Unidirectional lasing from InGaN multiple-quantum-well spiral-shaped micropillars

We report unidirectional emission from lasing in ${\mathrm{In}}_{\text{0.09}}{\mathrm{Ga}}_{\text{0.91}}\mathrm{N}/{\mathrm{In}}_{\text{0.01}}{\mathrm{Ga}}_{\text{0.99}}\mathrm{N}$ multiple-quantum-well spiral micropillars. Our imaging technique shows that the maximum emission comes from the notch of the spiral microcavities at an angle about $\text{40°}$ from the normal of the notch. At room temperature, the spiral microcavity lases near 400 nm when optically pumped with 266 or 355 nm light. A reduction in the lasing threshold and an improvement in unidirectionality occurs when the microcavity is selectively pumped near its boundary.