Photonic crystal circular-shaped microcavity and its uniform cavity-waveguide coupling property due to presence of whispering gallery mode.

In this report, we investigate a photonic crystal circular-shaped microcavity (removing seven air holes) sustaining whispering-gallery mode (WGM) by shifting the 12 nearest air holes according to the concept of cavity-shaping in micro-disk and micro-gear lasers. The WGM modal characteristics are investigated by three-dimensional (3D) finite-difference time-domain (FDTD) simulations. From well-fabricated devices and simulated results, we obtain and identify WGM single-mode lasing with low threshold and high measured quality factor. By inserting additional waveguides, we also investigate its uniform coupling behaviors in different waveguide-cavity-waveguide geometries in both FDTD simulations and experiments.