Tunable Arrayed Waveguide Grating Router Based on Graphene and Silicon Waveguide and Preparation Method

Abstract

The present application provides a tunable arrayed waveguide grating router based on graphene and silicon waveguides and a preparation method thereof, which relates to the technical field of optical elements. In the router, a target region is provided in the middle of each silicon waveguide in the length direction of the arrayed waveguides to jointly form a target waveguide bundle; a graphene layer covers the target waveguide bundle and is sequentially divided into respective covering layers along the length direction, and each covering layer covers each target region one by one. Electrodes are respectively connected to the graphene layer and the silicon dioxide substrate, so as to change the effective refractive index of the target waveguide bundle by adjusting the voltage value applied to the graphene layer from the electrodes, and further change the phase difference between adjacent arrayed waveguides. The present application can realize the tunability of the central wavelength and the channel bandwidth, can effectively improve the tuning range, has the characteristic of being independent of the frequency and wavelength, can reduce the tuning time to the picosecond level, and can effectively reduce the sensitivity to high temperature.

Description

Technical Field

[0001] This application relates to the technical field of optical components, and particularly to a tunable arrayed waveguide grating router based on graphene and silicon waveguides and a preparation method thereof. Background Art

[0002] In recent years, thanks to the remarkable progress of technologies such as artificial intelligence, data centers, cloud computing, and blockchain, data traffic has shown a trend of accelerating growth, and communication technologies are also undergoing an upgrading process. As a key networking device in the optical switching network of large-capacity data centers, the reconfigurable ability of the arrayed waveguide grating router (AWGR) has become a key R & D target in technical research by academia and communication equipment manufacturers. Tunable AWGR plays an important role in the optical switching network of data centers. By adjusting the optical characteristics of the arrayed waveguide grating router, such as the effective refractive index of the waveguide, the tunable arrayed waveguide grating router can enable optical signals to be switched and adjusted between different frequencies or wavelengths, thereby achieving flexible optical transmission and signal processing to meet the needs of network burst traffic switching.

[0003] Although there are currently several technologies to achieve the tunability of the arrayed waveguide grating router, current tunable optical waveguide devices often have limitations in terms of response speed, tuning range, and temperature sensitivity, and do not meet the requirements of high-speed burst large-capacity optical switching networks in data centers. The response time of common lithium niobate electro-optic tunable optical waveguide devices is mostly in the nanosecond (ns) to sub-nanosecond (sub-ns) level. The response time of polymer thermo-optic 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-optic tunable optical devices, temperature changes will have a significant impact on the working performance of the devices. Temperature changes will cause the characteristics of the devices to drift, thereby affecting the tuning range and tuning efficiency. Therefore, precise temperature control is often required to maintain performance. In addition, the tuning range of thermo-optic tunable devices is limited by the thermal 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 arrayed waveguide grating router that can improve the tuning range and reduce the high-temperature sensitivity. Summary of the Invention

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

[0006] One aspect of this application provides a tunable arrayed waveguide grating router based on graphene and silicon waveguides, including: a silica substrate, a plurality of silicon waveguides, a graphene layer, and a metal electrode;

[0007] Each of the silicon waveguides is sequentially disposed on the silica substrate; and each of the silicon waveguides includes an input waveguide, an array waveguide, and an output waveguide that are sequentially divided along its length direction, 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;

[0008] The middle of each of the array waveguides in the length direction is divided into a target region, the target regions are parallel to each other, and sequentially increase by a specific length, and jointly form a target waveguide bundle;

[0009] The graphene layer covers the target waveguide bundle, and the graphene layer is sequentially divided into covering layers having the same number and the same length as the silicon waveguides in the target region along the length direction, so that each covering layer covers each of the target regions one by one;

[0010] One of the metal electrodes is connected to the graphene layer, and the other metal electrode is connected to the region on the silica substrate that is not covered by the graphene layer, so as to change the effective refractive index of the target waveguide bundle by adjusting the voltage value applied to the graphene layer from the metal electrode, and further change the phase difference between adjacent array waveguides.

[0011] In some embodiments of the present application, an electrically insulating transition layer is provided between the graphene layer and the target waveguide bundle.

[0012] 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 graphene and the refractive index of silicon.

[0013] In some embodiments of the present application, the graphene layer includes: a graphene material layer or multiple graphene material layers stacked in sequence.

[0014] 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 region.

[0015] In some embodiments of the present application, the target regions in the target waveguide bundle are equally divided into two adjacent groups, one group is a first adjustment region, and the other group is a second adjustment region, and then the voltage value applied to each of the covering layers covering the first adjustment region from the metal electrode is adjusted to increase the effective refractive index of the first adjustment region; and the voltage value applied to each of the covering layers covering the second adjustment region from the metal electrode is adjusted to decrease the effective refractive index of the second adjustment region, so as to achieve channel bandwidth tuning of the tunable arrayed waveguide grating router.

[0016] Another aspect of the present application provides a method for fabricating a tunable arrayed waveguide grating router based on graphene and silicon waveguides, including:

[0017] Fabricating the silica substrate, each of the silicon waveguides sequentially disposed on the silica substrate, and an electrically insulating transition layer on the target region in each of the silicon waveguides;

[0018] Fabricating the graphene layer, covering the graphene layer on the target waveguide bundle, connecting one of the metal electrodes to the graphene layer, and connecting the other metal electrode to the region on the silica substrate not covered by the graphene layer to obtain a tunable arrayed waveguide grating router based on graphene and silicon waveguides.

[0019] In some embodiments of the present application, the method for fabricating the tunable arrayed waveguide grating router based on graphene and silicon waveguides further includes:

[0020] Testing the operating parameters of the fabricated tunable arrayed waveguide grating router based on graphene and silicon waveguides, where the operating parameters include: tunable ranges of insertion loss, crosstalk, wavelength, and bandwidth.

[0021] In some embodiments of the present application, fabricating the silica substrate, each of the silicon waveguides sequentially disposed on the silica substrate, and an electrically insulating transition layer on the target region in each of the silicon waveguides includes:

[0022] Using photolithography technology to engrave the optical waveguide design architecture of a preset tunable arrayed waveguide grating router based on graphene and silicon waveguides on a silicon wafer on an insulating substrate;

[0023] Using the photoresist pattern as a mask, forming each of the silicon waveguides on the silicon wafer through dry or wet etching technology, and planarizing the silicon waveguides;

[0024] Forming an electrically insulating transition layer on the surface of the target region in each of the silicon waveguides by thermal oxidation or chemical vapor deposition to obtain the silica substrate, each of the silicon waveguides sequentially disposed on the silica substrate, and an electrically insulating transition layer on the target region in each of the silicon waveguides.

[0025] In some embodiments of the present application, fabricating the graphene layer, covering the graphene layer on the target waveguide bundle, connecting one of the metal electrodes to the graphene layer, and connecting the other metal electrode to the region on the silica substrate not covered by the graphene layer to obtain a tunable arrayed waveguide grating router based on graphene and silicon waveguides includes:

[0026] A single-layer or multi-layer graphene material layer is obtained from a bulk crystal material by a mechanical exfoliation method to form the corresponding graphene layer;

[0027] Determine the crystal quality, surface morphology, crystal composition, and crystal phase information of the graphene material layer;

[0028] The graphene layer is covered on the target waveguide bundle by a graphene transfer technique;

[0029] Perform heat treatment and nano-processing on the covered graphene layer and the target waveguide bundle;

[0030] Connect one of the metal electrodes to the graphene layer, and connect the other metal electrode to the region on the silica substrate that is not covered by the graphene layer, and electrically connect the metal electrodes to an external circuit.

[0031] The tunable arrayed waveguide grating router based on graphene and silicon waveguide provided by the present application includes: a silica substrate, a plurality of silicon waveguides, a graphene layer, and metal electrodes; each of the silicon waveguides is sequentially arranged on the silica substrate; and each of the silicon waveguides includes an input waveguide, an array waveguide, and an output waveguide that are sequentially divided along its length direction, 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; a target region is divided in the middle of the length direction of each of the array waveguides, the target regions are parallel to each other, the lengths increase in sequence, and together they form a target waveguide bundle; the graphene layer covers the target waveguide bundle, and the graphene layer is sequentially divided along the length direction into a plurality of covering layers that have the same number and length as the silicon waveguides of the target waveguide bundle, so that each covering layer covers each of the target regions one by one; each of the covering layers and the silicon waveguides are respectively connected to both ends of the corresponding metal electrode, so as to change the effective refractive index of the target waveguide bundle by adjusting the voltage value applied from the metal electrode to the graphene layer, and further change 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 characteristic of being independent of the broadband and wavelength, being able to reduce the tuning time to the picosecond level, and being able to effectively reduce the sensitivity to high temperature.

[0032] The additional advantages, objectives, and features of the present application will be partially described below, and will become partially obvious to those of ordinary skill in the art after studying the following text, or can be learned from the practice of the present application. The objectives and other advantages of the present application can be achieved and obtained through the structures specifically pointed out in the specification and the drawings.

[0033] Those skilled in the art will understand that the objectives and advantages achievable with the present application are not limited to those specifically described above, and the above and other objectives achievable with the present application will be more clearly understood from the following detailed description. Description of the Drawings

[0034] The drawings described herein are used to provide a further understanding of the present application, form a part of the present application, and do not limit the present application. The components in the drawings are not drawn to scale, but are only for showing the principles of the present application. For the convenience of showing and describing some parts of the present application, the corresponding parts in the drawings may be enlarged, that is, may become larger relative to other components in the exemplary device actually manufactured according to the present application. In the drawings:

[0035] Figure 1 It is a schematic diagram of the relationship between the effective refractive indices of graphene and silicon waveguides and the chemical potential of graphene.

[0036] Figure 2 It is a schematic structural diagram of a tunable arrayed waveguide grating router based on graphene and silicon waveguides in an embodiment of the present application.

[0037] Figure 3 It is a schematic cross-sectional diagram of a tunable arrayed waveguide grating router based on graphene and silicon waveguides in an embodiment of the present application.

[0038] Figure 4 It is a schematic diagram of the operating principle of a tunable arrayed waveguide grating router based on graphene and silicon waveguides provided in an embodiment of the present application.

[0039] Figure 5 It is a schematic three-dimensional structure diagram of the target area and the cladding layer in a tunable arrayed waveguide grating router based on graphene and silicon waveguides in an embodiment of the present application.

[0040] Figure 6 It is a second schematic cross-sectional diagram of a tunable arrayed waveguide grating router based on graphene and silicon waveguides in an embodiment of the present application.

[0041] Figure 7 It is a schematic diagram of the first adjustment area and the second adjustment area in a tunable arrayed waveguide grating router based on graphene and silicon waveguides in an embodiment of the present application.

[0042] Figure 8 It is a schematic flow diagram of a preparation method of a tunable arrayed waveguide grating router based on graphene and silicon waveguides in an embodiment of the present application.

[0043] Figure 9 It is a schematic flow diagram of step 100 in a preparation method of a tunable arrayed waveguide grating router based on graphene and silicon waveguides in an embodiment of the present application.

[0044] Figure 10 It is a schematic flowchart of step 200 in the preparation method of a tunable arrayed waveguide grating router based on graphene and silicon waveguide in an embodiment of the present application.

[0045] Among them, the attached reference numerals are as follows:

[0046] 1. Silica substrate;

[0047] 2. Silicon waveguide;

[0048] 21. Input waveguide;

[0049] 22. Arrayed waveguide;

[0050] 221. Target area;

[0051] 23. Output waveguide;

[0052] 24. Free propagation area;

[0053] 3. Electrically insulating transition layer;

[0054] 4. Graphene layer;

[0055] 41. Cover layer;

[0056] 5. Metal electrode;

[0057] 6. Target waveguide bundle;

[0058] 7. First adjustment area;

[0059] 8. Second adjustment area. Detailed implementation manners

[0060] To make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below in combination with the implementation manners and the drawings. Herein, the illustrative implementation manners of the present application and their descriptions are used to explain the present application, but do not limit the present application.

[0061] Herein, it should also be noted that in order to avoid obscuring the present application due to unnecessary details, only the structures and / or processing steps closely related to the solution of the present application are shown in the drawings, while other details less related to the present application are omitted.

[0062] It should be emphasized that the term "including / comprising" 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.

[0063] Here, it should also be noted that, unless otherwise specified, the term "connection" in this article can not only refer to direct connection, but also indirect connection with intermediates.

[0064] In the following, embodiments of the present application will be described with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

[0065] Currently, common tunable AWGR solutions mainly include thermally tunable optical devices and electro-optically tunable optical devices. Thermally tunable optical devices can change their refractive index or the structure of the material by heating or cooling the material, thereby causing tuning of the wavelength or frequency. Common tuning materials such as Titanium Nitride (TiN) heating silicon waveguides, liquid crystal materials, etc. Electro-optically tunable optical devices can change the absorption characteristics of semiconductor materials by adjusting the electric field strength, thereby adjusting the transmitted light intensity. Common materials such as lithium niobate thin films, etc. Some scholars have studied a thermally tunable silicon-based AWG device based on the TiN heating principle, and the channel tunable bandwidth reaches 600 GHz. Some scholars have also proposed a thermo-optic effect tunable AWG device based on a silicon-on-insulator (SOI) platform. The maximum insertion loss of this device is 3.9 dB, and the channel crosstalk is about 16 dB. Some scholars have studied an electro-optically tunable AWG device based on a lithium niobate platform, and the tunable range of the central wavelength reaches 2 nm.

[0066] In order to solve the problems of small tuning range and high temperature sensitivity existing in the existing tunable arrayed waveguide grating routers, embodiments of the present application respectively provide a tunable arrayed waveguide grating router based on graphene and silicon waveguides and a preparation method of the tunable arrayed waveguide grating router based on graphene and silicon waveguides, which can realize the arrayed waveguide grating router, and can increase the tuning range of the tunable arrayed waveguide grating router and reduce the high temperature sensitivity.

[0067] 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 integrated optics have begun to attempt to combine two-dimensional materials with silicon waveguide platforms to achieve more possibilities for optical devices. Some scholars have proposed an electro-optic modulator based on graphene combined with silicon. After that, some scholars have elaborated in detail on the theoretical calculation method of the dielectric constant on the surface of graphene, laying the cornerstone for the theoretical research of graphene and silicon waveguides, so that the research on graphene and silicon waveguide devices has become a hot direction in the field of integrated optics. In recent years, optoelectronic devices such as optical modulators, optical switches, and microrings based on two-dimensional materials such as graphene have emerged one after another. 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 as follows: First, tuning an arrayed waveguide grating router requires the arrayed waveguides to have a large tuning range to meet the requirements of communication systems. However, the previously relatively mature high-quality graphene was obtained by mechanical exfoliation, and the maximum size was mostly in the micron level, making it difficult to prepare large-size graphene to achieve a large range of tuning of the AWGR. With the development of graphene preparation technology, there has been research that has proposed and prepared wafer-scale graphene, making it possible to realize a tunable AWGR based on graphene. Second, due to the size limitation of the device (millimeter level), it is difficult to perform three-dimensional numerical simulations on the tunable AWGR based on graphene. Therefore, this application proposes a segmented simulation scheme and successively superimposes the simulation results of each segment through theoretical calculations, so as to be able to achieve relatively accurate numerical simulations and verify the rationality and feasibility of the proposed scheme.

[0068] In order to improve and solve the problems existing in the above-mentioned prior art, this application proposes a design scheme of a tunable arrayed waveguide grating router based on graphene and silicon waveguides with graphene and silicon waveguides as the platform. The silicon waveguide will include general planar optical waveguide (PLC) platforms such as SOI, silicon-on-insulator, and silicon nitride. By applying electrodes on both sides of graphene, the chemical potential of graphene itself is adjusted, and the effective refractive index of the graphene and silicon waveguide composite structure is changed, thereby realizing the tunable function of the central wavelength and channel bandwidth of the arrayed waveguide grating router. Due to the extremely high carrier mobility and strong optoelectronic response characteristics of graphene, this device has broadband wavelength-independent characteristics, can achieve a tuning time reduced to the picosecond level, and has a high temperature-insensitive characteristic.

[0069] Specifically, it will be described in detail through the following embodiments.

[0070] First, graphene is a two-dimensional crystalline material that exists stably at room temperature. Graphene has special optoelectronic modulation characteristics, and its optical properties can be adjusted by applying an external electric field. In the common communication wavelength range of 1550 nm, when the chemical potential of graphene increases from 0 eV to 1 eV, its effective refractive index will change, which makes the equivalent refractive index of the graphene and silicon waveguide structure also have corresponding tunable characteristics, such as Figure 1 shown. At the same time, it also means that the phase of the optical signal will be controllably changed, making the graphene and silicon waveguide structure one of the best candidate platforms for tunable optical devices. This is the key theoretical basis for the design of the tunable arrayed waveguide grating router. In Figure 1 , the abscissa represents the chemical potential of graphene (Chemical potential), with the unit of electron volt (eV), and the ordinate is the equivalent refractive index (Equivalent refractive index) of the graphene and silicon waveguide structure. Figure 1 In, the solid line and the dashed line respectively represent the real part Re(n eff ) and the imaginary part Im(n eff ) of the equivalent refractive index.

[0071] Based on this, the embodiment of the present application provides a tunable arrayed waveguide grating router based on graphene and silicon waveguides. Refer to Figure 2 , Figure 3 and Figure 4 , where the number of silicon waveguides 2 in Figure 2 and Figure 4 is only for illustration. In actual applications, the number will be set according to actual application requirements; the tunable arrayed waveguide grating router based on graphene and silicon waveguides specifically includes the following:

[0072] A silica substrate 1, a plurality of silicon waveguides 2, a graphene layer 4, and a metal electrode 5.

[0073] Each of the silicon waveguides 2 is sequentially arranged on the silica substrate 1; and each of the silicon waveguides 2 includes an input waveguide 21, an arrayed waveguide 22, and an output waveguide 23 that are sequentially divided along its length direction, and a free transmission region 24 is formed between the input waveguide 21 and the arrayed waveguide 22 in each silicon waveguide 2, and a free transmission region 24 is also formed between the arrayed waveguide 22 and the output waveguide 23 in each silicon waveguide 2.

[0074] In the middle of the length direction of each of the array waveguides 22, a target area 221 is defined. The target areas 221 are parallel to each other and together form a target waveguide bundle 6, where the lengths of the target areas increase in sequence and the change amount is the same. Here, the array waveguides are not necessarily fan-shaped. In an example design of the present application, each of the array waveguides 22 can be in a shape with parallel middle and arc-shaped sides; other different shapes such as a saddle shape can also be used.

[0075] Each of the cladding layers 41 completely coincides with the target area 221.

[0076] One of the two metal electrodes 5 is connected to the graphene layer 4, and the other electrode is connected to the silica substrate 1 without graphene coverage; meanwhile Figure 3 The graphene inside is not interconnected. It only exists above the waveguide, and there is some on the side and both sides, but they are not connected. There is a certain distance in the middle without graphene coverage, exposing the silica substrate 1. The exposed silica substrate 1 is used to place the other 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 bundle 6 is changed, thereby changing the phase difference between adjacent array waveguides 22.

[0077] See Figure 4 , when a 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 diffract in the free propagation region. The obtained diffracted signals reach each array waveguide 22 and then propagate independently. Since there is a stable length difference between adjacent array waveguides 22, and at the same time a stable and adjustable optical path difference is generated under the action of voltage, for a specific wavelength, the diffracted signals in each array waveguide 22 will have a stable and adjustable phase difference, and then through interference in the free propagation region, interference enhancement positions or interference cancellation positions with alternating light and dark are formed. At the same time, because the phase differences of different wavelengths are different, interference maxima will be formed at different positions, so that the multi-wavelength signals are respectively output through the output waveguides 23 at different positions, and the output positions of specific wavelengths are adjustable.

[0078] Specifically, in the embodiment of the present application, by combining graphene and silicon-based waveguides, a graphene and silicon waveguide 2 structure is formed. By setting an electrode on the graphene, the chemical potential of the graphene is changed, and the effective refractive index of the graphene and silicon waveguide 2 is adjusted, thereby realizing the tuning function of the array waveguide 22 grating router (which can be abbreviated as an AWGR device).

[0079] In a specific example, in order to accurately tune the output positions of different wavelengths, see Figure 5, on the silica substrate 1 is the silicon waveguide 2 structure, where the typical width of the silicon waveguide 2 is 500 nm, and the typical height of the silicon waveguide 2 is 220 nm. The typical width and typical height are the most commonly used width and height parameters of the SOI waveguide (i.e., silicon waveguide on insulator), and they can also be adjusted appropriately. The approximate adjustment range should be 400 - 650 nm for the width and 180 - 240 nm for the height.

[0080] In the embodiment of the present application, the graphene layer 4 is the key part to realize the tunability of the AWGR device.

[0081] Metal electrodes 5 (such as gold) are placed on the outermost two sides of the graphene layer 4 to facilitate directly affecting the graphene layer 4 by applying voltage through the electrodes.

[0082] By adjusting the applied voltage of the graphene and the silicon waveguide 2 structure, the effective refractive index of the silicon waveguide 2 (i.e., the target waveguide bundle 6) covered with graphene is changed, thereby changing the phase difference between adjacent array waveguides 22. This will cause the movement of the position of the interference enhancement maximum formed after interference in the free propagation region, thus realizing the tunable function of the AWGR device. The principle of the related grating interference equation can be expressed as:

[0083] (1-1)

[0084] In the above formula (1-1), n s is the effective refractive index of the wavelength λ at the waveguide in the free propagation region, d is the spacing between each input waveguide 21 and the spacing between each output waveguide 23, and θ in is the angle between adjacent input waveguides 21, and θ out is the angle between adjacent output waveguides 23, represents the length difference introduced by the different angles of adjacent input waveguides, represents the length difference introduced by the different angles of adjacent output waveguides, n c0 is the effective refractive index of the wavelength λ in the waveguides of the input waveguide 21, output waveguide 23 and array waveguide 22 except for the target region 221, Δl0 is the length difference between adjacent waveguides in each array waveguide 22 except for the target region 221, n c_graphene is the effective refractive index of the wavelength λ at the graphene and the silicon waveguide 2 (i.e., the target waveguide bundle 6), as Figure 4 the triangular region in is the region where the graphene layer 4 covers the target waveguide bundle 6. Δl g is the length difference between the graphene (and the target region 221) covered in each adjacent array waveguide 22, m is the waveguide diffraction order of the AWGR device, and λ represents the central wavelength of the device.

[0085] As can be seen from the above grating interference equation, when the chemical potential of graphene changes, i.e., n c_graphene changes accordingly, and then the central wavelength λ of the device shifts, and the shift range can be expressed as:

[0086] (1-2)

[0087] In the above formula (1-2), n c2 and n c1 are the effective refractive indices of graphene and silicon waveguide 2 (i.e., the target waveguide bundle 6) before and after the change of the chemical potential, respectively.

[0088] As can be seen from the above description, the tunable arrayed waveguide grating router based on graphene and silicon waveguide provided by the embodiments of the present application can achieve tunability of the central wavelength and channel bandwidth, can effectively improve the tuning range, has the characteristic of being independent of frequency and wavelength, can reduce the tuning time to the picosecond level, and can effectively reduce the sensitivity to high temperature.

[0089] In order to effectively prevent current from directly flowing from graphene into silicon waveguide 2, in a tunable arrayed waveguide grating router based on graphene and silicon waveguide provided by the embodiments of the present application, referring to Figure 6 , an electrically insulating transition layer 3 is provided between the graphene layer 4 and the target waveguide bundle 6, but the electrically insulating transition layers 3 are not connected to each other. It only exists above the waveguide, and there are some on the side and both sides, but they are not connected, and there is a certain distance in the middle, which will expose the silicon dioxide substrate in the middle groove.

[0090] That is to say, an electrically insulating transition layer 3 can also be provided between the graphene layer 4 and the silicon waveguide. The electrically insulating transition layer 3 can specifically adopt an electrically insulating material with a thickness of 7 nm, which can effectively prevent current from directly flowing from graphene into silicon waveguide 2, thereby maintaining the electrical properties of graphene and ensuring the application effect of voltage.

[0091] In order to further improve the propagation characteristics of light waves in the graphene and silicon waveguide 2 composite structure, in a tunable arrayed waveguide grating router based on graphene and silicon waveguide provided by the embodiments 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 graphene and the refractive index of silicon.

[0092] In a specific implementation manner, the electrically insulating material of the electrically insulating transition layer 3 can adopt aluminum oxide Al2O3. 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 silicon waveguide 2 and further improves the propagation characteristics of light waves in the graphene and silicon waveguide 2 composite structure.

[0093] In order to further improve the application reliability and effectiveness of the graphene layer 4, in a tunable arrayed 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 multiple graphene material layers stacked in sequence.

[0094] Specifically, one or several layers of two-dimensional graphene material layers can be arranged above the Al2O3.

[0095] In order to further reduce the lateral coupling between the metal electrodes 5, in a tunable arrayed waveguide grating router based on graphene and silicon waveguide provided in an embodiment of the present application, the length direction of each of the metal electrodes 5 is parallel to the length direction of the target region 221. That is, each of the metal electrodes 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 effect of parasitic capacitance on the tunable AWGR device in high-speed applications that require up to hundreds of Gbps.

[0096] In order to achieve channel bandwidth tuning, in a tunable arrayed waveguide grating router based on graphene and silicon waveguide provided in an embodiment of the present application, referring to Figure 7 , each of the target regions 221 in the target waveguide bundle 6 is equally divided into two adjacent groups, one group is the first adjustment region 7, and the other group is the second adjustment region 8. Furthermore, the voltage value applied from the metal electrode 5 to each of the covering layers 41 covering the first adjustment region 7 is adjusted to increase the effective refractive index of the first adjustment region 7; and the voltage value applied from the metal electrode 5 to each of the covering layers 41 covering the second adjustment region 8 is adjusted to decrease the effective refractive index of the second adjustment region 8, so as to achieve channel bandwidth tuning of the tunable arrayed waveguide grating router.

[0097] Specifically, when the arrayed waveguide 22 is equally divided into upper and lower regions, the first adjustment region 7 and the second adjustment region 8 each cover half of the number of AWGR arrayed waveguides 22. The voltages applied to the first adjustment region 7 and the second adjustment region 8 are respectively adjusted 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 arrayed waveguide 22 in the first adjustment region 7 to increase, and the output center wavelength corresponding to the arrayed waveguide 22 in the second adjustment region 8 to decrease, thereby achieving channel bandwidth tuning, and its corresponding channel bandwidth tuning range is expressed as:

[0098] (1-3)

[0099] In formula (1-3), n c3 and n c2They are the effective refractive indices at the graphene-silicon waveguide in region A and region B after the change in chemical potential, respectively, n c1 is the effective refractive index at the graphene-silicon waveguide before the change in chemical potential, Δl g is the length difference between the graphene (and the target region 221) covered in each adjacent array waveguide 22, and m is the waveguide diffraction order of the AWGR device. Substitute the effective refractive indices of graphene at different chemical potentials into the above formulas (1-3) of the AWGR device for calculation, and a preliminary design scheme of the tunable AWGR device can be obtained.

[0100] Based on the tunable arrayed waveguide grating router based on graphene and silicon waveguide of the above embodiments, the present application also provides a preparation method of a tunable arrayed waveguide grating router based on graphene and silicon waveguide. See Figure 8 The preparation method of the tunable arrayed waveguide grating router based on graphene and silicon waveguide specifically includes the following contents:

[0101] Step 100: Prepare the silica substrate, each of the silicon waveguides sequentially disposed on the silica substrate, and the electrically insulating transition layer on the target region in each of the silicon waveguides.

[0102] Step 200: Prepare the graphene layer, cover the graphene layer on the target waveguide bundle, and respectively dispose the metal electrodes in the length direction of each of the covering layers and on the silica substrate waveguide to obtain a tunable arrayed waveguide grating router based on graphene and silicon waveguide.

[0103] On this basis, in order to further improve the application reliability of the tunable arrayed waveguide grating router based on graphene and silicon waveguide, after step 200 in the preparation method of the tunable arrayed waveguide grating router based on graphene and silicon waveguide of the present application, step 300 is specifically included: Test the operating parameters of the prepared tunable arrayed waveguide grating router based on graphene and silicon waveguide, where the operating parameters include: insertion loss, crosstalk, tunable range of wavelength and bandwidth.

[0104] Specifically, test the prepared tunable AWGR device, and test the tunable range of the central wavelength and bandwidth of the device. The test platform uses a Santec TSL-570 1480-1640nm type c tunable laser, couple the AWGR device with the optical fiber through a Dedi-Ye S60-05M high-precision six-axis displacement platform, and test the output spectrum of the AWGR through an Agilent spectrometer to obtain parameters such as the insertion loss, crosstalk, tunable range of wavelength and bandwidth of the device.

[0105] In a specific implementation manner, see Figure 9, Step 100 in the preparation method of the tunable arrayed waveguide grating router based on graphene and silicon waveguide specifically includes the following content:

[0106] Step 110: Use lithography technology to engrave the optical waveguide design architecture of the preset tunable arrayed waveguide grating router based on graphene and silicon waveguide on a silicon (SOI) wafer on an insulating substrate.

[0107] Step 120: Use the photoresist pattern as a mask, and form each of the silicon waveguides on the silicon (SOI) wafer through dry or wet etching technology, and perform planarization treatment on the silicon waveguides.

[0108] Step 130: Respectively form an electrically insulating transition layer on the surface of the target area in each of the silicon waveguides through thermal oxidation or chemical vapor deposition, so as to obtain the silicon dioxide substrate, each of 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.

[0109] Specifically, first select an SOI wafer, usually with a silicon-insulator-silicon structure. This substrate structure will be used for the fabrication of optical waveguides. Secondly, define the optical waveguides. Use lithography technology to define the optical waveguide design pattern on the SOI. This process includes making a mask on the SOI wafer and coating photoresist, and then forming a light mode pattern by exposing and developing the optical waveguide template. The next step is etching. Use the photoresist pattern as a mask, and remove the top layer of silicon not protected by the photoresist through dry etching (such as reactive ion etching, RIE) or wet etching technology, remove the non-desired areas of the optical waveguide mode, and then use chemical solvents or plasma treatment to remove the remaining photoresist, thereby forming the optical waveguide structure. In addition, it is also necessary to form an electrically insulating transition layer on the waveguide surface through thermal oxidation or chemical vapor deposition (CVD). In addition, it also includes planarization treatments such as chemical mechanical polishing (CMP) of the silicon waveguides, so as to enhance the bonding process at the junction of graphene and silicon waveguides and reduce the generation of holes and defects.

[0110] In a specific implementation, refer to Figure 10 , Step 200 in the preparation method of the tunable arrayed waveguide grating router based on graphene and silicon waveguide specifically includes the following content:

[0111] Step 210: Use the mechanical exfoliation method to obtain a single-layer or multi-layer graphene material layer from a bulk crystal material to form the corresponding graphene layer.

[0112] Step 220: Determine the crystal quality, surface morphology, crystal composition, and crystal phase information of the graphene material layer.

[0113] Step 230: Using graphene transfer technology to cover the target waveguide bundle with the graphene layer.

[0114] Step 240: thermally treat and nano-process the graphene layer covering and the target waveguide bundle.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] In one or more embodiments of the present application, the structures of graphene and silicon waveguides can be applied to other two-dimensional materials, such as transition metal dichalcogenides (TMDs), molybdenum disulfide (MoS2), graphene twist angle, and two-dimensional heterojunction structures.

[0119] The key point of the present application is to achieve the tunable function of the central wavelength and bandwidth of the AWGR device through graphene and silicon waveguides. By combining two-dimensional materials such as graphene with a 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 and adjusting the effective refractive indices of graphene and silicon waveguides in the two regions respectively, the bandwidth tunable function of the AWGR device is achieved.

[0120] In summary, the present application utilizes the graphene and silicon waveguide structures to achieve the tunable function of the AWGR device. Compared with common thermal tuning optical devices achieved by heating TiN and electro-optic tuning optical devices based on the lithium niobate platform, the present application changes the chemical potential of graphene itself by applying electrodes on both sides of graphene to tune the effective refractive index of the graphene and silicon waveguide structures. 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 higher than that of silicon-based materials. Therefore, a tuning time at the picosecond level 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 carrier mobility of graphene can remain basically stable. This makes the AWGR device highly insensitive to temperature. In addition, the device based on graphene and silicon waveguides can be compatible with the CMOS process, 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.

[0121] Those of ordinary skill in the art should understand that the various exemplary components, systems, and devices described in connection with the embodiments disclosed herein can be implemented in hardware, software, or a combination of both. Specifically, whether to implement it in hardware or software depends on the specific application and design constraints of the technical solution. A professional technician can use different devices for each specific application to implement the described functions, but such implementation should not be considered to exceed 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 functional card, and so on. 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 through a data signal carried in a carrier wave on a transmission medium or a communication link.

[0122] It should be clear that this application is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, the 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 this application is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order between steps after understanding the spirit of this application.

[0123] In this application, the features described and / or illustrated for one embodiment can be used in the same or similar manner in one or more other embodiments, and / or combined with the features of other embodiments or replace the features of other embodiments.

[0124] The above are only the preferred embodiments of this application and are not used to limit this application. For those skilled in the art, various changes and variations can be made to the embodiments of this application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A tunable arrayed waveguide grating router based on graphene and silicon waveguide, characterized in that, Comprising: A silica substrate, a plurality of silicon waveguides, a graphene layer, and metal electrodes; Each of the silicon waveguides is sequentially disposed on the silica substrate; and each of the silicon waveguides includes an input waveguide, an array waveguide, and an output waveguide sequentially divided along its length direction, 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; A target region is divided in the middle of the length direction of each of the array waveguides, and the target regions are parallel to each other and jointly form a target waveguide bundle; The graphene layer covers the target waveguide bundle to form a triangular region, there is a length difference between the target regions corresponding to adjacent array waveguides, and the graphene layer is sequentially divided along the length direction into covering layers having the same number and length as the silicon waveguides in the target region, so that each covering layer covers each of the target regions one-to-one; One of the metal electrodes is connected to the graphene layer, and the other metal electrode is connected to the region on the silica substrate that is not covered by the graphene layer, so as to change the effective refractive index of the target waveguide bundle by adjusting the voltage value applied from the metal electrode to the graphene layer, and further change the phase difference between adjacent array waveguides; Each of the target regions in the target waveguide bundle is equally divided into two adjacent groups, one group is the first adjustment region, and the other group is the second adjustment region, and then the voltage value applied from the metal electrode to each of the covering layers covering the first adjustment region is adjusted to increase the effective refractive index of the first adjustment region; and the voltage value applied from the metal electrode to each of the covering layers covering the second adjustment region is adjusted to decrease the effective refractive index of the second adjustment region, so as to realize the channel bandwidth tuning of the tunable array waveguide grating router.

2. The tunable arrayed waveguide grating router based on graphene and silicon waveguide according to claim 1, wherein An electrically insulating transition layer is provided between the graphene layer and the target waveguide bundle.

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

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

5. The tunable arrayed 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 region.

6. A preparation method of a tunable arrayed waveguide grating router based on graphene and silicon waveguide according to any one of claims 1 to 5, characterized in that, Comprising: Preparing the silica substrate, each of the silicon waveguides sequentially disposed on the silica substrate, and the electrically insulating transition layer on each of the target regions in each of the silicon waveguides; Preparing the graphene layer, covering the graphene layer on the target waveguide bundle, connecting one of the metal electrodes to the graphene layer, and connecting the other metal electrode to the region on the silica substrate that is not covered by the graphene layer, so as to obtain a tunable array waveguide grating router based on graphene and silicon waveguides.

7. The preparation method of the tunable arrayed waveguide grating router based on graphene and silicon waveguide according to claim 6, characterized in that Further comprising: Testing the operating parameters of the prepared tunable array waveguide grating router based on graphene and silicon waveguides, wherein the operating parameters include: insertion loss, crosstalk, tunable range of wavelength and bandwidth.

8. The preparation method of the tunable arrayed waveguide grating router based on graphene and silicon waveguide according to claim 6, wherein, The preparation of the silica substrate, each of the silicon waveguides sequentially disposed on the silica substrate, and the electrically insulating transition layer on the target region in each of the silicon waveguides includes: Using photolithography technology to engrave the optical waveguide design architecture of a preset tunable arrayed waveguide grating router based on graphene and silicon waveguides on a silicon wafer on an insulating substrate; Using the photoresist pattern as a mask, forming each of the silicon waveguides on the silicon wafer by dry or wet etching technology, and planarizing the silicon waveguides; By thermal oxidation or chemical vapor deposition, forming an electrically insulating transition layer on the surface of the target region in each of the silicon waveguides respectively, so as to obtain the silica substrate, each of the silicon waveguides sequentially disposed on the silica substrate, and the electrically insulating transition layer on the target region in each of the silicon waveguides.

9. The preparation method of the tunable arrayed waveguide grating router based on graphene and silicon waveguide according to claim 6, wherein The preparation of the graphene layer, covering the graphene layer on the target waveguide bundle, and connecting one of the metal electrodes to the graphene layer and the other metal electrode to the region on the silica substrate not covered by the graphene layer, so as to obtain a tunable arrayed waveguide grating router based on graphene and silicon waveguides, includes: Obtaining a single-layer or multi-layer graphene material layer from a bulk crystal material by mechanical exfoliation method to constitute 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-processing on the graphene layer covering and the target waveguide bundle; Connecting one of the metal electrodes to the graphene layer, connecting the other metal electrode to the region on the silica substrate not covered by the graphene layer, and electrically connecting the metal electrodes to an external circuit.

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