Directional laser emission from chaotic cavity modes in GaN micropillars

Summary form only given. The observation of directional laser emission from the "bow-tie" mode in stadium-shaped quantum cascade lasers has added to the interest in microdisk lasers. Shorter wavelength materials, such as GaN, make it possible to image the emission location along the sidewall of a micropillar laser with standard CCD cameras, enabling the direct identification of the excited mode. We have previously demonstrated laser action in circular GaN microdisks which emit uniformly in all directions. Here, we achieve more directional laser emission from optically pumped GaN micropillars of various shapes-quadrupolar, elliptical, and quadrupolar-octupolar. By imaging the micropillar sidewall, we show that the laser mode in the quadrupolar cavity comes from chaotic modes.