Method for designing high coupling efficiency composite type two-dimensional photon crystal

Abstract

A design method for a composite two-dimensional photonic crystal with high coupling efficiency, characterized in that: according to the working wavelength, the dielectric column material and the background material of the photonic crystal are selected; the lattice period of the photonic crystal is set as a constant a; the dielectric column is perpendicular to Place and fix the z direction of the paper; design a photonic crystal structure with a length M×a and a width N×a, take the direction of the long side as the x direction, and take the direction perpendicular to the x direction as the y direction; then take the middle of the photonic crystal in the x direction position, and lose all the dielectric columns along the y direction at this position to form a waveguide structure, and the incident light enters the waveguide structure from below the photonic crystal structure; reduce the cross-sectional size of the dielectric column of the photonic crystal output layer, and make this layer The even-numbered dielectric column moves downward to form a wrinkled structure; the even-numbered dielectric column under the wrinkled layer is removed to form a point defect structure; the structure designed in the present invention enhances the excitation of the surface mode, which can greatly improve The energy of the radiated radiation is directed, while the convergence of the outgoing beam is also improved.

Description

technical field [0001] The invention relates to a method for improving the coupling efficiency of a photonic crystal by introducing a composite structure, in particular to a design method for a composite two-dimensional photonic crystal with high coupling efficiency. Background technique [0002] Photonic crystal is a kind of artificially manufactured periodic material. Due to its bandgap characteristics, it can be applied in many aspects. A recent development is to use photonic crystal surface waves to realize directional radiation, and to construct periodic folds on the surface of photonic crystals. The structure can excite the surface mode and couple the surface mode into the radiation mode to achieve directional radiation. The literature proposes that the excitation of the surface wave can be enhanced by improving the coupling efficiency between the waveguide mode and the surface mode, thereby improving the performance of directional radiation; The specific method is to ...

AI Technical Summary

Problems solved by technology

[0002] Photonic crystal is a kind of man-made periodic material. Due to its forbidden band characteristics, it can be applied in many aspects. A recent development is to use photonic crystal surface waves to realize directional radiation, and to construct periodic folds on the surface of photonic crystals. The structure can excite the surface mode and couple the surface mode into the radiation mode to achieve directional radiation. The literature proposes that the excitation of the surface wave can be enhanced by improving the coupling efficiency between the waveguide mode and the surface mode, thereby improving the performance of directional radiation; The specific method is to increase the refractive index of the surface cylinder and move the cylinder of the photonic crystal surface forward to form a wrinkled structure, etc. However, only by improving the coupling efficiency between the waveguide mode and the surface mode, the improvement of the directional radiation performance is relatively limited. It has been proposed in the literature that directional radiation can also be achieved by adding point defects to the layer near the exit surface of the photonic crystal to form a resonant mode. However, due to the large energy reflected back to the waveguide by the resonant mode, the radiated energy is greatly limited.

Images