阅读说明：本技术 一种基于类狄拉克点的负折射率波导快光器件及设计方法 (Dirac-like point-based negative-refractive-index waveguide fast optical device and design method ) 是由 卓立强 赵泽阳 何真 邱伟彬 于 2019-11-29 设计创作，主要内容包括：一种基于类狄拉克点的负折射率波导快光器件及设计方法,负折射率波导快光器件包括由设置在硅板上的多个三角晶格光子晶体组成的具有负折射率的上包层和下包层；还包括设置在所述上包层和下包层之间的以硅为介质组成的芯层；所述上包层和下包层的上边界、下边界、左边界和右边界为散射边界条件,入射光从所述芯层的一侧入射,从所述芯层的另一侧出射。本发明利用类狄拉克点附近频率可使光子晶体的有效折射率为负的特性,通过控制入射光的频率和芯层厚度,实现包层的负折射率,并使得光在芯层中具有负群速度,以及反向传播的行为。(A negative refractive index waveguide fast optical device based on Dirac-like points and a design method thereof are provided, wherein the negative refractive index waveguide fast optical device comprises an upper cladding and a lower cladding which are composed of a plurality of triangular lattice photonic crystals and arranged on a silicon plate and have negative refractive index; the core layer which is arranged between the upper cladding layer and the lower cladding layer and consists of silicon as a medium is further included; and the upper boundary, the lower boundary, the left boundary and the right boundary of the upper cladding and the lower cladding are scattering boundary conditions, and incident light enters from one side of the core layer and exits from the other side of the core layer. The invention utilizes the characteristic that the effective refractive index of the photonic crystal can be negative by using the frequency near the Dirac-like point, realizes the negative refractive index of the cladding by controlling the frequency of incident light and the thickness of the core layer, and ensures that light has negative group velocity and backward propagation behavior in the core layer.)

1. A negative refractive index waveguide fast optical device based on Dirac-like points is characterized in that: comprises an upper cladding and a lower cladding with negative refractive index composed of a plurality of triangular lattice photonic crystals arranged on a silicon plate; the core layer which is arranged between the upper cladding layer and the lower cladding layer and consists of silicon as a medium is further included; and the upper boundary, the lower boundary, the left boundary and the right boundary of the upper cladding and the lower cladding are scattering boundary conditions, and incident light enters from one side of the core layer and exits from the other side of the core layer.

2. The dirac-like point based negative refractive index waveguide fast light device of claim 1, wherein the triangular lattice photonic crystal is a hollow air dielectric cylinder, forming a triangular lattice core-shell photonic crystal structure.

3. The dirac-like point-based negative refractive index waveguide fast light device of claim 2, wherein the hollow air dielectric pillars are periodically distributed in a silicon medium.

4. The dirac-like point based negative refractive index waveguide fast optical device according to claim 1, wherein the width of the negative refractive index waveguide fast optical device can be increased or decreased, i.e. the number of the air dielectric pillars can be increased or decreased, while the photonic crystal structure and boundary conditions are kept unchanged.

5. A design method of Dirac-like point based negative refractive index waveguide fast optical device as claimed in any one of claims 1 to 4, comprising:

s101, calculating an energy band structure of the core-shell photonic crystal;

s102, adjusting the duty ratio of an air medium column in the core-shell structure photonic crystal to realize a Dirac-like point at the center of the Brillouin zone;

s103, calculating the effective dielectric constant and the effective magnetic permeability of the photonic crystal by using the energy band structure;

s104, constructing an upper cladding and a lower cladding of the triangular lattice photonic crystal on a silicon plate according to the duty ratio of the air medium column of the Dirac-like point, reserving a core layer with a preset thickness in the middle of the silicon plate, wherein the upper boundary, the lower boundary, the left boundary and the right boundary of the upper cladding and the lower cladding are scattering boundary conditions, and incident light enters from one side of the core layer and exits from the other side of the core layer.

6. The design method of the Dirac-like point based negative refractive index waveguide fast optical device according to claim 5, wherein the duty cycle of the air dielectric cylinder is calculated as follows:

f＝(r1-r2)/a

where f denotes the duty cycle, r1 denotes the outer radius of the column of air dielectric, r2 denotes the inner radius of the shell column of air dielectric, and a denotes the lattice constant.

7. The design method of the dirac-like point-based negative refractive index waveguide fast optical device according to claim 5, wherein the effective dielectric constant and the effective permeability are calculated as follows:

wherein epsilon_effRepresents the effective dielectric constant of the photonic crystal; mu.s_effRepresents the effective permeability of the photonic crystal; k is a radical of_yA y component representing a wave vector; ω represents angular frequency; epsilon₀Represents the vacuum dielectric constant; mu.s₀Represents the vacuum permeability; e_xRepresents the average value of the intrinsic electric field along the x-axis direction; h_zRepresents the average value of the intrinsic magnetic field in the z-axis direction.

8. The design method of the dirac-like point based negative refractive index waveguide fast optical device according to claim 5, further comprising, after the step S104:

and S105, simulating the constructed photonic crystal waveguide through software, and carrying out simulation analysis on the photonic crystal waveguide to obtain a simulation result of the designed negative-refractive-index waveguide fast optical device.

9. The design method of the dirac-like point based negative refractive index waveguide fast optical device according to claim 8, wherein the simulation analysis in S105 adopts a finite element numerical method.

Technical Field

The invention relates to a microstructure photonic crystal element, in particular to a Dirac-like point-based negative refractive index waveguide fast optical device and a design method thereof.

Background

The photonic crystal is an artificially synthesized material with different media periodically distributed in space, and as the lattice constant and the working wavelength of the photonic crystal are on an order of magnitude, the photonic crystal-based fast optical device is easier to realize high integration and adapts to the development trend of photoelectric integration.

Waveguide devices play an important role in optical communication systems, and are essential to avoid loss caused by absorption and scattering of a medium and divergence caused by diffraction when a light beam is transmitted in the medium, so that the intensity of the central part of the light beam is continuously attenuated, and to ensure that the energy of the light beam is limited in the longitudinal direction during propagation, so that the light beam can be transmitted in a concentrated manner in a core layer, and loss and noise are minimized. Currently, negative index waveguides can be constructed from an effective dielectric constant ε_effAnd effective permeability mu_effConstructed of negative left-handed materials (LHMs) (Taya S A, Qadoura I M. guided modes in slab ways with negative index binding and substrate [ J]optical-International Journal for Light and electronic Optics,2013,124(13): 1431-1436), and the negative index waveguide can achieve anomalous dispersion phenomena, which in turn leads to fast Light phenomena (i.e. negative group velocity) (Zhang Y, Zhang X, Wang Y, et al. reversible Fano restriction by transmittance from fast Light to slow Light in a coupled-restricted-transmitted structure [ J]Opticsexpress,2013,21(7): 8570-. In recent years, light pulses can be realized by controlling the group velocity of fast light (Lezama A, Akulshin A M, Sidorov A I, et al]Physical Review A,2006,73(3):033806.), and propagation of entangled state quantum mutual information (Clark J B, glass R T, glass Q, et]Nature Photonics,2014,8(7): 515), and the like. But due to the effective dielectric constant epsilon of the material_effAnd effective permeability mu_effIn general, the negative refractive index waveguide is a specific value, so that the function of the negative refractive index waveguide is limited, and the negative refractive index waveguide is not convenient in practical application.

Disclosure of Invention

The main purpose of the present invention is to overcome the above-mentioned defects in the prior art, and to provide a kind of negative refractive index waveguide fast optical device based on dirac-like point and its design method, which realizes anomalous dispersion and backward propagation of light by controlling the frequency of incident light.

The invention adopts the following technical scheme:

on one hand, the invention relates to a Dirac-like point-based negative-refractive-index waveguide fast optical device, which comprises an upper cladding and a lower cladding, wherein the upper cladding and the lower cladding are composed of a plurality of triangular lattice photonic crystals arranged on a silicon plate and have negative refractive indexes; the core layer which is arranged between the upper cladding layer and the lower cladding layer and consists of silicon as a medium is further included; and the upper boundary, the lower boundary, the left boundary and the right boundary of the upper cladding and the lower cladding are scattering boundary conditions, and incident light enters from one side of the core layer and exits from the other side of the core layer.

Preferably, the triangular lattice photonic crystal is a hollow air dielectric column, and a triangular lattice core-shell photonic crystal structure is formed.

Preferably, the hollow air dielectric columns are periodically distributed in the silicon dielectric.

Preferably, the width of the negative refractive index waveguide fast optical device can be increased or decreased on the premise of keeping the photonic crystal structure and the boundary condition unchanged, namely, the number of the air dielectric columns can be increased or decreased.

In another aspect, a method for designing a dlac-like negative refractive index waveguide fast optical device includes:

s101, calculating an energy band structure of the core-shell photonic crystal;

s102, adjusting the duty ratio of an air medium column in the core-shell structure photonic crystal to realize a Dirac-like point at the center of the Brillouin zone;

s103, calculating the effective dielectric constant and the effective magnetic permeability of the photonic crystal by using the energy band structure;

s104, constructing an upper cladding and a lower cladding of the triangular lattice photonic crystal on a silicon plate according to the duty ratio of the air medium column of the Dirac-like point, reserving a core layer with a preset thickness in the middle of the silicon plate, wherein the upper boundary, the lower boundary, the left boundary and the right boundary of the upper cladding and the lower cladding are scattering boundary conditions, and incident light enters from one side of the core layer and exits from the other side of the core layer.

Preferably, the duty cycle of the air media column is calculated as follows:

f＝(r1-r2)/a

where f denotes the duty cycle, r1 denotes the outer radius of the column of air dielectric, r2 denotes the inner radius of the shell column of air dielectric, and a denotes the lattice constant.

Preferably, the method for calculating the effective dielectric constant and the effective permeability comprises the following steps:

wherein epsilon_effRepresents the effective dielectric constant of the photonic crystal; mu.s_effRepresents the effective permeability of the photonic crystal; k is a radical of_yA y component representing a wave vector; ω represents angular frequency; epsilon₀Represents the vacuum dielectric constant; mu.s₀Represents the vacuum permeability; e_xRepresents the average value of the intrinsic electric field along the x-axis direction; h_zRepresents the average value of the intrinsic magnetic field in the z-axis direction.

Preferably, after S104, the method further includes:

and S105, simulating the constructed photonic crystal waveguide through software, and carrying out simulation analysis on the photonic crystal waveguide to obtain a simulation result of the designed negative-refractive-index waveguide fast optical device.

Preferably, the method used in the simulation analysis in S105 is a finite element numerical method.

As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following advantages:

the waveguide fast light device comprises an upper package with negative refractive index composed of a plurality of triangular lattice core-shell photonic crystals arranged on a silicon plateA layer and a lower cladding layer; the core layer which is arranged between the upper cladding layer and the lower cladding layer and consists of silicon as a medium is further included; by controlling the frequency of the incident light, the effective dielectric constant epsilon around the Dirac-like point frequency is utilized_effAnd effective permeability mu_effLinear with the incident light frequency, so that light has a negative group velocity in the core layer, and anomalous dispersion and backward propagation of light are achieved.

Drawings

FIG. 1 is a diagram of a Dirac-like point based negative index waveguide fast light device of the present invention;

FIG. 2 is a diagram of the band structure of a triangular lattice core-shell photonic crystal of the present invention;

FIG. 3 is a light field distribution diagram of three degenerate modes at a Dirac-like point of the present invention;

FIG. 4 is a graph of the effective dielectric constant ε of a triangular lattice core-shell photonic crystal of the present invention_effAnd effective permeability mu_eff；

Fig. 5 is a graph of simulation results of the negative index waveguide fast optical device of the present invention.

Detailed Description

The invention is further described below by means of specific embodiments.

Referring to fig. 1, in one aspect, the present invention relates to a dirac-like point based negative refractive index waveguide fast optical device, which comprises an upper cladding 30 and a lower cladding 40 having a negative refractive index, which are composed of a plurality of triangular lattice photonic crystals 20 disposed on a silicon plate 10; the silicon-based composite material further comprises a core layer 50 which is arranged between the upper cladding layer and the lower cladding layer and is composed of silicon as a medium; the upper, lower, left, and right boundaries of the upper and lower claddings 30 and 40 are scattering boundary conditions, and incident light enters from one side of the core layer 50 and exits from the other side of the core layer 50.

The triangular lattice photonic crystal 20 is a hollow air dielectric column, and forms a triangular lattice core-shell photonic crystal structure.

The hollow air dielectric columns are periodically distributed in the silicon dielectric.

The width of the negative refractive index waveguide fast optical device can be increased or reduced on the premise of keeping the photonic crystal structure and the boundary condition unchanged, namely the number of the air dielectric columns can be increased or reduced.

On the other hand, the invention also discloses a design method of the negative refractive index waveguide fast optical device, which comprises the following steps:

s101, constructing a triangular lattice core-shell (core-shell) photonic crystal (air dielectric columns are periodically distributed in silicon) model by utilizing Comsol Multiphysics based on a finite element method, setting Floquet periodic boundary conditions for the boundary of an original cell (photonic crystal minimum periodic unit), applying an electromagnetic field of a TE mode, and calculating the energy band structure of the boundary of a region surrounded by high symmetry points (M-gamma-K-M) in Brillouin Zone (Brillouin Zone), namely finally calculating the energy band structure of the triangular lattice core-shell (core-shell) photonic crystal (air dielectric columns are periodically distributed in silicon);

s102, adjusting the duty ratio f of an air medium column in the triangular lattice core-shell photonic crystal (the duty ratio f of the air medium column is (r1-r2)/a, r1 represents the outer radius of the air medium column, r2 represents the inner radius of the air medium column, and a represents a lattice constant), and realizing a Dirichlet-like point at the center of the Brillouin zone; as shown in fig. 2, when the lattice constant a is 1um, the outer radius r1 of the dielectric shell column is 0.42a, and the outer radius r2 of the dielectric shell column is 0.1781a, a dirac-like point appears at the center of the brillouin zone, and the frequency thereof is 171.85THz (-1.7457 um), and (a) - (c) in fig. 3 are the optical field distributions of three degenerate modes at the dirac-like point;

s103, calculating the effective dielectric constant epsilon by using the data derived by calculating the energy band_effAnd effective permeability mu_effThe following are:

wherein epsilon_effRepresents the effective dielectric constant of the photonic crystal; mu.s_effRepresenting photonsThe effective permeability of the crystal; k is a radical of_yA y component representing a wave vector; ω represents angular frequency; epsilon₀Represents the vacuum dielectric constant; mu.s₀Represents the vacuum permeability; e_xRepresents the average value of the intrinsic electric field along the x-axis direction; h_zRepresents the average value of the intrinsic magnetic field in the z-axis direction.

Effective dielectric constant ε_effAnd effective permeability mu_effThe calculation results of (2) are shown in fig. 4.

S104, constructing an upper cladding and a lower cladding of the triangular lattice photonic crystal on a silicon plate according to the duty ratio f of the air medium column of the Dirac-like point, reserving a core layer with a preset thickness in the middle of the silicon plate, wherein the upper boundary, the lower boundary, the left boundary and the right boundary of the upper cladding and the lower cladding are scattering boundary conditions, and incident light enters from one side of the core layer and exits from the other side of the core layer. The width of the negative refractive index waveguide fast optical device can be increased or decreased on the premise of keeping the photonic crystal structure and the boundary condition unchanged, namely the number of the air dielectric columns can be increased or decreased, and the designed negative refractive index waveguide is shown in FIG. 1;

and S105, simulating the constructed photonic crystal negative refractive index waveguide through software, and performing simulation analysis on the photonic crystal negative refractive index waveguide by adopting a finite element numerical method to obtain a simulation result of the designed negative refractive index waveguide fast optical device. Referring to fig. 5, (a) is incident light having a frequency of 154THz, which is incident from a core layer having a thickness d of 4.5 μm, when the refractive indices of the upper and lower clad layers are negative, light has a negative group velocity in the core layer, and travels in the reverse direction; (b) incident light having a frequency of 176THz is incident on the core layer having a thickness d of 2.5 μm, and the refractive indices of the upper and lower clad layers are positive, so that light propagates in the core layer in the forward direction.

The above description is only an embodiment of the present invention, but the design concept of the present invention is not limited thereto, and any insubstantial modifications made by using the design concept should fall within the scope of infringing the present invention.