CN207908828U - High speed travelling-wave electrooptic modulator based on graphene-micro-nano fiber - Google Patents

Abstract

The utility model provides a high-speed traveling-wave electro-optic modulator based on graphene-micro-nano optical fiber, including micro-nano optical fiber, top graphene, right electrode, base layer, left electrode, medium layer, and bottom graphene; The side electrode and the right electrode are traveling-wave electrodes with a coplanar band structure. On the base layer, the micro-nano fiber is placed between the top layer graphene and the bottom layer graphene, and is located in the middle of the coplanar band electrode. The dielectric layer Isolate the top graphene from the bottom graphene. The utility model has the advantages of stable operation, easy integration and low power consumption. Compared with the existing lumped graphene-micro-nano optical fiber, the traveling wave electrode in the utility model significantly improves the modulation bandwidth. Its preparation is simple, and it can be efficiently connected to a standard single-mode optical fiber communication network. Through methods such as interferometer or directional coupling, it can be widely used in light intensity modulation, and can play a huge role in the field of optical communication.

Description

High-speed traveling-wave electro-optic modulator based on graphene-micro-nano fiber

technical field

The utility model relates to the technical field of optical signal modulation, in particular to a high-speed traveling wave electro-optical modulator based on graphene-micro-nano optical fiber.

Background technique

High-performance modulators are important hardware for loading electrical signals into light waves, and have become the core of optical fiber communication networks. At present, the device size of the lithium niobate modulator using the linear electro-optical effect has reached the centimeter level, which cannot meet the requirements of on-chip integration; the speed of the silicon-based optical modulator using the plasmonic dispersion effect is mainly limited by the resistance and capacitance of the device The time constant brought by the current optical modulator is not enough for the information processing capability to meet the stringent requirements of high integration and high speed.

Graphene is a new two-dimensional material composed of multiple hexagonal network structure carbon atoms. Using its special optical, electrical, energy band characteristics and other physical properties and the mechanism of its interaction with the transmission signal light, it is possible to develop optoelectronic devices with high bandwidth and fast response speed. The theoretical value of its frequency response can reach 500GHz, and it is considered to be the most promising material for silicon-based integration.

The micro-nano optical fiber is a waveguide obtained by melting and stretching a standard single-mode optical fiber under a hydrogen-oxygen flame. It has the advantages of high mechanical strength, simple processing, strong evanescent field, high numerical aperture, and low optical transmission loss. And the micro-nano fiber can be efficiently connected with the standard single-mode fiber.

Utility model content

In order to solve the problems in the prior art, the utility model provides a high-speed traveling-wave electro-optic modulator based on graphene-micro-nano fiber, including micro-nano fiber, top graphene, right electrode, base layer, left electrode, Dielectric layer and bottom graphene; the left electrode and the right electrode are traveling wave electrodes with coplanar band structure, and on the base layer, the micro-nano fiber is placed between the top graphene and the bottom graphene, and is located in the coplanar Between the strip electrodes, the dielectric layer separates the top graphene from the bottom graphene.

As a further improvement of the utility model, the right electrode is a signal electrode, the propagation direction of the high-speed radio frequency signal is consistent with the light in the optical fiber, and the left electrode is a ground electrode.

As a further improvement of the utility model, the dielectric layer is an aluminum oxide dielectric layer with a thickness of 6nm±10%.

As a further improvement of the utility model, the base layer is a base layer of magnesium fluoride.

As a further improvement of the present invention, the top layer graphene and the bottom layer graphene are single layer graphene with a thickness of 0.7nm±10%.

As a further improvement of the present invention, the diameter of the micro-nano optical fiber is 2.2 μm±10%.

As a further improvement of the present invention, the refractive index of the base layer is 1.378.

As a further improvement of the utility model, the structural parameters of the traveling wave electrode are: the electrode thickness is 2 μm, the electrode width is 176 μm, and the electrode spacing is 12 μm. The traveling wave electrode structure is used to match the optical rate and the electrical signal rate.

The beneficial effects of the utility model are:

The high-speed traveling-wave electro-optic modulator based on graphene-micro-nano fiber uses the interaction between graphene and the evanescent field of micro-nano fiber to adjust the real part of the effective refractive index of the device by changing the Fermi level of graphene, thereby Change the phase of light to realize the modulation of light. The traveling-wave electrode structure overcomes the group velocity mismatch between the optical signal and the high-speed radio frequency signal, and improves the bandwidth.

The utility model has the advantages of stable operation, easy integration, low power consumption and large modulation bandwidth, and its preparation is simple. Compared with the existing lumped graphene/micro-nano optical fiber modulator, the modulation bandwidth is significantly improved, and can be applied to Higher-speed optical fiber communication networks can be widely used in optical intensity modulation through methods such as interferometer or directional coupling, and can play a huge role in the field of optical communication.

Description of drawings

Fig. 1 is the three-dimensional structure schematic diagram of the utility model based on graphene-micro-nano optical fiber high-speed traveling wave electro-optic modulator;

Fig. 2 is the two-dimensional cross-sectional schematic view of the utility model based on graphene-micro-nano optical fiber high-speed traveling-wave electro-optic modulator;

Fig. 3 is the relationship between the applied voltage of the graphene-micro-nano optical fiber high-speed traveling-wave electro-optic modulator of the present invention and the Fermi level and optical phase change respectively;

Fig. 4 shows the electrical bandwidth and electro-optical modulation bandwidth of the high-speed traveling-wave electro-optic modulator based on graphene-micro-nano fiber of the present invention.

Among them: 1-micro-nano fiber, 2-signal source, 3-top graphene, 4-terminal impedance, 5-right electrode, 6-base layer, 7-left electrode, 8-dielectric layer, 9-bottom graphite alkene.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is further described.

The high-speed traveling-wave electro-optic modulator based on graphene-micro-nano optical fiber of the utility model is mainly composed of graphene, micro-nano optical fiber and traveling-wave electrodes;

Wherein the structure of the high-speed traveling wave electro-optic modulator of graphene-micro-nano fiber is shown in Figure 1, the electrode material is silver metal, the left electrode 7 and the right electrode 5 adopt the coplanar strip structure; on the magnesium fluoride substrate 6, The micro-nano optical fiber 1 with a diameter of 2.2 μm is placed between the upper and lower layers of graphene, and is located in the middle of the coplanar strip electrode; the dielectric layer 8 is aluminum oxide with a thickness of 6 nm, which isolates the top layer of graphene 3 and underlying graphene9;

The dielectric layer 8 is used to form a capacitance structure for regulating the Fermi level of graphene;

Among them, the micro-nano optical fiber passes continuous signal light with a wavelength of 1550nm, and the optical input end is on the same side as the signal source end;

The effective refractive index of the device is obtained by using the interaction between micro-nano fiber and graphene. By the real part of the effective refractive index, changing the wavelength of the incident light, by the formula When the wavelength is calculated to be 1550nm, the group refractive index of the device light is 1.38;

By changing the voltage to adjust the Fermi level of graphene and change the real part of the effective refractive index, the optical phase modulation is realized. The relationship between them is shown in Figure 3.

The change of the Fermi level of graphene from 0.5eV to 0.9eV only requires a voltage of 4.95V; when realizing a π phase change, the formula It can be calculated that the minimum length of the device is 1.372 μm, and the insertion loss of the device is only 1.6 dB at this time. The applied voltage of the device is given by the formula Calculated; where V _F is the Fermi velocity, its value is 3×106m/s, ε ₀ is the dielectric constant of air, is the reduced Planck constant, and ε _r is the dielectric constant of the dielectric between the equivalent plates, and its value is 10.8.

The coplanar strip electrode structure adopts a traveling wave electrode with a terminal impedance of 50 ohms, which is connected to the other end of the electrode (corresponding to the optical output end), and the signal source is loaded on the signal input end of the electrode. The electrode structure parameters are as follows: the electrode thickness is 2 μm, the electrode width is 176 μm, and the electrode spacing is 12 μm. These electrode structure parameters better meet the traveling wave matching condition.

The frequency response of the device with the traveling wave electrode structure is shown in FIG. 4 . At this time, the speed mismatch rate is 7.38%, the characteristic impedance is 54Ω, and the microwave attenuation is 0.967dB/mm. The 3dB bandwidth of the graphene-micro-nano fiber electro-optic modulator is obtained with an analog network analyzer, and its value reaches 82GHz. It is roughly consistent with an electrical bandwidth of 6.4dB, indicating that RF and the speed of light are generally well matched.

The utility model comprises a magnesium fluoride substrate, a micro-nano optical fiber obtained by tapering treatment, a single-layer graphene, a metal silver electrode, and an aluminum oxide dielectric layer. The base material of the device is magnesium fluoride, the refractive index of which is 1.378, which is closer to the refractive index of the micro-nano optical fiber, and reduces light leakage in the Wiener optical fiber. The micro-nano fiber is laid on the magnesium fluoride substrate covered by single-layer graphene, and fixed with glue; the graphene is single-layer graphene, and the Wiener fiber is placed between the upper and lower layers of graphene; Al2O3 is used as a dielectric layer to isolate the upper and lower layers of graphene, which ensures that capacitance can be formed, and its large dielectric constant can reduce the applied voltage of the device; the silver electrode adopts a traveling wave structure, and the applied The electrical signal is then used to regulate the Fermi level of graphene.

The utility model is prepared by adopting the following technical solutions:

1) First, the single-mode optical fiber with a diameter of 125 μm is heated by a hydrogen-oxygen flame, and a stepping motor is used for tapering to obtain a micro-nano optical fiber with a diameter of about 2.2 μm;

2) transfer a single-layer graphene with a thickness of 0.7nm to a magnesium fluoride substrate using wet transfer technology;

3) Coating a layer of aluminum oxide with a thickness of 6nm on a specific area by using ultraviolet exposure and physical vapor deposition technology;

4) Then spread the tapered Wiener fiber on the substrate and fix it with glue;

5) Use EBL, ICP etching technology and physical vapor deposition technology to plate metal silver with a thickness of 2 μm, a width of 176 μm and a spacing of 12 μm as electrodes in a specific area;

6) Transfer a layer of single-layer graphene to cover the micro-nano fiber and fix it with glue.

The above content is a further detailed description of the utility model in combination with specific preferred embodiments, and it cannot be assumed that the specific implementation of the utility model is only limited to these descriptions. For a person of ordinary skill in the technical field to which the utility model belongs, without departing from the concept of the utility model, some simple deduction or substitutions can also be made, which should be regarded as belonging to the protection scope of the utility model.

Claims (8)

1. A high-speed traveling-wave electro-optic modulator based on graphene-micro-nano fiber, characterized in that it includes micro-nano fiber (1), top graphene (3), right electrode (5), and base layer (6) , the left electrode (7), the dielectric layer (8), and the bottom graphene (9); the left electrode (7) and the right electrode (5) are traveling wave electrodes with a coplanar band structure, and the base layer (6) Above, the micro-nano optical fiber (1) is placed between the top layer graphene (3) and the bottom layer graphene (9), and is located in the middle of the coplanar strip electrode, and the dielectric layer (8) isolates the top layer graphene (3) and underlying graphene (9). 2. The high-speed traveling-wave electro-optic modulator based on graphene-micro-nano fiber according to claim 1, characterized in that: the right electrode (5) is a signal electrode, and the propagation direction of high-speed radio frequency signal is the same as that of light in the fiber Consistent, the left electrode (7) is the ground electrode. 3. The high-speed traveling-wave electro-optic modulator based on graphene-micro-nano fiber according to claim 1, characterized in that: the dielectric layer (8) is an aluminum oxide dielectric layer with a thickness of 6nm±10%. 4. The high-speed traveling-wave electro-optic modulator based on graphene-micro-nano fiber according to claim 1, characterized in that: the base layer (6) is a magnesium fluoride base layer. 5. The high-speed traveling-wave electro-optic modulator based on graphene-micro-nano fiber according to claim 1, characterized in that: the top layer graphene (3) and bottom layer graphene (9) have a thickness of 0.7nm±10 % of monolayer graphene. 6. The high-speed traveling-wave electro-optic modulator based on graphene-micro-nano fiber according to claim 1, characterized in that: the diameter of the micro-nano fiber (1) is 2.2 μm±10%. 7. The high-speed traveling-wave electro-optic modulator based on graphene-micro-nano fiber according to claim 1, characterized in that: the refractive index of the base layer (6) is 1.378. 8. The high-speed traveling-wave electro-optic modulator based on graphene-micro-nano fiber according to claim 1, characterized in that: the structural parameters of the traveling-wave electrode are: the electrode thickness is 2 μm, the electrode width is 176 μm, and the electrode spacing is 12μm, using a traveling wave electrode structure to match the optical rate with the electrical signal rate.