Probing disorder and mode localization in photonic crystal cavities using site-controlled quantum dots

The impact of optical disorder on photon propagation in long Ln photonic crystal cavities is investigated using spectrally resolved imaging, group index measurements, and selective mode excitation with site-controlled quantum dots. Mobility and diffusive edges, separating localized, diffusive, and dispersive regimes, are consistently identified. In situ probing of the photonic modes demonstrates the low impact of disorder in the dispersive regime and the transition to phase-distorted modes in the diffusive regime. The analysis yields criteria for designing photonic crystal waveguides for efficient single photon transport.