Optical-mechanical gas sensor based on graphene annular microcavity

Abstract

The invention belongs to the technical field of biochemical sensing, and particularly relates to an optical-mechanical gas sensor based on a graphene annular microcavity. According to the sensor, a high-sensitivity and low-noise gas detection platform is constructed by combining a high-quality-factor annular microcavity with single-layer graphene; the sensor excites the boundary of the cavity to generate optical mechanical vibration by utilizing radiation pressure generated by propagation of photons in the microcavity; a phonon laser signal with stable frequency and extremely low noise is formed under the continuous action of the pump light; after target gas molecules are adsorbed by graphene, effective mass change of the microcavity is caused, measurable deviation of phonon laser frequency is caused, and therefore real-time high-sensitivity detection of gas concentration is achieved. The optical-mechanical interaction mechanism, the two-dimensional material gas adsorption characteristic and the microcavity optical regulation and control technology are fused, and the device has the advantages of being high in response speed, low in detection limit, easy to integrate and the like and is suitable for multiple scenes such as environment monitoring, biochemical analysis and industrial safety.

Description

Technical Field

[0001] The present invention belongs to the field of biochemical sensing, and in particular relates to an optomechanical gas sensor based on a graphene annular microcavity. Background Art

[0002] Gas, a fundamental state of matter, has broad and profound applications in key areas such as industrial manufacturing, energy development, environmental protection, and biomedical health monitoring. The presence and concentration changes of different types of gases are often directly linked to system safety, energy efficiency, and even human health. Therefore, efficient and accurate gas detection and identification has become a core issue in modern science and technology. However, the natural properties of gases, such as low density, small molecular weight, strong diffusivity, and amorphous nature, pose numerous challenges to their detection. Especially in complex, multi-component environments, gas detection systems must not only possess high sensitivity and selectivity, but also meet the requirements of rapid response, real-time monitoring, label-free operation, and compact integration. While existing detection technologies such as electrochemical sensors, gas chromatography, and mass spectrometry have established a solid foundation for application, they still face limitations in sensitivity, system complexity, power consumption, and real-time performance. Consequently, the development of new, high-performance gas sensors has become a hot topic in current sensing technology research.

[0003] In recent years, optical microcavity gas sensing technology, as an emerging sensing method, has received widespread attention and application in the fields of national defense, intelligent perception, biochemical detection, etc. due to its excellent anti-electromagnetic interference ability, outstanding sensing performance and good optical system integration. Optical microcavities have ultra-high quality factors and extremely small mode volumes, which can effectively confine the light field to the surface area of ​​the microcavity, thereby significantly extending the photon lifetime and enhancing the interaction between light and matter. Compared with traditional electrochemical gas sensors, microcavity sensors have faster response speeds and higher sensitivity. The microcavity structure based on optical coupling further improves the integration and stability of the system. Thanks to the enhancement effect of the microcavity on the light-matter interaction, this type of sensor provides a new platform for achieving high-performance, low-power and miniaturized gas detection.

[0004] Although optical microcavity gas sensors have significant advantages in sensitivity and integration, their performance improvement still faces two key challenges: first, the noise of the photoelectric signal during the microcavity sensing process is high, which limits the ability to detect extremely low concentrations of gas; second, commonly used microcavity materials are mostly chemically inert media, which make it difficult to achieve efficient adsorption of target gas molecules, thus restricting further improvement of sensing sensitivity.

[0005] Based on this, there is an urgent need to propose a new optical microcavity sensor that can achieve high-performance gas detection to meet the growing performance requirements of gas monitoring technology in complex application scenarios. Summary of the Invention

[0006] In response to the above-mentioned problems or shortcomings, and to solve the problems of existing optical microcavity gas sensors, such as high photoelectric noise of sensing signals and difficulty in effectively adsorbing gas molecules by optical microcavity materials, which limit their application, the present invention provides an optomechanical gas sensor based on a graphene ring microcavity.

[0007] The specific technical solutions are as follows:

[0008] A graphene ring microcavity-based optomechanical gas sensor comprises a graphene ring microcavity, a micro-nano optical fiber, a tunable pump laser, a polarization controller, a photodetector, an electrical signal distributor, an oscilloscope and a spectrum analyzer.

[0009] The graphene annular microcavity is composed of an on-chip annular microcavity and a single layer of graphene attached to the surface of the annular microcavity. The pump light completes intracavity resonance in the annular microcavity, and the single layer of graphene achieves effective adsorption of gas molecules without affecting the quality factor of the annular microcavity.

[0010] The tunable pump laser generates pump light, which passes through a polarization controller and is then coupled into the graphene ring microcavity by a micro-nano optical fiber to excite a photomechanical mode, and then outputs a photomechanical mode signal to a photodetector through micro-nano optical fiber coupling.

[0011] The polarization controller is used to tune the polarization state of the pump light so that the optomechanical mode excited by the pump light coupled to the graphene ring microcavity through the micro-nano optical fiber is stable, thereby generating a stable optomechanical mode signal.

[0012] The photoelectric detector is used to realize photoelectric conversion of the optomechanical mode signal output by the micro-nano optical fiber coupling, and convert the optical signal into an electrical signal.

[0013] The electrical signal distributor (such as a 1×2 type) connects the electrical signal output by the photoelectric detector to the oscilloscope and the spectrum analyzer at the same time, so that the output electrical signal can be detected by the oscilloscope and the spectrum analyzer at the same time.

[0014] The oscilloscope is used to observe the optomechanical mode signal output by the graphene ring microcavity to obtain a stable optomechanical mode signal for sensing.

[0015] The spectrum analyzer is used to analyze the frequency position of the optomechanical mode signal output by the graphene annular microcavity, calculate the frequency drift, and thus inversely calculate the target detection gas concentration.

[0016] Furthermore, the on-chip annular microcavity is a disk structure with a smooth surface formed by photolithography and dry etching on a wafer and laser melting.

[0017] Furthermore, the material of the annular microcavity is silicon dioxide, silicon nitride, magnesium fluoride or lithium niobate, and the disk radius is 30 μm-60 μm to ensure that the pump light can resonate in the cavity.

[0018] Furthermore, the area of ​​the single-layer graphene in the graphene annular microcavity is 400 μm 2 -2500μm 2 , so that the graphene ring microcavity can effectively adsorb gas molecules and effectively tune the optomechanical mode signals in the graphene ring microcavity.

[0019] Furthermore, the single-layer graphene is obtained by a mechanical exfoliation method and is attached to the surface of the annular microcavity through a PDMS transfer process.

[0020] Furthermore, the micro-nano optical fiber is made of silica single-mode optical fiber through a fusion taper method, with a taper region diameter of 500nm-2000nm and an overall length of 2-5cm.

[0021] Furthermore, the tuning range of the tunable pump laser is 1540 nm-1560 nm, so that the optomechanical mode signal in the graphene ring microcavity can be effectively excited.

[0022] Furthermore, the quality factor of the graphene annular microcavity is greater than 10 6 , so that the interaction time between light and matter in the graphene ring microcavity is longer, thereby enhancing the photon residence time and optomechanical coupling efficiency, and the optomechanical mode signal is more easily excited.

[0023] Sensing principle of the present invention: The optomechanical gas sensor based on the graphene annular microcavity provided by the present invention excites the mechanical vibration of the cavity boundary through the radiation pressure generated by the propagation of photons in the annular microcavity, thereby forming a stable optomechanical mode. Due to the continuous injection of pump light, part of the photon energy is converted into phonons and low-frequency photons. Under the enhanced effect of the mechanical resonance of the cavity, a phonon laser signal with a frequency in the MHz range, an extremely narrow linewidth, and extremely low noise is finally formed. When gas molecules in the external environment are adsorbed by graphene, since the graphene is directly attached to the surface of the annular microcavity, the adsorbed molecules will cause a change in the equivalent mass of the microcavity, thereby causing the frequency of the phonon laser signal to shift; and the frequency shift is positively correlated with the adsorption amount of gas molecules (i.e., concentration). Therefore, by detecting the shift with high precision, real-time, label-free, and ultra-high sensitivity detection of the target gas concentration in the environment can be achieved.

[0024] Optomechanical interaction mechanism: Photons carry momentum as they propagate within a microcavity, generating radiation pressure that causes tiny deformations at the cavity boundary. This deformation, in turn, modulates the intracavity light field, enabling bidirectional coupling between light and mechanical motion. Under specific conditions, the continuous interaction of photons can excite coherent phonons, which, under the resonance of the microcavity, form phonon lasers. The frequency of this laser, controlled by the microcavity structural parameters, is typically in the MHz range and exhibits high coherence, narrow bandwidth, and ultra-low noise. Its output signal exhibits a high signal-to-noise ratio and high stability.

[0025] In summary, the present invention pioneered the combination of a high-quality-factor annular optical microcavity with a graphene material with high adsorption properties, and based on the principle of optomechanical interaction, constructed an optomechanical gas sensor that outputs an ultra-low-noise phonon laser. Through the adsorption of gas molecules by graphene, the equivalent mass of the annular microcavity is perturbed and regulated, thereby causing a measurable shift in the phonon laser frequency and achieving highly sensitive detection of the target gas concentration. The present invention integrates multiple cutting-edge technologies, including two-dimensional material physics, micro-nano optomechanical resonance, annular optical microcavity processing, and laser frequency regulation. This breakthrough overcomes the technical bottlenecks of existing optical gas sensors in terms of detection limit, signal-to-noise ratio, and system integration, providing a new path and technical support for the construction of a new generation of high-performance (low-noise, high-sensitivity, low-detection-limit) optomechanical gas sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the three-dimensional structure of the graphene annular microcavity of the present invention;

[0027] Figure 2 A test system diagram of an embodiment;

[0028] Figure 3 is a time domain diagram of the optomechanical mode signal generated in the embodiment;

[0029] Figure 4 is a spectrum diagram of the optomechanical mode signal generated in the embodiment;

[0030] Figure 5 FIG. 4 is a spectrum response diagram of the photomechanical mode signal after gas adsorption in an embodiment.

[0031] Figure numerals: 1-ring microcavity, 2-monolayer graphene, 3-micro-nano optical fiber, 4-tunable pump laser, 5-polarization controller, 6-graphene ring microcavity, 7-photodetector, 8-1×2 type electrical signal distributor, 9-oscilloscope, 10-spectrum analyzer. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] An optomechanical gas sensor based on a graphene ring microcavity includes a graphene ring microcavity, a micro-nano optical fiber, a tunable pump laser, a polarization controller, a photodetector, an electrical signal distributor, an oscilloscope, and a spectrum analyzer. The system diagram is shown in FIG. Figure 2 shown.

[0034] A disk structure is formed on the wafer by photolithography and dry etching, and the material underneath is removed by acid to form a suspended structure. Figure 1 The circular microcavity on the structure chip is shown. Then, the edge of the disk is irradiated by focusing CO2 laser, causing it to melt under heat and naturally shrink under the action of surface tension to form a smooth circular structure, thereby obtaining a circular microcavity (1) with a radius of 46μm.

[0035] A single layer of graphene (2) was obtained by repeatedly taping a graphite block and transferring it to PDMS. In the preparation process of the graphene annular microcavity, the annular microcavity was first fixed on a heating table, and the PDMS with the single layer of graphene was precisely controlled to fit the annular surface of the microcavity by a mechanical displacement table. Then, the PDMS was heated at a constant temperature of 80°C for 10 minutes. The PDMS expanded due to the heat, and the single layer of graphene fell off and bonded to the surface of the annular microcavity through van der Waals forces, resulting in a graphene annular microcavity with a quality factor of 5×10 6 The graphene size is 30μm×50μm, and the graphene transfer position is located on the upper surface of the annular microcavity.

[0036] A micro-nano optical fiber (3) with a length of 3 cm and a cone diameter of 1000 nm is coupled to the equator of the graphene annular microcavity, so as to facilitate excitation of the optical mechanical mode in the annular microcavity by coupling a pump laser.

[0037] Combine Figure 2 The prepared gas sensor device is placed in an environment where gas sensing is required (6), and the laser light generated by the tunable pump laser (4) is coupled into the device through a polarization controller (5) and a micro-nano optical fiber (3). The polarization controller is used to tune the polarization state of the pump light, thereby stabilizing the optomechanical mode signal in the device. Due to the continuous injection of the pump light, part of the photon energy is converted into phonons and low-frequency photons, and under the enhanced effect of the mechanical resonance of the cavity, an optomechanical mode signal is finally formed in the graphene ring microcavity.

[0038] The optomechanical mode signal formed in the graphene annular microcavity is converted into an electrical signal via a photodetector (7), and the electrical signal is split into two via a 1×2 type electrical signal distributor (8), and respectively connected to an oscilloscope (9) and a spectrum analyzer (10). The oscilloscope is used to observe the optomechanical mode signal output by the graphene annular microcavity to select a stable optomechanical mode signal for sensing. The spectrum analyzer is used to analyze the frequency position of the optomechanical mode signal output by the graphene annular microcavity, calculate the frequency drift, and thus inversely calculate the gas concentration.

[0039] In this embodiment, the tunable pump laser outputs a laser with a wavelength of 1551.55 nm and a power of 3 mW, which excites a photomechanical mode signal in the graphene ring microcavity. Figure 3 As shown, it is the time domain of the optomechanical mode signal in the graphene ring microcavity. The period of the oscillation signal is 53.2ns, which proves that optomechanical mode laser has been generated in the graphene ring microcavity.

[0040] Figure 4 This is the spectrum of the optomechanical mode signal output by the graphene ring microcavity. Its center frequency is 21.32 MHz, and the signal-to-noise ratio exceeds 80 dB, demonstrating the ultra-low noise of its optomechanical mode signal. When gas molecules from the external environment are adsorbed by graphene, the graphene is directly attached to the surface of the ring microcavity, causing the adsorbed molecules to change the equivalent mass of the microcavity, thereby causing a shift in the phonon laser frequency. This frequency shift is positively correlated with the amount of gas molecules adsorbed (i.e., concentration). By detecting this shift with high precision, real-time, label-free, and ultra-high-sensitivity detection of the target gas concentration in the environment can be achieved.

[0041] In this embodiment, ammonia gas sensing is achieved in an air environment. Figure 5 The relationship between the ammonia concentration in the graphene ring microcavity and the center frequency of the photomechanical mode signal was recorded. It was found that as the ammonia concentration increased from 0 ppb to 1 ppb, the center frequency of the photomechanical mode signal decreased by approximately 100 Hz. As the ammonia concentration was injected at successively higher concentrations up to 100 ppm, the center frequency of the photomechanical mode signal gradually decreased to approximately 300 Hz. As the ammonia concentration increased from 1 ppb to 100 pm, the response curve exhibited excellent linearity, with a minimum detection limit of 100 ppt.

[0042] As can be seen from the above embodiments, the present invention combines a high-quality factor annular optical microcavity with a graphene material with high adsorption performance, and based on the principle of optomechanical interaction, constructs an optomechanical gas sensor that can output ultra-low-noise phonon lasers. Through the adsorption of gas molecules by graphene, the equivalent mass of the microcavity is perturbation-controlled, thereby causing a measurable shift in the phonon laser frequency, and achieving highly sensitive detection of the target gas concentration. The present invention integrates a number of cutting-edge technologies such as two-dimensional material physics, micro-nano optomechanical resonance, annular optical microcavity processing, and laser frequency control, breaking through the technical bottlenecks of existing optical gas sensors in terms of detection limit, signal-to-noise ratio, and system integration, and providing innovative ideas and technical support for the construction of a new generation of high-performance optomechanical gas sensors.

Claims

1. An optomechanical gas sensor based on a graphene annular microcavity, characterized by: Including graphene ring microcavity, micro-nano optical fiber, tunable pump laser, polarization controller, photodetector, electrical signal distributor, oscilloscope and spectrum analyzer; The graphene annular microcavity is composed of an on-chip annular microcavity and a single-layer graphene attached to the surface of the annular microcavity. The pump light completes the intracavity resonance in the annular microcavity, and the single-layer graphene achieves effective adsorption of gas molecules without affecting the quality factor of the annular microcavity. The tunable pump laser generates pump light, which passes through a polarization controller and is then coupled into the graphene ring microcavity by a micro-nano optical fiber to excite a photomechanical mode, and then outputs a photomechanical mode signal to a photodetector through micro-nano optical fiber coupling; The polarization controller is used to tune the polarization state of the pump light so that the pump light is coupled to the graphene ring microcavity through the micro-nano optical fiber to stimulate the optomechanical mode to be stable, thereby generating a stable optomechanical mode signal; The photoelectric detector is used to realize photoelectric conversion of the optomechanical mode signal coupled out by the micro-nano optical fiber; The electrical signal distributor simultaneously connects the electrical signal output by the photoelectric detector to the oscilloscope and the spectrum analyzer; The oscilloscope is used to observe the optomechanical mode signal output by the graphene ring microcavity to obtain a stable optomechanical mode signal for sensing; The spectrum analyzer is used to analyze the frequency position of the optomechanical mode signal output by the graphene annular microcavity, calculate the frequency drift, and thus inversely calculate the target detection gas concentration.

2. The optomechanical gas sensor based on a graphene annular microcavity according to claim 1, characterized in that: The on-chip annular microcavity is a disk structure with a smooth surface formed by photolithography and dry etching on a wafer and laser melting.

3. The optomechanical gas sensor based on a graphene annular microcavity according to claim 2, characterized in that: The material of the annular microcavity is silicon dioxide, silicon nitride, magnesium fluoride or lithium niobate, and the disk radius is 30 μm-60 μm.

4. The optomechanical gas sensor based on a graphene annular microcavity according to claim 1, characterized in that: The area of ​​the single-layer graphene in the graphene annular microcavity is 400 μm 2 -2500μm 2 .

5. The optomechanical gas sensor based on a graphene annular microcavity according to claim 1, characterized in that: The single-layer graphene is obtained by a mechanical exfoliation method and is attached to the surface of the annular microcavity through a PDMS transfer process.

6. The optomechanical gas sensor based on a graphene annular microcavity according to claim 1, characterized in that: The micro-nano optical fiber is made of silica single-mode optical fiber through a fusion taper method, with a taper region diameter of 500nm-2000nm and an overall length of 2-5cm.

7. The optomechanical gas sensor based on a graphene annular microcavity according to claim 1, characterized in that: The tuning range of the tunable pump laser is 1540nm-1560nm.

8. The optomechanical gas sensor based on a graphene annular microcavity according to claim 1, characterized in that: The quality factor of the graphene annular microcavity is greater than 10 6 .

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