An on-chip photoacoustic gas sensing device and method based on axial acoustic resonance enhancement
By setting a miniature gas cylinder with an axial first-order standing wave mode between the optical waveguide module and the photoacoustic detection module, and combining it with PMUT to enhance the photoacoustic signal, the acoustic enhancement problem of the on-chip photoacoustic sensing system is solved, and gas detection with high sensitivity and high integration is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANXI UNIV
- Filing Date
- 2026-05-06
- Publication Date
- 2026-07-03
AI Technical Summary
Existing on-chip photoacoustic sensing systems lack effective acoustic enhancement mechanisms, resulting in limited photoacoustic signal amplitude, decreased detection sensitivity, and difficulty in achieving high integration and miniaturization.
An on-chip photoacoustic gas sensing device based on axial acoustic resonance is adopted. By setting a miniature gas cylinder between the optical waveguide module and the photoacoustic detection module, and matching its axial dimension to half the wavelength of the acoustic wave of the photoacoustic detection module, an axial first-order standing wave mode is formed. Combined with a piezoelectric micromechanical ultrasonic transducer PMUT, on-chip readout and signal enhancement of photoacoustic signals are realized.
It achieves miniaturization and high integration of photoacoustic sensing devices, improves the sensitivity of gas detection and signal enhancement, and is suitable for the detection of various waveguide materials and target gases.
Smart Images
Figure CN122330264A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of photoacoustic sensing and integrated photonics technology, and specifically relates to an on-chip photoacoustic gas sensing device and method based on axial acoustic resonance enhancement. Background Technology
[0002] Photoacoustic spectroscopy is a highly sensitive gas sensing technology based on the absorption and modulation of light by gas molecules, followed by a non-radiative relaxation process to generate a periodic heat source, which further excites sound waves in the medium, enabling detection via an acoustic detector. Traditional photoacoustic sensing systems typically use a free-space beam of light to illuminate a gas volume, forming a volumetric sound-absorbing source within the gas region. The sound pressure signal is then amplified by a macroscopic acoustic resonant cavity, and finally read out through a microphone, quartz tuning fork, or other acoustic-electric transducers. Although this technology can achieve highly sensitive gas detection, its core enhancement mechanism relies on a centimeter-scale acoustic resonant cavity structure and a free-space optical path, resulting in a large system size, complex structure, and poor environmental stability, making it difficult to meet the development requirements of miniaturization and on-chip integration.
[0003] With the development of integrated photonics and micro / nano fabrication technologies, chip sensing technology based on evanescent field absorption in optical waveguides has gradually attracted attention. When light propagates in a waveguide, its mode field forms an evanescent field near the waveguide interface. External gas molecules can absorb this energy and generate a photothermal effect, thus forming a photoacoustic signal near the waveguide interface. Unlike the bulk sound source in traditional free-space photoacoustic systems, the photoacoustic source in this type of structure is closer to a surface sound source continuously distributed along the waveguide propagation direction.
[0004] However, in on-chip photoacoustic sensing structures, since the device scale is typically on the micrometer to millimeter scale, the distance between the photoacoustic source and the detector is significantly smaller than the wavelength of the sound wave. The system's acoustic response primarily exhibits local near-field coupling characteristics, rather than the far-field standing wave mode response found in traditional acoustic resonators. While this structure facilitates high integration, it also introduces new problems: the lack of an effective acoustic enhancement mechanism limits the amplitude of the photoacoustic signal; at higher frequencies, sound wave attenuation increases, reducing detection sensitivity; the acoustic signal generated by the distributed photoacoustic source lacks effective phase modulation and spatial coupling mechanisms during propagation, making synergistic enhancement difficult; and most existing on-chip structures rely solely on single near-field coupling detection, failing to fully utilize the spatial phase evolution characteristics along the sound wave propagation path. Summary of the Invention
[0005] To address the aforementioned problems, this invention provides an on-chip photoacoustic gas sensing device and method based on axial acoustic resonance enhancement.
[0006] To achieve the above objectives, the present invention employs the following technical solution: An on-chip photoacoustic gas sensing device based on axial acoustic resonance enhancement includes a substrate, a housing fixedly disposed on top of the substrate, an optical waveguide module disposed on the upper surface of the substrate, the optical waveguide module being used to propagate excitation light and form an evanescent field at the waveguide interface, the input end of the optical waveguide module being connected to one end of an optical input port, the other end of the optical input port being connected to the output end of a laser controller, the input end of the laser controller being connected to the output end of a computer, a photoacoustic detection module being disposed parallel above the optical waveguide module, a miniature gas cylinder being disposed between the photoacoustic detection module and the optical waveguide module, the top of the miniature gas cylinder being fixedly connected to the photoacoustic detection module, the bottom of the miniature gas cylinder being fixedly mounted on the substrate, a target gas being disposed inside the miniature gas cylinder, and the photoacoustic detection module being connected to a signal processing module through electrodes.
[0007] Furthermore, the substrate material is silicon dioxide or silicon.
[0008] Furthermore, a gas guiding channel is provided on the side wall of the miniature gas cylinder to replenish the miniature gas cylinder with the target gas.
[0009] Furthermore, the photoacoustic detection module is a piezoelectric micromechanical ultrasonic transducer (PMUT).
[0010] Furthermore, the axial dimension of the micro gas cylinder is matched with the operating frequency of the photoacoustic detection module.
[0011] Furthermore, the axial dimension of the micro gas cylinder is half the wavelength of the corresponding photoacoustic detection module, so that an axial first-order standing wave mode is formed in the cavity of the micro gas cylinder, and the photoacoustic detection module is located at the antinode of the sound pressure wave to obtain the maximum sound pressure response.
[0012] Furthermore, the signal processing module includes a preamplifier circuit, the output of which is connected to the input of a lock-in amplifier, and the output of which is connected to the input of a computer.
[0013] The on-chip photoacoustic gas sensing method based on axial acoustic resonance enhancement includes the following steps: S1: First, a suitable excitation light source is fed into the laser controller, and then the laser controller modulates it to the target frequency, which is half of the operating frequency of the photoacoustic detection module; S2: The modulated excitation light is coupled into the on-chip optical waveguide module through the optical input port, forming an evanescent field on the interface of the optical waveguide module and acting on the micro gas cylinder; S3: After the target gas is added to the micro gas cylinder, the target gas generates the corresponding photoacoustic signal by absorbing the evanescent field energy; S4: The photoacoustic signal propagates within the miniature gas cylinder and undergoes phase accumulation and spatial superposition during propagation, thereby creating an enhancement effect at a specific propagation distance. The sound wave forms a standing wave distribution during propagation and generates a maximum sound pressure value at the location of the photoacoustic detection module. S5: Utilizes a photoacoustic detection module to receive enhanced photoacoustic signals and converts them into corresponding electrical signals for output; S6: The signal processing module amplifies, locks in, demodulates, acquires, and inverts the electrical signal sequentially to obtain the target gas detection result.
[0014] Furthermore, the target gas in S3 is hydrogen, acetylene, water vapor, carbon monoxide, carbon dioxide, or methane.
[0015] Furthermore, the photoacoustic detection module in S4 operates in a high-order vibration mode, and the operating frequency is set to 204kHz.
[0016] Compared with the prior art, the present invention has the following advantages: This invention utilizes the interaction between the evanescent field in the on-chip optical waveguide and the target gas to directly form a photoacoustic source near the waveguide interface. This breaks through the traditional photoacoustic system's reliance on free space volume to absorb sound sources and optimizes the generation method of photoacoustic signals in principle. This invention is adaptable to various waveguide material systems and various target gas detection scenarios, and has good versatility and engineering application prospects; This invention achieves on-chip readout of photoacoustic signals by integrating a piezoelectric micromechanical ultrasonic transducer (PMUT) near the optical waveguide module. This avoids the volume redundancy and integration limitations caused by traditional macroscopic acoustic resonant cavities and external detectors, ultimately realizing the miniaturization and highly integrated design of the photoacoustic sensing device while ensuring high sensitivity in the detection process. This comprehensively improves the application performance and scenario adaptability of photoacoustic sensing technology. This invention sets up a miniature gas cylinder between the optical waveguide module and the photoacoustic detection module, matching the axial length of the miniature gas cylinder to half the wavelength of the sound wave from the corresponding photoacoustic detection module. This creates a stable axial acoustic standing wave mode within the miniature gas cylinder, thereby achieving spatial energy accumulation and enhancement of the sound pressure signal and effectively improving gas detection sensitivity. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the overall structure of the on-chip enhanced photoacoustic sensing device of the present invention; Figure 2 This is a diagram showing the sound pressure intensity distribution of the acoustic standing wave along the z-axis inside the miniature gas cylinder of the present invention. Figure 3Simulation diagram of the sound pressure distribution of the miniature gas cylinder at approximately 204 kHz when the axial dimension of the cylinder is set to half wavelength; Figure 4 This is the frequency response curve of the present invention at approximately 204 kHz; Figure 5 This is a graph of the photoacoustic signal of water vapor in the atmosphere measured at approximately 204 kHz according to the present invention.
[0018] In the figure, 1 is the substrate, 2 is the housing, 3 is the optical waveguide module, 4 is the optical input port, 5 is the laser controller, 6 is the computer, 7 is the photoacoustic detection module, 8 is the miniature gas cylinder, 9 is the electrode, 10 is the preamplifier circuit, and 11 is the lock-in amplifier. Detailed Implementation
[0019] To further illustrate the technical solution of the present invention, the present invention will be further described below through embodiments.
[0020] like Figures 1 to 5As shown, an on-chip photoacoustic gas sensing device and method based on axial acoustic resonance enhancement includes a substrate 1 made of silicon dioxide or silicon. A housing 2 is fixedly disposed on the upper surface of the substrate 1. An optical waveguide module 3 is disposed on the upper surface of the substrate 1. The optical waveguide module 3 includes an input waveguide section, a sensing waveguide section, and an output waveguide section. The sensing waveguide section adopts a straight waveguide, a bent waveguide, a helical waveguide, a folded waveguide, or a combination thereof. The optical waveguide module 3 is made of SU8, Si, SiO2, or SiN. The optical waveguide module 3 is used to propagate excitation light and form at the waveguide interface. In the evanescent field, the input end of the optical waveguide module 3 is connected to one end of the optical input port 4, and the other end of the optical input port 4 is connected to the output end of the laser controller 5. The input end of the laser controller 5 is connected to the output end of the computer 6. A photoacoustic detection module 7 is arranged parallel above the optical waveguide module 3. The photoacoustic detection module 7 is a piezoelectric micromechanical ultrasonic transducer (PMUT), which includes a diaphragm, a piezoelectric layer, an electrode layer, and a support layer. The photoacoustic detection module 7 operates in a high-order vibration mode, and the operating frequency is preferably set to 204 kHz. A micro gas cylinder 8 is arranged between the photoacoustic detection module 7 and the optical waveguide module 3. The axial dimension of the micro gas cylinder 8 matches the operating frequency of the photoacoustic detection module 7. The distance between the piezoelectric micromechanical ultrasonic transducer PMUT and the optical waveguide module 3 is between 400 μm and 1200 μm, preferably about 800 μm. The spacing of μm corresponds to half the wavelength of the corresponding sound wave, thus satisfying the standing wave resonance condition. Simultaneously, the axial dimension of the micro gas cylinder 8 is half the wavelength of the corresponding sound wave from the photoacoustic detection module 7, forming an axial first-order standing wave mode within the micro gas cylinder 8. The photoacoustic detection module 7 is positioned at the antinode of the sound pressure wave to obtain the maximum sound pressure response. The top of the micro gas cylinder 8 is fixedly connected to the photoacoustic detection module 7, and the bottom of the micro gas cylinder 8 is fixedly mounted on the substrate 1. A target gas, such as hydrogen, acetylene, water vapor, carbon monoxide, carbon dioxide, or methane, is disposed within the micro gas cylinder 8. A gas guiding channel is provided on the side wall of the miniature gas cylinder 8 to replenish the target gas into the miniature gas cylinder 8. The target gas can be guided into the miniature gas cylinder 8 through a mass flow controller or a microfluidic channel. The photoacoustic detection module 7 is connected to the signal processing module through the electrode 9. The signal processing module includes a preamplifier circuit 10. The output of the preamplifier circuit 10 is connected to the input of the lock-in amplifier 11. The output of the lock-in amplifier 11 is connected to the input of the computer 6. A calibration curve between the target gas concentration and the demodulated signal amplitude is established to achieve quantitative detection.
[0021] An on-chip photoacoustic gas sensing method based on axial acoustic resonance enhancement includes the following steps: S1: First, a suitable excitation light source is fed into the laser controller 5, and then the laser controller 5 modulates it to the target frequency, which is half of the operating frequency of the photoacoustic detection module 7. S2: The modulated excitation light is coupled into the on-chip optical waveguide module 3 through the optical input port 4, forming an evanescent field on the interface of the optical waveguide module 3 and acting on the micro gas cylinder 8; S3: After the target gas is replenished into the micro gas cylinder 8, the target gas generates the corresponding photoacoustic signal by absorbing the evanescent field energy; S4: The photoacoustic signal propagates inside the miniature gas cylinder 8 and undergoes phase accumulation and spatial superposition during propagation, thereby forming an enhancement effect at a specific propagation distance. The sound wave forms a standing wave distribution during propagation and forms a maximum sound pressure value at the location of the photoacoustic detection module 7. S5: Utilize photoacoustic detection module 7 to receive the enhanced photoacoustic signal and convert it into a corresponding electrical signal for output; S6: The signal processing module amplifies, locks in, demodulates, acquires, and inverts the electrical signal sequentially to obtain the target gas detection result.
[0022] The foregoing has shown and described the main features and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.
[0023] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. An on-chip photoacoustic gas sensing device based on axial acoustic resonance enhancement, characterized by, The system includes a substrate (1), a housing (2) fixedly disposed on the top of the substrate (1), an optical waveguide module (3) disposed on the upper surface of the substrate (1), the optical waveguide module (3) is used to propagate excitation light and form an evanescent field at the waveguide interface, the input end of the optical waveguide module (3) is connected to one end of an optical input port (4), the other end of the optical input port (4) is connected to the output end of a laser controller (5), the input end of the laser controller (5) is connected to the output end of a computer (6), a photoacoustic detection module (7) is disposed parallel above the optical waveguide module (3), a micro gas cylinder (8) is disposed between the photoacoustic detection module (7) and the optical waveguide module (3), the top of the micro gas cylinder (8) is fixedly connected to the photoacoustic detection module (7), the bottom of the micro gas cylinder (8) is fixedly mounted on the substrate (1), a target gas is disposed inside the micro gas cylinder (8), and the photoacoustic detection module (7) is connected to a signal processing module through an electrode (9).
2. The on-chip photoacoustic gas sensing device based on axial acoustic resonance enhancement according to claim 1, wherein, The substrate (1) is made of silicon dioxide or silicon.
3. The on-chip photoacoustic gas sensing device based on axial acoustic resonance enhancement of claim 1, wherein, A gas guiding channel is provided on the side wall of the miniature gas cylinder (8) for replenishing the target gas into the miniature gas cylinder (8).
4. The on-chip photoacoustic gas sensing device based on axial acoustic resonance enhancement of claim 1, wherein, The photoacoustic detection module (7) is a piezoelectric micromechanical ultrasonic transducer (PMUT).
5. A chip-based opto-acoustic gas sensing device based on axial acoustic resonance enhancement according to claim 4, characterized in that, The axial dimension of the micro gas cylinder (8) is matched with the operating frequency of the photoacoustic detection module (7).
6. The on-chip photoacoustic gas sensing device based on axial acoustic resonance enhancement according to claim 5, characterized in that, The axial dimension of the micro gas cylinder (8) is half the wavelength of the corresponding photoacoustic detection module (7), so that an axial first-order standing wave mode is formed in the cavity of the micro gas cylinder (8), and the photoacoustic detection module (7) is located at the antinode of the sound pressure wave to obtain the maximum sound pressure response.
7. The on-chip photoacoustic gas sensing device based on axial acoustic resonance enhancement according to claim 6, characterized in that, The signal processing module includes a preamplifier circuit (10), the output of which is connected to the input of a lock-in amplifier (11), and the output of which is connected to the input of a computer (6).
8. An on-chip photoacoustic gas sensing method based on axial acoustic resonance enhancement, characterized in that, The on-chip photoacoustic gas sensing device based on axial acoustic resonance enhancement as described in claim 7 includes the following steps: S1: First, a suitable excitation light source is fed into the laser controller (5), and then the laser controller (5) modulates it to the target frequency, which is half the operating frequency of the photoacoustic detection module (7); S2: The modulated excitation light is coupled into the on-chip optical waveguide module (3) through the optical input port (4), forming an evanescent field on the interface of the optical waveguide module (3) and acting on the micro gas cylinder (8); S3: After the target gas is added to the micro gas cylinder (8), the target gas generates the corresponding photoacoustic signal by absorbing the evanescent field energy; S4: The photoacoustic signal propagates inside the micro gas cylinder (8) and undergoes phase accumulation and spatial superposition during propagation, thereby forming an enhancement effect at a specific propagation distance. The sound wave forms a standing wave distribution during propagation and forms a maximum sound pressure value at the location of the photoacoustic detection module (7). S5: Receive the enhanced photoacoustic signal using the photoacoustic detection module (7) and convert it into a corresponding electrical signal for output; S6: The signal processing module amplifies, locks in, demodulates, acquires, and inverts the electrical signal sequentially to obtain the target gas detection result.
9. The on-chip photoacoustic gas sensing method based on axial acoustic resonance enhancement according to claim 8, characterized in that, In step S3, the target gas is hydrogen, acetylene, water vapor, carbon monoxide, carbon dioxide, or methane.
10. The on-chip photoacoustic gas sensing method based on axial acoustic resonance enhancement according to claim 8, characterized in that, In step S4, the photoacoustic detection module (7) operates in a high-order vibration mode and the operating frequency is set to 204kHz.