Coupling of point-defect microcavities in two-dimensional photonic-crystal slabs

We investigate the coupling of two single point-defect microcavities formed in a two-dimensional photonic-crystal slab. The mode structure is probed using photoluminescence spectroscopy of self-assembled InGaAs quantum dots embedded in GaAs/AIGaAs membrane-based, photonic-crystal microcavities. As a baseline, we start from single defect cavities: We observe defect states originating from both the ground and the first-excited slab waveguide mode, depending on the photonic-crystal lattice period. This is explained using three-dimensional, plane-wave-expansion calculations. In the case of coupling between two such single defects, a splitting of the mode energies into binding and antibinding states controlled by the coupling strength is observed. These photonic-defect-molecule states are identified by a comparison of their expected far-field distributions with polarization-dependent measurements. (C) 2003 Optical Society of America.