Mode identification of high-quality-factor single-defect nanocavities in quantum dot-embedded photonic crystals

We investigate the quality (Q) factor and the mode dispersion of single-defect nanocavities based on a triangular-lattice GaAs photonic-crystal (PC) membrane, which contain InAs quantum dots (QDs) as a broadband emitter. To obtain a high Q factor for the dipole mode, we modulate the radii and positions of the air holes surrounding the nanocavity while keeping sixfold symmetry. A maximum Q of 17 000 is experimentally demonstrated with a mode volume of V=0.39(lambda/n)(3). We obtain a Q/V of 44 000(n/lambda)(3), one of the highest values ever reported with QD-embedded PC nanocavities. We also observe ten cavity modes within the first photonic band gap for the modulated structure. Their dispersion and polarization properties agree well with the numerical results. (c) 2007 American Institute of Physics.