Efficient micro-ring acousto-optic modulator

Abstract

The invention provides a high-efficiency micro-ring acousto-optic modulator, which combines high sensitivity and sound wave regulation and control capability of a micro-ring resonator, adopts two pairs of optical waveguides and acoustic waveguides with grating couplers, realizes flexible control of sound wave and light wave propagation directions, can be configured to perform common or reverse propagation, and can be used for acoustic wave and light wave propagation. The method is suitable for exploring the time reversal symmetry and the optical nonreciprocity of the system. The device adopts the sapphire substrate, by virtue of high mechanical strength, high sound velocity and low acoustic loss, the sound wave mode quality and transmission stability are improved, and meanwhile, high-quality integration with silicon dioxide and lithium niobate films is ensured; the silicon substrate has remarkable advantages in the aspects of micro-nano processing, heat conductivity and electro-optical system compatibility, and large-scale manufacturing and system integration are facilitated. In addition, a chalcogenide waveguide with low optical loss is introduced into the device, so that the light field constraint and locality are enhanced, the overlapping and coupling strength of an acousto-optic mode is improved, and meanwhile, the interface scattering loss is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of integrated optics, and in particular relates to a high-efficiency micro-ring acousto-optic modulator. Background Art

[0002] High-performance acousto-optic modulators (AOMs) play a key role in microwave-to-lightwave conversion. They rely on the interaction between phonons and photons to control the refractive index of the medium, achieving dynamic modulation of the light field. With the surge in communication data volume, higher requirements are placed on modulation rate, operating frequency band, conversion efficiency, and energy consumption. Traditional bulk AOMs typically use acousto-optic crystals such as tellurium oxide (TeO2) and piezoelectric transducers. Although they have stable performance, they are large in size, have high power consumption, and are difficult to be compatible with CMOS processes, limiting their application in integrated photonics.

[0003] To meet the demands of next-generation optical communications and quantum information systems for miniaturized, low-power, and high-efficiency modulators, integrated acousto-optic modulators have become a research hotspot. Microring resonators, with their compact structure and resonance-enhancing properties, can significantly enhance light-acoustic interactions. Under conditions of acousto-optic resonance, the intermodal scattering mechanism enables energy coupling between different optical modes, improving modulation efficiency while also enabling nonreciprocal transmission, frequency conversion, and modal control, providing a new path for integrated multifunctional photonic devices.

[0004] In terms of materials, the sapphire-silicon dioxide structure leverages sapphire's high thermal conductivity, wide transparency window, and high mechanical Q, combined with optimized waveguide design (such as a high-refractive-index-contrast interface), to significantly enhance acousto-optic coupling efficiency. Furthermore, the combination of the sapphire substrate and lithium niobate film enables ultra-low loss and high-speed acoustic wave propagation, providing the physical foundation for high-performance modulation.

[0005] Another promising structure is a thin-film lithium niobate-chalcogenide heterojunction integrated circuit based on a silicon-silicon dioxide substrate. This solution combines CMOS compatibility with high refractive index contrast. Leveraging the excellent electro-optical conversion properties of thin-film lithium niobate and the remarkable photoelastic response of chalcogenides, it achieves high-speed, low-power, and high-modulation-depth acousto-optic modulators, promising applications in next-generation programmable photonic chips and quantum control systems.

[0006] In summary, microring acousto-optic modulators based on sapphire-silicon dioxide or silicon-silicon dioxide platforms and combined with intermodal scattering mechanisms have outstanding integration, controllability and versatility, and show broad application prospects in non-reciprocal devices, on-chip optical networks, high-sensitivity sensing and frequency processing. Summary of the Invention

[0007] In order to solve the technical problems existing in the background technology, the present invention aims to provide a high-efficiency microring acousto-optic modulator, which fully utilizes the excellent piezoelectric effect and photoelastic effect of lithium niobate, combines the contribution of sapphire substrate and silicon substrate to surface acoustic wave-like bound states, and utilizes local acoustic resonance and optical resonance to enhance the intensity of acousto-optic interaction, thereby improving the conversion efficiency of microwaves to light waves.

[0008] In order to solve the technical problem, the technical solution of the present invention is:

[0009] A high-efficiency microring acousto-optic modulator includes a substrate, wherein the substrate includes: a substrate and a silicon dioxide layer disposed thereon; a lithium niobate-chalcogenide glass heterogeneous layer disposed on the silicon dioxide layer; the heterogeneous layer includes a lithium niobate thin film and a chalcogenide glass integrated on the lithium niobate thin film;

[0010] Two pairs of transduction regions are provided on the lithium niobate film, and interdigital transducers are provided on the transduction regions. Two pairs of acoustic and optical tapered transition regions, two pairs of grating couplers, two pairs of optical waveguides, two pairs of subwavelength acoustic waveguides, and a microring resonant cavity are formed in the chalcogenide glass. The two ends of the subwavelength acoustic waveguides are connected to the interdigital transducers via the acoustic tapered transition regions, and the two ends of the optical waveguide are connected to the grating couplers via the optical tapered transition regions. Acousto-optic modulation is achieved through point coupling between the microring resonant cavity, the subwavelength acoustic waveguide, and the optical waveguide.

[0011] Furthermore, the transduction region is formed by etching a lithium niobate film, the tapered transition region, the grating coupler, the optical waveguide, the subwavelength acoustic waveguide and the microring resonant cavity are all formed by etching the same chalcogenide glass, the substrate is a sapphire substrate or a silicon substrate, the acoustic mode in the subwavelength acoustic waveguide is a bound state surface acoustic wave mode, and the acoustic wave is in a resonant state; wherein the thickness of the sapphire substrate (1) or the silicon substrate (2) is 1 μm to 800 μm, the thickness of the silicon dioxide layer in the silicon-silicon dioxide substrate is 500 nm to 4000 nm, the thickness of the silicon dioxide layer in the sapphire-silicon dioxide substrate is 0 nm to 4000 nm, the thickness of the lithium niobate film is 200 nm to 1000 nm, and the thickness of the chalcogenide waveguide is 500 nm to 1500 nm.

[0012] Furthermore, the microring resonator is composed of two pairs of optical waveguides, two pairs of subwavelength acoustic waveguides and a microring resonant cavity; the waveguide widths of the optical waveguides, subwavelength acoustic waveguides and microring resonant cavity are all between 500nm and 1500nm;

[0013] The coupling spacing between the optical waveguide and the microring resonant cavity is 300nm to 1000nm, the coupling spacing between the subwavelength acoustic waveguide and the microring resonant cavity is also 300nm to 1000nm, the circumference of the microring resonant cavity is designed to be an integer multiple of the acoustic wavelength, the radius of the microring resonant cavity is 20 to 50 acoustic wavelengths, and the bending radius of the curved waveguide portion of the optical waveguide is 15 to 45 acoustic wavelengths. Inter-modal scattering occurs between the acoustic waves in the microring resonant cavity and optical modes of different orders. The acoustic waves excite the effective refractive index modulation between adjacent optical modes in the microring resonant cavity, thereby achieving energy exchange and coupling between different optical modes, thereby enhancing acousto-optic interaction and improving acousto-optic modulation efficiency and modulation depth.

[0014] Furthermore, the tangent direction of the lithium niobate film is X-cut, Y-cut or Z-cut for the interdigital transducer, the width of the transduction area is 0.01μm to 20μm, the finger width of the interdigital transducer is 0.2μm to 5μm, the number of interdigital pairs is 20 to 300 pairs, and the interdigital transducer is used to achieve 300MHz to 8GHz Rayleigh-like modes and Love-like modes excitation.

[0015] Furthermore, the chalcogenide glass material has a lower acoustic velocity and acoustic impedance than the lithium niobate film. The difference in acoustic impedance between the chalcogenide glass and the lithium niobate film forms an acoustic wave reflection interface, effectively confining the acoustic waves within the chalcogenide waveguide. This structure effectively suppresses acoustic radiation losses, improves the acoustic mode quality factor (Q factor) and the overlap of acousto-optic modes, and thus enhances the acousto-optic coupling efficiency. This structure achieves subwavelength acoustic mode transmission while maintaining high mode field confinement and high modulation efficiency, providing strong support for the high performance and miniaturization of integrated acousto-optic modulators.

[0016] A working method of a microring acousto-optic modulator, the method comprising: based on the inverse piezoelectric effect of a lithium niobate film, converting an input microwave modulation signal into an acoustic wave signal on the surface of the lithium niobate film through an interdigital transducer, so that a periodic mechanical strain field distribution is formed in the lithium niobate film; the mechanical acoustic wave generated on the surface of the lithium niobate film is efficiently coupled to a subwavelength acoustic waveguide through an acoustic conical transition region, wherein the acoustic wave types mainly include Rayleigh-like waves and Love-like waves, both of which have transverse wave characteristics, that is, the particle vibration direction is perpendicular to the wave propagation direction. Due to the strong confinement characteristics of such acoustic waves in the subwavelength acoustic waveguide, A localized acoustic field is effectively formed and well guided into the microring resonant cavity; for the optical mode, the external laser is coupled into the optical tapered transition region through a grating coupler, propagates along the optical straight waveguide to its curved part, and effectively couples with the microring resonant cavity; in the microring resonant cavity, the acoustic field and the light field are resonantly coupled, and the acoustic wave forms a periodic strain field in the microring area, which modulates the refractive index distribution of the material in the microring based on the photoelastic effect, thereby modulating the light field. The optical resonant mode therefore carries the acoustic wave signal excited by the radio frequency signal, thereby completing the effective modulation of the electrical signal to the optical signal.

[0017] Compared with the prior art, the advantages of the present invention are:

[0018] The high-efficiency microring acousto-optic modulator provided by the present invention is arranged on a sapphire-silicon dioxide substrate and a silicon-silicon dioxide substrate, and is composed of an interdigital transducer, an acoustic / optical tapered transition region, a grating coupler, a subwavelength acoustic waveguide, an optical waveguide, and a microring resonant cavity;

[0019] First, sapphire is used as the substrate material and X-cut Y-conducting lithium niobate film is used as the piezoelectric material. The large contrast in sound velocity between sapphire, lithium niobate and silicon dioxide is utilized to achieve low sound wave propagation loss and support higher frequency (GHz level) acousto-optic modulation. At the same time, sapphire's near-infrared transparency and low light absorption loss provide the microring resonator with a high Q value, which can achieve efficient acousto-optic coupling.

[0020] Second, silicon / sapphire is used as the substrate material, X-cut-Y-transduced lithium niobate film is used as the piezoelectric material, and chalcogenide medium is used as the waveguide material. By optimizing the chalcogenide waveguide structure, the sidewall scattering loss is reduced, and the microring resonance is enhanced. The use of silicon as the substrate material shows unique advantages in large-scale integration, cost control and CMOS compatibility.

[0021] Third, the RF signal is converted into acoustic waves through the IDT. The IDT converts the electrical signal into surface acoustic waves through the piezoelectric effect of the lithium niobate thin film. These waves propagate along the acoustic straight waveguide through the etched tapered transition zone. The acoustic waves form a periodic strain field in the microring region, modulating the refractive index through the photoelastic effect and causing physical deformation of the waveguide through the moving boundary effect. External laser light is coupled into the optical waveguide through a first pair of grating couplers. The light field is coupled into the microring via evanescent waves. The microring circumference is designed to be an integer multiple of the acoustic wavelength to enhance resonance. The device achieves efficient modulation through the synergistic effect of acoustic and optical waves.

[0022] Fourth, we design two pairs of bidirectional waveguides and couplers that allow for free choice of the propagation direction between acoustic and optical waves, and they can be configured to co-propagate or counter-propagate, allowing us to explore and verify the time-reversal symmetry and optical reciprocity of the system.

[0023] Fifth, the optimized microring resonator is insensitive to the coupling conditions of acoustic waves, has a wide range of working conditions, and can be driven to resonate by various types of IDTs, including but not limited to focusing IDTs, unidirectional IDTs, unidirectional focusing IDTs, and the general IDT introduced in the present invention.

[0024] The above-mentioned acousto-optic modulator has high modulation efficiency, strong acousto-optic interaction and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 , a cross-sectional view of a sub-wavelength waveguide based on heterogeneous integration of silicon-silicon dioxide substrate / sapphire-silicon dioxide substrate in an embodiment of the present invention;

[0026] Figure 2 , a schematic diagram of the microring resonant cavity structure in an embodiment of the present invention;

[0027] Figure 3 , a schematic diagram of the top view of the structure of a high-efficiency micro-ring acousto-optic modulator based on heterogeneous integration of silicon-silicon dioxide substrate / sapphire-silicon dioxide substrate in an embodiment of the present invention.

[0028] Reference numerals:

[0029] 1-sapphire substrate; 2-silicon substrate; 3-silicon dioxide layer; 4-lithium niobate thin film; 5-chalcogenide glass; 6-interdigitated transducer; 7-acoustic tapered transition region; 8-optical tapered transition region; 9-grating coupler; 10-optical waveguide; 11-subwavelength acoustic waveguide; 12-microring resonator. DETAILED DESCRIPTION

[0030] The specific implementation of the present invention is described below in conjunction with examples:

[0031] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose that can be achieved by the present invention.

[0032] At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0033] Example 1:

[0034] The purpose of this embodiment is to provide a highly efficient microring acousto-optic modulator (AOM). The AOM, based on a sapphire-silicon dioxide substrate, exploits the smaller size of surface acoustic wave-like modes on the sapphire substrate. The AOM, based on a silicon-silicon dioxide substrate, utilizes the excellent CMOS process compatibility and high refractive index contrast of the silicon-silicon dioxide substrate, as well as the excellent photoelastic properties of the chalcogenide glass. Both embodiments demonstrate the high electromechanical coupling coefficient and the ease with which Love-like waves are excited by the X-cut, Y-transmitted lithium niobate. The acoustic waves excited by the interdigital transducer 6 are coupled into the subwavelength acoustic waveguide 11 through a tapered region. The acoustic waves confined by the subwavelength acoustic waveguide 11 are further coupled into the microring resonant cavity 12. External laser light is coupled into the optical waveguide 10 through the grating coupler 9 and the optical tapered transition region 8, where it further couples with the microring resonant cavity 12, forming an optical resonant mode with a high quality factor.

[0035] This embodiment further introduces an intermodal scattering mechanism into the aforementioned acousto-optic resonance structure. Through the precise design and matching of the subwavelength acoustic waveguide and the microring resonator, the acoustic wave field drives efficient energy conversion and coupling between optical modes of different orders, thereby achieving inter-optical mode scattering. This intermodal scattering not only enhances the interaction between light and acoustic waves but also enables nonreciprocal optical transmission, frequency conversion, and mode selection, providing the device with higher modulation efficiency and flexibility.

[0036] In summary, this embodiment first solves the problem of difficulty in coupling quasi-surface acoustic waves to the subwavelength acoustic waveguide 11; secondly, the tapered transition zone improves the coupling efficiency of the acoustic waves excited by the interdigital transducer 6, thereby improving the utilization rate of acoustic energy; and at the same time, combined with the principle of intermodal scattering, further enhances the interaction strength between acoustic waves and optical waves, significantly improving the problems of insufficient acoustic-optical interaction and low conversion efficiency in traditional acousto-optic modulators, thereby realizing a high-efficiency, low-power, high-modulation-depth microring acousto-optic modulator with broad practical application prospects.

[0037] like Figure 1 、 3 As shown, this embodiment provides a high-efficiency micro-ring acousto-optic modulator with heterogeneous integration based on silicon-silicon dioxide / sapphire-silicon dioxide as a substrate, comprising: a substrate, wherein the substrate comprises a silicon substrate 2 / sapphire substrate 1, and a silicon dioxide layer 3 disposed on the silicon substrate 2 / sapphire substrate 1; a lithium niobate-chalcogenide glass heterogeneous layer is disposed on the substrate, wherein the lithium niobate-chalcogenide glass heterogeneous layer comprises a lithium niobate film 4 and a chalcogenide waveguide 5 heterogeneously integrated on the lithium niobate film, as shown in FIG. Figure 1 The lithium niobate film 4 includes two pairs of etched transduction regions, and an interdigital transducer 6 is provided on the transduction region; the chalcogenide waveguide 5 heterogeneously integrated on the lithium niobate film includes acoustic / optical tapered transition regions 7, 8, two pairs of grating couplers 9, two pairs of optical waveguides 10, two pairs of subwavelength acoustic waveguides 11 and a microring resonator 12, wherein the subwavelength acoustic waveguide 11 is connected to the transduction region through the etched acoustic tapered transition region 7, the optical waveguide 10 is connected to the grating coupler 9 through the optical tapered transition region 8, and the microring resonator 12 is point-coupled with the subwavelength acoustic waveguide 11 and the optical waveguide 10, as shown in FIG. Figure 3 .

[0038] The transduction region is formed by etching a lithium niobate thin film 4, while the tapered transition region, grating coupler 9, optical waveguide 10, subwavelength acoustic waveguide 11, and microring resonator 12 are all etched from the same chalcogenide glass 5. The silicon substrate 1 is formed of silicon or sapphire, and the silicon dioxide layer 3 disposed on the silicon substrate 2 / sapphire substrate 1 is formed of silicon dioxide.

[0039] Specifically, the interdigital transducer 6, the tapered transition regions (7, 8), the grating coupler 9, the optical waveguide 10, the subwavelength acoustic waveguide 11, and the microring resonator cavity 12 are all in a non-suspended state relative to the substrate.

[0040] like Figure 2The microring resonator is composed of two pairs of optical waveguides 10, two pairs of subwavelength acoustic waveguides 11, and a microring resonant cavity 12. The waveguide parameters of the optical waveguides 10, subwavelength acoustic waveguides 11, and microring resonant cavity 12 are consistent. The coupling spacing between the optical waveguides 10 and the microring resonant cavity 12 is 300nm to 1000nm, the coupling spacing between the subwavelength acoustic waveguides 11 and the microring resonant cavity 12 is 300nm to 1000nm, the radius of the microring resonant cavity 12 is 20 to 50 acoustic wavelengths, and the bending radius of the curved waveguide portion of the optical waveguide is 15 to 45 acoustic wavelengths.

[0041] The radio frequency signal is converted into an acoustic wave by the interdigital transducer 6, and the interdigital transducer 6 converts the electrical signal into a surface acoustic wave through the piezoelectric effect of the lithium niobate film 4, and propagates along the acoustic waveguide 11 through the etched acoustic tapered transition region 7. The external laser is coupled into the optical tapered transition region 8 through the grating coupler 9 and propagates along the optical waveguide 10.

[0042] When an acoustic wave propagates through the subwavelength acoustic waveguide 11 and enters the microring resonator 12, the refractive index modulation induced by the acoustic wave in the medium drives intermodal scattering between different-order optical modes in the microring, thereby effectively transferring energy from the fundamental mode to higher-order modes. This intermodal scattering process enhances the acousto-optic interaction, enabling modal conversion, frequency conversion, and nonreciprocal transmission of optical signals, further enhancing the functional versatility and system flexibility of the modulator. Furthermore, by adjusting the geometric and material parameters of the subwavelength acoustic waveguide 11 and the microring resonator 12, as well as the acoustic wave frequency, the intermodal scattering intensity can be optimized, further improving the efficiency of acousto-optic modulation.

[0043] The width of the transducer zone should not be set too wide, as the Rayleigh-like waves and Love-like waves excited by such a wide transducer zone are not easy to couple with the subwavelength acoustic waveguide 11; similarly, the width of the transducer zone should not be too narrow, as such a narrow transducer zone is not easy to achieve impedance matching of microwaves, resulting in low conversion efficiency of microwaves to sound waves.

[0044] In particular, the surface acoustic wave-like waves excited by the interdigital transducer 6 here are similar to surface acoustic waves, both of which propagate on the surface of the medium. The difference is that since the subwavelength acoustic waveguide 11 can achieve a strong bound state for the sound waves, the surface acoustic wave-like waves are used to distinguish the guided propagation of the bound state from the diffusive surface acoustic waves that propagate in a single direction.

[0045] The lithium niobate film 4 is tangentially oriented in an XY or X-(θ)Y direction. Leveraging the high electromechanical coupling coefficient of lithium niobate in this XY direction, the microwave-to-acoustic conversion efficiency is improved, while simultaneously generating relatively pure Love- and Rayleigh-like waves. X-(θ)Y indicates that the acoustic wave propagates counterclockwise along the Y-axis of the lithium niobate crystal, rotating θ degrees counterclockwise. Conversely, the clockwise direction indicates negative θ degrees, expressed as X-(-θ)Y, where θ is typically 30° to 90°.

[0046] The thickness of the lithium niobate film 4 is 200nm to 1000nm, the thickness of the corresponding chalcogenide glass 5 is 500nm to 1000nm, the width of the transduction region is 0.01μm to 20μm, the finger width of the interdigital transducer 6 is 0.2μm to 5μm, the number of interdigital pairs is 20 to 100 pairs, and the interdigital transducer 6 can achieve the excitation of 300MHz to 8GHz Rayleigh-like waves and Love-like waves; the size of the subwavelength acoustic waveguide 11 is smaller than the working acoustic wavelength, and its width is 500nm to 1500nm; the thickness of the optical waveguide 10 is consistent with that of the subwavelength acoustic waveguide 11.

[0047] The working principle of the efficient micro-ring acousto-optic modulator is as follows:

[0048] Based on the inverse piezoelectric effect of the lithium niobate film 4, the input microwave modulation signal is converted into an acoustic wave signal on the surface of the lithium niobate film 4 through the interdigital transducer 6, so that a periodic mechanical strain field distribution is formed in the lithium niobate film 4. The mechanical acoustic waves generated on the surface of the lithium niobate film 4 are efficiently coupled to the subwavelength acoustic waveguide 11 through the acoustic conical transition zone 7. The acoustic wave types here mainly include Rayleigh-like waves and Love-like waves, both of which have transverse wave characteristics, that is, the particle vibration direction is perpendicular to the wave propagation direction. Due to the strong confinement characteristics in the subwavelength acoustic waveguide 11, this type of acoustic wave can effectively form a localized acoustic field and be well guided into the microring resonant cavity 12. For the optical mode, the external laser is coupled into the optical conical transition zone 8 through the grating coupler 9, propagates along the optical straight waveguide 10 to its curved part, and effectively couples with the microring resonant cavity 12. In the microring resonant cavity 12, the acoustic field and the optical field are resonantly coupled, and the acoustic wave forms a periodic strain field in the microring area. Based on the photoelastic effect, the refractive index distribution of the material in the microring is modulated, thereby modulating the optical field. The optical resonant mode therefore carries the acoustic wave signal excited by the radio frequency signal, thereby completing the effective modulation of the electrical signal to the optical signal. Furthermore, when the acoustic field modulates the optical field in the microring resonant cavity 12, in addition to changing the frequency or phase of a single optical mode, it can also induce intermodal scattering between optical modes of different orders, thereby enhancing the interaction. Specifically, the periodic refractive index modulation formed by the acoustic field provides momentum matching conditions between different modes, realizing energy exchange between the fundamental mode and the higher-order modes. This intermodal scattering not only enhances the interaction strength between the optical field and the acoustic field, but also enables the acousto-optic modulator of the present invention to have functional expansion capabilities such as mode conversion, frequency conversion, and non-reciprocal optical transmission, significantly improving the application flexibility and integration potential of the device.

[0049] This embodiment designs two pairs of bidirectional optical waveguides and subwavelength acoustic waveguides and grating couplers, which can flexibly control the propagation direction of acoustic and light waves to achieve common propagation or counter-propagation, facilitating the exploration of the system's time reversal symmetry, optical reciprocity, and non-reciprocal properties. The introduced inter-mode scattering mechanism enhances the acoustic-optical interaction capability within the microring cavity, effectively improving the conversion and processing efficiency of acoustic-optical information. The device uses a sapphire substrate, which improves the quality factor and propagation stability of the acoustic wave mode due to its high mechanical strength, high sound velocity, and low acoustic loss characteristics; its excellent thermal matching and process compatibility also support high-quality heterogeneous integration with silicon dioxide and lithium niobate films. Furthermore, the use of high-refractive-index, low-optical-loss sulfur-based waveguide materials enhances the spatial overlap and coupling strength of the photoacoustic mode field, and effectively suppresses interface scattering losses. The above structural optimization significantly improves the optical, acoustic, and mechanical properties of the device, providing a solid foundation for the realization of efficient, stable, and easily integrated microring acousto-optic modulators.

[0050] Example 2:

[0051] This embodiment 2 is applied to the embodiment 1, such as Figure 3 As shown, in this embodiment, a high-efficiency microring acousto-optic modulator based on a sapphire-silicon dioxide substrate operating at a microwave frequency of 3.985 GHz is provided. The modulator primarily comprises two pairs of interdigital transducers 6 formed by etching a lithium niobate thin film 4, two pairs of acoustic / optical tapered transition regions (7, 8) formed by etching a chalcogenide glass 5, two pairs of grating couplers 9, two pairs of optical waveguides 10, two pairs of subwavelength acoustic waveguides 11, and a microring resonant cavity 12. The transduction region where the interdigital transducers 6 are located has a width of approximately 20.7 μm and a transducer period of approximately 691 nm, capable of exciting Rayleigh-like waves near 4.01 GHz. Furthermore, the widths of the optical waveguides 10 and the subwavelength acoustic waveguides 11 are 800 nm, the coupling spacing between the optical waveguides 10 and the microring resonant cavity 12 is 350 nm, and the coupling spacing between the subwavelength acoustic waveguides 11 and the microring resonant cavity 12 is 400 nm. Ultimately, optical resonance will occur at a wavelength of 1553nm and acoustic resonance will occur at 4.01GHz.

[0052] Example 3:

[0053] This embodiment 3 is applied to the embodiment 1, such as Figure 3 As shown, in this embodiment, a high-efficiency microring acousto-optic modulator based on a silicon-silicon dioxide substrate operating at a microwave frequency of 1.97 GHz is provided. The modulator primarily comprises two pairs of interdigital transducers 6 formed by etching a lithium niobate thin film 4, two pairs of acoustic / optical tapered transition regions (7, 8) formed by etching a chalcogenide glass 5, two pairs of grating couplers 9, two pairs of optical waveguides 10, two pairs of subwavelength acoustic waveguides 11, and a microring resonant cavity 12. The transduction region where the interdigital transducers 6 are located has a width of approximately 64.8 μm, a transducer period of approximately 3.2 μm, and can excite Rayleigh-like waves near 1.5 GHz. Furthermore, the cross-sectional width of the optical waveguide 10 and the subwavelength acoustic waveguide is approximately 1000 nm, and the coupling spacing with the microring resonant cavity 12 is 500 nm. The coupling spacing between the subwavelength acoustic waveguide 11 and the microring resonant cavity 12 is 400 nm. Ultimately, optical resonance will occur at a wavelength of 1562nm and acoustic resonance will occur at 1.97GHz.

[0054] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

[0055] Many other changes and modifications can be made without departing from the spirit and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. An efficient microring acousto-optic modulator, characterized in that: The invention comprises a substrate, wherein the substrate comprises: a substrate and a silicon dioxide layer (3) arranged thereon; a lithium niobate-chalcogenide glass heterogeneous layer is arranged on the silicon dioxide layer (3); the heterogeneous layer comprises a lithium niobate film (4) and a chalcogenide glass (5) integrated on the lithium niobate film (4); Two pairs of transduction regions are provided on the lithium niobate film (4), and an interdigital transducer (6) is provided on the transduction region; two pairs of acoustic and optical tapered transition regions, two pairs of grating couplers (9), two pairs of optical waveguides (10), two pairs of subwavelength acoustic waveguides (11), and a microring resonant cavity (12) are formed in the chalcogenide glass (5); two ends of the subwavelength acoustic waveguide (11) are connected to the interdigital transducers (6) through the acoustic tapered transition regions (7), and two ends of the optical waveguide (10) are connected to the grating coupler (9) through the optical tapered transition regions (8); and acousto-optic modulation is achieved among the microring resonant cavity (12), the subwavelength acoustic waveguide (11), and the optical waveguide (10) through point coupling.

2. The high-efficiency microring acousto-optic modulator according to claim 1, characterized in that: The energy conversion region is formed by etching a lithium niobate film (4), and the tapered transition region, the grating coupler (9), the optical waveguide (10), the subwavelength acoustic waveguide (11) and the microring resonant cavity (12) are all formed by etching the same chalcogenide glass (5). The substrate is a sapphire substrate (1) or a silicon substrate (2). The acoustic mode in the subwavelength acoustic waveguide (11) is a bound state surface acoustic wave mode, and the acoustic wave is in a resonant state. The thickness of the sapphire substrate (1) or the silicon substrate (2) is 1 μm to 800 μm, the thickness of the silicon dioxide layer (3) in the silicon-silicon dioxide substrate is 500 nm to 4000 nm, the thickness of the silicon dioxide layer (3) in the sapphire-silicon dioxide substrate is 0 nm to 4000 nm, the thickness of the lithium niobate film (4) is 200 nm to 1000 nm, and the thickness of the chalcogenide glass (5) is 500 nm to 1500 nm.

3. The high-efficiency microring acousto-optic modulator according to claim 1, characterized in that: The microring resonator is composed of two pairs of optical waveguides (10), two pairs of subwavelength acoustic waveguides (11) and a microring resonant cavity (12); the waveguide widths of the optical waveguides (10), the subwavelength acoustic waveguides (11) and the microring resonant cavity (12) are all between 500 nm and 1500 nm; The coupling spacing between the optical waveguide (10) and the microring resonant cavity (12) is 300nm to 1000nm, the coupling spacing between the subwavelength acoustic waveguide (11) and the microring resonant cavity (12) is 300nm to 1000nm, the circumference of the microring resonant cavity (12) is designed to be an integer multiple of the acoustic wavelength, the radius of the microring resonant cavity (12) is 20 to 50 acoustic wavelengths, and the bending radius of the curved waveguide portion of the optical waveguide is 15 to 45 acoustic wavelengths; inter-mode scattering occurs between the acoustic wave in the microring resonant cavity (12) and optical modes of different orders, and the effective refractive index modulation between adjacent optical modes in the microring resonant cavity is excited by the acoustic wave, thereby realizing energy exchange and coupling between different optical modes, thereby enhancing acousto-optic interaction and improving acousto-optic modulation efficiency and modulation depth.

4. The high-efficiency microring acousto-optic modulator according to claim 1, characterized in that: The tangent direction of the lithium niobate film (4) is X-cut, Y-cut or Z-cut for the interdigital transducer (6), the width of the transducer region is 0.01 μm to 20 μm, the finger width of the interdigital transducer (6) is 0.2 μm to 5 μm, the number of interdigital pairs is 20 to 300 pairs, and the interdigital transducer (6) is used to achieve the excitation of 300 MHz to 8 GHz Rayleigh-like modes and Love-like modes.

5. The high-efficiency microring acousto-optic modulator according to claim 1, characterized in that: The chalcogenide glass material has a lower acoustic velocity and acoustic impedance than the lithium niobate film (4); the difference in acoustic impedance between the chalcogenide glass (5) and the lithium niobate film (4) forms an acoustic wave reflection interface, thereby achieving effective confinement of acoustic waves in the chalcogenide waveguide; this structure effectively suppresses the radiation loss of acoustic waves, improves the acoustic mode quality factor (Q factor) and the overlap of the acousto-optic mode, thereby improving the acousto-optic coupling efficiency; and can achieve high mode field confinement and high modulation efficiency while realizing subwavelength acoustic mode transmission, thereby providing strong support for the high performance and miniaturization of the integrated acousto-optic modulator.

6. A method for operating a microring acousto-optic modulator, characterized in that: The method comprises: based on the inverse piezoelectric effect of the lithium niobate film (4), converting the input microwave modulation signal into an acoustic wave signal on the surface of the lithium niobate film (4) through an interdigital transducer (6), so that a periodic mechanical strain field distribution is formed in the lithium niobate film (4); the mechanical acoustic wave generated on the surface of the lithium niobate film (4) is efficiently coupled to the subwavelength acoustic waveguide (11) through the acoustic conical transition zone (7), wherein the acoustic wave types include Rayleigh-like waves and Love-like waves, both of which have transverse wave characteristics, that is, the particle vibration direction is perpendicular to the wave propagation direction. Due to the strong confinement characteristics of this type of acoustic wave in the subwavelength acoustic waveguide (11), the localized The acoustic field is well guided into the microring resonant cavity (12); for the optical mode, the external laser is coupled into the optical tapered transition region (8) through the grating coupler (9), propagates along the optical straight waveguide (10) to its curved part, and is effectively coupled with the microring resonant cavity (12); in the microring resonant cavity (12), the acoustic field and the optical field are resonantly coupled, and the acoustic wave forms a periodic strain field in the microring region, modulating the refractive index distribution of the material in the microring based on the photoelastic effect, thereby modulating the light field. Therefore, the optical resonant mode carries the acoustic wave signal excited by the radio frequency signal, thereby completing the effective modulation of the electrical signal to the optical signal.

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