Tunable array waveguide grating router based on graphene and silicon waveguide and preparation method thereof

Abstract

The invention provides a tunable array waveguide grating router based on graphene and silicon waveguides and a preparation method, and relates to the technical field of optical elements, and the middle part of the array waveguide in each silicon waveguide in the router in the length direction is provided with a target area so as to form a target waveguide beam together; the graphene layer covers the target waveguide beam and is sequentially divided into covering layers in the length direction, each covering layer covers the corresponding target area in a one-to-one mode, and the electrodes are connected with the graphene layer and the silicon dioxide substrate so that the effective refractive index of the target waveguide beam can be changed by adjusting the voltage value applied to the graphene layer from the electrodes. And the phase difference between the adjacent array waveguides is further changed. Tunability of the central wavelength and the channel bandwidth can be achieved, the tuning range can be effectively widened, the broadband and wavelength irrelevant characteristic is achieved, the tuning time can be reduced to the picosecond level, and the sensitivity to high temperature can be effectively reduced.

Description

Technical Field

[0001] The present application relates to the technical field of optical elements, and in particular to a tunable array waveguide grating router based on graphene and silicon waveguide and a preparation method thereof. Background Art

[0002] In recent years, thanks to the significant progress in technologies such as artificial intelligence, data centers, cloud computing, and blockchain, data traffic has shown an accelerating upward trend, and communication technology is also undergoing a renewal process. As a key networking device for large-capacity data center optical switching networks, the reconfigurable capability of arrayed waveguide grating routers (AWGR) has become a key research and development target in academia and communication equipment manufacturers in technology research. Tunable AWGR plays an important role in data center optical switching networks. By adjusting the optical properties of arrayed waveguide grating routers, such as the effective refractive index of the waveguide, tunable arrayed waveguide grating routers can enable optical signals to switch and adjust between different frequencies or wavelengths, thereby achieving flexible optical transmission and signal processing to meet the network's burst traffic switching needs.

[0003] Although there are several technologies that can achieve the tunability of arrayed waveguide grating routers, current tunable optical waveguide devices often have limitations in response speed, tuning range and temperature sensitivity, which do not meet the needs of high-speed burst and large-capacity optical switching networks in data centers. The response time of common lithium niobate electro-optical tunable optical waveguide devices is mostly in the nanosecond (ns) to sub-nanosecond (sub-ns) level, and the response time of polymer thermo-optical tunable optical waveguide devices depends on the heating element and waveguide structure, usually in the microsecond (μs) to millisecond (ms) level. For common tunable optical waveguide devices, such as thermo-optical tunable optical devices, temperature changes will have a significant impact on the working performance of the device. Temperature changes can cause the characteristics of the device to drift, thereby affecting the tuning range and tuning efficiency, so precise temperature control is often required to maintain performance. In addition, the tuning range of thermo-optical tunable devices is limited by the heat diffusion effect, resulting in the inability to achieve a wide range of optical frequency tuning.

[0004] Therefore, there is an urgent need to design a tunable array waveguide grating router that can increase the tuning range and reduce high temperature sensitivity. Summary of the invention

[0005] In view of this, the embodiments of the present application provide a tunable array waveguide grating router based on graphene and silicon waveguide and a preparation method to eliminate or improve one or more defects existing in the prior art.

[0006] One aspect of the present application provides a tunable array waveguide grating router based on graphene and silicon waveguide, comprising: a silicon dioxide substrate, a plurality of silicon waveguides, a graphene layer and a metal electrode; Each of the silicon waveguides is sequentially arranged on the silicon dioxide substrate; and each of the silicon waveguides includes an input waveguide, an array waveguide and an output waveguide which are sequentially divided along the length direction thereof, and a free transmission region is formed between the input waveguide and the array waveguide in each of the silicon waveguides, and a free transmission region is also formed between the array waveguide and the output waveguide in each of the silicon waveguides; The middle part of each array waveguide in the length direction is divided into a target area, and each target area is parallel to each other and increases in specific length in sequence, and together constitutes a target waveguide bundle; The graphene layer covers the target waveguide bundle, and the graphene layer is sequentially divided into covering layers having the same number and length as the silicon waveguides in the target area along the extension direction, so that each covering layer covers each target area one-to-one; One of the metal electrodes is connected to the graphene layer, and the other metal electrode is connected to an area on the silicon dioxide substrate not covered by the graphene layer, so as to change the effective refractive index of the target waveguide beam by adjusting the voltage value applied from the metal electrode to the graphene layer, thereby changing the phase difference between adjacent array waveguides.

[0007] In some embodiments of the present application, an electrically insulating transition layer is provided between the graphene layer and the target waveguide bundle.

[0008] In some embodiments of the present application, the refractive index of the electrically insulating material constituting the electrically insulating transition layer is between the refractive index of the graphene and the refractive index of silicon.

[0009] In some embodiments of the present application, the graphene layer includes: one graphene material layer or a plurality of graphene material layers stacked in sequence.

[0010] In some embodiments of the present application, the length direction of each of the metal electrodes is parallel to the length direction of the target area.

[0011] In some embodiments of the present application, each of the target areas in the target waveguide beam is equally divided into two adjacent groups, one of which is a first adjustment area and the other is a second adjustment area, and then the voltage value applied from the metal electrode to each of the covering layers covering the first adjustment area is adjusted to increase the effective refractive index of the first adjustment area; and the voltage value applied from the metal electrode to each of the covering layers covering the second adjustment area is adjusted to reduce the effective refractive index of the second adjustment area, so as to achieve channel bandwidth tuning of the tunable array waveguide grating router.

[0012] Another aspect of the present application provides a method for preparing a tunable array waveguide grating router based on graphene and silicon waveguide, comprising: Prepare the silicon dioxide substrate, the silicon waveguides sequentially disposed on the silicon dioxide substrate, and an electrical insulating transition layer on the target area in each silicon waveguide; The graphene layer is prepared and covered on the target waveguide bundle with the graphene layer, one of the metal electrodes is connected to the graphene layer, and another of the metal electrodes is connected to the area on the silicon dioxide substrate not covered by the graphene layer, so as to obtain a tunable array waveguide grating router based on graphene and silicon waveguide.

[0013] In some embodiments of the present application, the method for preparing the tunable array waveguide grating router based on graphene and silicon waveguide further includes: The operating parameters of the prepared tunable array waveguide grating router based on graphene and silicon waveguide are tested, wherein the operating parameters include: insertion loss, crosstalk, and tunable range of wavelength and bandwidth.

[0014] In some embodiments of the present application, the step of preparing the silicon dioxide substrate, sequentially disposing the silicon waveguides on the silicon dioxide substrate, and the electrically insulating transition layer on the target region in each silicon waveguide comprises: The preset optical waveguide design architecture of the tunable array waveguide grating router based on graphene and silicon waveguide is etched on a silicon wafer on an insulating substrate by using photolithography technology; Using the photoresist pattern as a mask, forming each of the silicon waveguides on the silicon wafer by dry or wet etching technology, and performing a planarization process on the silicon waveguide; By thermal oxidation or chemical vapor deposition, an electrically insulating transition layer is formed on the surface of the target area in each of the silicon waveguides to obtain the silicon dioxide substrate, the silicon waveguides sequentially arranged on the silicon dioxide substrate, and the electrically insulating transition layer on the target area in each of the silicon waveguides.

[0015] In some embodiments of the present application, the graphene layer is prepared, and the graphene layer is covered on the target waveguide bundle, one of the metal electrodes is connected to the graphene layer, and another of the metal electrodes is connected to the area on the silicon dioxide substrate not covered by the graphene layer, so as to obtain a tunable array waveguide grating router based on graphene and silicon waveguide, comprising: A single or multiple graphene material layer is obtained from a bulk crystal material by a mechanical exfoliation method to form the corresponding graphene layer; Determining the crystal quality, surface morphology, crystal composition and crystal phase information of the graphene material layer; Using graphene transfer technology to cover the graphene layer on the target waveguide bundle; performing heat treatment and nano-machining on the graphene layer covering and the target waveguide bundle; One of the metal electrodes is connected to the graphene layer, another of the metal electrodes is connected to a region on the silicon dioxide substrate that is not covered by the graphene layer, and the metal electrodes are electrically connected to an external circuit.

[0016] The present application provides a tunable array waveguide grating router based on graphene and silicon waveguide, comprising: a silicon dioxide substrate, a plurality of silicon waveguides, a graphene layer and a metal electrode; each of the silicon waveguides is sequentially arranged on the silicon dioxide substrate; each of the silicon waveguides comprises an input waveguide, an array waveguide and an output waveguide sequentially divided along its length direction, and a free transmission area is formed between the input waveguide and the array waveguide in each of the silicon waveguides, and a free transmission area is also formed between the array waveguide and the output waveguide in each of the silicon waveguides; a target area is divided in the middle of the length direction of each of the array waveguides, and each of the target areas is parallel to each other, the lengths of which increase sequentially, and together form a target waveguide beam; the graphene layer The target waveguide beam is covered, and the graphene layer is divided into covering layers of the same number and length as the silicon waveguides of the target waveguide beam in sequence along the extension direction, so that each covering layer covers each target area one-to-one; each covering layer and silicon waveguide are respectively connected to the two ends of the corresponding metal electrode, so as to change the effective refractive index of the target waveguide beam by adjusting the voltage value applied from the metal electrode to the graphene layer, thereby changing the phase difference between adjacent array waveguides, thereby realizing the tunability of the central wavelength and the channel bandwidth, effectively improving the tuning range, having the characteristics of broadband independence from wavelength, reducing the tuning time to picosecond level, and effectively reducing the sensitivity to high temperature.

[0017] Additional advantages, purposes, and features of the present application will be partially described in the following description, and will become partially apparent to those skilled in the art after studying the following, or may be learned from the practice of the present application. The purposes and other advantages of the present application can be achieved and obtained by the structures specifically pointed out in the specification and the drawings.

[0018] Those skilled in the art will understand that the purposes and advantages that can be achieved by the present application are not limited to the above specific description, and the above and other purposes that can be achieved by the present application will be more clearly understood based on the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present application, constitute a part of the present application, and do not constitute a limitation of the present application. The components in the drawings are not drawn to scale, but are only for the purpose of illustrating the principles of the present application. In order to facilitate the illustration and description of some parts of the present application, the corresponding parts in the drawings may be enlarged, that is, they may become larger relative to other components in the exemplary device actually manufactured according to the present application. In the drawings: Figure 1 Schematic diagram of the relationship between the effective refractive index of graphene and silicon waveguide and the chemical potential of graphene.

[0020] Figure 2 Schematic diagram of the structure of a tunable array waveguide grating router based on graphene and silicon waveguide in one embodiment of the present application.

[0021] Figure 3 A schematic cross-sectional view of a tunable array waveguide grating router based on graphene and silicon waveguide in one embodiment of the present application.

[0022] Figure 4 A schematic diagram of the operation principle of a tunable array waveguide grating router based on graphene and silicon waveguide provided in one embodiment of the present application.

[0023] Figure 5 Schematic diagram of the three-dimensional structure of the target area and the covering layer in a tunable array waveguide grating router based on graphene and silicon waveguide in one embodiment of the present application.

[0024] Figure 6 Schematic diagram of a second cross-section of a tunable array waveguide grating router based on graphene and silicon waveguide in one embodiment of the present application.

[0025] Figure 7 Schematic diagram of a first adjustment region and a second adjustment region in a tunable array waveguide grating router based on graphene and silicon waveguide in one embodiment of the present application.

[0026] Figure 8 It is a schematic flow chart of a method for preparing a tunable array waveguide grating router based on graphene and silicon waveguide in one embodiment of the present application.

[0027] Fig. 9 1 is a flow chart of step 100 in a method for preparing a tunable array waveguide grating router based on graphene and silicon waveguide in an embodiment of the present application.

[0028] Fig.10 2 is a flow chart of step 200 in a method for preparing a tunable array waveguide grating router based on graphene and silicon waveguide in an embodiment of the present application.

[0029] The figures in the attached drawings are as follows: 1. Silicon dioxide substrate; 2. Silicon waveguide; 21. Input waveguide; 22. Arrayed waveguide; 221. Target area; 23. Output waveguide; 24. Free transmission area; 3. Electrical insulation transition layer; 4. Graphene layer; 41. Covering layer; 5. Metal electrode; 6. Target waveguide beam; 7. The first adjustment area; 8. The second adjustment area. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the implementation modes and the accompanying drawings. Here, the illustrative implementation modes and descriptions of the present application are used to explain the present application, but are not intended to limit the present application.

[0031] It should also be noted here that in order to avoid obscuring the present application due to unnecessary details, only the structures and / or processing steps closely related to the scheme according to the present application are shown in the accompanying drawings, while other details that are not very relevant to the present application are omitted.

[0032] It should be emphasized that the term “include / comprises” when used herein refers to the presence of features, elements, steps or components, but does not exclude the presence or addition of one or more other features, elements, steps or components.

[0033] It should also be noted that, unless otherwise specified, the term “connection” herein may refer not only to a direct connection but also to an indirect connection with an intermediate.

[0034] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

[0035] At present, the common tunable AWGR schemes mainly include thermally tuned optical devices and electro-optically tuned optical devices. Thermally tuned optical devices can change the refractive index or structure of materials by heating or cooling the materials, thereby leading to the tuning of wavelength or frequency. Common tuning materials include titanium nitride (TiN) heating silicon waveguides, liquid crystal materials, etc. Electrically tuned optical devices can change the absorption characteristics of semiconductor materials by adjusting the electric field strength, thereby adjusting the transmitted light intensity. Common materials include lithium niobate films. Some scholars have studied a thermally tuned silicon-based AWG device based on the TiN heating principle, and the channel tunable bandwidth reaches 600GHz. Other scholars have proposed a thermo-optical effect tunable AWG device based on a silicon platform on an insulating substrate (SOI), the maximum insertion loss of which is 3.9dB and the channel crosstalk is about 16dB. Some scholars have studied an AWG electro-optically tunable device based on a lithium niobate platform, with a central wavelength tunable range of 2nm.

[0036] In order to solve the problems of small tuning range and high high temperature sensitivity of the existing tunable array waveguide grating routers, the embodiments of the present application respectively provide a tunable array waveguide grating router based on graphene and silicon waveguide and a preparation method of a tunable array waveguide grating router based on graphene and silicon waveguide, which can realize the array waveguide grating router, improve the tuning range of the tunable array waveguide grating router and reduce the high temperature sensitivity.

[0037] Since the discovery of graphene, research on two-dimensional materials has emerged in an endless stream in the past two decades. In recent years, with the maturity and development of silicon-based optical devices, researchers in the field of optics have begun to try to realize more possibilities of optical devices by combining two-dimensional materials with silicon waveguide platforms. Some scholars have proposed an electro-optic modulator based on graphene combined with silicon. Since then, some scholars have elaborated on the theoretical calculation method of the surface dielectric constant of graphene, laying the foundation for theoretical research on graphene and silicon waveguides, making the research on graphene and silicon waveguide devices a hot topic in the field of integrated optics. In recent years, optical modulators, optical switches, microrings and other optoelectronic devices based on two-dimensional materials such as graphene have emerged. However, there has been no research on applying the structure of graphene and silicon waveguides to arrayed waveguide grating routers. The main research difficulties are: first, tuning arrayed waveguide grating routers requires arrayed waveguides to have a large tuning range to meet the needs of communication systems, but the more mature high-quality graphene previously was made by mechanical peeling, and the maximum size was mostly at the micron level, making it difficult to prepare large-size graphene to achieve large-range tuning of AWGR. With the development of graphene preparation technology, studies have proposed and prepared wafer-scale graphene, making graphene-based tunable AWGR feasible. Secondly, due to the size limitation of the device (millimeter level), it is difficult to perform three-dimensional numerical simulation of the graphene-based tunable AWGR. Therefore, this application proposes a segmented simulation scheme, and superimposes the simulation results of each segment in sequence through theoretical calculation, so as to achieve more accurate numerical simulation and verify the rationality and feasibility of the proposed scheme.

[0038] In order to improve and solve the problems existing in the above-mentioned prior art, this application takes graphene and silicon waveguide as platforms and proposes a design scheme for a tunable array waveguide grating router based on graphene and silicon waveguide. Silicon waveguides will include general planar light waveguide (PLC) platforms such as SOI, silicon dioxide on silicon, and silicon nitride. By applying electrodes on both sides of graphene to adjust the chemical potential of graphene itself, the effective refractive index of the composite structure of graphene and silicon waveguide is changed, thereby realizing the tunable function of the center wavelength and channel bandwidth of the array waveguide grating router. Due to the extremely high carrier mobility and strong photoelectric response characteristics of graphene, the device has broadband wavelength-independent characteristics, can achieve tuning time down to picoseconds, and has a high degree of temperature insensitivity.

[0039] The details are described in detail through the following examples.

[0040] First, graphene is a two-dimensional crystalline material that is stable at room temperature. Graphene has special photoelectric regulation properties, and its optical properties can be adjusted by applying an external electric field. In the common communication band of 1550nm wavelength, when the chemical potential of graphene increases from 0eV to 1eV, its effective refractive index will change, which makes the equivalent refractive index of graphene and silicon waveguide structure also have corresponding tunable characteristics, such as Figure 1 As shown. It also means that the phase of the optical signal can be changed in a controllable manner, making graphene and silicon waveguide structures one of the best candidate platforms for tunable optical devices. This is the key theoretical basis for the design of tunable array waveguide grating routers. Figure 1 In the figure, the horizontal axis represents the chemical potential of graphene. (Chemical potential), the unit is electron volt (eV), the ordinate is the equivalent refractive index of graphene and silicon waveguide structure, Figure 1 The solid and dashed lines represent the real part of the equivalent refractive index Re (n eff ) and the imaginary part Im(n eff ).

[0041] Based on this, the embodiment of the present application provides a tunable array waveguide grating router based on graphene and silicon waveguide, see Figure 2 , Figure 3 and Figure 4 ,in, Figure 2 and Figure 4 The number of silicon waveguides 2 is only for illustration. In actual applications, the number will be set according to actual application requirements. The tunable array waveguide grating router based on graphene and silicon waveguide specifically includes the following contents: Silicon dioxide substrate 1, multiple silicon waveguides 2, graphene layer 4 and metal electrodes 5.

[0042] Each of the silicon waveguides 2 is sequentially arranged on the silicon dioxide substrate 1; and each of the silicon waveguides 2 includes an input waveguide 21, an array waveguide 22 and an output waveguide 23 which are sequentially divided along the length direction thereof, and a free transmission region 24 is formed between the input waveguide 21 and the array waveguide 22 in each of the silicon waveguides 2, and a free transmission region 24 is also formed between the array waveguide 22 and the output waveguide 23 in each of the silicon waveguides 2.

[0043] The middle part of each arrayed waveguide 22 in the length direction is divided into a target area 221, and each of the target areas 221 is parallel to each other and together constitutes a target waveguide bundle 6, wherein the length of the target area increases successively and the change amount is the same. Among them, the arrayed waveguide is not necessarily fan-shaped. In a design example of the present application, each of the arrayed waveguides 22 can be parallel in the middle and arc-shaped on both sides; other different shapes such as a saddle shape are also possible.

[0044] Each of the covering layers 41 completely overlaps with the target area 221 .

[0045] One of the two metal electrodes 5 is connected to the graphene layer 4, and the other is connected to the silicon dioxide substrate 1 not covered with graphene; Figure 3 The graphene inside is not connected, it only exists above the waveguide, and there are some on the sides and both sides, but they are not connected. There is a certain distance in the middle that is not covered by graphene, and the silicon dioxide substrate 1 is exposed. The exposed silicon dioxide substrate 1 is used to place another electrode. By adjusting the voltage value applied from the metal electrode 5 to the graphene layer 4, the effective refractive index of the target waveguide beam 6 is changed, thereby changing the phase difference between the adjacent array waveguides 22.

[0046] See also Figure 4 When the multi-wavelength signal is transmitted to the tunable array waveguide grating router based on graphene and silicon waveguide via the input waveguide 21, it will first be diffracted in the free propagation area, and the obtained diffraction signal will be independently propagated after reaching each array waveguide 22. Since there is a stable length difference between adjacent array waveguides 22, and a stable and adjustable optical path difference is generated under the action of voltage, for a certain specific wavelength, the diffraction signal in each array waveguide 22 will have a stable and adjustable phase difference, and then through interference in the free propagation area, an alternating light and dark interference enhancement position or interference cancellation position is formed. At the same time, due to the different phase differences of different wavelengths, interference maxima will be formed at different positions, so that the multi-wavelength signals are output separately through the output waveguides 23 at different positions, and the output position of a specific wavelength can be adjusted.

[0047] Specifically, the embodiment of the present application combines graphene and silicon-based waveguides to form a graphene and silicon waveguide 2 architecture, changes the chemical potential of graphene by means of electrodes arranged on the graphene, adjusts the effective refractive index of the graphene and silicon waveguide 2, and thereby realizes the tuning function of the array waveguide 22 grating router (hereinafter referred to as AWGR device).

[0048] In a specific example, in order to precisely tune the output position of different wavelengths, see Figure 5, the silicon dioxide substrate 1 is a silicon waveguide 2 structure, wherein the typical width of the silicon waveguide 2 is 500nm, and the typical height of the silicon waveguide 2 is 220nm. The typical width and typical height are the most commonly used width and height parameters of SOI waveguides (i.e. silicon waveguides on insulators), and can also be adjusted appropriately. The approximate adjustment range should be 400-650nm for width and 180-240nm for height.

[0049] In the embodiment of the present application, the graphene layer 4 is a key part for realizing the tunability of the AWGR device.

[0050] Metal electrodes 5 (such as gold) are placed on the outermost sides of the graphene layer 4 so that the graphene layer 4 can be directly affected by applying voltage through the electrodes.

[0051] By adjusting the applied voltage of the graphene and silicon waveguide 2 structure, the effective refractive index of the silicon waveguide 2 (i.e., the target waveguide beam 6) covered with the graphene portion is changed, thereby changing the phase difference between adjacent array waveguides 22, which will lead to the movement of the position of the interference enhancement maximum value formed after the interference in the free propagation region, thereby realizing the tunable function of the AWGR device. The principle of the related grating interference equation can be expressed as: (1-1) In the above formula (1-1), n s is the effective refractive index of the wavelength λ in the free propagation region waveguide, d is the spacing between each input waveguide 21, and the spacing between each output waveguide 23, θ in is the angle between adjacent input waveguides 21, θ out is the angle between adjacent output waveguides 23, It represents the length difference introduced by the different angles of adjacent input waveguides. It represents the length difference introduced by the different angles of adjacent output waveguides, n c0 is the effective refractive index of the waveguides with wavelength λ in the input waveguide 21, the output waveguide 23 and the arrayed waveguide 22 except the target area 221, Δl0 is the length difference between adjacent waveguides in each adjacent arrayed waveguide 22 except the target area 221, n c_graphene is the effective refractive index of wavelength λ at the graphene and silicon waveguide 2 (i.e., the target waveguide beam 6), Figure 4 The triangular area in is the area where the graphene layer 4 covers the target waveguide beam 6. g is the length difference between the graphene (and the target area 221 ) covered in adjacent array waveguides 22 , m is the waveguide diffraction order of the AWGR device, and λ represents the central wavelength of the device.

[0052] From the above grating interference equation, we can know that when the chemical potential of graphene changes, that is, nc_graphene As a result, the central wavelength λ of the device shifts, and the shift range It can be expressed as: (1-2) In the above formula (1-2), n c2 and n c1 They are the effective refractive indices of graphene and silicon waveguide 2 (i.e., target waveguide beam 6) before and after the chemical potential is changed, respectively.

[0053] From the above description, it can be seen that the tunable array waveguide grating router based on graphene and silicon waveguide provided in the embodiment of the present application can realize the tunability of the central wavelength and the channel bandwidth, can effectively improve the tuning range, has the characteristics of broadband and wavelength independence, can reduce the tuning time to the picosecond level, and can effectively reduce the sensitivity to high temperature.

[0054] In order to effectively prevent the current from flowing directly from the graphene into the silicon waveguide 2, in a tunable array waveguide grating router based on graphene and silicon waveguide provided in an embodiment of the present application, see Figure 6 An electrical insulating transition layer 3 is provided between the graphene layer 4 and the target waveguide bundle 6, but the electrical insulating transition layers 3 are not interconnected. They are only provided above the waveguide, and there are some on the sides and sides, but they are not connected. There is a certain distance in the middle, which will cause the silicon dioxide substrate in the middle groove to leak out.

[0055] That is to say, an electrically insulating transition layer 3 can be provided between the graphene layer 4 and the silicon waveguide. The electrically insulating transition layer 3 can specifically be made of an electrically insulating material with a thickness of 7 nm, which can effectively prevent current from flowing directly from the graphene into the silicon waveguide 2, thereby maintaining the electrical properties of the graphene and ensuring the effect of voltage application.

[0056] In order to further improve the propagation characteristics of light waves in the composite structure of graphene and silicon waveguide 2, in a tunable array waveguide grating router based on graphene and silicon waveguide provided in an embodiment of the present application, the refractive index of the electrically insulating material constituting the electrically insulating transition layer 3 is between the refractive index of the graphene and the refractive index of silicon.

[0057] In a specific implementation, the electrically insulating material of the electrically insulating transition layer 3 can be aluminum oxide Al2O3, and the refractive index of Al2O3 is between the refractive index of graphene and the refractive index of silicon. As a transition layer, it optimizes the optical coupling between graphene and the silicon waveguide 2, and further improves the propagation characteristics of light waves in the composite structure of graphene and silicon waveguide 2.

[0058] In order to further improve the application reliability and effectiveness of the graphene layer 4, in a tunable array waveguide grating router based on graphene and silicon waveguide provided in an embodiment of the present application, the graphene layer 4 includes: a graphene material layer or a plurality of graphene material layers stacked in sequence.

[0059] Specifically, one or more layers of two-dimensional graphene material may be disposed on top of Al2O3.

[0060] In order to further reduce the lateral coupling between the metal electrodes 5, in a tunable array waveguide grating router based on graphene and silicon waveguide provided in an embodiment of the present application, the length direction of each metal electrode 5 is parallel to the length direction of the target area 221. That is, each metal electrode 5 can be perpendicular to the width direction of the device, thereby reducing the lateral coupling between the electrodes, which will effectively reduce the adverse effects of parasitic capacitance on the tunable AWGR device in high-speed applications that need to achieve hundreds of Gbps.

[0061] In order to achieve channel bandwidth tuning, in a tunable array waveguide grating router based on graphene and silicon waveguide provided in an embodiment of the present application, see Figure 7 , each of the target areas 221 in the target waveguide bundle 6 is equally divided into two adjacent groups, one of which is the first adjustment area 7, and the other is the second adjustment area 8, and then the voltage value applied from the metal electrode 5 to each of the covering layers 41 covering the first adjustment area 7 is adjusted to increase the effective refractive index of the first adjustment area 7; and the voltage value applied from the metal electrode 5 to each of the covering layers 41 covering the second adjustment area 8 is adjusted to reduce the effective refractive index of the second adjustment area 8, so as to achieve channel bandwidth tuning of the tunable array waveguide grating router.

[0062] Specifically, when the array waveguide 22 is equally divided into two upper and lower regions, the first adjustment region 7 and the second adjustment region 8 each cover half of the number of AWGR array waveguides 22. The voltages applied to the first adjustment region 7 and the second adjustment region 8 are adjusted respectively to increase the effective refractive index of the first adjustment region 7 and decrease the effective refractive index of the second adjustment region 8. According to formula (1-2), this will cause the output center wavelength corresponding to the array waveguide 22 of the first adjustment region 7 to increase and the output center wavelength corresponding to the array waveguide 22 of the second adjustment region 8 to decrease, thereby achieving channel bandwidth tuning. The corresponding channel bandwidth tuning range is It is expressed as: (1-3) In formula (1-3), n c3 and n c2 are the effective refractive index of the graphene-silicon waveguide in region A and region B after the chemical potential changes, nc1 is the effective refractive index of the graphene-silicon waveguide before the chemical potential changes, Δl g is the length difference between the graphene (and target area 221) covered in each adjacent array waveguide 22, and m is the waveguide diffraction order of the AWGR device. The effective refractive index of graphene under different chemical potentials is brought into the above formula (1-3) of the AWGR device for calculation, and a preliminary design scheme of the tunable AWGR device can be obtained.

[0063] Based on the tunable array waveguide grating router based on graphene and silicon waveguide in the above embodiment, the present application also provides a method for preparing a tunable array waveguide grating router based on graphene and silicon waveguide, see Figure 8 The method for preparing the tunable array waveguide grating router based on graphene and silicon waveguide specifically includes the following contents: Step 100: preparing the silicon dioxide substrate, the silicon waveguides sequentially disposed on the silicon dioxide substrate, and an electrical insulating transition layer on the target region in each silicon waveguide.

[0064] Step 200: Prepare the graphene layer and cover the target waveguide bundle with the graphene layer, and respectively set the metal electrodes in the length direction of each of the covering layers and on the silicon dioxide substrate waveguide to obtain a tunable array waveguide grating router based on graphene and silicon waveguide.

[0065] On this basis, in order to further improve the application reliability of the tunable array waveguide grating router based on graphene and silicon waveguide, the preparation method of the tunable array waveguide grating router based on graphene and silicon waveguide of the present application further specifically includes step 300 after step 200: testing the operating parameters of the prepared tunable array waveguide grating router based on graphene and silicon waveguide, wherein the operating parameters include: insertion loss, crosstalk, and tunable range of wavelength and bandwidth.

[0066] Specifically, the prepared tunable AWGR device was tested to test the device's central wavelength and bandwidth tunable range. The test platform used a SantecTSL-570 1480-1640nm type c tunable laser, coupled the AWGR device with the optical fiber through the Dediwei Industry S60-05M high-precision six-axis displacement platform, and tested the AWGR output spectrum through an Agilent spectrometer to obtain the device's insertion loss, crosstalk, wavelength and bandwidth tunable range and other parameters.

[0067] In a specific implementation, see Fig. 9 , step 100 in the method for preparing a tunable array waveguide grating router based on graphene and silicon waveguide specifically includes the following contents: Step 110: Use photolithography technology to pattern the preset optical waveguide design architecture of the tunable array waveguide grating router based on graphene and silicon waveguide on a silicon on insulating substrate (SOI) wafer.

[0068] Step 120: using the photoresist pattern as a mask, forming each of the silicon waveguides on the silicon (SOI) wafer by dry or wet etching technology, and planarizing the silicon waveguides.

[0069] Step 130: Form an electrically insulating transition layer on the surface of the target area in each of the silicon waveguides by thermal oxidation or chemical vapor deposition to obtain the silicon dioxide substrate, the silicon waveguides sequentially arranged on the silicon dioxide substrate, and the electrically insulating transition layer on the target area in each of the silicon waveguides.

[0070] Specifically, first select an SOI wafer, which is usually a silicon-insulator-silicon structure. This substrate structure will be used to make optical waveguides. The second step is to define the optical waveguide, and use photolithography technology to define the optical waveguide design pattern on SOI. The process includes making a mask on the SOI wafer and coating it with photoresist, and then forming an optical mode pattern by exposing and developing the optical waveguide template. The next step is etching, using the photoresist pattern as a mask, removing the top silicon that is not protected by the photoresist through dry methods (such as reactive ion etching, RIE) or wet etching technology, removing the non-required areas of the optical waveguide pattern, and then using chemical solvents or plasma treatment to remove the remaining photoresist, thereby forming an optical waveguide structure. In addition, it is necessary to form an electrically insulating transition layer on the surface of the waveguide by thermal oxidation or chemical vapor deposition (CVD). In addition, it also includes planarization treatments such as chemical mechanical polishing (CMP) of silicon waveguides, thereby enhancing the bonding process at the junction of graphene and silicon waveguides and reducing the generation of holes and defects.

[0071] In a specific implementation, see Fig.10 , step 200 in the method for preparing a tunable array waveguide grating router based on graphene and silicon waveguide specifically includes the following contents: Step 210: using a mechanical exfoliation method to obtain a single layer or multiple layers of graphene material from a bulk crystalline material to form the corresponding graphene layer.

[0072] Step 220: Determine the crystal quality, surface morphology, crystal composition and crystal phase information of the graphene material layer.

[0073] Step 230: Using graphene transfer technology to cover the target waveguide bundle with the graphene layer.

[0074] Step 240: thermally treat and nano-process the graphene layer covering and the target waveguide bundle.

[0075] Step 250: Arrange the metal electrodes in the graphene material layer in the length direction of each of the cover layers and on the silicon dioxide substrate in the middle of the array waveguide, and electrically connect the metal electrodes to an external circuit.

[0076] That is, one of the metal electrodes is connected to the graphene layer, and the other metal electrode is connected to a region on the silicon dioxide substrate that is not covered by the graphene layer.

[0077] Specifically, a mechanical exfoliation method is used to obtain a single layer or a few layers of high-quality two-dimensional crystalline graphene from a bulk crystalline material. Secondly, the obtained two-dimensional material is characterized to obtain information such as crystal quality, surface morphology, crystal composition, and crystal phase. Characterization techniques will include optical microscopy, atomic force microscopy (AFM), Raman spectroscopy (Raman), photoluminescence spectroscopy (PL), etc. When using atomic force microscopy for characterization, multiple test parameters are adjusted and appropriate working modes such as contact mode, tapping mode, and conductive mode are selected. Third, graphene transfer technology is used to achieve the combination of two-dimensional graphene and silicon waveguides. Including: polymethyl methacrylate (PMMA) film transfer technology, polydimethylsiloxane / polycarbonate (PDMS / PC) and other auxiliary transfer technologies. In addition, van der Waals heterojunctions can be stacked by all-inorganic transfer technology, especially the relative crystal rotation or twist angle between different atomic layers in the double-layer heterojunction is precisely controlled to form a two-dimensional double-layer graphene heterojunction with special physical properties, thereby improving the optoelectronic properties of graphene to optimize the optical performance of AWGR devices. Fourth, after the graphene is transferred, a large-scale graphene and silicon waveguide composite structure is formed, and heat treatment is performed to enhance the adhesion of graphene to silicon waveguide. Then, the graphene-SOI optical waveguide is nano-processed in a clean room, including electron beam etching (EBL), reactive ion etching (RIE), plasma etching, metal evaporation, molecular layer deposition, etc., to complete the setting of parameters such as the precise position and size of graphene in the graphene and silicon waveguide composite structure in the AWGR device. Fifth, the parameters of the electrode are determined according to the device layout, and photolithography technology is used to coat photoresist, expose, and develop to form an electrode pattern on the graphene, and then the electrode material is deposited and excess metal is removed to form a metal electrode pattern. The electrode and the external circuit are connected through connection and packaging, and good electrical contact is ensured.

[0078] In one or more embodiments of the present application, the graphene and silicon waveguide structures may be applicable to other two-dimensional materials, such as transition metal dichalcogenides (TMDs), molybdenum disulfide (MoS2), graphene twists, and two-dimensional heterojunction structures.

[0079] The key point of this application is to achieve the tunable function of the central wavelength and bandwidth of the AWGR device through graphene and silicon waveguide. By combining two-dimensional materials such as graphene and silicon waveguide platform, the effective refractive index of the device is adjusted, thereby changing the phase of the signal propagating in the optical waveguide device. By dividing the AWGR array waveguide into two regions, the effective refractive index of the graphene and silicon waveguide in the two regions is adjusted respectively, so as to achieve the tunable bandwidth function of the AWGR device.

[0080] In summary, the present application utilizes graphene and silicon waveguide structures to realize the tunable function of AWGR devices. Compared with the common thermally tuned optical devices realized by TiN heating and the electro-optical tuned optical devices based on the lithium niobate platform, the present application uses electrodes applied on both sides of the graphene to change the chemical potential of the graphene itself to tune the effective refractive index of the graphene and silicon waveguide structure. At room temperature, the carrier mobility of graphene is usually as high as 2×10 5 cm 2 V -1 s -1 , which is dozens of times faster than silicon-based materials, so picosecond tuning time can be achieved, which meets the requirements of high bandwidth and low latency for burst traffic in data centers. At the same time, since the change in the dielectric constant of graphene is independent of the frequency of light, the device can meet the requirements of broadband wavelength independence. In the temperature range of 15K-120K, the graphene carrier mobility can remain basically stable. This makes the AWGR device highly temperature-insensitive. In addition, graphene-based and silicon waveguide devices are compatible with CMOS processes, which will greatly reduce the additional power consumption of the device and is of great significance to the research and development of high-speed micro-nano tunable optical devices.

[0081] It should be understood by those skilled in the art that the exemplary components, systems and devices described in conjunction with the embodiments disclosed herein can be implemented in hardware, software or a combination of the two. Whether it is performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different devices to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application. When implemented in hardware, it can be, for example, an electronic circuit, an application-specific integrated circuit (ASIC), appropriate firmware, a plug-in, a function card, etc. When implemented in software, the elements of this application are programs or code segments used to perform the required tasks. The program or code segment can be stored in a machine-readable medium, or transmitted on a transmission medium or a communication link via a data signal carried in a carrier.

[0082] It should be clear that the present application is not limited to the specific configurations and processes described above and shown in the figures. For the sake of simplicity, a detailed description of known devices is omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the device process of the present application is not limited to the specific steps described and shown, and those skilled in the art can make various changes, modifications and additions, or change the order between the steps after understanding the spirit of the present application.

[0083] In the present application, features described and / or illustrated for one embodiment may be used in the same manner or in a similar manner in one or more other embodiments, and / or combined with features of other embodiments or replace features of other embodiments.

[0084] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the embodiments of the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A tunable array waveguide grating router based on graphene and silicon waveguide, characterized in that: include: a silicon dioxide substrate, a plurality of silicon waveguides, a graphene layer, and metal electrodes; Each of the silicon waveguides is sequentially arranged on the silicon dioxide substrate; and each of the silicon waveguides includes an input waveguide, an array waveguide and an output waveguide which are sequentially divided along the length direction thereof, and a free transmission region is formed between the input waveguide and the array waveguide in each of the silicon waveguides, and a free transmission region is also formed between the array waveguide and the output waveguide in each of the silicon waveguides; The middle part of each array waveguide in the length direction is divided into a target area, and each target area is parallel to each other and together constitutes a target waveguide bundle; The graphene layer covers the target waveguide bundle, and the graphene layer is sequentially divided into covering layers having the same number and length as the silicon waveguides in the target area along the extension direction, so that each covering layer covers each target area one-to-one; One of the metal electrodes is connected to the graphene layer, and the other metal electrode is connected to an area on the silicon dioxide substrate not covered by the graphene layer, so as to change the effective refractive index of the target waveguide beam by adjusting the voltage value applied from the metal electrode to the graphene layer, thereby changing the phase difference between adjacent array waveguides.

2. The tunable array waveguide grating router based on graphene and silicon waveguide according to claim 1, characterized in that: An electrical insulation transition layer is provided between the graphene layer and the target waveguide bundle.

3. The tunable array waveguide grating router based on graphene and silicon waveguide according to claim 2, characterized in that: The refractive index of the electrically insulating material constituting the electrically insulating transition layer is between the refractive index of the graphene and the refractive index of silicon.

4. The tunable array waveguide grating router based on graphene and silicon waveguide according to claim 1, characterized in that: The graphene layer includes: one graphene material layer or a plurality of graphene material layers stacked in sequence.

5. The tunable array waveguide grating router based on graphene and silicon waveguide according to claim 1, characterized in that: The length direction of each of the metal electrodes is parallel to the length direction of the target area.

6. The tunable array waveguide grating router based on graphene and silicon waveguide according to any one of claims 1 to 5, characterized in that: Each of the target areas in the target waveguide beam is equally divided into two adjacent groups, one of which is a first adjustment area and the other is a second adjustment area, and then the voltage value applied from the metal electrode to each of the covering layers covering the first adjustment area is adjusted to increase the effective refractive index of the first adjustment area; and the voltage value applied from the metal electrode to each of the covering layers covering the second adjustment area is adjusted to reduce the effective refractive index of the second adjustment area, so as to achieve channel bandwidth tuning of the tunable array waveguide grating router.

7. A method for preparing a tunable array waveguide grating router based on graphene and silicon waveguide according to any one of claims 1 to 6, characterized in that: include: Prepare the silicon dioxide substrate, the silicon waveguides sequentially disposed on the silicon dioxide substrate, and an electrical insulating transition layer on the target area in each silicon waveguide; The graphene layer is prepared and covered on the target waveguide bundle with the graphene layer, one of the metal electrodes is connected to the graphene layer, and another of the metal electrodes is connected to the area on the silicon dioxide substrate not covered by the graphene layer, so as to obtain a tunable array waveguide grating router based on graphene and silicon waveguide.

8. The method for preparing a tunable array waveguide grating router based on graphene and silicon waveguide according to claim 7, characterized in that: Also includes: The operating parameters of the prepared tunable array waveguide grating router based on graphene and silicon waveguide are tested, wherein the operating parameters include: insertion loss, crosstalk, and tunable range of wavelength and bandwidth.

9. The method for preparing a tunable array waveguide grating router based on graphene and silicon waveguide according to claim 7, characterized in that: The step of preparing the silicon dioxide substrate, sequentially disposing the silicon waveguides on the silicon dioxide substrate and the electrical insulating transition layer on the target area in each silicon waveguide comprises: The preset optical waveguide design architecture of the tunable array waveguide grating router based on graphene and silicon waveguide is etched on a silicon wafer on an insulating substrate by using photolithography technology; Using the photoresist pattern as a mask, forming each of the silicon waveguides on the silicon wafer by dry or wet etching technology, and performing a planarization process on the silicon waveguide; By thermal oxidation or chemical vapor deposition, an electrically insulating transition layer is formed on the surface of the target area in each of the silicon waveguides to obtain the silicon dioxide substrate, the silicon waveguides sequentially arranged on the silicon dioxide substrate, and the electrically insulating transition layer on the target area in each of the silicon waveguides.

10. The method for preparing a tunable array waveguide grating router based on graphene and silicon waveguide according to claim 7, characterized in that: The graphene layer is prepared, and the graphene layer is covered on the target waveguide bundle, one of the metal electrodes is connected to the graphene layer, and another of the metal electrodes is connected to the area on the silicon dioxide substrate not covered by the graphene layer, so as to obtain a tunable array waveguide grating router based on graphene and silicon waveguide, comprising: A single or multiple graphene material layer is obtained from a bulk crystal material by a mechanical exfoliation method to form the corresponding graphene layer; Determining the crystal quality, surface morphology, crystal composition and crystal phase information of the graphene material layer; Using graphene transfer technology to cover the graphene layer on the target waveguide bundle; performing heat treatment and nano-machining on the graphene layer covering and the target waveguide bundle; One of the metal electrodes is connected to the graphene layer, another of the metal electrodes is connected to a region on the silicon dioxide substrate that is not covered by the graphene layer, and the metal electrodes are electrically connected to an external circuit.

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