Abstract

Circular microdisk semiconductor lasers have low laser thresholds and outputs, because whispering gallery modes (WGMs), which have high Q and low non-directional output, provide their feedback [1]. Stadium-shaped microdisk quantum-cascade lasers have greatly increased emission and directionality, because feedback is provided by the regular-orbit “bow-tie” modes [2]. Despite high dislocation densities in GaN, we have achieved directional laser emission from quadrupolar-deformed GaN microdisks which have the same threshold as circular microdisks. With uniform optical pumping of the top face of the quadrupolar-shaped microdisk, the strongest directional emission emerges from the sidewall as four beams at 50° relative to the long axis The feedback is attributed to chaotic-orbit modes that leak out by refraction, when rays have incident angle less than the critical angle.

© 2000 IEEE