CN109799626B

CN109799626B - Low-power-consumption ridge waveguide thermo-optical switch based on buried graphene heating electrode and preparation method thereof

Info

Publication number: CN109799626B
Application number: CN201910084526.5A
Authority: CN
Inventors: 王希斌; 廉天航; 张大明; 王力磊; 牛东海; 王菲; 衣云骥
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2019-01-29
Filing date: 2019-01-29
Publication date: 2021-09-24
Anticipated expiration: 2039-01-29
Also published as: CN109799626A

Abstract

A low-power consumption ridge waveguide thermo-optical switch based on a buried graphene heating electrode and a preparation method thereof belong to the technical field of polymer planar optical waveguide devices and preparation thereof. The whole device is of an MZI optical waveguide structure and comprises, from left to right, an input straight waveguide, a 3-dB Y-branch beam splitter, a device modulation region consisting of two parallel first interference arms and second interference arms, a 3-dB Y-branch coupler and an output straight waveguide; according to the invention, a silicon wafer is used as a substrate, an organic polymer material with a large thermo-optic coefficient is respectively used as an upper cladding layer, a lower cladding layer and a core layer material of an optical waveguide, and the graphene heating electrode is arranged in the core layer of the optical waveguide, so that the heating efficiency of the heating electrode is fully improved, and the advantages of large thermo-optic coefficient and easiness in processing of the organic polymer material are utilized. Meanwhile, the manufacturing process adopted by the invention is simpler, compatible with a semiconductor process, easy to integrate and suitable for large-scale production, thereby having important application prospect.

Description

Low-power-consumption ridge waveguide thermo-optical switch based on buried graphene heating electrode and preparation method thereof

Technical Field

The invention belongs to the technical field of polymer planar optical waveguide devices and preparation thereof, and particularly relates to a low-power consumption ridge waveguide thermo-optical switch and a preparation method thereof, wherein a silicon wafer is used as a substrate, an organic polymer is used as a core layer and a cladding layer of an optical waveguide, and graphene buried in the core layer of the polymer optical waveguide is used as a heating electrode.

Background

With the continuous development of society, the signal processing capacity of information communication networks is also rapidly increased, and further, the demand of equipment on energy is also continuously increased. At present, the energy consumption of the information infrastructure accounts for 4% of the total global energy consumption, the electricity consumption of the information technology equipment is estimated to account for 15% of the total global amount in 2025 with the increase of the data volume, and the high energy consumption is one of the main bottlenecks which restrict the sustainable development of the information technology. Optical switches and optical switch arrays are important components for constructing optical communication networks, and especially on backbone lines of high-speed broadband communication networks adopting Dense Wavelength Division Multiplexing (DWDM), a complex network topology requires reliable and flexible network management. The optical switch and the optical switch array play the functions of optical domain optimization, routing, protection, self-healing and the like in an optical network, are core technologies of an add-drop multiplexer (OADM) and an optical cross connector (OXC), and the performance of the optical switch and the optical switch array affects the performance of the whole optical network.

The thermo-optical switch has received wide attention from people by virtue of the advantages of small device size, low driving power, good long-term stability and the like, and has made great progress in recent years. Currently, thermo-optic switches can be mainly classified into two categories according to different material systems: silicon dioxide/Silicon (SOI) material systems and organic polymer material systems. Since silicon dioxide and silicon materials have larger heat conduction coefficients, a thermo-optical switch of an SOI material system has obvious advantages in response speed, but the power consumption of a device is generally larger, and although the power consumption of the device can be reduced by designing a suspension arm waveguide structure, the processing difficulty and the manufacturing cost of the device can be increased at the same time.

Compared with inorganic materials, organic polymer materials have the advantages of large thermo-optic coefficient, low thermal conductivity and the like, so that thermo-optic switch devices prepared by using the organic polymer materials have the advantages of low power consumption, simple and flexible preparation process and the like, and are more and more attracted by people. In recent years, the performance of the device is improved mainly by optimizing waveguide materials and waveguide structures, and the selected electrodes are mainly metal electrodes (gold, silver, aluminum, copper, chromium and the like), are generally arranged on the surface of an upper cladding of a waveguide and are separated from a waveguide core layer by a certain distance, and are mainly used for reducing the absorption loss of metal to light. However, the heating efficiency of the metal electrode is also limited, and the heat generated by the metal electrode cannot be effectively conducted on the waveguide core layer for transmitting the optical signal, so that the reduction of the power consumption of the device is limited.

Graphene is used as a two-dimensional atomic crystal thin film material emerging in recent years, and has important application prospects in the fields of micro-nano optoelectronic devices, composite materials, energy sources, sensor devices and the like by virtue of excellent electronic, thermal, optical and mechanical properties of graphene. Particularly, due to the light transmission characteristic of graphene, the graphene has important application in the field of transparent conductive films, and experiments show that the single-layer graphene only absorbs 2.3% of light. According to the graphene heating electrode, the graphene is used as the heating electrode and is placed in the core layer of the ridge waveguide by utilizing the excellent electrical conductivity, thermal conductivity and transparency of the graphene material and combining the processing flexibility of the organic polymer material, so that the introduction of the graphene electrode can not cause excessive optical absorption loss by controlling the polarization mode of signal light, the heating efficiency of the electrode can be improved, and the power consumption of a device can be reduced; meanwhile, the preparation method provided by the patent avoids direct processing of the graphene heating electrode, can reduce damage to the graphene film, and ensures the integrity of the graphene heating electrode.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a low-power consumption ridge waveguide thermo-optical switch based on a buried graphene heating electrode and a preparation method thereof.

According to the invention, a silicon wafer is used as a substrate, an organic polymer material with a large thermo-optic coefficient is respectively used as an upper cladding layer, a lower cladding layer and a core layer material of an optical waveguide, and the graphene heating electrode is arranged in the core layer of the optical waveguide, so that the heating efficiency of the heating electrode is fully improved, and the advantages of large thermo-optic coefficient and easiness in processing of the organic polymer material are utilized. Meanwhile, the manufacturing process adopted by the invention is simpler, compatible with a semiconductor process, easy to integrate and suitable for large-scale production, thereby having important application prospect.

The technical scheme adopted by the invention for solving the technical problems is as follows:

as shown in fig. 1(a), a low-power consumption ridge waveguide thermo-optic switch based on a buried graphene heating electrode is characterized in that: the whole device is based on a Mach-Zehnder interferometer (MZI) optical waveguide structure and sequentially comprises an input straight waveguide 1, a 3-dB Y-branch beam splitter 2, a device modulation area consisting of two parallel first interference arms 3 and second interference arms 4, a 3-dB Y-branch coupler 5 and an output straight waveguide 6 from left to right; the input straight waveguide 1 and the output straight waveguide 6 have the same structure and the length a₁And a₁' 0.5 to 1.5cm, 3 to 7 μm in width; the 3-dB Y-branch beam splitter 2 and the 3-dB Y-branch coupler 5 are identical in structure, the Y-branch angle theta is 0.5-1.5 degrees, the length of a Y branch is 1000-3000 mu m, and the width of the Y branch is 3-7 mu m; the two parallel first 3 and second 4 interference arms are of identical construction and have a length a₂And a₂' 0.5 to 1.5cm, 3 to 7 μm in width, and 30 to 100 μm in center-to-center distance d between two parallel interference arms; the widths of the input straight waveguide 1, the 3-dB Y-branch beam splitter 2, the first interference arm 3, the second interference arm 4, the 3-dB Y-branch coupler 5 and the output straight waveguide are the same;

as shown in fig. 1(b), which is a schematic plane structure diagram of a low power consumption ridge waveguide thermo-optic switch with a metal heating electrode 26(26 ') and a graphene heating electrode 24 (or 34), the metal heating electrode 26 (26') includes three parts, an effective heating area, an input and output area, and a metal heating electrode pin area; length L of effective heating zone₁1-2 cm, width W₁10-25 μm, center-to-center distance W between two effective heating areas₂30-80 μm, and the center-to-center distance L between the input and output regions of the metal heating electrode₂0.8-2 cm, input and output regions of metal heating electrodeLength L₃0.3-1 cm, width W₃50-200 μm, length L of the metal heating electrode pin₄500 to 1500 μm, width W₄2000-5000 μm; the length L of the metal pin 8 of the graphene heating electrode 24(34)₅2000 to 5000 μm, width W₅2000-5000 μm; except for the partial area of the metal pin 8, the rest area of the graphene heating electrode 24 (or 34) (including the effective heating area, the input and output area and the metal pin) is completely covered by the metal heating electrode 26, and the two areas are separated by the polymer upper cladding layer 25 (or 35) and a part of the optical waveguide core layer 23 (or 33);

as an embodiment, as shown in fig. 2(a) (a cross-sectional view corresponding to a cross-sectional view AA' in fig. 1 (b)), a low-power consumption inverted ridge waveguide thermo-optical switch based on a buried graphene heating electrode, from bottom to top, a MZI optical waveguide structure modulation region composed of two parallel first interference arms 3 and second interference arms 4 is sequentially composed of a silicon wafer substrate 21, a polymer lower cladding 22 with a waveguide groove structure prepared on the silicon wafer substrate 21, an optical waveguide core 23 with an inverted ridge waveguide structure prepared on the polymer lower cladding 22, a graphene heating electrode 24 prepared in the inverted ridge optical waveguide core 23, a polymer upper cladding 25 prepared on the optical waveguide core 23, a metal heating cladding prepared on the polymer upper cladding 25 (and also used as an etching mask for processing the graphene electrode) 26; the thickness of the silicon wafer substrate 21 is 0.5-1 mm, the thickness of the polymer lower cladding 22 is 4-7 μm, the width of a groove on the polymer lower cladding 22 is 3-7 μm, the depth of the groove is 0.5-2 μm, the total thickness of the optical waveguide core layer 23 is 3-8 μm, the ridge width of the optical waveguide core layer 23 is 3-7 μm, the ridge height is 0.5-2 μm, the width of the graphene heating electrode 24 is 10-30 μm, the thickness of the graphene heating electrode 24 is 0.4-1.7 nm, the thickness of the polymer upper cladding 25 is 3-6 μm, the width of the metal heating electrode 26 is 10-30 μm, and the thickness of the metal heating electrode 26 is 100-300 nm; the widths of the polymer lower cladding 22, the inverted ridge type optical waveguide core layer 23, the graphene heating electrode 24, the polymer upper cladding 25 and the metal heating electrode 26 are the same;

as another embodiment, as shown in fig. 2(b) (a cross-sectional view corresponding to a cross-sectional view AA' in fig. 1 (b)), a low-power consumption positive-ridge waveguide thermo-optical switch based on a buried graphene heating electrode, from bottom to top, a MZI optical waveguide structure modulation region composed of two parallel first and

second interference arms

3 and 4 is composed of a silicon wafer substrate 21, a polymer lower cladding layer 32 prepared on the silicon wafer substrate 21, an optical waveguide core layer 33 prepared on the polymer lower cladding layer 32 and having a positive-ridge optical waveguide structure, a graphene heating electrode 34 prepared in the positive-ridge optical waveguide core layer 33, a polymer upper cladding layer 35 prepared on the optical waveguide core layer 33, and a metal heating electrode (as an etching mask for processing the graphene electrode shape at the same time) 26 prepared on the polymer upper cladding layer 35; the thickness of the silicon wafer substrate 21 is 0.5-1 mm, the thickness of the polymer lower cladding 32 is 4-7 microns, the total thickness of the optical waveguide core layer 33 is 3-8 microns, the ridge width of the optical waveguide core layer 23 is 3-7 microns, the ridge height is 0.5-2 microns, the width of the graphene heating electrode 34 is 10-30 microns, the thickness of the graphene heating electrode 34 is 0.4-1.7 nm, the thickness of the polymer upper cladding 35 is 3-6 microns, the width of the metal heating electrode 26 is 10-30 microns, and the thickness of the metal heating electrode 26 is 100-300 nm; the widths of the polymer lower cladding layer 32, the positive ridge type optical waveguide core layer 33, the graphene heating electrode 34, the polymer upper cladding layer 35 and the metal heating electrode 26 are the same;

for the graphene heating electrode based low-power consumption inverted ridge waveguide thermo-optical switch shown in fig. 2(a), the region outside the modulation region of the MZI optical waveguide structure (the region not covered by the metal heating electrode 26) is composed of a silicon substrate 21, a polymer lower cladding layer 22, an inverted ridge optical waveguide core layer 23 and a polymer upper cladding layer 25 from bottom to top in sequence.

For the graphene heating electrode based low-power consumption positive ridge type waveguide thermo-optical switch shown in fig. 2(b), the region outside the modulation region of the MZI optical waveguide structure (the region not covered by the metal heating electrode 26) is composed of a silicon substrate 21, a polymer lower cladding layer 32, a positive ridge type optical waveguide core layer 33 and a polymer upper cladding layer 35 from bottom to top in sequence.

The preparation method of the low-power consumption ridge waveguide thermo-optical switch based on the buried graphene heating electrode is shown in the attached figure 3, and the specific description is as follows:

the preparation method of the low-power-consumption inverted ridge type waveguide thermo-optic switch based on the buried graphene heating electrode comprises the following steps:

a: cleaning process for silicon wafer substrate 21

Soaking the dissociated silicon wafer substrate 21 which meets the design size (the length is 2-5 cm; the width is 2-4 cm) in an acetone solution, ultrasonically cleaning for 5-12 minutes, then sequentially and repeatedly wiping the surface of the silicon wafer substrate by using acetone and ethanol cotton balls, washing the surface of the silicon wafer substrate by using deionized water, finally drying the silicon wafer substrate by using nitrogen, and baking the silicon wafer substrate for 1-3 hours at the temperature of 90-120 ℃ to remove water vapor;

b: polymer lower cladding 22 and preparation of upper groove thereof

Spin-coating a polymer lower cladding material on a cleaned silicon wafer substrate at a spin-coating speed of 2000-6000 rpm, and baking the obtained polymer film at 100-150 ℃ for 2-3 hours to obtain a polymer lower cladding with a thickness of 4-7 microns (the polymer lower cladding material is a series of organic polymer materials with good transparency and comprises polymethyl methacrylate (PMMA), Polycarbonate (PC), Polyimide (PI), Polyethylene (PE), Polyester (PET), Polystyrene (PS) and the like); then, evaporating an Al mask with the thickness of 50-200 nm on the prepared polymer lower cladding by adopting an evaporation process, then, spinning a positive photoresist BP212 with the thickness of 0.5-2.0 mu m on the Al film by adopting a spin coating process, and baking for 10-30 minutes at the temperature of 80-100 ℃; then, on a photoetching machine, closely contacting the positive photoresist with a photoetching mask plate to carry out plate-to-plate photoetching (the structure of the photoetching mask plate is complementary with the MZI core layer structure to be prepared), wherein the exposure time is 5-10 seconds, so that the positive photoresist BP212 in the waveguide core layer region of the MZI structure to be prepared is exposed; removing the photoetching mask plate, and removing the exposed positive photoresist BP212 after developing with a special developing solution for the photoresist for 10-30 seconds; baking for 5-20 minutes at 90-110 ℃ to obtain a required photoresist waveguide groove pattern on the Al film; then placing the film in NaOH solution with the mass concentration of 5-8 per mill for 50-90 seconds to remove the Al film which is not covered by the photoresist; then, carrying out dry etching in an Inductively Coupled Plasma (ICP) etching machine, wherein the etching radio frequency power is 300-500W, the bias power is 20-80W, the oxygen flow is 20-60 sccm, and the etching time is 30-240 seconds, so that a groove structure is etched on the polymer lower cladding; finally, fully exposing for 10-20 seconds under a photoetching machine to completely expose the residual positive photoresist BP212, removing the residual photoresist and an Al film covered by the residual photoresist by using NaOH solution with the mass concentration of 5-8 per mill, washing the device with deionized water, drying the device with nitrogen, and finally baking the device for 1-2 hours at the temperature of 90-120 ℃ to remove water vapor; the width of the obtained groove is 3-7 mu m, and the depth is 0.5-2 mu m;

c: preparation of optical waveguide core layer 23

Spin-coating an acetone corrosion resistant organic polymer core layer material (the polymer core layer is a series of ultraviolet negative photoresist materials which are insoluble in an acetone solvent after being irradiated by ultraviolet light and cured by heating and comprise SU-82002, SU-82005, EpoCore and EpoClad, and the refractive index of the core layer material is required to be larger than that of the upper cladding layer and the lower cladding layer of the optical waveguide) on the lower cladding layer by adopting a spin-coating process to form a film, wherein the spin-coating speed is 2000-6000 revolutions per minute, and the thickness of the film is 1-4 mu m; then, processing for 5-30 minutes at 70-100 ℃ for pre-baking, and then performing ultraviolet exposure under ultraviolet light with the wavelength of 350-400 nm; then, treating for 5-30 minutes at 70-100 ℃ for medium drying; finally, after the treatment is carried out for 30 to 90 minutes at the temperature of between 120 and 150 ℃, the film is baked and hardened, and thus the optical waveguide core layer 23' is prepared on the polymer lower cladding;

d: transferring graphene on optical waveguide core layer 23' and preparing metal pin 8

Placing commercially purchased suspended self-transfer single-layer graphene (purchased from combined-fertilizer microcrystalline material science and technology limited) with a polymethyl methacrylate (PMMA) supporting layer into a beaker filled with deionized water, transferring the graphene to the surface of a sample with a prepared optical waveguide core layer 23 ', enabling the single-layer graphene to be in contact with the optical waveguide core layer 23', and adjusting the position of graphene to enable the center of the graphene to be aligned with the center of an MZI waveguide modulation region; then naturally drying the mixture at 60-90 DEG CTreating for 30-60 minutes under the condition; then, gently dripping an acetone solution on the surface of the sample wafer by using a dropper to remove the PMMA film, removing the residual acetone solution by using deionized water, naturally drying the sample wafer, and treating for 30-60 minutes at 70-100 ℃; and finally, adopting a '+' solid metal mask plate, aligning and tightly attaching the center of the metal mask plate with the center of the graphene, and evaporating a layer of metal (gold or copper) (the thickness is 100-400 nm) at four corners of the graphene by adopting an evaporation process, wherein the length L of each metal pin is L₅2000 to 5000 μm, width W₅2000-5000 μm;

e: preparation of optical waveguide core layer 23 ″

Spin-coating materials of the optical waveguide core layer 23 '(the optical waveguide core layer 23' and the optical waveguide core layer 23 'are the same kind of organic polymer material and jointly form the optical waveguide core layer 23) on the optical waveguide core layer 23', the graphene and the metal pins 8 to form a film by adopting a spin-coating process, wherein the spin-coating speed is 2000-6000 revolutions per minute, and the film thickness is 1-4 mu m; then, processing for 5-30 minutes at 70-100 ℃ for pre-baking, and then performing ultraviolet exposure under ultraviolet light with the wavelength of 350-400 nm; then, treating for 5-30 minutes at 70-100 ℃ for medium drying; finally, processing for 30-90 minutes at 120-150 ℃ for post-baking hardening, so that the graphene film is prepared in the core layer 23 of the inverted ridge type optical waveguide;

f: preparation of Polymer overclad 25

Spin-coating a polymer upper cladding material (the polymer upper cladding is a series of organic polymer materials with good transparency including polymethyl methacrylate (PMMA), Polycarbonate (PC), Polyimide (PI), Polyethylene (PE), Polyester (PET), Polystyrene (PS) and the like) on the optical waveguide core layer 23 to form a film by adopting a spin-coating process, wherein the spin-coating speed is 2000-6000 r/min, then baking the film at 100-140 ℃ for 2-3 hours to prepare a polymer upper cladding 25 with the thickness of 3-6 mu m, and the polymer upper cladding 25 completely covers the optical waveguide core layer 23 of the whole MZI (including an input straight waveguide 1, 3-dB Y branch beam splitter 2, two parallel first interference arms 3 and second interference arms 4, a 3-dB Y branch coupler 5 and an output straight waveguide 6);

g: preparation of metallic heating electrode (etching mask) 26

Evaporating an Al mask with the thickness of 100-300 nm on the prepared polymer upper cladding 25 by adopting an evaporation process, then spin-coating a layer of positive photoresist BP218 with the thickness of 0.5-2.0 mu m on the Al film by adopting a spin-coating process, and baking for 10-30 minutes at the temperature of 80-100 ℃; then, on a photoetching machine, the electrode mask plate is closely contacted with an electrode mask plate for carrying out plate alignment photoetching, the center of the effective heating area of the electrode mask plate (the structure comprises an effective heating area of a metal heating electrode, an input and output area and a metal heating electrode pin) is aligned with the center of a modulation area (a first interference arm 3 and a second interference arm 4) of an MZI optical waveguide structure (as shown in figure 1 (b)), the exposure time is 5-15 seconds, the electrode mask plate is removed, and after development of a special developing solution for photoresist for 10-30 seconds, the exposed positive photoresist BP218 is removed; baking the Al film for 5 to 20 minutes at the temperature of between 90 and 110 ℃ so as to obtain a required photoresist mask pattern (such as patterns shown as 26 and 26' in figure 1 (b)); then placing the metal heating electrode in 5-8 per mill NaOH solution for 50-90 seconds to remove the Al film which is not covered by the photoresist, and obtaining a metal heating electrode 26 (which is used as an etching mask at the same time) with the width of 10-30 mu m;

h: preparation of graphene heating electrode 24

Performing dry etching in an ICP etching machine, wherein the etching radio frequency power is 300-500W, the bias power is 20-80W, the oxygen flow is 20-60 sccm, the argon flow is 1-5 sccm, the etching time is 150-600 seconds, in the etching process, the metal heating electrode 26 is used as an etching mask, the region except the graphene covering region shown in fig. 1(b) is shielded by a metal mask plate, the waveguide upper cladding 25, the optical waveguide core 23, the single-layer graphene film and the polymer lower cladding 22 which are not covered by the metal heating electrode 26 and the metal pin 8 within the graphene covering region shown in fig. 1(b) are etched by an ICP etching technology to expose the silicon wafer substrate 21, the polymer upper cladding 25, the optical waveguide core layer 23 and the polymer lower cladding 22 which are covered by the metal mask plate and the metal heating electrode cannot be etched, further, the graphene heater electrode 24 (the shape of the graphene heater electrode 24 and the dotted line shown in fig. 1 (b)) is completed.The shape of the metal heating electrode 26 in the wire frame is the same), and simultaneously, the metal pin 8 for applying a probe in the test is exposed, a polymer upper cladding 25 and an optical waveguide core layer 23' are arranged between the metal pin 8 and the metal heating electrode 26, the metal pin 8 is not directly contacted, and the length L of the metal pin 8 is the same₅2000 to 5000 μm, width W₅2000 to 5000 μm.

The preparation method of the low-power consumption positive ridge type waveguide thermo-optical switch based on the buried graphene heating electrode comprises the following steps:

a: cleaning process for silicon wafer substrate 21

b: preparation of Polymer undercladding layer 32

Spin-coating a polymer lower cladding material on a cleaned silicon wafer substrate 21 at a spin-coating speed of 2000-6000 rpm, and then baking the film at 100-150 ℃ for 2-3 hours to obtain a polymer lower cladding with a thickness of 4-7 microns (the polymer lower cladding is a series of organic polymer materials with good transparency, such as polymethyl methacrylate (PMMA), Polycarbonate (PC), Polyimide (PI), Polyethylene (PE), Polyester (PET), Polystyrene (PS), and the like);

c: preparation of optical waveguide core layer 33

Directly spin-coating an acetone corrosion resistant organic polymer core layer material (the polymer core layer is a series of ultraviolet negative photoresist materials which are insoluble in an acetone solvent after ultraviolet irradiation and heating curing and comprise SU-82002, SU-82005, EpoCore and EpoClad, and meanwhile, the refractive index of the core layer material is required to be larger than that of the optical waveguide upper cladding layer and the optical waveguide lower cladding layer material) on the lower cladding layer by adopting a spin-coating process to form a film, wherein the spin-coating speed is 2000-6000 revolutions per minute, and the thickness of the film is 1-4 mu m; then, processing for 5-30 minutes at 70-100 ℃ for pre-baking, and then performing ultraviolet exposure under ultraviolet light with the wavelength of 350-400 nm; then, treating for 10-30 minutes at 70-100 ℃ for medium drying; finally, the optical waveguide core layer 33' is prepared on the polymer lower cladding layer by treating the optical waveguide core layer for 30 to 90 minutes at the temperature of between 120 and 150 ℃ and then baking and hardening the film;

d: transferring graphene on optical waveguide core layer 33' and preparing metal pin 8

Placing commercially available suspended self-transferring single-layer graphene (purchased from combined-fertilizer microcrystalline material science and technology limited) with a polymethyl methacrylate (PMMA) supporting layer into a beaker filled with deionized water, transferring the graphene to the surface of a sample with a prepared optical waveguide core layer 33 ', enabling the single-layer graphene to be in contact with the optical waveguide core layer 33', and adjusting the position of graphene to enable the center of the graphene to be aligned with the center of an MZI waveguide modulation region; then, naturally drying the mixture, and treating the mixture for 30-60 minutes at the temperature of 60-90 ℃; then, gently dripping an acetone solution on the surface of the sample wafer by using a dropper to remove the PMMA film, removing the residual acetone solution by using deionized water, naturally drying the sample wafer, and treating for 30-60 minutes at 70-100 ℃; and finally, adopting a '+' solid-shaped metal mask plate, aligning and tightly attaching the center of the metal mask plate with the center of the graphene, and evaporating a layer of metal (gold or copper) (the thickness is 100-400 nm) at four corners of the graphene by adopting an evaporation process to obtain the length L of the metal pin 8₅2000 to 5000 μm, width W₅2000-5000 μm;

e: preparation of optical waveguide core layer 33' and ridge waveguide

Spin-coating materials of the optical waveguide core layer 33 '(the optical waveguide core layer 33' and the optical waveguide core layer 33 'are the same kind of organic polymer material and jointly form the optical waveguide core layer 33) on the optical waveguide core layer 33', the graphene and the metal pins 8 to form a film by adopting a spin-coating process, wherein the spin-coating speed is 2000-6000 revolutions per minute, and the film thickness is 1-4 mu m; then, processing for 5-30 minutes at 70-100 ℃ for pre-baking, and then performing ultraviolet exposure under ultraviolet light with the wavelength of 350-400 nm; then, treating the mixture at 70-100 ℃ for 10-30 minutes for medium drying, and treating the mixture at 120-150 ℃ for 30-90 minutes for post-drying and hardening; then, evaporating an Al mask with the thickness of 50-200 nm on the prepared optical waveguide core layer 33' by adopting an evaporation process, then, spinning a positive photoresist BP212 with the thickness of 0.5-2.0 mu m on the Al film by adopting a spin coating process, and baking for 10-30 minutes at the temperature of 80-100 ℃; then, on a photoetching machine, the positive photoresist is closely contacted with a waveguide mask plate for performing plate alignment photoetching (the structure of the waveguide mask plate is the same as that of an MZI core layer to be prepared), the exposure time is 5-10 seconds, and the positive photoresist BP212 in the region except the waveguide core layer of the MZI structure to be prepared is exposed; removing the waveguide mask plate, and removing the exposed positive photoresist BP212 after developing with a special developing solution for the photoresist for 10-30 seconds; baking for 5-20 minutes at 90-110 ℃ to obtain a required photoresist mask pattern on the Al film; then placing the film in NaOH solution with the mass concentration of 5-8 per mill for 50-90 seconds to remove the Al film which is not covered by the photoresist; then, dry etching is carried out in an Inductively Coupled Plasma (ICP) etching machine, the etching radio frequency power is 300-500W, the bias power is 20-80W, the oxygen flow is 20-60 sccm, and the etching time is 30-240 seconds, so that a positive ridge type waveguide structure (the width of a ridge is 3-7 microns, the height of the ridge is 0.5-2 microns, and the height of the ridge is less than the total thickness of the waveguide core layer 33 ") is prepared on the optical waveguide core layer 33", and graphene is prevented from being damaged; finally, fully exposing the sample wafer for 10-20 seconds under a photoetching machine to fully expose the residual positive photoresist BP212, removing the residual photoresist and an Al film covered by the residual photoresist by using a NaOH solution with the mass concentration of 5-8 per mill, washing the device clean by using deionized water, drying by using nitrogen, and finally baking the sample wafer for 1-2 hours at the temperature of 90-120 ℃ to remove water vapor; this places the graphene in the positive ridge optical waveguide core layer 33;

f: preparation of Polymer overclad 35

Spin-coating a polymer upper cladding material (the polymer upper cladding is a series of organic polymer materials with good transparency including polymethyl methacrylate (PMMA), Polycarbonate (PC), Polyimide (PI), Polyethylene (PE), Polyester (PET), Polystyrene (PS) and the like) on the optical waveguide core layer to form a film by adopting a spin-coating process, wherein the spin-coating speed is 2000-6000 r/min, then baking the film at 100-140 ℃ for 2-3 hours to prepare an upper cladding with the thickness of 3-6 mu m, and the polymer upper cladding 35 completely covers the optical waveguide core layer 33 of the whole MZI (including an input straight waveguide 1, 3-dB Y-branch beam splitter 2, two parallel first interference arms 3 and second interference arms 4, a 3-dB Y-branch coupler 5 and an output straight waveguide 6);

g: preparation of metallic heating electrode 26

Evaporating an Al mask with the thickness of 100-300 nm on the prepared polymer upper cladding 35 by adopting an evaporation process, then spin-coating a layer of positive photoresist BP218 with the thickness of 0.5-2.0 mu m on the Al film by adopting a spin-coating process, and baking for 10-30 minutes at the temperature of 80-100 ℃; then, on a photoetching machine, the electrode mask plate is closely contacted with an electrode mask plate for carrying out plate alignment photoetching, the center of the effective heating area of the electrode mask plate (the structure comprises an effective heating area of a metal heating electrode, an input and output area and a metal heating electrode pin) is aligned with the center of a modulation area (a first interference arm 3 and a second interference arm 4) of an MZI optical waveguide structure (as shown in figure 1 (b)), the exposure time is 5-15 seconds, the electrode mask plate is removed, and after development of a special developing solution for photoresist for 10-30 seconds, the exposed positive photoresist BP218 is removed; baking the Al film for 5 to 20 minutes at the temperature of between 90 and 110 ℃ so as to obtain a required photoresist mask pattern (such as patterns shown as 26 and 26' in figure 1 (b)); then placing the metal heating electrode in 5-8 per mill NaOH solution for 50-90 seconds to remove the Al film which is not covered by the photoresist, and obtaining a metal heating electrode 26 (which is used as an etching mask at the same time) with the width of 10-30 mu m;

h: preparation of graphene heating electrode 34

Performing dry etching in an ICP etching machine, wherein the etching radio frequency power is 300-500W, the bias power is 20-80W, the oxygen flow is 20-60 sccm, the argon flow is 1-5 sccm, and the etching time is 150-600 seconds, in the etching process, using the metal heating electrode 26 as an etching mask, shielding the area except the graphene covering area shown in the figure 1(b) by using a metal mask plate, and covering the waveguide which is not covered by the metal heating electrode 26 and the metal pin 8 in the graphene covering area shown in the figure 1(b)The layer 35, the optical waveguide core layer 33, the single-layer graphene film and the polymer lower cladding layer 32 are etched by an ICP (inductively coupled plasma) etching technology to expose the silicon wafer substrate 21, while the polymer upper cladding layer 35, the optical waveguide core layer 33 and the polymer lower cladding layer 32 which are covered by the metal mask plate and the metal heating electrode cannot be etched, so that the preparation of the graphene heating electrode 34 (the shape of the graphene heating electrode 34 is the same as that of the metal heating electrode 26 in a dotted frame shown in fig. 1 (b)) is completed, meanwhile, the metal pin 8 for applying a probe in a test is exposed, the polymer upper cladding layer 35 and the optical waveguide core layer 33 are arranged between the metal pin 8 and the metal heating electrode 26 and are not directly contacted, and the length L of the metal pin 8 is not directly contacted with each other₅2000 to 5000 μm, width W₅2000 to 5000 μm.

Compared with the prior device structure and preparation technology, the invention has the beneficial effects that: the ridge waveguide thermo-optic switch device based on the buried graphene heating electrode not only utilizes the advantage of large thermo-optic coefficient of organic polymer material, but also utilizes the advantage of flexible processing of organic polymer material to place the graphene heating electrode in the optical waveguide core layer, thereby effectively improving the heating efficiency of the electrode, achieving the purpose of reducing the power consumption of the thermo-optic switch device, and having small optical absorption damage caused by the graphene electrode; in addition, the manufacturing process of the device is simple, only some common semiconductor equipment and conventional manufacturing processes are needed, complex and expensive process equipment and high-difficulty preparation technology are not needed, the production cost is low, the efficiency is high, and the device is suitable for batch production of low-power consumption thermo-optical switching devices which can be practically applied.

Drawings

Fig. 1 (a): the MZI waveguide plane structure schematic diagram of the ridge waveguide thermo-optic switch based on the buried graphene heating electrode;

fig. 1 (b): planar structure schematic diagram of ridge waveguide thermo-optic switch based on buried graphene heating electrode

Fig. 2 (a): a schematic cross-sectional view of a modulation region of an inverted ridge waveguide thermo-optic switch based on a buried graphene heating electrode;

fig. 2 (b): a schematic cross-sectional view of a modulation region of a positive ridge waveguide thermo-optic switch based on a buried graphene heating electrode;

fig. 3 (a): a process flow diagram for preparing the inverted ridge waveguide thermo-optic switch based on the buried graphene heating electrode;

fig. 3 (b): a preparation process flow chart of a positive ridge type waveguide thermo-optic switch based on a buried graphene heating electrode;

fig. 4 (a): a modulation region optical field simulation diagram of the inverted ridge waveguide thermo-optic switch based on the buried graphene heating electrode;

fig. 4 (b): a modulation region optical field simulation diagram of a positive ridge type waveguide thermo-optic switch based on a buried graphene heating electrode;

fig. 5 (a): simulation results of loss caused by heating electrodes by graphene in the inverted ridge waveguide (C + L band);

fig. 5 (b): simulation results of loss caused by heating electrodes by graphene in the positive ridge waveguide (C + L band);

fig. 6 (a): preparing a microscopic picture of the cross section of the inverted ridge waveguide after the waveguide core layer is prepared;

fig. 6 (b): preparing a microscopic picture of the cross section of the positive ridge waveguide after the waveguide core layer is prepared;

fig. 7 (a): the change relation curve of the output optical power of the inverted ridge waveguide thermo-optical switch based on the buried graphene heating electrode and the metal heating electrode along with the change of the applied electric power;

fig. 7 (b): the change relation curve of the output optical power of the positive ridge type waveguide thermo-optical switch based on the buried graphene heating electrode and the metal heating electrode along with the applied electric power;

fig. 8 (a): the time response characteristic curve of the inverted ridge waveguide thermo-optic switch based on the buried graphene heating electrode;

fig. 8 (b): the time response characteristic curve of the positive ridge type waveguide thermo-optic switch based on the buried graphene heating electrode;

as shown in fig. 1(a), the waveguide plane structure of the ridge waveguide thermo-optical switch based on the buried graphene heating electrode is schematically illustrated, and the names of the components are: an input straight waveguide 1, 3-dB Y-branch splitter 2, two

parallel interference arms

3 and 4, 3-dB Y-branch couplers 5 and an output straight waveguide 6.

As shown in fig. 1(b), the schematic plane structure of the ridge waveguide thermo-optic switch based on the buried graphene heating electrode is as follows: the input straight waveguide 1, 3-dB Y-branch beam splitter 2, 3-dB Y-branch coupler 5, the output straight waveguide 6, a metal heating electrode 26(26 '), a metal pin 8 of a graphene heating electrode, and two parallel first interference arms 3 and second interference arms 4 are positioned right below the metal heating electrodes 26 and 26' and are aligned in the center.

As shown in fig. 2, (a) is a schematic cross-sectional view of a modulation region of an inverted ridge waveguide thermo-optic switch based on a buried graphene heating electrode, and the names of the components are: a silicon wafer substrate 21, a polymer lower cladding layer 22, an optical waveguide core layer 23 with an inverted ridge waveguide structure, a graphene heating electrode 24 buried in the optical waveguide core layer 23, a polymer upper cladding layer 25, and a metal heating electrode 26 (which are simultaneously used as an etching mask for processing the shape of the graphene electrode); (b) the figure is a schematic cross-sectional view of a modulation region of a positive ridge type waveguide thermo-optic switch based on a graphene heating electrode, and the names of all components are as follows: the silicon chip comprises a silicon chip substrate 21, a polymer lower cladding layer 32, an optical waveguide core layer 33 with a positive ridge type waveguide structure, a graphene heating electrode 34 buried in the optical waveguide core layer 33, a polymer upper cladding layer 35 and a metal heating electrode 26 (which are simultaneously used as an etching mask for processing the shape of the graphene electrode).

As shown in fig. 3, (a) is a flow chart of a manufacturing process of an inverted ridge waveguide thermo-optic switch based on a buried graphene heating electrode, in the drawing, 21 is a silicon wafer substrate, 22 is a polymer lower cladding with a waveguide groove structure manufactured on the silicon substrate 21 by a spin coating process, 23 'is an inverted ridge waveguide core layer manufactured by the spin coating process, 23 "is an optical waveguide core layer manufactured by the spin coating process, 23' and 23" are the same organic polymer waveguide core layer material and jointly form the optical waveguide core layer 23, 24 is a graphene heating electrode, 25 is a polymer upper cladding manufactured by the spin coating process, and 26 is a metal heating electrode and is an etching mask for processing the shape of the graphene electrode; (b) the figure is a flow chart of a preparation process of a positive ridge type waveguide thermo-optic switch based on a buried graphene heating electrode, wherein 21 in the figure is a silicon wafer substrate, 32 is a polymer lower cladding layer prepared on the silicon substrate 21 by adopting a spin coating process, 33 'is a polymer optical waveguide core layer prepared by adopting the spin coating process, 33' is a ridge type waveguide core layer prepared by adopting spin coating, photoetching and etching processes, 33 'and 33' are same organic polymer waveguide core layer materials and jointly form an optical waveguide core layer 33, 34 of the graphene heating electrode, 35 is a polymer upper cladding layer prepared by adopting the spin coating process, and 26 is a metal heating electrode and is also used as an etching mask for processing the shape of the graphene electrode.

As shown in fig. 4, (a) is a graph showing a modulation region optical field simulation diagram of an inverted ridge waveguide thermo-optical switch based on a buried graphene heating electrode in a TM polarization mode, and (b) is a graph showing a modulation region optical field distribution simulation diagram of a positive ridge waveguide thermo-optical switch based on a buried graphene heating electrode in a TM polarization mode.

As shown in fig. 5, (a) is a graph showing a simulation result of loss caused by the graphene heating electrode in the inverted ridge waveguide, and (b) is a graph showing a simulation result of loss caused by the graphene heating electrode in the positive ridge waveguide. From simulation results, in the range of the operating wavelength of the C + L waveband, the graphene electrodes in the two structures have larger absorption loss to an optical signal in a TE polarization mode, and in a TM polarization operating mode, the optical loss generated by the graphene heating electrode is below 0.15dB/cm, so that the loss of the whole device is hardly influenced, and the device can be operated in the TM polarization mode.

As shown in fig. 6, (a) is a waveguide cross-sectional microscope photograph of an inverted ridge waveguide thermo-optic switch based on a buried graphene heating electrode, the total thickness of a waveguide core layer is 4 μm, the thickness of a flat plate layer is 3 μm, the depth of a groove is 1 μm, and the width of the groove is 4 μm; (b) the figure is a photomicrograph of a cross section of a waveguide of a positive ridge type waveguide thermo-optic switch based on a buried graphene heating electrode, the total thickness of a waveguide core layer is 4.2 μm, the thickness of a flat plate layer is 3.2 μm, and the width of a ridge is 4 μm.

As shown in fig. 7, (a) is a graph showing the variation of output optical power of the inverted ridge waveguide thermo-optical switch with applied electric power based on the buried graphene heating electrode and the metal heating electrode, and (b) is a graph showing the variation of output optical power with applied electric power of the positive ridge waveguide thermo-optical switch based on the buried graphene heating electrode and the metal heating electrode, it can be seen from the test results that the power consumption of the thermo-optical switch device based on the buried graphene heating electrode is significantly lower than that of the metal heating electrode, and is respectively reduced from 4.76mW to 0.61mW and from 4.35mW to 0.64mW, and the extinction ratio is respectively 25.5dB and 24.9 dB.

As shown in fig. 8, (a) is a time response characteristic curve of an inverted ridge waveguide thermo-optic switch based on a buried graphene heating electrode, and the rising time and the falling time of the switch are 191.0 mus and 203.8 mus respectively; (b) the graph shows the time response characteristic curve of a positive ridge waveguide thermo-optic switch based on a buried graphene heating electrode, and the rising time and the falling time of the switch are respectively 220 mus and 240 mus.

Detailed Description

Example 1

Cleaning treatment of the silicon wafer substrate 21: and soaking the dissociated silicon wafer substrate which accords with the designed dimension (the length: 3.2 cm; the width: 1.8cm) in an acetone solution for ultrasonic cleaning for 10 minutes, then sequentially and repeatedly wiping the surface of the silicon wafer by using acetone and an ethanol cotton ball, washing the silicon wafer by using deionized water, finally drying the silicon wafer by using nitrogen, and baking the silicon wafer substrate for 2 hours at the temperature of 110 ℃ to remove moisture.

The polymer under-cladding 22 is prepared by a spin-on process: the polymer material PMMA is spin-coated on a cleaned silicon wafer substrate by adopting a spin-coating process, the spin-coating speed is 2500 rpm, and then the film is baked for 2.5 hours at the temperature of 120 ℃ to prepare the polymer lower cladding 22 with the thickness of 4.5 mu m.

Preparing a waveguide groove by adopting standard photoetching and dry etching processes: firstly, evaporating and plating an Al mask with the thickness of 100nm on a prepared polymer lower cladding 22 by adopting an evaporation process, then, carrying out spin coating on the Al film by adopting a spin coating process to form a layer of positive photoresist BP212 with the thickness of 1 mu m, and baking for 20 minutes at the temperature of 85 ℃; then, on a photoetching machine, the positive photoresist BP212 is closely contacted with a waveguide mask plate to carry out the plate alignment photoetching (the structure of the photoetching mask plate is complementary with the MZI core layer structure to be prepared), the exposure time is 8 seconds, and the positive photoresist BP212 of the waveguide core layer region of the MZI structure to be prepared is exposed; removing the waveguide mask plate, and removing the exposed positive photoresist BP212 after developing by using a developing solution special for the photoresist for 15 seconds; baking for 10 minutes at the temperature of 100 ℃ so as to obtain a required photoresist waveguide groove pattern on the Al film; then placing the film in NaOH solution with the mass concentration of 5 per mill for 60 seconds to remove the Al film which is not covered by the photoresist; then, dry etching is carried out in an Inductively Coupled Plasma (ICP) etching machine, the etching radio frequency power is 400W, the bias power is 40W, the oxygen flow is 40sccm, and the etching time is 50 seconds, so that a groove structure is etched on the polymer lower cladding; finally, the sample wafer is fully exposed for 15 seconds under a photoetching machine, so that the residual positive photoresist BP212 is completely exposed, then NaOH solution with the mass concentration of 5 per mill is used for removing the residual photoresist and the Al film covered by the photoresist, the device is washed clean by deionized water and then is dried by nitrogen, finally the sample wafer is baked for 1.5 hours at the temperature of 110 ℃ for removing moisture, and thus the waveguide groove is prepared, and the width and the depth of the groove are respectively 4 micrometers and 1 micrometer.

Preparing the optical waveguide core layer 23' by adopting a spin coating process: spin-coating an organic polymer core layer material SU-82002 corroded by an acetone solvent in a groove of the lower cladding layer by adopting a spin-coating process to form a film, wherein the spin-coating speed is 2500 rpm, and the thickness of the film is 2.5 mu m; then processing for 10 minutes at 85 ℃ for prebaking, and then carrying out ultraviolet exposure under ultraviolet light with the wavelength of 350 nm; then, the mixture is treated for 10 minutes at 90 ℃ for intermediate baking; finally, the post-baking hardening is performed at 140 ℃ for 60 minutes, thereby obtaining an optical waveguide core layer 23' on the polymer under clad layer.

Pasting graphene on the optical waveguide core layer 23' and preparing a metal pin 8: commercially available graphene (1 cm × 1cm in size, purchased from co-fertilizer microcrystalline materials science and technology limited) with a PMMA supporting layer suspended and self-transferred single-layer is placed in a beaker filled with deionized water, and then transferred to the surface of a sample of an optical waveguide core layer 23', the graphene is in contact with the optical waveguide core layer, and the position of the graphene is adjustedAligning the center of the graphene with the center of the MZI waveguide modulation region; then, the mixture is naturally dried and then is treated for 40 minutes at the temperature of 80 ℃; then, gently dripping an acetone solution on the surface of the sample wafer by using a dropper to remove the PMMA film, removing the residual acetone solution by using deionized water, naturally drying the sample wafer, and treating for 60 minutes at 90 ℃; finally, a metal mask plate in a '+' solid shape is adopted, the center of the metal mask plate is aligned with the center of the graphene and is tightly attached to the center of the graphene, a layer of metal (gold) (the thickness of the metal is 250nm) is evaporated at four corners of the graphene by an evaporation process, and the length L of each metal pin is equal to that of each metal pin₅3000 μm, width W₅And 3000 μm.

Preparing the optical waveguide core layer 23' by adopting a spin coating process: spin-coating another layer of SU-82002 on the graphene by a spin-coating process to form a film, wherein the spin-coating speed is 3500 rpm, and the film thickness is 1.5 mu m; then processing for 10 minutes at 85 ℃ for prebaking, and then carrying out ultraviolet exposure under ultraviolet light with the wavelength of 350 nm; then, the mixture is treated for 10 minutes at 85 ℃ for intermediate baking; finally, post-baking hardening is performed for 60 minutes at 140 ℃, so that the graphene is placed in the core layer of the inverted ridge type optical waveguide.

Preparing a polymer upper cladding by adopting a spin coating process: spin-coating a polymer upper cladding material PMMA on the optical waveguide core layer 23 by a spin-coating process to form a film, wherein the spin-coating speed is 3500 rpm, then baking the film at 120 ℃ for 2.5 hours to obtain a polymer upper cladding 25 with the thickness of 4 μm, wherein the polymer upper cladding 25 completely covers the optical waveguide core layer 23 of the whole MZI (comprising an input straight waveguide 1, a 3-dB Y-branch beam splitter 2, two parallel first and

second interference arms

3 and 4, a 3-dB Y-branch coupler 5 and an output straight waveguide 6).

Preparation of the metal heating electrode 26: evaporating an Al mask with the thickness of 200nm on the prepared polymer upper cladding 25 by adopting an evaporation process, then spin-coating a positive photoresist BP218 with the thickness of 1.5 mu m on the Al film by adopting a spin-coating process, and baking for 20 minutes at the temperature of 90 ℃; then, on a photoetching machine, the electrode mask plate is closely contacted with an electrode mask plate for carrying out plate alignment photoetching, the center of the effective heating area of the electrode mask plate (the structure comprises an effective heating area, an input and output area and a metal heating electrode pin of a metal heating electrode) is aligned with the center of a modulation area (a first interference arm 3 and a second interference arm 4) of an MZI optical waveguide structure (as shown in figure 1 (b)), the exposure time is 8 seconds, the electrode mask plate is removed, and after 20 seconds of photoresist special developing solution development, the exposed positive photoresist BP218 is removed; baking at 100 deg.C for 10 min to obtain the desired photoresist mask pattern (such as 26 and 26' shown in FIG. 1 (b)); then placing the metal heating electrode in NaOH solution with the mass concentration of 5 per mill for 50 seconds to remove the Al film which is not covered by the photoresist, and obtaining a metal heating electrode 26 with the width of 16 mu m (simultaneously used as an etching mask);

preparation of the graphene heating electrode 24: performing dry etching on a sample wafer in an ICP etching machine, wherein the etching radio frequency power is 400W, the bias power is 50W, the oxygen flow is 40sccm, the argon flow is 2sccm, the etching time is 480 seconds, in the etching process, the metal heating electrode 26 is used as an etching mask, the region except the graphene covering shown in figure 1(b) is shielded by a metal mask plate, the waveguide upper cladding 25, the optical waveguide core 23, the single-layer graphene film and the polymer lower cladding 22 which are not covered by the metal heating electrode 26 and the metal pin 8 in the graphene covering shown in figure 1(b) are etched by the ICP etching technology, the silicon wafer exposes the substrate 21, and the polymer upper cladding 25, the optical waveguide core 23 and the polymer lower cladding 22 which are not etched by the metal mask plate and the metal heating electrode are further completed, so that the graphene heating electrode 24 (the shape of the graphene heating electrode 24 and the metal heating electrode 26 in the dashed frame shown in figure 1(b) are covered by the ICP etching technology Same shape of the metal lead 8) for applying a probe in a test is prepared, and a polymer upper cladding 25 and an optical waveguide core layer 23' are arranged between the metal lead 8 and a metal heating electrode 26 without directly contacting, and the length L of the metal lead 8 is₅3000 μm, width W₅And 3000 μm.

Thus, the inverted ridge waveguide thermo-optic switch device based on the graphene heating electrode, which meets the design requirements, is prepared, and meanwhile, the traditional metal heating electrode positioned on the surface of the waveguide upper cladding is also prepared. After the preparation, the inverted ridge waveguide thermo-optical switch based on the graphene heating electrode prepared in example 1 was tested for power consumption and time response characteristics, and the test instrument included a function signal generator providing an ac electrical signal, a dc power supply providing a dc electrical signal, a tunable semiconductor laser (waveguide adjustment range is 1510nm to 1590nm) providing an input optical signal, a five-dimensional fine-tuning frame for adjusting alignment of an optical fiber and an optical waveguide, an infrared camera for observing an output spot of the waveguide, an optical power meter for measuring insertion loss of a device, and a digital oscilloscope for observing response of the device. Under the wavelength of 1550nm signal light, the insertion loss of the device in a TM polarization mode is measured to be 12.1 dB; then, the current passing through the graphene heating electrode and the metal heating electrode is controlled by respectively changing the voltage applied to the two ends of the graphene heating electrode and the two ends of the metal heating electrode, the output light power of the device is monitored by an optical power meter, a change relation curve of the output light power of the device along with the change of the applied electric power is shown in fig. 7(a), the power consumption of the device based on the metal electrode is respectively measured to be 4.76mW, the power consumption of the device based on the graphene heating electrode is 0.61mW, and the power consumption of the device is effectively reduced by introducing the graphene heating electrode; finally, response time is tested by applying square wave alternating current signals to the inverted ridge waveguide thermo-optic switching device based on the graphene heating electrode, and the rise time and the fall time of the device switch are respectively 191.0 mus and 203.8 mus, as shown in fig. 8 (a).

Example 2

Cleaning treatment of the silicon wafer substrate 21: and soaking the dissociated silicon wafer substrate which accords with the designed dimension (the length: 3.0cm and the width: 1.8cm) in an acetone solution for ultrasonic cleaning for 10 minutes, then sequentially and repeatedly wiping the surface of the silicon wafer by using acetone and an ethanol cotton ball, washing the silicon wafer by using deionized water, finally drying the silicon wafer by using nitrogen, and baking the silicon wafer substrate for 2 hours at the temperature of 110 ℃ to remove moisture.

The polymer lower cladding 32 is prepared using a spin-on process: the polymer material PMMA is spin-coated on a cleaned silicon wafer substrate by adopting a spin-coating process, the spin-coating speed is 2500 rpm, and then the film is baked for 2.5 hours at the temperature of 120 ℃ to prepare the polymer lower cladding 32 with the thickness of 4.5 mu m.

Preparing the optical waveguide core layer 33' by adopting a spin coating process: spin-coating an organic polymer core layer material SU-82002 resistant to acetone solvent corrosion on the lower cladding layer by adopting a spin-coating process to form a film, wherein the spin-coating speed is 2500 revolutions per minute, and the thickness of the film is 1.5 mu m; then processing for 10 minutes at 85 ℃ for prebaking, and then carrying out ultraviolet exposure under ultraviolet light with the wavelength of 350 nm; then, the mixture is treated for 10 minutes at 85 ℃ for intermediate baking; finally, the post-baking hardening is performed at 140 ℃ for 60 minutes, thereby obtaining an optical waveguide core layer 33' on the polymer under clad layer 32.

Pasting graphene on the optical waveguide core layer 33' and preparing a metal pin 8: commercially available graphene (with the size of 1cm multiplied by 1cm, purchased from combined-fertilizer microcrystalline material science and technology limited) with a PMMA supporting layer suspended and self-transferred single-layer is placed in a beaker filled with deionized water, and then the graphene is transferred to the surface of a sample of an optical waveguide core layer 33', and the position of the graphene is adjusted, so that the center of the graphene is aligned with the center of an MZI waveguide modulation region; then, the mixture is naturally dried and then is treated for 40 minutes at the temperature of 80 ℃; then, gently dripping an acetone solution on the surface of the sample wafer by using a dropper to remove the PMMA film, removing the residual acetone solution by using deionized water, naturally drying the sample wafer, and treating for 60 minutes at 90 ℃; finally, a metal mask plate in a '+' solid shape is adopted, the center of the metal mask plate is aligned with the center of the graphene and is tightly attached to the center of the graphene, a layer of metal (gold) (the thickness of the metal is 250nm) is evaporated at four corners of the graphene by an evaporation process, and the length L of each metal pin is equal to that of each metal pin₅3000 μm, width W₅And 3000 μm.

The optical waveguide core layer 33' is prepared by adopting a spin coating process: spin-coating another layer of SU-82002 on the graphene by a spin-coating process to form a film, wherein the spin-coating speed is 2500 rpm, and the thickness of the film is 2.7 mu m; then processing for 10 minutes at 85 ℃ for prebaking, and then carrying out ultraviolet exposure under ultraviolet light with the wavelength of 350 nm; then, the mixture is treated for 10 minutes at 85 ℃ for intermediate baking; finally, the film is subjected to postbaking hardening treatment at 140 ℃ for 60 minutes.

The positive ridge core layer waveguide 33 is prepared by adopting the processes of evaporation, spin coating, photoetching and etching: firstly, evaporating and plating an Al mask with the thickness of 100nm on a prepared optical waveguide core layer 33' by adopting an evaporation process, then, spin-coating a layer of positive photoresist BP212 with the thickness of 1 mu m on an Al film by adopting a spin-coating process, and baking for 20 minutes at the temperature of 85 ℃; then, on a photoetching machine, the positive photoresist BP212 is closely contacted with a waveguide mask plate to carry out the plate alignment photoetching (the structure of the waveguide mask plate is the same as that of the MZI core layer to be prepared), the exposure time is 8 seconds, and the positive photoresist BP212 in the area except the waveguide core layer of the MZI structure to be prepared is exposed; removing the waveguide mask plate, and removing the exposed positive photoresist BP212 after developing by using a developing solution special for the photoresist for 15 seconds; baking for 10 minutes at the temperature of 100 ℃ so as to obtain a required photoresist mask pattern on the Al film; then placing the film in NaOH solution with the mass concentration of 5 per mill for 60 seconds to remove the Al film which is not covered by the photoresist; then, dry etching is carried out in an Inductively Coupled Plasma (ICP) etching machine, the etching radio frequency power is 400W, the bias power is 40W, the oxygen flow is 30sccm, and the etching time is 50 seconds, so that a positive ridge type waveguide structure (the height of the ridge is 1 μm, and the width is 4 μm) is prepared on the optical waveguide core layer 33 ″; finally, fully exposing the sample wafer for 15 seconds under a photoetching machine to completely expose the residual positive photoresist BP212, removing the residual photoresist and an Al film covered by the residual photoresist by using NaOH solution with the mass concentration of 5 per mill, washing the device clean by using deionized water, drying by using nitrogen, and finally baking the sample wafer for 1.5 hours at the temperature of 110 ℃ to remove water vapor; this places the graphene in the positive ridge optical waveguide core 33.

The polymer upper cladding 35 is prepared by a spin-coating process: spin-coating a polymer upper cladding material PMMA on an optical waveguide core layer to form a film by adopting a spin-coating process, wherein the spin-coating speed is 2500 rpm, then baking the film at 100-140 ℃ for 2.5 hours to obtain a polymer upper cladding with the thickness of 4 mu m, and the polymer upper cladding 35 completely covers the optical waveguide core layer 33 of the whole MZI (comprising an input straight waveguide 1, a 3-dB Y-branch beam splitter 2, two parallel first interference arms 3 and second interference arms 4, a 3-dB Y-branch coupler 5 and an output straight waveguide 6).

Preparation of the metal heating electrode 26: evaporating an Al mask with the thickness of 200nm on the prepared polymer upper cladding 35 by adopting an evaporation process, then spin-coating a positive photoresist BP218 with the thickness of 1.5 mu m on the Al film by adopting a spin-coating process, and baking for 20 minutes at the temperature of 90 ℃; then, on a photoetching machine, the electrode mask plate is closely contacted with an electrode mask plate for carrying out plate alignment photoetching, the center of the effective heating area of the electrode mask plate (the structure comprises an effective heating area, an input and output area and a metal heating electrode pin of a metal heating electrode) is aligned with the center of a modulation area (a first interference arm 3 and a second interference arm 4) of an MZI optical waveguide structure (as shown in figure 1 (b)), the exposure time is 8 seconds, the electrode mask plate is removed, and after 20 seconds of photoresist special developing solution development, the exposed positive photoresist BP218 is removed; baking at 100 deg.C for 10 min to obtain the desired photoresist mask pattern (such as 26 and 26' shown in FIG. 1 (b)); then placing the metal heating electrode in NaOH solution with the mass concentration of 5 per mill for 50 seconds to remove the Al film which is not covered by the photoresist, and obtaining a metal heating electrode 26 with the width of 16 mu m (simultaneously used as an etching mask);

preparation of the graphene heating electrode 34: performing dry etching on a sample wafer in an ICP etching machine, wherein the etching radio frequency power is 400W, the bias power is 50W, the oxygen flow is 40sccm, the argon flow is 2sccm, the etching time is 480 seconds, in the etching process, the metal heating electrode 26 is used as an etching mask, the region except the graphene covering shown in figure 1(b) is shielded by a metal mask plate, the waveguide upper cladding 35, the optical waveguide core layer 33, the single-layer graphene film and the polymer lower cladding 32 which are not covered by the metal heating electrode 26 and the metal pin 8 in the graphene covering shown in figure 1(b) are etched by an ICP etching technology to expose the silicon wafer substrate 21, and the polymer upper cladding 35, the optical waveguide core layer 33 and the polymer lower cladding 32 which are not etched by the metal mask plate and the metal heating electrode are further completed to cover the graphene heating electrode 34 (the shape of the graphene heating electrode 34 and the metal heating electrode 26 in a dotted frame shown in figure 1(b) Same shape of the metal lead 8) for applying a probe for test is prepared while exposing the metal lead 8 for applying a probe for test, and a polymer over clad layer 35 and an optical waveguide core layer 33 are interposed between the metal lead 8 and the metal heater electrode 26 "Length L of metal pin 8 without direct contact₅3000 μm, width W₅Is 3000 μm

Thus, the positive ridge type waveguide thermo-optical switch device based on the graphene heating electrode, which meets the design requirements, is prepared, and meanwhile, the traditional metal heating electrode positioned on the surface of the waveguide upper cladding is also prepared. After the preparation, the positive ridge type waveguide thermo-optical switch based on the graphene heating electrode prepared in example 2 was tested for power consumption and time response characteristics, and the test instrument included a function signal generator providing an ac electrical signal, a dc power supply providing a dc electrical signal, a tunable semiconductor laser (waveguide adjustment range is 1510nm to 1590nm) providing an input optical signal, a five-dimensional fine-tuning frame for adjusting alignment of an optical fiber and an optical waveguide, an infrared camera for observing an output spot of the waveguide, an optical power meter for measuring insertion loss of a device, and a digital oscilloscope for observing response of the device. Under the wavelength of 1550nm signal light, the insertion loss of the device in a TM polarization mode is measured to be 12.5 dB; then, the current passing through the graphene heating electrode and the metal heating electrode is controlled by respectively changing the voltage applied to the two ends of the graphene heating electrode and the two ends of the metal heating electrode, the output light power of the device is monitored by an optical power meter, fig. 7(b) shows a change relation curve of the output light power of the device along with the change of the applied electric power, the power consumption of the device based on the metal electrode is respectively measured to be 4.35mW, the power consumption of the device based on the graphene heating electrode is 0.64mW, and the introduction of the graphene heating electrode effectively reduces the power consumption of the device; finally, response time is tested by applying square wave alternating current signals to the inverted ridge waveguide thermo-optic switching device based on the graphene heating electrode, and the rise time and the fall time of the device switch are respectively measured to be 220 mus and 240 mus, as shown in fig. 8 (b).

Claims

1. The utility model provides a low-power consumption ridge waveguide thermo-optic switch based on bury graphite alkene heating electrode which characterized in that:

the whole device is of an MZI optical waveguide structure and comprises, from left to right, an input straight waveguide (1), a 3-dB Y-branch beam splitter (2), a device modulation region consisting of a first interference arm (3) and a second interference arm (4) which are parallel, a 3-dB Y-branch coupler (5) and an output straight waveguide (6); the input straight waveguide (1) and the output straight waveguide (6) have the same structure, the 3-dB Y-branch beam splitter (2) and the 3-dB Y-branch coupler (5) have the same structure, and the two parallel first interference arms (3) and the second interference arms (4) have the same structure; the widths of the input straight waveguide (1), the 3-dB Y-branch beam splitter (2), the first interference arm (3) and the second interference arm (4), the 3-dB Y-branch coupler (5) and the output straight waveguide (6) are the same;

from bottom to top, an MZI optical waveguide structure modulation region formed by a first interference arm (3) and a second interference arm (4) which are parallel to each other sequentially consists of a silicon wafer substrate (21), a polymer lower cladding (22) with a waveguide groove structure, an optical waveguide core layer (23) with an inverted ridge type waveguide structure, a graphene heating electrode (24) prepared in the inverted ridge type optical waveguide core layer (23), a polymer upper cladding (25) prepared on the optical waveguide core layer (23) and a metal heating electrode (26) prepared on the polymer upper cladding (25); the widths of the polymer lower cladding (22), the inverted ridge type optical waveguide core layer (23), the graphene heating electrode (24), the polymer upper cladding (25) and the metal heating electrode (26) are the same;

the region outside the MZI optical waveguide structure modulation region is sequentially composed of a silicon chip substrate (21), a polymer lower cladding (22), an inverted ridge type optical waveguide core layer (23) and a polymer upper cladding (25) from bottom to top;

the metal heating electrode (26) comprises an effective heating area, an input and output area and a metal heating electrode pin area; except for the partial area of the metal pin (8) of the graphene heating electrode (24), the rest area of the graphene heating electrode (24) is completely covered by the metal heating electrode (26), and the graphene heating electrode and the metal heating electrode are separated by a polymer upper cladding layer (25) and a part of the optical waveguide core layer (23).

2. The buried graphene heating electrode-based low work function of claim 1A ridge-consuming waveguide thermo-optic switch is characterized in that: length a of input straight waveguide (1) and output straight waveguide (6)₁And a₁ ^’0.5-1.5 cm and 3-7 mu m in width; the Y branch angle theta of the 3-dB Y branch beam splitter (2) and the 3-dB Y branch coupler (5) is 0.5-1.5 degrees, the length of the Y branch is 1000-3000 mu m, and the width of the Y branch is 3-7 mu m; two parallel first (3) and second (4) interference arms of length a₂And a₂The' is 0.5-1.5 cm, the width is 3-7 mu m, and the center-to-center distance d between two parallel interference arms is 30-100 mu m; the thickness of the silicon wafer substrate (21) is 0.5-1 mm, the thickness of the polymer lower cladding (22) is 4-7 mu m, the width of a groove on the polymer lower cladding (22) is 3-7 mu m, the depth of the groove is 0.5-2 mu m, the total thickness of the optical waveguide core layer (23) is 3-8 mu m, the ridge width of the optical waveguide core layer (23) is 3-7 mu m, the ridge height is 0.5-2 mu m, the width of the graphene heating electrode (24) is 10-30 mu m, the thickness of the graphene heating electrode (24) is 0.4-1.7 nm, the thickness of the polymer upper cladding (25) is 3-6 mu m, the width of the metal heating electrode (26) is 10-30 mu m, and the thickness of the metal heating electrode (26) is 100-300 nm; the length L of the effective heating zone of the metal heating electrode (26)₁1-2 cm, width W₁Is 10 to 25 mu m, and the center-to-center distance W between two effective heating areas₂Is 30-80 mu m, and the center-to-center distance L of the input and output areas of the metal heating electrode (26)₂0.8-2 cm, length L of input and output region of the metal heating electrode₃0.3-1 cm, width W₃Is 50 to 200 mu m, and the length L of the metal heating electrode pin₄Is 500 to 1500 mu m and has a width W₄2000-5000 mu m; the length L of a metal pin (8) of a graphene heating electrode (24)₅Is 2000-5000 mu m and has a width W₅Is 2000-5000 mu m.

3. The preparation method of the buried graphene heating electrode-based low-power consumption ridge waveguide thermo-optical switch as claimed in claim 1, comprising the following steps:

a: cleaning process for silicon wafer substrate (21)

Soaking the dissociated silicon wafer substrate (21) which accords with the designed size in an acetone solution for ultrasonic cleaning for 5-12 minutes, then sequentially and repeatedly wiping the surface of the silicon wafer substrate by using acetone and ethanol cotton balls, washing the silicon wafer substrate by using deionized water, finally drying the silicon wafer substrate by using nitrogen, and baking the silicon wafer substrate for 1-3 hours at the temperature of 90-120 ℃ to remove water vapor;

b: preparation of polymer lower cladding (22) and upper groove thereof

Spin-coating a polymer lower cladding material on a cleaned silicon wafer substrate at a spin-coating speed of 2000-6000 rpm by adopting a spin-coating process, and then baking the obtained polymer film at 100-150 ℃ for 2-3 hours to obtain a polymer lower cladding with the thickness of 4-7 mu m; then, evaporating an Al mask with the thickness of 50-200 nm on the prepared polymer lower cladding by adopting an evaporation process, then performing spin coating on the Al film by adopting a spin coating process to form a positive photoresist BP212 with the thickness of 0.5-2.0 mu m, and baking for 10-30 minutes at the temperature of 80-100 ℃; then, on a photoetching machine, closely contacting the positive photoresist with a photoetching mask plate to carry out plate photoetching, wherein the structure of the photoetching mask plate is complementary with the MZI core layer structure to be prepared, and the exposure time is 5-10 seconds, so that the positive photoresist BP212 in the waveguide core layer region of the MZI structure to be prepared is exposed; removing the photoetching mask plate, and removing the exposed positive photoresist BP212 after developing with a special developing solution for the photoresist for 10-30 seconds; baking for 5-20 minutes at 90-110 ℃ to obtain a required photoresist waveguide groove pattern on the Al film; then placing the film in NaOH solution with the mass concentration of 5-8 per mill for 50-90 seconds to remove the Al film which is not covered by the photoresist; then, carrying out dry etching in an inductively coupled plasma etching machine, wherein the etching radio frequency power is 300-500W, the bias power is 20-80W, the oxygen flow is 20-60 sccm, and the etching time is 30-240 seconds, so that a groove structure is etched on the polymer lower cladding; finally, fully exposing for 10-20 seconds under a photoetching machine to completely expose the residual positive photoresist BP212, removing the residual photoresist and an Al film covered by the residual photoresist by using NaOH solution with the mass concentration of 5-8 per mill, washing the device with deionized water, drying the device with nitrogen, and finally baking the device for 1-2 hours at the temperature of 90-120 ℃ to remove water vapor;

c: preparation of the first optical waveguide core layer (23

Spin-coating the acetone corrosion resistant optical waveguide core layer material on the lower cladding layer by adopting a spin-coating process to form a film, wherein the spin-coating speed is 2000-6000 revolutions per minute, and the thickness of the film is 1-4 mu m; then, processing for 5-30 minutes at 70-100 ℃ for prebaking, and then carrying out ultraviolet exposure under ultraviolet light with the wavelength of 350-400 nm; then, treating for 5-30 minutes at 70-100 ℃ for medium drying; finally, post-baking and hardening the film for 30 to 90 minutes at the temperature of 120 to 150 ℃, thus obtaining a first optical waveguide core layer (23') on the polymer lower cladding;

d: transferring graphene on the first optical waveguide core layer (23') and making metal pins (8)

Placing the suspended self-transfer single-layer graphene with the PMMA supporting layer into a beaker filled with deionized water, transferring the graphene to the surface of a sample with a prepared first optical waveguide core layer (23 '), making the single-layer graphene contact with the first optical waveguide core layer (23'), adjusting the position of graphene, and aligning the center of the graphene with the center of an MZI waveguide modulation region; then, naturally airing the dried material, and treating the dried material for 30-60 minutes at the temperature of 60-90 ℃; then, gently dripping an acetone solution on the surface of the sample wafer by using a dropper to remove the PMMA film, removing the residual acetone solution by using deionized water, naturally drying the sample wafer, and treating for 30-60 minutes at the temperature of 70-100 ℃; finally, adopting a + solid-shaped metal mask plate, aligning and tightly attaching the center of the + solid-shaped metal mask plate with the center of the graphene, and evaporating a layer of metal at four corners of the graphene by adopting an evaporation process to obtain metal pins (8);

e: preparation of the second optical waveguide core layer (23 ″)

Spin-coating the second optical waveguide core layer (23 ' ') material on the first optical waveguide core layer (23 '), the graphene and the metal pins (8) to form a film by adopting a spin-coating process, wherein the spin-coating speed is 2000-6000 rpm; then, processing for 5-30 minutes at 70-100 ℃ for prebaking, and then carrying out ultraviolet exposure under ultraviolet light with the wavelength of 350-400 nm; then, treating for 5-30 minutes at 70-100 ℃ for medium drying; the second optical waveguide core layer (23 ') and the first optical waveguide core layer (23') are made of the same organic polymer material and jointly form the optical waveguide core layer (23); finally, processing for 30-90 minutes at 120-150 ℃ for post-baking hardening, so that the graphene film is prepared in the core layer (23) of the inverted ridge type optical waveguide;

f: preparation of a polymeric overclad (25)

Spin-coating a polymer upper cladding material on the optical waveguide core layer (23) by adopting a spin-coating process to form a film, wherein the spin-coating speed is 2000-6000 rpm, then baking the film at 100-140 ℃ for 2-3 hours to obtain a polymer upper cladding (25), and the polymer upper cladding (25) completely covers the optical waveguide core layer (23) of the whole MZI structure;

g: preparation of a metallic heating electrode (26)

An Al mask with the thickness of 100-300 nm is vapor-plated on the prepared polymer upper cladding (25) by adopting a vapor deposition process, a positive photoresist BP218 with the thickness of 0.5-2.0 mu m is spin-coated on the Al film by adopting a spin coating process, and the Al film is baked for 10-30 minutes at the temperature of 80-100 ℃; then, on a photoetching machine, closely contacting the electrode mask plate with an electrode mask plate to carry out plate alignment photoetching, wherein the electrode mask plate structure comprises an effective heating area of a metal heating electrode, an input area, an output area and a metal heating electrode pin, the center of the effective heating area of the electrode mask plate is aligned with the center of a modulation area of an MZI optical waveguide structure, the exposure time is 5-15 seconds, the electrode mask plate is removed, and after 10-30 seconds of development liquid special for photoresist is used for developing, the exposed positive photoresist BP218 is removed; baking for 5-20 minutes at 90-110 ℃ to obtain a required photoresist mask pattern on the Al film; then placing the metal heating electrode in NaOH solution with the mass concentration of 5-8 per mill for 50-90 seconds to remove the Al film which is not covered by the photoresist, and obtaining a metal heating electrode (26);

h: preparation of graphene heating electrode (24)

Performing dry etching in an ICP etching machine, wherein the etching radio frequency power is 300-500W, the bias power is 20-80W, the oxygen flow is 20-60 sccm, the argon flow is 1-5 sccm, and the etching time is 150-600 seconds, in the etching process, a metal heating electrode (26) is used as an etching mask, the region outside the graphene covering region is shielded by a metal mask plate, the waveguide upper cladding (25), the optical waveguide core layer (23), the single-layer graphene film and the polymer lower cladding (22) which are not covered by the metal heating electrode (26) and the metal pin (8) in the graphene covering region are etched through an ICP etching technology, the silicon wafer exposes the substrate (21), and the polymer upper cladding (25), the optical waveguide core layer (23) and the polymer lower cladding (22) of the metal mask plate and the metal heating electrode are not etched, so that the preparation of the graphene heating electrode (24) is completed, meanwhile, a metal pin (8) for applying a probe in the test is exposed, and a polymer upper cladding layer (25) and a second optical waveguide core layer (23 '') are arranged between the metal pin (8) and a metal heating electrode (26) and are not in direct contact.

4. The utility model provides a low-power consumption ridge waveguide thermo-optic switch based on bury graphite alkene heating electrode which characterized in that:

from bottom to top, an MZI optical waveguide structure modulation region formed by a first interference arm (3) and a second interference arm (4) which are parallel to each other sequentially consists of a silicon wafer substrate (21), a polymer lower cladding (32) prepared on the silicon wafer substrate (21), an optical waveguide core layer (33) which is prepared on the polymer lower cladding (32) and has a positive ridge type optical waveguide structure, a graphene heating electrode (34) prepared in the positive ridge type optical waveguide core layer (33), a polymer upper cladding (35) prepared on the optical waveguide core layer (33) and a metal heating electrode (26) prepared on the polymer upper cladding (35); the widths of the polymer lower cladding (32), the positive ridge type optical waveguide core layer (33), the graphene heating electrode (34), the polymer upper cladding (35) and the metal heating electrode (26) are the same;

the region outside the MZI optical waveguide structure modulation region is composed of a silicon substrate (21), a polymer lower cladding (32), a positive ridge type optical waveguide core layer (33) and a polymer upper cladding (35) from bottom to top in sequence;

the metal heating electrode (26) comprises an effective heating area, an input and output area and a metal heating electrode pin area; except for the partial area of the metal pin (8) of the graphene heating electrode (34), the rest area of the graphene heating electrode (34) is completely covered by the metal heating electrode (26), and the graphene heating electrode and the metal heating electrode are separated by a polymer upper cladding layer (35) and a part of an optical waveguide core layer (33).

5. The buried graphene heating electrode-based low-power consumption ridge waveguide thermo-optic switch of claim 4, wherein: length a of input straight waveguide (1) and output straight waveguide (6)₁And a₁ ^’0.5-1.5 cm and 3-7 mu m in width; the Y branch angle theta of the 3-dB Y branch beam splitter (2) and the 3-dB Y branch coupler (5) is 0.5-1.5 degrees, the length of the Y branch is 1000-3000 mu m, and the width of the Y branch is 3-7 mu m; two parallel first (3) and second (4) interference arms of length a₂And a₂The' is 0.5-1.5 cm, the width is 3-7 mu m, and the center-to-center distance d between two parallel interference arms is 30-100 mu m; the thickness of a silicon wafer substrate (21) is 0.5-1 mm, the thickness of a polymer lower cladding (32) is 4-7 mu m, the total thickness of an optical waveguide core layer (33) is 3-8 mu m, the ridge width and the ridge height of the optical waveguide core layer (23) are 3-7 mu m and 0.5-2 mu m respectively, the width of a graphene heating electrode (34) is 10-30 mu m, the thickness of the graphene heating electrode (34) is 0.4-1.7 nm, the thickness of a polymer upper cladding (35) is 3-6 mu m, the width of a metal heating electrode (26) is 10-30 mu m, and the thickness of the metal heating electrode (26) is 100-300 nm; metal heating electrode (2)6) Length L of effective heating zone₁1-2 cm, width W₁Is 10 to 25 mu m, and the center-to-center distance W between two effective heating areas₂Is 30-80 mu m, and the center-to-center distance L of the input and output areas of the metal heating electrode (26)₂0.8-2 cm, length L of input and output region of the metal heating electrode₃0.3-1 cm, width W₃Is 50 to 200 mu m, and the length L of the metal heating electrode pin₄Is 500 to 1500 mu m and has a width W₄2000-5000 mu m; the length L of a metal pin (8) of a graphene heating electrode (34)₅Is 2000-5000 mu m and has a width W₅Is 2000-5000 mu m.

6. The method for preparing a low-power consumption ridge waveguide thermo-optical switch based on a buried graphene heating electrode according to claim 4, comprising the following steps:

a: cleaning process for silicon wafer substrate (21)

b: preparation of Polymer undercladding layer (32)

Spin-coating a polymer lower cladding material on a cleaned silicon wafer substrate (21) at a spin-coating speed of 2000-6000 rpm by adopting a spin-coating process, and then baking the film at 100-150 ℃ for 2-3 hours to obtain a polymer lower cladding (32) with the thickness of 4-7 mu m;

c: preparation of the first optical waveguide core layer (33

Directly spin-coating the acetone corrosion resistant optical waveguide core layer material on the lower cladding layer (32) to form a film by adopting a spin-coating process, wherein the spin-coating speed is 2000-6000 r/min, and the thickness of the film is 1-4 mu m; then, processing for 5-30 minutes at 70-100 ℃ for prebaking, and then carrying out ultraviolet exposure under ultraviolet light with the wavelength of 350-400 nm; then, treating for 10-30 minutes at 70-100 ℃ for intermediate baking; finally, post-baking and hardening the film for 30 to 90 minutes at the temperature of 120 to 150 ℃, thus obtaining a first optical waveguide core layer (33') on the polymer lower cladding;

d: transferring graphene on a first optical waveguide core layer (33') and fabricating metal pins (8)

Placing the suspended self-transfer single-layer graphene with the PMMA supporting layer into a beaker filled with deionized water, transferring the graphene to the surface of a sample with a prepared first optical waveguide core layer (33 '), making the single-layer graphene contact with the first optical waveguide core layer (33'), adjusting the position of graphene, and aligning the center of the graphene with the center of an MZI waveguide modulation region; then, naturally airing the dried material, and treating the dried material for 30-60 minutes at the temperature of 60-90 ℃; then, gently dripping an acetone solution on the surface of the sample wafer by using a dropper to remove the PMMA film, removing the residual acetone solution by using deionized water, naturally drying the sample wafer, and treating for 30-60 minutes at the temperature of 70-100 ℃; finally, adopting a + solid-shaped metal mask plate, aligning and tightly attaching the center of the + solid-shaped metal mask plate with the center of the graphene, and evaporating a layer of metal at four corners of the graphene by adopting an evaporation process to obtain metal pins (8);

e: preparation of the second optical waveguide core layer (33') and the ridge waveguide

Spin-coating the material of the second optical waveguide core layer (33 ' ') on the first optical waveguide core layer (33 '), the graphene and the metal pins 8 to form a film by adopting a spin-coating process, wherein the spin-coating speed is 2000-6000 revolutions per minute, and the thickness of the film is 1-4 mu m; then, processing for 5-30 minutes at 70-100 ℃ for prebaking, and then carrying out ultraviolet exposure under ultraviolet light with the wavelength of 350-400 nm; then, treating the mixture at 70-100 ℃ for 10-30 minutes for medium drying, and treating the mixture at 120-150 ℃ for 30-90 minutes for post-drying hardening; then, an Al mask with the thickness of 50-200 nm is vapor-plated on the prepared second optical waveguide core layer (33 '') by adopting a vapor deposition process, a positive photoresist BP212 with the thickness of 0.5-2.0 mu m is spin-coated on the Al film by adopting a spin-coating process, and the Al film is baked for 10-30 minutes at the temperature of 80-100 ℃; then, on a photoetching machine, closely contacting the waveguide mask plate with the waveguide mask plate to carry out the plate alignment photoetching, wherein the structure of the waveguide mask plate is the same as that of the MZI core layer to be prepared, and the exposure time is 5-10 seconds, so that the positive photoresist BP212 in the region except the waveguide core layer of the MZI structure to be prepared is exposed; removing the waveguide mask plate, and removing the exposed positive photoresist BP212 after developing with a special developing solution for the photoresist for 10-30 seconds; baking for 5-20 minutes at 90-110 ℃ to obtain a required photoresist mask pattern on the Al film; then placing the film in NaOH solution with the mass concentration of 5-8 per mill for 50-90 seconds to remove the Al film which is not covered by the photoresist; then, dry etching is carried out in an inductively coupled plasma etching machine, the etched radio frequency power is 300-500W, the bias power is 20-80W, the oxygen flow is 20-60 sccm, and the etching time is 30-240 seconds, so that a positive ridge type waveguide structure is prepared on the second optical waveguide core layer (33 ''); finally, fully exposing the sample wafer for 10-20 seconds under a photoetching machine to completely expose the residual positive photoresist BP212, removing the residual photoresist and an Al film covered by the residual photoresist by using a NaOH solution with the mass concentration of 5-8 per mill, washing the device clean by using deionized water, drying by using nitrogen, and finally baking for 1-2 hours at the temperature of 90-120 ℃ to remove water vapor; the second optical waveguide core layer (33 ') and the first optical waveguide core layer (33') are made of the same organic polymer material and form the optical waveguide core layer (33), so that the graphene is arranged in the positive ridge type optical waveguide core layer (33);

f: preparation of a polymeric overclad (35)

Spin-coating a polymer upper cladding material on the optical waveguide core layer (33) by adopting a spin-coating process to form a film, wherein the spin-coating speed is 2000-6000 rpm, then baking the film at 100-140 ℃ for 2-3 hours to obtain an upper cladding, and the polymer upper cladding (35) completely covers the optical waveguide core layer (33) of the whole MZI structure;

g: preparation of a metallic heating electrode (26)

An Al mask with the thickness of 100-300 nm is vapor-plated on the prepared polymer upper cladding (35) by adopting a vapor deposition process, a positive photoresist BP218 with the thickness of 0.5-2.0 mu m is spin-coated on the Al film by adopting a spin coating process, and the Al film is baked for 10-30 minutes at the temperature of 80-100 ℃; then, on a photoetching machine, closely contacting the electrode mask plate with an electrode mask plate to carry out plate alignment photoetching, wherein the structure of the electrode mask plate comprises an effective heating area of a metal heating electrode, an input and output area and a metal heating electrode pin, the center of the effective heating area of the electrode mask plate is aligned with the center of a modulation area of an MZI optical waveguide structure, the exposure time is 5-15 seconds, the electrode mask plate is removed, and after 10-30 seconds of development of a special developing solution for photoresist, the exposed positive photoresist BP218 is removed; baking for 5-20 minutes at 90-110 ℃ to obtain a required photoresist mask pattern on the Al film; then placing the metal heating electrode in NaOH solution with the mass concentration of 5-8 per mill for 50-90 seconds to remove the Al film which is not covered by the photoresist, and obtaining a metal heating electrode (26);

h: preparation of graphene heating electrode (34)

Performing dry etching in an ICP etching machine, wherein the etching radio frequency power is 300-500W, the bias power is 20-80W, the oxygen flow is 20-60 sccm, the argon flow is 1-5 sccm, and the etching time is 150-600 seconds, in the etching process, a metal heating electrode (26) is used as an etching mask, the region outside the graphene covering region is shielded by a metal mask plate, the waveguide upper cladding (35), the optical waveguide core layer (33), the single-layer graphene film and the polymer lower cladding (32) which are not covered by the metal heating electrode (26) and the metal pin (8) in the graphene covering region are etched by an ICP etching technology, the silicon chip substrate (21) is exposed, and the polymer upper cladding (35), the optical waveguide core layer (33) and the polymer lower cladding (32) which are covered by the metal mask plate and the metal heating electrode are not etched, so as to complete the preparation of the graphene heating electrode (34), meanwhile, a metal pin (8) for applying a probe in the test is exposed, and a polymer upper cladding layer (35) and a second optical waveguide core layer (33 '') are arranged between the metal pin (8) and the metal heating electrode (26) and are not in direct contact.

7. A low power consumption ridge waveguide thermo-optic switch based on buried graphene heating electrodes as claimed in claims 1, 2, 4 or 5, characterized in that: the polymer under-cladding (22 or 32) is polymethylmethacrylate, polycarbonate, polyimide, polyethylene, polyester or polystyrene; the optical waveguide core layer (23 or 33) is SU-82002, SU-82005, EpoCore, or EpoClad; the polymer over-cladding (25 or 35) is polymethylmethacrylate, polycarbonate, polyimide, polyethylene, polyester or polystyrene.