Spectral Linewidth Analysis for Square Microlasers

Mode characteristics and spectral linewidths are investigated for single-mode and dual-mode AlGaInAs/InP square microlasers. For a single-mode square microlaser with a side length of 22 μm, connected with a 2-μm-wide waveguide, a linewidth of 20 MHz is obtained by means of a non-zero delayed self-heterodyne method. Dual-mode square microlaser linewidths are also analyzed using an optical heterodyne, and a strong mode correlation is experimentally demonstrated. Furthermore, we successfully realize the narrow-linewidth microlaser and microwave signal generation through a dual-loop optical feedback technique.