Controlling the filtering characteristics of the two-dimensional silicon-based photonic crystal with elliptic air holes

Light propagation characteristics of the channel filters based on the two-dimensional photonic crystals with elliptic defects are studied by the finite-difference time-domain method. The two-dimensional photonic crystal consists of a triangular array of air holes immersed in the silicon background. Shape alteration of the air hole from a circle to an ellipse offers a powerful approach to engineer the resonant frequency of channel filters. And the resonant frequency can be flexibly adjusted only by changing the orientation angle of the elliptic holes. A six-channel drop filters based on the elliptic holes with different obliquities is designed. Connected with the active optical device, above structure can be employed as a kind of frequency division and direction separation device, which is suitable in the complicated optical circuits.