Graphene-based silver nanorod-enhanced dual-core light intensity modulator

Abstract

The invention provides a graphene-based silver nanorod-enhanced dual-core light intensity modulator. The device is characterized in that it comprises a dual-core optical fiber (1), input and output port couplers (2-1) and (2-2), graphene layers (3-1 and (3-3) respectively deposited on the left and right polished optical fiber surfaces, graphene layers (3-2) and (3-4) respectively deposited on the left and right aluminum oxide film top layers, aluminum oxide films (4-1) and (4-2) as transition materials between graphenes, silver nanorods (5-1) and (5-2) on the top layers, electrode materials (6-1) and (7-2) placed at the ends and in contact with the lower graphene layers on both sides, and (6‑3), electrode materials (6‑2) and (6‑4) in contact with the upper graphene layers on both sides, two incident ports (7‑1) and (7‑2), and two exit ports (7‑3) and (7‑4). Graphene has the characteristic of adjustable carrier concentration. By connecting different voltages to the two sides respectively, different effective refractive index changes of the double cores in the polished optical fiber (8) can be achieved, and linear modulation of light intensity can be achieved through coupling at the tail port. The present invention can be widely used in the field of light intensity modulation of dual ports in optical fiber communication.

Description

(I) Technical field

[0001] The invention relates to a graphene-based silver nanocolumn-enhanced dual-core light intensity modulator, which can be used for dual-port high extinction ratio light intensity modulation and optical fiber sensing, and belongs to the technical field of optical fiber integrated devices. (II) Background technology

[0002] Optical modulators play an important role in optical communication systems due to their low insertion loss and fixed broadband characteristics. However, for most fiber optic modulators, an additional electro-optical device needs to be added to the fiber optic transmission system, which not only increases the complexity of the system, but also causes serious insertion loss. Therefore, it is necessary to realize a low insertion loss optical modulator with a simple structure. Among them, electro-optical modulators have better application prospects because they can be directly combined with electrical systems.

[0003] Graphene is a hexagonal lattice of carbon atoms, only one atom thick, and has high strength due to its chemical bonding properties. As a semiconductor, graphene has excellent optoelectronic properties due to its unique zero-bandgap structure. Graphene can be used as an active tunable material in electro-optical modulators due to its ability to interact with light, but the fixed 2.3% light absorption rate limits the application of graphene in modulators, so it is particularly important to enhance the interaction strength of graphene with light in modulators.

[0004] Patent CN 102591041 proposes a graphene film D-type fiber integrated online electro-optic modulator, in which a single-layer graphene structure is used to regulate the light field. However, due to the limited contact length between the electrode and the graphene, the required driving voltage is as high as 5V. At the same time, the single-layer graphene structure in its structure has limited effect on the light field, and the supporting structure is large and complex, resulting in poor integration.

[0005] Patent CN 108717237 A proposes a multi-layer graphene multi-output modulator based on a dual-core optical fiber. In order to overcome the weak interaction ability of single-layer graphene with light, this structure deposits multi-layer graphene and hexagonal boron nitride on the surface of the polished optical fiber to enhance the light absorption of the structure. However, multi-layer materials will bring higher system loss, and high loss will weaken the modulation performance of the coupled principle electro-optic modulator.

[0006] Patent CN 111045228 A proposes a graphene-based D-type dual-core fiber MZ modulator and its preparation method, which uses Mach-Zehnder modulation structure and double-layer graphene to regulate light. Since the motor is located on both sides, this modulator requires additional complex supporting materials, and the driving voltage is as high as 20V. At the same time, this modulator only supports single-port output.

[0007] The present invention proposes a graphene-based silver nanocolumn-enhanced dual-core light intensity modulator. First, a double-layer graphene structure is used to enhance the interaction between light and graphene, and aluminum oxide is added as a transition material to enhance the absorption of the light field. Ten silver nanocolumns are then placed tangentially above the top graphene layer to confine the light field, further enhancing the interaction between light and the modulation structure. The same modulation structure is placed above the dual core of the modulator, and different driving voltages are applied to the electrodes placed at the head and tail of both sides to achieve simultaneous modulation of the phase of light on both sides. This design offsets the phase shift of light in a single core when it enters the modulation structure, thereby achieving more accurate dual-core phase difference control to achieve a higher modulator extinction ratio. (III) Summary of the invention

[0008] The object of the present invention is to provide a double-layer graphene all-fiber light intensity modulator based on a Mach-Zehnder modulator with low insertion loss, dual-core modulation and silver nano-column assistance.

[0009] The graphene-based silver nanorod-enhanced dual-core light intensity modulator comprises a dual-core optical fiber 1, input and output port couplers (2-1) and (2-2), graphene layers (3-1) and (3-3) deposited on the left and right polished optical fiber surfaces, respectively, and graphene layers (3-2) and (3-4) deposited on the left and right aluminum oxide film surfaces, respectively, aluminum oxide films (4-1) and (4-2) as transition materials between graphenes, top silver nanorods (5-1) and (5-2), electrode materials (6-1) and (6-3) placed at the head and tail in contact with the lower graphene layers on both sides, electrode materials (6-2) and (6-4) in contact with the upper graphene layers on both sides, two incident ports (7-1) and (7-2), and two exit ports (7-3) and (7-4). In the system, light is incident from any port of the dual-core optical fiber (7-1) or (7-2), and is coupled into another fiber core in the coupler (2-1) for dual-path transmission; the middle part of the modulator is polished parallel to the direction of the dual-core arrangement to obtain a side-polished dual-core optical fiber structure; firstly, the first graphene layer (3-1) and (3-2) are deposited on the polished surface of the top of the dual core, and then the Al2O3 transition layer (4-1) and (4-2) are covered on the right and left sides respectively, and the second graphene layer (3-2) and (3-4) are deposited again on the top of the transition material, and finally the silver nanocolumn (5-1) is placed on the top of the right graphene and the silver nanocolumn (5-2) is placed on the top of the left graphene; the gold electrode (6-1) modulates the lower graphene on both sides, and (6-2) modulates the upper graphene on both sides. The electrodes placed on both sides of the head and tail can input different voltages to both sides at the same time, so that the phase difference in the dual core reaches the maximum. Traditional single-core modulation cannot achieve the best modulation effect due to the phase error when the light enters and exits the modulator, thus affecting the extinction ratio of the modulator.

[0010] A graphene-based silver nanorod-enhanced dual-core optical intensity modulator, wherein the system uses gold electrodes 6 placed at the head and tail of both sides, characterized in that the gold electrodes are placed at the head and tail of the side-cast optical fiber, wherein electrodes (6-1) and (6-3) are in contact with the lower graphene layer, and electrodes (6-2) and (6-4) are in contact with the upper graphene layer, and two driving voltages of different sizes can be input simultaneously, so that the double-layer graphene on both sides form a flat plate capacitor structure.

[0011] Silver nanopillar-enhanced dual-core light intensity modulator based on graphene. The silver nanopillars (5-1) and (5-2) used in the system are placed on the top of the modulation structure on both sides, and are characterized by: there are 10 silver nanopillars with the same radius in each row. This design of placing silver nanopillars on the top of graphene can control the light field within the modulation structure respectively, greatly enhancing the interaction between light and graphene.

[0012] In a traditional single-core modulator, there is a phase error when light enters and exits the modulation structure, so it is difficult to avoid the phase shift effect having errors with the calculation. The Mach-Zehnder-based light intensity modulator modulates the light intensity through the optical coupling in the coupler (2-2) at the end of the modulator, and the phase drift will directly affect the modulation effect. The dual-core modulator proposed in the present invention can avoid the phase error in the two cores. Simultaneous modulation of the two cores will offset the errors that occur when the light enters and exits the modulator, thereby obtaining a higher extinction ratio. (IV) Description of the drawings

[0013] Figure 1 The overall structure of the graphene-based silver nanorod-enhanced dual-core light intensity modulator, wherein 1 is a dual-core optical fiber, (2-1) and (2-2) are couplers of the incident port and the output port, (3-1) and (3-2) are the lower and upper graphene materials on the right side, (3-3) and (3-4) are the lower and upper graphene materials on the left side, (4-1) and (4-2) are aluminum oxide, which are the right and left transition materials, respectively, (5-1) and (5-2) are silver nanorods, which are the right and left sides, respectively, (6-1) and (6-2) are gold electrodes placed at the first position of the left modulation segment, (6-3) and (6-4) are gold electrodes placed at the first position of the right modulation segment, (7-1) and (7-2) are the two cores of the dual-core optical fiber incident port, (7-3) and (7-4) are the two cores of the dual-core optical fiber output port, and 8 is the modulation segment.

[0014] Figure 2 The schematic diagram of the modulator principle is shown in Figure 2. Light enters the modulator from the fiber core (7-1) and is split into two paths for transmission through the coupler (2-1). When passing through the modulation section, the light phases in the two fiber cores change differently according to different external voltages. Then, the light after the phase change enters the tail coupler (2-2) and finally exits from the tail.

[0015] Figure 3 Schematic diagram of the modulator from the front.

[0016] Figure 4 Schematic diagram of the cross section of the modulator.

[0017] Figure 5 The transmittance changes of the two ports when the chemical potential of the two layers of graphene on the upper part of one side of the fiber core is 0.4eV and the chemical potential of the graphene in the other fiber core is 0-1eV. (V) Specific implementation methods

[0018] 1) The dual-core optical fiber 1 is side-polished until half of the two cores are polished off and a concave surface is formed on the polished surface; 2) The bottom graphene (3-1) and (3-3) are respectively deposited on the polished surfaces of the two cores, and the graphene layers on both sides do not contact each other; 3) Aluminum oxide (4-1) and (4-2) are respectively deposited on the top of the graphene on both sides as transition materials for the modulation structure; 4) The second layer of graphene (3-2) and (3-4) is deposited on the top of the alumina to enhance the interaction with light; 5) Nanocolumn structures (5-1) and (5-2) are respectively placed on the top of the graphene on the left and right sides; 6) Gold electrodes are prepared at the first positions of the modulation structures on the left and right sides, and the first electrodes are respectively in contact with the lower and upper graphene layers to form a flat capacitor structure.

[0019] The dielectric constant of graphene is related to its conductivity, and its relationship with conductivity is:

[0020]

[0021] Among them, Δ represents the thickness of the graphene layer, ω is the angular frequency of light, and σ is the conductivity of graphene.

[0022]

[0023] Γ is the scattering rate, is the reduced Planck constant. The conductivity of graphene is directly related to its carrier concentration, expressed as c The magnitude of the external voltage will directly change the carrier concentration of graphene, thereby affecting its conductivity.

[0024] The change in the modulator's effective refractive index caused by changing the graphene dielectric constant will directly affect the phase of the transmitted light, and the relationship is:

[0025]

[0026] In the above formula, L is the modulator length, λ is the wavelength, Δn eff is the effective refractive index variation range of the modulator. By changing the optical phase difference in different fiber cores, the modulator has a good light intensity control effect.

Claims

1. A graphene-based silver nanorod-enhanced dual-core light intensity modulator, characterized by: It consists of a double-core optical fiber (1), input and output port couplers (2-1) and (2-2), graphene layers (3-1) and (3-3) deposited on the left and right polished optical fiber surfaces, respectively, graphene layers (3-2) and (3-4) deposited on the left and right aluminum oxide film surfaces, respectively, aluminum oxide films (4-1) and (4-2) as transition materials between graphenes, silver nanorods (5-1) and (5-2) on the top layer, gold electrodes (6-1) and (6-3) placed at the head and tail in contact with the lower graphene layers on both sides, gold electrodes (6-2) and (6-4) in contact with the upper graphene layers on both sides, two incident ports (7-1) and (7-2), and two exit ports (7-3). Light in the modulator is incident from the dual-core optical fiber port (7-1) or (7-2), and is coupled into another optical core in the coupler (2-1) for dual-path transmission; in the modulation section (8), polishing is performed in parallel to the direction of the dual-core arrangement to obtain a side-polished dual-core optical fiber structure; firstly, the first graphene layer (3-1) and (3-2) are deposited on the polished surface of the dual-core top, and then Al2O3 transition layers (4-1) and (4-2) are covered on the right and left sides respectively, and the second graphene layer (3-2) and (3-4) are deposited again on the top of the transition material, and finally, the silver nanocolumn (5-1) is placed on the top of the right graphene and the silver nanocolumn (5-2) is placed on the top of the left graphene; the gold electrode (6-1) modulates the lower graphene on both sides, and the gold electrode (6-2) modulates the upper graphene on both sides, and the electrodes placed on both sides of the head and tail can simultaneously input different voltages to both sides, so that the phase difference in the dual core reaches the maximum.

2. The graphene-based silver nanorod-enhanced dual-core light intensity modulator according to claim 1, characterized in that: The modulator places gold electrodes at the head and tail of the side-cast optical fiber, wherein the gold electrodes (6-1) and (6-3) are in contact with the lower graphene layer, and the gold electrodes (6-2) and (6-4) are in contact with the upper graphene layer. Two driving voltages of different magnitudes are input simultaneously, and the double-layer graphene on both sides form a flat-plate capacitor structure.

3. The graphene-based silver nanorod-enhanced dual-core light intensity modulator according to claim 1, characterized in that: The diameters of the silver nanorods (5-1) and (5-2) are the same, and the arrangement and spacing of the silver nanorods (5-1) and (5-2) are designed to optimize the distribution of the light field and confine the light field within the modulation structure to enhance the interaction between light and graphene.

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