High Efficiency Interface for Coupling Into Slotted Photonic Crystal Waveguides

We investigate the mechanism of coupling light into slotted photonic crystal waveguides. We identify two alternative approaches for improving the coupling efficiency, based on engineered mode dispersion and on resonant mechanisms. For the optimized geometry, we calculate a loss figure of 0.3 dB over 100-nm bandwidth per interface and demonstrate a corresponding experimental value of 1.5 dB over 78-nm bandwidth per interface.