Stability of Intensity Imbalance between Left‐ and Right‐Circulation Modes in GaN Hexagonal Microdisk

Abstract

The mechanisms underlying the stability of the intensity imbalance between the left‐ and right‐circulating lasing modes in a GaN hexagonal microdisk resonator are investigated. Finite‐difference time‐domain simulations reveal that the imbalance is determined by the position of the point light source (seed light for lasing) inside the resonator. The coupling mechanism between the resonance modes and light from the source is clarified using numerical calculations. In addition, it is confirmed that light is highly coupled with one of the circulation modes when the source is placed off the bilateral symmetry axis of the mode near the side of the resonator, without any influence of the polarization of the source. The results indicate that the imbalance of the lasing modes observed in the experiments is determined by the position of the seed light near the side of the resonator, which must be spontaneous emission from impurities or defects, such as donor–acceptor pairs, donor‐bounded excitons, basal plane stacking faults, or the transition of free electrons in the conduction band to acceptor levels et al.