Design of an air-slot mode-gap nanocavity in a two dimensional photonic crystal slab

We present a novel and simple design of an air-slot mode-gap photonic crystal (PC) nanocavity by introducing a linear air slot to the center of a line-defect waveguide in a two dimensional triangular-lattice silicon PC slab. A high quality factor (Q factor) of 8.42×105 and an ultrasmall mode volume of 0.998 cubic wavelength are achieved in an optimized air-slot nanocavity which is a suitable choice for the strong matter-field interaction in free space. The high Q cavities with ultrasmall mode volume are important for applications such as quantum computation and nonlinear optics.