Ultrahigh-Q two-dimensional photonic crystal slab nanocavities in very thin barriers

We demonstrate that width-modulated line-defect nanocavities in photonic crystals with long air slots on either side can maintain an ultrahigh Q even with very thin in-plane photonic crystal (only several rows of air holes). Although it is commonly believed that high-Q photonic crystal nanocavities require relatively thick in-plane barriers, surprisingly these nanocavities fabricated in silicon photonic crystals exhibit an ultrahigh Q (>106) even with very thin barriers. This design may be useful for various nanocavity applications.