CN114859579A - Novel push-pull type efficient broadband acousto-optic modulator and preparation method thereof - Google Patents
Novel push-pull type efficient broadband acousto-optic modulator and preparation method thereof Download PDFInfo
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- 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
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
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- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/13—Integrated optical circuits characterised by the manufacturing method
- G02B6/136—Integrated optical circuits characterised by the manufacturing method by etching
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- G—PHYSICS
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- 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
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- G02F1/0072—Mechanical, acoustic, electro-elastic, magneto-elastic properties
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- G—PHYSICS
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- 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
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- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/26—Processing photosensitive materials; Apparatus therefor
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12166—Manufacturing methods
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- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
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Abstract
The invention discloses a novel push-pull type efficient broadband acousto-optic modulator and a preparation method thereof, wherein the acousto-optic modulator comprises a substrate, a lithium niobate-chalcogenide glass heterogeneous layer arranged on the substrate and an interdigital transducer on a lithium niobate film; the lithium niobate-chalcogenide glass heterogeneous layer comprises a lithium niobate thin film and a chalcogenide optical waveguide heterointegrated on the lithium niobate thin film; the interdigital transducer arranged on the lithium niobate film comprises a plurality of interdigital electrodes, and the interdigital transducer adopts a focusing interdigital transducer or a double-electrode interdigital transducer with different lengths. The focusing interdigital transducer is used for exciting the convergent surface acoustic wave, so that the acoustic wave energy is fully utilized, and the variation of the refractive index of the optical waveguide is improved; or double-electrode interdigital transducers with different lengths are used, so that the problem of electrode reflection is effectively solved, and the working bandwidth of microwaves is improved; the acousto-optic modulator has the characteristics of high modulation efficiency, easiness in manufacturing, large bandwidth, high speed and easiness in realizing on-chip large-scale integration.
Description
Technical Field
The invention relates to the technical field of photoelectron, in particular to a novel push-pull type efficient broadband acousto-optic modulator and a preparation method thereof.
Background
The acousto-optic control device is a multi-physical field coupling element utilizing the interaction of sound waves and light waves, and is an indispensable bridge in the interconversion of the sound waves and the light waves. Various acousto-optic devices of different types, such as an acousto-optic modulator, an acousto-optic frequency shifter, an acousto-optic deflector, an acousto-optic filter, an acousto-optic Q switch and the like, are developed on the market at present, and are used for realizing effective control of the intensity, direction and frequency of light wave transmission. The acousto-optic functional devices are physical devices which are based on Bragg grating diffraction effect and Doppler effect, and combine an electroacoustic transducer and a piezoelectric crystal material to carry out multi-dimensional regulation and control on relevant parameters of incident light wave signals. The acousto-optic modulator is a common acousto-optic regulation and control device which is most widely applied, the acousto-optic modulator is currently divided into bulk wave drive and surface wave drive, and the surface acoustic wave modulator has wide application and development prospects in the fields of optical communication, laser processing technology, laser ranging technology, optical radar technology, laser medical technology and the like due to the advantages of small driving power, small size, high modulation efficiency, easiness in integration and the like. However, the development of the acousto-optic modulator faces the challenges of modulation efficiency, modulation bandwidth and modulation rate, so how to enhance the interaction strength of the acoustic wave and the optical wave in a small scale range and simultaneously improve the modulation rate, efficiency and bandwidth is a must trend for future development.
In recent years, researchers have been based on different device structures, such as: the modulation effect of the surface acoustic wave on the waveguide is experimentally researched by a suspension structure, a one-dimensional photonic crystal nano beam, a two-dimensional photonic crystal resonator, an opto-mechanical resonant cavity and the like. However, the defects of too large device size, too low modulation efficiency, narrow bandwidth, complex process and the like exist, so that the realization of the acousto-optic modulation of the high-speed high-efficiency broadband still has a lot of difficulties, and therefore, the research on the on-chip acousto-optic modulator of the high-speed high-efficiency broadband has a remarkable practical significance.
Disclosure of Invention
The invention aims to provide a novel push-pull type efficient broadband acousto-optic modulator and a preparation method thereof, which combine the acousto-optic characteristics of chalcogenide glass materials and the piezoelectric effect of a lithium niobate film, utilize an interdigital transducer to excite a convergent surface acoustic wave, fully utilize acoustic wave energy, improve the working bandwidth of light waves, further realize the push-pull type efficient broadband acousto-optic modulation, and have the characteristics of high modulation efficiency, easiness in manufacturing, large bandwidth and easiness in realizing large-scale on-chip integration.
In order to achieve the purpose, the invention provides the following scheme:
a novel push-pull type high-efficiency broadband acousto-optic modulator comprises: the lithium niobate-chalcogenide glass heterogeneous layer is in a non-suspension state relative to the substrate; the lithium niobate-chalcogenide glass heterogeneous layer comprises a lithium niobate film and a chalcogenide optical waveguide which is heterogeneously integrated on the lithium niobate film, the interdigital transducer is arranged on the lithium niobate film, the interdigital transducer adopts a focusing type interdigital transducer or a double-electrode interdigital transducer with different lengths, and the interdigital transducer comprises a plurality of interdigital electrodes.
Furthermore, the chalcogenide optical waveguide is an MZI type optical waveguide, an RT runway type optical waveguide, a one-dimensional photonic crystal nano beam, a two-dimensional photonic crystal resonator or an optical mechanical resonant cavity waveguide structure.
Furthermore, the upper arm of the MZI optical waveguide is composed of four 90-degree small bending radius waveguides and straight waveguides.
Further, the interdigital transducer has odd interdigital index for the MZI type optical waveguide under specific frequency; for the RT runway type optical waveguide, the interdigital transducers have even number of interdigital indexes, are arranged between two arms of the optical waveguide, and have the same distance from the center to the two arms of the optical waveguide.
Further, the thickness of the lithium niobate thin film is 100 nm-1500 nm; the interdigital transducer can realize the excitation of Rayleigh acoustic surface waves of 100 MHz-10 GHz; the width of the chalcogenide optical waveguide is 300 nm-30 mu m, the height of the chalcogenide optical waveguide is 350 nm-2500 nm, and the working wavelength of the chalcogenide optical waveguide is 800nm-10000 nm.
The invention also provides a preparation method of the novel push-pull type efficient broadband acousto-optic modulator, which is applied to the novel push-pull type efficient broadband acousto-optic modulator and comprises the following steps:
s1, depositing a chalcogenide glass film on the substrate covered with the lithium niobate film by a thermal evaporation method;
s2, the optical waveguide can be manufactured after the substrate is exposed, developed and etched;
and S3, plating a layer of metal film on the substrate after exposure and development by using an evaporation plating or micro-plating method after secondary exposure and development, and then completing the manufacture of the interdigital transducer by a stripping process.
Further, in step S2, the manufacturing of the optical waveguide can be completed after the substrate is exposed, developed and etched, and the manufacturing method specifically includes:
s201, exposing the positive electronic adhesive APR6200 on a prepared ChG thin film by using an electron beam direct writing system; the thickness is about 400nm, then baking is carried out for 5min on a hot plate at the temperature of 130 ℃, and after developing by utilizing xylene, a mask pattern in the shape of MZI can be obtained on the electronic glue;
s202, using a reactive ion etching device, using a pattern obtained on the electronic glue as a mask and using CHF 3 Carrying out dry etching on gas and argon, wherein the appearance of the side wall is required to be smooth and steep, the etching power is set to be 60W, the etching pressure is set to be 60mTorr, and the flow rate of the etching gas is set to be 25 sccm and 30 sccm;
s203, placing the etched substrate into a cavity, and removing residual electronic glue on the top by using oxygen plasma etching gas, wherein the gas flow rate is 50sccm, the radio frequency power is 20W, the inductively coupled plasma ICP power is 1000W, and after the process is finished, the MZI pattern on the substrate can be transferred and processed, so that the optical waveguide is manufactured.
Further, in step S3, after the second exposure and development, a metal film is plated on the substrate after the exposure and development by using an evaporation or micro-plating method, and then the manufacturing of the focus type interdigital transducer is completed through a stripping process, which specifically includes:
s301, exposing the positive electronic adhesive APR6200 on the etched substrate by using an electron beam direct writing system; the thickness is about 500nm, then baking is carried out for 5min on a hot plate at the temperature of 130 ℃, and a mask pattern of the focusing interdigital transducer can be obtained on the electronic glue after developing by utilizing xylene;
s302, depositing gold with the thickness of 100nm on the substrate after development and exposure by using a thermal evaporation method;
and S303, soaking the deposited substrate in an organic solution to remove the electronic glue on the surface of the substrate and the metal film on the electronic glue, thus finishing the manufacture of the interdigital transducer.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects: the invention provides a novel push-pull type efficient broadband acousto-optic modulator and a preparation method thereof, firstly, based on a mixed heterogeneous integrated waveguide structure of lithium niobate-chalcogenide glass, the excellent piezoelectric effect of the lithium niobate and the remarkable elasto-optic effect of the chalcogenide glass are fully exerted, and the refractive index change generated by an optical waveguide is obviously improved; secondly, the focusing interdigital transducer structure fully utilizes the acoustic energy of the part of the traditional interdigital transducer which does not participate in modulation, thereby further improving the modulation efficiency; thirdly, the double-electrode interdigital transducers with different lengths can effectively eliminate the electrode reflection problem and improve the microwave working bandwidth. The optical waveguides are arranged at two sides of the focusing interdigital transducer, so that the problem of acoustic energy loss caused by the fact that acoustic waves pass through the first optical waveguide in the traditional acoustic optical modulator is solved, and the waveguides at two sides of the interdigital transducer are respectively arranged at the wave crest and the wave trough of the acoustic waves, so that the defect that the traditional acoustic optical modulator is difficult to carry out a precise push-pull mode is overcome; and finally, the problem that the working bandwidth of the traditional acousto-optic modulator is too narrow is solved. Compared with the prior art, the proposal provides an idea for developing a push-pull type high-efficiency broadband acousto-optic modulator.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a schematic diagram of a top view of a push-pull high efficiency broadband acousto-optic modulator according to an embodiment of the present invention;
FIG. 2 is a flow chart of a method for manufacturing a novel push-pull type high-efficiency broadband acousto-optic modulator according to an embodiment of the present invention;
FIG. 3 is a schematic top view of a push-pull high-efficiency broadband acousto-optic modulator according to a second embodiment of the present invention;
FIG. 4 is a flow chart of a method for manufacturing a push-pull type high-efficiency broadband acousto-optic modulator according to a second embodiment of the present invention;
FIG. 5 is a schematic diagram of a testing system of the novel push-pull type high-efficiency broadband acousto-optic modulator according to the embodiment of the invention.
Description of reference numerals: 1. si (silicon); 2. SiO 2 2 (silica); 3. LiNbO 3 (lithium niobate); 4. ChG (chalcogenide glass); 5. au (gold); 6. resist (Resist coating, either electronic or photoresist).
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a novel push-pull type efficient broadband acousto-optic modulator, which comprehensively utilizes the excellent acousto-optic characteristics of a chalcogenide glass material and the outstanding piezoelectric effect of a lithium niobate film, four waveguides with 90-degree small bending radius are arranged on one arm to flexibly adjust the distance between the waveguides and an interdigital transducer, the full utilization of acoustic energy and the remarkable expansion of the working bandwidth of an optical wave are realized by respectively utilizing a focusing type interdigital transducer and a double-electrode interdigital transducer with different lengths, and the interdigital transducer is arranged between the two arms to achieve push-pull mode modulation. The defect that the traditional acousto-optic modulator is insufficient in utilization rate of acoustic wave energy is overcome, the defect that the bandwidth is insufficient is overcome, and the defect that a push-pull mode is difficult to realize is overcome.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
The invention provides a novel push-pull type efficient broadband acousto-optic modulator, which comprises: the lithium niobate-chalcogenide glass heterogeneous layer is in a non-suspension state relative to the substrate; the lithium niobate-chalcogenide glass heterogeneous layer comprises a lithium niobate film and a chalcogenide optical waveguide which is heterogeneously integrated on the lithium niobate film, the interdigital transducer is arranged on the lithium niobate film, the interdigital transducer adopts a focusing type interdigital transducer or a double-electrode interdigital transducer with different lengths, and the interdigital transducer comprises a plurality of interdigital electrodes.
As shown in fig. 2 and 4, the substrate comprises silicon 1 and silicon dioxide 2, lithium niobate 3 is arranged on the silicon dioxide, and gold 5 is adopted as the interdigital electrode; chalcogenide glass 4 is used as the chalcogenide optical waveguide.
The chalcogenide optical waveguide is of a MZI type optical waveguide, an RT runway type optical waveguide, a one-dimensional photonic crystal nano beam, a two-dimensional photonic crystal resonator or an opto-mechanical resonant cavity and other waveguide structures. The upper arm of the chalcogenide MZI type optical waveguide is composed of four 90-degree small bending radius waveguides and straight waveguides. The lithium niobate-chalcogenide glass heterostructure layer is in an unsuspended state relative to the substrate. The interdigital transducer is arranged between the two arms of the optical waveguide, and the distance from the center of the interdigital transducer to the two arms of the optical waveguide is the same. The thickness of the lithium niobate film is 100 nm-1500 nm; the width of the chalcogenide optical waveguide is 300 nm-30 mu m, the height of the chalcogenide optical waveguide is 150 nm-2500 nm, the working wavelength of the chalcogenide optical waveguide is 800nm-10000nm, and the interdigital transducer can realize the excitation of Rayleigh surface acoustic waves of 100 MHz-10 GHz; the length-unequal double-electrode interdigital transducers realize the working bandwidth of 20 MHz-500 MHz.
The microwave is input to the process of generating surface acoustic waves, based on the reverse piezoelectric coupling effect of the lithium niobate thin film, an input microwave signal is converted into a lithium niobate thin film surface acoustic wave signal through an interdigital transducer, so that the lithium niobate thin film has mechanical strain field distribution, the mechanical acoustic waves generated on the surface of the lithium niobate thin film further act on an optical waveguide, the process is based on the optomechanical coupling effect (moving boundary effect, elasto-optical effect and electro-optical effect), so that the optical refractive index of the optical waveguide is changed, and further, the change of the refractive index can be converted into the change of the phase through waveguide structures such as MZI type waveguides, RT runway type waveguides, one-dimensional photonic crystal nano beams, two-dimensional photonic crystal resonators or optomechanical resonant cavities. The focusing interdigital transducer can use most energy of the generated surface wave for modulation, and the double-electrode interdigital transducers with different lengths can effectively eliminate the electrode reflection problem and improve the working bandwidth of the light wave. Meanwhile, the optical waveguide is positioned on two sides of the focusing interdigital transducer and works in a push-pull mode, so that the strength of acousto-optic action is enhanced to a great extent, and the novel acousto-optic modulator which is high in bandwidth, high in efficiency and push-pull is facilitated to be realized.
The invention also provides a preparation method of the novel push-pull type efficient broadband acousto-optic modulator, which is applied to the novel push-pull type efficient broadband acousto-optic modulator and comprises the following steps:
s1, depositing a chalcogenide glass film on the substrate covered with the lithium niobate film by a thermal evaporation method;
s2, the optical waveguide can be manufactured after the substrate is exposed, developed and etched;
and S3, plating a layer of metal film on the substrate after exposure and development by using an evaporation plating or micro-plating method after secondary exposure and development, and then completing the manufacture of the interdigital transducer by a stripping process.
As shown in fig. 1, the novel push-pull efficient broadband acousto-optic modulator provided by the embodiment of the invention adopts a focusing interdigital transducer, mainly comprising an odd number of interdigital focusing interdigital electrodes on a lithium niobate thin film and a hetero-integrated chalcogenide MZI-type optical waveguide on the thin film, wherein the waveguide works in a communication band near 1550nm, and the interdigital transducer excites a 1GHz surface acoustic wave. The focusing interdigital transducers with odd number of interdigital are selected to excite convergent surface acoustic waves to better utilize the energy of the surface acoustic waves on one hand, and to enable two arms to be respectively positioned at wave crests and wave troughs on the other hand, so that the regulation and control under a push-pull mode are realized.
As shown in fig. 2, the preparation method of the focusing push-pull type high-efficiency acousto-optic modulator based on the MZI type optical waveguide comprises the following specific steps:
s1, depositing Ge with thickness of 850nm on the substrate covered with the lithium niobate thin film by adopting a thermal evaporation method 25 Sb 10 S 65 A chalcogenide glass film;
s2, exposing the positive electronic glue (APR6200) on the prepared ChG thin film using an electron beam direct writing system (EBL, Vistec EBPG 5000 +); the thickness is about 400nm, then baking is carried out for 5min on a hot plate at the temperature of 130 ℃, and a mask pattern in the shape of MZI can be obtained on the electronic glue after developing by utilizing xylene;
s3, using reactive ion etching equipment and using the pattern obtained on the electronic glue as a mask by means of CHF 3 Carrying out dry etching on gas and argon, wherein the appearance of the side wall is required to be smooth and steep; setting the etching power to be 60W, the etching pressure to be 60mTorr and the etching gas flow rate to be 25 sccm and 30 sccm;
s4, placing the etched substrate into a chamber, and removing residual electronic glue on the top by using oxygen plasma etching gas, wherein the gas flow rate is 50sccm, the radio frequency power is 20W, the inductively coupled plasma ICP power is 1000W, and the MZI pattern transfer processing on the substrate can be completed after the process is finished;
s5, exposing the positive electronic glue (APR6200) on the etched substrate by using an electron beam direct writing system (EBL, Vistec EBPG 5000 +); the thickness is about 500nm, then baking is carried out for 5min on a hot plate at the temperature of 130 ℃, and a mask pattern of the focusing interdigital transducer can be obtained on the electronic glue after developing by utilizing xylene;
s6, depositing gold with the thickness of about 100nm on the substrate after development and exposure by a thermal evaporation method;
and S7, soaking the deposited substrate in an organic solution (such as acetone) to remove the electronic glue on the surface of the substrate and the metal film on the electronic glue, thus completing the manufacture of the focusing interdigital transducer.
Fig. 5 is a schematic diagram of a test system according to the present invention, which mainly includes: tunable laser, erbium-doped fiber amplifier, photoelectric detector, vector network analyzer, and spectrometer.
When the device is tested, a microwave signal with a certain frequency is loaded on the focusing interdigital transducer, at the moment, the converging surface acoustic waves which are transmitted to two sides can be excited under the action of the inverse piezoelectric effect of the lithium niobate film, and the sound waves act on the optical waveguide to complete the conversion of the microwaves and the optical waves. Under the action of the sound wave, the equivalent refractive index of the optical waveguide is changed, so that the phase of the optical signal is further changed, and finally, the intensity modulation is realized. The output optical signal is converted into an electric signal through a photoelectric detector, and the S of the modulated signal can be obtained after the electric signal passes through a network analyzer 21 Transmission spectrum by pair S 21 The analysis of the transmission spectrum can calculate the voltage required to be loaded for changing the pi phase, and further multiply the calculated voltage with the length of the modulation region to obtain a half-wave voltage length product, so that the conversion efficiency and the modulation performance of the acousto-optic modulator are evaluated.
Example II
As shown in fig. 3, the novel push-pull type high-efficiency broadband acousto-optic modulator provided by the embodiment of the invention adopts a dual-electrode interdigital transducer, mainly comprising odd-numbered interdigital dual-electrode interdigital transducers with different lengths on a lithium niobate thin film and a sulfur series MZI type optical waveguide heterologously integrated on the thin film, and the waveguide works in a communication waveband near 1550 nm.
The interdigital transducer generates 1GHz surface acoustic waves, and meanwhile, the working bandwidth of the interdigital transducer can reach 20 MHz-500 MHz. Odd interdigital double-electrode interdigital transducers with different lengths are selected, on one hand, the reflection of the electrodes is effectively eliminated, and the working bandwidth of microwaves is improved; on the other hand, in order to enable the two-arm waveguide to be respectively positioned at the wave crest and the wave trough, the efficient regulation and control under the push-pull mode is realized.
As shown in fig. 4, the preparation method of the dual-electrode push-pull type high-efficiency broadband acousto-optic modulator based on the MZI type optical waveguide comprises the following specific steps:
s1, depositing Ge with thickness of 850nm on the substrate covered with the lithium niobate thin film by adopting a thermal evaporation method 25 Sb 10 S 65 A chalcogenide glass film;
s2, exposing the positive electronic glue (APR6200) on the prepared ChG thin film using an electron beam direct writing system (EBL, Vistec EBPG 5000 +); the thickness is about 400nm, then baking is carried out for 5min on a hot plate at the temperature of 130 ℃, and a mask pattern in the shape of MZI can be obtained on the electronic glue after developing by utilizing xylene;
s3, using reactive ion etching equipment, using the pattern obtained on the electronic glue as a mask, and using CHF 3 Carrying out dry etching on gas and argon, wherein the appearance of the side wall is required to be smooth and steep; setting the etching power to be 60W, the gas pressure to be 60mTorr, the etching gas pressure to be 60mTorr and the etching gas flow rate to be 25 sccm and 30 sccm;
s4, placing the etched substrate into a chamber, and removing residual electronic glue on the top by using oxygen plasma etching gas, wherein the gas flow rate is 50sccm, the radio frequency power is 20W, the inductively coupled plasma ICP power is 1000W, and the MZI pattern transfer processing on the substrate can be completed after the process is finished;
s5, exposing the positive electronic glue (APR6200) on the etched substrate by using an electron beam direct writing system (EBL, Vistec EBPG 5000 +); the thickness is about 500nm, then baking is carried out for 5min on a hot plate at the temperature of 130 ℃, and a mask pattern of the focusing interdigital transducer can be obtained on the electronic glue after developing by utilizing xylene;
s6, depositing gold with the thickness of about 100nm on the substrate after development and exposure by a thermal evaporation method;
and S7, soaking the deposited substrate in an organic solution (such as acetone) to remove the electronic glue on the surface of the substrate and the metal film on the electronic glue, thus completing the manufacture of the double-electrode interdigital transducer.
The testing system and the testing steps corresponding to the second embodiment are the same as those of the first embodiment.
In conclusion, the novel push-pull type efficient broadband acousto-optic modulator and the preparation method thereof provided by the invention have the advantages that firstly, based on the mixed heterogeneous integrated waveguide structure of lithium niobate-chalcogenide glass, the excellent piezoelectric effect of lithium niobate and the remarkable elasto-optic effect of chalcogenide glass are fully exerted, and the refractive index change generated by the optical waveguide is obviously improved; secondly, the structure of the focusing interdigital transducer fully utilizes the acoustic energy of the traditional interdigital transducer which does not participate in modulation; thirdly, the double-electrode interdigital transducers with different lengths can effectively eliminate the electrode reflection problem and improve the microwave working bandwidth, and the optical waveguides are positioned at two sides of the focusing interdigital transducer, so that the problem of sound wave energy loss caused by the fact that sound waves pass through the first optical waveguide in the traditional acoustic-optical modulator is solved, and the waveguides at two sides of the interdigital transducer are respectively positioned at the wave crest and the wave trough of the sound waves, so that the defect that the traditional acoustic-optical modulator is difficult to carry out a precise push-pull mode is overcome; and finally, the problem that the working bandwidth of the traditional acousto-optic modulator is too narrow is solved. Compared with the prior art, the proposal provides an idea for developing a push-pull type high-efficiency broadband acousto-optic modulator.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In summary, this summary should not be construed to limit the present invention.
Claims (8)
1. A novel push-pull type efficient broadband acousto-optic modulator is characterized by comprising: the lithium niobate-chalcogenide glass heterogeneous layer is in a non-suspension state relative to the substrate; the lithium niobate-chalcogenide glass heterogeneous layer comprises a lithium niobate film and a chalcogenide optical waveguide which is heterogeneously integrated on the lithium niobate film, the interdigital transducer is arranged on the lithium niobate film, the interdigital transducer adopts a focusing type interdigital transducer or a double-electrode interdigital transducer with different lengths, and the interdigital transducer comprises a plurality of interdigital electrodes.
2. The novel push-pull efficient broadband acousto-optic modulator according to claim 1, wherein the chalcogenide optical waveguide is an MZI type optical waveguide, an RT racetrack type optical waveguide, a one-dimensional photonic crystal nano-beam, a two-dimensional photonic crystal resonator or an opto-mechanical resonator waveguide structure.
3. The novel push-pull efficient broadband acousto-optic modulator according to claim 2, wherein the MZI type optical waveguide upper arm is composed of four 90-degree small bend radius waveguides and a straight waveguide.
4. The novel push-pull high-efficiency broadband acousto-optic modulator according to claim 2, characterized in that the interdigital transducer has an odd number of interdigital transducers for MZI type optical waveguides at a specific frequency; for the RT runway type optical waveguide, the interdigital transducers have even number of interdigital indexes, are arranged between two arms of the optical waveguide, and have the same distance from the center to the two arms of the optical waveguide.
5. The novel push-pull type efficient broadband acousto-optic modulator according to claim 1, wherein the thickness of the lithium niobate thin film is 100nm to 1500 nm; the interdigital transducer can realize the excitation of Rayleigh acoustic surface waves of 100 MHz-10 GHz; the width of the chalcogenide optical waveguide is 300 nm-30 mu m, the height of the chalcogenide optical waveguide is 350 nm-2500 nm, and the working wavelength of the chalcogenide optical waveguide is 800nm-10000 nm.
6. A preparation method of a novel push-pull type efficient broadband acousto-optic modulator is characterized by being applied to the novel push-pull type efficient broadband acousto-optic modulator according to any one of claims 1 to 5, and comprising the following steps:
s1, depositing a chalcogenide glass film on the substrate covered with the lithium niobate film by a thermal evaporation method;
s2, the optical waveguide can be manufactured after the substrate is exposed, developed and etched;
and S3, plating a layer of metal film on the substrate after exposure and development by using an evaporation plating or micro-plating method after secondary exposure and development, and then completing the manufacture of the interdigital transducer by a stripping process.
7. The method for manufacturing a push-pull efficient broadband acousto-optic modulator according to claim 6, wherein in step S2, the substrate is exposed, developed and etched to complete the manufacture of the optical waveguide, specifically comprising:
s201, exposing the positive electronic adhesive APR6200 on a prepared ChG thin film by using an electron beam direct writing system; the thickness is about 400nm, then baking is carried out for 5min on a hot plate at the temperature of 130 ℃, and after developing by utilizing xylene, a mask pattern in the shape of MZI can be obtained on the electronic glue;
s202, using a reactive ion etching device, using a pattern obtained on the electronic glue as a mask and using CHF 3 Carrying out dry etching on the gas and argon, wherein the appearance of the side wall is required to be smooth and steep, the etching power is set to be 60W, the etching pressure is set to be 60mTorr, and the flow rate of the etching gas is set to be 25 sccm and 30 sccm;
s203, placing the etched substrate into a cavity, and removing residual electronic glue on the top by using oxygen plasma etching gas, wherein the gas flow rate is 50sccm, the radio frequency power is 20W, the inductively coupled plasma ICP power is 1000W, and after the process is finished, the MZI pattern on the substrate can be transferred and processed, so that the optical waveguide is manufactured.
8. The method for manufacturing a novel push-pull type efficient broadband acousto-optic modulator according to claim 6, wherein the step S3 is to plate a metal film on the substrate after exposure and development by using an evaporation or micro-plating method after secondary exposure and development and then complete the manufacturing of the focusing interdigital transducer by a stripping process, and specifically comprises the steps of:
s301, exposing the positive electronic adhesive APR6200 on the etched substrate by using an electron beam direct writing system; the thickness is about 500nm, then baking is carried out for 5min on a hot plate at the temperature of 130 ℃, and a mask pattern of the focusing interdigital transducer can be obtained on the electronic glue after developing by utilizing xylene;
s302, depositing gold with the thickness of 100nm on the substrate after development and exposure by using a thermal evaporation method;
and S303, soaking the deposited substrate in an organic solution to remove the electronic glue on the surface of the substrate and the metal film on the electronic glue, thus finishing the manufacture of the interdigital transducer.
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