Mode structure of coupled L3 photonic crystal cavities

We investigate the energy splitting, quality factor and polar-ization of the fundamental modes of coupled L3 photonic crystal cavities. Four different geometries are evaluated theoretically, before experimentally investigating coupling in a direction at 30° to the line of the cavities. In this geometry, a smooth variation of the energy splitting with the cavity separation is predicted and observed, together with significant differences between the polarizations of the bonding and anti-bonding states. The con-trolled splitting of the coupled states is potentially useful for applications that require simultaneous resonant enhancement of two transitions.