Experiments Versus Modelling in Quantum Dot Pillar Microcavities

Recently, single photon sources have been realised by coupling InAs quantum-dots into circular micro-pillar microcavities based on distributed Bragg reflectors (DBRs). These sources can be highly efficient because the high semiconductor refractive index collects a large fraction of the spontaneous emission into the waveguide mode. We have modelled emission from circular, square, elliptical and rectangular pillars using the finite difference time domain (FDTD) method and see enhanced emission into the cavity mode and improved efficiency for coupling light out of the microcavity. The cavity Q-factors can be very high even when the pillar diameter (dimension) is comparable to the emission wavelength. In the elliptical and rectangular cavities the modes separate (in frequency) into a high-Q resonance with polarisation parallel to the long axis and a lower Q-factor resonance with polarisation orthogonal to the long axis. We compare our modelling with preliminary measurements made on micro-pillar microcavity samples containing a layer of low density InAs dots at the cavity centre.