CN2842451Y - Polarization beam splitter based on photon crystal positive-negative refraction - Google Patents

Abstract

A polarizing beam splitter based on photonic crystal positive and negative refraction. A two-dimensional periodic array of air pillars in the dielectric material on the substrate, or an array of metal pillars, or another dielectric material pillar array constitutes a photonic crystal; or a two-dimensional periodic array of metal pillars on the substrate Or an array of dielectric material pillars constitutes a photonic crystal. After the incident electromagnetic wave beam is incident from the environmental interface, one experiences negative refraction on the environmental interface, and the incident electromagnetic wave beam and the refracted electromagnetic wave beam are on the same side of the normal line between the photonic crystal and the environmental interface; the other experiences positive refraction on the environmental interface, and the incident electromagnetic wave beam The wave beam and the refracted electromagnetic wave beam are respectively located on both sides of the normal line, and the electromagnetic wave beams of the two polarization states are separated to realize polarization beam splitting. The utility model realizes polarization splitting by using photonic crystals, and the electromagnetic wave beams of two polarization states work in the transmission mode, has the advantages of small size, easy integration, simple process, etc., and can be used in microwave and optical bands.

Description

Polarizing Beam Splitter Based on Positive and Negative Refraction of Photonic Crystals

technical field

The utility model relates to a polarization beam splitter, in particular to a polarization beam splitter based on positive and negative refraction of photonic crystals.

Background technique

Photonic Crystal (Photonic Crystal) is an artificial periodic structure [J.D.Joannopoulos, Photonic crystals: Molding the flow of light, Princeton, 1995], using dielectric materials such as alumina, silicon dioxide, silicon, gallium arsenide, The two-dimensional periodic structure made of indium phosphide can also be a two-dimensional periodic distribution of metal pillar arrays in the dielectric background. The two-dimensional periodicity means that the line connecting the centers of any three adjacent pillars in the array forms a square lattice of isosceles right triangles, or a triangular lattice of equilateral triangles. The length of the shortest line is called the lattice constant. Because microwaves and light waves are both electromagnetic waves, and their behaviors also follow the Maxwell equation, photonic crystals can be applied in both microwave and light bands, but the sizes of the two bands are different.

For ordinary materials, what happens to the electromagnetic beam at the interface of different materials is positive refraction, that is, the incident wave [such as photonic crystal, M. Phys.Rev.B 62, 10696, 2000] At the interface with the surrounding environment (such as ordinary materials or air), the electromagnetic beam can be negatively refracted, that is, the incident beam and the refracted beam are on the same side of the interface normal.

Literature [S.Kim, Opt.Lett.28, 2384, 2003] designed a polarization beam splitter by using the different positions of the forbidden bands of different polarization states of photonic crystals, that is, the electromagnetic beam of one polarization state can pass through the photonic crystal, The electromagnetic beam of the other polarization state is reflected. Literature [X.Y.Chen, Chinese Phys.Lett.21, 1285, 2004] designed a photonic crystal line defect Y-shaped branch waveguide, one branch waveguide transmits electromagnetic waves of one polarization state and reflects electromagnetic waves of another polarization state, and the other branch waveguide the other way around.

Contents of the invention

The purpose of the utility model is to provide a polarization beam splitter based on positive and negative refraction of photonic crystals.

The technical scheme that the utility model adopts is:

1. Polarizing beam splitters based on positive and negative refraction of photonic crystals have two structural forms:

1) A two-dimensional periodic array of air pillars, or a metal pillar array, or another dielectric material pillar array in the dielectric material on the substrate constitutes a photonic crystal.

2) A photonic crystal is composed of a two-dimensional periodic array of metal pillars or dielectric material pillars on the substrate.

The two-dimensional periodicity means that the line connecting the centers of any three adjacent pillars in the array forms a square lattice of isosceles right triangles, or a triangular lattice of equilateral triangles.

The shape of the array is rectangle or triangle.

2. Polarization beam splitting method based on positive and negative refraction effects of photonic crystals: Rectangular or triangular photonic crystals are used as polarization beam splitting elements of electromagnetic waves. The incident electromagnetic wave beam contains two polarization states. After incident from the environmental interface, one of the polarization states The electromagnetic beam of the polarization state experiences negative refraction on the interface of the environment, and the incident electromagnetic wave beam and the refracted electromagnetic wave beam are on the same side of the normal line of the photonic crystal and the environment interface; the electromagnetic wave beam of the other polarization state experiences positive refraction on the photonic crystal and the environment interface, and the incident electromagnetic wave beam The electromagnetic wave beam and the refracted electromagnetic wave beam are respectively located on both sides of the normal line, so as to separate the electromagnetic wave beams of the two polarization states and realize polarization beam splitting.

The included angle between the incident electromagnetic wave beam and the normal is 10°-80°.

The beneficial effects of the utility model are: the device uses photonic crystals to realize polarization splitting, and the electromagnetic beams of the two polarization states work in the transmission mode. It has the advantages of small size, easy integration, simple process, etc., and can be used in microwave and light bands.

Description of drawings

Fig. 1 is a schematic diagram of the structure and principle of a planar photonic crystal polarization beam splitter composed of a pillar array in a dielectric material;

Fig. 2 is A-A sectional view of Fig. 1;

Fig. 3 is a schematic diagram of the structure and principle of a triangular polarizing beam splitter;

Fig. 4 is a schematic diagram of the structure and principle of a planar photonic crystal polarization beam splitter composed of a column array in the air;

Fig. 5 is the B-B sectional view of Fig. 4;

Fig. 6 is a schematic diagram of photonic crystal energy band structure characteristics;

Figure 7 is the energy band structure of a photonic crystal composed of silver cylinder arrays arranged in a triangular lattice in alumina. The black circles represent TE polarization, and the black squares represent TM polarization;

Fig. 8 is the energy band structure of a photonic crystal composed of a gallium arsenide cylindrical array arranged in a triangular lattice in air, (a) TE polarization, (b) TM polarization.

In the figure: 1. Flat plate shape, 2. Triangular shape, 3. Incident electromagnetic wave beam, 4. Refracted electromagnetic wave beam, 5. Refracted electromagnetic wave beam, 6. Environmental interface, 7. Normal line, 8. Dielectric material, 9. Substrate , 10. Dielectric material pillar array.

Detailed ways

As shown in FIG. 1 and FIG. 2 , a two-dimensional periodic array of air pillars, or a metal pillar array, or another dielectric material pillar array in the dielectric material 8 on the substrate 9 constitutes a photonic crystal.

As shown in FIG. 4 and FIG. 5 , a two-dimensional periodic arrangement of metal pillar arrays or dielectric material pillar arrays 10 on a substrate 9 constitutes a photonic crystal.

The two-dimensional periodicity means that the line connecting the centers of any three adjacent pillars in the array forms a square lattice of isosceles right triangles, or a triangular lattice of equilateral triangles.

The shape of the array is rectangle 1 (as shown in FIG. 1 and FIG. 4 ) or triangle 2 (as shown in FIG. 3 ).

The material of the dielectric material plate is aluminum oxide, silicon dioxide, silicon, gallium arsenide or indium phosphide.

Polarization beam splitting method based on the positive and negative refraction effects of photonic crystals: the photonic crystal of rectangle 1 or triangle 2 is used as the polarization beam splitting element of electromagnetic waves, and the incident electromagnetic wave beam 3 contains two polarization states. After incident from the environment interface 6, one of them The electromagnetic beam of the polarization state experiences negative refraction on the environment interface, and the incident electromagnetic wave beam 3 and the refracted electromagnetic wave beam 4 are on the same side of the normal line 7 of the photonic crystal and the environment interface 6; the other polarization state of the electromagnetic wave beam is at the photonic crystal and the environment interface 6 undergoes positive refraction, and the incident electromagnetic wave beam 3 and the refracted electromagnetic wave beam 5 are respectively located on both sides of the normal line 7, thereby separating the electromagnetic wave beams of the two polarization states and realizing polarization beam splitting.

The included angle between the incident electromagnetic wave beam 3 and the normal line 7 is 10°-80°.

The photonic crystal involved in the utility model has the characteristics of the energy band in the working frequency range as shown in Fig. 6, that is, for the polarization state I, as the wave vector increases and the frequency decreases, the photonic crystal exhibits Negative refraction effect; for polarization state II, as the wave vector increases, the frequency also increases, and the photonic crystal exhibits a positive refraction effect for this polarization state. The photonic crystal whose energy band has the characteristic of Fig. 6 is the polarization beam splitting element of the present invention. The photonic crystal is cut into a flat plate or a triangle, and the incident electromagnetic wave beam is obliquely incident on an interface to realize polarization beam splitting.

Embodiment 1: Polarizing beam splitter based on dielectric background silver nanowire array

The photonic crystal here is an array of silver cylinders arranged in a triangular lattice in an alumina background, and the lattice constant a=300nm. When the silver cylinder radius r=0.255a, when the photonic crystal is at the frequency ω=0.40(2πc/a), the equivalent refractive index of TE polarization is -1 and the equivalent refractive index of TM polarization is +1, the corresponding energy The belt structure is shown in Figure 7.

Embodiment 2: Polarizing Beam Splitter Based on Dielectric Cylindrical Array

The photonic crystal here is a gallium arsenide cylinder array arranged in a triangular lattice in the air, the lattice constant a=1155nm, and the cylinder radius r=0.15a. Figure 8 shows the energy band structure of this photonic crystal, the working frequency is ω=0.75-0.79(2πc/a). TE polarization operates at negative refraction, while TM polarization is positive refraction.

Claims (6)

1. The polarizing beam splitter based on the positive and negative refraction of photonic crystals is characterized in that: a two-dimensional periodic array of air pillars in the dielectric material (8) on the substrate (9), or an array of metal pillars, or another An array of pillars of a dielectric material constitutes a photonic crystal. 2. The polarizing beam splitter based on photonic crystal positive and negative refraction according to claim 1, characterized in that: the two-dimensional periodic arrangement refers to the connection of the centers of any three adjacent columns in the array. A square lattice of right isosceles triangles, or a triangular lattice of equilateral triangles. 3. The polarizing beam splitter based on photonic crystal positive and negative refraction according to claim 1, characterized in that: the shape of the array is a rectangle (1) or a triangle (2). 4. A polarizing beam splitter based on positive and negative refraction of photonic crystals, characterized in that: on the substrate (9), a two-dimensional periodic array of metal pillars or dielectric material pillar arrays (10) constitutes a photonic crystal. 5. The polarizing beam splitter based on positive and negative refraction of photonic crystals according to claim 4, characterized in that: said two-dimensional periodicity means that the connection line between the centers of any three adjacent columns in the array constitutes A square lattice of right isosceles triangles, or a triangular lattice of equilateral triangles. 6. The polarizing beam splitter based on photonic crystal positive and negative refraction according to claim 4, characterized in that: the shape of the array is a rectangle (1) or a triangle (2).

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