CN111913251B - A Hybrid Plasmonic Waveguide Supporting Simultaneous TE and TM Modes - Google Patents

Abstract

The invention discloses a mixed plasmon waveguide simultaneously supporting TE (transverse electric) and TM (transverse magnetic) modes, which can be vertically arranged on the premise of not exciting a traditional mode waveguideThe mixed plasmon modes of TM and TE are supported in the vertical direction and the horizontal direction respectively. The vertical and horizontal directions are respectively provided with three layers of structures: with SiO₂For the substrate, the first layer structure is high refractive index material Si and the second layer structure is low refractive index material SiO₂The third layer structure is metal Ag; the first layer structure in the horizontal direction is a high-refractive-index material Si and is consistent with the first layer structure in the horizontal direction, the second layer structure is low-refractive-index medium air, and the third layer structure is metal Ag. The second layer structures in the vertical and horizontal directions are both positioned between the first layer structure and the third layer structure. The waveguide realizes the control of the polarization state of the optical wave, and provides possibility for realizing high-density integration of various applications requiring polarization control.

Description

A Hybrid Plasmonic Waveguide Supporting Simultaneous TE and TM Modes

technical field

The invention belongs to the technical field of subwavelength photonics, and in particular relates to a hybrid plasmon waveguide supporting both TE and TM modes.

Background technique:

Polarization state is one of the important properties of light, and its vector properties make intricate interactions between it and matter, so people can make various optical devices and optical systems. Past studies have mainly focused on spatially uniform polarization states, such as linear polarization, circular polarization, etc., for which the polarization state does not depend on the spatial position of the beam.

Hybrid plasmon waveguide (HPW) is generally composed of a metal layer and a high-refractive-index dielectric material layer sandwiched by a low-refractive-index dielectric material. The performance of HPW is closely related to the thickness of the intermediate low-refractive-index dielectric layer: when When the thickness of the dielectric layer is large, the two modes are separated, and usually the plasmon mode cannot be excited; when the thickness of the dielectric layer is reduced to a certain extent, the two modes are mixed and superimposed into a new mode, and the light field Mainly confined to the middle layer of low refractive index dielectric material.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a hybrid plasmon waveguide that supports both TE and TM modes to improve the performance of existing structures.

A hybrid plasmon waveguide supporting TE and TM modes at the same time, including a plasmon waveguide mixed in a vertical direction and a horizontal direction, the vertical plasmon waveguide is composed of three layers of materials, including the first A layer of high refractive index material, a second layer of low refractive index material and a third layer of metal material, the horizontal plasmon waveguide is composed of three layers of materials, including the first layer of high refractive index material, The low refractive index material of the second layer and the metal material of the third layer, the second layer structures in the vertical direction and the horizontal direction are both located between the first layer and the third layer structure.

Further, the refractive index of the high refractive index material Si is 3.478, the refractive index of the low refractive index material SiO ₂ is 1.44, and the refractive index of the low refractive index material air is 1.

Further, the height of Si is selected from 100 to 400 nm, the width of Si is selected from 100 to 300 nm, and the low refractive index layer is selected from 30 to 80 nm.

The optical field is well confined in the low-refractive-index dielectric layer (air, SiO ₂ ), and at the same time, it has the characteristics of low loss and long propagation distance under the condition that the structure is still compact.

The real part of the mode's effective refractive index represents the refractive index in the hybrid plasmonic waveguide structure, while the imaginary part determines the transmission loss of the hybrid mode propagating in the waveguide.

The advantages of the present invention are: the hybrid plasmon waveguide supporting TE and TM modes simultaneously:

(1) The structure is simple and easy to design, the material is easy to obtain, and the preparation is easy to realize;

(2) The hybrid plasmon modes of TE and TM can be supported in the horizontal and vertical directions respectively without exciting the traditional mode waveguide, which breaks through the limitations of the existing structure;

(3) Through proper selection of materials and reasonable design of structural dimensions, the transmission loss can be kept low;

(4) The structure is compact, so it is convenient for photonic integration, can be applied to ultra-high-density integrated optical circuits, and is easy to be applied to high-integration optical waveguide chips.

Description of drawings

FIG. 1 is a schematic cross-sectional view of a hybrid plasmon waveguide structure supporting both TE and TM modes according to an embodiment.

FIG. 2 is a mode distribution diagram of a TE polarized light waveguide with a wavelength of λ=1550 nm in an embodiment.

FIG. 3 is a mode distribution diagram of a TM polarized light waveguide with a wavelength of λ=1550 nm in an embodiment.

FIG. 4 is a graph showing the variation of the real part of the effective refractive index with the width of Si in an optical waveguide mode with a wavelength of λ=1550 nm.

FIG. 5 is a graph showing the variation relationship between the real part of the effective refractive index of the optical waveguide mode with the wavelength of λ=1550 nm and the height of Si according to the embodiment.

FIG. 6 is a graph showing the relationship between the real part of the effective refractive index and the thickness of the low refractive index dielectric layer (the height of SiO ₂ and the width of the air layer) g in the optical waveguide mode with wavelength λ=1550 nm of the embodiment.

Detailed ways

In order to make the technical means, creative features, achievement goals and effects realized by the present invention easy to understand, the present invention will be further described below with reference to the specific embodiments.

As shown in Figure 1, the hybrid plasmon waveguide supporting both TE and TM mode optical waveguide modes is a structure composed of three materials A, B and C, which are divided into two parts: the left and the right parts, which are the high refractive index medium Si. , low refractive index medium SiO ₂ and precious metal Ag. The height of the corresponding _SiO2 and the width of the air layer between the left and right parts are g.

The high-refractive index medium, low-refractive index medium and noble metal in this embodiment are Si, SiO ₂ , air, and Ag, wherein the refractive index of Si is 3.478, the refractive index of SiO ₂ is 1.44, and the refractive index of air is 1. For the incident light of 1550nm wavelength, the corresponding refractive index of metallic silver is 0.145+11.438i.

FIG. 2 and FIG. 3 are respectively the distribution diagrams of the TE and TM polarized light waveguide modes with the wavelength of λ=1550 nm in the embodiment. The thickness of the low-refractive-index dielectric layer (the height of SiO ₂ and the width of the air layer) is g=50 nm. It can be seen from the figure that under the incident light of 1550 nm wavelength, the hybrid plasmon waveguide has obvious field enhancement effect in the low refractive index medium region, and has super strong mode field confinement ability.

FIG. 4 shows the variation relationship between the real part of the effective refractive index of the optical waveguide mode with the wavelength of λ=1550 nm and the width w_si of Si according to the embodiment. It can be seen from the figure that the real part of the effective refractive index of the optical waveguide mode increases with the increase of the width w_si of Si, indicating that the confinement ability of the waveguide to the transmission mode increases with the increase of the width of Si.

FIG. 5 shows the variation relationship of the real part of the effective refractive index of the optical waveguide mode with the wavelength of λ=1550 nm with the height h_si of Si. It can be seen from the figure that the real part of the effective refractive index of the optical waveguide mode increases with the increase of the height h_si of Si, indicating that the confinement ability of the waveguide to the transmission mode increases with the increase of the height of Si.

FIG. 6 shows the variation relationship of the real part of the effective refractive index with the thickness of the low refractive index medium layer (the height of SiO ₂ and the width of the air layer) g for the optical waveguide mode with wavelength λ=1550 nm of the embodiment. It can be seen from the figure that the real part of the effective refractive index of the optical waveguide mode decreases with the increase of the thickness of the low-refractive _- index dielectric layer (the height of SiO and the width of the air layer) g, indicating that the waveguide's ability to confine the transmission mode increases with the thickness of the low-refractive-index dielectric layer. increases and increases, and the real part of the effective refractive index of the TM mode is larger than that of the TE mode.

It is known from the technical common sense that the present invention can be realized by other embodiments without departing from its spirit or essential characteristics. Accordingly, the above-disclosed embodiments are, in all respects, illustrative and not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are encompassed by the present invention.

Claims (2)

1. A hybrid plasmon waveguide supporting TE and TM modes at the same time, characterized in that it comprises a plasmon waveguide mixed in a vertical direction and a horizontal direction, and the vertical plasmon waveguide is composed of three plasmons. The layer material is composed of a first layer of high refractive index material, a second layer of low refractive index material and a third layer of metal material, and the horizontal plasmon waveguide is composed of three layers of material, including the first layer The high-refractive-index material, the low-refractive-index material of the second layer and the metal material of the third layer, the high-refractive-index material of the first layer in the horizontal direction is consistent with the high-refractive-index material of the first layer in the vertical direction. The second layer structure in the vertical direction and the horizontal direction is located between the first layer structure and the third layer structure; The plasmon waveguides in the vertical direction and the horizontal direction are both based on SiO ₂ ; The high refractive index material of the first layer of the plasmon waveguide in the vertical direction and the horizontal direction is all Si, and its refractive index is 3.478; the height of the high refractive index material Si is 100-400nm, and the width is 100-300nm ; The low-refractive-index material of the second layer of the plasmon waveguide in the vertical direction is SiO ₂ , and its refractive index is 1.44; The width of the low-refractive-index material of the second layer of the plasmon waveguide in the vertical direction and the horizontal direction is both 30-80 nm; The metal material of the third layer of the plasmon waveguide in the vertical direction and the horizontal direction is Ag; The low-refractive-index material of the second layer of the plasmon waveguide in the horizontal direction is medium air, and its refractive index is 1. 2 . The hybrid plasmon waveguide supporting both TE and TM modes according to claim 1 , wherein the working wavelength of the hybrid plasmon waveguide is 1550 nm. 3 .

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