An on-chip acousto-optic modulation device and a preparation method thereof

Abstract

The application relates to the field of optoelectronic technology, and relates to an on-chip acousto-optic modulation device and a preparation method thereof. The on-chip acousto-optic modulation device comprises a lithium niobate-chalcogenide material hetero-layer arranged on a substrate, an interdigital transducer arranged on the lithium niobate film layer, and a chalcogenide photonic waveguide structure formed by etching the chalcogenide material film layer, the chalcogenide photonic waveguide structure comprising a collinear acousto-optic coupling mode conversion structure and a cascaded asymmetric waveguide mode demultiplexing structure; the collinear acousto-optic coupling mode conversion structure can simultaneously bind input light waves and surface acoustic waves, and make the light waves and the surface acoustic waves transmit collinearly in the same direction, under the phase matching condition, make incident light produce mode conversion, complete conversion from a low-order mode to a high-order mode, and produce a single sideband; the cascaded asymmetric waveguide mode demultiplexing structure is used for filtering a carrier multiple times to realize high extinction ratio. The application greatly improves the modulation efficiency of the device and greatly improves the extinction ratio.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optoelectronic technology, and more particularly, to an on-chip acousto-optic modulation device and a preparation method thereof. BACKGROUND

[0002] With the rapid development of cloud computing, Internet of Things, big data, 5G communication, artificial intelligence and other technologies, the network scale of data centers continues to expand, and the demand for data transmission capacity is growing rapidly. However, traditional electrical interconnection faces certain challenges in dealing with high-density, high-speed and large-capacity scenarios. Therefore, it is urgent to develop future information technology to meet the needs of information generation, exchange, perception, storage and processing, and high-performance and high-integration photonic chips are the physical basis for the development of future information technology. Photonic chips use photons / optical waves as information carriers, and can realize accurate acquisition, high-speed transmission and parallel processing of huge amounts of information. Photonic chips have the advantages of fast processing speed, small information distortion and low energy consumption, and are considered as one of the core technologies in the "post-Moore era". In photonic chips, acousto-optic modulation is a key technology to realize on-chip frequency shifting and high-speed switching.

[0003] Traditional commercial acousto-optic modulation devices are made of block-shaped piezoelectric crystal materials such as TeO2 or LiNbO3, which have large volume, high energy consumption and are incompatible with wafers, hindering their integration on chips and failing to meet the requirements of low-power, high-integration and high-reliability acousto-optic modulation devices in the information age. With the development of micro-nano processing technology, lithium niobate nanosheet bonding technology is becoming mature, making it possible for acousto-optic modulation chips based on lithium niobate piezoelectric thin films to efficiently manipulate the intensity, frequency and phase of light. In on-chip acousto-optic modulation, the high confinement of phonon and photon waveguides enables surface acoustic waves and light waves to be confined in a micron-scale size range, thereby producing stronger interaction than bulk material devices. However, due to the lack of prominent photoelastic properties of lithium niobate, the high sensitivity of existing in-coupling structures to processing errors, and the inability to effectively separate the carrier wave from the modulation wave, the modulation efficiency is low, and the extinction ratio is far behind traditional commercial devices. Traditional acousto-optic modulation devices use acousto-optic Bragg diffraction deflection characteristics, which are spatially demultiplexed with carrier and modulation waves, and have high extinction ratios based on the large size of the device structure. MZI and micro-ring structure on-chip acousto-optic modulation uses an in-coupling interference scheme, and the extinction ratio depends on the processing accuracy of the coupling structure. It is very difficult to achieve an extinction ratio of more than 30 dB due to the carrier and modulation wave crosstalk. SUMMARY

[0004] The present application aims to overcome the low acousto-optic extinction ratio of acousto-optic modulation chips based on lithium niobate piezoelectric thin films in the prior art, and provides an on-chip acousto-optic modulation device and a preparation method thereof, which enhances the acousto-optic interaction strength and thus improves the extinction ratio.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is:

[0006] The application provides an on-chip acousto-optic modulation device, which comprises a lithium niobate-chalcogenide material hetero-layer arranged on a substrate, an interdigital transducer capable of generating a surface acoustic wave arranged on the lithium niobate film layer, and a chalcogenide photonic waveguide structure formed by etching the chalcogenide film layer, wherein the chalcogenide photonic waveguide structure comprises a collinear acousto-optic coupling mode conversion structure and a cascaded asymmetric waveguide mode demultiplexing structure; the collinear acousto-optic coupling mode conversion structure can simultaneously confine an input light wave and a surface acoustic wave, and make the light wave and the surface acoustic wave transmit collinearly in the same direction, under a phase matching condition, make incident light generate mode conversion, complete conversion from a low-order mode to a high-order mode, and generate a single sideband; and the cascaded asymmetric waveguide mode demultiplexing structure is used for filtering a carrier wave multiple times to realize high extinction ratio.

[0007] The acousto-optic modulation device of the present application is based on a lithium niobate-chalcogenide material mixed hetero-integrated chalcogenide photonic waveguide structure, which fully utilizes the excellent piezoelectric characteristics of the lithium niobate film and the significant photoelastic characteristics of the chalcogenide material, can significantly play the advantages of piezoelectric effect and photoelastic effect, the interdigital transducer can effectively focus and confine the surface acoustic wave energy in the collinear acousto-optic coupling mode conversion structure, and the sound wave and the light wave transmit collinearly in the structure, through collinear acousto-optic interaction, fully utilize the acousto-optic Brillouin scattering effect, the acousto-optic interaction intensity reaches the maximum, and the acousto-optic interaction intensity is significantly enhanced, so that the mode conversion and single sideband frequency shift can be realized in the acousto-optic interaction length, and the modulation efficiency of the device is greatly improved; in addition, the cascaded asymmetric waveguide mode demultiplexing structure is introduced to filter the carrier wave, and the extinction ratio is greatly improved by using the phase matching relationship.

[0008] Further, the collinear acousto-optic coupling mode conversion structure comprises an input optical waveguide, a chalcogenide phonon-photon collinear waveguide structure mode-coupled with the input optical waveguide, and a focusing waveguide for focusing the surface acoustic wave; the chalcogenide phonon-photon collinear waveguide structure simultaneously binds the input optical wave and the surface acoustic wave, so that the optical wave and the surface acoustic wave are collinearly transmitted in the same direction in the chalcogenide phonon-photon collinear waveguide structure; under the condition of satisfying the Brilouin scattering phase matching condition, the optical wave and the surface acoustic wave interact in the collinear acousto-optic coupling mode conversion structure, so that the optical wave is mode-converted, the conversion from a low-order mode to a high-order mode and the single sideband frequency shift are realized. The design of the focusing waveguide effectively focuses the surface acoustic wave energy excited by the interdigital transducer and binds the surface acoustic wave energy in the chalcogenide phonon-photon collinear waveguide structure. In the structure in which the acoustic wave and the optical wave are collinearly transmitted, the acousto-optic interaction is utilized through the collinear acousto-optic interaction, the phase matching condition required by the Brilouin scattering effect is ensured between the specific optical wave mode and the specific frequency of the surface acoustic wave through the precise geometric design of the chalcogenide phonon-photon collinear waveguide structure, the acousto-optic interaction intensity reaches the maximum under the phase matching condition, the above-mentioned structure synergistically acts, and the acousto-optic interaction intensity is significantly enhanced, so that the high-efficiency mode conversion and the single sideband frequency shift can be realized in the obviously shortened acousto-optic interaction length, and the modulation efficiency of the device is greatly improved.

[0009] Further, the focusing waveguide is a tapered structure extending from the transmission direction of the interdigital transducer to the chalcogenide phonon-photon collinear waveguide structure; the surface acoustic wave generated by the interdigital transducer is focused and coupled into the chalcogenide phonon-photon collinear waveguide structure through the focusing waveguide. In the present application, the focusing waveguide is a tapered structure, and the width thereof gradually decreases from one end of the interdigital transducer to the end of the chalcogenide phonon-photon collinear waveguide structure.

[0010] Further, the cascaded asymmetric waveguide mode demultiplexing structure is connected with the output light path of the chalcogenide phonon-photon collinear waveguide structure, and the cascaded asymmetric waveguide mode demultiplexing structure comprises at least two same or different type of mode selection substructures in cascade; the mode selection substructure is based on the inter-mode conversion principle, and the converted high-order mode and the unconverted low-order mode are converted by using the difference in the propagation characteristics in the waveguide; the low-order mode is filtered multiple times by cascading the mode selection substructures, so as to realize high extinction ratio. Downstream of the acousto-optic interaction region, the cascaded asymmetric waveguide mode demultiplexing structure is introduced, and the structure works based on the inter-mode beam splitting principle. The light signal generated after the mode conversion and the original carrier which is not converted have different propagation characteristics in the cascaded asymmetric waveguide mode demultiplexing structure. The carrier is filtered multiple times and step by step by the cascaded asymmetric waveguide mode demultiplexing structure. The acousto-optic interaction itself strictly depends on the phase matching condition to generate a specific high-order mode. The cascaded asymmetric waveguide mode demultiplexing structure skillfully uses the orthogonality between the high-order mode generated by the phase matching conversion and the carrier mode. The orthogonality enables the cascaded asymmetric waveguide mode demultiplexing structure to selectively separate the two modes. By deeply filtering the carrier through the cascaded asymmetric waveguide mode demultiplexing structure and using the inherent mode orthogonality brought by the mode conversion, the extinction ratio of the device is greatly improved, and the key problem of serious carrier and modulation wave crosstalk and low extinction ratio of the traditional on-chip acousto-optic device is effectively solved.

[0011] Further, the mode selection substructure comprises a multi-mode interference structure, an asymmetric directional coupler structure, a photonic crystal waveguide structure or an out-of-plane grating structure. By cascading a plurality of same or different mode selection substructures, the carrier is filtered, the cascaded mode demultiplexing is realized, and high extinction ratio is achieved.

[0012] Further, the lithium niobate-chalcogenide material hetero-layer comprises a lithium niobate thin film layer arranged on a silicon-silicon dioxide substrate wafer and a chalcogenide material thin film layer hetero-integrated on the lithium niobate thin film layer; and the interdigital transducer comprises a plurality of interdigital electrodes. The present application combines the thin film lithium niobate and the novel infrared waveband transparent chalcogenide material, and comprehensively utilizes the excellent piezoelectric characteristics of lithium niobate and the significant photoelastic characteristics of chalcogenide material to improve the acousto-optic interaction strength.

[0013] Further, the chalcogenide phonon-photon collinear waveguide structure is a rectangular or ridge waveguide. By designing the geometric dimensions such as width and height of the chalcogenide phonon-photon collinear waveguide structure, it can be ensured that the phase matching condition required by the Brillouin scattering is met between the specific light wave mode propagating in the chalcogenide phonon-photon collinear waveguide structure and the specific frequency of the surface acoustic wave.

[0014] Further, the collinear acousto-optic coupling mode conversion structure is in a suspended state relative to the substrate. The collinear acousto-optic coupling mode conversion structure is designed in a suspended state, which can effectively bind the surface acoustic wave and avoid the leakage of the acoustic wave in the substrate.

[0015] Further, the chalcogenide material includes antimony sulfide, germanium tellurium sulfide, arsenic selenide, germanium antimony tellurium, germanium arsenic sulfide, germanium tellurium selenium and the like sulfides or selenides.

[0016] Further, the acousto-optic modulation device includes an acousto-optic modulator, an acousto-optic frequency shifter, or an acousto-optic high-speed switch.

[0017] The application also provides a preparation method of the above-mentioned on-chip acousto-optic modulation device, including the following steps:

[0018] S1. Depositing a chalcogenide material thin film layer on the substrate covered with the lithium niobate thin film layer by using evaporation or sputtering method;

[0019] S2. Exposing the electron glue on the chalcogenide material thin film layer by using grating scanning electron beam lithography;

[0020] S3. Obtaining the electron glue mask pattern of the chalcogenide photonic waveguide structure by developing;

[0021] S4. Using the pattern obtained on the electron glue as a mask, and using ion beam etching equipment to perform dry etching;

[0022] S5. Placing the etched substrate into a chamber, and using oxygen plasma etching gas to remove the residual electron glue on the top;

[0023] S6. Exposing the electron glue or photoresist by using electron beam direct writing system or ultraviolet lithography, protecting the chalcogenide photonic waveguide structure area, and manufacturing the phonon waveguide layout through alignment process, i.e. the layout of the collinear acousto-optic coupling mode conversion structure in a suspended state;

[0024] S7. Etching the chalcogenide material thin film layer or the lithium niobate thin film layer based on the new electron glue or photoresist mask pattern;

[0025] S8. Placing the etched substrate into a chamber, and using oxygen plasma etching gas to remove the residual electron glue on the top;

[0026] S9. Exposing the electron glue or photoresist by using electron beam direct writing system or ultraviolet lithography, protecting the chalcogenide photonic waveguide structure area, opening a window for the interdigital transducer area, and completing the interdigital transducer layout manufacturing;

[0027] S10. Obtaining Ti / Au electrode material based on the new electron glue or photoresist mask pattern, or by using evaporation or sputtering deposition process;

[0028] S11. Using a stripping solution to perform a lift-off process to obtain the interdigital transducer structure;

[0029] S12. Finally removing the remaining electronic glue on the substrate.

[0030] The application also provides a preparation method of the above-mentioned on-chip acousto-optic modulation device, comprising the following steps:

[0031] S1. Depositing a thin film layer of chalcogenide material on a substrate covered with a lithium niobate film layer by using an evaporation or sputtering method;

[0032] S2. Exposing electronic glue on the thin film layer of chalcogenide material by using a grating scanning electron beam lithography;

[0033] S3. Obtaining an electronic glue mask pattern of the chalcogenide photonic waveguide structure by developing;

[0034] S4. Using the pattern obtained on the electronic glue as a mask, and performing dry etching by using an ion beam etching device;

[0035] S5. Placing the etched substrate into a chamber, and removing the electronic glue remaining on the top by using oxygen plasma etching gas;

[0036] S6. Exposing electronic glue or photoresist by using an electron beam direct writing system or ultraviolet lithography, protecting the chalcogenide photonic waveguide structure area, opening a window for the interdigital transducer area, and completing the interdigital transducer layout;

[0037] S7. Obtaining Ti / Au electrode material based on the new electronic glue or photoresist mask pattern, or by using a deposition process such as evaporation or sputtering;

[0038] S8. Using a stripping solution to perform a lift-off process to obtain the interdigital transducer structure;

[0039] S9. Removing the remaining electronic glue on the substrate;

[0040] S10. Exposing electronic glue or photoresist by using an electron beam lithography system or ultraviolet lithography system, and then developing to obtain a new electronic glue or photoresist mask pattern, i.e. the layout of the suspended-state collinear acousto-optic coupling mode conversion structure;

[0041] S11. Transferring a hard mask based on the new electronic glue or photoresist mask pattern, or by using a deposition process such as evaporation or sputtering, and then performing dry etching by using a reactive ion etching device, and etching through the lithium niobate film layer to expose the silicon oxide layer, so as to realize window opening;

[0042] S12. Corroding the bottom silicon oxide film layer by using a hydrofluoric acid buffer solution, and controlling the etching time to realize the hollowing of the bottom lithium niobate film layer;

[0043] S13. Remove the residual electronic glue on the substrate.

[0044] Compared with the prior art, the present application has the following advantages:

[0045] 1. The on-chip acousto-optic modulation device and its preparation method, based on lithium niobate-sulfur material mixed hetero-integrated sulfide photonic waveguide structure, make full use of the excellent piezoelectric properties of lithium niobate thin film and the significant photoelastic properties of sulfide material, can significantly play the advantages of piezoelectric effect and photoelastic effect, the interdigital transducer excites the effective focusing and binding of the surface acoustic wave energy in the collinear acousto-optic coupling mode conversion structure, in the structure of the collinear transmission of the acoustic wave and the light wave, through the collinear acousto-optic effect, the acousto-optic Bragg scattering effect is fully utilized, the acousto-optic interaction intensity reaches the maximum, the acousto-optic interaction intensity is significantly enhanced, so that the length of the acousto-optic effect is obviously shortened, and high-efficiency mode conversion and single sideband frequency shift can be realized, and the modulation efficiency of the device is greatly improved; in addition, the cascaded asymmetric waveguide mode demultiplexing structure is introduced, the phase matching relationship is utilized, the carrier and the modulation wave of the acousto-optic modulation are split, and the extinction is effectively improved.

[0046] 2. The on-chip acousto-optic modulation device, through the design of the focusing waveguide, the surface acoustic wave energy excited by the interdigital transducer is effectively focused and bound in the sulfide phonon-photon collinear waveguide structure, in the structure of the collinear transmission of the acoustic wave and the light wave, through the collinear acousto-optic effect, the acousto-optic Bragg scattering effect is fully utilized, through the precise geometric design of the sulfide phonon-photon collinear waveguide structure, the phase matching condition required by the Bragg scattering between the specific light wave mode and the specific frequency of the surface acoustic wave propagating in the structure can be ensured, under the phase matching condition, the acousto-optic interaction intensity reaches the maximum, the synergistic effect of hetero-material utilization, acoustic wave focusing and binding, collinear waveguide and phase matching significantly enhances the acousto-optic interaction intensity, so that high-efficiency mode conversion and single sideband frequency shift can be realized in the obviously shortened acousto-optic interaction length, and the modulation efficiency of the device is greatly improved.

[0047] 3. The on-chip acousto-optic modulation device, the cascaded asymmetric waveguide mode demultiplexing structure filters the carrier multiple times, and realizes high-extinction-ratio carrier filtering; the cascaded asymmetric waveguide mode demultiplexing structure skillfully utilizes the orthogonality between the high-order mode generated by the phase matching conversion and the carrier mode, deeply filters the carrier through the cascaded asymmetric waveguide mode demultiplexing structure, and utilizes the inherent mode orthogonality brought by the mode conversion, the extinction ratio of the device is greatly improved, and the key problem of serious carrier and modulation wave crosstalk and low extinction ratio of the traditional on-chip acousto-optic device is effectively solved.

[0048] In summary, the on-chip acousto-optic modulation device and the preparation method thereof provided by the application, through the innovative combination and synergistic optimization of hetero-integrated waveguide, acoustic wave focusing confinement, collinear waveguide phase matching, cascade mode demultiplexing and mode orthogonality, the on-chip acousto-optic modulation device with high efficiency and high extinction ratio is realized for the first time, and the preparation method of the acousto-optic modulation device is simple, has large bandwidth and is easy to realize large-scale integration. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 It is a first perspective structural schematic diagram of the on-chip acousto-optic modulation device of the application.

[0050] Figure 2 It is a structural schematic diagram of another perspective of the on-chip acousto-optic modulation device of the application.

[0051] Figure 3 It is an input TE1 mode simulation simulation result diagram of the cascade asymmetric waveguide mode demultiplexing structure in the on-chip acousto-optic modulation device of the application.

[0052] Figure 4 It is an input TE0 mode simulation simulation result diagram of the cascade asymmetric waveguide mode demultiplexing structure in the on-chip acousto-optic modulation device of the application.

[0053] Figure 5 It is a propagation coefficient and wavelength change relationship simulation result diagram of the input TE1 and TE0 modes in the range of 1500nm-1600nm of the cascade asymmetric waveguide mode demultiplexing structure in the on-chip acousto-optic modulation device of the application.

[0054] Figure 6 It is a test link structure schematic diagram of the acousto-optic modulator in an embodiment.

[0055] Figure 7 It is a test link structure schematic diagram of the acousto-optic switch in an embodiment.

[0056] Figure 8 It is a test link structure schematic diagram of the acousto-optic frequency shifter in an embodiment.

[0057] Figure 9 It is a preparation method flowchart schematic diagram of a non-suspended acousto-optic modulation device in an embodiment.

[0058] Figure 10 It is a preparation method flowchart schematic diagram of a suspended acousto-optic modulation device in an embodiment.

[0059] In the drawings: 1, substrate; 2, lithium niobate thin film layer; 3, chalcogenide material thin film layer; 31, collinear acousto-optic coupling mode conversion structure; 311, input optical waveguide; 312, collinear waveguide structure of phonon-photon; 313, focusing waveguide; 32, cascaded asymmetric waveguide mode demultiplexing structure; 4, interdigital transducer. DETAILED DESCRIPTION

[0060] The application will be further described below in connection with specific embodiments. In the drawings, only for exemplary illustration, the representation is only a schematic diagram, not a physical diagram, and cannot be understood as a limitation on the application; in order to better illustrate the embodiments of the application, some components in the drawings will be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures in the drawings and their descriptions can be omitted.

[0061] The same or similar reference numerals in the drawings of the embodiments of the application correspond to the same or similar components; in the description of the application, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate the orientation or positional relationship shown in the drawings, only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the terms describing the positional relationship in the drawings are only for exemplary illustration, and cannot be understood as a limitation on the application, for those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0062] Embodiment one

[0063] The present embodiment is a first embodiment of an on-chip acousto-optic modulation device, as shown in Figure 1 and Figure 2 , including a lithium niobate-chalcogenide material heterostructure disposed on a substrate 1, an interdigital transducer 4 capable of generating surface acoustic waves disposed on a lithium niobate thin film layer 2, and a chalcogenide photonic waveguide structure formed by etching a chalcogenide material thin film layer 3, the chalcogenide photonic waveguide structure including a collinear acousto-optic coupling mode conversion structure 31 and a cascaded asymmetric waveguide mode demultiplexing structure 32; the lithium niobate-chalcogenide material heterostructure includes a lithium niobate thin film layer 2 disposed on a wafer with silicon-silicon dioxide as a substrate 1, and a chalcogenide material thin film layer 3 heterogeneously integrated on the lithium niobate thin film layer 2; the interdigital transducer 4 includes a plurality of interdigital electrodes.

[0064] As shown in Figure 2As shown in the figure, the collinear acousto-optic mode conversion structure 31 includes an input optical waveguide 311, a chalcogenide phonon-photon collinear waveguide structure 312 mode-coupled with the input optical waveguide 311, and a focusing waveguide 313 for focusing the surface acoustic wave; the chalcogenide phonon-photon collinear waveguide structure 312 simultaneously binds the input optical wave and the surface acoustic wave, so that the optical wave and the surface acoustic wave are collinearly transmitted in the same direction in the chalcogenide phonon-photon collinear waveguide structure 312; under the condition of satisfying the Brilouin scattering phase matching condition, the optical wave and the surface acoustic wave interact in the collinear acousto-optic mode conversion structure 31, which causes the mode conversion of the optical wave, realizes the conversion from the low-order mode to the high-order mode, and single sideband frequency shift.

[0065] As shown in the figure, Figure 2 The cascaded asymmetric waveguide mode demultiplexing structure 32 is connected with the output end of the chalcogenide phonon-photon collinear waveguide structure 312, and includes at least two same or different type of mode selection substructure cascades; the mode selection substructure is based on the inter-mode conversion principle, and uses the difference between the converted high-order mode and the unconverted low-order mode in the waveguide propagation characteristics for conversion; the low-order mode is filtered multiple times through cascading several mode selection substructures, so as to realize high extinction ratio.

[0066] The mode selection substructure includes a multimode interference structure, an asymmetric directional coupler structure, a photonic crystal waveguide structure, or an out-of-plane grating structure.

[0067] In the embodiment, as shown in the figure, Figure 2 The focusing waveguide 313 is a tapered structure, which extends from the transmission direction of the interdigital transducer 4 to the chalcogenide phonon-photon collinear waveguide structure 312; the surface acoustic wave generated by the interdigital transducer 4 is focused and coupled into the chalcogenide phonon-photon collinear waveguide structure 312 through the focusing waveguide 313. In the present application, the focusing waveguide 313 is a tapered structure, and its width gradually decreases from one end of the interdigital transducer 4 to the end of the chalcogenide phonon-photon collinear waveguide structure 312.

[0068] In the embodiment, the design of the focusing waveguide 313 effectively focuses and confines the surface acoustic wave energy excited by the interdigital transducer 4 in the chalcogenide phonon-photon collinear waveguide structure 312. In the structure where the acoustic wave and the optical wave are collinearly transmitted, the acoustic-optic interaction is achieved through the collinear acoustic-optic effect, and the acoustic-optic Bragg scattering effect is fully utilized. Through the precise geometric design (such as width and height) of the chalcogenide phonon-photon collinear waveguide structure 312, the phase matching condition (momentum conservation: optical input wave vector + acoustic wave vector = optical output wave vector) required for Bragg scattering is ensured between the specific optical mode (such as the incident TE0 mode) propagating in the structure and the surface acoustic wave of a specific frequency. Under the phase matching condition, the acoustic-optic interaction intensity reaches the maximum. The above structure design (heterogeneous material utilization, acoustic wave focusing and confinement, collinear waveguide, phase matching design) synergistically enhances the acoustic-optic interaction intensity, thereby realizing efficient mode conversion (such as TE0->TE1) and single sideband frequency shift in a significantly shortened acoustic-optic interaction length, and greatly improving the modulation efficiency of the device.

[0069] Downstream of the acoustic-optic interaction region (i.e., the chalcogenide phonon-photon collinear waveguide structure 312), a cascaded asymmetric waveguide mode demultiplexing structure 32 is introduced, which works based on the principle of intermodal beam splitting. The optical signal (such as the high-order mode TE1, i.e., the modulation wave / sideband) generated after mode conversion through acoustic-optic interaction and the original carrier (such as the low-order mode TE0) that has not been converted have different propagation characteristics (such as effective refractive index and coupling coefficient) in the cascaded asymmetric waveguide mode demultiplexing structure 32. The cascaded asymmetric waveguide mode demultiplexing structure 32 filters out the carrier multiple times and step by step. The acoustic-optic interaction itself strictly depends on the phase matching condition to produce a specific high-order mode (modulation wave). The cascaded asymmetric waveguide mode demultiplexing structure 32 skillfully utilizes the orthogonality (essentially the difference in wave vector / propagation constant) between the high-order mode generated by phase matching conversion and the carrier mode. This orthogonality enables the cascaded asymmetric waveguide mode demultiplexing structure 32 to selectively separate the two modes. By deeply filtering the carrier through the cascaded asymmetric waveguide mode demultiplexing structure 32 and utilizing the inherent mode orthogonality (resulting from phase matching) brought by mode conversion, the present application greatly improves the extinction ratio of the device (up to 40 dB or more), effectively solving the key problem of severe carrier and modulation wave crosstalk and low extinction ratio in traditional on-chip acoustic-optic devices.

[0070] In the embodiment, the chalcogenide phonon-photon collinear waveguide structure 312 is a rectangular or ridge waveguide. Through the design of geometric dimensions such as width and height of the chalcogenide phonon-photon collinear waveguide structure 312, the phase matching condition required for Bragg scattering is ensured between the specific optical mode propagating in the structure and the surface acoustic wave of a specific frequency.

[0071] In the embodiment, asFigure 1 As shown, the collinear acousto-optic coupling mode conversion structure 31 is in a suspended state relative to the substrate 1. The collinear acousto-optic coupling mode conversion structure 31 is designed in a suspended state, which can effectively bind the surface acoustic wave and avoid the leakage of the acoustic wave in the substrate.

[0072] In the embodiment, the chalcogenide material includes antimony sulfide, germanium tellurium sulfide, arsenic selenide, germanium antimony tellurium, germanium arsenic sulfide, germanium tellurium selenium, and the like. The acousto-optic modulation device includes an acousto-optic modulator, an acousto-optic frequency shifter, or an acousto-optic high-speed switch.

[0073] The chalcogenide photonic waveguide works in the communication waveband near 1550 nm, and the interdigital transducer 4 generates a 700 MHz surface acoustic wave. The interdigital transducer 4 excites the surface acoustic wave in the lithium niobate layer, and the focusing waveguide 313 can play a role in focusing the acoustic wave. The hetero-integrated lithium niobate thin film deformation drives the deformation of the surface chalcogenide material, so that the acoustic wave can be bound on the chalcogenide photonic waveguide and propagate along the direction of the chalcogenide photonic waveguide. Through the binding of the surface acoustic wave energy by the chalcogenide phonon-photon collinear waveguide structure 312, efficient energy utilization is achieved. When the phonon and the photon in the chalcogenide phonon-photon collinear waveguide structure 312 satisfy the condition of Brillouin scattering, that is, the frequency and wave vector of the acoustic wave and the optical wave satisfy the phase matching condition (the output optical angular frequency = the input optical angular frequency + the acoustic angular frequency, the optical output wave vector = the optical input wave vector + the acoustic wave vector), the light occurs mode conversion, forming a single sideband frequency shift. The selection of the collinear acousto-optic coupling mode conversion structure 31 can increase the interaction area and improve the energy utilization efficiency. In the cascaded asymmetric waveguide mode demultiplexing structure 32, the carrier wave and the modulation wave of the acousto-optic modulation are split, that is, the intermodal mode demultiplexing. By selecting the waveguide width of the asymmetric directional coupler that satisfies the modulation wave phase matching condition, the modulation wave is coupled to the narrow waveguide, and the carrier wave continues to transmit in the wide waveguide, so that the modes are separated to filter out the carrier wave. The selection of the asymmetric directional coupler efficiently filters out the carrier wave, and improves the extinction ratio of the acousto-optic modulator. Through the acoustic wave binding, the collinear acousto-optic coupling mode conversion structure 31 and the cascaded asymmetric waveguide mode demultiplexing structure 32 based on the asymmetric directional coupler, the on-chip acousto-optic modulation with high efficiency and high extinction ratio is realized.

[0074] Figures 3 to 5The simulation results of the key component, cascaded asymmetric waveguide mode demultiplexer structure 32 in the device are shown. In the embodiment, a plurality of asymmetric directional couplers are cascaded, and the structure adopts a hetero-integrated platform of LNOI (SiO2 (thickness 2 μm), LN (thickness 400 nm)-Sb2Se3 (thickness 280 nm), and excellent mode selection characteristics are achieved through accurate design of geometric parameters. In the working process of the device, the collinear acousto-optic coupling mode conversion structure 31 first converts the input TE0 mode into a TE1 mode, and then the cascaded asymmetric waveguide mode demultiplexer structure 32 is responsible for effectively separating the TE0 and TE1 modes. The simulation results show that the structure exhibits excellent mode selection performance. As shown in Figure 3 the right transmission TE1 mode can pass through efficiently. In sharp contrast, Figure 4 the right transmission TE0 mode is significantly suppressed. Further analysis of the wavelength-dependent performance, Figure 5 detailedly shows the relationship between the transmission coefficients of the two polarization modes and the wavelength. In the wide wavelength range of 1500-15600 nm, the transmission coefficient ratio of the TE1 mode to the TE0 mode is always maintained at 10 4 The corresponding extinction ratio reaches about 40 dB. These excellent performance indicators fully prove the rationality and feasibility of the structure design.

[0075] Figure 6 The test system corresponding to the application is shown in the schematic diagram, and the test system mainly includes a communication waveband tunable laser, a polarization controller, a coupler, a high-speed photoelectric detector, a vector network analyzer and an oscilloscope. During device testing, the light wave is output in a single-mode optical fiber through a laser, and the polarization is adjusted through a polarization controller after the light wave passes through the coupler and is divided into two beams. The splitting ratio of the coupler is determined according to the experimental conditions, one beam is used as a modulation light to enter the device to be tested, and the other beam is adjusted in the polarization state through another polarization controller. A certain frequency of microwave signal is excited on the surface of the device through the vector network analyzer, and when the impedance and frequency matching conditions are met, the interdigital transducer 4 will form a surface acoustic wave on the surface of the piezoelectric film. The light wave incident therein will be mode-converted under the action of the surface acoustic wave. The two beams interfere in the second coupler, and then the light signal is converted into an electrical signal through the photoelectric detector. After beating with the carrier wave, the S 21 transmission spectrum of the corresponding acoustic wave modulation signal can be observed by the network analyzer. The transmission spectrum is analyzed to calculate the conversion efficiency and modulation performance of the acoustic wave-light wave, and is input into the oscilloscope to observe the modulation effect.

[0076] In summary, the acousto-optic modulation device of the embodiment is based on lithium niobate-sulfur material mixed heterostructure integrated sulfide photonic waveguide structure, which makes full use of the excellent piezoelectric properties of lithium niobate thin film and the significant photoelastic properties of sulfide material, can significantly play the advantages of piezoelectric effect and photoelastic effect, the interdigital transducer 4 excites the sound surface wave energy to be effectively focused and bound in the collinear acousto-optic coupling mode conversion structure 31, in the structure of the collinear transmission of the sound wave and the light wave, through the collinear acousto-optic effect, the acousto-optic Bragg scattering effect is fully utilized, the acousto-optic interaction intensity reaches the maximum, and the acousto-optic interaction intensity is significantly enhanced, so that high-efficiency mode conversion and single sideband frequency shift can be realized in the obviously shortened acousto-optic interaction length, and the modulation efficiency of the device is greatly improved. In addition, the cascade asymmetric waveguide mode demultiplexing structure 32 is introduced to realize the filtering of the carrier wave, and the extinction ratio is greatly improved by using the phase matching relationship.

[0077] Embodiment two

[0078] The acousto-optic switch of the embodiment has a structure and principle similar to those of embodiment one, as shown in Figure 7 The test system of the acousto-optic switch of the embodiment is shown in the figure, and the test system mainly includes a communication waveband tunable laser, a polarization controller, a signal generator, a high-speed photodetector, a high-speed oscilloscope and an optical power meter.

[0079] During device testing, the light wave is output from the laser in the single-mode optical fiber, enters the device to be tested through the polarization controller after polarization control. The output switch of the signal generator is adjusted, a microwave signal of a certain frequency is loaded on the surface of the device to excite the Bragg grating in the sulfide photonic waveguide, the mode conversion of the incident light wave occurs, the converted mode satisfies the phase matching condition, and is coupled out through the cascade asymmetric waveguide mode demultiplexing structure 32. When there is no microwave signal excitation on the surface of the device, the incident light wave does not satisfy the phase matching condition, and there is almost no obvious coupling. The ratio of the optical powers in the on / off states of the device is tested by the optical power meter; the optical signal is converted into an electrical signal by the photodetector, and the electrical signal is input into the oscilloscope to test the rise / fall time of the optical switch.

[0080] Embodiment three

[0081] The acousto-optic frequency shifter of the embodiment has a structure and principle similar to those of embodiment one, as shown in Figure 8 The test system of the acousto-optic frequency shifter of the embodiment is shown in the figure, and the test system mainly includes a communication waveband tunable laser, a polarization controller, a signal generator and a precision spectrometer.

[0082] When testing the device, the light wave is output from the laser through the single-mode optical fiber, enters the device to be tested after being regulated by the polarization controller, and a certain frequency of microwave electrical signal is loaded on the surface of the device by the signal generator. When the impedance and frequency matching conditions are met, the interdigital transducer 4 will form a surface acoustic wave on the surface of the piezoelectric film, which propagates in the chalcogenide photonic waveguide. When the phase matching condition is met, the incident light wave in the chalcogenide photonic waveguide will be frequency-shifted, and an optical sideband will be generated. The intensity of the optical sideband signal and the frequency-shifted frequency of the light wave are observed by the optical spectrum analyzer.

[0083] Embodiment Four

[0084] This embodiment is a first embodiment of a preparation method of an on-chip acousto-optic regulating device, which is used for preparing the acousto-optic regulating device of Embodiment One. In this embodiment, a non-suspended acousto-optic regulating device is prepared, as shown in FIG. 1, which comprises the following steps: Figure 9

[0085] S1. A layer of Sb2Se3 chalcogenide material thin film layer 3 with a thickness of 280 nm is deposited on the substrate 1 covering the lithium niobate thin film layer 2 by using a thermal evaporation method;

[0086] S2. The positive electron glue (APR6200) is exposed on the pre-prepared Sb2Se3 chalcogenide material thin film layer 3 by using an electron direct writing system (EBL, Vistec EBPG 5000+), and the thickness is about 400 nm. Then, the electron glue is baked on a hot plate at 130°C for 5 min;

[0087] S3. The photonic waveguide mask pattern is obtained on the electron glue by developing with dimethylbenzene;

[0088] S4. The obtained pattern on the electron glue is used as a mask, and the dry etching of the chalcogenide material thin film is carried out by using a reactive ion beam etching device with argon gas. The side wall morphology is required to be smooth and steep. The etching power is set to 60 W, the gas pressure is 60 mTorr, the etching gas pressure is 60 mTorr, and the etching gas flow rate is 25-30 sccm;

[0089] S5. The etched substrate 1 is placed into a chamber, and the residual electron glue on the top is removed by using oxygen plasma etching gas. The gas flow rate is 50 sccm, the radio frequency power is 20 W, and the inductive coupled plasma (ICP) power is 1000 W. After the process is completed, the transfer processing of the chalcogenide photonic waveguide pattern on the substrate 1 is finished;

[0090] ​S6. Positive tone electron resist (APR6200) is spin-coated on the patterned Sb2Se3 chalcogenide material thin film layer 3, and after baking on a hot plate at 130°C for 5 min, a second exposure is performed using an electron beam direct writing system to protect the photonic waveguide region. The phononic waveguide pattern is fabricated through an alignment process, i.e. the pattern of the co-linear acousto-optic coupling mode conversion structure 31.

[0091] S7. Based on the new electron resist or photoresist mask pattern, the lithium niobate thin film layer 2 is etched using a reactive ion beam etching device with argon gas.

[0092] S8. The etched substrate 1 is placed in a chamber, and oxygen plasma etching gas is used to remove the residual electron resist on the top.

[0093] S9. Positive tone electron resist (APR6200) is spin-coated again on the prepared Sb2Se3 chalcogenide material thin film layer 3, and after baking on a hot plate at 130°C for 5 min, a third exposure is performed using an electron beam direct writing system (EBL, Vistec EBPG 5000+). After development using xylene, the area of the interdigital transducer 4 is exposed, and the fine structure pattern of the interdigital transducer 4 is completed.

[0094] S10. Based on the new electron resist or photoresist mask pattern, or by means of evaporation or sputter deposition process, a metal Ti / Au or Ti / Al thin film is obtained, with a thickness of Ti: 10 nm, Au, Al: 100 nm.

[0095] S11. The deposited substrate 1 is soaked in an organic solution (such as acetone) to remove the electron resist on the surface of the substrate 1 and the metal film on the electron resist, leaving the interdigital transducer 4 structure.

[0096] S12. Finally, the substrate 1 is soaked in an organic solution (such as acetone) to remove the residual electron resist on the surface, completing the final device preparation.

[0097] Example Five

[0098] This embodiment is a second embodiment of a method for preparing an on-chip acousto-optic modulation device, which is used to prepare the acousto-optic modulation device of Example One. In this embodiment, a suspended state acousto-optic modulation device is prepared. The integrated waveguide structure in this example is in a suspended state, i.e. the silicon oxide under the lithium niobate thin film is removed. In this structure, the suspended lithium niobate thin film can better confine the surface acoustic wave beam within the phononic waveguide, improving the modulation effect of the acoustic wave on the optical wave. At the same time, based on the suspended structure, the acousto-optic interaction length can be relatively small.

[0099] As shown in Figure 10 , the method comprises the following steps:

[0100] S1. A layer of Sb2Se3 chalcogenide material thin film layer 3 with a thickness of 280 nm is deposited on the substrate 1 covering the lithium niobate thin film layer 2 by using a thermal evaporation method;

[0101] S2. The positive electron glue (APR6200) is exposed on the pre-prepared Sb2Se3 chalcogenide material thin film layer 3 with a thickness of about 400 nm by using an electron direct writing system (EBL, Vistec EBPG 5000+), and then baked on a hot plate at 130°C for 5 min;

[0102] S3. The photonic waveguide mask pattern is obtained on the electron glue by developing with xylene;

[0103] S4. The Sb2Se3 chalcogenide material thin film layer 3 is dry etched by using a reactive ion beam etching device with argon as the mask film based on the pattern obtained on the electron glue, and the side wall morphology is required to be smooth and steep; the etching power is set to 60 W, the gas pressure is 60 mTorr, the etching gas pressure is 60 mTorr, and the etching gas flow rate is 25-30 sccm;

[0104] S5. The etched substrate 1 is placed in a chamber, and the residual electron glue on the top is removed by using oxygen plasma etching gas, wherein the gas flow rate is 50 sccm, the radio frequency power is 20 W, and the inductively coupled plasma ICP power is 1000 W; after the process is completed, the transfer processing of the chalcogenide photonic waveguide pattern on the substrate 1 is completed;

[0105] S6. The positive electron glue (APR6200) is spin-coated on the prepared Sb2Se3 chalcogenide material thin film layer 3 again, and then baked on a hot plate at 130°C for 5 min, and then secondarily exposed by using an electron beam direct writing system (EBL, Vistec EBPG 5000+); after developing with xylene, the area of the interdigital transducer 4 is exposed;

[0106] S7. Based on the new electron glue or photoresist mask pattern, or by using evaporation or sputtering deposition process, the metal Ti / Au or Ti / Al thin film is obtained, with a thickness of Ti: 10 nm, Au, Al: 100 nm;

[0107] S8. The deposited substrate 1 is soaked in an organic solution (such as acetone) to remove the electron glue on the surface of the substrate 1 and the metal film on the electron glue, leaving the interdigital transducer 4 structure;

[0108] S9. The substrate 1 is soaked in an organic solution (such as acetone) to remove the residual electron glue on the surface;

[0109] S10. On the prepared Sb2Se3 chalcogenide material thin film layer 3, spin-coat positive electron glue (APR6200) again, and then bake on a hot plate at 130°C for 5 min, and then perform three times of exposure by using an electron beam direct writing system (EBL, Vistec EBPG 5000+);

[0110] S11. Based on a new electron glue or photoresist mask pattern, or by means of evaporation or sputtering deposition process, transfer to obtain a hard mask of other materials, and then perform dry etching by using a reactive ion etching device, and etch through the lithium niobate thin film layer 2 to expose the silicon oxide layer, to realize windowing;

[0111] S12. Corrode the bottom silicon oxide thin film by using a hydrofluoric acid buffer solution, and control the etching time to realize the hollowing of the lithium niobate bottom;

[0112] S13. Finally, remove the residual electron glue on the substrate 1, and the lithium niobate-chalcogenide material heterostructure in a suspended state is completed.

[0113] In summary, in the present application, the heterostructure integration platform of lithium niobate and chalcogenide material can significantly play the advantages of excellent piezoelectric properties of lithium niobate and significant photoelastic effect of chalcogenide material, and the refractive index thereof is greater than that of lithium niobate, which can better confine light waves, and the effective combination of the two improves the efficiency of acousto-optic modulation. Compared with single material acousto-optic modulation devices, limited by the inherent properties of the material, the photoelasticity and piezoelectricity and the refractive index cannot simultaneously obtain high values, and the method of selecting two materials for heterostructure integration can solve this problem; the present application realizes acoustic surface wave focusing and confinement through the optimization design of acoustic waveguide; through the collinear structure on-chip acousto-optic modulation, the device efficiency is improved; in addition, by combining the optical waveguide with the asymmetric directional coupler structure design, high extinction ratio is realized, and high integration, high efficiency and high extinction ratio acousto-optic modulation devices are realized on-chip; compared with the prior art, the proposal will fill the gap of high efficiency and high extinction ratio on-chip acousto-optic modulation devices.

[0114] In the specific content of the above specific embodiments, any non-contradictory combination of technical features can be made, and in order to make the description simple, not all possible combinations of the above technical features are described, however, as long as the combination of these technical features does not exist, it should be considered as the scope of the present application.

[0115] Obviously, the above embodiments of the present application are merely exemplary but not intended to limit the embodiments of the present application. Based on the above description, any other variations or changes can be made by those skilled in the art without departing from the spirit and principles of the present application. It is not necessary to list all the embodiments here. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall fall within the scope of the claims of the present application.

Claims

1. An on-chip acousto-optic modulating device, characterized by, The lithium niobate-chalcogenide material hetero-layer is arranged on a substrate (1), an interdigital transducer (4) capable of generating a surface acoustic wave is arranged on a lithium niobate thin film layer (2), and a chalcogenide photonic waveguide structure is formed by etching a chalcogenide thin film layer (3), the chalcogenide photonic waveguide structure comprises a collinear acousto-optic coupling mode conversion structure (31) and a cascaded asymmetric waveguide mode demultiplexing structure (32); the collinear acousto-optic coupling mode conversion structure (31) can simultaneously bind an input light wave and a surface acoustic wave, and make the light wave and the surface acoustic wave transmit collinearly in the same direction, under the phase matching condition, make the incident light generate mode conversion, complete the conversion from a low-order mode to a high-order mode, and generate a single sideband; the cascaded asymmetric waveguide mode demultiplexing structure (32) is used for filtering a carrier multiple times to realize high extinction ratio; wherein the collinear acousto-optic coupling mode conversion structure (31) comprises an input light waveguide (311), a chalcogenide phonon-photon collinear waveguide structure (312) mode-coupled with the input light waveguide (311), and a focusing waveguide (313) for focusing a surface acoustic wave; the chalcogenide phonon-photon collinear waveguide structure (312) simultaneously binds an input light wave and a surface acoustic wave, and makes the light wave and the surface acoustic wave transmit collinearly in the same direction in the chalcogenide phonon-photon collinear waveguide structure (312), under the condition of satisfying the Brilouin scattering phase matching condition, the light wave and the surface acoustic wave interact in the collinear acousto-optic coupling mode conversion structure (31), which causes the light wave to generate mode conversion, realizes the conversion from a low-order mode to a high-order mode and single sideband frequency shift; the cascaded asymmetric waveguide mode demultiplexing structure (32) is connected with an output end light path of the chalcogenide phonon-photon collinear waveguide structure (312), and the cascaded asymmetric waveguide mode demultiplexing structure (32) comprises at least two same or different type mode selection substructure cascades; the mode selection substructure is based on the mode conversion principle, and uses the difference between the converted high-order mode and the unconverted low-order mode in the waveguide propagation characteristics to convert; by cascading several mode selection substructures, the low-order mode is filtered multiple times to realize high extinction ratio.

2. The on-chip acousto-optic modulating device of claim 1, wherein, The focusing waveguide (313) is a tapered structure, which extends from the transmission direction of the interdigital transducer (4) to the chalcogenide phonon-photon collinear waveguide structure (312); the surface acoustic wave generated by the interdigital transducer (4) is focused and coupled into the chalcogenide phonon-photon collinear waveguide structure (312) through the focusing waveguide (313).

3. The on-chip acousto-optic modulating device of claim 1, wherein, The mode selection substructure comprises a multimode interference structure, an asymmetric directional coupler structure, a photonic crystal waveguide structure or an out-of-plane grating structure.

4. The on-chip acousto-optic modulating device according to claim 2 or 3, characterized in that, The lithium niobate-chalcogenide material hetero-layer comprises a lithium niobate thin film layer (2) arranged on a silicon-silicon dioxide substrate (1) wafer, and a chalcogenide material thin film layer (3) heterogeneously integrated on the lithium niobate thin film layer (2); the interdigital transducer (4) comprises a plurality of interdigital electrodes.

5. The on-chip acousto-optic modulating device of claim 4, wherein, The chalcogenide phonon-photon collinear waveguide structure (312) is a rectangular or ridge waveguide.

6. The on-chip acousto-optic modulating device of claim 5, wherein, The collinear acousto-optic coupling mode conversion structure (31) is in a suspended state relative to the substrate (1).

7. A method of fabricating an on-chip acousto-optic modulating device according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: S1. depositing a thin film layer (3) of chalcogenide material on the substrate (1) covering the lithium niobate thin film layer (2) by using evaporation or sputtering; S2. exposing photoresist on the thin film layer (3) of chalcogenide material by raster scan electron beam lithography; S3. obtaining the photoresist mask pattern of the chalcogenide photonic waveguide structure by developing; S4. performing dry etching by using an ion beam etching device with the obtained pattern on the photoresist as a mask; S5. placing the etched substrate (1) into a chamber and removing the residual photoresist on the top by using oxygen plasma etching gas; S6. exposing photoresist or photoresist by using an electron beam direct writing system or ultraviolet lithography, protecting the chalcogenide photonic waveguide structure area, and making the layout of the phonon waveguide through an alignment process, that is, the layout of the collinear acousto-optic coupling mode conversion structure (31); S7. etching the thin film layer (3) of chalcogenide material or the lithium niobate thin film layer (2) based on the new photoresist or photoresist mask pattern or by using a deposition process such as evaporation or sputtering; S8. placing the etched substrate (1) into a chamber and removing the residual photoresist on the top by using oxygen plasma etching gas; S9. exposing photoresist or photoresist by using an electron beam direct writing system or ultraviolet lithography, protecting the chalcogenide photonic waveguide structure area, and opening a window for the area where the interdigital transducer (4) is located and completing the layout of the interdigital transducer (4); S10. obtaining Ti / Au electrode material based on the new photoresist or photoresist mask pattern or by using a deposition process such as evaporation or sputtering; S11. performing a lift-off process by using a stripping liquid to obtain the structure of the interdigital transducer (4); S12. finally removing the residual photoresist on the substrate (1).

8. A method of fabricating an on-chip acousto-optic modulating device according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: S1. depositing a thin film layer (3) of chalcogenide material on the substrate (1) covering the lithium niobate thin film layer (2) by using evaporation or sputtering; S2. exposing photoresist on the thin film layer (3) of chalcogenide material by raster scan electron beam lithography; S3. obtaining the photoresist mask pattern of the chalcogenide photonic waveguide structure by developing; S4. performing dry etching by using an ion beam etching device with the obtained pattern on the photoresist as a mask; S5. placing the etched substrate (1) into a chamber and removing the residual photoresist on the top by using oxygen plasma etching gas; S6. exposing photoresist or photoresist by using an electron beam direct writing system or ultraviolet lithography, protecting the chalcogenide photonic waveguide structure area, and opening a window for the area where the interdigital transducer (4) is located and completing the layout of the interdigital transducer (4); S7. obtaining Ti / Au electrode material based on the new photoresist or photoresist mask pattern or by using a deposition process such as evaporation or sputtering; S8. performing a lift-off process by using a stripping liquid to obtain the structure of the interdigital transducer (4); S9. removing the residual photoresist on the substrate (1). S10. Expose the electron resist or photoresist by electron beam lithography system or ultraviolet lithography system, and then obtain the new electron resist or photoresist mask pattern, i.e. the layout of the suspended state collinear acousto-optic coupling mode conversion structure (31) by developing; S11. Based on the new electron resist or photoresist mask pattern, or by means of evaporation, sputtering deposition process transfer to obtain a hard mask, and then use a reactive ion etching device to perform dry etching and etch through the lithium niobate film layer (2) to expose the silicon oxide layer, and realize windowing; S12. Use hydrofluoric acid buffer solution to etch the bottom silicon oxide film layer, control the etching time to realize the hollowing of the bottom of the lithium niobate film layer (2); S13. Remove the residual electron resist on the substrate (1).

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