CN209879050U

CN209879050U - Cylindrical waveguide made of graphene hyperbolic metamaterial

Info

Publication number: CN209879050U
Application number: CN201920621283.XU
Authority: CN
Inventors: 胡思敏; 许吉; 朱文武; 朱玉坤; 袁沭娟; 陆昕怡; 高彬森
Original assignee: Nanjing Post and Telecommunication University
Current assignee: Nanjing Post and Telecommunication University; Nanjing University of Posts and Telecommunications
Priority date: 2019-04-30
Filing date: 2019-04-30
Publication date: 2019-12-31
Anticipated expiration: 2029-04-30

Abstract

The utility model discloses a graphite alkene hyperbolic metamaterial cylindrical waveguide, this graphite alkene hyperbolic metamaterial cylindrical waveguide structure include two kinds of materials A, B from inside to outside, and A, B are SiO respectively₂With the graphene material, the whole waveguide structure is a sixteen-layer coaxial cylindrical structure, and the innermost layer of the cross section of the cylindrical waveguide is solid SiO₂And then from inside to outside, the graphene with 8 layers and the SiO with 7 layers are alternately arranged₂A circular ring. When light vertically enters the structure, the light field is well limited in the structure of the circular ring, so that the light-emitting diode not only has strong mode field limiting capability, but also has the characteristic of long-distance transmission, and breaks through the original polarizationThe mode realizes the restrictive transmission of radial polarized light, and the waveguide can be applied to an ultra-high density integrated optical path because of small structure size and high integration level, and has very important significance for realizing various surface plasmon devices and high-integration photon devices.

Description

Cylindrical waveguide made of graphene hyperbolic metamaterial

Technical Field

The utility model relates to a graphite alkene hyperbolic metamaterial cylindrical waveguide can be used to technical field such as terahertz wave band photonics, integrated photonic device, hyperbolic metamaterial artificial microstructure.

Background

The polarization state is one of the important characteristics of light, and the vector characteristic of the light makes the light and a substance have complicated interaction, so that various optical devices and optical systems can be manufactured. Past research has been directed primarily to spatially uniform polarization states, such as linear polarization, circular polarization, and the like, for which the polarization state is not dependent on the spatial position of the beam. With the deep exploration of optics, the vector beam with the spatially non-uniform polarization distribution is discovered. The polarization state of the vector light beam changes along with the change of the space, and the characteristic causes the vector light beam to have a plurality of new effects and phenomena, thereby well expanding the functions of the optical system. The special vector beams are Column Vector Beams (CVBs) with polarization states in column symmetric distribution on the cross section in the beam propagation direction, and can be divided into radial polarized light, spin polarized light and general column vector beams according to the distribution characteristics of an electric field of the CVB in space.

In recent decades, especially in the field of photonic integration, many surface plasmon waveguide structures that can confine an optical field to a nanometer scale have been proposed in succession, such as a dielectric-metal-dielectric waveguide structure, a metal-dielectric-metal waveguide structure, a metal slit structure, a V-groove waveguide structure, and the like. The dielectric constant of the graphene hyperbolic metamaterial in a near infrared to terahertz waveband is less than 0, the graphene hyperbolic metamaterial can be used for replacing metal to serve as a composition material of HMMs, and the thickness of single-layer graphene is only about 0.335nm, so that the formed HMMs have smaller periodic units and lower loss. However, at present, the graphene-dielectric multilayer film structure mostly appears in a plane, and the cylindrical vector beam distribution of the cylindrical waveguide is not realized.

Disclosure of Invention

The utility model aims at solving the above-mentioned problem that exists among the prior art, provide a graphite alkene hyperbolic metamaterial cylindrical waveguide.

The purpose of the utility model can be realized through the following technical scheme: a graphene hyperbolic metamaterial cylindrical waveguide is a coaxial cylindrical structure and comprises two materials A and B from inside to outside, wherein the A and the B are respectively SiO₂With graphene material, the innermost layer of the cross section of the cylindrical waveguide is solid SiO₂And then from inside to outside are n layers of graphene and n-1 layers of SiO which are alternately arranged₂Circular ring, innermost solid SiO₂The radius of the cylinder is r, the thickness of each graphene ring layer is dg, and each SiO layer₂The thickness of the ring is dd.

Preferably, the SiO₂Has a dielectric constant of 2.2, and the dielectric constant of the corresponding graphene is epsilon under the incidence of light with a wavelength of 30 mu m_m-1334.4-42.774i, the tangential dielectric constant epsilon of graphene_mt＝-1335.6-42.774i。

Preferably, the coaxial cylindrical structure has 16 layers in total, and the innermost layer of the cross section of the cylindrical waveguide is solid SiO₂And then from inside to outside, the graphene with 8 layers and the SiO with 7 layers are alternately arranged₂A circular ring.

Preferably, the innermost layer is SiO₂The radius of the cylinder is r 114 nm.

Preferably, the thickness of each layer of graphene ring is dg-1 nm.

Preferably, each layer of SiO₂The thickness of the ring is dd 19 nm.

The utility model adopts the above technical scheme to compare with prior art, have following technological effect: the cylindrical waveguide structure is used for replacing the original plane structure and is designed into a cylindrical symmetrical structure for regulating and controlling the radial polarized light which is symmetrical to the cylindrical waveguide structure. When light vertically enters the structure, the light field is well limited in the structure of the circular ring, so that the waveguide not only has very strong mode field limiting capacity, but also has the characteristic of long-distance transmission, breaks through the original polarization mode, realizes the limiting transmission of radial polarized light, and has very important significance for realizing various surface plasmon devices and high-integration-level photonic devices because the waveguide has small structure size and high integration level, and can be applied to ultrahigh-density integrated optical paths.

(1) The utility model discloses a restricted transmission of radial polarized light has broken through prior art's polarization state limitation.

(2) The utility model discloses have the high refracting index, have stronger light field limiting power, can limit the light field in the waveguide structure.

(3) The utility model discloses compact structure, structural dimension is little, and the photon of consequently being convenient for is integrated, can be applied to super high density integrated optical path, makes integrated photonic device.

(4) The utility model discloses because graphite alkene is adjustable, structural dimension is adjustable, through rational design, can realize long distance propagation.

Drawings

Fig. 1 is the utility model discloses embodiment graphite alkene hyperbolic metamaterial cylindrical waveguide structure cross-sectional schematic diagram.

Fig. 2 is a distribution diagram of the surface electric field mode | E | of the radial polarization optical waveguide mode with a wavelength λ ═ 30 μm according to an embodiment of the present invention.

Fig. 3 is a distribution curve of the surface electric field mode | E | along the cross-sectional diameter of the waveguide in the radial polarization optical waveguide mode with the wavelength λ being 30 μm according to the embodiment of the present invention.

Fig. 4 is a polarization distribution diagram of a radial polarization optical waveguide mode with a wavelength λ of 30 μm according to an embodiment of the present invention, and arrows indicate radial polarization states.

FIG. 5 shows the real part n of the effective refractive index of the radially polarized optical waveguide mode with a wavelength λ of 30 μm according to an embodiment of the present invention_{eff_r}And an imaginary effective index n_{eff_i}With innermost SiO layer₂And (4) a radius change relation graph.

Detailed Description

Objects, advantages and features of the present invention will be illustrated and explained by the following non-limiting description of preferred embodiments. These embodiments are merely exemplary embodiments for applying the technical solutions of the present invention, and all technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the scope of the present invention.

The utility model discloses a graphite alkene hyperbolic metamaterial cylindrical waveguide, this graphite alkene hyperbolic metamaterial cylindrical waveguide be a high integration, high refracting index, propagation distance is long, can realize the adjustable cylindrical waveguide of radial polarized light restrictive transmission.

As shown in FIG. 1, the graphene hyperbolic metamaterial cylindrical waveguide comprises A, B two materials, A, B is SiO respectively₂With the graphene material, the whole waveguide structure is a sixteen-layer coaxial cylindrical structure. FIG. 1 is a white part of SiO₂Due to graphene versus SiO₂The layers are thin, indicated by the solid lines. The innermost layer of the cross section of the cylindrical waveguide is solid SiO₂And then from inside to outside are n layers of graphene and n-1 layers of SiO which are alternately arranged₂A circular ring. Solid SiO of innermost layer₂The radius of the cylinder is r, the thickness of each graphene ring layer is dg, and each SiO layer₂The thickness of the ring is dd. In this embodiment, the innermost layer is solid SiO₂The radius of the cylinder is r 114nm, the thickness of each layer of graphene ring is dg 1nm, and each layer of SiO₂The thickness of the ring is dd ═ 19nm, and the total thickness of the ring is 8 layers of graphene and 7 layers of SiO from inside to outside₂The rings are arranged alternately, and the radius of the whole waveguide is 255 nm.

In this example, SiO was selected₂Hyperbolic metamaterial with graphene, wherein SiO₂Has a dielectric constant of 2.2, and the dielectric constant of the corresponding graphene is epsilon under the incidence of light with a wavelength of 30 mu m_m-1334.4-42.774i, the tangential dielectric constant epsilon of graphene_mt＝-1335.6-42.774i。

Light with the wavelength of 30 microns is selected to be incident, a light field is well limited in a waveguide structure, limited transmission of radial polarized light can be achieved besides linear polarized light, and the transmission distance is long under the condition that the structure is compact.

The propagation distance L is defined as the distance when the electric field intensity on any interface decays to the initial value 1/e, and the expression is as follows:

L＝1/(k₀n_{eff_i})＝λ/(2πn_{eff_i})

wherein k is₀Is the wave vector in vacuum, n_{eff_i}Is the imaginary part of the mode effective index of the waveguide.

The real part of the mode effective index reflects the mode confinement capability in a cylindrical waveguide structure, while the magnitude of the imaginary part determines the magnitude of the transmission loss as it propagates in the waveguide.

Further, at 30 μm wavelength radial polarized light incidence, the radius of the cylindrical waveguide is 255nm, and the mode effective refractive index n of the waveguide_eff18.909-0.32198i, where the real part n of the mode effective index_{eff_r}18.909 is higher, the high index of refraction reflects a stronger mode confinement capability; imaginary part n of the mode effective index_{eff_i}At 0.32198, the propagation distance of the mode can be calculated to be 14.83 μm, i.e., long distance propagation can be achieved.

Furthermore, as the polarization modes supported by the column symmetric structure are more, the regulation and control of the radial polarized light of the column symmetry are facilitated, and meanwhile, as the graphene is a material with high adjustability, the dielectric constant and other related parameters of the graphene can be changed by regulating the chemical potential, the temperature and the wavelength of incident light of the graphene; can also be realized by changing the SiO of the innermost layer₂Radius r or change of graphene rings and SiO₂The number of cycles of the ring is optimized.

FIG. 2 is a radial polarized optical waveguide mode | E | profile for an embodiment having a wavelength λ of 30 μm, where the innermost layer is solid SiO₂The radius of the cylinder is r 114nm, the thickness of each layer of graphene ring is dg 1nm, and each layer of SiO₂The thickness of the ring is dd ═ 19nm, and the total thickness of the ring is 8 layers of graphene and 7 layers of SiO from inside to outside₂The rings are arranged alternately, and the radius of the whole waveguide is 255 nm. The distribution of the optical field is reflected by the density and distribution of the contour lines, and it can be seen that the optical field is mainly confined in the waveguide structure and distributed equivalently on the circumference under the incidence of light with the wavelength of 30 μm.

FIG. 3 is a radial polarized waveguide mode | E | with a wavelength λ of 30 μm along the diameter of the waveguide cross section according to an embodiment, and it can be seen that the waveguideThe surface electric field mode in the structure is far higher than that outside the waveguide structure and also far higher than that of the innermost SiO layer₂Cylindrical surface electric field mode, therefore the optical field is considered to be confined in the waveguide structure and mainly concentrated on graphene and SiO₂A periodically arranged portion.

Fig. 4 shows polarization distribution of a radial polarization optical waveguide mode with a wavelength λ of 30 μm in the embodiment, where arrows indicate radial polarization states, and when the wavelength of a transmission optical signal is 30 μm, it can be seen from the figure that the vibration direction of an electric field of radial polarization light is along the radial direction, so that limited transmission of radial polarization light is realized, and the limitation of the original polarization mode is broken through.

FIG. 5 shows the real part of the effective refractive index n of the radially polarized optical waveguide mode with the wavelength λ of 30 μm according to the embodiment_{eff_r}And an imaginary effective index n_{eff_i}With innermost SiO layer₂Radius r change relation graph. As can be seen, SiO is present in the innermost layer of the film₂At radius r, the real part and the imaginary part of the effective refractive index of the mode are reduced and then increased along with the increase of r, and the real part n of the effective refractive index of the mode_{eff_r}The minimum value is still larger than 18.5, the refractive index is high, the mode limiting capability is strong, and the effective refractive index imaginary part n_{eff_i}Substantially less than 0.336, a longer propagation distance can be obtained by calculation. As can be seen, the optimal adjustment of the mode effective refractive index can be realized by adjusting the magnitude of r.

Under the incidence of light with the wavelength of 30 microns, the waveguide structure can limit an optical field in a structural region, further narrow the distribution range of the optical field and realize the limited transmission of radial polarized light. The structure has small size and high integration level, has the characteristics of high refractive index and long propagation distance, and can realize the optimization of optical field distribution and refractive index by changing the structure radius and the number of layers or adjusting related parameters of graphene. The utility model discloses a can be applied to super high density integrated optical path, for realizing that the super high integrated level provides probably in integrated photonic device field, have certain using value in integrated optics field, metamaterial artificial microstructure field.

The utility model has a plurality of implementation modes, and all technical schemes formed by adopting equivalent transformation or equivalent transformation all fall within the protection scope of the utility model.

Claims

1. The utility model provides a graphite alkene hyperbolic metamaterial cylindrical waveguide which characterized in that: the graphene hyperbolic metamaterial cylindrical waveguide structure is a coaxial cylindrical structure and comprises two materials A and B from inside to outside, wherein the A and the B are respectively SiO₂With graphene material, the innermost layer of the cross section of the cylindrical waveguide is solid SiO₂And then from inside to outside are n layers of graphene and n-1 layers of SiO which are alternately arranged₂Circular ring, innermost solid SiO₂The radius of the cylinder is r, the thickness of each graphene ring layer is dg, and each SiO layer₂The thickness of the ring is dd.

2. The graphene hyperbolic metamaterial cylindrical waveguide of claim 1, wherein: the SiO₂Has a dielectric constant of 2.2, and the dielectric constant of the corresponding graphene is epsilon under the incidence of light with a wavelength of 30 mu m_m-1334.4-42.774i, the tangential dielectric constant epsilon of graphene_mt＝-1335.6-42.774i。

3. The graphene hyperbolic metamaterial cylindrical waveguide of claim 1, wherein: the coaxial cylindrical structure has 16 layers in total, and the innermost layer of the cross section of the cylindrical waveguide is solid SiO₂And then from inside to outside, the graphene with 8 layers and the SiO with 7 layers are alternately arranged₂A circular ring.

4. The graphene hyperbolic metamaterial cylindrical waveguide of claim 1, wherein: the innermost solid SiO layer₂The radius of the cylinder is r 114 nm.

5. The graphene hyperbolic metamaterial cylindrical waveguide of claim 1, wherein: the thickness of each layer of graphene ring is dg-1 nm.

6. The graphene hyperbolic metamaterial cylindrical waveguide of claim 1, wherein: each layerSiO₂The thickness of the ring is dd 19 nm.