Octagonal quasi-photonic crystal single-defect microcavity with whispering gallery mode and condensed device size

We propose a new single-defect microcavity which supports well-confined whispering gallery mode in octagonal quasiphotonic crystals (OQPC) by shifting the eight nearest air holes around the cavity. Lasing action is observed and compared with the calculated results obtained using the finite-difference time-domain method. We also investigate the threshold dependence on the number of lattice periods of this OQPC microcavity and compare it with triangular lattice photonic crystal (PC) microcavity with similar cavity size. The OQPC microcavity exhibits only a 36% increase of threshold when the number of lattice periods decreases from eight to four, which is more advantageous than the triangular lattice PC microcavity for the shrinkage of device size.