Hybrid waveguide integrated graphene mid-infrared electro-optic modulator

Abstract

The application discloses a mixed waveguide integrated graphene mid-infrared electro-optic modulator. The application comprises a sapphire substrate; a silicon waveguide transmission layer is formed on the sapphire substrate; a first graphene layer is located on one side of the silicon waveguide transmission layer; a first graphene layer control electrode arrangement is connected on the first graphene layer; a chalcogenide medium layer is formed on the silicon waveguide transmission layer, and the first graphene layer is covered; a second graphene layer is located on one side of the chalcogenide medium layer; a second graphene layer control electrode arrangement is arranged on the second graphene layer; a chalcogenide strip waveguide is formed on the second graphene layer; and a chalcogenide cover layer is formed on the chalcogenide medium layer, and the second graphene layer and the chalcogenide strip waveguide are covered. The application supports low-loss transmission and modulation of signal light in the 3-5 mu m waveband. The application uses a silicon flat plate layer and a chalcogenide strip waveguide to form a mixed ridge waveguide structure, and the graphene layer can be integrated at the maximum field strength of the TE0 mode, thereby reducing optical power consumption.

Description

Technical Field

[0001] This invention relates to an optical intensity modulation device in the field of optical communication technology, specifically a mid-infrared electro-optic modulator integrated with a hybrid waveguide based on a sapphire-silicon-chalcogenide-graphene system. Background Technology

[0002] The mid-infrared band (2-20μm) is an optical band with significant engineering application value. Firstly, it contains the absorption fingerprints (7μm-20μm) of most chemical and biological molecules, making it suitable for chemical gas sensing and bio-information sensing. Secondly, it includes atmospheric windows (3-5μm and 8-14μm), which can be used for thermal imaging, infrared countermeasures, and free-space communication. Its strong water absorption in the 2μm band and low penetration into human tissue make it suitable for wind direction tracking and precision surgery. Free-space communication, a fiber-free point-to-point bidirectional information transmission technology, has significant implications and broad application prospects in bandwidth access, wide area network and metropolitan area network expansion, local area network interconnection, and deep space communication. These applications rely heavily on functional devices such as mid-infrared lasers, amplifiers, optical switches, optical modulators, detectors, wavelength division multiplexers, and power dividers. Chip-level mid-infrared devices provide important fundamental conditions for greatly improving the performance of mid-infrared application systems and reducing system size. In particular, research on mid-infrared chip-integrated modulators provides key support for building compact, high-speed, low-power 3-5μm band space optical communication systems. Summary of the Invention

[0003] To improve the modulation speed and reduce the modulation power consumption of current 3-5μm mid-infrared modulators, the present invention aims to provide a hybrid waveguide integrated mid-infrared modulator based on a sapphire-silicon-chalcogenide glass-graphene system with strong light-matter interaction, supporting TEO mode optical signal transmission and modulation; achieving low-power modulation through the strong interaction between graphene and the TEO mode; and realizing ultra-high-speed modulation by utilizing the high carrier mobility of graphene.

[0004] To achieve the above objectives, the technical solution adopted by the present invention includes:

[0005] This invention includes a sapphire substrate, a silicon waveguide transmission layer, a first graphene layer, a first graphene layer electrode, a chalcogenide dielectric layer, a second graphene layer, a second graphene layer electrode, a chalcogenide strip waveguide, and a chalcogenide capping layer. The sapphire substrate, silicon waveguide layer, and chalcogenide materials all support low-loss transmission of light waves with wavelengths of 3-5 μm.

[0006] Including sapphire substrate;

[0007] Includes a silicon waveguide transmission layer formed on a sapphire substrate;

[0008] It includes a first graphene layer, located on one side of the silicon waveguide transmission layer;

[0009] It includes a first graphene layer control electrode, which is arranged and connected on the first graphene layer.

[0010] It includes a chalcogenide dielectric layer formed on a silicon waveguide transmission layer and covered with a first graphene layer;

[0011] It includes a second graphene layer, located on one side of the chalcogenide dielectric layer;

[0012] It includes a second graphene layer control electrode, which is arranged and connected on the second graphene layer.

[0013] Including chalcogenide strip waveguides, formed on the second graphene layer;

[0014] It includes a chalcogenide capping layer formed on a chalcogenide dielectric layer, and is covered with a second graphene layer and a chalcogenide strip waveguide.

[0015] The first and second graphene layers are located on opposite sides, and the chalcogenide strip waveguide is located in the middle between the first and second graphene layers. Both the first and second graphene layers extend directly below the chalcogenide strip waveguide, such that the chalcogenide strip waveguide is located above the second graphene layer and connected to the second graphene layer.

[0016] It also includes two through-hole electrodes, which are respectively connected to the first graphene layer control electrode and the second graphene layer control electrode. The first graphene layer control electrode and the second graphene layer control electrode are respectively connected to the two ends of an external voltage through their respective through-hole electrodes.

[0017] The hybrid ridge waveguide, composed of the silicon waveguide transmission layer, the chalcogenide dielectric layer, and the chalcogenide strip waveguide, propagates along the hybrid ridge waveguide and interacts strongly with the first graphene layer.

[0018] The first graphene layer, the chalcogenide dielectric layer, the second graphene layer, and the control electrode constitute a capacitor structure. The first graphene layer is electro-inductively doped, and the light absorption rate is changed by changing the carrier concentration, thereby realizing electro-optic modulation.

[0019] The sapphire substrate is made of sapphire material.

[0020] The first and second graphene layers are made of graphene material.

[0021] The first graphene layer control electrode and the second graphene layer control electrode are made of metallic materials.

[0022] The silicon waveguide transmission layer is made of silicon material.

[0023] The chalcogenide dielectric layer, chalcogenide strip waveguide, and chalcogenide capping layer are made of materials including, but not limited to, Ge. 23 Sb7S 70 Chalcogenide glass materials with Ge2Sb2Se5 composition.

[0024] The structure and material system of this invention have the characteristics of a wide infrared window and high optical nonlinearity, which enable the device to operate with low loss in the mid-infrared band.

[0025] The electromodulator of the present invention uses bilayer graphene and has a control electrode, thus enabling electro-inductive doping of graphene for high-speed electro-optic modulation.

[0026] Beneficial effects of this invention:

[0027] The substrate and waveguide structure in this invention support low-loss transmission of signal light in the 3-5μm band. Simultaneously, graphene can be absorbed in the mid-infrared band, thereby modulating the signal light. Based on this material system, silicon planar / chalcogenide strip waveguide structures can be fabricated, supporting TEO mode transmission. Because it is a hybrid material system, graphene can flexibly shift at the mode light field maxima, greatly enhancing the interaction between graphene and signal light, thus reducing optical power consumption.

[0028] This invention uses a silicon planar layer and a chalcogenide strip waveguide to form a hybrid ridge waveguide structure, and the graphene layer can be integrated at the field maxima of the TEO mode.

[0029] This invention flexibly integrates graphene, greatly enhancing the interaction between light and matter, and proposes a new solution for realizing ultra-fast and ultra-low power electro-optic modulators in the mid-infrared band. Attached Figure Description

[0030] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0031] Figure 1 This is a schematic diagram of a sapphire substrate / silicon planar waveguide layer / chalcogenide strip waveguide / chalcogenide capping layer structure according to an exemplary embodiment.

[0032] Figure 2 yes Figure 1 The diagram shows the TE0 mode field distribution of the sapphire substrate / silicon planar waveguide layer / chalcogenide strip waveguide / chalcogenide capping layer structure.

[0033] Figure 3 It is an electro-optic modulator in the form of a straight waveguide.

[0034] Figure 4 It is an electro-optic modulator in the form of a micro-ring.

[0035] Figure 5 This is a comparison chart showing the modulation effect of the device of the present invention and a conventional silicon waveguide device (graphene transferred on the upper surface of the waveguide).

[0036] In the figure: sapphire substrate (1), silicon waveguide transmission layer (2), first graphene layer (3), first graphene layer control electrode (4), chalcogenide dielectric layer (5), second graphene layer (6), second graphene layer control electrode (7), chalcogenide waveguide (8), chalcogenide capping layer (9), through-hole electrode (10). Detailed Implementation

[0037] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0038] The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0039] like Figure 1 As shown, the device structure includes:

[0040] Including sapphire substrate 1;

[0041] It includes a silicon waveguide transmission layer 2, which is formed on a sapphire substrate 1 and integrated with the sapphire substrate 1 using a bonding process;

[0042] It includes a first graphene layer 3, located on one side of the silicon waveguide transmission layer 2, which is transferred and fabricated on the silicon waveguide transmission layer 2;

[0043] It includes a first graphene layer control electrode 4, which is arranged and connected on the first graphene layer 3.

[0044] It includes a chalcogenide dielectric layer 5, which is formed on the silicon waveguide transmission layer 2, specifically grown on the first graphene layer 3 by thermal evaporation and coated with the first graphene layer 3.

[0045] The second graphene layer 6 is located on one side of the chalcogenide dielectric layer 5 and is transferred onto the chalcogenide dielectric layer 5.

[0046] It includes a second graphene layer control electrode 7, which is arranged and connected on the second graphene layer 6.

[0047] It includes a chalcogenide strip waveguide 8, which is formed on the second graphene layer 6, specifically grown on the second graphene layer 6 using a thermal evaporation process.

[0048] It includes a chalcogenide capping layer 9, which is formed on the chalcogenide dielectric layer 5. Specifically, it is grown on the second graphene layer 6 by thermal evaporation and covers the second graphene layer 6 and the chalcogenide strip waveguide 8 to provide waveguide protection.

[0049] The first graphene layer 3 and the second graphene layer 6 are located on both sides and are arranged at intervals. The chalcogenide strip waveguide 8 is located in the middle between the first graphene layer 3 and the second graphene layer 6. Both the first graphene layer 3 and the second graphene layer 6 extend directly below the chalcogenide strip waveguide 8, so that the chalcogenide strip waveguide 8 is located on top of the second graphene layer 6 and connected to the second graphene layer 6.

[0050] The first graphene layer control electrode 4 and the second graphene layer control electrode 7 are also distributed on both sides, arranged at intervals, and after passing through the chalcogenide dielectric layer 5 and the chalcogenide capping layer 9, they are respectively connected to the top surface of their respective graphene layers.

[0051] The present invention, through the above-described structural arrangement, arranges the first graphene layer 3, the second graphene layer 6, and the chalcogenide strip waveguide 8 sequentially from bottom to top on the silicon waveguide transmission layer 2. The first graphene layer 3 is located at the point of strongest optical field, and the interaction between the first graphene layer 3 and the optical field is greatly enhanced, thereby greatly improving its modulation effect on light and achieving the advantages of reducing device length and lowering modulation power consumption.

[0052] It also includes two through-hole electrodes 10, which are respectively connected to the first graphene layer control electrode 4 and the second graphene layer control electrode 7. The first graphene layer control electrode 4 and the second graphene layer control electrode 7 are respectively connected to the two ends of an external voltage through their respective through-hole electrodes 10.

[0053] The through-hole electrode 10 is prepared in the sulfur capping layer 9 and is connected to the control electrodes 4 and 7 through the sulfur capping layer 9.

[0054] A hybrid ridge waveguide is formed by a silicon waveguide transmission layer 2, a chalcogenide dielectric layer 5, and a chalcogenide strip waveguide 8. The TEO mode optical signal propagates along the hybrid ridge waveguide formed by the silicon waveguide transmission layer 2, the chalcogenide dielectric layer 5, and the chalcogenide strip waveguide 8, and interacts strongly with the first graphene layer 3.

[0055] The first graphene layer 3, the chalcogenide dielectric layer 5, the second graphene layer 6, and the control electrodes 4 and 7 constitute a planar capacitor structure. Different bias voltages are applied to the two graphene layers, and different charges are induced on the first graphene layer 3. Electro-inductive doping is performed on the first graphene layer 3, that is, the light absorption rate is changed by changing the carrier concentration of the graphene layer 3, thereby realizing electro-optic modulation.

[0056] like Figure 2 These are the simulation results of the field distribution of the TE0 mode of the waveguide structure of this invention. The sub-figures, from left to right, represent the total field intensity E, the x-component E, and so on. x , y component E y z component E z The directions of the electric field components are shown in the figure, where the z-direction is perpendicular to the cross-section and represents the direction of light propagation.

[0057] Specifically, the first graphene layer (3) is located at the maximum value of the total electric field E, which is also the point where E is at its maximum value. x The maximum value E xmax At the location. Electric field x component E x The polarization direction is parallel to the graphene plane, enabling strong interaction with graphene and achieving advantages such as reduced optical power consumption and smaller device length.

[0058] Graphene layers 3 and 6 and control electrodes 4 and 7 constitute a planar capacitor structure. The first graphene layer 3 is electro-inductively doped by the second graphene layer 6, that is, the carrier concentration of the graphene layer 3 is changed by the electro-inductive effect, thereby changing its light absorption rate and realizing ultrafast electro-optic modulation.

[0059] Example 1

[0060] Constructing electro-optic modulators in the form of straight waveguides, such as Figure 3 As shown.

[0061] The chalcogenide waveguide 8 is a straight waveguide arranged linearly along the direction of optical signal propagation. The first graphene layer 3, the first graphene layer control electrode 4, the chalcogenide dielectric layer 5, the second graphene layer 6, the second graphene layer control electrode 7, and the chalcogenide waveguide 8 are all arranged linearly along the direction of optical signal propagation on the required waveguide segment to form the structure of this invention. In this embodiment, the graphene is electrochemically doped using the aforementioned capacitor structure to change its light absorption rate and directly modulate the transmittance of the signal light.

[0062] Considering a working wavelength of 4.3 μm, and defining the initial Fermi level of graphene as 0.12 eV and the modulated Fermi level as 0.3 eV, the modulation depth and required power consumption of devices with different graphene lengths can be calculated. The modulation effect of the device designed in this patent is compared with that of a conventional silicon waveguide device (graphene transferred to the waveguide surface), and the results are as follows. Figure 5 As shown, at the same modulation depth, the device designed in this patent can use shorter graphene, and at the same graphene length, the device designed in this patent has lower modulation power consumption.

[0063] Example 2

[0064] Constructing micro-ring-shaped electro-optic modulators, such as Figure 4 As shown.

[0065] The chalcogenide waveguide 8 comprises a straight waveguide arranged linearly along the direction of optical signal propagation and a micro-ring waveguide coupled to the side of the straight waveguide. The first graphene layer 3, the first graphene layer control electrode 4, the chalcogenide dielectric layer 5, the second graphene layer 6, the second graphene layer control electrode 7, and the chalcogenide waveguide 8 are all arranged linearly along the direction of optical signal propagation on one side of the micro-ring waveguide, forming the structure of this invention. In this embodiment, the graphene is inductively doped using the aforementioned capacitor structure to modulate the graphene's absorptivity, change the coupling conditions of the micro-ring, and thus alter the transmittance of its resonant wavelength, thereby producing a modulation effect.

[0066] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0067] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1.A hybrid waveguide integrated graphene mid-infrared electro-optic modulator, comprising: a sapphire substrate (1); a silicon waveguide transmission layer (2) formed on the sapphire substrate (1); a first graphene layer (3) located on one side of the silicon waveguide transmission layer (2); a first graphene layer control electrode (4) arranged on the first graphene layer (3); a chalcogenide medium layer (5) formed on the silicon waveguide transmission layer (2) and covering the first graphene layer (3); a second graphene layer (6) located on one side of the chalcogenide medium layer (5); a second graphene layer control electrode (7) arranged on the second graphene layer (6); a chalcogenide strip waveguide (8) formed on the second graphene layer (6); and a chalcogenide cover layer (9) formed on the chalcogenide medium layer (5) and covering the second graphene layer (6) and the chalcogenide strip waveguide (8). 2.The hybrid waveguide integrated graphene mid-infrared electro-optic modulator of claim 1, wherein: the first graphene layer (3) and the second graphene layer (6) are located on two sides, respectively, the chalcogenide strip waveguide (8) is located in the middle between the first graphene layer (3) and the second graphene layer (6), and the first graphene layer (3) and the second graphene layer (6) are arranged to extend directly below the chalcogenide strip waveguide (8), and the chalcogenide strip waveguide (8) is located on the second graphene layer (6) and connected to the second graphene layer (6). 3.The hybrid waveguide integrated graphene mid-infrared electro-optic modulator of claim 1, further comprising: two via electrodes (10) connected to the first graphene layer control electrode (4) and the second graphene layer control electrode (7), respectively, and the first graphene layer control electrode (4) and the second graphene layer control electrode (7) are connected to two ends of an external voltage through the respective via electrodes (10). 4.The hybrid waveguide integrated graphene mid-infrared electro-optic modulator of claim 1, wherein: the silicon waveguide transmission layer (2), the chalcogenide medium layer (5) and the chalcogenide strip waveguide (8) form a hybrid ridge waveguide, and a TE0 mode optical signal propagates in the hybrid ridge waveguide formed by the silicon waveguide transmission layer (2), the chalcogenide medium layer (5) and the chalcogenide strip waveguide (8) and strongly interacts with the first graphene layer (3). 5.The hybrid waveguide integrated graphene mid-infrared electro-optic modulator of claim 2, wherein: the first graphene layer (3), the chalcogenide medium layer (5), the second graphene layer (6) and the control electrodes (4, 7) form a capacitor structure, the first graphene layer (3) is inductively doped by an electric field, the carrier concentration is changed by changing the light absorption rate, and the electro-optic modulation is realized. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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