Electro-optically modulated quantum dot-plasmon strongly coupled device and method of making the same

Abstract

The application discloses a quantum dot-plasmon strong coupling device capable of electro-optical modulation and a preparation method thereof, which comprises a bottom silicon substrate, a silicon dioxide oxidation layer, a lead zirconate titanate film, a metal interdigital electrode and a quantum dot light-emitting layer; the bottom silicon substrate, the silicon dioxide oxidation layer and the lead zirconate titanate film are sequentially arranged from bottom to top; the metal interdigital electrode is arranged in an interdigital grating array groove structure of the lead zirconate titanate film; and the quantum dot light-emitting layer is arranged above a first groove and a second groove of the interdigital grating array groove structure. The quantum dot-plasmon strong coupling device has the following advantages in the modulation performance: the lead zirconate titanate is a relaxor ferroelectric material, the electro-optical coefficient of which is far higher than that of lithium niobate material, nanosecond-level super high-speed response can be realized, and the refractive index of the material can be adjusted in real time to match the quantum dot energy level.

Description

Technical Field

[0001] This invention relates to the fields of optical communication and quantum information, specifically to an electro-optically modulated quantum dot-plasmon strong coupling device and its fabrication method. Background Technology

[0002] In the fields of optical communication and quantum information, the strong coupling system of quantum dots and microcavities is the core foundation for research and applications such as the construction of high-precision quantum light sources and the development of low-threshold lasers. However, the difficulty in real-time control of this strong coupling system has severely restricted the development of quantum technology. Electro-optic modulation technology, with its rapid response and precise control capabilities, has become a key means to overcome this bottleneck. Current mainstream electro-optic modulation technologies all have certain limitations: traditional lithium niobate modulators, although possessing the advantage of low loss, have extremely low electro-optic coefficients, requiring increased device length to achieve effective modulation, resulting in bulky size and high driving voltage, making it difficult to meet chip-level integration requirements; silicon-based modulators rely on plasmon dispersion effects, and although compatible with CMOS processes, they suffer from inherent defects such as low modulation efficiency and high insertion loss, limiting their application in high-speed quantum communication; organic material modulators, while achieving high electro-optic coefficients, suffer from poor long-term stability and cannot meet the requirements of industrial environments. Summary of the Invention

[0003] The purpose of this invention is to provide an electro-optic modulated quantum dot-plasmonic strongly coupled device and its fabrication method, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: An electro-optically modulated quantum dot-plasmon strongly coupled device, comprising: Underlying silicon substrate; A silicon dioxide oxide layer is disposed on the upper end of the bottom silicon substrate; A lead zirconate titanate film is disposed on the upper end of a silicon dioxide oxide layer. A first connecting groove is provided on one side of the upper end of the lead zirconate titanate film, and a plurality of first grooves communicating with the first connecting groove are provided at intervals along the first connecting groove. A second connecting groove is provided on the other side of the upper end of the lead zirconate titanate film, and a plurality of second grooves communicating with the second connecting groove are provided at intervals along the second connecting groove. The first connecting groove and the second connecting groove are arranged opposite to each other, and the first groove and the second groove are arranged alternately. The first connecting groove, the first groove, the second connecting groove, and the second groove constitute an interdigitated grating array groove structure. A metal interdigitated electrode assembly, comprising a first electrode and a second electrode, wherein the first electrode includes a first connecting electrode and a plurality of first insertion electrodes spaced apart on the first connecting electrode, the first connecting electrode being embedded in a first connecting groove, and the first insertion electrodes being correspondingly embedded in first recesses; the second electrode includes a second connecting electrode and a plurality of second insertion electrodes spaced apart on the second connecting electrode, the second connecting electrode being embedded in a second connecting groove, and the second insertion electrodes being correspondingly embedded in second recesses; and A quantum dot light-emitting layer is disposed in the region above the interdigitated grating array groove structure.

[0005] Furthermore, the underlying silicon substrate is an intrinsic silicon substrate material with a thickness of 200-500 μm.

[0006] Furthermore, the thickness of the silicon dioxide oxide layer is 2-5 μm.

[0007] Furthermore, the quantum dot luminescent layer is a colloidal quantum dot material with luminescence wavelengths in the visible and near-infrared bands.

[0008] Furthermore, the interdigitated grating array groove structure adopts a straight waveguide-shaped or sawtooth-shaped grating, the period of the interdigitated grating array groove structure is 500-1000nm, the duty cycle is 20%-80%, and the etching depth is 50-300nm.

[0009] The present invention also provides a method for fabricating a quantum dot-plasmonic strongly coupled device that can be modulated by electro-optics as described above, comprising the following steps: Step 1: Take the bottom silicon substrate and prepare a silicon dioxide oxide layer on the bottom silicon substrate using any one of the following methods: chemical vapor deposition, rapid thermal oxidation, ion implantation, or high temperature and low pressure oxidation. This silicon dioxide layer serves as an insulating layer. Alternatively, an existing silicon-on-silicon oxide substrate material can be used instead, which includes a bottom silicon substrate and a silicon dioxide oxide layer; Step 2: Prepare a lead zirconate titanate film on the silica oxide layer. The lead zirconate titanate film is formed on the top of the silica layer by sol-gel and spin-coating annealing. Step 3: Fabricate an interdigitated grating array groove structure on a lead zirconate titanate thin film; Step 4: Fabricate metal interdigitated electrodes on the groove structure of the interdigitated grating array.

[0010] Step 5: Fabricate a quantum dot light-emitting layer on the groove structure of the interdigitated grating array.

[0011] Further, step 3 includes: First, positive photoresist is spin-coated onto a lead zirconate titanate thin film. Then, the pattern of the interdigitated metal electrode assembly is transferred onto the photoresist using electron beam lithography to form an interdigitated grating array groove structure. After development, the lead zirconate titanate beneath the interdigitated grating array groove structure is exposed. Next, a plasma etching process is used with the photoresist as a mask to etch the lead zirconate titanate material to a depth of 50-300 nm.

[0012] Further, step 4 includes: Metal interdigitated electrode components are grown in the region of the interdigitated grating array groove structure using electron beam evaporation or magnetron sputtering, and finally excess metal and photoresist are removed by stripping.

[0013] Further, step 5 includes: A quantum dot luminescent layer is spin-coated onto the area above the first and second grooves, and then air-dried; alternatively, a solution-dropping method is used, in which an appropriate amount of quantum dot solution is measured with a pipette and dripped onto the area above the first and second grooves to obtain the quantum dot luminescent layer.

[0014] The electro-optic modulation device proposed in this invention modulates the refractive index change of lead zirconate titanate material by energizing the interdigitated metal electrode assembly, thereby controlling the optical properties such as the strong coupling between the interdigitated grating array groove structure and quantum dots. Compared with the prior art, the advantages of this invention are as follows: 1) In terms of process fabrication, lead zirconate titanate thin film modulators can be integrated into subwavelengths and have low cost, making them widely applicable in flexible wearable devices, large-area displays and other fields.

[0015] 2) In terms of modulation performance, lead zirconate titanate, as a relaxor ferroelectric material, has an electro-optic coefficient far exceeding that of lithium niobate, enabling nanosecond-level ultra-high-speed response and real-time adjustment of the material's refractive index to match the quantum dot energy level. Furthermore, the strong coupling effect between quantum dots and surface plasmons can confine the optical field to the subwavelength scale, and its local field enhancement effect can significantly amplify the electro-optic modulation effect.

[0016] 3) In terms of integration characteristics, the device size can be reduced to the micrometer or even nanometer scale, which is more conducive to on-chip integration.

[0017] 4) Through the design of metal micro-nano structures, the electro-optic modulator has a wide coverage of response wavelengths, compatible with quantum dot visible light emission and optical fiber communication bands, overcoming the wavelength limitations of silicon-based modulators.

[0018] Therefore, lead zirconate titanate interdigitated grating electro-optic modulators, with their advantages of high-speed dynamic control, excellent integration capability and wide band applicability, provide an efficient solution for the strong coupling control of quantum dots and optical modes, and lay a solid technical foundation for the construction of ultra-sensitive sensing and on-chip quantum interconnects. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the main structure of the quantum dot-plasmonic strongly coupled device prepared in Example 2.

[0020] Figure 2 This is a top view schematic diagram of the quantum dot-plasmoid strong coupling device prepared in Example 2.

[0021] Figure 3 This is a schematic diagram of the front view of the quantum dot-plasmoid strongly coupled device prepared in Example 2 after removing the metal interdigitated electrode assembly and the quantum dot light-emitting layer.

[0022] Figure 4 This is a top view of the quantum dot-plasmoid strongly coupled device prepared in Example 2 after removing the metal interdigitated electrode assembly and the quantum dot light-emitting layer.

[0023] Figure 5 This is a top view of the quantum dot-plasmoid strongly coupled device prepared in Example 5.

[0024] In the figure: bottom silicon substrate 1, silicon dioxide oxide layer 2, lead zirconate titanate film 3, first connecting groove 300, first recess 301, second connecting groove 302, second recess 303, metal interdigitated electrode assembly 4, first connecting electrode 400, first insertion electrode 401, second connecting electrode 402, second insertion electrode 403, quantum dot light-emitting layer 5. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1: As Figure 1 and Figure 2 As shown, a quantum dot-plasmite strongly coupled device that can be modulated by electro-optics includes: a bottom silicon substrate 1, a silicon dioxide oxide layer 2, a lead zirconate titanate thin film 3, a metal interdigitated electrode 4, and a quantum dot light-emitting layer 5.

[0027] The bottom silicon substrate 1 is an intrinsic silicon substrate material with a thickness of about 200-500μm.

[0028] The silicon dioxide oxide layer 2 is fabricated on the underlying silicon substrate 1 using chemical vapor deposition, rapid thermal oxidation, ion implantation, or high-temperature low-pressure oxidation. The silicon dioxide oxide layer 2 is a 2-5 μm thick silicon dioxide thin film and serves as an insulating layer.

[0029] The lead zirconate titanate thin film 3 is fabricated on top of the silicon dioxide insulating layer 2 using a sol-gel process followed by spin-coating and annealing, with a thickness of 100-500 nm. An interdigitated grating array groove structure 300 is etched onto the lead zirconate titanate thin film 3 using electron beam lithography and plasma etching techniques. A first connecting groove 300 is provided on one side of the upper end of the lead zirconate titanate thin film 3, and several first grooves 301 communicating with the first connecting groove 300 are spaced along the first connecting groove 300. A second connecting groove 302 is provided on the other side of the upper end of the lead zirconate titanate thin film 3, and several second grooves 303 communicating with the second connecting groove 302 are spaced along the second connecting groove 302. The first connecting groove 300 and the second connecting groove 302 are positioned opposite each other, and the first grooves 301 and the second grooves 303 are staggered. The first connecting groove 300, the first groove 301, the second connecting groove 302, and the second groove 303 constitute the interdigitated grating array groove structure.

[0030] The metal interdigitated electrode assembly 4 is formed by growing a metal thin film in the etched grooves of the lead zirconate titanate thin film 3 using electron beam evaporation or magnetron sputtering. The material can be gold, silver, or an aluminum / nickel-tin alloy. The metal interdigitated electrode assembly 4 includes a first electrode and a second electrode. The first electrode includes a first connecting electrode 400 and a plurality of first insertion electrodes 401 spaced apart on the first connecting electrode 400. The first connecting electrode 400 is embedded in a first connecting groove 300, and the first insertion electrodes 401 are correspondingly embedded in the first grooves 301. The second electrode includes a second connecting electrode 402 and a plurality of second insertion electrodes 403 spaced apart on the second connecting electrode 402. The second connecting electrode 402 is embedded in a second connecting groove 302, and the second insertion electrodes 403 are correspondingly embedded in the second grooves 303.

[0031] The quantum dot emitting layer 5 is a colloidal quantum dot material with emission wavelengths in the visible and near-infrared bands. It is a CdTe / ZnSe core / shell structure quantum dot material with emission wavelengths of 605nm, 655nm, or 800nm. High-concentration quantum dots are introduced in the region above the first groove 301 and the second groove 303 by drop-casting or uniform spin-coating, or by dragging the quantum dot solution onto the structure with clean paper or by using a soft probe to pick up the quantum dot solution and dot-coating it onto the structure.

[0032] Example 2: This example provides a method for fabricating a strongly coupled device of a 655nm quantum dot and a straight waveguide interdigitated grating nanocavity based on lead zirconate titanate electro-optic modulation, including the following steps: S1, Preparation of lead zirconate titanate thin film A 4-inch silicon wafer substrate sample with a top silicon dioxide film thickness of 3 μm was used. In other embodiments, a silicon dioxide layer can also be prepared on the bottom silicon substrate using any of the following methods: chemical vapor deposition, rapid thermal oxidation, ion implantation, or high-temperature low-pressure oxidation. A 300 nm thick lead zirconate titanate film 3 was prepared on the substrate using the sol-gel method.

[0033] S2, zoned A photoresist layer was applied over the lead zirconate titanate film as a protective layer, and then the film was diced into 1.4cm x 1.5cm wafers using a dicing machine.

[0034] S3, Cleaning The sample was placed in a basket and sonicated for 15 minutes each in acetone, ethanol, and deionized water, then dried with a nitrogen gun. Finally, it was placed in a plasma degumming machine and cleaned for 2 minutes using an oxygen discharge program.

[0035] S4, Fabrication of the interdigitated grating array groove structure First, a positive photoresist, Zep520A, was spin-coated onto the sample surface at 2000 rpm for 45 seconds, followed by preheating at 180°C for 2 minutes. Then, an electron beam lithography machine was used to transfer a straight waveguide grating and connecting electrode pattern onto the photoresist. The grating is a combination of all the first and second grooves; the straight waveguide grating refers to the first and second grooves with straight inner walls. The connecting electrode pattern consists of the first and second connecting grooves. The sample was then preheated at 120°C for 20 minutes. After cooling, the sample was developed in amyl acetate solution for 70 seconds and fixed with isopropanol for 30 seconds. After photoresist fixing, the lead zirconate titanate film beneath the interdigitated grating array groove structure was exposed. Next, a plasma etching machine was used with the photoresist as a mask to etch the lead zirconate titanate film to a depth of 100 nm. The interdigitated grating array groove structure is a straight waveguide shape with a duty cycle of 1:1 and a period of 655 nm, where the period refers to the spacing between adjacent grooves.

[0036] S5, Electrode fabrication Following the previous step without removing the photoresist mask, the stacked Ge / Au films (20nm / 80nm thick) were sequentially evaporated using electron beam evaporation. They were then immersed in acetone solution and stripped to remove excess metal and photoresist. This left the metal interdigitated electrodes and connecting electrodes in the lead zirconate titanate film grooves.

[0037] S6, Fabrication of quantum dot light-emitting layer Use a pipette to measure a concentration of 1×10 -8One μL of colloidal quantum dot solution of M was dropwise onto the PZT grating region to form the quantum dot emitting layer, which was then allowed to air dry in a fume hood. The quantum dots were an oil-soluble solution with a CdSe / ZnS core-shell structure, and the emission wavelength was 655 nm.

[0038] Example 3: This example provides a method for fabricating a 605nm quantum dot-straight waveguide grating nanocavity strongly coupled device based on lead zirconate titanate material electro-optic modulation. Compared to Example 2, the difference lies in the following: in S4, when fabricating the interdigitated grating array groove structure, the period of the interdigitated grating array groove structure is 605nm, and the duty cycle is 1:1. Also, in S6, when fabricating the quantum dot emitting layer, the quantum dot solution is selected as an oil-soluble solution with a CdSe / ZnS core-shell structure and an emission wavelength of 605nm.

[0039] Example 4: This example provides a method for fabricating an 800nm ​​quantum dot-straight waveguide grating nanocavity strongly coupled device based on PZT material electro-optic modulation. Compared to Example 2, the difference lies in the following: in S4, when fabricating the interdigitated grating array groove structure, the period of the interdigitated grating array groove structure is 800nm, and the duty cycle is 1:1. Also, in S6, when fabricating the quantum dot emitting layer, the quantum dot solution is selected as an oil-soluble solution with a CdSe / ZnS core-shell structure and an emission wavelength of 800nm.

[0040] Examples 5, 6, and 7 are based on Examples 2, 3, and 4, respectively, but replace the straight waveguide-shaped interdigitated grating array groove structure with a sawtooth-shaped interdigitated grating array groove structure. The sawtooth-shaped interdigitated grating array groove structure is characterized in that the inner walls of the first groove and the second groove are sawtooth-shaped.

[0041] Examples 8, 9, 10, 11, 12, and 13, based on Examples 2, 3, 4, 5, 6, and 7, respectively, modify the method of preparing quantum dot layers by dropping a liquid, using a soft probe to pick up 1×10⁻⁶ particles. -9 1 μL of colloidal quantum dot solution of M was dotted onto the region of the interdigitated grating array groove structure to prepare a strongly coupled system of single quantum dots and interdigitated grating array groove structure.

[0042] It should be noted that the pattern and corresponding positional relationships of the above-mentioned underlying silicon substrate, silicon dioxide oxide layer, metal interdigitated electrode assembly, and quantum dot light-emitting layer can be referred to... Figure 1 and Figure 2 The pattern and their corresponding positions of the underlying silicon substrate, silicon dioxide oxide layer, interdigitated metal electrode assembly, and quantum dot light-emitting layer can be found in [reference]. Figure 1 and Figure 3 .

[0043] The principle of the above electro-optic modulator is as follows: To achieve efficient electro-optic modulation of the proposed electro-optic modulation device, the core step lies in polarizing the lead zirconate titanate thin film. During polarization, opposite DC bias voltages are applied to the connecting electrodes at both ends of the interdigital metal electrode assembly, resulting in opposite polarities for adjacent metal gratings (i.e., the first and second interdigital electrodes), thereby constructing a capacitor system with lead zirconate titanate as the dielectric layer. The polarization electric field is a DC field of 15–20 V / μm. Under the influence of the external electric field, the ferroelectric domains within the lead zirconate titanate material align in a specific direction. After dielectric polarization treatment, the lead zirconate titanate thin film achieves an electro-optic coefficient of 200 pm / V.

[0044] After polarization is completed, a modulation electric field in the same direction as the polarization electric field is applied to the lead zirconate titanate electro-optic modulator. The direction of the ferroelectric polarization vector inside the lead zirconate titanate material changes with the applied electric field, causing a change in refractive index. The change in refractive index of the lead zirconate titanate grating (plug-in electrode) array further induces a change in the optical mode of the grating. At this time, by monitoring the reflection spectrum of the grating array with a spectrometer, the shift of the spectral peaks can be clearly observed. When the grating mode is modulated to match the eigenmode of the quantum dot, a strong coupling occurs with the quantum dot, which is a strong interaction between light and matter. In addition to the strong interaction between the lead zirconate titanate grating mode and the quantum dot, this electro-optic modulator also achieves a strong coupling between surface plasmons generated by the plug-in electrodes and the quantum dot. Designing the metal grating as a sawtooth shape can increase the intensity of the local field on the metal surface, greatly enhancing the strong interaction between the quantum dot and the surface plasmons. Therefore, a hybrid state of exciton polaritons and surface plasmon polaritons is formed on the grating surface, improving the strong coupling performance. Measuring the photoluminescence spectrum of quantum dots using a spectrometer can characterize strong coupling phenomena. When Rabi splitting occurs in the fluorescence spectrum, it indicates that the quantum dots and the grating mode have strong coupling, thus providing a key basis for the performance research and optimization of electro-optic modulation devices.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A quantum dot-plasmon strongly coupled device that can be modulated by electro-optics, characterized in that, include: Underlying silicon substrate; A silicon dioxide oxide layer is disposed on the upper end of the bottom silicon substrate; A lead zirconate titanate film is disposed on the upper end of a silicon dioxide oxide layer. A first connecting groove is provided on one side of the upper end of the lead zirconate titanate film, and a plurality of first grooves communicating with the first connecting groove are provided at intervals along the first connecting groove. A second connecting groove is provided on the other side of the upper end of the lead zirconate titanate film, and a plurality of second grooves communicating with the second connecting groove are provided at intervals along the second connecting groove. The first connecting groove and the second connecting groove are arranged opposite to each other, and the first groove and the second groove are arranged alternately. The first connecting groove, the first groove, the second connecting groove, and the second groove constitute an interdigitated grating array groove structure. A metal interdigitated electrode assembly, comprising a first electrode and a second electrode, wherein the first electrode includes a first connecting electrode and a plurality of first insertion electrodes spaced apart on the first connecting electrode, the first connecting electrode being embedded in a first connecting groove, and the first insertion electrodes being correspondingly embedded in first recesses; the second electrode includes a second connecting electrode and a plurality of second insertion electrodes spaced apart on the second connecting electrode, the second connecting electrode being embedded in a second connecting groove, and the second insertion electrodes being correspondingly embedded in second recesses; and A quantum dot light-emitting layer is disposed in the region above the interdigitated grating array groove structure.

2. The electro-optically modulated quantum dot-plasmon strong coupling device according to claim 1, characterized in that, The underlying silicon substrate is an intrinsic silicon substrate material with a thickness of 200-500 μm.

3. The electro-optically modulated quantum dot-plasmon strongly coupled device according to claim 1, characterized in that, The thickness of the silicon dioxide oxide layer is 2-5 μm.

4. The electro-optically modulated quantum dot-plasmon strongly coupled device according to claim 1, characterized in that, The quantum dot luminescent layer is a colloidal quantum dot material with luminescence wavelengths in the visible and near-infrared bands.

5. The electro-optically modulated quantum dot-plasmon strongly coupled device according to claim 1, characterized in that, The interdigitated grating array groove structure adopts a straight waveguide-shaped or sawtooth-shaped grating. The period of the interdigitated grating array groove structure is 500-1000nm, the duty cycle is 20%-80%, and the etching depth is 50-300nm.

6. A method for fabricating a quantum dot-plasmon strongly coupled device that can be modulated by electro-optics as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Take the bottom silicon substrate and prepare a silicon dioxide oxide layer on the bottom silicon substrate using any one of the following methods: chemical vapor deposition, rapid thermal oxidation, ion implantation, or high temperature and low pressure oxidation. This silicon dioxide layer serves as an insulating layer. Alternatively, an existing silicon-on-silicon oxide substrate material can be used instead, which includes a bottom silicon substrate and a silicon dioxide oxide layer; Step 2: Prepare a lead zirconate titanate film on the silica oxide layer. The lead zirconate titanate film is formed on the top of the silica layer by sol-gel and spin-coating annealing. Step 3: Fabricate an interdigitated grating array groove structure on a lead zirconate titanate thin film; Step 4: Fabricate metal interdigitated electrodes on the interdigitated grating array groove structure; Step 5: Fabricate a quantum dot light-emitting layer on the groove structure of the interdigitated grating array.

7. The preparation method according to claim 6, characterized in that, Step 3 includes: First, positive photoresist is spin-coated onto a lead zirconate titanate thin film. Then, the pattern of the interdigitated metal electrode assembly is transferred onto the photoresist using electron beam lithography to form an interdigitated grating array groove structure. After development, the lead zirconate titanate beneath the interdigitated grating array groove structure is exposed. Next, a plasma etching process is used with the photoresist as a mask to etch the lead zirconate titanate material to a depth of 50-300 nm.

8. The preparation method according to claim 6, characterized in that, Step 4 includes: Metal interdigitated electrode components are grown in the region of the interdigitated grating array groove structure using electron beam evaporation or magnetron sputtering, and finally excess metal and photoresist are removed by stripping.

9. The preparation method according to claim 6, characterized in that, Step 5 includes: A quantum dot luminescent layer is spin-coated onto the area above the first and second grooves, and then air-dried; alternatively, a solution-dropping method is used, in which an appropriate amount of quantum dot solution is measured with a pipette and dripped onto the area above the first and second grooves to obtain the quantum dot luminescent layer.

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