Quasi-Whispering Gallery Mode Lasing Action in an Asymmetric Hexagonal GaN Microdisk

Abstract

The optical properties of an asymmetric hexagonal GaN microdisk, fabricated via crystal growth by radio-frequency plasma-assisted molecular beam epitaxy (rf-MBE), were investigated by experimental and theoretical methods to clarify the contribution of the light confinement modes of quasi-whispering gallery modes (QWGMs). Under the optically pumped condition, a lasing action was observed from the asymmetric GaN microdisk, indicating that there is a resonant scheme of QWGMs in such a microcavity of a GaN microdisk. In addition, the analysis of the light response of hexagonal GaN microdisk models by a three-dimensional finite difference time-domain method (3D-FDTD) indicates that the QWGMs preferentially contribute to a lasing action even in a microcavity with a regular hexagonal configuration with side lengths of 1 to 2 µm. The results of the experiment and the numerical analysis strongly indicate that it is important to take not only the WGM but also the QWGMs into account to clarify the optical responses of resonant modes in a hexagonal microdisk configuration.