Optical switch based on quantum confined stark effect and microcavity and preparation method thereof

Abstract

The application is a kind of optical switch based on quantum limited Stark effect and microcavity and a preparation method thereof, the structure of the optical switch from bottom to top: the first layer is a quartz substrate, the second layer is a bottom distributed Bragg reflector (DBR) composed of multiple pairs of high refractive index thin film and low refractive index thin film, the third layer is an interdigital electrode etched on the bottom DBR and a group II- VI semiconductor nanosheet (NPL) arranged uniformly and orderly between the electrodes, and the fourth layer is a top DBR composed of multiple pairs of high refractive index thin film and low refractive index thin film. The optical switch based on quantum limited Stark effect and microcavity provided by the application introduces a Stark effect device into a micro resonant cavity, enhances the incident light by means of the resonance characteristics of the microcavity on the working wavelength, and prolongs the effective interaction length of the incident light and the nanosheet through the microcavity, thereby enhancing the light absorption effect of the nanosheet and improving the transmittance modulation range of the optical switch.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of optical switch based on quantum limit starker effect and microcavity and its preparation method, belong to optical switch technical field. BACKGROUND

[0002] Optical microcavity is a kind of through resonance recycling to limit light to propagate in a specific space for a long time. Optical microcavity can compress the light field coupled into the limited compression, and the compressed light field has high energy density and specific light field distribution, which can strongly enhance the interaction between light and matter, and is widely used in photonic device field.

[0003] At present, optical fiber communication network still needs a large number of optical / electric conversion between different nodes, with the rapid growth of information transmission, it has been more and more difficult to meet the needs of contemporary technology, and all-optical communication network is thus born. Compared with the traditional "electric-optical-electric" transmission mode, all-optical communication network can greatly improve the transmission rate. Large-scale high-speed optical switch is the key device of future all-optical communication network with cross connection function, and its performance directly affects the whole optical network, so people have been continuously researching on optical switch, and various optical switches based on different principles have been developed. The optical switch based on quantum limit starker effect has picosecond response time, and is not affected by the polarization mode of input light signal, which has good application prospect. However, the current all-optical switch based on nanosheet has low utilization rate of incident light, low response sensitivity, and the modulation efficiency of transmitted light needs to be improved. SUMMARY

[0004] In view of the shortcomings and deficiencies of the existing nanosheet optical switch, the present application proposes an optical switch based on quantum limit starker effect and microcavity and its preparation method. The optical switch introduces nanosheet optical switch into micro resonant cavity, enhances the incident light by means of the resonance characteristics of microcavity to working wavelength, and prolongs the effective interaction length of incident light and nanosheet, thereby enhancing the light absorption effect of nanosheet and improving the transmittance modulation range of optical switch.

[0005] The optical switch based on quantum confinement Stark effect and microcavity of the application comprises, from bottom to top, a quartz substrate, a bottom distributed Bragg reflector (DBR), an interdigital electrode and a top DBR; the bottom DBR and the top DBR each comprise alternately deposited high refractive index thin films and low refractive index thin films, and the thickness of a single thin film is one quarter of a target wavelength; wherein II-VI semiconductor nanosheets (NPLs) are uniformly and orderly arranged between the interdigital electrode, the nanosheets are multilayered and face downward; the II-VI semiconductor nanosheets are CdSe / CdS nanosheets and are core / crown heterostructure CdSe / CdS nanosheets; the high refractive index thin films and the low refractive index thin films are transparent to the target wavelength;

[0006] Further, the high refractive index thin films refer to titanium dioxide (TiO2), zinc sulfide (ZnS) or hafnium dioxide (HfO2) thin films; and the low refractive index thin films refer to silicon dioxide (SiO2), calcium fluoride (CaF2) or magnesium fluoride (MgF2) thin films;

[0007] Further, the number of the alternately deposited high refractive index thin films and low refractive index thin films is 8-12; the reflectivity of the bottom DBR is slightly lower than that of the top DBR by adjusting the number of thin films of the bottom DBR and the top DBR, so that the incident light can preferentially exit through the bottom DBR.

[0008] The preparation method of the optical switch based on quantum confinement Stark effect and microcavity of the application comprises the following steps:

[0009] Step 1: depositing a bottom DBR on a quartz substrate;

[0010] Step 2: etching an interdigital electrode on the bottom DBR;

[0011] Step 3: uniformly and orderly arranging II-VI semiconductor nanosheets (NPLs) between the interdigital electrode;

[0012] Step 4: depositing a top DBR above the interdigital electrode.

[0013] Further, the specific process of depositing the bottom DBR on the quartz substrate in step 1 is as follows:

[0014] After the quartz substrate is cleaned, it is dried by using nitrogen, is placed in a high-vacuum coating machine, is heated to 150 DEG C under a high-vacuum environment, and alternately deposited high refractive index thin films and low refractive index thin films on the quartz substrate by electron beam evaporation, wherein the thickness of a single thin film is one quarter of a target wavelength.

[0015] Further, the specific process of etching the interdigital electrode on the bottom DBR in step 2 is as follows:

[0016] The quartz substrate with deposited bottom DBR is dehydrated and baked, photoresist is coated on the bottom DBR, most of the solvent in the photoresist is removed by soft baking and the exposure characteristics of the photoresist are fixed, the mask with periodic cross structure is used to block the bottom to perform exposure and development, an Au film is plated in a high vacuum environment, the photoresist is cleaned to obtain a periodic interdigital electrode structure, and metal wires are arranged on both sides of the interdigital electrode as positive and negative terminals for connecting external voltage.

[0017] Further, the II-VI semiconductor nanosheet in step 3 is a CdSe / CdS nanosheet, and is a CdSe / CdS nanosheet with core / crown heterostructure, and the preparation process is as follows:

[0018] Step 3.1, preparation of CdSe core nanosheet;

[0019] Cd precursor preparation: mix cadmium acetate, oleic acid and octadecene, continuously stir in air, heat to 150℃ and simultaneously perform ultrasonic treatment until a white gel is generated;

[0020] S precursor preparation: add sulfur powder to octadecene, heat to 160℃ under argon condition, continuously stir until the sulfur powder is dissolved, cool to 100℃ and keep for 1h;

[0021] Put cadmium oxide, tetradecanoic acid and octadecene into a three-necked flask, perform degassing under argon gas with magnetic stirring, degas for 30min at 110℃, continue to heat to 285℃ until the solution is colorless and transparent, cool to 90℃, degas for 30min by adding selenium powder, heat to 195℃, add cadmium acetate, continue to heat to 240℃, and the reaction generates CdSe core nanosheet; quickly cool to room temperature, inject oleic acid when the temperature drops to 180℃, and reserve the reaction product;

[0022] Step 3.2, preparation of CdSe / CdS core / crown nanosheet;

[0023] Mix Cd precursor and S precursor and continuously stir until use; add all the products of synthesized CdSe nanosheet core to octadecene, perform degassing under argon gas with magnetic stirring; heat to 240℃, slowly inject the precursors through a syringe pump; after the injection is completed, heat at 240℃ for 5min, quickly cool to room temperature; add n-hexane-ethanol mixed solution to centrifugal purification, and disperse the prepared CdSe / CdS core / crown nanosheet in n-hexane.

[0024] Further, the II-VI semiconductor nanosheet in step 3 is a CdSe / CdS nanosheet, and is a CdSe / CdS nanosheet with core / crown heterostructure, and the preparation process is as follows:

[0025] The substrate etched with the interdigital electrode is placed on a wedge-shaped glass table in a polytetrafluoroethylene container, acetonitrile is added to the polytetrafluoroethylene container, and the interdigital electrode is completely immersed in the acetonitrile; the CdSe / CdS core / crown nanosheet solution is dropped, and silicon oil is dropped on the other side of the container to generate surface pressure on the nanosheets; after the n-hexane is completely evaporated, the nanosheet film suspended on the liquid surface is obtained, the acetonitrile is slowly discharged, and the self-assembled film is deposited between the electrodes in a face-down manner, and the residual acetonitrile is vacuum evaporated at room temperature; the above process is repeated to obtain the required number of nanosheet layers.

[0026] Further, the top DBR is deposited above the interdigital electrode in step 4, and the specific process is as follows:

[0027] After the device deposited with the nanosheets is completely dried, it is placed in a high-vacuum coating machine, and high-refractive thin films and low-refractive thin films are alternately deposited by electron beam evaporation in a high-vacuum environment, wherein the thickness of a single thin film is one-fourth of the target wavelength, and the deposition temperature is less than 50 DEG C to prevent the nanosheets from failing.

[0028] Beneficial effects: The optical switch enhances the incident light by means of the resonance characteristics of the microcavity on the working wavelength, and prolongs the effective interaction length of the incident light with the nanosheets through the microcavity, thereby enhancing the light absorption effect of the nanosheets and improving the transmission modulation range of the optical switch. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a device structure diagram of the present application;

[0030] Figure 2 is an interdigital electrode diagram deposited with nanosheets.

[0031] wherein 1 is a quartz substrate, 2 is a bottom DBR, 3 is an interdigital electrode, and 4 is a top DBR. DETAILED DESCRIPTION

[0032] As shown in Figure 1 The optical switch based on quantum confinement Stark effect and microcavity of the present application comprises, from bottom to top, a quartz substrate 1, a bottom DBR 2, an interdigital electrode 3, and a top DBR 4; the bottom DBR 2 and the top DBR 4 each comprise high-refractive thin films and low-refractive thin films deposited alternately, and the thickness of a single thin film is one-fourth of the target wavelength; wherein the interdigital electrode 3 is uniformly and orderly arranged with Ⅱ-Ⅵ semiconductor nanosheets NPLs, the nanosheets are multilayered, and face down. The Ⅱ-Ⅵ semiconductor nanosheets are CdSe / CdS nanosheets, and are core / crown heterostructure CdSe / CdS nanosheets.

[0033] The preparation method of the optical switch based on quantum confinement Stark effect and microcavity of the present application specifically comprises the following steps:

[0034] Step 1, depositing bottom DBR 2 on quartz substrate 1;

[0035] The quartz substrate 1 is cleaned by ultrasonic cleaning with deionized water, acetone and ethanol for 30 minutes respectively, and then is placed in ethanol solution for use;

[0036] The quartz substrate 1 for use is dried by nitrogen and is placed in a high vacuum coating machine, and the coating material is placed in an electron beam evaporation crucible. The evaporation chamber is pumped to high vacuum (10^(-4) Pa);

[0037] The vacuum chamber is heated to 150℃, and the substrate is rotated at a constant speed;

[0038] The electron beam evaporation voltage is adjusted to 7800V-8200V, so that the deposition rate of the material reaches 1.5A / s. High refractive index thin films and low refractive index thin films are alternately deposited on the quartz substrate 1;

[0039] The evaporation thickness is monitored by a film thickness monitor. When the thickness of a single layer of thin film is one quarter of the target wavelength, the coating is stopped and the material is switched. Finally, the bottom DBR 2 is obtained.

[0040] Step 2, etching interdigital electrodes 3 on the bottom DBR 2, with an electrode spacing of 4μm;

[0041] The quartz substrate 1 with the bottom DBR 2 is baked to remove water. It is baked at 150-200℃ in a vacuum or dry nitrogen atmosphere;

[0042] Spin coating, a layer of negative su8 photoresist is coated on the bottom DBR 2, with a thickness of about 2μm;

[0043] Soft baking, remove most of the solvent in the photoresist and fix the exposure characteristics of the glue. The soft baking temperature is 90-100℃, and the time is 10min

[0044] Exposure with a mask to block the substrate;

[0045] Post-exposure baking, activate the chemical properties of the photoresist after exposure. The temperature is 90℃, and the time is 5min;

[0046] Developing, soaking in a 5% NaOH solution, and controlling the developing degree by controlling the soaking time;

[0047] Hard baking, remove residual developing solution and distilled water by baking at 150-200℃ in a vacuum or dry nitrogen atmosphere;

[0048] Coating a layer of gold (Au) with a thickness of 2μm by vacuum coating machine;

[0049] The Au-plated quartz wafer is soaked in an acetone photoresist cleaning solution to remove the su-8 and the Au thereon, thereby obtaining a periodic electrode structure, and metal wires are arranged on both sides of the interdigital electrode 3 to serve as positive and negative terminals for connecting an external voltage.

[0050] Step 3, the II-VI semiconductor nanosheet NPLs arranged uniformly and orderly between the interdigital electrode 3, wherein the uniform and orderly arrangement refers to that the multilayer nanosheets are deposited between the electrodes in a face-down manner, the II-VI semiconductor nanosheet is a CdSe / CdS nanosheet, and is a CdSe / CdS nanosheet with a core / crown heterostructure, and specifically includes the following steps:

[0051] Step 3.1, preparation of CdSe core nanosheets (4MLs);

[0052] Cd precursor preparation: 480 mg of cadmium acetate, 340 μL of oleic acid and 2 mL of octadecene are mixed and placed in a 10 mL glass bottle, continuously stirred in air, heated to 150°C and simultaneously subjected to ultrasonic treatment until a white gel is formed;

[0053] S precursor preparation: 0.096 g of sulfur powder is added to 30 mL of octadecene, and is added to a 100 ml three-necked flask, argon is introduced for degassing for 20 min, and the temperature is raised to 160°C, and the stirring is continued until the sulfur powder is dissolved, and the temperature is lowered to 100°C for 1 h, and the temperature is lowered to room temperature for sealing preservation;

[0054] 70 mg of cadmium oxide, 340 mg of myristic acid and 30 mL of octadecene are added to a three-necked flask, argon is introduced for degassing for 20 min under the condition of magnetic stirring, and the temperature is raised to 110°C for 30 min, and the temperature is continuously raised to 285°C until the solution is colorless and transparent, and the temperature is lowered to 90°C; 24 mg of selenium powder is added and degassed for 30 min, and the temperature is raised to 195°C, and 160 mg of cadmium acetate is added; the temperature is continuously raised to 240°C, and the reaction is carried out for 10 min to obtain CdSe core nanosheets; the temperature is rapidly lowered to room temperature, and 1 mL of oleic acid is injected when the temperature is lowered to 180°C, and the reaction product is reserved for use;

[0055] Step 3.2, preparation of CdSe / CdS core / crown nanosheets;

[0056] 3 mL of S precursor is added to all the Cd precursors, and the stirring is continuously carried out until use; all the products for synthesizing CdSe nanosheet cores are added to 5 mL of octadecene, argon is introduced for degassing for 20 min under the condition of magnetic stirring; the temperature is raised to 240°C, and the precursors are slowly injected at a speed of 8 mL / h through a syringe pump; after the injection is completed, the temperature is maintained at 240°C for 5 min, and the temperature is rapidly lowered to room temperature; a n-hexane-ethanol mixed solution is added and centrifuged to purify, and the prepared CdSe / CdS core / crown nanosheets are dispersed in n-hexane.

[0057] The bottom DBR 2 with the interdigital electrode 3 etched thereon is placed on a wedge-shaped glass stage in a polytetrafluoroethylene container, and a CdSe / CdS core / crown nanosheet n-hexane solution is added to control the orientation of the nanosheets through liquid-gas interface self-assembly.

[0058] The bottom DBR 2 with the interdigital electrode 3 etched thereon is placed on a wedge-shaped glass stage in a polytetrafluoroethylene container as a substrate, the polytetrafluoroethylene container has a diameter of 64 mm, a drain hole at the bottom, and the wedge-shaped glass stage has an included angle of 10° and a size of 3 cm X 3 cm; acetonitrile solution is added to cover the glass stage, and a CdSe / CdS core / crown nanosheet n-hexane solution is dropped from the top, and silicon oil is dropped on the other side of the liquid surface to generate surface pressure on the nanosheets; after the n-hexane solvent is completely evaporated, the acetonitrile is slowly drawn out, so that the self-assembled film is deposited between the electrodes in a face-down manner, and the residual acetonitrile is vacuum evaporated at room temperature; the above process is repeated to obtain the required number of nanosheet layers.

[0059] The top DBR 4 is deposited above the interdigital electrode 3 in step 4;

[0060] After the device with deposited nanosheets is completely dried, it is placed in a high-vacuum coating machine, and the coating material is placed in an electron beam evaporation crucible, and the evaporation chamber is pumped to high vacuum (10^(-4) Pa);

[0061] The rotation is turned on to rotate the substrate at a constant speed;

[0062] The electron beam evaporation voltage is adjusted to 7800V-8200V, so that the deposition rate of the material reaches 1.5A / s, and high refractive index thin films and low refractive index thin films are alternately deposited on the device;

[0063] The evaporation thickness is monitored by a film thickness monitor, and when the thickness of a single-layer thin film is one-fourth of the target wavelength, the coating is stopped and the material is switched; finally, the top DBR 4 is obtained.

Claims

1. An optical switch based on the quantum confined Stark effect and a microcavity, characterized in that, The quartz substrate, the bottom DBR, the interdigital electrode and the top DBR are arranged from bottom to top in order of low degree; The bottom DBR and the top DBR each comprise high refractive index thin films and low refractive index thin films which are alternately deposited, and the thickness of a single thin film is a quarter of the target wavelength; The Ⅱ-Ⅵ semiconductor nanosheets are arranged in an orderly and uniform manner between the interdigital electrodes, and the nanosheets are multilayered and face downward.

2. The optical switch based on quantum confined Stark effect and microcavity according to claim 1, characterized in that, The Ⅱ-Ⅵ semiconductor nanosheets are CdSe / CdS nanosheets, and are CdSe / CdS nanosheets in core / crown heterostructure.

3. The optical switch based on quantum confined Stark effect and microcavity according to claim 1, wherein, The high refractive index thin film refers to a titanium dioxide TiO2, zinc sulfide ZnS or hafnium dioxide HfO2 thin film; The low refractive index thin film refers to a silicon dioxide SiO2, calcium fluoride CaF2 or magnesium fluoride MgF2 thin film.

4. The optical switch based on quantum confined Stark effect and microcavity according to claim 1, wherein, The number of the alternately deposited high refractive index thin films and low refractive index thin films is 8-12; The reflectivity of the bottom DBR is slightly lower than that of the top DBR by adjusting the number of thin films of the bottom DBR and the top DBR, so that the incident light can preferentially pass through the bottom DBR and exit.

5. The method of claim 1, wherein the method further comprises: forming a first electrode on the substrate; forming a second electrode on the substrate; and forming a quantum dot layer between the first electrode and the second electrode. The method comprises the following steps: Step 1: depositing a bottom DBR on a quartz substrate; Step 2: etching an interdigital electrode on the bottom DBR; Step 3: arranging Ⅱ-Ⅵ semiconductor nanosheets NPLs in an orderly and uniform manner between the interdigital electrodes; Step 4: depositing a top DBR above the interdigital electrode.

6. The method of claim 5, wherein the method further comprises: The specific process of depositing the bottom DBR on the quartz substrate in step 1 is as follows: After the quartz substrate is cleaned, it is blown dry with nitrogen, placed in a high-vacuum coating machine, heated to 150℃ in a high-vacuum environment, and high refractive index thin films and low refractive index thin films are alternately deposited on the quartz substrate by electron beam evaporation.

7. The method of claim 5, wherein the method further comprises: forming a first electrode on the substrate; forming a second electrode on the substrate; and forming a microcavity between the first electrode and the second electrode. The specific process of etching the interdigital electrode on the bottom DBR in step 2 is as follows: After the quartz substrate with the deposited bottom DBR is baked, photoresist is coated on the bottom DBR, most of the solvents in the photoresist are removed by soft baking and the exposure characteristics of the photoresist are fixed, a mask with a periodic cross structure is used to block the deposition and exposure, a layer of gold (Au) film is deposited in a high-vacuum environment, the photoresist is cleaned to obtain a periodic interdigital electrode structure, and metal wires are led out on both sides of the interdigital electrode for connecting the positive and negative electrodes of an external voltage.

8. The method for preparing the optical switch based on quantum confined Stark effect and microcavity according to claim 5, wherein, The Ⅱ-Ⅵ semiconductor nanosheets are CdSe / CdS nanosheets, and are CdSe / CdS nanosheets in core / crown heterostructure, and the preparation process is as follows: Step 3.1: preparation of CdSe core nanosheets; Cd precursor preparation: mix cadmium acetate, oleic acid and octadecene, continuously stir in air, heat to 150℃ and simultaneously perform ultrasonic treatment until a white gel is generated; S precursor preparation: add sulfur powder to octadecene, heat to 160℃ under argon, continuously stir until the sulfur powder dissolves, and cool to 100℃ for 1h; CdSe / CdS core / crown nanosheets were prepared by the following steps: CdSe core nanosheets were prepared by the following steps: Cd, myristic acid, octadecene were added into a three-necked flask, and argon was bubbled through the solution under magnetic stirring to remove oxygen. The solution was heated to 110°C for 30 min, and then heated to 285°C until the solution was colorless and transparent. The solution was cooled to 90°C, and selenium powder was added into the solution. The solution was heated to 195°C, and then Cd(OAc)2 was added into the solution. The solution was heated to 240°C, and CdSe core nanosheets were obtained. The solution was cooled to room temperature rapidly, and then oleic acid was added into the solution when the temperature was 180°C. The reaction product was reserved for use; Step 3.2, preparation of CdSe / CdS core / crown nanosheets; Cd precursor and S precursor were mixed and stirred constantly until use. The whole product of CdSe nanosheet core was added into octadecene, and argon was bubbled through the solution under magnetic stirring to remove oxygen. The solution was heated to 240°C, and then the precursors were slowly injected through a syringe pump. The solution was heated at 240°C for 5 min after the injection was completed, and then the solution was cooled to room temperature rapidly. n-Hexane-ethanol mixed solution was added into the solution, and the solution was centrifuged and purified. The prepared CdSe / CdS core / crown nanosheets were dispersed in n-hexane.

9. The method of claim 5, wherein the method further comprises the step of: The Ⅱ-Ⅵ semiconductor nanosheets arranged uniformly and orderly between the interdigital electrodes in step 3 were prepared by the following steps: ​ The substrate etched with interdigital electrodes was placed on a wedge-shaped glass platform in a polytetrafluoroethylene container, and acetonitrile was added into the container. The interdigital electrodes were completely immersed in the acetonitrile. CdSe / CdS core / crown nanosheet solution was added dropwise into the container, and silicone oil was added dropwise into the other side of the container to generate surface pressure on the nanosheets. After the n-hexane was completely evaporated, a nanosheet film suspended on the surface of the liquid was obtained. The acetonitrile was slowly discharged, and the self-assembled film was deposited between the electrodes in a face-down manner. The residual acetonitrile was evaporated in a vacuum at room temperature. The above process was repeated to obtain the required number of nanosheet layers.

10. The method of claim 5, wherein the method further comprises: forming a first electrode on the substrate; forming a second electrode on the substrate; and forming a microcavity between the first electrode and the second electrode. The top DBR was deposited above the interdigital electrodes in step 4 by the following steps: After the device with deposited nanosheets was completely dried, the device was placed in a high-vacuum coating machine. High-refractive thin films and low-refractive thin films were alternately deposited by electron beam evaporation in a high-vacuum environment. The deposition temperature was less than 50°C.

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