Strong exciton‐light coupling in photonic crystal nanocavities

Abstract

The strong coupling regime between excitons in a single self-assembled InAs quantum dot and the cavity mode in a photonic-crystal structure embedded in GaAs planar waveguides is theoretically investigated. It is concluded that zero-dimensional mixed states should form when the quality factor of the cavity mode is higher than Q ∼ 2000. The corresponding vacuum-field Rabi splitting is close to its limiting value already for Q ∼ 10000. Results are shown for a model GaAs-based photonic crystal nanocavity, in which single quantum dot excitons are predicted to be always in the strong coupling regime if the quantum dot is placed close to the antinode position of the electric field. 1 Introduction Photonic crystals (PhC) embedded in planar dielectric waveguides (also known as photonic-crystal slabs) allow for a three-dimensional (3D) control of light confinement and propagation at optical wavelengths, and are currently receiving much attention owing to the difficulties in fabricating 3D PhC with robust band gaps in the visible region (for a recent review see [1]). In PhC slabs the electromagnetic field can be confined in 3D by exploiting the photonic band gap properties in the plane of the waveguide and the confinement provided by the strong dielectric contrast along the vertical direction. By creating localized defects in the otherwise periodic structures, PhC nanocavities with cavity mode energies falling within the photonic band gap can be obtained. Very small mode volumes and ultra-high quality (Q) factors have been recently demonstrated for cavity modes in thin air-suspended Silicon slabs (also called air bridges) with point defects in a triangular lattice of air holes [2]. Thus, these systems appear as ideal candidates for the observation of the strong coupling regime and other interesting cavity quantum electrodynamics phenomena in photonic nanostructures.