Micro-hemisphere resonator structure for efficient light-mechanical coupling

Abstract

The application discloses a micro-hemisphere resonator structure for efficient optical-mechanical coupling, comprising a micro-hemisphere shell, an optical field localization ring belt structure and a surface grating structure, wherein the micro-hemisphere shell is used for providing a standing wave resonance mode with high mechanical quality factor; the optical field localization ring belt structure is integrally formed on the sidewall of the micro-hemisphere shell corresponding to a region with maximum mechanical vibration displacement; the optical field localization ring belt structure is a continuous ring belt with variable cross-section topography, which is used for generating an effective refractive index gradient in space, thereby generating three-dimensional total reflection constraint on an optical whispering gallery mode, and locally compressing the optical mode volume to the extreme; and the surface grating structure is arrayed and processed on a local surface at the periphery of the optical field localization ring belt structure, which is used for satisfying a phase matching condition of spatial light diffraction, coupling external spatial light into the inside of the optical field localization ring belt structure to excite the optical whispering gallery mode.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano opto-electro-mechanical systems and high-precision inertial sensing technology, specifically relating to a micro-hemispherical resonator structure for efficient opto-mechanical coupling. Background Technology

[0002] Micro-hemispherical resonator gyroscopes, due to their high symmetry and extremely low energy loss, are key inertial devices in the field of high-precision autonomous navigation. In recent years, the development of cavity optomechanics has provided a revolutionary path to break through the electronic thermal noise limit of traditional electrostatic capacitance detection. Utilizing the momentum exchange between photons and phonons for precision measurement has become the core direction of next-generation ultra-high sensitivity sensing.

[0003] However, directly applying traditional three-dimensional macroscopic micro-hemispherical resonators to cavity optical-mechanical systems faces extremely severe technical bottlenecks, namely, "optical-mechanical mode spatial mismatch" and "difficulty in optical field localization." Optomechanical coupling rate With optical mode volume It is inversely proportional to the square root. Traditional millimeter or hundred-micrometer-scale micro-hemispherical surfaces have extremely gentle three-dimensional curvature and lack localized micro-geometric features capable of generating effective abrupt changes in refractive index, resulting in extremely weak three-dimensional spatial constraint on the light field. This not only causes optical whispering-gallery modes to diverge significantly in the target working area, but also results in mode volumes typically reaching 10⁻⁶. -12 m 3 The magnitude of the problem further results in an extremely low overlap integral between the divergent optical field and the extreme region of mechanical vibration, which is completely unable to meet the stringent requirements of high-performance cavity optical-mechanical systems for strong optomechanical coupling.

[0004] On the other hand, although traditional high-quality optical microcavities (such as micro disk cavities, micro ring cavities, micro rod cavities, etc.) have extremely strong optical field spatial confinement capabilities and ultra-high optical quality factors, their micro-volume and simple optical configuration do not have the low-frequency, high-Q three-dimensional mechanical standing wave characteristics (such as n=2 wine glass mode) of macroscopic hemispherical harmonic oscillators, and cannot be directly used as high-performance Coriolis force inertial sensing carriers.

[0005] Furthermore, in traditional whispering-gallery mode resonators, efficient optical field feeding is highly dependent on near-field evanescent wave coupling via tapered fiber or prism. For macroscopic three-dimensional inertial resonators that require maintaining extremely high mechanical quality factors, the proximity or contact of external physical waveguides at the submicron level inevitably introduces severe contact damping, air damping, and mechanical noise, directly disrupting the intrinsic mechanical symmetry and mechanical properties of the system. This fails to meet the high-precision and robust measurement requirements of multi-axis physical quantities (such as angular velocity / angular acceleration) for micro-hemispherical resonators in complex real-world working environments.

[0006] Therefore, how to break through the geometric constraints of traditional single devices, perfectly integrate macroscopic high-quality mechanical standing wave modes and microscopic extreme optical local modes through the evolution of the underlying topology on the same physical carrier, and completely solve the problem of efficient feeding of highly stable, contactless free space light, is a technological gap that urgently needs to be filled in the current field of cavity optical inertial sensing. Summary of the Invention

[0007] The purpose of this invention is to solve the above-mentioned problems and provide a micro-hemispherical resonator structure for efficient optomechanical coupling that can solve the problems of large optical mode volume, spatial mismatch between optical and mechanical modes, and mechanical performance damage caused by contact coupling in existing traditional micro-hemispherical structures due to the lack of an effective three-dimensional spatial confinement mechanism for the optical field.

[0008] To solve the above-mentioned technical problems, the technical solution of the present invention is: a micro-hemispherical resonator structure for efficient optomechanical coupling, comprising a micro-hemispherical shell, an optical field localized ring structure, and a surface grating structure. The micro-hemispherical shell is used to provide standing wave resonant modes with high mechanical quality factors. The optical field localized ring structure is integrally formed on the sidewall of the micro-hemispherical shell corresponding to the region of maximum mechanical vibration displacement. The optical field localized ring structure is a continuous ring with a variable cross-sectional morphology, used to generate an effective refractive index gradient in space, thereby constraining the optical whispering glove mode (WGM) with three-dimensional total internal reflection, thereby locally compressing the volume of the optical mode to the extreme. The surface grating structure is arrayed on the local surface of the optical field localized ring structure to satisfy the phase matching condition of spatial light diffraction, coupling external spatial light into the interior of the optical field localized ring structure to excite the optical whispering glove mode.

[0009] Preferably, the localized optical field annular structure is constructed in situ on the sidewall of the shell or is a variable cross-section geometric feature that protrudes directly outward from the sidewall of the shell. Its specific morphology includes, but is not limited to: a single-sided annular ridge that protrudes directly outward; a stepped confined annular zone constructed by a single-sided concave groove; an annular zone resembling a microdisk or microrod cavity formed by two consecutive annular grooves; or any sidewall deformation structure that can generate an equivalent refractive index gradient in the axial direction to localize the optical field. Specifically, the localized optical field annular structure is composed of two consecutive annular grooves extending circumferentially and a straight annular outer wall between the two annular grooves, forming a microrod cavity feature. The spatial position of the localized optical field annular structure corresponds to the antinode region of the mechanical working mode of the microhemispherical shell, that is, the region of maximum vibration displacement, so that the local center of the optical whispering gallery mode formed by the constraint of this structure is highly overlapped in space with the maximum mechanical deformation, thereby maximizing the overlap integral of the system's mechanical deformation and the optical local field.

[0010] Preferably, the concave surface of the annular groove and the adjacent outer wall of the micro-hemispherical shell and the straight annular outer wall all satisfy a continuous and smooth transition with equal curvature, eliminating geometric angles to avoid parasitic attenuation of the mechanical quality factor of the micro-hemispherical shell.

[0011] Preferably, the radial etching depth of the surface grating structure is less than the overall radial thickness of the localized optical field annular structure; the surface grating serves only as a refractive index perturbation structure on the local surface, so that the grating region provides a spatial wave vector matching feed window without disrupting the total internal reflection boundary conditions of the main optical field and the coherent enhancement mechanism of the optical whispering gallery mode within the localized optical field annular structure; the radial etching depth of the surface grating structure is much smaller than the radial thickness of the localized optical field annular structure, and the ratio of their dimensions differs by at least one order of magnitude, to ensure that the grating structure modulates only the evanescent field or the polar surface optical field of the optical whispering gallery mode.

[0012] Preferably, the radial thickness of the main body of the localized optical field ring structure is on the order of tens to hundreds of micrometers, and the radial etching depth of the surface grating structure is on the order of submicrometers to micrometers.

[0013] Preferably, the period, duty cycle, and effective refractive index configuration of the surface grating structure must satisfy the wave vector matching condition for spatial light feeding at the target operating wavelength; the surface grating only performs selective coherent enhancement coupling on the target optical modes that satisfy the phase matching condition, while mismatched stray optical modes are naturally suppressed by the grating structure due to phase mismatch.

[0014] Preferably, the surface grating structure satisfies the first-order diffraction phase-matching equation, and its grating period is... Satisfying the formula:

[0015] ;

[0016] in, The incident pump light wavelength, The incident angle of the external collimated light relative to the normal to the grating surface is denoted as . The equivalent effective refractive index is determined by the duty cycle of both the grating teeth and the grating groove.

[0017] Preferably, the grating period, grating tooth width, and grating etching depth of the surface grating structure are all subwavelength or wavelength-scale that match the incident light wavelength, so as to form a non-uniform subwavelength optical medium perturbation array.

[0018] Preferably, the micro-hemispherical shell, the optical field local ring structure, and the surface grating structure are monolithic all-dielectric structures integrally microfabricated using the same hard and brittle optical dielectric material; the optical dielectric material must simultaneously possess low intrinsic optical absorption loss and high mechanical quality factor characteristics.

[0019] Preferably, the material of the micro-hemispherical shell, the localized light field ring structure, and the surface grating structure is isotropic high-purity fused silica.

[0020] The beneficial effects of this invention are:

[0021] 1. The present invention provides a micro-hemispherical resonator structure for efficient optomechanical coupling, with actively compressed optical mode volumes: breaking through the morphological limitations of traditional single smooth curved surfaces, an optical potential well is constructed by introducing an effective refractive index gradient. This effectively suppresses the axial divergence of whispering-gallery modes, resulting in a several-order-of-magnitude improvement in the calculated optomechanical coupling efficiency.

[0022] 2. The optimal overlap and deep decoupling of the optical-mechanical modal space of this invention: The local structure of the optical field is precisely anchored in the region of maximum mechanical vibration (antinode), which maximizes the integral of the overlap between the optical local field and the mechanical deformation field; at the same time, with the characteristics of the constant curvature anti-stress concentration process, while endowing the system with extreme optical confinement capability, the original ultra-high mechanical quality factor of the micro-hemispherical shell is completely preserved, realizing the perfect integration of "optical-mechanical" on a single physical carrier.

[0023] 3. This invention features highly stable non-contact wave vector matching feed: Utilizing a subwavelength grating with an extremely shallow thickness compared to the physical thickness of the microcavity as a local coupling window, it completely eliminates the near-field evanescent wave coupling of traditional fiber tapers while perfectly maintaining the total internal reflection circulation conditions of the WGM mode within the cavity. This achieves efficient and lossless feed of spatially free collimated light, significantly improving the robustness of the device under complex external mechanical interference environments. Attached Figure Description

[0024] Figure 1 This is a two-dimensional partial cross-sectional schematic diagram of a micro-hemispherical resonator structure for high-efficiency optomechanical coupling according to different embodiments of the present invention;

[0025] Figure 2 This is the present invention. Figure 1 Enlarged cross-sectional view of the sidewall of the micro-hemispherical shell;

[0026] Figure 3 This invention provides the microscopic dimensional parameters of a local surface grating for a localized ring structure of an optical field, and a schematic diagram illustrating the principle of non-contact feeding of collimated light from external space based on phase-matching conditions.

[0027] Figure 4 This is a cross-sectional view comparing the spatial confinement capability of the embodiment of the present invention and the conventional structure in optical whispering gallery mode. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0029] like Figures 1 to 4 As shown, this invention provides a micro-hemispherical resonator structure for efficient optomechanical coupling, comprising a micro-hemispherical shell, a localized optical field annular structure, and a surface grating structure. The micro-hemispherical shell provides standing wave resonant modes with high mechanical quality factors. The localized optical field annular structure is integrally formed on the sidewall of the micro-hemispherical shell corresponding to the region of maximum mechanical vibration displacement. The localized optical field annular structure is a continuous annular structure with a variable cross-sectional topography, used to generate an effective refractive index gradient in space, thereby constraining the optical whispering-gallery mode (WGM) with three-dimensional total internal reflection, thus locally compressing the optical mode volume to an extreme degree. The surface grating structure is arrayed on a local surface surrounding the localized optical field annular structure to satisfy the phase-matching condition of spatial light diffraction, coupling external spatial light into the interior of the localized optical field annular structure to excite the optical whispering-gallery mode.

[0030] like Figure 1 and Figure 2 As shown, the entire structure is made of an isotropic dielectric material that combines low optical absorption loss and high mechanical quality factor, preferably high-purity fused silica integrally molded. The micro-hemispherical shell substrate typically has a diameter on the order of millimeters, preferably 5 mm, corresponding to the maximum vibration displacement region of the core mechanical working mode. A localized optical field annular structure with variable cross-section characteristics is designed and fused in situ along the circumference.

[0031] In this embodiment, the working mode is like the n=2 wine glass mode, and the region of maximum vibration displacement is the antinode. Figure 1 In the diagram, (a) is a single-sided annular ridge section that bulges outward directly. (b) is a stepped confined annular section constructed from single-sided concave grooves. (c) is a variable cross-section confined annular section composed of continuous irregular undulations. Figure 2 The two-dimensional cross-sectional morphology of the optical field local ring structure and the smooth transition of constant curvature to prevent stress concentration are shown in the preferred embodiment.

[0032] The localized optical field annular structure is either constructed in situ on the sidewall of the shell or is a variable cross-section geometric feature that bulges directly outward from the sidewall of the shell. Its specific morphology includes, but is not limited to: a single-sided annular ridge that bulges directly outward; a stepped confined annular zone constructed by a single-sided concave groove; an annular zone resembling a microdisk or microrod cavity, constrained by two consecutive annular grooves; or any sidewall deformation structure capable of generating an equivalent refractive index gradient in the axial direction to localize the optical field. Specifically, the localized optical field annular structure is composed of two consecutive annular grooves extending circumferentially, and a straight annular outer wall between the two annular grooves, forming a microrod cavity-like feature. The spatial position of the localized optical field annular structure corresponds to the antinode region of the mechanical working mode of the microhemispherical shell, i.e., the region of maximum vibration displacement, so that the local center of the optical whispering gallery mode formed by this structure highly overlaps spatially with the point of maximum mechanical deformation, thereby maximizing the overlap integral of the system's mechanical deformation and the optical local field.

[0033] Starting from the electromagnetic field boundary conditions and the Helmholtz equation, analysis using the equivalent refractive index method reveals that when light propagates circumferentially within the localized annular structure of the optical field, the change in the structure's geometric volume directly causes a spatial step in the effective dielectric constant. Specifically, in the preferred embodiment of the double grooves described above, the grooves at the upper and lower ends become low equivalent refractive index regions due to the reduction of high refractive index medium, while the straight annular band in the middle maintains a high refractive index. This physical configuration constructs a strong refractive index gradient along the axial distribution, thereby triggering an extremely strong total internal reflection constraint force at the boundary.

[0034] The concave surface of the annular groove and the adjacent outer wall of the micro-hemispherical shell and the straight annular outer wall all satisfy a continuous and smooth transition with equal curvature, eliminating geometric angles to avoid parasitic attenuation of the mechanical quality factor of the micro-hemispherical shell.

[0035] The radial etching depth of the surface grating structure is much smaller than the radial thickness of the localized optical field annular structure, with a size ratio at least one order of magnitude different. This ensures that the grating structure modulates only the evanescent field or the epipolar optical field of the optical whispering-gallery mode. Specifically, the size difference is at least one order of magnitude, such as a main annular bandwidth on the order of 60 μm and a grating depth on the order of 1 μm. This ensures that the refractive index perturbation of the shallow grating does not disrupt the total internal reflection boundary conditions of the main optical field within the annular zone. The surface grating serves only as a local surface refractive index perturbation structure, allowing the grating region to provide a spatial wavevector matching feed window without disrupting the total internal reflection boundary conditions of the main optical field within the localized optical field annular structure and the coherent enhancement mechanism of the optical whispering-gallery mode.

[0036] In this embodiment, to eliminate parasitic mechanical losses caused by abrupt changes in manufacturing morphology, the contour boundary of the localized optical field ring structure and the adjacent micro-hemispherical shell surface strictly follow a smooth transition with equal curvature to prevent stress concentration from attenuating the mechanical Q value.

[0037] In this embodiment, to avoid mechanical and acoustic losses, such as thermoelastic losses or acoustic radiation losses, caused by structural cross-section changes or sudden changes in local morphology, a continuous and smooth transition surface design is adopted at the junction of the geometric boundary of the optical field local ring structure and the surface of the adjacent micro-hemispherical shell, as well as at the internal turning points of its own morphological features, to eliminate geometric acute angles and bends.

[0038] In embodiments encompassing various types of variable cross-section microstructures, the tangent of the smooth transition surface remains continuous with the tangents of the two side surfaces. In the optimal embodiment, such as the aforementioned dual-groove microrod cavity structure, the junction of the concave surface of the annular groove with the upper and lower hemispherical sidewalls and the straight outer wall in the middle not only satisfies first-order tangential continuity (C1 continuity) but also strictly follows a continuous fluid-like boundary transition with equal curvature (C2 continuity). This design achieves an extremely small optical mode volume while fundamentally eliminating local stress concentration hotspots generated during actuation, minimizing the parasitic impact of morphology reconstruction on the device's macroscopic mechanical quality factor.

[0039] At the manufacturing process level, the aforementioned smooth morphology with extremely high surface finish can be achieved through a series of three-dimensional micro-nano fabrication techniques, including but not limited to: isotropic / anisotropic dry etching, chemical wet etching, or ultra-precision machining. This structure can be achieved by establishing the basic stepped morphology using fluorine-based dry etching (ICP), followed by a carbon dioxide laser localized transient thermal reflow self-shaping process. Utilizing high-energy laser irradiation with a large localized defocusing amount within an extremely short time, the quartz surface is instantly liquefied and, driven by surface tension, reshaped into a continuous curved surface that satisfies micromechanical optimization and achieves atomic-level roughness.

[0040] The radial thickness of the main body of the localized optical field ring structure is on the order of tens to hundreds of micrometers, and the radial etching depth of the surface grating structure is on the order of submicrometers to micrometers.

[0041] In this embodiment, the localized annular structure of the optical field aims to construct an optical confinement boundary through local geometric changes, in... Figure 2 In the preferred embodiment shown, the structure is specifically defined as a type of microrod cavity feature: it is not a simple columnar protrusion, but rather a straight annular feature band in the middle is shaped by processing an inwardly recessed continuous annular groove above and below the target area, with a radial thickness on the order of tens of micrometers, such as preferably 60 μm.

[0042] This mechanism physically blocks the spillover and divergence of the light field towards the poles of the hemisphere, tightly locking the optical whispering gallery mode within a specified latitude. Theoretical calculations and physical field analysis confirm that introducing this localized light field feature breaks the optical divergence limitation of traditional hemispherical manifolds, and its optical mode volume is extremely compressed to 102. -14 m 3 The magnitude is significant. Furthermore, because the optical local center is perfectly aligned spatially with the point of maximum mechanical vibration, the overlap integral of the optomechanical modes is greatly enhanced, resulting in a calculated optomechanical coupling rate exceeding 10. 19 On the order of Hz / m.

[0043] The period, duty cycle, and effective refractive index configuration of the surface grating structure must satisfy the wave vector matching condition for spatial light feeding at the target operating wavelength. The surface grating selectively and coherently enhances coupling only for target optical modes that meet this phase matching condition, while mismatched stray optical modes are naturally suppressed by the grating structure due to phase mismatch.

[0044] The surface grating structure satisfies the first-order diffraction phase-matching equation, and its grating period... Satisfying the formula:

[0045] ;

[0046] in, The incident pump light wavelength, The incident angle of the external collimated light relative to the normal to the grating surface is denoted as . The equivalent effective refractive index is determined by the duty cycle of both the grating teeth and the grating groove.

[0047] The grating period, grating tooth width, and grating etching depth of the surface grating structure are all on the subwavelength or wavelength scale that match the incident light wavelength, so as to form a non-uniform subwavelength optical medium perturbation array.

[0048] When the target operating wavelength is in the near-infrared communication band, the grating period of the surface grating structure The aperture is 1.6µm, the grating tooth width w is 0.8µm, and the fill factor is 50%.

[0049] The micro-hemispherical shell, the localized optical field ring structure, and the surface grating structure are monolithic all-dielectric structures integrally microfabricated using the same hard and brittle optical dielectric material. The optical dielectric material must simultaneously possess low intrinsic optical absorption loss and a high mechanical quality factor.

[0050] The material preferred for the micro-hemispherical shell, the localized light field ring structure, and the surface grating structure is isotropic high-purity fused silica.

[0051] As shown in Figure 3, in order to efficiently and stably feed the external light field into the resonator, the present invention has a subwavelength non-uniform surface grating structure that matches the target operating wavelength on the local peripheral surface of the light field local ring structure.

[0052] In terms of geometric design, the radial etching depth ed of the surface grating is much smaller than the radial thickness of the main body of the optical field localized annular structure, and the two dimensions preferably differ by at least one order of magnitude. This extremely shallow etching groove serves only as a refractive index perturbation on the surface of the device, and its physical function is to provide a spatial optical wave vector coupling window, without blocking the total internal reflection boundary condition of the optical field inside the thick main annular structure, thus perfectly maintaining the circumferential low-loss propagation of the optical whispering-gallery mode.

[0053] In optical feeding mechanisms, when an external optical element (such as a microlens) feeds a wavelength of... Spatial collimated beam at a specific tilt angle When the grating region is illuminated, the system's equivalent effective refractive index The wave vector is determined by a weighted average of the grating teeth (intrinsic refractive index n1 of the dielectric material) and the grating grooves (typically air, refractive index n2). The surface grating provides additional wave vector compensation through its periodic structure, enabling the free-space light field to meet stringent wave vector matching conditions.

[0054] In a specific preferred embodiment, for example, for near-infrared communication bands, the main body thickness of the optical field localized annular structure is approximately 60 μm, while the grating etching depth ed is only on the order of 1 μm; the total grating length is designed to be on the order of 10.4 μm, and the height is on the order of 68 μm (completely covering or slightly wider than the optical field localization region). In this embodiment, the grating tooth width w is 0.8 μm, and the period... The equivalent refractive index is 1.6 μm (i.e., fill factor ff = 50%), and satisfies the following conditions: Only if the incident light field strictly satisfies the first-order diffraction phase-matching equation. Only when the target mode's optical field is efficiently fed into the annular structure and undergoes coherent interference enhancement can it be achieved, while mismatched stray optical modes are naturally suppressed by the grating. Through the above mechanism, this invention completely eliminates the near-field evanescent wave contact coupling of traditional tapered optical fibers, and realizes efficient non-contact feeding of external collimated light using a local shallow grating, fundamentally eliminating contact damping interference of external waveguides on the intrinsic mechanical modes of the resonator.

[0055] Figure 4 In the image, (a) shows the light field distribution of the traditional micro-hemispherical sidewall; (b) shows the light field distribution after introducing a variable cross-section confined ring structure composed of continuous irregular undulations.

[0056] This invention breaks through the physical limitation of the large size of traditional micro-hemispherical resonator optical modes by introducing an effective refractive index gradient in situ at the point of maximum mechanical deformation to construct the optical confinement boundary. This design perfectly preserves the ultra-high mechanical quality factor of the macroscopic hemisphere while maximizing the integral of the overlap between the optical field and mechanical deformation, greatly improving the optomechanical coupling efficiency of the system and providing a universal structural optimization paradigm for high-performance cavity optomechanical devices.

[0057] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A micro-hemispherical resonator structure for high-efficiency optomechanical coupling, characterized in that: The system comprises a micro-hemispherical shell, a localized optical field annular structure, and a surface grating structure. The micro-hemispherical shell provides a standing wave resonant mode with a high mechanical quality factor. The localized optical field annular structure is integrally formed on the sidewall of the micro-hemispherical shell corresponding to the region of maximum mechanical vibration displacement. The localized optical field annular structure is a continuous annular band with a variable cross-sectional morphology, used to generate an effective refractive index gradient in space, thereby constraining the optical whispering glove mode (WGM) with three-dimensional total internal reflection, thereby locally compressing the optical mode volume to the extreme. The surface grating structure is arrayed on the local surface surrounding the localized optical field annular structure to satisfy the phase matching condition of spatial light diffraction, coupling external spatial light into the interior of the localized optical field annular structure to excite the optical whispering glove mode.

2. The micro-hemispherical resonator structure for high-efficiency optomechanical coupling according to claim 1, characterized in that: The localized optical field annular structure is either constructed in situ on the sidewall of the shell or is a variable cross-section geometric feature that bulges directly outward from the sidewall of the shell. Its specific morphology includes, but is not limited to: a single-sided annular ridge that bulges directly outward; a stepped confined annular zone constructed by a single-sided concave groove; an annular zone resembling a microdisk or microrod cavity formed by two consecutive annular grooves; or any sidewall deformation structure that can generate an equivalent refractive index gradient in the axial direction to localize the optical field. Specifically, the localized optical field annular structure is composed of two consecutive annular grooves extending circumferentially and a straight annular outer wall between the two annular grooves, forming a microrod cavity feature. The spatial position of the localized optical field annular structure corresponds to the antinode region of the mechanical working mode of the microhemispherical shell, that is, the region of maximum vibration displacement, so that the local center of the optical whispering gallery mode formed by the constraint of this structure is highly overlapped in space with the maximum mechanical deformation, thereby maximizing the overlap integral of the system's mechanical deformation and the optical local field.

3. A micro-hemispherical resonator structure for high-efficiency optomechanical coupling according to claim 2, characterized in that: The concave surface of the annular groove and the adjacent outer wall of the micro-hemispherical shell and the straight annular outer wall all satisfy a continuous and smooth transition with equal curvature, eliminating geometric angles to avoid parasitic attenuation of the mechanical quality factor of the micro-hemispherical shell.

4. A micro-hemispherical resonator structure for high-efficiency optomechanical coupling according to claim 1, characterized in that: The radial etching depth of the surface grating structure is less than the overall radial thickness of the localized optical field annular structure; the surface grating serves only as a refractive index perturbation structure on the local surface, ensuring that the grating region provides a spatial wave vector matching feed window without disrupting the total internal reflection boundary conditions of the main optical field within the localized optical field annular structure and the coherent enhancement mechanism of the optical whispering gallery mode; the radial etching depth of the surface grating structure is much smaller than the radial thickness of the localized optical field annular structure, with a size ratio at least one order of magnitude different, to ensure that the grating structure modulates only the evanescent field or the polar surface optical field of the optical whispering gallery mode.

5. A micro-hemispherical resonator structure for high-efficiency optomechanical coupling according to claim 1, characterized in that: The radial thickness of the main body of the localized optical field ring structure is on the order of tens to hundreds of micrometers, and the radial etching depth of the surface grating structure is on the order of submicrometers to micrometers.

6. A micro-hemispherical resonator structure for high-efficiency optomechanical coupling according to claim 1, characterized in that: The period, duty cycle, and effective refractive index configuration of the surface grating structure must meet the wave vector matching condition of spatial light feed at the target operating wavelength. The surface grating only performs selective coherent enhancement coupling on the target optical mode that meets the phase matching condition, while mismatched stray optical modes are naturally suppressed by the grating structure due to phase mismatch.

7. A micro-hemispherical resonator structure for high-efficiency optomechanical coupling according to claim 1, characterized in that: The surface grating structure satisfies the first-order diffraction phase-matching equation, and its grating period... Satisfying the formula: ； in, The incident pump light wavelength, The incident angle of the external collimated light relative to the normal to the grating surface is denoted as . The equivalent effective refractive index is determined by the duty cycle of both the grating teeth and the grating groove.

8. A micro-hemispherical resonator structure for high-efficiency optomechanical coupling according to claim 1, characterized in that: The grating period, grating tooth width, and grating etching depth of the surface grating structure are all subwavelength or wavelength-scale that match the incident light wavelength, so as to form a non-uniform subwavelength optical medium perturbation array.

9. A micro-hemispherical resonator structure for high-efficiency optomechanical coupling according to claim 1, characterized in that: The micro-hemispherical shell, the localized optical field ring structure, and the surface grating structure are monolithic all-dielectric structures integrally microfabricated using the same hard and brittle optical dielectric material; the optical dielectric material must simultaneously possess low intrinsic optical absorption loss and high mechanical quality factor characteristics.

10. A micro-hemispherical resonator structure for high-efficiency optomechanical coupling according to claim 1, characterized in that: The material of the micro-hemispherical shell, the localized light field ring structure, and the surface grating structure is preferably isotropic high-purity fused silica.

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