High quality factor microcavity lasers realized by circular photonic crystal with isotropic photonic band gap effect

The photonic band gap (PBG) effect and its isotropy of sunflower-type circular photonic crystal (CPC) are obtained and investigated from the transmission spectra performed by finite-difference time-domain (FDTD) method. The PBG directional width variation is found to be only 6.7%. A well-confined whispering gallery mode (WGM) with azimuthal number of 6 is obtained by FDTD simulation from the CPC microcavity formed by seven missing air holes (C2). Ascribed to the deep and isotropic PBG confinement, the WGM lasing with very-low threshold (∼0.13 mW) and very-high-quality (Q) factor (>10000) is obtained from well-fabricated CPC C2 microcavity lasers.