Efficient coupling into slow-light photonic crystal channel guides using photonic crystal tapers

Photonic crystal tapers have been designed for coupling of light from ridge waveguides into low group velocity photonic crystal channel guides. The coupling efficiency is increased from 3 % (case of butt-coupling) to 97 % for frequencies in the band-edge region, corresponding to a group index close to 100, as predicted using 2D finite-difference time-domain simulations.