Unidirectional Emission Cut-Corner Square Microcavity Lasers

Square microcavity lasers with a cut-corner are proposed and demonstrated for realizing unidirectional emission single-mode lasers. The mode characteristics of the square resonator with a cut-corner are investigated by 2-D finite-element method simulation. Far field patterns with single petal and double petals are obtained numerically for symmetric and antisymmetric modes, respectively. Square microcavity lasers with a cut-corner are fabricated using planar photolithography and inductively coupled-plasma etching techniques. A continuous wave single-mode operation with a side mode suppression ratio of 31 dB is achieved at an injection current of 25 mA for a 20 μm-side-length square microcavity laser with a cut-corner width of 10 μm. The far field patterns agreement with the simulated symmetric and anti-symmetric modes are observed at different injected currents.