Wideband acoustic sensing method and system based on hybrid q-value microcavity array and dual optical comb demodulation

Abstract

The application provides a wide-frequency acoustic sensing method and system based on a mixed Q-value microcavity array and a double optical comb demodulation, which comprises the following steps: forming a sensing array by integrating echo wall mode optical microcavities with high Q values and low Q values on the same substrate, and arranging hollow films with different sizes below the microcavities to respectively enhance the mechanical response to low-frequency and high-frequency acoustic waves; generating a signal light frequency comb, coupling each comb tooth to each microcavity and locking it to a resonant spectral line preset working point; the measured acoustic wave drives the film to vibrate and modulates the microcavity resonant wavelength, the high-Q microcavity generates a high-sensitivity light intensity change signal, and the low-Q microcavity generates a wide dynamic range light intensity change signal; the signal light frequency comb carrying acoustic modulation information is coherently heterodyne detected with the local light frequency comb, a plurality of radio frequency beat signals are generated, and after frequency domain separation and demodulation, the acoustic sensing signals of each channel are recovered in parallel and fused and output. The application can simultaneously realize high-sensitivity, wide-frequency response and large dynamic range acoustic detection.

Description

Technical Field

[0001] This invention relates to the field of optical microcavity sensing and acoustic signal detection technology, and in particular to a broadband acoustic sensing method and system based on a hybrid Q-value microcavity array and dual optical comb demodulation. Background Technology

[0002] High-sensitivity detection in the audible sound frequency band has significant application value in military security, industrial monitoring, and acoustic analysis. However, sound waves attenuate rapidly in air, and the dynamic range and spectral distribution of sound fields in real-world scenarios are large, placing comprehensive performance requirements on sensing technologies, including high sensitivity, large bandwidth, and wide dynamic range. Optical microcavities based on whispering-gallery modes, with their ultra-high quality factor and extremely small mode volume, have shown significant advantages in detecting weak acoustic signals and have become a research hotspot in this field.

[0003] In recent years, researchers have achieved high-sensitivity acoustic sensing at the μPa level based on whispering-gallery microcavities. For example, a scheme based on a cantilever beam microsphere cavity achieved 52 μPa / Hz. ¹ / ² The sensitivity of the above-mentioned schemes is high, with a response frequency range of 0-6kHz. The scheme based on calcium fluoride microcavities also achieved extremely high sensitivity in the 100Hz-1kHz frequency range underwater. However, the high sensitivity of these schemes is mostly limited to the vicinity of specific resonant frequencies, the frequency response curve is not flat enough, and the detection bandwidth cannot fully cover the entire audible frequency range. More importantly, there is an inherent contradiction between high sensitivity and wide dynamic range: high sensitivity depends on the ultra-high Q value of the microcavity, which inevitably leads to an extremely narrow resonant spectrum. When the sound pressure is slightly high, the acoustic wavelength shift is very likely to exceed the linear response region, causing signal saturation distortion. To address this problem, some researchers have manually switched different resonant modes of multimode microcavities, improving the dynamic range by 38.3dB. However, this method is essentially a time-division static adjustment and cannot synchronously and continuously detect wide dynamic range acoustic signals with continuously changing intensity in real time.

[0004] Therefore, existing technologies cannot simultaneously achieve high sensitivity, wide frequency response, and large dynamic range, and there is an urgent need for a new sensing architecture that can acquire multi-dimensional acoustic information in parallel and demodulate it efficiently. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a broadband acoustic sensing method and system based on hybrid Q-value microcavity array and dual optical comb demodulation, in order to solve the problems of existing technologies, such as the difficulty in achieving both high sensitivity and wide frequency response, the mutual constraint between high sensitivity and large dynamic range, and the inability to demodulate multi-channel acoustic signals in parallel and continuously.

[0006] On one hand, the present invention provides a broadband acoustic sensing method based on a hybrid Q-value microcavity array and dual optical comb demodulation, the method comprising: A sensing array is provided, wherein multiple whispering-gallery mode optical microcavities are integrated on the same substrate, the multiple whispering-gallery mode optical microcavities including at least a first microcavity with a relatively high quality factor and a second microcavity with a relatively low quality factor; wherein the substrate regions below the first microcavity and below the second microcavity are both hollowed out to form thin films, and at least one first thin film and one second thin film exist, the first thin film having a relatively large area to enhance the response to relatively low frequency sound waves, and the second thin film having a relatively small area to enhance the response to relatively high frequency sound waves; A signal optical frequency comb is generated, and each tooth of the signal optical frequency comb is coupled to the corresponding microcavity in the sensing array, and its wavelength is locked to the preset operating point of the corresponding microcavity resonant spectrum line. The sound wave to be tested is applied to the sensing array such that the first microcavity generates a first light intensity change signal based on its quality factor and the acoustic wavelength shift, the second microcavity generates a second light intensity change signal based on its quality factor and the acoustic wavelength shift, and the first film selectively mechanically enhances the low-frequency component of the sound wave to be tested, and the second film selectively mechanically enhances the high-frequency component of the sound wave to be tested. The signal optical frequency comb carrying the first light intensity change signal and the second light intensity change signal are coherently heterodyne probed with the local oscillator optical frequency comb to generate multiple radio frequency beat frequency signals. The acoustic sensing signals corresponding to different microcavities are then demodulated in parallel from the multiple radio frequency beat frequency signals, so that a detection result with high sensitivity, wide frequency response and large dynamic range can be obtained based on the fusion of the acoustic sensing signals.

[0007] In some embodiments of the present invention, the wavelength of each comb tooth of the signal optical frequency comb is locked to a preset operating point of the corresponding microcavity resonant spectrum line, including: The wavelength of each tooth of the signal optical frequency comb is locked at the point where the slope of the corresponding microcavity resonant spectral line is the maximum.

[0008] In some embodiments of the present invention, both the first thin film and the second thin film are circular silicon dioxide thin films, and their fundamental resonant frequencies satisfy the following relationship: ; in, This represents the fundamental resonant frequency; Indicates the thin film radius; Indicates film thickness; Indicates the Young's modulus of the material; Indicates the density of the material; This indicates the Poisson's ratio of the material.

[0009] In some embodiments of the present invention, the first film has a thickness of 10 micrometers and a radius of 2.11 millimeters, and its resonant center frequency is 5 kHz; the second film has a thickness of 10 micrometers and a radius of 1.22 millimeters, and its resonant center frequency is 15 kHz.

[0010] In some embodiments of the present invention, the quality factor of the first microcavity is set to 10. 8 The quality factor of the second microcavity is set to 10. 6 Magnitude.

[0011] In some embodiments of the present invention, multiple radio frequency beat frequency signals are generated, and acoustic sensing signals corresponding to different microcavities are recovered by parallel demodulation from the multiple radio frequency beat frequency signals, including: The signal optical frequency comb and the local oscillator optical frequency comb are subjected to coherent heterodyne detection to generate a radio frequency beat signal containing multiple subcarriers, wherein each subcarrier corresponds to a microcavity in the sensing array; The radio frequency beat signal is separated in the frequency domain by a set of bandpass filters with different center frequencies to obtain independent subcarrier signals corresponding to each microcavity. The independent subcarrier signals are demodulated by radio frequency to recover the acoustic sensing signals corresponding to each microcavity.

[0012] In some embodiments of the present invention, the amplitude information of the acoustic sensing signal is derived from the magnitude of the corresponding microcavity resonant wavelength offset, and the frequency information of the acoustic sensing signal is derived from the speed of the corresponding microcavity resonant wavelength offset.

[0013] In some embodiments of the present invention, the spacing between the comb teeth of the signal optical frequency comb is matched with the free spectral range of each microcavity in the sensing array, so that each comb tooth corresponds to the resonance peak of a microcavity.

[0014] In some embodiments of the present invention, the method further includes: Based on the intensity characteristics of the sound wave to be measured, the acoustic sensing signal corresponding to the first microcavity or the acoustic sensing signal corresponding to the second microcavity is selectively accepted as the output result to obtain a detection result that combines high sensitivity and wide dynamic range.

[0015] On the other hand, the present invention also provides a broadband acoustic sensing system based on a hybrid Q-value microcavity array and dual optical comb demodulation, comprising: A sensing array, disposed on a single substrate, integrates multiple whispering-gallery-mode optical microcavities. Each whispering-gallery-mode optical microcavity includes at least a first microcavity with a relatively high quality factor and a second microcavity with a relatively low quality factor. The substrate regions below both the first and second microcavities are perforated to form thin films, and at least one first thin film and one second thin film are present. The first thin film has a relatively large area to enhance the response to relatively low-frequency sound waves, while the second thin film has a relatively small area to enhance the response to relatively high-frequency sound waves. The signal optical frequency comb generation module is used to generate a signal optical frequency comb and couple each comb tooth of the signal optical frequency comb to the corresponding microcavity in the sensing array, and the wavelength of each comb tooth is locked to the preset operating point of the corresponding microcavity resonant spectrum line. The local oscillator optical frequency comb generation module is used to generate local oscillator optical frequency combs; The coherent detection and demodulation module is used to perform coherent heterodyne detection on the signal optical frequency comb carrying acoustic modulation information and the local oscillator optical frequency comb to generate multiple radio frequency beat frequency signals, and demodulate in parallel from the multiple radio frequency beat frequency signals to recover the acoustic sensing signals corresponding to different microcavities. The processing module is used to receive and fuse the acoustic sensing signals to output detection results with high sensitivity, wide frequency response and large dynamic range.

[0016] The broadband acoustic sensing method and system based on hybrid Q-value microcavity array and dual optical comb demodulation provided by this invention effectively overcomes the performance bottleneck of traditional optical acoustic sensors in achieving high sensitivity, wide frequency response and large dynamic range by integrating whispering-gallery mode optical microcavities with different quality factors on the same substrate and setting hollow thin film structures of different sizes below the microcavities.

[0017] By employing a high-Q microcavity and a low-Q microcavity in synergy, this invention simultaneously achieves high-sensitivity detection of weak acoustic signals and a wide dynamic range response to larger acoustic signals. When the intensity of the acoustic wave to be measured is weak, the high-Q microcavity, with its extremely narrow resonant spectral line, generates a significant change in light intensity, providing a high-sensitivity output on the order of μPa. When the intensity of the acoustic wave to be measured is large, causing the high-Q microcavity to tend to saturate, the low-Q microcavity, with its wider linear response region, can still maintain a distortion-free linear output, effectively extending the dynamic response range of the sensor.

[0018] By placing perforated thin films of different sizes beneath the microcavity, this invention achieves selective mechanical enhancement of different frequency components within the audible sound band. Large-area thin films have lower resonant frequencies, significantly enhancing low-frequency sound waves; small-area thin films have higher resonant frequencies, significantly enhancing high-frequency sound waves. The synergistic effect of these two materials allows the sensor to maintain high detection sensitivity across the entire audible sound band, effectively broadening the frequency response bandwidth and solving the problem of uneven frequency response curves in traditional solutions.

[0019] By employing a signal optical frequency comb as a multi-wavelength detection light source and combining it with a local oscillator optical frequency comb for coherent heterodyne detection, this invention achieves parallel excitation and synchronous demodulation of multiple microcavity channels in a sensing array. Each tooth of the signal optical frequency comb corresponds to a microcavity resonant peak. The dual-comb heterodyne technique downconverts the acoustic modulation information of each channel in parallel to different subcarriers in the radio frequency domain. After frequency domain separation, the independent acoustic sensing signals of each channel can be synchronously recovered, greatly improving demodulation efficiency and avoiding the cumbersome operations of time-division scanning or manual switching required in traditional methods.

[0020] Furthermore, this invention integrates all functional units in the sensor array onto the same substrate, resulting in a compact structure that facilitates mass production and has promising prospects for engineering applications.

[0021] Additional advantages, objects, and features of the invention will be set forth in part in the description which follows, and will also become apparent in part to those skilled in the art upon studying the description, or may be learned by practice of the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures specifically pointed out in the description and drawings.

[0022] Those skilled in the art will understand that the objectives and advantages achievable with the present invention are not limited to those specifically described above, and that the above and other objectives achievable with the present invention will become clearer from the following detailed description. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, are not intended to limit the scope of the invention. In the drawings: Figure 1 This is a schematic diagram of the steps of a broadband acoustic sensing method based on a hybrid Q-value microcavity array and dual optical comb demodulation in one embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram of the sensor array structure in one embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of the microcavity acoustic sensing principle in one embodiment of the present invention.

[0026] Figure 4This is a schematic diagram illustrating the principle of limited dynamic range of a high-Q microcavity in one embodiment of the present invention.

[0027] Figure 5 This is an overall block diagram of a broadband acoustic sensing system based on a hybrid Q-value microcavity array and dual optical comb demodulation in one embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. Here, the illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention.

[0029] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0030] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components.

[0031] It should also be noted that, unless otherwise specified, the term "connection" in this article can refer not only to a direct connection, but also to an indirect connection involving an intermediary.

[0032] In the following description, embodiments of the invention will be illustrated with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar parts, or the same or similar steps.

[0033] It should be emphasized here that the step markers mentioned below are not a limitation on the order of the steps, but should be understood as meaning that the steps can be executed in the order mentioned in the embodiments, or in a different order than in the embodiments, or several steps can be executed simultaneously.

[0034] To address the challenges of balancing high sensitivity and wide frequency response, the trade-off between high sensitivity and large dynamic range, and the inability to demodulate multi-channel acoustic signals in parallel and continuously in existing technologies, this invention provides a broadband acoustic sensing method based on a hybrid Q-value microcavity array and dual optical comb demodulation, such as... Figure 1 As shown, the method includes the following steps S101~S104: Step S101: Provide a sensing array, which integrates multiple whispering-gallery mode optical microcavities on the same substrate. Each whispering-gallery mode optical microcavity includes at least a first microcavity with a relatively high quality factor and a second microcavity with a relatively low quality factor. The substrate regions below the first and second microcavities are both perforated to form thin films, and at least one first thin film and one second thin film exist. The first thin film has a relatively large area to enhance the response to relatively low-frequency sound waves, and the second thin film has a relatively small area to enhance the response to relatively high-frequency sound waves.

[0035] Step S102: Generate a signal optical frequency comb, couple each tooth of the signal optical frequency comb to the corresponding microcavity in the sensing array, and lock its wavelength to the preset operating point of the corresponding microcavity resonant spectrum line.

[0036] Step S103: Apply the acoustic wave to be tested to the sensing array so that the first microcavity generates a first light intensity change signal based on its quality factor to induce a acoustic wavelength shift, the second microcavity generates a second light intensity change signal based on its quality factor to induce a acoustic wavelength shift, and the first thin film selectively mechanically enhances the low-frequency component of the acoustic wave to be tested, and the second thin film selectively mechanically enhances the high-frequency component of the acoustic wave to be tested.

[0037] Step S104: Perform coherent heterodyne detection on the signal optical frequency comb carrying the first light intensity change signal and the second light intensity change signal and the local oscillator optical frequency comb to generate multiple radio frequency beat frequency signals, and demodulate in parallel from the multiple radio frequency beat frequency signals to recover the acoustic sensing signals corresponding to different microcavities, so as to obtain detection results with high sensitivity, wide frequency response and large dynamic range based on acoustic sensing signal fusion.

[0038] In step S101, a microcavity array integrating multiple sensing units is constructed as the core sensitive front end of the entire acoustic sensing system. This sensing array integrates whispering-gallery mode optical microcavities with different quality factors on a single substrate, and sets hollow thin film structures of different sizes below the microcavities to achieve differentiated responses to different frequency and intensity components in the sound wave under test, providing a physical basis for subsequent parallel acoustic detection with wide bandwidth and wide dynamic range.

[0039] In some embodiments, the sensing array uses a single-crystal silicon wafer as the substrate material. Multiple whispering-gallery mode optical microcavities are fabricated on this silicon substrate using standard micro / nano fabrication processes. The specific structural forms of the whispering-gallery mode microcavities can be microdisk cavities, microring cavities, microsphere cavities, or microcore ring cavities, etc. The multiple microcavities can be arranged in a linear or planar array on the substrate, and the input and output of optical signals are coupled through one or more bus waveguides.

[0040] The multiple whispering-gallery mode optical microcavities integrated in the sensor array include at least two types: a first microcavity with a relatively high quality factor (Q value) and a second microcavity with a relatively low quality factor. The first microcavity is primarily used to achieve high-sensitivity detection of weak acoustic signals, and its Q value is preferably set to 10. 8 The second microcavity is mainly used to achieve wide dynamic range detection of larger acoustic signals, and its Q value is preferably set to 10. 8 The magnitude of the Q value is not explicitly stated here; it should be noted that the specific magnitude of the Q value is merely illustrative and can be adjusted according to specific detection requirements in practical applications. By simultaneously integrating high-Q and low-Q microcavities on the same substrate, a single sensor can possess both high sensitivity and a large dynamic range acoustic response, breaking through the performance bottleneck of traditional single-Q microcavity sensors.

[0041] To achieve effective mechanical modulation of the microcavity by sound waves, the silicon substrate region directly below the microcavity needs to be hollowed out to form a suspended thin film structure.

[0042] In some embodiments, the specific preparation process is as follows: First, a silicon dioxide thin film is deposited or thermally grown on the surface of a silicon substrate as a sacrificial layer. Then, a whispering-gallery pattern microcavity structure is fabricated above this silicon dioxide layer. Next, the silicon material is selectively etched from the back of the substrate using back-side photolithography and deep reactive ion etching until the silicon dioxide layer is exposed. Finally, residual silicon is removed by wet etching or dry etching, releasing the suspended silicon dioxide thin film. Thus, independent thin film structures are formed in the substrate regions below both the first and second microcavities.

[0043] To achieve selective mechanical amplification of sound waves at different frequencies, this invention employs a differentiated design of the dimensions of the thin film beneath the microcavity. Specifically, the sensing array contains at least one relatively large first thin film and one relatively small second thin film.

[0044] In some embodiments, both the first film and the second film are circular silicon dioxide films.

[0045] The fundamental resonant frequency of a circular thin film determines its center frequency, which produces the maximum mechanical response to external sound pressure. According to the theory of thin-plate vibration, the fundamental resonant frequency of a circular thin film fixed on four sides can be approximately described by formula (1): ; (1) in, Indicates the fundamental resonant frequency; Indicates the thin film radius; Indicates film thickness; Indicates the Young's modulus of the material; Indicates the density of the material; This indicates the Poisson's ratio of the material.

[0046] As shown in the above formula, given a fixed material and thickness, the fundamental resonant frequency of the thin film is approximately inversely proportional to the square of its radius. That is, the larger the radius, the lower the resonant frequency, and the more significant the mechanical enhancement effect on low-frequency sound waves; conversely, the smaller the radius, the higher the resonant frequency, and the more significant the mechanical enhancement effect on high-frequency sound waves. Based on this principle, this invention designs thin films with different radii to specifically broaden the overall mechanical frequency response range of the sensor.

[0047] In some embodiments, the first thin film is designed to have a thickness of 10 micrometers and a radius of 2.11 millimeters, and its resonant center frequency is calculated to be approximately 5 kHz according to formula (1), which is used to enhance the response to the low-frequency components of the sound wave under test. The second thin film is also designed to have a thickness of 10 micrometers and a radius of 1.22 millimeters, and its resonant center frequency is approximately 15 kHz, which is used to enhance the response to the high-frequency components of the sound wave under test. Those skilled in the art can select other suitable size parameters according to the requirements of the target detection frequency band and based on the above design principles.

[0048] In terms of layout, some high-Q microcavities and some low-Q microcavities are respectively fabricated on the second thin film (smaller area, enhanced for high frequencies) to enhance the detection capability of high-frequency acoustic components; the other part of the high-Q microcavities and low-Q microcavities are respectively fabricated on the first thin film (larger area, enhanced for low frequencies) to enhance the detection capability of low-frequency acoustic components. With the above layout, the sensor array can form a multi-channel parallel detection capability covering both low and high frequencies.

[0049] Through step S101, a multi-dimensional sensing array integrating a high-Q high-sensitivity channel, a low-Q wide dynamic range channel, a low-frequency enhancement channel, and a high-frequency enhancement channel was successfully constructed, laying the structural foundation for the parallel detection of the full-frequency band and wide dynamic range of the sound wave under test in subsequent steps.

[0050] Figure 2 A schematic diagram of the sensor array structure is shown in one embodiment of the present invention. Figure 2 As shown, the sensing array integrates multiple whispering-gallery mode optical microcavities on the same silicon substrate, with a thin-film structure formed by perforation beneath each microcavity. A larger first thin film enhances the low-frequency acoustic response, while a smaller second thin film enhances the high-frequency acoustic response. High-Q and low-Q microcavities are positioned above thin films of different sizes, forming a multi-channel parallel detection structure. A bus waveguide is used to couple the input and output optical signals.

[0051] In step S102, the optical excitation and operating point locking of the sensing array constructed in step S101 are mainly completed. By generating a signal light frequency comb as a multi-wavelength detection light source, each comb tooth is aligned and coupled to the corresponding microcavity in the sensing array, and the wavelength of each comb tooth is precisely locked to the position with the highest sensitivity on the corresponding microcavity resonant spectrum line, thereby providing a stable optical carrier for realizing multi-channel parallel, high-sensitivity acoustic-optical conversion.

[0052] In some embodiments, an optical frequency comb is used as the detection light source to replace the single-wavelength tunable laser or multiple independent lasers in traditional schemes. An optical frequency comb is a broadband light source composed of a series of coherent spectral lines with equal frequency spacing and locked phase relationship, and its spectrum presents a comb-like structure with equally spaced teeth.

[0053] In some embodiments, the signal optical frequency comb is generated as follows: First, a narrow-linewidth tunable laser is provided as the pump source, with an output wavelength in the communication band (e.g., around 1550 nm) and a narrow linewidth on the order of kHz, to ensure precise locking of the microcavity resonant peak. Then, this pump laser is coupled into a high-Q optical microcavity, such as a calcium fluoride microcavity or a silicon nitride microring cavity, and a broadband Kerr frequency comb is generated through nonlinear optical effects such as cascaded four-wave mixing.

[0054] To achieve parallel excitation of each microcavity in the sensing array, the spacing of the signal optical frequency comb needs to be rationally designed to match the free spectral range of each microcavity in the sensing array. The free spectral range of a microcavity refers to the wavelength or frequency interval between two adjacent resonant modes, and its size is determined by the perimeter and effective refractive index of the microcavity.

[0055] In some embodiments, firstly, the geometry of the microcavities is designed so that the free spectral ranges of each microcavity in the sensing array are substantially consistent or integer multiples of each other. Then, the pump parameters or modulation frequency of the signal optical frequency comb are adjusted, and its tooth spacing is precisely set so that each tooth of the signal optical frequency comb corresponds to a resonant mode of a microcavity at its spectral position. This one-to-one correspondence between the comb teeth and the resonant peaks is a key prerequisite for realizing multi-channel parallel excitation, avoiding the inefficiency of traditional methods that require time-division scanning or mechanical switching of the light source.

[0056] After completing the design of the optical frequency comb tooth spacing, the signal optical frequency comb is introduced into the bus waveguide of the sensing array via optical fiber coupling or spatial optical coupling. The bus waveguide can adopt a ridge waveguide or strip waveguide structure, and through evanescent field coupling, light of different wavelengths in the signal optical frequency comb is coupled into the corresponding microcavities.

[0057] Specifically, when the light from the signal optical frequency comb propagates in the bus waveguide, for a specific wavelength of light, if its frequency matches the resonant frequency of a certain microcavity, then the light of that wavelength will enter the microcavity through evanescent field coupling and circulate within the cavity, forming resonance enhancement; while wavelengths with mismatched frequencies continue to propagate along the waveguide. Thus, each tooth of the signal optical frequency comb is coupled separately and in parallel to the corresponding microcavities in the sensing array, achieving simultaneous excitation of all sensing units.

[0058] To further improve sensing sensitivity and stability, this invention locks the wavelength of each tooth of the signal optical frequency comb to a preset operating point of its corresponding microcavity resonant spectral line. After optical coupling is completed, the resonant wavelength of the microcavity is finely adjusted by adjusting the pump wavelength of the optical frequency comb or by using thermo-optical tuning, electro-optical tuning, or other methods, so that the wavelength of each tooth is precisely aligned with a specific position on its corresponding microcavity resonant spectral line.

[0059] In some embodiments, the preset operating point is selected as the location with the maximum slope of the corresponding microcavity resonant spectral line. The principle is that the transmission spectrum of a whispering-gallery mode microcavity exhibits a Lorentz-shaped depression near the resonant wavelength, with regions on both sides having the maximum absolute slope. When the wavelength of the probe light is locked at this location with the maximum slope, a small shift in the resonant wavelength will cause a linear change in the maximum amplitude of the transmitted light intensity, thereby achieving the highest acousto-optic conversion sensitivity.

[0060] In step S102, a signal optical frequency comb for multi-channel parallel excitation was successfully generated. Each comb tooth was coupled to a microcavity in the sensing array, and the operating point was locked at the point with the highest slope of the spectral line with the highest sensitivity. This provides a stable and sensitive optical carrier condition for the efficient modulation of the microcavities by the acoustic wave in step S103, and also lays the technical foundation for the subsequent parallel demodulation in step S104.

[0061] In step S103, the sound wave to be measured, as the physical quantity to be detected, acts on the sensing array constructed in step S101, causing dynamic changes in the optical resonance characteristics of the microcavity. Through the mechanical resonance enhancement effect of the thin film beneath the microcavity and the differentiated optical responses of microcavities with different Q values, the frequency and intensity information of the sound wave to be measured are encoded into the transmitted light intensity changes of different sensing channels, realizing multi-dimensional parallel conversion of acoustic signals to optical signals.

[0062] First, the sound wave to be measured propagates to the surface of the sensing array as a longitudinal wave in the air. The time-varying sound pressure of the sound wave acts on the suspended thin film structure below each microcavity in the sensing array, driving the thin film to produce forced vibration. Since the dimensions of different thin films have been differentiated in step S101, the mechanical response of thin films with different areas to different frequency sound wave components is significantly different.

[0063] Specifically, the first thin film, due to its relatively large area and radius, has a low fundamental resonant frequency, resulting in a significant mechanical resonance enhancement effect on the lower frequency components of the sound wave. When the sound wave being measured contains frequency components close to the resonant frequency of the first thin film, the vibration amplitude of the thin film reaches its maximum, thus effectively converting the weak low-frequency sound pressure into a considerable mechanical displacement. Similarly, the second thin film, due to its relatively small area and radius, has a higher fundamental resonant frequency, resulting in selective mechanical enhancement of the higher frequency components of the sound wave. Thus, the sensing array achieves parallel and enhanced pickup of different frequency components at the physical level.

[0064] The mechanical vibrations generated by the thin film under acoustic wave drive are directly transmitted to the whispering-gallery mode optical microcavity integrated above it. Since the microcavity and thin film are an integrated structure, the vibrations of the thin film will cause minute periodic changes in the geometry of the microcavity, such as stretching or compression of the microcavity perimeter, or a change in the radius of curvature. This geometric deformation leads to a dynamic change in the optical resonant cavity length of the microcavity.

[0065] According to the resonance condition of the whispering-gallery mode microcavity, when the optical path length of the resonant cavity satisfies At that time, light resonates within the cavity. Indicates optical path length; It is an integer; Indicates the resonant wavelength. Optical path length. It can be represented as ,in, Indicates the effective refractive index of the microcavity material; This represents the physical perimeter of the resonant cavity. When sound waves cause deformation of the microcavity, the physical perimeter changes periodically, resulting in a synchronous dynamic shift in the resonant wavelength. This process is known as acoustic-mechanical-optical coupling, which essentially converts the mechanical energy of sound waves into modulation of the optical resonant mode wavelength through the intermediate medium of thin-film vibration.

[0066] Figure 3 A schematic diagram illustrating the microcavity acoustic sensing principle in one embodiment of the present invention is shown. Figure 3 As shown, when the microcavity is not modulated by acoustic waves, its resonant mode corresponds to the curve. When the microcavity deforms under the influence of sound waves, the length of the resonant cavity changes accordingly, and the resonant mode shifts, corresponding to the curves respectively. and By locking the probe wavelength at the point of maximum slope of the resonant spectral line, even a small shift in the resonant wavelength can cause a significant change in the intensity of the transmitted light, thereby achieving efficient conversion of acoustic signals to optical signals.

[0067] During the process of the microcavity resonant wavelength shifting due to acoustic modulation, since step S102 has locked the wavelength of each comb tooth of the signal optical frequency comb to the maximum slope of the corresponding microcavity resonant spectrum line, the slight shift in the resonant wavelength will directly cause a significant change in the transmitted light intensity of the microcavity.

[0068] For a first microcavity with a relatively high quality factor, its resonant spectrum has an extremely narrow full width at half maximum (FWHM). This is based on the relationship between the microcavity's Q-value and linewidth. When Q is 10 8 At this point, the width of the resonant spectral line is only on the order of femtometers. This extremely narrow spectral line means that at the edge of the resonant peak, the slope of the light intensity change with wavelength is extremely steep. Therefore, when the intensity of the sound wave to be measured is weak and the resulting acoustic wavelength shift is small, the first microcavity can generate a significant change in light intensity, forming a first light intensity change signal, thus achieving highly sensitive detection of weak acoustic signals.

[0069] However, precisely because the spectral lines of the first microcavity are extremely narrow, its linear response range is very limited. When the intensity of the sound wave to be measured is large, the acoustic wavelength shift may exceed the linear region of the resonant spectral lines, causing the output light intensity signal to saturate or become distorted, that is, the dynamic range of the first microcavity is limited.

[0070] Figure 4 A schematic diagram illustrating the principle of limited dynamic range in high-Q microcavities is shown. Figure 4 As shown, high-Q microcavities have extremely narrow resonant valley linewidths. While they achieve very high detection sensitivity at the point of maximum spectral slope, their linear response range is very limited. When the wavelength shift caused by external sound pressure exceeds this linear range, the relationship between transmitted light intensity and wavelength shift ceases to be linear, leading to nonlinear distortion in the sensing signal and severely affecting the accuracy and reliability of detection. In contrast, low-Q microcavities have wider resonant spectral lines and a larger linear response range, maintaining linear output over a wider sound pressure range.

[0071] To address the aforementioned issues, this invention integrates a second microcavity with a relatively low quality factor within the sensing array. The second microcavity exhibits a relatively wide resonant spectral linewidth (approximately on the picometer scale), and its linear response region at the resonant peak edge is even broader. Even when the intensity of the sound wave being measured is high and the acoustic wavelength shift is significant, the second microcavity can still generate a proportional change in light intensity within the linear region, forming a second light intensity change signal, thereby providing a wide dynamic range detection capability. Although the sensitivity of the second microcavity is relatively low, it ensures that the sound pressure level signal is not clipped or distorted, effectively compensating for the insufficient dynamic range of the first microcavity.

[0072] Through the above mechanism, the first and second microcavities work together in the same sensing array: the first microcavity is responsible for capturing weak sound signals and providing high-sensitivity output; the second microcavity is responsible for processing larger sound signals and providing wide dynamic range output. The two complement each other, enabling a single sensing system to simultaneously handle a wide dynamic range sound field, from extremely weak to relatively strong sound pressure levels.

[0073] In summary, by combining the above three steps, different frequency and intensity components of the sound wave under test are distributed and differentiatedly encoded into the transmitted light intensity variations of different microcavity channels. Specifically: The low-frequency weak signal mainly generates a strong response in the "first microcavity + first thin film (large area)" channel; Low-frequency strong signals mainly generate a distortion-free linear response in the "second microcavity + first thin film (large area)" channel; The strong response of the high-frequency weak signal is mainly generated in the "first microcavity + second thin film (small area)" channel; High-frequency strong signals mainly generate a distortion-free linear response in the "second microcavity + second thin film (small area)" channel.

[0074] Therefore, the optical signal output by the sensor array carries multiple independent modulation information corresponding to different frequency components and different intensity components, providing rich raw data for parallel demodulation and signal fusion in step S104.

[0075] Through step S103, the parallel conversion of the sound wave under test into multiple optical intensity modulation signals was successfully achieved. The differentiated design of the thin film broadened the mechanical frequency response range of the sensor, and the integration of the hybrid Q-value microcavity broke through the performance bottleneck of the difficulty in balancing high sensitivity and wide dynamic range. The synergistic effect of the two enabled the sensor array to comprehensively and accurately encode the acoustic-optical information of the wide-bandwidth, wide dynamic range sound field.

[0076] In step S104, the parallel demodulation and signal recovery of the multi-channel optical intensity modulation signals generated in step S103 are mainly completed. Using dual-optical frequency comb heterodyne detection technology, the signal optical frequency comb carrying acoustic modulation information is coherently mixed with the local oscillator optical frequency comb. The wavelength shift information of the optical frequency band is linearly down-converted to the radio frequency domain. Then, the frequency division multiplexing principle is used to separate and demodulate the signals of each channel, ultimately recovering the independent acoustic sensing signals corresponding to each microcavity in parallel.

[0077] First, an independent local oscillator optical frequency comb is generated. There is a slight frequency difference between the tooth spacing of the local oscillator optical frequency comb and the tooth spacing of the signal optical frequency comb. This frequency difference is the key to realizing multi-channel frequency division multiplexing.

[0078] Then, the signal optical frequency comb output from step S103, carrying the first and second light intensity change signals, is input together with the local oscillator optical frequency comb into a balanced photodetector for coherent heterodyne detection. After the two optical frequency combs are mixed on the detector, a radio frequency beat frequency signal containing multiple subcarriers is generated. Due to the difference in the spacing between the comb teeth of the two optical frequency combs, the modulation information carried by different comb teeth in the signal optical frequency comb is mapped onto each subcarrier in the radio frequency domain whose frequency positions do not overlap. Each subcarrier corresponds to a microcavity in the sensing array.

[0079] After obtaining the composite radio frequency beat frequency signal containing multiple subcarriers, it is frequency-domain separated by a set of bandpass filters with different center frequencies. The center frequency of each bandpass filter is matched with the radio frequency subcarrier frequency corresponding to a specific microcavity, thereby effectively separating the individual subcarrier components in the composite signal and obtaining the independent subcarrier signals corresponding to each microcavity.

[0080] Each independent subcarrier signal after separation is demodulated by radio frequency (such as envelope detection or phase-locked amplification) to recover the acoustic sensing signal corresponding to each microcavity. The amplitude information of the acoustic sensing signal comes from the magnitude of the corresponding microcavity resonant wavelength offset, reflecting the sound pressure amplitude of the sound wave under test; the frequency information of the acoustic sensing signal comes from the rate of the corresponding microcavity resonant wavelength offset, reflecting the frequency characteristics of the sound wave under test.

[0081] After recovering the acoustic sensing signals corresponding to each microcavity, the processing module selectively accepts signals from different channels based on the intensity and frequency characteristics of the sound wave being measured. For example, for weak sound signals, the high-Q output of the first microcavity channel is accepted; for strong sound signals, the wide dynamic range output of the second microcavity channel with a low Q value is accepted; and for different frequency components, the responses of the corresponding resonant enhancement film channels are accepted respectively. Through the fusion processing of multi-channel signals, a detection result that combines high sensitivity, wide frequency response, and large dynamic range is finally obtained.

[0082] Through step S104, parallel and efficient demodulation of the multi-channel acoustic-optical modulation signal of the sensor array was successfully achieved, providing complete raw data for subsequent signal fusion.

[0083] Corresponding to the above method, the present invention also provides a broadband acoustic sensing system based on a hybrid Q-value microcavity array and dual optical comb demodulation, such as... Figure 5 As shown, it includes: A sensing array, mounted on a single substrate, integrates multiple whispering-gallery-mode optical microcavities. Each microcavity includes at least a first microcavity with a relatively high quality factor and a second microcavity with a relatively low quality factor. The substrate regions below both the first and second microcavities are perforated to form thin films, with at least one first film and one second film present. The first film has a relatively large area to enhance the response to relatively low-frequency sound waves, while the second film has a relatively small area to enhance the response to relatively high-frequency sound waves.

[0084] The signal optical frequency comb generation module is used to generate the signal optical frequency comb and couple each comb tooth of the signal optical frequency comb to the corresponding microcavity in the sensing array, and the wavelength of each comb tooth is locked to the preset operating point of the corresponding microcavity resonant spectrum line.

[0085] The local oscillator optical frequency comb generation module is used to generate local oscillator optical frequency combs.

[0086] The coherent detection and demodulation module is used to perform coherent heterodyne detection on the signal optical frequency comb carrying acoustic modulation information and the local oscillator optical frequency comb to generate multiple radio frequency beat frequency signals, and demodulate in parallel from the multiple radio frequency beat frequency signals to recover the acoustic sensing signals corresponding to different microcavities.

[0087] The processing module is used to receive and fuse the acoustic sensing signals to output detection results with high sensitivity, wide frequency response and large dynamic range.

[0088] Corresponding to the above method, the present invention also provides an electronic device including a computer device, the computer device including a processor and a memory, the memory storing computer instructions, the processor executing the computer instructions stored in the memory, and when the computer instructions are executed by the processor, the electronic device performs the steps of the method as described above.

[0089] This invention also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the aforementioned method. The computer-readable storage medium may be a tangible storage medium, such as random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, register, floppy disk, hard disk, removable storage disk, CD-ROM, or any other form of storage medium known in the art.

[0090] Those skilled in the art will understand that the exemplary components, systems, and methods described in conjunction with the embodiments disclosed herein can be implemented in hardware, software, or a combination of both. Whether implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this invention. When implemented in hardware, it can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this invention are programs or code segments used to perform the desired tasks. The programs or code segments can be stored in a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried in a carrier wave.

[0091] It should be clarified that the present invention is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of the present invention.

[0092] In this invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or in place of features of other embodiments.

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various modifications and variations of the embodiments of the present invention are possible. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A broadband acoustic sensing method based on a hybrid Q-value microcavity array and dual optical comb demodulation, characterized in that, The method includes: A sensing array is provided, wherein multiple whispering-gallery mode optical microcavities are integrated on the same substrate. The multiple whispering-gallery mode optical microcavities include at least a first microcavity having a first quality factor and a second microcavity having a second quality factor, wherein the first quality factor is higher than the second quality factor. The substrate regions below the first microcavity and below the second microcavity are both perforated to form thin films, and at least one first thin film and one second thin film exist. The area of ​​the first thin film is larger than the area of ​​the second thin film. The first thin film is used to enhance the response to low-frequency sound waves, and the second thin film is used to enhance the response to high-frequency sound waves. A signal optical frequency comb is generated, and each tooth of the signal optical frequency comb is coupled to the corresponding microcavity in the sensing array, and its wavelength is locked to the preset operating point of the corresponding microcavity resonant spectrum line. The sound wave to be tested is applied to the sensing array such that the first microcavity generates a first light intensity change signal based on its quality factor and the acoustic wavelength shift, the second microcavity generates a second light intensity change signal based on its quality factor and the acoustic wavelength shift, and the first film selectively mechanically enhances the low-frequency component of the sound wave to be tested, and the second film selectively mechanically enhances the high-frequency component of the sound wave to be tested. The signal optical frequency comb carrying the first light intensity change signal and the second light intensity change signal are coherently heterodyne probed with the local oscillator optical frequency comb to generate multiple radio frequency beat frequency signals. The acoustic sensing signals corresponding to different microcavities are then demodulated in parallel from the multiple radio frequency beat frequency signals, so that a detection result with high sensitivity, wide frequency response and large dynamic range can be obtained based on the fusion of the acoustic sensing signals.

2. The broadband acoustic sensing method based on hybrid Q-value microcavity array and dual optical comb demodulation according to claim 1, characterized in that, Locking the wavelength of each comb tooth of the signal optical frequency comb to a preset operating point of the corresponding microcavity resonant spectrum line includes: The wavelength of each tooth of the signal optical frequency comb is locked at the point where the slope of the corresponding microcavity resonant spectral line is the maximum.

3. The broadband acoustic sensing method based on hybrid Q-value microcavity array and dual optical comb demodulation according to claim 1, characterized in that, Both the first and second films are circular silicon dioxide films, and their fundamental resonant frequencies satisfy the following relationship: ； in, This represents the fundamental resonant frequency; Indicates the thin film radius; Indicates film thickness; Indicates the Young's modulus of the material; Indicates the density of the material; This indicates the Poisson's ratio of the material.

4. The broadband acoustic sensing method based on hybrid Q-value microcavity array and dual optical comb demodulation according to claim 3, characterized in that, The first film has a thickness of 10 micrometers and a radius of 2.11 millimeters, and its resonant center frequency is 5 kHz; the second film has a thickness of 10 micrometers and a radius of 1.22 millimeters, and its resonant center frequency is 15 kHz.

5. The broadband acoustic sensing method based on hybrid Q-value microcavity array and dual optical comb demodulation according to claim 1, characterized in that, The quality factor of the first microcavity is set to 10. 8 The quality factor of the second microcavity is set to 10. 6 Magnitude.

6. The broadband acoustic sensing method based on hybrid Q-value microcavity array and dual optical comb demodulation according to claim 1, characterized in that, Generating multiple radio frequency beat frequency signals and demodulating them in parallel to recover the acoustic sensing signals corresponding to different microcavities includes: The signal optical frequency comb and the local oscillator optical frequency comb are subjected to coherent heterodyne detection to generate a radio frequency beat signal containing multiple subcarriers, wherein each subcarrier corresponds to a microcavity in the sensing array; The radio frequency beat signal is separated in the frequency domain by a set of bandpass filters with different center frequencies to obtain independent subcarrier signals corresponding to each microcavity. The independent subcarrier signals are demodulated by radio frequency to recover the acoustic sensing signals corresponding to each microcavity.

7. The broadband acoustic sensing method based on hybrid Q-value microcavity array and dual optical comb demodulation according to claim 6, characterized in that, The amplitude information of the acoustic sensing signal comes from the magnitude of the corresponding microcavity resonant wavelength offset, and the frequency information of the acoustic sensing signal comes from the speed of the corresponding microcavity resonant wavelength offset.

8. The broadband acoustic sensing method based on hybrid Q-value microcavity array and dual optical comb demodulation according to claim 1, characterized in that, The spacing between the comb teeth of the signal optical frequency comb is matched with the free spectral range of each microcavity in the sensing array, so that each comb tooth corresponds to the resonance peak of a microcavity.

9. The broadband acoustic sensing method based on hybrid Q-value microcavity array and dual optical comb demodulation according to claim 1, characterized in that, The method further includes: Based on the intensity characteristics of the sound wave to be measured, the acoustic sensing signal corresponding to the first microcavity or the acoustic sensing signal corresponding to the second microcavity is selectively accepted as the output result to obtain a detection result that combines high sensitivity and wide dynamic range.

10. A broadband acoustic sensing system based on a hybrid Q-value microcavity array and dual optical comb demodulation, characterized in that, include: A sensing array, disposed on a single substrate, integrates multiple whispering-gallery-mode optical microcavities. Each whispering-gallery-mode optical microcavity includes at least a first microcavity with a first quality factor and a second microcavity with a second quality factor, the first quality factor being higher than the second quality factor. The substrate regions below the first and second microcavities are both perforated to form thin films, and at least one first thin film and one second thin film exist. The area of ​​the first thin film is larger than the area of ​​the second thin film. The first thin film enhances the response to low-frequency sound waves, and the second thin film enhances the response to high-frequency sound waves. The signal optical frequency comb generation module is used to generate a signal optical frequency comb and couple each comb tooth of the signal optical frequency comb to the corresponding microcavity in the sensing array, and the wavelength of each comb tooth is locked to the preset operating point of the corresponding microcavity resonant spectrum line. The local oscillator optical frequency comb generation module is used to generate local oscillator optical frequency combs; The coherent detection and demodulation module is used to perform coherent heterodyne detection on the signal optical frequency comb carrying acoustic modulation information and the local oscillator optical frequency comb to generate multiple radio frequency beat frequency signals, and demodulate in parallel from the multiple radio frequency beat frequency signals to recover the acoustic sensing signals corresponding to different microcavities. The processing module is used to receive and fuse the acoustic sensing signals to output detection results with high sensitivity, wide frequency response and large dynamic range.

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