano-air slot region, the change in the cavity absorption coefficient directly modulates the transmission spectral depth of the resonant cavity, resulting in a light intensity attenuation proportional to the concentration change. Through this intensity modulation mechanism, the system can convert the weak fingerprint absorption signal of gas molecules into a quantifiable normalized light intensity change, thereby achieving highly sensitive quantitative measurement of the concentration of the target gas component.
[0059] To achieve accurate detection of multi-component gases, the on-chip tunable filter 3 located at the front end of the on-chip photodetector 4 has spectral tunability, which can dynamically filter narrowband spectral signals in the absorption band of the target gas, further eliminating the influence of interfering gases and suppressing spectral noise. Finally, the on-chip photodetector 4 completes the demodulation of the light intensity signal, and the gas type and concentration are obtained by combining wavelength frequency selection and light intensity attenuation characteristics, realizing multi-dimensional detection.
[0060] This invention also provides a gas detection method using a multi-dimensional infrared sensing chip for detecting multiple types of gases. In this method, a multi-parameter matching relationship is established between the resonant peak wavelength, transmission intensity, and free spectral range (FSR) of the micro-ring sensing unit 2 and the infrared fingerprint absorption spectrum of the gas. This is combined with the frequency selection characteristics of the on-chip tunable filter 3 and the signal demodulation capability of the on-chip photodetector 4 to form a complete multi-dimensional sensing mechanism. By adjusting the micro-ring parameters, each sensing channel independently corresponds to different gases, enabling parallel detection of multiple components. The specific process is as follows: The effective refractive index and group refractive index of the micro-ring sensing unit are calculated using the intrinsic mode finite difference method (FDE). The micro-ring radius is designed based on the micro-ring resonance equation, ensuring that the wavelength of the micro-ring resonant peak precisely coincides with the characteristic absorption peak wavelength of the target gas. Based on the target gas composition, multiple micro-ring sensing units with different structural parameters are integrated in parallel, ensuring that the resonant peak of each micro-ring matches the absorption peak of the corresponding gas component, achieving parallel and interference-free detection of multiple gas components. The gas type is determined by matching the wavelength of the resonance peak with the free spectral range. The gas concentration is calculated by using the Lambert-Beer law based on the attenuation of the output light intensity of the resonance peak. A wavelength-intensity dual-dimensional mapping relationship is constructed to complete multi-dimensional signal demodulation.
[0061] The method of the present invention specifically includes the following steps: Step S1: Obtain the infrared absorption spectrum of each target gas and determine the center wavelength of the absorption peak of all target gases.
[0062] Step S2: Calculate the refractive index of the micro-ring sensing unit 2 using the finite difference method (FDE) of intrinsic modes; the refractive index includes the effective refractive index. n eff Group refractive index n g .
[0063] Step S3: Based on the center wavelength of the absorption peak of the target gas, combined with the pre-set resonance order, the effective refractive index of the micro-ring sensing unit 2, and the target resonance peak wavelength, calculate and determine the micro-ring radius of the micro-ring sensing unit 2, i.e., the center radius of the slot waveguide micro-ring structure; the resonance order is in the integer order.
[0064] In this step, the center radius of the slot waveguide microring structure is determined using the microring resonance equation, enabling a multi-parameter matching relationship between the resonance peak wavelength, transmission intensity, free spectral range (FSR), and infrared fingerprint absorption spectrum in the gas of the microring sensing unit 2. Specifically, this includes: A quantitative correspondence between the microring structure parameters (radius, groove width, waveguide width) and refractive index was established, and the microring resonance equation was obtained. Based on the microring resonance equation, with the center wavelength of the absorption peak of the target gas as the resonance target, the corresponding microring radius is calculated and optimized. RThis allows the resonant peak wavelength of a single microring to precisely coincide with the absorption peak wavelength of a single target gas. Based on the Free Spectral Range (FSR) calculation formula, the radius and group refractive index of the microring are adjusted to match the FSR of the microring with the spectral line cluster spacing of the infrared fingerprint absorption spectrum in the gas, forming a two-dimensional mapping relationship of wavelength position and spectral line period. The target gas and the interfering gas can be distinguished from each other from the two dimensions of wavelength position and spectral line period.
[0065] Step S4: Under the micro-ring radius, with the goal of optimizing the evanescent field fraction, calculate the waveguide width and slot width of the slot waveguide micro-ring structure using the finite difference method of intrinsic modes (FDE).
[0066] Step S5: Determine the target filtering wavelength of the on-chip tunable filter 3 based on the center wavelength of the absorption peak of the target gas, and then calculate the corresponding loading voltage based on the target filtering wavelength.
[0067] Step S6: For a variety of different gases to be tested, repeat the parameter design process of steps S1 to S5, and prepare micro-ring sensing units 2 with different sizes, groove widths and waveguide widths respectively, and form micro-ring arrays, so that each micro-ring sensing unit 2 in the array independently corresponds to the characteristic absorption spectrum of a gas. Step S7: Fabricate infrared sensor chips for various types of gases and use these chips to detect the concentration of each target gas in the ambient gas.
[0068] In this step, the mid-infrared broadband light generated by the on-chip broadband light source 1 is synchronously coupled to the micro-ring sensing unit 2 via a power divider. After the light field interacts with the corresponding gas, it outputs a resonant spectrum carrying the component characteristics. After the spectrum is frequency-selectively filtered by the on-chip tunable filter and demodulated by the on-chip photodetector signal, the parallel crosstalk-free qualitative identification and quantitative detection of multi-component gases are completed.
[0069] Specific embodiments of the present invention are as follows: In this embodiment, the microring sensing array uses a grooved waveguide microring structure based on chalcogenide glass on insulator: its waveguide layer is chalcogenide glass (As2Se3) with a thickness of 1.4 μm and a refractive index of 2.822 at the center operating wavelength of 2.004 μm. Below the waveguide is a 2 μm thick buried oxide layer 7 of silicon dioxide (SiO2) with a refractive index of 1.45; the silicon substrate layer 8 is single-crystal silicon (Si); and the upper cladding is the gas environment to be measured.
[0070] The structural parameters of the microring sensing unit 2 were designed to detect the fingerprint absorption band of CO2 molecules. The total width of the slot waveguide was selected to be 1.10 μm, and the width of the central air slot was 200 nm to ensure a 51.5% evanescent field fraction in quasi-transverse (TE) mode. The radius of the microring in the microring sensing unit 2 was set to 18.59 μm, and the coupling distance between the straight waveguide and the microring resonant cavity was set to 200 nm. The width of the microring slot was 0.06 μm, and the width of the microring was 0.3 μm.
[0071] The resonant characteristics of the device were simulated and verified using the finite-difference time-domain algorithm. In this embodiment, the slot waveguide microring achieves an extinction ratio of approximately 22 dB for the target resonant order. Q The value reached 1.56 × 10 4 Sensitivity is 2×10 -8 ppm -1 .
[0072] Figure 6 The optical field distribution of the slot waveguide structure is shown. Figure 6 It can be seen that the vast majority of the light field is confined to the central slot region.
[0073] Figure 7 The transmission and reflection spectra of the slotted waveguide microring are shown. Figure 7 It can be seen that the transmission peak of the target microring precisely corresponds to the absorption peak of CO2 at 2004 nm.
[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A multi-dimensional infrared sensing chip for detecting multiple types of gases, characterized in that: The infrared sensing chip for various gases includes an on-chip broadband light source (1), a micro-ring sensing array, an on-chip tunable filter array, and an on-chip photodetector array; the micro-ring sensing array, the on-chip tunable filter array, and the on-chip photodetector array have the same number of units, and the micro-ring sensing unit (2), the on-chip tunable filter (3), and the on-chip photodetector (4) correspond one-to-one. The three corresponding units form a sensing channel, and each sensing channel corresponds to a target gas. In each sensing channel, the micro-ring sensing unit (2) receives the mid-infrared light signal emitted by the on-chip broadband light source (1), forms a detection light signal, and couples it to the corresponding on-chip tunable filter (3). The on-chip tunable filter (3) filters the detection light signal to generate a filtered light signal. The on-chip photodetector (4) collects the filtered light signal and converts it into an electrical signal carrying the detection result of the corresponding target gas.
2. The infrared sensing chip for multi-dimensional detection of various gases according to claim 1, characterized in that: The resonant peak wavelength of the micro-ring sensing unit (2) is aligned with the characteristic absorption peak wavelength of the target gas, and the free spectral range (FSR) matches the periodic interval of the absorption spectral line clusters of the target gas; the on-chip tunable filter (3) has spectral tunability.
3. The infrared sensing chip for multi-dimensional detection of various gases according to claim 1, characterized in that: The micro-ring sensing unit (2) adopts a chalcogenide glass groove waveguide micro-ring structure. The waveguide material of the chalcogenide glass groove waveguide micro-ring structure is chalcogenide glass material, and the waveguide structure adopts a groove waveguide micro-ring structure. The central air groove of the groove waveguide micro-ring structure is exposed to the ambient gas.
4. The infrared sensing chip for multi-dimensional detection of various gases according to claim 3, characterized in that: The on-chip broadband light source (1), micro-ring sensing array, on-chip tunable filter array and on-chip photodetector array are integrated on the same chip through heterogeneous integration process. The on-chip tunable filter (3) is made of chalcogenide glass material. The on-chip broadband light source (1) is optically coupled to the micro-ring sensing array through a power divider. The output terminal of the power divider corresponds one-to-one with the micro-ring sensing unit (2) in the micro-ring sensing array, and each output terminal of the power divider is optically coupled to the input terminal of a corresponding micro-ring sensing unit (2).
5. The infrared sensing chip for multi-dimensional detection of various gases according to claim 4, characterized in that: The upper cladding of the micro-ring sensing unit (2) is ambient gas, which exposes the central air slot of the slot waveguide micro-ring structure to the ambient gas.
6. The infrared sensing chip for multi-dimensional detection of various gases according to claim 3, characterized in that: The groove waveguide microring structure adopts a circular microring, and the chalcogenide glass material is As2Se3.
7. A gas detection method using an infrared sensing chip for multi-dimensional detection of multiple types of gases as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step S1: Obtain the infrared absorption spectrum of each target gas and determine the center wavelength of the absorption peak of all target gases; Step S2: Calculate the refractive index of the micro-ring sensing unit (2) using the intrinsic mode finite difference method; Step S3: Based on the center wavelength of the absorption peak of the target gas, combined with the pre-set resonance order, the effective refractive index of the micro-ring sensing unit (2) and the wavelength of the target resonance peak, calculate and determine the micro-ring radius of the micro-ring sensing unit (2); Step S4: Under the radius of the microring, with the goal of optimizing the evanescent field fraction, calculate the waveguide width and slot width of the slot waveguide microring structure using the intrinsic mode finite difference method; Step S5: Determine the target filtering wavelength of the on-chip tunable filter (3) based on the center wavelength of the absorption peak of the target gas, and then calculate the corresponding loading voltage based on the target filtering wavelength. Step S6: Fabricate multiple types of gas infrared sensor chips and use the multiple types of gas infrared sensor chips to detect the concentration of each target gas in the ambient gas.
8. The gas detection method according to claim 7, characterized in that: In step S3, the center radius of the slot waveguide microring structure is determined by the microring resonance equation, so that the resonant peak wavelength, transmission intensity, free spectral range FSR of the microring sensing unit (2) and the infrared fingerprint absorption spectrum in the gas form a multi-parameter matching relationship.
9. The gas detection method according to claim 7, characterized in that: In step S6, for each sensing channel, the on-chip tunable filter (3) generates an optical signal at the target filtering wavelength as a filtered optical signal. The on-chip photodetector (4) collects the filtered optical signal and converts it into an electrical signal carrying the corresponding target gas detection result. The host computer obtains the light intensity of the target filtering wavelength from the electrical signal and then calculates the gas concentration using the Lambert-Beer law.
10. The gas detection method according to claim 7, characterized in that: In step S6, the spectral tunability of the on-chip tunable filter (3) is used to dynamically screen narrowband spectral signals at multiple target filtering wavelengths of the target gas absorption band.