Single-mode unidirectional-emission circular-side hexagonal resonator microlasers

Circular-side hexagonal resonator (CSHR) microlasers connecting an output waveguide are proposed and demonstrated for enhancing the mode Q factor and realizing single-mode operation. Three-dimensional simulation results indicate that the CSHRs with an optimized deformation can greatly enhance mode Q factors. The CSHR microlasers with output waveguides are fabricated using a planar technology process. For a CSHR microlaser with a side length of 7.5 μm and an output waveguide width of 2 μm, single-mode operation is realized with a side-mode suppression ratio of 43 dB and a threshold current of 2.5 mA. Furthermore, flat small-signal modulation responses are obtained with a 3 dB bandwidth of 13 GHz.