Mode and modulation characteristics for microsquare lasers with a vertex output waveguide

The mode and high-speed modulation characteristics are investigated for a microsquare laser with a side length of 16 μm and a 2-μm-wide output waveguide connected to one vertex. The longitudinal and transverse mode characteristics are analyzed by numerical simulation and light ray model, and compared with the lasing spectra for the microsquare laser. Up to the fifth transverse mode is observed clearly from the lasing spectra. Single mode operation with the side mode suppression ratio of 41 dB is realized at the injection current of 24 mA, and the maximum output power of 0.53 (0.18) mW coupled into the multiple (single) mode fiber is obtained at the current of 35 mA, for the microsquare laser at the temperature of 288 K. Furthermore, a flat small-signal modulation response is reached with the 3-dB bandwidth of 16.2 GHz and the resonant peak of 3.6 dB at the bias current of 34 mA. The K-factor of 0.22 ns is obtained by fitting the damping factor versus the resonant frequency, which implies a maximum intrinsic 3-dB bandwidth of 40 GHz.