A broadband and efficient acousto-optic modulator in shear wave mode and a preparation method thereof

Abstract

The application discloses a wideband and high-efficiency acousto-optic modulator in a shear wave mode and a preparation method thereof, and relates to the technical field of integrated optics. The acousto-optic modulator comprises, from bottom to top, a silicon substrate, a silicon dioxide layer and a lithium niobate-chalcogenide glass hetero layer. The lithium niobate-chalcogenide glass hetero layer comprises a lithium niobate thin film, a chalcogenide optical waveguide, an interdigital transducer and a reflection grating which are hetero-integrated on the lithium niobate thin film. The reflection gratings are symmetrically arranged about the interdigital transducer, and an oblique included angle is formed between the interdigital transducer and the chalcogenide optical waveguide. The acousto-optic modulator comprehensively utilizes the excellent acousto-optic characteristics of chalcogenide glass materials, the outstanding piezoelectric effect of the lithium niobate thin film and the oblique included angle arrangement of the interdigital transducer relative to the optical waveguide. The mechanical deformation of the horizontal shear wave in the acoustic aperture direction is fully utilized, the reflection grating is used for the enhancement of the acoustic wave, the Q value of the acoustic wave resonant cavity is improved, the modulation bandwidth is improved, and the problem of low acousto-optic modulation efficiency is solved.

Description

Technical Field

[0001] This invention relates to the field of integrated optical technology, and in particular to a novel broadband and efficient acousto-optic modulator operating in shear wave mode and its fabrication method. Background Technology

[0002] An acousto-optic modulator mainly consists of a piezoelectric transducer and an acousto-optic medium. It can be used to change the intensity, propagation direction, and phase of a light beam. Its basic principle is that when an input signal drives the transducer, the transducer generates ultrasonic waves with the same frequency as the input signal, which are then transmitted into the acousto-optic medium. This causes a periodic change in the refractive index of the acousto-optic medium. When the light beam passes through the acousto-optic medium, an interaction occurs, loading the signal onto the light for transmission. The advent of interdigital transducers has greatly improved the performance of surface acoustic wave (SAW) acousto-optic devices, enhancing the integration of optical systems and strengthening their information transmission and processing capabilities. These devices are widely used in optical signal processing, optical communication, and optical computing. To date, researchers have used SAW technology to create various acousto-optic devices with different functions, such as acousto-optic modulators, acousto-optic deflectors, acousto-optic filters, and acousto-optic Q-switched lasers, which are widely used in optical communication systems, optical communication equipment, and military applications. However, traditional acousto-optic modulation devices have low electromechanical and optomechanical coupling coefficients during multi-field coupling, resulting in low surface acoustic wave modulation bandwidth and acousto-optic modulation efficiency. Therefore, improving the modulation bandwidth while solving the problem of low acousto-optic modulation efficiency is of great significance for the research of acousto-optic modulation. Summary of the Invention

[0003] The purpose of this invention is to provide a broadband and efficient acousto-optic modulator and its fabrication method in shear wave operation mode. It comprehensively utilizes the excellent acousto-optic properties of chalcogenide glass materials and the prominent piezoelectric effect of lithium niobate thin film. The interdigital transducer is placed at an inclined angle relative to the optical waveguide, which makes full use of the mechanical deformation generated by the horizontal shear wave in the direction of the acoustic aperture. At the same time, a reflective grating is used to enhance the acoustic wave and improve the Q value of the acoustic resonant cavity, thereby increasing the modulation bandwidth and solving the problem of low acousto-optic modulation efficiency.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] A broadband, high-efficiency acousto-optic modulator operating in shear wave mode includes: a silicon substrate, a silicon dioxide layer, and a lithium niobate-chalcogenide glass heterostructure layer arranged sequentially from bottom to top. The lithium niobate-chalcogenide glass heterostructure layer includes a lithium niobate thin film and a chalcogenide optical waveguide heterogeneously integrated on the lithium niobate thin film. An interdigital transducer and a reflective grating are also disposed on the lithium niobate thin film. The interdigital transducer adopts a single-electrode or dual-electrode structure. A plurality of the reflective gratings are symmetrically arranged about the interdigital transducer, and an inclined angle is formed between the interdigital transducer and the chalcogenide optical waveguide.

[0006] Driven by an external radio frequency signal, the interdigital transducer generates surface acoustic waves through the inverse piezoelectric effect of the lithium niobate thin film. The generated surface acoustic waves are transmitted to the chalcogenide optical waveguide, realizing the interaction between the sound field and the optical field.

[0007] Furthermore, the lithium niobate-chalcogenide glass heterolayer is in a non-suspended state relative to the silicon substrate.

[0008] Furthermore, the chalcogenide optical waveguide is an MZI-type optical waveguide, an RT racetrack-type optical waveguide, a one-dimensional photonic crystal nanobeam, a two-dimensional photonic crystal resonator, or an optomechanical resonant cavity waveguide structure.

[0009] Furthermore, the chalcogenide optical waveguide is an MZI-type optical waveguide, and the upper arm of the MZI-type optical waveguide is composed of four 90-degree small bending radius waveguides and a straight waveguide.

[0010] Furthermore, the reflective grating is provided in two sets, respectively located on both sides of the interdigital transducer; wherein the interdigital transducer is located on the inner side of the chalcogenide optical waveguide, and the two sets of reflective gratings are located on the outer side of the chalcogenide optical waveguide; or, the interdigital transducer is located on the outer side of the chalcogenide optical waveguide, and the two sets of reflective gratings are respectively located on the outer side and the inner side of the chalcogenide optical waveguide.

[0011] Furthermore, the thickness of the lithium niobate film is 100nm to 1500nm; the interdigital transducer can excite horizontal shear waves of 100MHz to 10GHz; the width of the chalcogenide optical waveguide is 300nm to 30um, the height is 350nm to 2500nm, and the operating wavelength is 800nm ​​to 10000nm.

[0012] Furthermore, the tangential orientation of the lithium niobate film is X-(-10°)Y.

[0013] Furthermore, the tilt angle between the interdigital transducer and the chalcogenide waveguide is between 0 and 85 degrees.

[0014] Furthermore, the reflective grating and the interdigital transducer form a high-Q acoustic resonator. The reflective gratings are arranged periodically, and the arrangement period of multiple reflective gratings satisfies the acoustic Bragg reflection condition. The number of pairs of reflective gratings is set to 50 to 100.

[0015] This invention also provides a method for fabricating a broadband, high-efficiency acousto-optic modulator in shear wave mode, applicable to the aforementioned broadband, high-efficiency acousto-optic modulator in shear wave mode, comprising the following steps:

[0016] S1, a chalcogenide glass film is deposited on a silicon substrate covered with a silicon dioxide layer and a lithium niobate film by thermal evaporation.

[0017] S2, the fabrication of chalcogenide optical waveguides can be completed by exposure, development and etching on a chalcogenide glass film;

[0018] S3 involves a second exposure and development process. A metal film is deposited on the chalcogenide glass film after the second exposure and development using vapor deposition or micro-electroplating. After a stripping process, the interdigital transducer and reflector grid can be fabricated.

[0019] Furthermore, in step S2, the fabrication of the chalcogenide optical waveguide is completed by exposure, development, and etching on the chalcogenide glass thin film, specifically including:

[0020] S201. Using an electron beam direct writing system, positive electron paste is exposed onto a deposited chalcogenide glass film with a thickness of approximately 400 nm. After baking on a hot plate at 130°C for 5 minutes, and then developing with xylene, a mask pattern corresponding to the shape of the chalcogenide optical waveguide can be obtained on the electron paste.

[0021] S202. Using reactive ion etching equipment, the mask pattern obtained on the electronic adhesive is used as a mask, and dry etching is performed with CHF3 gas and argon gas. The sidewall morphology is required to be smooth and steep. The etching power is set to 60W, the etching gas pressure is 60mTorr, and the etching gas flow rate is 25 and 30sccm.

[0022] S203. Place the etched silicon substrate into the chamber and use oxygen plasma etching gas to remove the residual electron adhesive on top. The gas flow rate is 50 sccm, the RF power is 20W, and the inductively coupled plasma (ICP) power is 1000W. After the process is completed, the mask pattern can be transferred and the chalcogenide optical waveguide can be fabricated.

[0023] According to specific embodiments provided by the present invention, the following technical effects are disclosed: The broadband and efficient acousto-optic modulator and its fabrication method provided by the present invention in shear wave mode have the following advantages: First, based on a hybrid heterogeneous integrated waveguide structure of lithium niobate and chalcogenide glass, the excellent piezoelectric effect of lithium niobate and the significant elasto-optic effect of chalcogenide glass are fully utilized, significantly improving the refractive index change generated by the optical waveguide; Second, using an X-(-10°)Y tangential lithium niobate thin film as the piezoelectric material significantly improves the electromechanical coupling coefficient; Third, using horizontal shear waves for acousto-optic modulation effectively solves the problem of narrow acoustic wave modulation bandwidth; Fourth, the interdigital transducer and the chalcogenide optical waveguide are set at an inclined angle, fully utilizing the mechanical deformation of the horizontal shear wave and improving the modulation efficiency of the horizontal shear wave on light; Fifth, symmetrical reflection gratings are set on both sides of the interdigital transducer to form an acoustic resonant cavity, enhancing the acoustic wave amplitude through Bragg reflection. Compared with the existing technology, the present invention will fill the gap in high-bandwidth acousto-optic modulators. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a top view schematic diagram of the broadband high-efficiency acousto-optic modulator in shear wave mode according to Embodiment 1 of the present invention;

[0026] Figure 2 This is a flowchart illustrating the fabrication method of a broadband, high-efficiency acousto-optic modulator in shear wave mode according to Embodiment 1 of the present invention.

[0027] Figure 3 This is a top view schematic diagram of the broadband high-efficiency acousto-optic modulator in the shear wave operating mode of Embodiment 2 of the present invention;

[0028] Figure 4 This is a flowchart of the fabrication method of the broadband high-efficiency acousto-optic modulator in the shear wave operating mode in Embodiment 2 of the present invention;

[0029] Figure 5 This is a schematic diagram of a test system for a broadband, high-efficiency acousto-optic modulator operating in shear wave mode according to an embodiment of the present invention.

[0030] Explanation of reference numerals in the attached figures: 1. Si (silicon); 2. SiO2 (silicon dioxide); 3. LiNbO3 (lithium niobate); 4. ChG (chalcogenide glass); 5. Au (gold); 6. Resist (anti-corrosion coating, which is electronic adhesive or photoresist); 7. Chalcogenide waveguide; 8. Reflector grating; 9. Interdigital transducer. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The purpose of this invention is to provide a broadband and efficient acousto-optic modulator and its fabrication method in shear wave operation mode. It comprehensively utilizes the excellent acousto-optic properties of chalcogenide glass, the high electromechanical coupling coefficient of the X-(-10°)Y tangential lithium niobate thin film, and the high bandwidth of horizontal shear waves. Four waveguides with small 90-degree bending radii are set on one arm to flexibly adjust the distance between the waveguide and the interdigital transducer. A metal reflective grating is used to enhance the acoustic waves of the single-arm and double-arm modulation structures. The tilt angle between the interdigital transducer and the chalcogenide optical waveguide is adjusted to maximize the utilization of the mechanical strain of the horizontal shear wave. This invention first solves the problem of narrow modulation bandwidth in traditional acousto-optic modulators, and secondly, it solves the problem of low modulation efficiency of horizontal shear waves.

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] like Figures 1 to 4 As shown, the broadband, high-efficiency acousto-optic modulator in shear wave mode provided by the present invention includes: a silicon substrate, a silicon dioxide layer, and a lithium niobate-chalcogenide glass heterostructure layer arranged sequentially from bottom to top. The lithium niobate-chalcogenide glass heterostructure layer includes a lithium niobate thin film and a chalcogenide optical waveguide 7 heterogeneously integrated on the lithium niobate thin film. An interdigital transducer 9 and a reflective grating 8 are also disposed on the lithium niobate thin film. The interdigital transducer 9 adopts a single-electrode or dual-electrode structure. A plurality of reflective gratings 8 are symmetrically arranged about the interdigital transducer 9, and an inclined angle is formed between the interdigital transducer 9 and the chalcogenide optical waveguide 7. This inclined angle fully utilizes the mechanical deformation generated by the horizontal shear wave in the acoustic aperture direction of the interdigital transducer 9. For example, the inclined angle between the interdigital transducer 9 and the chalcogenide optical waveguide 7 can be between 0 and 85 degrees.

[0035] The interdigital transducer 9 includes a plurality of interdigital electrodes. The interdigital transducer, with its dual-electrode structure, can effectively improve the acoustic bandwidth. The reflective grating 8 is a metal reflective grating.

[0036] Driven by an external radio frequency signal, the interdigital transducer generates surface acoustic waves through the inverse piezoelectric effect of the lithium niobate thin film. The generated surface acoustic waves are transmitted to the chalcogenide optical waveguide, realizing the interaction between the sound field and the optical field.

[0037] The silicon substrate is formed using silicon 1, a silicon dioxide layer is formed on the silicon substrate using silicon dioxide 2, a lithium niobate thin film is formed on the silicon dioxide layer using lithium niobate 3, the interdigitated transducer and the reflective grating are made of gold 5, and the chalcogenide optical waveguide is made of chalcogenide glass 4.

[0038] Specifically, the lithium niobate-chalcogenide glass heterolayer is in a non-suspended state relative to the silicon substrate.

[0039] For example, the chalcogenide optical waveguide is an MZI-type optical waveguide, an RT racetrack-type optical waveguide, a one-dimensional photonic crystal nanobeam, a two-dimensional photonic crystal resonator, or an optomechanical resonant cavity waveguide structure. Preferably, the chalcogenide optical waveguide is an MZI-type optical waveguide, and the upper arm of the MZI-type optical waveguide is composed of four 90-degree small bending radius waveguides and a straight waveguide.

[0040] The reflective grating and the interdigital transducer form a high-Q acoustic resonator. The reflective gratings are arranged periodically, and the arrangement period of multiple reflective gratings satisfies the Bragg reflection condition for acoustic waves.

[0041] The two sets of reflective gratings are arranged in pairs; for example, the number of pairs of reflective gratings is set to 50 to 100.

[0042] The thickness of the lithium niobate film is 100nm to 1500nm; the interdigital transducer can excite horizontal shear waves of 100MHz to 10GHz and can achieve a working bandwidth of 400MHz to 600MHz; the width of the chalcogenide optical waveguide is 300nm to 30um, the height is 350nm to 2500nm, and the working wavelength is 800nm ​​to 10000nm.

[0043] Specifically, the lithium niobate film has a tangential orientation of X-(-10°)Y, under which the horizontal shear wave excited has the highest electromechanical coupling coefficient and the largest acoustic bandwidth. Here, X-(-10°)Y means that the sound wave propagates along the Y-axis in a direction that is cut along the X-axis and rotated 10 degrees clockwise.

[0044] The working principle of the broadband high-efficiency acousto-optic modulator in the shear wave mode is as follows:

[0045] The process of microwave input generating surface acoustic waves (SAWs) is based on the inverse piezoelectric coupling effect of a lithium niobate thin film. An interdigital transducer converts the input microwave signal into a SAW signal on the lithium niobate film, causing a mechanical strain field distribution on the film. The horizontal shear wave generated on the surface of the lithium niobate film further acts on the optical waveguide. This process, based on optomechanical coupling effects (moving boundary effect, elasto-optic effect, electro-optic effect), alters the optical refractive index of the waveguide. This refractive index change can be further converted into a phase change using waveguide structures such as MZI-type waveguides, RT racetrack-type waveguides, one-dimensional photonic crystal nanobeams, two-dimensional photonic crystal resonators, or optomechanical resonant cavities. A metal reflective grating reflects the acoustic wave excited by the interdigital transducer. The reflected acoustic wave coherently and constructively interacts with the excited acoustic wave, greatly enhancing the amplitude of the acoustic wave and significantly strengthening the acousto-optic interaction.

[0046] This invention also provides a method for fabricating a broadband, high-efficiency acousto-optic modulator in shear wave mode, applicable to the aforementioned broadband, high-efficiency acousto-optic modulator in shear wave mode, comprising the following steps:

[0047] S1, a chalcogenide glass film is deposited on a silicon substrate covered with a silicon dioxide layer and a lithium niobate film by thermal evaporation.

[0048] S2, the fabrication of chalcogenide optical waveguides can be completed by exposure, development and etching on a chalcogenide glass film;

[0049] S3 involves a second exposure and development process. A metal film is deposited on the chalcogenide glass film after the second exposure and development using vapor deposition or micro-electroplating. After a stripping process, the interdigital transducer and reflector grid can be fabricated.

[0050] Example 1:

[0051] like Figure 1 As shown in Embodiment 1, two sets of reflective gratings 8 are provided, located on both sides of the interdigital transducer 9. In the single-arm modulation structure at a specific frequency, the interdigital transducer 9 is located on the outer side of the chalcogenide waveguide 7, and the two sets of reflective gratings 8 are respectively located on the outer and inner sides of the chalcogenide waveguide 7. The two sets of reflective gratings 8 on the inner and outer sides of the chalcogenide waveguide 7 are symmetrical about the interdigital transducer 9, and their placement maximizes the acoustic wave amplitude.

[0052] At a specific frequency, the interdigital transducer in the single-arm modulation structure satisfies the impedance matching condition, and the interdigital transducer is placed on one side of the chalcogenide optical waveguide.

[0053] like Figure 2 As shown, taking a chalcogenide optical waveguide as an MZI type optical waveguide as an example, the fabrication method of the broadband high-efficiency acousto-optic modulator in the shear wave operating mode in Example 1 is explained. The specific steps are as follows:

[0054] S1. GeO with a thickness of 850 nm is deposited on a silicon substrate covered with a lithium niobate thin film using a thermal evaporation method. 25 Sb 10 S 65 Chalcogenide glass thin films;

[0055] S2. Using an electron beam direct writing system (EBL, Vistec EBPG5000+), positive electron adhesive (APR6200) is exposed onto a pre-prepared ChG film with a thickness of approximately 400 nm. After baking on a hot plate at 130°C for 5 minutes, the mask pattern of MZI shape is obtained on the electron adhesive after development with xylene.

[0056] S3. Using reactive ion etching equipment, the pattern obtained on the electronic adhesive is used as a mask, and dry etching is performed with CHF3 gas and argon gas. The sidewall morphology is required to be smooth and steep. The etching power is set to 60W, the etching gas pressure is 60mTorr, and the etching gas flow rate is 25 and 30sccm.

[0057] S4. Place the etched substrate into the chamber and use oxygen plasma etching gas to remove the residual electron adhesive on the top. The gas flow rate is 50 sccm, the RF power is 20W, and the inductively coupled plasma (ICP) power is 1000W. After the process is completed, the transfer of the MZI pattern on the substrate can be completed.

[0058] S5. Using an electron beam direct writing system (EBL, Vistec EBPG5000+), positive electron paste (APR6200) is exposed onto the etched substrate with a thickness of approximately 500 nm. After baking on a hot plate at 130°C for 5 minutes, the mask pattern of the interdigital transducer and reflective grating can be obtained on the electron paste after development with xylene.

[0059] S6. Deposit a gold layer with a thickness of approximately 100 nm on the substrate after development and exposure using a thermal evaporation method;

[0060] S7. Immerse the deposited substrate in an organic solution (such as acetone) to remove the electron glue and metal film on the substrate surface, thus completing the fabrication of the interdigital transducer and reflective grating.

[0061] like Figure 5 The diagram shown is a schematic of the test system corresponding to this invention. The test system mainly includes: a tunable quantum cascade laser, an erbium-doped fiber amplifier, a photodetector, a vector network analyzer, and a spectrometer.

[0062] During testing, a microwave signal of a certain frequency is applied to the interdigital transducer. Under the inverse piezoelectric effect of the lithium niobate thin film, converging surface acoustic waves propagate to both sides. These acoustic waves act on the optical waveguide, completing the microwave-to-optical conversion. The acoustic waves alter the equivalent refractive index of the optical waveguide, further changing the phase of the optical signal and ultimately achieving intensity modulation. The output optical signal is converted into an electrical signal by a photodetector, and the S-wavelength of the modulated signal can be obtained after passing through a network analyzer. 21 Transmission spectrum, on the one hand, can be obtained through S 21 The acousto-optic modulation bandwidth can be calculated from the transmission spectrum, and on the other hand, it can be obtained by analyzing S... 21Transmission spectrum analysis can calculate the voltage required to change the π phase. Multiplying the calculated voltage by the modulation region length yields the half-wave voltage-length product, allowing evaluation of the acousto-optic modulator's conversion efficiency and modulation performance. Passing the output signal through a spectrometer allows observation of the modulated first-order sideband signal, and the maximum conversion efficiency of the sideband can be calculated.

[0063] Example 2:

[0064] like Figure 3 As shown in Embodiment 2, two sets of the reflective grating 8 are provided, located on both sides of the interdigital transducer 9; in the dual-arm modulation structure at a specific frequency, the interdigital transducer 9 is located inside the chalcogenide optical waveguide, and the two sets of the reflective grating 8 are located outside the two arms of the chalcogenide optical waveguide 7; the distance between the reflective grating 8 and the chalcogenide optical waveguide 7 can maximize the increase of the acoustic wave amplitude.

[0065] At a specific frequency, the interdigitated transducer of the dual-arm modulation structure has an odd number of interdigitated indices for the MZI type optical waveguide and an even number of interdigitated indices for the RT racetrack type optical waveguide. The interdigitated transducer is placed between the two arms of the optical waveguide, and the center distance from the two arms of the optical waveguide is the same.

[0066] Embodiment 2 of this invention provides a broadband, high-efficiency acousto-optic modulator operating in MZI-type dual-arm shear wave mode. It mainly comprises an odd-pair interdigital transducer on a lithium niobate thin film, a metal reflective grating, and a heterogeneously integrated chalcogenide MZI-type optical waveguide on the thin film. The waveguide operates in the communication band near 1550 nm. The interdigital transducers generate 1 GHz surface acoustic waves while achieving a bandwidth of 400 MHz to 600 MHz. Placing the interdigital transducers within the optical waveguide allows for full utilization of acoustic energy while performing push-pull modulation. The reflective grating outside the two arms significantly enhances the acoustic wave intensity, greatly improving the acousto-optic interaction intensity.

[0067] like Figure 4 As shown, the specific steps of the fabrication method of the broadband high-efficiency acousto-optic modulator based on the MZI-type double-arm shear wave operating mode are as follows:

[0068] S1. A Ge25Sb10S65 chalcogenide glass film with a thickness of 850 nm was deposited on a lithium niobate film substrate by thermal evaporation.

[0069] S2. Using an electron beam direct writing system (EBL, Vistec EBPG5000+), positive electron paste (APR6200) is exposed onto a pre-prepared ChG film with a thickness of approximately 400 nm. After baking on a hot plate at 130°C for 5 min, the mask pattern of MZI shape is obtained on the electron paste after development with xylene.

[0070] S3. Using reactive ion etching equipment, the pattern obtained on the electronic adhesive is used as a mask, and dry etching is performed with CHF3 gas and argon gas. The sidewall morphology is required to be smooth and steep. The etching power is set to 60W, the etching gas pressure is 60mTorr, and the etching gas flow rate is 25 and 30sccm.

[0071] S4. Place the etched substrate into the chamber and use oxygen plasma etching gas to remove the residual electron adhesive on the top. The gas flow rate is 50 sccm, the RF power is 20W, and the inductively coupled plasma (ICP) power is 1000W. After the process is completed, the transfer of the MZI pattern on the substrate can be completed.

[0072] S5. Using an electron beam direct writing system (EBL, Vistec EBPG5000+), positive electron paste (APR6200) is exposed on the etched substrate with a thickness of approximately 500 nm. After baking on a hot plate at 130°C for 5 minutes, the mask pattern of the interdigital transducer and reflective grating can be obtained on the electron paste after development with xylene.

[0073] S6. Deposit a gold layer with a thickness of approximately 100 nm on the substrate after development and exposure using a thermal evaporation method;

[0074] S7. Immerse the deposited substrate in an organic solution (such as acetone) to remove the electron glue and metal film on the substrate surface, thus completing the fabrication of the interdigital transducer and reflective grating.

[0075] The testing system and testing steps corresponding to this second embodiment are the same as those in the first embodiment.

[0076] In summary, the novel broadband and efficient acousto-optic modulator and its fabrication method provided by this invention, operating under shear wave mode, achieves the following: First, based on a hybrid heterogeneous integrated waveguide structure of lithium niobate and chalcogenide glass, it fully leverages the excellent piezoelectric effect of lithium niobate and the significant elasto-optic effect of chalcogenide glass, significantly improving the refractive index change generated by the optical waveguide. Second, the use of X-(10°)Y lithium niobate thin film as the piezoelectric material significantly improves the electromechanical coupling coefficient. Third, the use of horizontal shear waves for acousto-optic modulation effectively solves the problem of narrow acoustic modulation bandwidth. Fourth, the interdigital transducer is placed at an inclined angle to the optical waveguide, fully utilizing the deformation of the horizontal shear wave and improving the modulation efficiency of the horizontal shear wave on light. Fifth, metal reflective gratings are placed at both ends of the interdigital transducer to form an acoustic resonant cavity, enhancing the acoustic wave amplitude through Bragg reflection. Compared with existing technologies, this proposed scheme will fill the gap in high-bandwidth acousto-optic modulators.

[0077] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A broadband, high-efficiency acousto-optic modulator operating in shear wave mode, characterized in that, include: The following layers are arranged sequentially from bottom to top: a silicon substrate, a silicon dioxide layer, and a lithium niobate-chalcogenide glass heterostructure. The lithium niobate-chalcogenide glass heterostructure includes a lithium niobate thin film and a chalcogenide optical waveguide heterogeneously integrated on the lithium niobate thin film. An interdigital transducer and a reflective grating are also disposed on the lithium niobate thin film. The interdigital transducer adopts a single-electrode or dual-electrode structure. A plurality of the reflective gratings are symmetrically arranged about the interdigital transducer. An inclined angle is formed between the interdigital transducer and the chalcogenide optical waveguide. The reflective grating is provided in two sets, located on both sides of the interdigital transducer; wherein the interdigital transducer is located on the inner side of the chalcogenide optical waveguide, and the two sets of reflective gratings are located on the outer side of the chalcogenide optical waveguide; or, the interdigital transducer is located on the outer side of the chalcogenide optical waveguide, and the two sets of reflective gratings are located on the outer side and the inner side of the chalcogenide optical waveguide, respectively. The reflective grating and the interdigital transducer form a high-Q acoustic resonator. The reflective gratings are arranged periodically, and the arrangement period of multiple reflective gratings satisfies the Bragg reflection condition for acoustic waves.

2. The broadband, high-efficiency acousto-optic modulator in shear wave mode according to claim 1, characterized in that, The lithium niobate-chalcogenide glass heterolayer is in a non-suspended state relative to the silicon substrate.

3. The broadband, high-efficiency acousto-optic modulator in shear wave mode according to claim 1, characterized in that, The thickness of the lithium niobate film is 100nm to 1500nm; the interdigital transducer can excite horizontal shear waves of 100MHz to 10GHz; the width of the chalcogenide optical waveguide is 300nm to 30um, the height is 350nm to 2500nm, and the operating wavelength is 800nm ​​to 10000nm.

4. The broadband, high-efficiency acousto-optic modulator in shear wave mode according to claim 1, characterized in that, The tangential orientation of the lithium niobate film is X-(-10°)Y.

5. The broadband, high-efficiency acousto-optic modulator in shear wave mode according to claim 1, characterized in that, The tilt angle between the interdigital transducer and the chalcogenide waveguide is between 0 and 85 degrees.

6. The broadband, high-efficiency acousto-optic modulator in shear wave mode according to claim 1, characterized in that, The number of pairs of the reflective gratings is set to 50 to 100.

7. A method for fabricating a broadband, high-efficiency acousto-optic modulator operating in shear wave mode, characterized in that, A broadband, high-efficiency acousto-optic modulator applied to the shear wave operating mode as described in any one of claims 1-6 comprises the following steps: S1, a chalcogenide glass film is deposited on a silicon substrate covered with a silicon dioxide layer and a lithium niobate film by thermal evaporation. S2, the fabrication of chalcogenide optical waveguides can be completed by exposure, development and etching on a chalcogenide glass film; S3 involves a second exposure and development process. A metal film is deposited on the chalcogenide glass film after the second exposure and development using vapor deposition or micro-electroplating. After a stripping process, the interdigital transducer and reflector grid can be fabricated.

8. The method for fabricating a broadband, high-efficiency acousto-optic modulator in shear wave mode according to claim 7, characterized in that, Step S2, which involves the fabrication of a chalcogenide optical waveguide on a chalcogenide glass thin film through exposure, development, and etching, specifically includes: S201. Using an electron beam direct writing system, positive electron paste is exposed onto a deposited chalcogenide glass film with a thickness of 400 nm. After baking on a hot plate at 130°C for 5 min, and then developing with xylene, a mask pattern corresponding to the shape of the chalcogenide optical waveguide can be obtained on the electron paste. S202. Using reactive ion etching equipment, the mask pattern obtained on the electronic adhesive is used as a mask, and dry etching is performed with CHF3 gas and argon gas. The sidewall morphology is required to be smooth and steep. The etching power is set to 60W, the etching gas pressure is 60mTorr, and the etching gas flow rate is 25 and 30sccm. S203. Place the etched silicon substrate into the chamber and use oxygen plasma etching gas to remove the residual electron adhesive on top. The gas flow rate is 50 sccm, the RF power is 20W, and the inductively coupled plasma (ICP) power is 1000W. After the process is completed, the mask pattern can be transferred and the chalcogenide optical waveguide can be fabricated.

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