CN116736600A - Micro-ring type acousto-optic modulator and preparation method thereof - Google Patents
Micro-ring type acousto-optic modulator and preparation method thereof Download PDFInfo
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/365—Non-linear optics in an optical waveguide structure
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/11—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on acousto-optical elements, e.g. using variable diffraction by sound or like mechanical waves
- G02F1/125—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on acousto-optical elements, e.g. using variable diffraction by sound or like mechanical waves in an optical waveguide structure
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/3501—Constructional details or arrangements of non-linear optical devices, e.g. shape of non-linear crystals
- G02F1/3503—Structural association of optical elements, e.g. lenses, with the non-linear optical device
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/3511—Self-focusing or self-trapping of light; Light-induced birefringence; Induced optical Kerr-effect
- G02F1/3513—Soliton propagation
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F2203/00—Function characteristic
- G02F2203/56—Frequency comb synthesizer
Abstract
The application relates to a micro-ring type acousto-optic modulator and a preparation method thereof, wherein the modulator comprises the following components: a substrate, a heterogeneous integrated film, wherein the heterogeneous integrated film comprises a bonded SiC film and an LN piezoelectric film; the heterogeneous integrated film is bonded with a substrate; the acousto-optic modulator is also provided with an optical waveguide structure and an acoustic assembly. The application combines the excellent characteristics of LN and SiC by utilizing two convenient film-on-insulator preparation processes, transfers the high-quality SiC film and the LN film to the insulating substrate, greatly optimizes the integration difficulty of a multilayer film structure, and simultaneously obtains the bending symmetrical interdigital electrode structure of the adaptable optical micro-ring resonant cavity on the SiC/LN/insulating layer structure. The design can be effectively compatible with the traditional processing technology, realizes single and high-efficiency acousto-optic coupling modulation, and is expected to provide a new solving way for realizing multidimensional regulation and control of nonlinear effects such as on-chip optical frequency comb, optical solitons and the like.
Description
Technical Field
The application belongs to the field of information functional materials, and particularly relates to a micro-ring type acousto-optic modulator and a preparation method thereof.
Background
Compared with other optical microcavities, the micro-ring resonant cavity has a low-mode volume capable of remarkably enhancing interaction between light and substances, and has become a way for obtaining a wide-spectrum optical frequency comb and a stable optical soliton, and the device characteristics such as a large free spectral range, cascade connection and the like can be effectively applied to the fields such as nonlinear devices, high-sensitivity sensing, optical communication and the like. As an ideal optical material for realizing the high Q value on-chip micro-ring resonator, siC is used to prepare a thin film on an insulating layer due to its excellent characteristics of wide band gap (2.3-3.2 eV), wide transparent window (0.2-2 um), high refractive index (2.5-2.7), higher second and third order nonlinear coefficients, CMOS process compatibility, etc., which allows the realization of an integrated optical platform with low optical loss, high refractive index contrast, and strong locality. Compared with SiC, LN can also be used for preparing a high-Q microcavity structure, has more unique linear electro-optic effect, photoelastic effect and piezoelectric property, but the high stability of LN waveguide still brings certain difficulty to the micro-nano processing technology of LN waveguide, and most devices can not obtain high-performance acousto-optic modulation by avoiding LN processing.
The continuous innovation of integrated optical technology is urgent to require a multi-dimensional modulation means, and acousto-optic coupling, i.e. the interaction between phonons and photons is utilized to realize the modulation of optical refractive index on a physical level, is an effective linear modulation means. Although acoustic optical coupling based on microcavity structures has been implemented on various LN material platforms, the process limitations of LN and the relatively low third-order nonlinear coefficients limit the application of acoustic modulation in nonlinear fields such as tunable optical frequency comb, soliton regulation and the like, and in addition, the micro-ring resonator is difficult to integrate with the traditional interdigital electrode for generating acoustic surface waves due to the structural specificity of the micro-ring resonator. Therefore, it is necessary to develop new material platforms and device structures to achieve efficient acousto-optic modulation within the micro-ring cavity.
Disclosure of Invention
Aiming at the problems in the prior art, the application aims to provide a micro-ring type acousto-optic modulator and a preparation method thereof.
An acousto-optic modulator of the present application, the modulator comprising: a substrate, a heterogeneous integrated film, wherein the heterogeneous integrated film comprises a bonded SiC film and an LN piezoelectric film; the heterogeneous integrated film is bonded with a substrate; the acousto-optic modulator is also provided with an optical waveguide structure and an acoustic assembly.
The substrate is at least one of a silicon oxide-silicon heterogeneous substrate and a SiC substrate; the optical waveguide structure is arranged in the SiC film; the acoustic assembly is arranged above the heterogeneous integrated film, and further, the acoustic assembly is arranged on the surface of the etched heterogeneous integrated film; the optical waveguide structure includes: a micro-ring waveguide, a linear waveguide; the optical waveguide structure is a micro-nano level optical waveguide structure; the acoustic assembly includes an interdigital structure and an acoustic reflector; the acoustic reflector comprises a metal grid array; the interdigital structure adopts an improved semicircular symmetrical metal electrode shape.
The interdigital structure comprises a first bus, a second bus, a first interdigital structure and a second interdigital structure; the first bus and the second bus are parallel to each other; the second bus is composed of two lines, which are symmetrical along the first bus; the first interdigital structure is connected with the first bus, and a first main bus bar obtained by extending the first bus exists on the first interdigital structure; the second interdigital structure is connected with the second bus, and two second main bus bars symmetrical along the first bus exist on the second interdigital structure; the two second main bus bars are connected with the semicircular connecting lines with the interval distance from the micro-ring type waveguide;
the first interdigital structure is provided with more than two symmetrically distributed arc-shaped finger strips along the first main bus bar; the second interdigital structure is provided with more than two circular arc-shaped finger strips along the two second main bus bars, and the circular arc-shaped finger strips are symmetrical along the first main bus bars; all the circular arc-shaped finger strips are adjacent at equal intervals and concentric with the annular waveguide;
the inter-grating spacing in the metal grid array in the acoustic reflector is 300-3000 nm, the adjacent grating spacing is equal, and specific numerical values can be adjusted according to optimization requirements; the periodic metal grid array, the annular waveguide and the circular arc finger strip are concentric.
The thickness of the interdigital structure internal finger strip is 100-600 nm, the width of the finger strip is 300-2000 nm, the electrode spacing of the finger strip is 300-3000 nm, and the interdigital structure internal finger strip can excite 50 MHz-15 GHz acoustic surface waves, including but not limited to Rayleigh waves and lamb waves;
the annular waveguide comprises at least one of cascaded micro annular waveguide and photonic crystal type micro annular waveguide; the height of the micro-ring type waveguide and the linear type waveguide is 200 nm-700 nm, the width is 300 nm-1500 nm, the working wavelength of light is 700 nm-4000 nm, and the radius of the ring type waveguide is 5 mu m-50 mu m;
the LN piezoelectric film is a Z-cut LN piezoelectric film layer, and the thickness is 400 nm-1000 nm.
The device preparation process comprises the technologies of thermal oxidation, vapor deposition, wafer grinding, chemical mechanical polishing, wafer bonding, film plating, post annealing, electron beam lithography and dry etching, metal stripping process, ion beam evaporation and the like.
The preparation method of the acousto-optic modulator comprises the following steps:
(1) Preparing silicon oxide layers on a SiC wafer <0001> plane and an LN wafer <0001> plane respectively, then activating the silicon oxide layers of the SiC wafer and the LN wafer by using plasma, activating a substrate by using plasma, then respectively bonding the silicon oxide surface of the SiC wafer with the surface of the substrate, bonding the silicon oxide surface of the LN wafer with the surface of the other substrate, and then performing heat treatment;
(2) Thinning the SiC layer and the LN layer by utilizing mechanical grinding and chemical mechanical polishing to obtain target thickness, activating the surfaces of the SiC layer and the LN layer by plasma, bonding the SiC film and the LN film, performing heat treatment, and performing deep silicon etching on the SiC side of the bonding structure until the substrate above the SiC side is completely removed;
(3) And preparing a mask pattern of the optical waveguide structure on the SiC surface, etching the optical waveguide structure, then performing mask patterning of the acoustic assembly on the etched SiC surface by utilizing a double-layer lift-off process, preparing an interdigital electrode and an acoustic reflector, and completing the preparation of the whole device.
The preferred mode of the preparation method is as follows:
the thickness of the silicon oxide dielectric layer prepared on the LN <0001> plane and the SiC <0001> plane in the step (1) is 0-4 mu m, and the preparation method comprises at least one of plasma enhanced chemical vapor deposition, low-pressure chemical vapor deposition and thermal oxidation;
the substrate in the step (1) is at least one of a silicon oxide-silicon heterogeneous substrate and a SiC substrate; when the substrate is a silicon oxide-silicon heterogeneous substrate, a silicon oxide layer of the silicon oxide-silicon heterogeneous substrate is activated by adopting plasma, then the silicon oxide surface of the SiC wafer and the silicon oxide surface of the heterogeneous substrate are respectively subjected to wafer bonding, and the silicon oxide surface of the LN wafer and the silicon oxide surface of another heterogeneous substrate are subjected to wafer bonding.
The energy range of the plasma activation in the steps (1) and (2) is 400 eV-2000 eV, the gas source comprises at least one of oxygen, nitrogen and argon, and the bonding is as follows: the integration between films is carried out in a direct bonding mode under the experimental environment condition of normal temperature and normal pressure; the bonding structure is subjected to thermal annealing on the bonded multi-layer film material, the annealing temperature is higher than the bonding temperature, the thermal annealing is performed, and the temperature is 300-1200 ℃; the annealing time is 1 h-48 h, and the annealing time and the annealing temperature are in a negative correlation.
The thinning in the step (2) specifically comprises the following steps: firstly, mechanically grinding the SiC layer and the LN layer to 5-10 mu m; and polishing and grinding to 200-1000 nm by using chemical machinery, ensuring that the bonding surface roughness of the SiC film and the LN film is less than 0.5nm, and finally obtaining the target thickness within the range of the grinding thickness.
Patterning the optical waveguide structure on a mask by using an electron beam exposure method, and preparing the optical waveguide structure on the SiC film by using dry etching; patterning the acoustic assembly by using PDMS as a mask and a double-layer lift-off process; depositing a metal electrode by using an electron beam evaporation method, wherein the thickness of the electrode is 100 nm-300 nm; removing the unexposed mask by removing the photoresist, wherein the photoresist removing types comprise, but are not limited to, concentrated sulfuric acid, acetone and alcohol; carrying out heat treatment on the metal electrode by adopting an annealing process, wherein the annealing time is 1-5 min, and the annealing temperature is 150-400 ℃; the metal electrode comprises at least one of aluminum, copper, titanium, nickel, chromium, i.e., the electron beam evaporation method is used to deposit the metal electrode comprising but not limited to aluminum, copper, titanium, nickel, chromium.
The application relates to an application of an acousto-optic modulator in an integrated optical chip, wherein the integrated optical chip comprises but is not limited to an integrated acousto-optic modulation chip, an acoustic tunable optical frequency comb, an acousto-optic filter and a high-speed on-chip sensor.
The acousto-optic modulator can be applied to the integrated optical chip by utilizing the field coupling of the acoustic surface wave and the light wave, and can be used for adjusting and controlling the optical frequency comb, stabilizing the optical soliton, high-speed filtering, sensing and the like by utilizing the acousto-physical field.
The application designs a novel micro-ring type acousto-optic modulator and a preparation method thereof. The acousto-optic modulator comprises a substrate, a heterogeneous integrated film and an acoustic assembly; the heterogeneous integrated film comprises a tightly-bonded SiC film and an LN film, and an optical waveguide structure and an acoustic assembly are respectively arranged on the heterogeneous integrated film; the optical waveguide structure comprises a micro-ring waveguide and a linear waveguide, which are arranged in the SiC layer; the acoustic assembly comprises a novel interdigital structure and an acoustic reflector, wherein the acoustic reflector is in a semicircular shape and is concentric with the micro-ring waveguide; the interdigital structure is arranged on the heterogeneous integrated film, and can stably excite the surface acoustic wave coupled with the field intensity of the micro-ring cavity. The preparation process comprises the following steps: generating hydrophilic silicon oxide layers on SiC and LN wafers; respectively integrating the two oxidized wafers with a silicon oxide/silicon heterogeneous substrate; grinding to obtain a SiC film and an LN film with submicron thickness; directly bonding the SiC film on the chip and the LN film on the chip, and realizing a SiC/LN/insulating layer structure by deep silicon etching; and preparing a device structure on the SiC layer by using ion beam exposure, dry etching and ion beam evaporation, and then carrying out low-temperature annealing heat treatment to obtain the complete micro-ring type acousto-optic modulation device.
The application combines the excellent characteristics of LN and SiC by utilizing two convenient film-on-insulator preparation processes, transfers the high-quality SiC film and the LN film to the insulating substrate, greatly optimizes the integration difficulty of a multilayer film structure, and simultaneously obtains the bending symmetrical interdigital electrode structure of the adaptable optical micro-ring resonant cavity on the SiC/LN/insulating layer structure. The design can be effectively compatible with the traditional processing technology, realizes single and high-efficiency acousto-optic coupling modulation, and is expected to provide a new solving way for realizing multidimensional regulation and control of nonlinear effects such as on-chip optical frequency comb, optical solitons and the like.
Advantageous effects
The application provides an acousto-optic modulator based on a heterogeneous SiC/LN integrated optical platform by combining the acousto-optic characteristics of LN and the strong nonlinear effect of SiC. The design combines SiC, LN film materials and a substrate through a more convenient insulator-on-integration process under the fusion of two types of materials, greatly optimizes the difficulty of the wafer-level on-chip integration process, combines an on-chip micro-ring cavity by utilizing an improved semicircular symmetrical interdigital electrode structure on the premise of not processing an LN layer, can realize high-efficiency and high-field-cavity overlapping acousto-optic coupling modulation, can adapt to the compatibility of the traditional processing process, simultaneously isolates the adverse effect of an electro-optic effect, and further meets the requirement of an on-chip integrated chip on the degree of freedom of optical regulation. The application shows the unique advantages of heterogeneous integrated materials and devices in fusing various modulation methods, and opens up a new way for obtaining a multidimensional-regulation high-speed photonics platform.
Drawings
FIG. 1 is a process schematic of a method of making an acousto-optic modulator of the present application;
fig. 2 is a schematic structural diagram of an acousto-optic modulator of the present application.
Detailed Description
The application will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application. Furthermore, it should be understood that various changes and modifications can be made by one skilled in the art after reading the teachings of the present application, and such equivalents are intended to fall within the scope of the application as defined in the appended claims.
Example 1
An acousto-optic modulator, the modulator comprising: a substrate, a heterogeneous integrated film, wherein the heterogeneous integrated film comprises a bonded SiC film and an LN piezoelectric film; the heterogeneous integrated film is bonded with a substrate; the acousto-optic modulator is also provided with an optical waveguide structure and an acoustic assembly. The substrate can be at least one selected from a silicon oxide-silicon heterogeneous substrate and a SiC substrate; further this embodiment selects a silicon oxide-silicon hetero-substrate.
The optical waveguide structure is arranged in the SiC film; the acoustic assembly is arranged above the heterogeneous integrated film (the acoustic assembly is arranged on the surface of the etched heterogeneous integrated film); the optical waveguide structure includes: a ring waveguide, a linear waveguide; the optical waveguide structure is a micro-nano level optical waveguide structure; the acoustic assembly includes an interdigital structure and an acoustic reflector; the acoustic reflector comprises a metal grid array.
The interdigital structure comprises a first bus, a second bus, a first interdigital structure and a second interdigital structure; the first bus and the second bus are parallel to each other; the second bus is composed of two lines, and the second bus is symmetrical to the first bus; the first interdigital structure is connected with the first bus, and a first main bus bar obtained by extending the first bus exists on the first interdigital structure; the second interdigital structure is connected with the second bus, and two second main bus bars symmetrical along the first bus exist on the second interdigital structure; the two second main bus bars are connected with the semicircular connecting lines with the interval distance from the annular waveguide;
the first interdigital structure is provided with more than two symmetrically distributed arc-shaped finger strips along the first main bus bar; the second interdigital structure is provided with more than two circular arc-shaped finger strips along the two second main bus bars, and the circular arc-shaped finger strips are symmetrical along the first main bus bars; all the circular arc-shaped finger strips are adjacent at equal intervals and concentric with the annular waveguide;
inter-grating spacing in the metal grid array in the acoustic reflector is related to inter-grating spacing of the circular arc-shaped finger strips, and adjacent grating spacing is equal; the periodic metal grid array, the annular waveguide and the circular arc finger strip are concentric.
The thickness of the interdigital structure internal finger strip is 100 nm-600 nm, the width of the finger strip is 300 nm-2000 nm, the electrode spacing of the finger strip is 300 nm-3000 nm, and the interdigital structure internal finger strip can excite 50 MHz-15 GHz acoustic surface wave;
the annular waveguide comprises at least one of cascaded micro annular waveguide and photonic crystal type micro annular waveguide; the height of the annular waveguide and the linear waveguide is 200 nm-700 nm, the width is 300 nm-1500 nm, the working wavelength of light is 700 nm-4000 nm, and the radius of the annular waveguide is 5 mu m-50 mu m.
Example 2
(1) A SiC wafer 1 and a LN wafer 2 are provided, and silicon oxide protective layers 3, 4 having a thickness of 400nm are formed on <0001> planes of the SiC and LN wafers, respectively, by a low-pressure chemical vapor deposition method, and a chemical mechanical polishing process is employed.
(2) Preparing two silicon oxide-silicon heterogeneous substrates 5 and 6, treating the silicon oxide sides of the silicon oxide protective layer 3 of the SiC wafer 1, the silicon oxide protective layer 4 of the LN wafer 2 and the silicon oxide-silicon heterogeneous substrates 5 and 6 by utilizing low-energy argon plasma, forming an argon-rich layer with the depth of about 2nm on the surfaces of the silicon oxides, and directly bonding the silicon oxide surfaces of the SiC wafer 1 and the LN wafer 2 with the heterogeneous substrates 5 and 6 in a vacuum environment at normal temperature to form bonding structures 7 and 8; after bonding, a thermal annealing treatment at 800 ℃ was performed for 2 hours.
(3) Adopting a mechanical grinding method to enable the SiC layer and the LN layer after bonding to be 5 mu m, and obtaining ground structures 9 and 10; and thinning the LN grinding structure to 500nm by chemical mechanical polishing, and thinning the SiC grinding structure to 400nm to obtain the SiC film 11 on the insulating sheet and the LN film 12 on the insulating sheet, and ensuring the surface roughness to be below 0.5nm.
(4) The SiC film side of the SiC film 11 on the insulating sheet and the LN film side of the LN film 12 on the insulating sheet are treated with low-energy oxygen plasma, the activation energy of the plasma is 1keV, oxygen-enriched layers with the depth of about 2nm are formed on the surfaces of SiC and LN, and the SiC film and the LN film are directly bonded under the vacuum environment at normal temperature to obtain Si-SiO 2 -SiC-LN-SiO 2 -Si bonding structures 13; after bonding, a thermal annealing treatment at 800 ℃ was performed for 2 hours.
(5) Sheet to be bonded to structureThe upper SiC side is on, the on-chip LN side is under, and deep silicon is adopted to etch the top silicon to obtain SiC-LN-SiO 2 Si heterostructure 14.
(6) The micro-ring modulator is manufactured by adopting PDMS as a mask and assisting electron beam exposure to pattern a micro-ring waveguide structure 15 and a linear waveguide structure 16, defining the width of the waveguide to be 400nm and the radius of the micro-ring to be 10 mu m, and adopting dry etching.
(7) The Al metal interdigital structure 17 and the acoustic reflector 18 are prepared by adopting a double-layer lift-off process and an electron beam evaporation method, so that a complete device structure 19 is obtained, the thickness of an interdigital structure inner finger is 200nm, the width of the finger is 400nm, and the electrode spacing of the finger is 400nm.
(8) And carrying out rapid thermal annealing treatment at 300 ℃ on the device structure 19 for 1 minute to finish the preparation of the micro-ring type acousto-optic modulator.
Based on the embodiment provided in the application, the acousto-optic modulator provided by the application can obtain the following effects: firstly, the micro-ring type acousto-optic modulator based on the heterogeneous integrated film fully combines the optical nonlinear effect of the SiC film and the piezoelectric effect of the LN film, can obtain a stable acoustic mode with high field overlap degree and an intracavity optical mode, and solves the problem of low modulation efficiency caused by poor overlap degree between sound waves and light waves; secondly, the structural symmetry of the device enables the region where the micro-ring waveguide is located to be equipotential, so that crosstalk of electro-optical effect on acousto-optic modulation in the lithium niobate material is isolated; thirdly, the process flow of the micro-ring type acousto-optic modulator avoids the defect of difficult processing of lithium niobate, and improves the process compatibility; fourth, the acousto-optic modulator focuses on the application of optical frequency comb regulation in the micro-ring, and provides a process and device foundation for regulating optical frequency comb and optical soliton by acoustic surface wave.
Claims (10)
1. An acousto-optic modulator, said modulator comprising: a substrate, a heterogeneous integrated film, wherein the heterogeneous integrated film comprises a bonded SiC film and an LN piezoelectric film; the heterogeneous integrated film is bonded with a substrate; the acousto-optic modulator is also provided with an optical waveguide structure and an acoustic assembly.
2. The acousto-optic modulator according to claim 1, wherein said substrate is at least one of a silicon oxide-silicon hetero-substrate, a SiC substrate; the optical waveguide structure is arranged in the SiC film; the acoustic assembly is disposed over the heterogeneous integrated membrane; the optical waveguide structure includes: a ring waveguide, a linear waveguide; the optical waveguide structure is a micro-nano level optical waveguide structure; the acoustic assembly includes an interdigital structure and an acoustic reflector; the acoustic reflector comprises a metal grid array.
3. The acousto-optic modulator according to claim 2, wherein said interdigital structures comprise a first bus, a second bus, a first interdigital structure, and a second interdigital structure; the first bus and the second bus are parallel to each other; the second bus is composed of two lines, and the second bus is symmetrical to the first bus; the first interdigital structure is connected with the first bus, and a first main bus bar obtained by extending the first bus exists on the first interdigital structure; the second interdigital structure is connected with the second bus, and two second main bus bars symmetrical along the first bus exist on the second interdigital structure; the two second main bus bars are connected with the semicircular connecting lines with the interval distance from the annular waveguide;
the first interdigital structure is provided with more than two symmetrically distributed arc-shaped finger strips along the first main bus bar; the second interdigital structure is provided with more than two circular arc-shaped finger strips along the two second main bus bars, and the circular arc-shaped finger strips are symmetrical along the first main bus bars; all the circular arc-shaped finger strips are adjacent at equal intervals and concentric with the annular waveguide.
4. The acousto-optic modulator according to claim 2, wherein inter-grating spacing in the metal grating array in the acoustic reflector is 300 nm-3000 nm, and adjacent grating spacing is equal; the periodic metal grid array, the annular waveguide and the circular arc finger strip are concentric.
5. The acousto-optic modulator according to claim 2, wherein the thickness of the interdigital structure internal finger is 100 nm-600 nm, the width of the finger is 300 nm-2000 nm, the electrode spacing of the finger is 300 nm-3000 nm, and the acoustic surface wave of 50 MHz-15 GHz can be excited;
the annular waveguide comprises at least one of cascaded micro annular waveguide and photonic crystal type micro annular waveguide; the height of the annular waveguide and the linear waveguide is 200 nm-700 nm, the width is 300 nm-1500 nm, the working wavelength of light is 700 nm-4000 nm, and the radius of the annular waveguide is 5 mu m-50 mu m;
the LN piezoelectric film is a Z-cut LN piezoelectric film layer, and the thickness is 400 nm-1000 nm.
6. A method of making an acousto-optic modulator according to claim 1, comprising:
(1) Preparing silicon oxide layers on a SiC wafer <0001> plane and an LN wafer <0001> plane respectively, then activating the silicon oxide layers of the SiC wafer and the LN wafer by using plasma, activating a substrate by using plasma, then respectively bonding the silicon oxide surface of the SiC wafer with the surface of the substrate, bonding the silicon oxide surface of the LN wafer with the surface of the other substrate, and then performing heat treatment;
(2) Thinning the SiC layer and the LN layer, activating the surfaces of the SiC layer and the LN layer by plasma, bonding the SiC film and the LN film, and removing the substrate above the SiC side by heat treatment;
(3) And preparing a mask pattern of the optical waveguide structure on the SiC surface, etching the optical waveguide structure, and then performing mask patterning of the acoustic assembly on the etched SiC surface to prepare an interdigital electrode and an acoustic reflector so as to complete the preparation of the whole device.
7. The method according to claim 6, wherein the thickness of the silicon oxide dielectric layer prepared on the LN <0001> plane and the SiC <0001> plane in the step (1) is 0 to 4. Mu.m, and the method comprises at least one of plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition, and thermal oxidation;
the substrate in the step (1) is at least one of a silicon oxide-silicon heterogeneous substrate and a SiC substrate; when the substrate is a silicon oxide-silicon heterogeneous substrate, activating a silicon oxide layer of the silicon oxide-silicon heterogeneous substrate by adopting plasma, and then respectively bonding the silicon oxide surface of the SiC wafer and the silicon oxide surface of the heterogeneous substrate, and bonding the silicon oxide surface of the LN wafer and the silicon oxide surface of another heterogeneous substrate;
the energy range of the plasma activation in the steps (1) and (2) is 400 eV-2000 eV, the gas source comprises at least one of oxygen, nitrogen and argon, and the bonding is as follows: the integration between films is carried out in a direct bonding mode under the environment condition of normal temperature and normal pressure; the heat treatment is thermal annealing at 300-1200 ℃; the annealing time is 1 h-48 h.
8. The method according to claim 6, wherein the thinning in the step (2) is specifically: firstly, mechanically grinding the SiC layer and the LN layer to 5-10 mu m; chemical mechanical polishing is utilized to grind to 200 nm-1000 nm, and the bonding surface roughness of the SiC film and the LN film is ensured to be less than 0.5nm.
9. The method according to claim 6, wherein the optical waveguide structure is patterned on the mask by electron beam exposure in the step (3), and the optical waveguide structure is prepared on the SiC thin film by dry etching; patterning the acoustic assembly by using PDMS as a mask and a double-layer lift-off process; depositing a metal electrode by using an electron beam evaporation method, wherein the thickness of the electrode is 100 nm-300 nm; removing the unexposed mask by removing the photoresist, wherein the photoresist removing types comprise, but are not limited to, concentrated sulfuric acid, acetone and alcohol; carrying out heat treatment on the metal electrode by adopting an annealing process, wherein the annealing time is 1-5 min, and the annealing temperature is 150-400 ℃; the metal electrode comprises at least one of aluminum, copper, titanium, nickel and chromium.
10. Use of the acousto-optic modulator of claim 1 in an integrated optical chip.
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