Efficient optical coupling to Bloch waves

Summary form only given. Highly non-linear dispersion of Bloch waves which may be designed into photonic crystals (PCs) has potential application in optical signal processing, laser beam steering, and WDM filtering. However, due to the large mismatch between the group velocity in a PC material and an isotropic material it is difficult to couple light efficiently to these structures over a wide range of input wavelengths. In this paper we show how a non-periodic dielectric transition region may be used to reduce coupling losses. In this way we provide an approach to remove one of the barriers to practical application of PCs.