Topological photonic crystal ultra-sensitive gas sensor based on projection geometry regulation and detection method thereof

Abstract

The application discloses a kind of topological photonic crystal ultra-sensitive gas sensor based on projection geometry regulation and its detection method.The sensor includes topological photonic crystal sensing chip (including topological photonic crystal microcavity structure and gas channel), projection geometry regulation module, gas path module, light source module, spectrum detection module and signal processing and analysis module.Projection geometry regulation module is controlled by external field projection angle θ of topological photonic crystal microcavity=arctan (β_s / β_r), β_r²+β_s²=1, optimization sensor detection state;Target gas molecule is captured after specific adsorption layer and causes microcavity surface effective refractive index change and resonance frequency shift, signal processing module is quantitatively calculated according to spectrum change gas concentration;Topological stability criterion verifies detection reliability in real time.The application realizes ultra-high sensitivity (detection limit reaches ppb level), high selectivity and active regulation gas detection, and is suitable for environmental monitoring, industrial safety, respiratory gas analysis and food safety and the like scene.

Description

Technical Field

[0001] This invention relates to the fields of gas sensing technology and topological photonics, specifically to an ultrasensitive gas sensor based on projective geometry modulation of a topological photonic crystal and its detection method. This invention can be applied to environmental monitoring, industrial safety, toxic and harmful gas detection, respiratory gas analysis, food safety, and other fields, and is particularly suitable for applications requiring ultra-high sensitivity and selective gas detection. Background Technology

[0002] Gas sensors have wide applications in environmental monitoring, industrial safety, and medical diagnostics. However, existing gas sensor technology mainly suffers from the following problems: (a) Insufficient sensitivity Traditional gas sensors (such as electrochemical sensors and semiconductor sensors) have limited sensitivity when detecting trace gases, making it difficult to meet the requirements for ppb-level detection. (ii) Poor selectivity Existing sensors lack the ability to selectively identify specific components in mixed gases and are susceptible to interference from other gases. (iii) Slow response speed Some high-sensitivity sensors have long response recovery times, making it difficult to meet the needs of real-time monitoring. (iv) Topological photonic crystal gas sensors lack active control Existing topological photonic crystal sensors have a fixed structure and cannot be optimized for detection of different gases. To address the aforementioned problems, this invention provides a topological photonic crystal ultrasensitive gas sensor based on projection geometry control and its detection method. Summary of the Invention

[0003] (a) Purpose of the invention This invention aims to solve the technical problems of insufficient sensitivity, poor selectivity, slow response speed and lack of active control in existing gas sensors, and provides a topological photonic crystal ultrasensitive gas sensor based on projection geometry control and its detection method. (II) Technical Solution This invention provides a topological photonic crystal ultrasensitive gas sensor based on projection geometry control, characterized in that it comprises: A topological photonic crystal sensing chip, comprising a topological photonic crystal microcavity structure and a gas channel; A projection geometry control module is connected to the topological photonic crystal sensing chip and is used to control the projection angle of the topological photonic crystal microcavity through an external field; A gas path module, connected to the gas channel, is used to deliver the gas to be tested to the surface of the topological photonic crystal microcavity; A light source module is used to generate a probe light signal and couple it into the topological photonic crystal microcavity; A spectral detection module is connected to the output end of the topological photonic crystal microcavity for real-time detection of changes in transmission or reflection spectra. A signal processing and analysis module is connected to the spectral detection module for quantitatively detecting the concentration of the target gas based on spectral changes. Mathematical framework for projection geometry control: Definition of projection angle: θ = arctan(β_s / β_r), β_r² + β_s² = 1 Topological stability criterion: γθ˙2≥∣1−k∣∣∂C∂θ∣∣θ˙∣⋅h2γθ˙2≥∣1−k∣∂θ∂C∣θ˙∣⋅2h When the criterion is met, the gas detection is in a stable topological state, and the detection data is reliable. Detection principle: After target gas molecules are captured by the specific adsorption layer on the surface of the topological photonic crystal microcavity, the effective refractive index of the microcavity surface changes, leading to a shift in the resonant frequency. Projection geometry modulation optimizes the detection sensitivity by matching the absorption peaks of the target gas. (III) Beneficial Effects Ultra-high sensitivity: the detection limit can reach the ppb level; High selectivity: specific adsorption layer + optimized projection angle selectivity; Active control: Projection geometry control optimizes the detection status in real time; Topological stability criterion: Real-time verification of detection reliability. Attached Figure Description Figure 1 The overall structure diagram of the sensor shows the architectural relationship between the topological photonic crystal sensing chip, the projection geometry control module, the gas path module, the light source module, the spectral detection module, and the signal processing and analysis module. Figure 2 A schematic diagram of a topological photonic crystal microcavity structure, showing the layered structure of the topological photonic crystal resonant cavity, specific adsorption layer, gas channel, and coupling grating. Figure 3 Schematic diagram of gas sensing detection principle: Target gas molecule adsorption → Change in effective refractive index → ​​Shift in resonant frequency → Quantitative concentration detection process Figure 4 A schematic diagram of a multi-gas parallel detection architecture. This architecture features multiple microcavities, each configured with a different adsorption layer, and independently adjustable projection angles. Figure 5 Projection geometry control and stability criterion flowchart: a complete closed-loop process of projection angle configuration → detection and optimization → steady-state criterion → feedback adjustment. Terminology Explanation

[0004] Terminology Meaning Topological photonic crystals are photonic crystals with nontrivial topological band structures that support topologically protected electromagnetic modes. Microcavities, with dimensions on the micrometer scale, are optical resonant cavities used to enhance the interaction between light and matter. A specific adsorption layer is a material layer that selectively adsorbs specific gas molecules. The projection angle (θ) is a geometric parameter describing the projection direction in fiber bundle projection mapping, where θ = arctan(β_s / β_r). Projection geometry control is a technique for precisely controlling a physical system by configuring the projection angle θ. The quality factor (Q) is a parameter describing the energy storage capacity of an optical resonator. The higher the Q value, the sharper the resonance peak. The change in microcavity resonant frequency caused by target gas adsorption. Topological Chern number (C) describes a topological invariant that carries topological nontriviality. Limit of Detection (LOD): The lowest concentration of a target gas that a sensor can reliably detect. Detailed Implementation

[0005] Example 1: Ultrasensitive Single-Gas Detection Step 1: Fabrication of a topological photonic crystal sensing chip A topological photonic crystal microcavity was fabricated on a silicon-on-insulator (SOI) substrate using electron beam lithography and reactive ion etching. The topological photonic crystal has a lattice constant of 500 nm, an air hole radius of 150 nm, and an etching depth of 220 nm. A specific adsorption layer (such as ZIF-8 metal-organic framework material, 50 nm thick) was coated on the surface of the microcavity for selective adsorption of NO2 gas molecules. Step 2: Configure the projection geometry control module The projection geometry control module is connected to the control electrode of the microcavity, with an initial projection angle configured as θ = 0.45 rad and a quality factor Q ≈ 1.5 × 10⁻⁶. 5 The resonant wavelength λ_res≈1550nm. Step 3: Connect the gas circuit module The gas to be tested is delivered to the surface of the microcavity of the topological photonic crystal through a microfluidic channel, and the gas flow rate is controlled at 10-50 sccm to ensure sufficient contact between the gas molecules and the adsorption layer. Step 4: Perform spectral detection The probe light signal generated by the broadband light source (wavelength range 1500-1600nm) enters the topological photonic crystal microcavity through a coupling grating, and the transmission spectrum is acquired in real time by the spectral detection module (high-resolution spectrometer, resolution 0.01nm). The signal processing and analysis module quantitatively calculates the NO2 concentration based on the resonance peak shift. Step 5: Verify detection performance Calibration was performed by introducing standard NO2 gas of different concentrations. The sensor's detection limit reached 5 ppb, response time ≤ 8s, recovery time ≤ 15s, sensitivity 0.12nm / ppm, and linear correlation coefficient R² ≥ 0.999. Example 2: Optimizing Detection Performance by Adjusting Projection Angle Step 1: Initial detection state configuration The projection geometry control module was configured to an initial state of θ=0.30rad, and 10ppm of target gas was introduced. The resonant frequency shift and signal-to-noise ratio were recorded. Step 2: Scan and optimize the projection angle Within the range of θ = 0.10 rad to 0.80 rad, the projection angle is adjusted sequentially in steps of 0.02 rad, and the resonant frequency offset and signal-to-noise ratio at each projection angle are recorded to determine the optimal projection angle θ_opt. Step 3: Perform optimal projection angle detection The projection angle was fixed at θ_opt = 0.55 rad, and the target gas was introduced for detection. Under the optimal projection angle condition, the quality factor Q was improved to 2.0 × 10⁻⁶. 5 The resonance peak half-width at half-maximum is compressed to 0.015 nm, and the sensing sensitivity S(θ_opt) = 1.8 × S_max. Step 4: Verify the optimization effect After the projection angle adjustment was optimized, the signal-to-noise ratio was improved by 15dB in the initial state, the detection limit was reduced from 10ppb to 2ppb, and the response time was further shortened to 5s. Example 3: Adaptive Temperature Drift Compensation Step 1: Temperature monitoring configuration A temperature sensor is integrated on the topological photonic crystal sensing chip to monitor the chip's operating temperature in real time, with a sampling frequency of 100Hz. Step 2: Temperature-Refractive Index Relationship Calibration The resonant wavelength shift of blank samples was tested under different temperature conditions (20°C, 25°C, 30°C, 35°C, 40°C), and a temperature-resonant wavelength relationship model Δλ_T(T) was established. Step 3: Real-time compensation of projection angle The projection geometry control module calculates the required projection angle adjustment Δθ_T for temperature compensation based on real-time temperature monitoring values, and dynamically adjusts the microcavity projection angle to lock the resonant wavelength to the target value. Step 4: Verify the temperature compensation effect Within a temperature range of 20°C to 40°C, the compensated resonant wavelength drift is ≤0.005nm, the detection error is ≤2%, and it can work stably in a wide temperature range without the need for an external temperature control device. Example 4: Parallel Detection of Multiple Gases Step 1: Fabrication of a multi-microcavity array Four topological photonic crystal microcavities were fabricated on a single chip, arranged in a 1×4 array with a cavity spacing of 500 μm to avoid optical crosstalk. Step 2: Configure adsorption layers with different specificities The surfaces of the four microcavities are coated with different specific adsorption layers: - Microcavity 1: ZIF-8 (NO2 adsorption) - Microcavity 2: HKUST-1 (CO2 adsorption) - Microcavity 3: MIL-101 (VOCs adsorption) - Microcavity 4: MOF-199 (H2S adsorption) Step 3: Independent projection angle adjustment The projection geometry control module controls the projection angle of the four microcavities through independent control electrodes, and the projection angle of each microcavity is independently optimized to the optimal detection state of the corresponding target gas. Step 4: Parallel Spectral Detection The light source module couples the probe light signal to each microcavity in a time-division or simultaneous manner via a 1×4 optical switch, and the spectral detection module acquires the transmission spectrum of each microcavity sequentially or in parallel. The signal processing and analysis module calculates the concentrations of the four gases based on the resonant frequency offset of each microcavity. Step 5: Verify the multi-gas detection effect When tested in a mixed gas (containing 50ppb NO2, 500ppm CO2, 100ppb VOCs, and 30ppb H2S), the detection error of each channel is ≤5%, and the crosstalk between channels is ≤-30dB. Example 5: Humidity Interference Suppression Step 1: Humidity Impact Assessment The sensor's response to the target gas was tested under different relative humidity conditions (10%, 30%, 50%, 70%, 90% RH) to evaluate the detection error caused by humidity. Step 2: Establishing a humidity compensation model A humidity compensation mathematical model is established, in which the resonant frequency offset Δλ_RH caused by humidity is taken as a function of humidity H: Δλ_RH(H) = a·H² + b·H + c (where a, b, and c are calibration coefficients), and the humidity contribution is subtracted in signal processing. Step 3: Adaptive adjustment of projection angle and humidity The projection geometry control module dynamically adjusts the projection angle based on the real-time humidity detection value to compensate for the refractive index change caused by humidity, so that the sensor can maintain the optimal detection state under different humidity conditions. Step 4: Verify the humidity compensation effect Within the RH range of 10%-90%, the compensated detection error is reduced from ±25% to ±5%, and the sensor maintains high reliability over a wide humidity range. Example 6: Rapid Response and Real-time Monitoring Step 1: Configure Fast Response Mode The projection geometry control module configures the microcavity in a low quality factor, wide bandwidth mode (Q≈5×10). 4 (This involves sacrificing some sensitivity in exchange for a faster response speed.) Step 2: Continuous Real-Time Monitoring The gas path module continuously delivers the gas to be tested to the sensor chip at a constant flow rate, while the spectral detection module continuously acquires the transmission spectrum at a sampling rate of 100Hz. The signal processing module calculates the gas concentration in real time and outputs the result. Step 3: Alarm Threshold Setting The alarm threshold can be set according to the application scenario (e.g., triggering an alarm when the H2S concentration exceeds 10ppm), and the system will automatically judge and output an alarm signal. Step 4: Verify the real-time monitoring effect The sensor has a response time of ≤2s (10%-90% rise time) and a recovery time of ≤5s (90%-10% fall time) when the gas concentration changes abruptly, making it suitable for real-time monitoring scenarios in industrial safety. Example 7: Regeneration and Recycling of Specific Adsorption Layer Step 1: Design of Adsorption Layer Regeneration Mechanism The specific adsorption layer uses metal-organic framework (MOF) materials, which can be regenerated by desorbing the adsorbed gas molecules through heating or vacuum treatment. Step 2: Optimization of regeneration conditions Optimize the heating temperature (150°C), heating time (5 minutes), and vacuum degree (10⁻³Pa) to restore the adsorption capacity of the adsorption layer to more than 95% of the initial value after regeneration. Step 3: Cyclic Detection Test Perform 100 "adsorption-detection-regeneration" cycle tests and record the sensitivity, response time and recovery time for each cycle. Step 4: Verify cycle stability After 100 cycles, the sensor sensitivity retention rate is ≥90%, the response time increases by ≤2s, and the adsorption layer shows no obvious structural or performance degradation. Example 8: Miniaturization and Low-Power Integration Step 1: On-chip integrated light source An on-chip integrated DFB laser replaces the external broadband light source, and the tunable range of the laser wavelength covers the microcavity resonant wavelength (±5nm). Step 2: Photodetector integration InGaAs photodetectors and topological photonic crystal microcavities are integrated on the same chip to achieve on-chip detection of optical signals. Step 3: Low-power circuit design The projection geometry control module and signal processing module are designed using low-power CMOS technology, with an operating voltage of 3.3V and a typical power consumption of <50mW. Step 4: Verify the miniaturized integration effect The integrated sensor has a size of <5mm×5mm×1mm, a total weight of <1g, and a power consumption of <80mW. Its detection performance is comparable to that of large-size discrete systems (sensitivity retention rate ≥95%), making it suitable for portable and wearable gas detection devices.

Claims

1. A topological photonic crystal ultrasensitive gas sensor based on projection geometry control, characterized in that, The system includes: a topological photonic crystal sensing chip comprising a topological photonic crystal microcavity structure and a gas channel; a projection geometry control module connected to the topological photonic crystal sensing chip for controlling the projection angle of the topological photonic crystal microcavity via an external field; a gas path module connected to the gas channel for delivering the gas to be measured to the surface of the topological photonic crystal microcavity; a light source module for generating a probe light signal and coupling it into the topological photonic crystal microcavity; a spectral detection module connected to the output of the topological photonic crystal microcavity for real-time detection of changes in the transmission or reflection spectrum; and a signal processing and analysis module connected to the spectral detection module for quantitatively detecting the concentration of the target gas based on spectral changes.

2. The sensor according to claim 1, characterized in that: The topological photonic crystal microcavity includes a topological photonic crystal resonant cavity, a specific adsorption layer disposed on the surface of the resonant cavity, a gas channel communicating with the resonant cavity, and a coupling grating or waveguide structure for optical signal coupling; the specific adsorption layer is at least one of metal-organic framework material, molecularly imprinted polymer or functionalized self-assembled monolayer.

3. The sensor according to claim 1, characterized in that: The projection angle θ is defined as θ = arctan(β_s / β_r), where β_r and β_s satisfy the projection constraint β_r² + β_s² = 1. By adjusting the projection angle θ, the resonant cavity quality factor Q(θ) = Q_max·exp[-(θ-θ_Q)² / 2σ_Q²], the resonant wavelength λ_res(θ) = λ_0 + δλ(θ) and the sensing sensitivity S(θ) = S_max·exp[-(θ-θ_S)² / 2σ_S²].

4. The sensor according to claim 1, characterized in that: The relationship between the target gas concentration C and the resonant frequency offset Δλ is C = α·Δλ + β·(Δλ)² + γ·(Δλ)³, where α, β, and γ are calibration coefficients obtained through standard gas calibration.

5. The sensor according to claim 1, characterized in that: The sensor comprises multiple topological photonic crystal microcavities. Each microcavity surface is provided with an adsorption layer that specifically adsorbs different target gases. The projection angle of each microcavity is independently controlled by a projection geometry control module, enabling parallel detection of multiple gases with inter-channel crosstalk ≤ -30dB.

6. The sensor according to claim 1, characterized in that: The projection geometry control module dynamically adjusts the projection angle based on the real-time temperature monitoring value to compensate for the refractive index change caused by temperature, so that the resonant wavelength is locked to the target value. After compensation, the resonant wavelength drift is ≤0.005nm, and the detection error is ≤2% in the range of 20°C to 40°C.

7. The sensor according to claim 1, characterized in that: The projection geometry control module dynamically adjusts the projection angle based on the real-time humidity monitoring value to compensate for the resonant frequency shift caused by humidity, Δλ_RH(H)=a·H²+b·H+c. After compensation, the detection error is ≤5% in the range of 10%-90% relative humidity.

8. The sensor according to claim 1, characterized in that: During the gas detection process, the projection geometry control module continuously monitors the rate of change of the projection angle. According to the topological stability criterion γ· ² ≥ |1−k|·|∂C / ∂θ|·| |·h / 2 determines whether it is in a stable topological state. If the criterion is not met, a feedback adjustment is triggered to relock the sensor to a stable topological state.

9. The sensor according to claim 1, characterized in that: The sensor supports a fast response mode, and the microcavity quality factor Q is configured to be 5×10. 4 The response time is ≤2s, the recovery time is ≤5s; the sensor's detection limit is ≤5ppb, its sensitivity is ≥0.10nm / ppm, and its linear correlation coefficient R² is ≥0.

999.

10. A detection method for a topological photonic crystal ultrasensitive gas sensor based on projection geometry control, characterized in that, The process includes the following steps: (1) The projection angle of the topological photonic crystal microcavity is configured by the projection geometry control module to optimize the detection state of the sensor; (2) The gas path module delivers the gas to be tested to the surface of the topological photonic crystal microcavity, and the target gas molecules are captured by the specific adsorption layer; (3) The light source module generates a probe light signal and couples it into the topological photonic crystal microcavity; (4) The spectral detection module detects the changes in the transmission spectrum or reflection spectrum in real time and records the resonant frequency offset; (5) The signal processing and analysis module quantitatively detects the concentration of the target gas according to the spectral changes and compensates according to the real-time temperature and humidity; (6) The projection geometry control module continuously verifies the detection reliability according to the topological stability criterion, and triggers feedback adjustment when the criterion is not met.

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