Non-resonant recyclable integrated acousto-optic modulator

Abstract

The invention discloses a non-resonant recyclable integrated acousto-optic modulator which has a high-order controllable mode light modulation capability. According to the device, a lithium niobate-chalcogenide glass heterogeneous layer is constructed based on a silicon-silicon dioxide substrate, and the device comprises a lithium niobate film and a heterogeneous integrated chalcogenide waveguide. A multi-mode light field is formed through waveguide conical transition, and coupling of an annular loop and a multi-mode waveguide is realized by means of an asymmetric directional coupler, so that high-order mode light circulates in a modulation area, and multi-time modulation is realized. According to the structure, the modulation efficiency can be improved and the required microwave power can be reduced through a high-order mode on the premise that the interaction length is not increased. The device is compact in structure, simple in process and suitable for the fields of optical communication, photon calculation, signal processing and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of integrated optics, and particularly relates to a non-resonant recyclable integrated acousto-optic modulator. BACKGROUND

[0002] High-performance integrated acousto-optic modulators play an increasingly key role in microwave photonics, on-chip optical communication and reconfigurable photonic circuits. By regulating the interaction between phonons and photons, it dynamically changes the effective refractive index in the waveguide, thereby achieving precise modulation of the optical field. With the rapid growth of data transmission rate and bandwidth demand, traditional modulators gradually reveal bottlenecks in size, modulation efficiency and power consumption, and new structural paradigms are urgently needed to break through the existing limitations. In particular, in the integrated acousto-optic modulator device, how to improve the modulation depth and reduce the driving power without sacrificing the bandwidth has become a research focus.

[0003] Non-resonant modulators have wider modulation bandwidth and stronger frequency tolerance due to their independence on fixed frequency conditions, and have become an important development direction in the field of high-frequency dynamic regulation. On this basis, the use of optical feedback structure realizes cyclic modulation, which can significantly improve the effective light-phonon interaction length without increasing the size of the device, thereby enhancing the modulation depth and energy efficiency ratio. By coupling the first modulated optical signal back to the modulation region and re-entering it in different modes (such as TE0 to TE n , n≥1), equivalent multiple modulation can be achieved, and a "non-resonant and recyclable" acousto-optic enhancement mechanism is constructed. This mechanism not only simplifies the frequency matching requirement in the resonant structure, but also shows significant advantages in reducing RF power consumption and improving sideband strength. The mode conversion, optical path control and phase compensation design in this process ensure the light-phonon phase matching between the two modulations, so as to achieve a resonant-like modulation enhancement effect without using a resonant cavity. The entire structure fully utilizes the path construction advantages of single-mode-multimode-ring, realizes the superposition and enhancement of intermodal modulation, and has good structural stability and modulation uniformity.

[0004] The recyclable acousto-optic modulator based on the silicon-silicon dioxide substrate and thin film lithium niobate-sulfur glass hetero-integrated platform has dual advantages of material performance and structural innovation. Thin film lithium niobate (TFLN) provides high piezoelectric response and low loss waveguide environment, and sulfur glass (ChG) significantly enhances the light-phonon coupling efficiency with its high photoelastic coefficient. In terms of structure, the device uses single-mode to multi-mode waveguide transition design, and forms a controllable feedback path with an asymmetric directional coupler, so that the optical field realizes cyclic transmission and continuous modulation between different modes. This design effectively improves the modulation efficiency while retaining the bandwidth flexibility and process compatibility of the non-resonant structure, and is particularly suitable for application in high-speed, low-power and programmable on-chip photonic systems.

[0005] In summary, the integrated acousto-optic modulator based on a non-resonant cyclic modulation mechanism, combined with mode control and loop enhancement structures, provides a practical technical solution for improving modulation depth, reducing power consumption, and minimizing size. Compared to traditional single-pass modulators, this structure achieves a higher modulation index with the same electrode size and significantly reduces the required microwave power. Its design concept is applicable to key application scenarios such as next-generation high-density integrated photonic chips, photonic neural networks, non-reciprocal modulators, and optical frequency comb systems, demonstrating broad development prospects and application potential. Summary of the Invention

[0006] In order to solve the technical problems existing in the background art, the present invention aims to provide a non-resonant cyclic integrated acousto-optic modulator, which adopts a lithium niobate thin film and a chalcogenide glass heterogeneous integrated waveguide structure, and combines inter-mode switching and waveguide loop path to realize multiple non-resonant enhancement modulation of optical signals in the modulation region, so as to improve the intensity of acousto-optic interaction and modulation efficiency, reduce RF drive power, and meet the development needs of high-speed, low-power, on-chip integrated acousto-optic control devices.

[0007] To solve the technical problem, the technical solution of the present invention is as follows:

[0008] A non-resonant cyclic integrated acousto-optic modulator includes a substrate, the substrate including a silicon substrate and a silicon dioxide layer disposed on the silicon substrate, a lithium niobate-chalcogenide glass heterostructure layer disposed on the silicon dioxide layer, the lithium niobate-chalcogenide glass heterostructure layer including a lithium niobate thin film and a chalcogenide waveguide heterostructure integrated on the lithium niobate thin film;

[0009] The lithium niobate thin film is etched to form a transducer region, and an interdigital transducer is disposed on the transducer region. The chalcogenide waveguide sequentially includes: a single-mode optical waveguide, a first optical tapered transition region, a multimode optical waveguide, an asymmetric directional coupler, and a ring loop waveguide. The single-mode optical waveguide is connected to one end of the multimode optical waveguide through the first optical tapered transition region, and the other end of the multimode optical waveguide is coupled to the ring loop waveguide through the asymmetric directional coupler. A second optical tapered transition region is also provided between the multimode optical waveguide and the ring loop waveguide for mode transition and guiding the light wave back to the modulation region, thereby realizing mode conversion and cyclic modulation of the optical signal.

[0010] Furthermore, the asymmetric directional coupler is distributed between the multimode optical waveguide and the loop waveguide, converting the TEO mode light wave propagating in the multimode optical waveguide into a higher-order transverse electric mode (TE) through mode-selective coupling. n (n≥1), and guide it into the ring loop waveguide to realize the feedback path of the optical signal. The feedback optical wave can return to the modulation region again and perform subsequent acousto-optic modulation with the acoustic field.

[0011] Furthermore, its signal modulation process includes:

[0012] An external laser is injected through a single-mode optical waveguide, passes through the first optical conical transition region, and enters a multimode optical waveguide. In the TE0 mode, it first interacts with the acoustic field in the modulation region. When the TE0 mode light wave propagates to the end of the multimode optical waveguide, it undergoes mode conversion to TE1 or TE2 mode via an asymmetric directional coupler. The mode-converted light wave is coupled into the loop waveguide via the asymmetric directional coupler, forming an optical feedback path in the loop. It then re-enters the modulation region in the feedback mode, completing the second or multiple acousto-optic modulations and achieving non-resonant cyclic modulation enhancement.

[0013] Furthermore, the interdigital transducer, single-mode optical waveguide, optical tapered transition region, asymmetric directional coupler, multimode optical waveguide, and ring loop waveguide are all in a non-suspended state relative to the substrate.

[0014] Furthermore, the single-mode optical waveguide, multi-mode optical waveguide, and ring loop waveguide all have a width of 925nm~3230nm. The optical path length of the ring loop waveguide is designed to be an integer multiple of 2π of the optical phase change, and the radius of the curved waveguide in the loop is 120um.

[0015] Furthermore, the coupling spacing between the ring-loop waveguide and the multimode optical waveguide is 400 nm, and the coupling length of the asymmetric directional coupler is 210 μm to 376 μm.

[0016] Furthermore, the lithium niobate film is tangentially XZ-oriented relative to the interdigital transducer; the interdigital transducer has a finger width of 500 nm, an aperture of 120 μm, and 85 to 130 interdigital pairs; its distance from the waveguide is 5 μm to 8.3 μm. The interdigital transducer is used to excite Rayleigh-like and Love-like waves in the frequency range of 300 MHz to 8 GHz. The lithium niobate film has a thickness of 400 nm, the silicon dioxide layer has a thickness of 0 to 2000 nm, and the chalcogenide waveguide has a thickness of 925 nm to 3230 nm. The interdigital transducer is suitable for high-order transverse electric modes (TE). n The refractive index modulation efficiency of the multimode (n≥1) is higher than that of the fundamental mode (TE0); the ring-loop waveguide is a closed optical path structure, configured to recouple the modulated residual higher-order mode optical field to the input end of the multimode optical waveguide, so as to realize the recycling of optical energy and modulation enhancement.

[0017] Furthermore, the lateral dimension of the multimode optical waveguide is optimized and determined by the following conditions: the characteristic frequency corresponding to the maximum refractive index change caused by the acousto-optic interaction in the multimode optical waveguide is equal to the characteristic frequency corresponding to the minimum value of the S11 curve of the interdigital transducer. Based on this frequency matching condition, its lateral dimension range is determined to be 925nm~1020nm; the lateral dimension of the single-mode optical waveguide is determined to be 1950nm~3230nm according to the single-mode transmission conditions and the mode field matching requirements with the multimode optical waveguide.

[0018] Furthermore, one end of the ring-loop waveguide is coupled to a multimode optical waveguide via an asymmetric directional coupler to receive TE1 or TE2 mode light waves converted from TE0 mode light waves in the multimode optical waveguide. The ring-loop waveguide consists of a straight waveguide and a curved waveguide, forming a closed light propagation path. Its total length is designed to be an integer multiple of 2π for optical phase change to achieve stable phase feedback. The bending radius of the curved waveguide is 120 μm to reduce light loss during curved propagation. The other end of the ring-loop waveguide is connected to the multimode optical waveguide via a second optical conical transition region to guide the feedback light wave back to the modulation region, realizing the cyclic return and remodulation of the optical signal. Utilizing the ring-loop waveguide structure, the light wave can interact with the acoustic field multiple times in the modulation region, thereby achieving a non-resonant cyclic modulation mechanism without relying on a resonant structure, significantly improving modulation depth and energy efficiency.

[0019] The overall ring-shaped waveguide is designed to be relatively short, allowing the lateral dimensions of the overall device to be controlled within the range of 3361nm to 3861nm. This minimizes the propagation delay of light in the ring path, increases the range of possible superimposed modulation frequencies, and forms multiple modulations under the same approximately equivalent sound field, thereby achieving enhanced superposition of high-frequency modulation depth. The device can be fabricated as a single-loop structure with the fundamental mode to a single higher-order mode, or as a multi-loop structure with the fundamental mode to multiple higher-order modes.

[0020] Compared with the prior art, the advantages of the present invention are as follows:

[0021] The non-resonant cyclic integrated acousto-optic modulator provided by the present invention is disposed on a silicon-silicon dioxide substrate and consists of an interdigital transducer, a single-mode optical waveguide, an optical tapered transition region, an asymmetric directional coupler, a multimode optical waveguide, and a loop circuit.

[0022] First, silicon is used as the substrate material and XZ lithium niobate film is used as the piezoelectric material. Taking advantage of the large contrast between the sound velocity of silicon and lithium niobate and silicon dioxide, the sound wave propagation loss is low, which supports higher frequency (GHz level) acousto-optic modulation.

[0023] Second, by using chalcogenide dielectrics as waveguide materials and optimizing the ChG waveguide structure to reduce sidewall scattering loss and enable mode matching, silicon as the substrate material exhibits unique advantages in large-scale integration, cost control, and CMOS compatibility.

[0024] Third, the radio frequency signal is converted into an acoustic wave through the IDT. The IDT converts the electrical signal into a surface acoustic wave through the piezoelectric effect of the lithium niobate film. The acoustic wave forms a periodic strain field in the multimode waveguide region, modulates the refractive index through the photoelastic effect, and causes physical deformation of the waveguide through the moving boundary effect.

[0025] Fourth, by constructing a coupling path from single-mode to higher-order mode to multi-mode, the TE0 mode is injected and initially modulated in the main modulation region. Then, through a feedback loop via the coupling structure, it re-enters the modulation region in TE1 or TE2 mode, achieving a non-resonant, multi-phase modulation enhancement mechanism. This effectively increases the modulation depth and reduces driving power consumption without relying on resonant cavity conditions. Compared to traditional single-modulation devices, this structure achieves an equivalent double or triple effective interaction length, significantly improving acousto-optic conversion efficiency.

[0026] Fifth, the optimized acousto-optic modulator is insensitive to the coupling conditions of acoustic waves, has a wide operating range, 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 type IDT described in this invention.

[0027] The aforementioned acousto-optic modulator has significant advantages such as compact structure, high modulation efficiency, low power consumption, and strong scalability. It is suitable for multiple integrated photonics applications, including high-speed optical communication, optical frequency comb generation, non-reciprocal device design, and on-chip signal processing, and has broad prospects for technology promotion and industrialization. Attached Figure Description

[0028] Figure 1 Cross-sectional views of a waveguide based on a silicon-silicon dioxide substrate and a lithium niobate-chalcogenide glass heterolayer layer disposed on the substrate in the embodiments of the present invention;

[0029] Figure 2 A top view schematic diagram of the non-resonant cyclic integrated acousto-optic modulator based on heterogeneous integration of silicon-silicon dioxide substrate in an embodiment of the present invention.

[0030] Figure Labels

[0031] 1-Silicon substrate; 2-Silicon dioxide layer; 3-Lithium niobate thin film; 4-Chalcogenide glass; 5-Interdigital transducer; 6-Single-mode optical waveguide; 7-Optical tapered transition region; 8-Asymmetric directional coupler; 9-Multimode optical waveguide; 10-Ring circuit. Detailed Implementation

[0032] The specific implementation of the present invention is described below with reference to embodiments:

[0033] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0034] Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0035] Example 1:

[0036] The purpose of this invention is to provide a non-resonant, cyclic integrated acousto-optic modulator, based on a silicon-silica substrate thin-film lithium niobate-chalcogenide glass heterostructure integrated acousto-optic modulator. It utilizes the excellent CMOS process compatibility and high refractive index contrast of the silicon-silica substrate, as well as the excellent photoelastic properties of chalcogenide glass. Both exhibit the high electromechanical coupling coefficient and easy excitation of Love waves characteristic of lithium niobate. A single-mode optical waveguide 6 guides the input TE0 mode optical signal, which is widened by an optical tapered transition region 7 to a multimode optical waveguide 9 supporting TE1 or TE2 modes. The acoustic wave excited by the interdigital transducer 5 enters the multimode optical waveguide 9, achieving acousto-optic modulation for the first time in the multimode waveguide modulation region. Subsequently, the optical signal is introduced into the loop waveguide and, during transmission, is converted to TE1 or TE2 mode via an asymmetric directional coupler 8, returning to the main modulation region to complete a second modulation.

[0037] In the aforementioned acousto-optic modulation structure, this invention addresses the problems of limited acousto-optic interaction length, insufficient modulation depth, and low energy utilization efficiency in traditional single-pass acousto-optic modulation structures by proposing a non-resonant cyclic acousto-optic modulator structure based on a modal selective feedback mechanism. By introducing a multi-stage cyclic modulation path for optical modes and combining it with an asymmetric directional coupler, a non-resonant enhancement mechanism for TE0 mode injection and TE1 / TE2 mode feedback modulation is achieved. Without relying on cavity resonance conditions, this effectively improves modulation efficiency, reduces power consumption, expands the structural flexibility and frequency adaptation range of the device, and exhibits good bandwidth robustness and system compatibility.

[0038] In summary, the cyclic non-resonant acousto-optic modulation mechanism proposed in this invention significantly improves the interaction efficiency of sound waves and light waves in chalcogenide waveguide structures, overcoming the challenges of limited modulation depth, non-reentrancy of the structure, and limited response rate in traditional acousto-optic modulators. By precisely controlling the optical loop length and mode coupling method, it achieves multiple modulations, multi-mode conversion, and energy redistribution in a miniaturized platform, ultimately achieving the goal of efficient, low-power, and high-phase-control-precision integrated acousto-optic modulation, demonstrating broad engineering application prospects and industrialization value.

[0039] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] like Figure 1 As shown, the present invention provides a heterogeneously integrated non-resonant cyclic integrated acousto-optic modulator based on a silicon-silica substrate, comprising: a substrate, the substrate including a silicon substrate 1 and a silicon dioxide layer 2 disposed on the silicon substrate 1; a lithium niobate-chalcogenide glass heterogeneous layer disposed on the substrate, the lithium niobate-chalcogenide glass heterogeneous layer including a lithium niobate thin film 3 and a chalcogenide waveguide 4 heterogeneously integrated on the lithium niobate thin film, such as... Figure 1 The lithium niobate thin film 3 includes an etched transducer region, on which an interdigital transducer 5 is disposed; the heterogeneously integrated chalcogenide waveguide 4 on the lithium niobate thin film includes a single-mode optical waveguide 6, an optical tapered transition region 7, an asymmetric directional coupler 8, a multimode optical waveguide 9, and a ring loop 10. The single-mode optical waveguide 6 and the multimode optical waveguide 9 are connected through the optical tapered transition region 7, and the ring loop 10 and the multimode optical waveguide 9 are coupled through the asymmetric directional coupler 8, as shown below. Figure 2 As shown.

[0041] The lithium niobate thin film 3 in the transducer region is etched, and the single-mode optical waveguide 6, optical tapered transition region 7, asymmetric directional coupler 8, multimode optical waveguide 9, and ring circuit 10 are all etched from the same chalcogenide glass 4. The silicon substrate 1 is formed of silicon, and the silicon dioxide layer 2 disposed on the silicon substrate 1 is made of silicon dioxide.

[0042] Specifically, the interdigital transducer 5, single-mode optical waveguide 6, optical conical transition region 7, asymmetric directional coupler 8, multimode optical waveguide 9, and ring circuit 10 are all in a non-suspended state relative to the substrate.

[0043] For example, such as Figure 2As shown, the ring circuit consists of a straight waveguide and a curved waveguide. The length of the ring circuit is designed to be an integer multiple of 2π of the optical phase change, and the radius of the curved waveguide in the circuit is 120 μm. The coupling distance between the ring circuit and the multimode optical waveguide 9 is 400 nm, and the coupling length of the asymmetric directional coupler 8 is 210 μm to 376 μm.

[0044] The radio frequency signal is converted into an acoustic wave through the interdigital transducer 5. The interdigital transducer 5 converts the electrical signal into a surface acoustic wave through the piezoelectric effect of the lithium niobate thin film 3, which propagates perpendicular to the multimode optical waveguide 9. The external laser passes through the single-mode optical waveguide 6 and gradually widens through the tapered transition region 7 before entering the multimode optical waveguide 9, that is, the TEO mode propagates for the first time in the modulation region.

[0045] The light wave passes through the optical conical transition region 7 and enters the ring loop 10, propagating backward within the loop. In the asymmetric directional coupler 8, the TE0 mode is converted to the TE1 or TE2 mode and coupled back to the modulation region, completing a second or more modulations. In the ring path, the light wave interacts with the acoustic field each time it returns to the modulation region, forming a non-resonant cyclic modulation mechanism. This mechanism utilizes the refractive index perturbation caused by acoustic modulation to drive the optical field to undergo phase superposition between different order modes such as TE0, TE1, and TE2. By controlling the optical path length and mode conversion path, equivalent multiple modulations and enhanced interference effects can be achieved, further improving the phase modulation depth and energy efficiency ratio, which helps to realize functions such as mode diversity, frequency conversion, and non-reciprocal transmission of optical signals. The waveguide width and coupling length of the asymmetric directional coupler must be strictly set to ensure the coupling efficiency of the fundamental mode to higher order modes.

[0046] In particular, the system can flexibly control and select optical modes by adjusting the waveguide width and coupling length of the directional coupler, optimize the non-resonant modulation superposition effect, further enhance the degree of freedom of control of the photoacoustic interaction region, and expand the functional integration and application range of the device.

[0047] The lithium niobate film 3 has a tangential orientation of XZ. Utilizing the high electromechanical coupling coefficient of lithium niobate with an XZ tangential orientation, the microwave-to-sound wave conversion efficiency is improved, while simultaneously obtaining relatively pure Love-like waves and pure Rayleigh-like waves. Here, XZ indicates a cut along the X-axis of the lithium niobate crystal, with the sound wave propagating along the Z-axis of the crystal.

[0048] The lithium niobate film 3 has a thickness of 400 nm, the chalcogenide glass 4 has a thickness of 950 nm to 3230 nm, the interdigital transducer 5 has a finger width of 500 nm, an aperture of 120 μm, and 85 to 130 interdigital pairs. The interdigital transducer 5 can achieve excitation of Rayleigh-like waves and Love-like waves from 300 MHz to 8 GHz.

[0049] The working principle of the aforementioned non-resonant cyclic integrated acousto-optic modulator is as follows:

[0050] Based on the piezoelectric coupling effect of the lithium niobate thin film 3, the input microwave modulation signal is converted into surface acoustic waves on the surface of the lithium niobate thin film through the interdigital transducer 5, resulting in a periodic mechanical strain field distribution along the propagation direction in the lithium niobate thin film 3. This strain field propagates perpendicular to the multimode optical wave 9, exciting Rayleigh-like or Love-like surface acoustic waves, forming a stable acoustic field with spatial locality and frequency selectivity in the modulation region. These acoustic waves can interact with the optical field propagating in the multimode optical waveguide, modulating the effective refractive index of the waveguide mode at the optical field location, thereby achieving phase modulation of the optical signal. For the optical modulation process, the external incident laser is first injected through the single-mode optical waveguide 6, enters the conical optical transition region 7, and gradually widens into the multimode optical waveguide 9, realizing the first propagation of the TE0 mode in the modulation region. When the light wave continues to pass through the conical transition region 7 and enters the ring loop 10, it propagates backward in the ring path. Through the asymmetric directional coupler 8, the TE0 mode is effectively converted into the higher-order TE1 or TE2 mode. Subsequently, the converted optical wave mode is coupled back to the modulation region, forming a new phase interference condition with the acoustic wave, completing the second modulation process. This structure allows the optical field to be cyclically modulated between different modes, enabling multi-level mode switching and phase accumulation, effectively improving the modulation depth. In this non-resonant cyclic structure, the optical field achieves enhanced modulation through mode switching and path reentry. By optimizing the control of the loop length, waveguide width, and coupling length, accurate phase compensation can be obtained under different modes, meeting the requirements of coherent interference and enhanced modulation.

[0051] Furthermore, by introducing a light field circulation path, this invention not only improves modulation efficiency but also effectively overcomes the problems of insufficient interaction length, complex mode switching, and limited modulation efficiency in traditional acousto-optic modulators, providing a new solution for realizing a high-performance, low-power, and highly flexible integrated acousto-optic modulation platform.

[0052] Example 2:

[0053] This embodiment 2 is applied to the embodiment 1, such as Figure 2As shown in Example 2, a non-resonant cyclic integrated acousto-optic modulator based on a silicon-silicon dioxide substrate with an operating frequency of 1.16 GHz is provided. The modulation structure achieves loop-loop modulation enhancement in the TE1 mode. This structure mainly includes an interdigital transducer 5, an acoustic transducer region formed by etching a lithium niobate thin film 3, a single-mode optical waveguide 6 composed of a chalcogenide glass waveguide 4, an optical tapered transition region 7, a multimode optical waveguide 9, an asymmetric directional coupler 8, and a loop 10. Laser light is injected from the single-mode optical waveguide 6 in TE0 mode, gradually widens through the optical tapered transition region 7, and enters the multimode waveguide supporting TE0 / TE1 modes, achieving acousto-optic modulation for the first time through the modulation region. Subsequently, the light wave enters the loop 10 through the asymmetric directional coupler 8, converts to TE1 mode, and re-enters the main modulation region, achieving secondary modulation. The multimode optical waveguide 9 has a width of 1950 nm, the ring circuit 10 has a waveguide width of 950 nm, the asymmetric directional coupler 8 has a coupling length of 210 μm and a coupling distance of 400 nm.

[0054] Example 3:

[0055] This embodiment 3 is applied to embodiment 1, such as Figure 2 As shown in Example 3, a non-resonant cyclic integrated acousto-optic modulator based on a silicon-silicon dioxide substrate with an operating frequency of 1.16 GHz is provided. The modulation structure achieves loop-loop modulation enhancement in the TE1 mode. This structure mainly includes an interdigital transducer 5, an acoustic transducer region formed by etching a lithium niobate thin film 3, a single-mode optical waveguide 6 composed of a chalcogenide glass waveguide 4, a tapered optical transition region 7, a multimode optical waveguide 9, an asymmetric directional coupler 8, and a loop circuit 10. Laser light is injected from the input waveguide in TE0 mode, gradually widening through the tapered structure before entering the multimode waveguide supporting TE0 / TE2 modes, achieving acousto-optic modulation for the first time in the modulation region. Subsequently, the light wave enters the loop-loop path through the asymmetric directional coupler, converts to TE2 mode, and re-enters the main modulation region, achieving secondary modulation. The width of the multimode waveguide is 3230 nm, the waveguide width of the loop circuit 10 is 1020 nm, the coupling length of the asymmetric directional coupler 8 is 376 μm, and the coupling distance is 400 nm.

[0056] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

[0057] Many other changes and modifications can be made without departing from the concept and scope of this invention. It should be understood that this invention is not limited to the specific embodiments, and the scope of this invention is defined by the appended claims.

Claims

1. A non-resonant, cyclic integrated acousto-optic modulator, comprising a substrate, characterized in that, The substrate includes a silicon substrate (1) and a silicon dioxide layer (2) disposed on the silicon substrate (1). A lithium niobate-chalcogenide glass heterostructure is disposed on the silicon dioxide layer (2). The lithium niobate-chalcogenide glass heterostructure includes a lithium niobate thin film (3) and a chalcogenide waveguide (4) heterogeneously integrated on the lithium niobate thin film (3). The lithium niobate thin film (3) is etched to form a transducer region, and an interdigital transducer (5) is provided on the transducer region; the chalcogenide waveguide (4) includes, in sequence: a single-mode optical waveguide (6), a first optical conical transition region (7), a multimode optical waveguide (9), an asymmetric directional coupler (8), and a ring loop waveguide (10); the single-mode optical waveguide (6) is connected to one end of the multimode optical waveguide (9) through the first optical conical transition region (7), and the other end of the multimode optical waveguide (9) is coupled to the ring loop waveguide (10) through the asymmetric directional coupler (8); a second optical conical transition region (7) is also provided between the multimode optical waveguide (9) and the ring loop waveguide (10) for mode transition and guiding the light wave back to the modulation region, so as to realize the mode conversion and cyclic modulation of the optical signal.

2. The non-resonant, cyclic integrated acousto-optic modulator according to claim 1, characterized in that, The asymmetric directional coupler (8) is distributed between the multimode optical waveguide (9) and the ring loop waveguide (10), converting the TEO mode light wave propagating in the multimode optical waveguide (9) into a TEO mode light wave through mode-selective coupling. n (n≥1) mode, and guide it into the ring loop waveguide (10) to realize the feedback path of the optical signal. The feedback optical wave can return to the modulation area again and perform subsequent acousto-optic modulation with the acoustic field.

3. The non-resonant, cyclic integrated acousto-optic modulator according to claim 1, characterized in that, Its signal modulation process includes: An external laser is injected through a single-mode optical waveguide (6), passes through the first optical cone transition region (7), and enters a multimode optical waveguide (9). In the TEO mode, it first interacts with the acoustic field in the modulation region. When the TEO mode light wave propagates to the end of the multimode optical waveguide (9), it is coupled to the TEO mode light wave via an asymmetric directional coupler (8). n (n≥1) Mode conversion of the mode; the light wave after mode conversion is coupled into the ring loop waveguide (10) via the asymmetric directional coupler (8), forming an optical feedback path in the loop, and re-entering the modulation region in the feedback mode to complete the second or multiple acousto-optic modulation, thereby realizing non-resonant cyclic modulation enhancement.

4. The non-resonant, cyclic integrated acousto-optic modulator according to claim 1, characterized in that, The interdigitated transducer (5), single-mode optical waveguide (6), optical conical transition region, asymmetric directional coupler (8), multimode optical waveguide (9) and ring loop waveguide (10) are all in a non-suspended state relative to the substrate.

5. A non-resonant, cyclic integrated acousto-optic modulator according to claim 1, characterized in that, The widths of the single-mode optical waveguide (6), multimode optical waveguide (9) and ring loop waveguide (10) are all 925nm~3230nm. The optical path length of the ring loop waveguide (10) is designed to be an integer multiple of 2π of the optical phase change, and the radius of the curved waveguide in the loop is 120um.

6. The non-resonant, cyclic integrated acousto-optic modulator according to claim 1, characterized in that, The coupling distance between the ring loop waveguide (10) and the multimode optical waveguide (9) is 400 nm, and the coupling length of the asymmetric directional coupler (8) is 210 μm to 376 μm.

7. A non-resonant, cyclic integrated acousto-optic modulator according to claim 1, characterized in that, The lithium niobate film (3) is tangentially XZ relative to the interdigital transducer (5). The interdigital transducer (5) has a finger width of 500 nm, an aperture of 120 μm, and 85 to 130 interdigital pairs. Its distance from the waveguide is 5 μm to 8.3 μm. The interdigital transducer (5) is used to excite Rayleigh-like and Love-like waves with a frequency range of 300 MHz to 8 GHz. The lithium niobate film (3) has a thickness of 400 nm, the silicon dioxide layer (2) has a thickness of 0 to 2000 nm, and the chalcogenide waveguide (4) has a thickness of 925 nm to 3230 nm. The interdigital transducer (5) is used to excite higher-order transverse electric modes (TE). n The refractive index modulation efficiency of the n≥1) is higher than that of the fundamental mode (TE0); the ring loop waveguide (10) is a closed optical path structure, configured to recouple the modulated residual high-order mode optical field to the input end of the multimode optical waveguide (9) to realize the recycling of optical energy and modulation enhancement.

8. A non-resonant, cyclic integrated acousto-optic modulator according to claim 1, characterized in that, The lateral dimension of the multimode optical waveguide (9) is determined by optimizing the following conditions: the characteristic frequency corresponding to the maximum refractive index change caused by the acousto-optic interaction in the multimode optical waveguide (9) is equal to the characteristic frequency corresponding to the minimum value of the S11 curve of the radio frequency reflection coefficient of the interdigital transducer (5). Based on this frequency matching condition, its lateral dimension range is determined to be 925nm~1020nm. The lateral dimension of the single-mode optical waveguide (6) is determined to be 1950nm~3230nm according to the single-mode transmission conditions and the mode field matching requirements with the multimode optical waveguide (9).

9. A non-resonant, cyclic integrated acousto-optic modulator according to claim 1, characterized in that, One end of the ring-loop waveguide (10) is coupled to the multimode optical waveguide (9) via an asymmetric directional coupler (8) to receive the TE mode light wave converted from the TE0 mode light wave in the multimode optical waveguide (9). n (n≥1) mode light wave, the ring loop waveguide (10) is composed of straight waveguide and curved waveguide, forming a closed light propagation path, and its total length is designed to be an integer multiple of 2π for optical phase change, so as to achieve stable phase feedback; wherein, the bending radius of the curved waveguide is 120μm, so as to reduce the loss of light wave in the bending propagation process; the other end of the ring loop waveguide (10) is connected to the multimode optical waveguide (9) through the second optical conical transition region (7), which is used to guide the feedback light wave back to the modulation region, so as to realize the cyclic return and remodulation of the optical signal; using the ring loop waveguide (10) structure, the light wave can interact with the acoustic field multiple times in the modulation region, thereby realizing the non-resonant cyclic modulation mechanism without relying on the resonant structure, significantly improving the modulation depth and energy efficiency.

10. A non-resonant, cyclic integrated acousto-optic modulator according to claim 1, characterized in that, The overall ring-shaped waveguide (10) is designed to be short in length, so that the lateral dimension of the overall device can be controlled within the range of 3361nm~3861nm. This minimizes the propagation delay of light in the ring path, increases the modulation frequency range of possible superposition, and forms multiple modulations under the same sound field that are approximately equivalent, thereby achieving enhanced superposition of high-frequency modulation depth. The device can be made into a single-loop structure with the fundamental mode to a single higher-order mode, or into a multi-loop structure with the fundamental mode to multiple higher-order modes.

Images