An acousto-optic coupling-based non-reciprocal waveguide device, preparation method and application thereof
By designing collinear serpentine optical and acoustic waveguides on SiC-LN heterostructure films, and combining interdigital structures and acoustic scattering structures, the problem of acoustic wave transmission limitation of SiC materials in optical chips was solved, achieving efficient acoustic-optical coupling and multi-dimensional control.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI INST OF MICROSYSTEM & INFORMATION TECH CHINESE ACAD OF SCI
- Filing Date
- 2023-06-01
- Publication Date
- 2026-07-10
Smart Images
Figure CN116755265B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chip materials, and specifically relates to a non-reciprocal waveguide device based on acousto-optic coupling, its fabrication method, and its application. Background Technology
[0002] As an effective modulation method in integrated optics, acousto-optic coupling technology, combined with advanced materials integration methods, has the potential to achieve highly stable, ultra-compact optical modulation devices on-chip. Furthermore, Brillouin scattering, as a representative mechanism of photon-phonon interaction, has been used to achieve linear, highly sensitive, and robust frequency modulation and mode control. Although piezoelectric thin film materials such as LN and AlN have proven feasible for integrated acousto-optic coupling, the high acoustic loss, low field overlap, and low micro / nano fabrication compatibility of devices on the corresponding material platforms still pose significant challenges to achieving acousto-optic effects with long coupling distances. As a novel optical material, SiC possesses excellent properties such as high refractive index, high nonlinear coefficient, CMOS process compatibility, and strong mechanical stability, but its high acoustic velocity property prevents effective confinement of stable sound wave transmission, thus limiting its widespread application in integrated acoustics. Moreover, sound waves can cause decoupling between waveguides, greatly limiting the application of acousto-optic effects within optical chip systems. Summary of the Invention
[0003] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a non-reciprocal waveguide device based on acousto-optic coupling, its fabrication method, and its application.
[0004] A waveguide device according to the present invention includes: a substrate, a SiC-LN heterofilm, and a metal interdigitated structure, wherein the SiC-LN heterofilm is disposed on the substrate, and the metal interdigitated structure is disposed on the SiC-LN heterofilm.
[0005] The SiC-LN heterostructure is a bonded structure of SiC and LN films; wherein the SiC-LN heterostructure contains optical waveguides, acoustic waveguides and acoustic scattering structures.
[0006] The substrate is a polycrystalline SiC substrate; the SiC-LN heterofilm contains collinear optical waveguides, acoustic waveguides, and relatively independent acoustic scattering structures.
[0007] The optical waveguide includes an optical linear waveguide and an optical coupling waveguide; the optical waveguide is disposed within a SiC thin film; the optical coupling waveguide is at least one of a grating waveguide and a tapered waveguide.
[0008] The acoustic waveguide includes an acoustic linear waveguide and an acoustic tapered coupled waveguide; the acoustic scattering structure is a semi-circular structure for rapidly attenuating acoustic waves; the acoustic waveguide and acoustic scattering structure are disposed in a SiC-LN heterostructure thin film, and further, the acoustic waveguide and acoustic scattering structure are defined within the LN thin film after being etched into the SiC thin film.
[0009] The optical waveguide structure has a thickness of 200nm to 800nm and a width of 200nm to 1μm; the acoustic waveguide structure has a thickness of 500nm to 5μm and a width of 1μm to 10μm; the optical and acoustic linear waveguides are collinear serpentine structures; the semicircular radius of the collinear serpentine structure is 750nm to 7.5μm; the optical coupling waveguide is disposed within the acoustic scattering structure and does not overlap with the acoustic waveguide region; the metal interdigitated structure is disposed within the acoustic tapered coupling waveguide.
[0010] A method for fabricating the waveguide device of the present invention includes:
[0011] We provide LN wafers, substrates (SiC substrates), SiC wafers, and silicon oxide-silicon substrates;
[0012] (1) Plasma activation is used to activate the LN wafer and substrate surface, on the LN wafer <0001> The LN material is thinned by surface bonding to the substrate, heat treatment is performed, and then mechanical grinding and chemical mechanical polishing are used to obtain an LN film of the target thickness.
[0013] (2) On SiC wafers <0001> A silicon oxide layer is prepared on the surface. The silicon oxide layer of the SiC wafer and the silicon oxide layer of the silicon oxide-silicon substrate are activated by plasma. The SiC wafer structure is bonded to the surface of another silicon oxide-silicon substrate along the silicon oxide surface. After heat treatment, the SiC material is thinned to the target thickness by mechanical grinding and chemical mechanical polishing to obtain a SiC thin film on an insulator.
[0014] (3) Activate the SiC layer in step (2) and the LN layer in step (1) with plasma, bond the SiC film and the LN film, perform heat treatment, and remove the silicon oxide-silicon heterostructure above the SiC film in the bonded structure by deep silicon etching to obtain the substrate-LN-SiC heterostructure.
[0015] (4) Cover the SiC surface with a mask and pattern the optical waveguide, acoustic waveguide and acoustic scattering structure; etch the waveguide structure, and use the double-layer lift-off process and ion beam evaporation method to prepare the metal interdigitated structure on the etched SiC surface to make the overall device.
[0016] The preferred embodiment of the above preparation method is as follows:
[0017] In steps (1) to (3), plasma activation is performed using a gas containing at least one of argon, oxygen, and nitrogen, with an energy range of 500 eV to 2000 eV. After activation, at least one of an argon-rich layer, an oxygen-rich layer, and a nitrogen-rich layer can be formed on the surface of the thin film. The activated thin film surface is then directly bonded, and the bonding environment conditions include, but are not limited to, a vacuum environment and normal temperature and pressure. Furthermore, the bonding temperature is 20-700℃.
[0018] The heat treatment is an annealing process, the annealing atmosphere is nitrogen, the annealing temperature is 500℃~1400℃, and the annealing time is 1min~24h.
[0019] In steps (1) to (2), the thinning is to thin the film. First, mechanical grinding is used to reduce the thickness to 5μm to 8μm, and chemical mechanical polishing is used to grind it to 200nm to 1000nm, while ensuring that the surface roughness of the film is less than 0.3nm.
[0020] In step (2), on the SiC wafer <0001> A silicon oxide layer with a thickness of 100 nm to 5 μm is prepared on the surface of SiC, wherein methods including but not limited to thermal oxidation, plasma-enhanced chemical vapor deposition, low-pressure chemical vapor deposition, and physical vapor deposition are used. <0001> A silicon oxide layer is deposited on the surface.
[0021] In step (4), the optical waveguide includes an optical linear waveguide and an optical coupling waveguide, wherein the optical linear waveguide and the optical coupling waveguide are both SiC retention regions after dry etching of the SiC thin film; since SiC and LN have similar refractive indices, the light field is distributed in the optical linear waveguide and the LN thin film below it;
[0022] The acoustic waveguide includes an acoustic linear waveguide and an acoustic tapered coupled waveguide, wherein the acoustic linear waveguide, the acoustic tapered coupled waveguide, and the acoustic scattering structure are all LN regions after SiC layer etching; based on the characteristics of high sound velocity in SiC material and low sound velocity in LN material, the sound field can be localized within the acoustic waveguide in the LN thin film;
[0023] The optical linear waveguide and the acoustic linear waveguide are collinear serpentine structures, which can obtain the maximum sound field-optical field overlap. The collinear serpentine structure is a periodic structure composed of straight lines and semicircles, and its period number and length are related to the scattering between different optical modes in Brillouin scattering.
[0024] The optically coupled waveguide is located within the acoustic scattering structure and does not overlap with the acoustic waveguide region.
[0025] In step (4), the optical waveguide structure has a thickness of 200nm to 800nm and a width of 200nm to 1μm; the acoustic waveguide structure has a thickness of 500nm to 5μm and a width of 1μm to 10μm; and the semicircular radius in the collinear serpentine structure is 750nm to 7.5μm.
[0026] The metal interdigitated structure in step (4) is placed inside the acoustic tapered coupling waveguide. The metal interdigitated structure is a dual-electrode interdigitated structure composed of metal fingers, used to form Lamb waves and Rayleigh waves that can be stably transmitted in the acoustic waveguide. Its frequency is between 80MHz and 10GHz, which can meet the Brillouin scattering conditions between different modes in the optical waveguide.
[0027] In step (4), the pattern transfer of optical waveguide, acoustic waveguide and acoustic scattering structure on the mask is performed on the SiC layer by electron beam exposure, and the corresponding structure is fabricated by dry etching.
[0028] The mask is patterned into a metal interdigitated structure using a double-layer lift-off process, and the mask is PDMS. Metal electrodes are deposited in the maskless area using electron beam evaporation, with a deposition thickness of 100 nm to 200 nm. Unexposed mask is removed using a stripper, which is at least one of concentrated sulfuric acid, acetone, and alcohol. The metal electrodes are heat-treated using a low-temperature annealing process, with an annealing temperature of 100°C to 250°C and an annealing time of 1 min to 3 min. The metal electrodes are at least one of aluminum, copper, and titanium.
[0029] This invention discloses an application of the waveguide device in an integrated acousto-optic chip, wherein the principle of the integrated acousto-optic chip is stimulated Brillouin scattering, and the application of the integrated acousto-optic chip includes, but is not limited to, acousto-optic modulation chips, non-reciprocal optical transmission, and on-chip Brillouin lasers.
[0030] One waveguide device of the present invention is based on stimulated Brillouin scattering and can realize applications such as acousto-optic modulation chips, non-reciprocal optical transmission, and on-chip Brillouin lasers.
[0031] This invention designs a novel non-reciprocal waveguide device based on acoustic-optical coupling and its fabrication method. The non-reciprocal waveguide device includes a substrate, a SiC-LN heterostructure thin film, and a metal interdigitated structure. The SiC-LN heterostructure thin film contains collinear, serpentine optical and acoustic waveguides, as well as a semi-circular acoustic scattering structure to isolate the optical coupling from the surface acoustic wave (SAW). A SAW is excited using a dual-electrode interdigitated structure, which can stably propagate in the acoustic waveguide and is positioned above the SiC-LN heterostructure thin film. The fabrication process includes: directly bonding an LN wafer and a SiC insulating substrate using plasma activation; and... <0001> A silicon oxide layer is formed on the surface, and it is directly bonded to the silicon oxide-silicon substrate along the silicon oxide surface; submicron-thick on-chip LN and SiC films are obtained by grinding, and the two are directly bonded along the LN and SiC surfaces; a SiC / LN / SiC heterostructure is fabricated using deep silicon etching; optical waveguides, acoustic waveguides, and acoustic scattering structures are fabricated in the SiC layer using ion beam exposure and dry etching; a metal interdigitated structure is fabricated on top of the SiC-LN heterostructure to obtain a complete non-reciprocal waveguide device.
[0032] This invention proposes a strategy for fabricating high-performance, easily implementable acousto-optic coupling devices by collinearly assembling acoustic and optical waveguides on a single chip. Utilizing a special integration process, the excellent acousto-optic properties of LN material and the easy fabrication of SiC material are combined to create a wafer-level material platform consisting of SiC thin films, LN thin films, and a SiC substrate. Based on the refractive index contrast and material acoustic velocity differences, a waveguide coupling structure capable of simultaneously confining optical waves and surface acoustic waves is designed, achieving high-overlap inter-field coupling. Combining interdigitated electrodes, grating-cone couplers, and waveguide structures satisfies the inter-mode scattering condition in Brillouin scattering, enabling efficient unidirectional conversion between different optical modes and achieving on-chip optical non-reciprocity. Furthermore, the addition of an acoustic wave scattering structure allows for rapid dissipation of surface acoustic waves at the optical coupling device, solving the problem of decoupling optically coupled waveguides in acousto-optic coupling. This invention, to a certain extent, fills a design gap in acousto-optic coupling devices and is of great significance for future manipulation of multi-physics coupling, including on-chip acoustic, electric, and optical fields.
[0033] Beneficial effects
[0034] This invention combines the superior material properties of LN and SiC, utilizing a special wafer integration method and easily implemented fabrication technology to obtain a waveguide coupling structure based on a SiC / LN / SiC heterostructure. This structure can locally confine light waves and surface acoustic waves. By combining a metal interdigital structure, a grating coupler, and an acoustic wave scattering structure, a high-field overlap and long-coupling-distance acousto-optic coupling effect can be achieved, thus obtaining a non-reciprocal waveguide that satisfies the intermode scattering conditions. This design effectively solves the problems of low physical field overlap and low coupling efficiency in current on-chip integrated acousto-optic devices, and is of great significance for realizing multi-dimensional control of multiple physical fields within integrated optical chips. Attached Figure Description
[0035] Figure 1 This is a schematic diagram illustrating the fabrication process of the waveguide device of this application;
[0036] Figure 2 These are top and side views of the waveguide device structure of this application. Detailed Implementation
[0037] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.
[0038] Example 1
[0039] A waveguide device includes: a substrate, a SiC-LN heterostructure, and a metal interdigitated structure, wherein the SiC-LN heterostructure is disposed on the substrate, and the metal interdigitated structure is disposed on the SiC-LN heterostructure; the SiC-LN heterostructure is a bonding structure of a SiC thin film and an LN thin film; wherein the SiC-LN heterostructure contains an optical waveguide, an acoustic waveguide, and an acoustic scattering structure; the substrate is a SiC substrate; the SiC-LN heterostructure contains collinear optical waveguides, acoustic waveguides, and relatively independent acoustic scattering structures;
[0040] The optical waveguide includes an optical linear waveguide and an optical coupling waveguide; the optical waveguide is disposed within a SiC thin film; the optical coupling waveguide is at least one of a grating waveguide and a tapered waveguide, and further, in this embodiment, a tapered waveguide is selected;
[0041] The acoustic waveguide includes an acoustic linear waveguide and an acoustic tapered coupled waveguide; the acoustic scattering structure is a semi-circular structure; the acoustic waveguide and the acoustic scattering structure are disposed in a SiC-LN heterostructure thin film (the SiC thin film after the acoustic waveguide and the acoustic scattering structure are etched is defined within the LN thin film).
[0042] The optical waveguide structure has a thickness of 200nm to 800nm and a width of 200nm to 1μm; the acoustic waveguide structure has a thickness of 500nm to 5μm and a width of 1μm to 10μm; the optical and acoustic linear waveguides are collinear serpentine structures; the semicircular radius of the collinear serpentine structure is 750nm to 7.5μm; the optical coupling waveguide is disposed within the acoustic scattering structure and does not overlap with the acoustic waveguide region; the metal interdigitated structure is disposed within the acoustic tapered coupling waveguide.
[0043] Example 2
[0044] (1) Provide LN wafer 1 and SiC substrate 2. Use low-energy oxygen plasma with activation energy of 1.5keV to treat the surface of LN wafer and SiC substrate to form an oxygen-rich layer about 2nm deep. Directly bond the substrate under normal temperature and pressure and vacuum environment to form bonding structure 3. Anneal the bonding structure 3 under nitrogen atmosphere at 1000℃ for 2 hours.
[0045] (2) The LN film in the bonding structure is thinned to 5 μm by mechanical grinding to obtain thinned structure 4; the thinned structure 4 is thinned to 700 nm by chemical mechanical polishing to obtain LN film 5 on insulator, and the surface roughness of LN film is kept below 0.3 nm.
[0046] (3) Provide a low-doped SiC wafer 6 and a silicon oxide-silicon substrate 7, and use plasma-enhanced chemical vapor deposition to deposit silicon oxide on the SiC wafer 6. <0001> A silicon oxide layer with a thickness of 400 nm is prepared on the surface, and chemical mechanical polishing is used to make the surface roughness of the silicon oxide side of both SiC wafer 6 and silicon oxide-silicon substrate 7 less than 0.3 nm.
[0047] (4) The oxide surfaces of both SiC wafer 6 and silicon oxide-silicon substrate 7 were treated with 1.5keV low-energy argon plasma, and then an argon-rich layer of about 2nm depth was formed on the surfaces of the two wafers. The bonding structure 8 was formed by direct bonding under normal temperature and pressure and vacuum environment. The bonding structure 8 was annealed in nitrogen atmosphere at 1200℃ for 2 hours.
[0048] (5) The SiC film in the bonded structure is thinned to 5 μm by mechanical polishing to obtain the thinned structure 9; the thinned structure 9 is thinned to a 400 nm SiC film on an insulator 10 by chemical mechanical polishing, and the surface roughness of the SiC layer film is kept below 0.3 nm.
[0049] (6) The LN surface of the LN film 5 on the insulator and the SiC surface of the SiC film 10 on the insulator were treated with 1.5keV low-energy oxygen plasma, and then an oxygen-rich layer of about 2nm depth was formed on the two film surfaces. The bonded structure 11 was formed by direct bonding under normal temperature and pressure and vacuum environment. The bonded structure 11 was annealed in nitrogen atmosphere at 1500℃ for 2 hours.
[0050] (7) The top silicon layer of the bonding structure 11 was completely removed by deep silicon etching to obtain the SiC-LN-SiC heterostructure 12.
[0051] (8) Using a mask PDMS, supplemented by electron beam exposure and dry etching, an optical linear waveguide 13, a grating coupler 14, an acoustic waveguide 15 and an acoustic scatterer structure 16 are patterned on the heterostructure 12. The optical waveguide 13 has a width of 400 nm and a thickness of 400 nm. The acoustic waveguide 15 has a width of 2 μm and a thickness of 700 nm. The radius of the semi-circular curved portion of the optical waveguide 13 and the acoustic waveguide 15 in the serpentine structure is set to 4 μm. The etching process does not involve the LN thin film layer.
[0052] (9) Using a double-layer lift-off process, an Al metal interdigitated structure 17 is patterned on a PDMS mask, and an aluminum metal electrode is grown by electron beam evaporation to obtain a complete device structure 18.
[0053] (10) Perform a rapid thermal annealing treatment at 200°C on the device structure 18 for 1 minute to obtain the waveguide device.
[0054] The provided waveguide device fully leverages the advantages of the novel SiC / LN / SiC heterostructure, circumventing the difficulties in fabricating lithium niobate optical platforms, while simultaneously meeting the requirements of compatibility with traditional processes and on-chip integration. The collinear design of the acoustic and optical waveguides in this waveguide device enables high-field overlap and long-coupling-distance acousto-optic coupling effects, further achieving unidirectional optical mode conversion based on Brillouin scattering and corresponding optical non-reciprocity. In addition, the organic combination of the acoustic scattering structure and the coupled waveguide in this invention solves the decoupling problem caused by acoustic waves in traditional acousto-optic coupling devices, thereby achieving stable coupling between light and the chip, providing a general-purpose device foundation for the integrated design of large-scale on-chip photonic devices.
Claims
1. A waveguide device, characterized in that, The waveguide device includes: a substrate, a SiC-LN heterofilm, and a metal interdigitated structure, wherein the SiC-LN heterofilm is disposed on the substrate, and the metal interdigitated structure is disposed on the SiC-LN heterofilm; The SiC-LN heterostructure is a bonded structure of SiC and LN films; wherein the SiC-LN heterostructure contains optical waveguides, acoustic waveguides and acoustic scattering structures. The optical waveguide includes an optical linear waveguide and an optical coupling waveguide; the optical waveguide is the retained region after etching the SiC thin film. The acoustic waveguide includes an acoustic linear waveguide and an acoustic tapered coupled waveguide; the acoustic waveguide and acoustic scattering structure are LN regions after SiC layer etching; The optical linear waveguide and acoustic linear waveguide are collinear serpentine structures; wherein the collinear serpentine structure is a periodic structure composed of straight lines and semicircles; The optical coupling waveguide is located within the acoustic scattering structure, and its region does not overlap with that of the acoustic waveguide; the metal interdigitated structure is located within the acoustic tapered coupling waveguide; by combining the interdigitated electrodes, couplers, and waveguide structure, the intermode scattering condition in Brillouin scattering is satisfied, that is, efficient conversion between different optical modes can be achieved in one direction, thus obtaining on-chip optical non-reciprocity.
2. The waveguide device according to claim 1, characterized in that, The substrate is a SiC substrate; the optical coupling waveguide is at least one of a grating waveguide and a tapered waveguide; the acoustic scattering structure is a semi-circular structure.
3. The waveguide device according to claim 2, characterized in that, The optical waveguide structure has a thickness of 200nm~800nm and a width of 200nm~1μm; the acoustic waveguide structure has a thickness of 500nm~5μm and a width of 1μm~10μm; the semicircle radius in the collinear serpentine structure is 750nm~7.5μm.
4. A method for fabricating the waveguide device according to claim 1, comprising the following steps: (1) Plasma activation of LN wafer and substrate surface, on LN wafer <0001> The substrate is surface-bonded, heat-treated, and then the LN material is thinned to obtain an LN thin film; (2) On another SiC wafer <0001> A silicon oxide layer is prepared on the surface. The silicon oxide layer of the SiC wafer and the surface of the silicon oxide layer of another silicon oxide-silicon substrate are activated by plasma. The SiC wafer structure is bonded to the surface of another silicon oxide-silicon substrate along the silicon oxide surface. After heat treatment, the SiC material is thinned to obtain a SiC thin film on an insulator. (3) Using plasma to activate the surface of the SiC layer in step (2) and the LN layer in step (1), bond the SiC film and the LN film, perform heat treatment, remove the silicon oxide-silicon heterostructure above the SiC film in the bonded structure, and obtain the substrate-LN-SiC heterostructure. (4) Cover the SiC surface with a mask and pattern the optical waveguide, acoustic waveguide and acoustic scattering structure; The waveguide structure is etched, and a metal interdigitated structure is fabricated on the etched SiC surface to form an integral device.
5. The preparation method according to claim 4, characterized in that, In steps (1) to (3), plasma activation is performed: the gas includes at least one of argon, oxygen, and nitrogen, with an energy range of 500eV to 2000eV. After activation, at least one of argon-rich, oxygen-rich, and nitrogen-rich layers can be formed on the surface of the film. The activated film surface is then directly bonded, and the bonding environment conditions include at least one of vacuum environment and ambient temperature and pressure. The heat treatment is an annealing process, the annealing atmosphere is nitrogen, the annealing temperature is 500℃~1400℃, and the annealing time is 1min~24h.
6. The preparation method according to claim 4, characterized in that, In steps (1) to (2), the thinning is to thin the film. First, mechanical grinding is used to reduce the film to 5μm to 8μm, and chemical mechanical polishing is used to grind it to 200nm to 1000nm, while ensuring that the surface roughness of the film is less than 0.3nm. In step (2), on the SiC wafer <0001> A silicon oxide layer is prepared on the surface, with a thickness of 100 nm to 5 μm.
7. The preparation method according to claim 4, characterized in that, In step (4), the optical waveguide includes an optical linear waveguide and an optical coupling waveguide, wherein the optical linear waveguide and the optical coupling waveguide are both retained areas after the SiC thin film is dry etched; The acoustic waveguide includes an acoustic linear waveguide and an acoustic tapered coupled waveguide, wherein the acoustic linear waveguide, the acoustic tapered coupled waveguide, and the acoustic scattering structure are all LN regions after SiC layer etching; the optical linear waveguide and the acoustic linear waveguide are collinear serpentine structures, and the collinear serpentine structure is a periodic structure composed of straight lines and semicircles; The optically coupled waveguide is located within the acoustic scattering structure and does not overlap with the acoustic waveguide region.
8. The preparation method according to claim 4, characterized in that, The metal interdigitated structure in step (4) is placed inside the acoustic tapered coupling waveguide. The metal interdigitated structure is a dual-electrode interdigitated structure composed of metal fingers, used to form Lamb waves and Rayleigh waves that can be stably transmitted in the acoustic waveguide. The frequency is between 80MHz and 10GHz, which satisfies the Brillouin scattering condition between different modes in the optical waveguide.
9. The preparation method according to claim 4, characterized in that, In step (4), the pattern transfer of optical waveguide, acoustic waveguide and acoustic scattering structure on the mask is performed on the SiC layer by electron beam exposure method, and the corresponding structure is fabricated by dry etching. A dual-layer lift-off process was used to pattern the mask into a metal interdigitated structure, and the mask was made of PDMS. A metal electrode is deposited in the maskless area using electron beam evaporation, with a deposition thickness of 100 nm to 200 nm. The unexposed mask is removed using a stripper, which is at least one of concentrated sulfuric acid, acetone, and alcohol. The metal electrode is heat-treated using a low-temperature annealing process, with an annealing temperature of 100°C to 250°C and an annealing time of 1 min to 3 min. The metal electrode is at least one of aluminum, copper, and titanium.
10. An integrated acousto-optic chip, characterized in that, The integrated acousto-optic chip includes the waveguide device described in claim 1.