Interfaces of photonic crystals for high efficiency light transmission

Input and output interfaces of photonic crystals are discussed for high efficiency transmission of light. The discussion focuses on the-frequency range higher than the photonic bandgap, at which a small group velocity of light, the superprism effect, the strong structural birefringence and the negative refractive index effect are expected. The two-dimensional photonic crystal of triangular lattice airholes in a high-refractive-index dielectric medium is assumed as the fundamental model, The finite difference time domain simulation shows that two types of interfaces improve the transmission efficiency. One is composed of small airholes and the other is composed of projected airholes. In particular, the latter generates a wide transmission band of similar to 0.1 times the center frequency with the maximum efficiency of -0.01 dB against the normal or slightly inclined incidence of the TE-polarized wave.