Increase of Q-factor in photonic crystal H1-defect nanocavities after closing of photonic bandgap with optimal slab thickness

We investigate the dependence of quality factor Q of dipole modes in photonic crystal H1-defect nanocavity on the slab thickness and observe an increase of Q even after closing of the photonic bandgap both in numerical simulation and experimentation. This counter intuitive behavior results from the weak coupling between the cavity mode and the 2(nd)-guided mode in the photonic crystal slab. This is confirmed by computing the overlap between them in the momentum space. c 2008 Optical Society of America (c) 2008 Optical Society of America.