Demonstration of Low-Threshold and Directly Modulated Grating-Assisted Microcylinder Surface-Emitting Lasers

In this article, we report the demonstration of directly modulated grating-assisted microcylinder surface-emitting lasers (GAMSELs) with low threshold. Two second-order gratings are added onto the side and top of the microcylinder cavity to select a single mode with a radially polarized emission pattern and efficiently emit the mode vertically, respectively. Laser with cavity radius of 6.05 μm is demonstrated with continuous-wave lasing ranging from 1 °C to 50 °C. This radius is approaching the theoretically smallest radius for the microcylinder laser to work at O band. A low threshold of 3.6 mA at 15 °C is obtained for the GAMSEL laser. Single-mode lasing with side-mode suppression-ratio (SMSR) larger than 40 dB is also shown here. GAMSELs with different cavity radii are demonstrated as laser arrays. 3 dB direct modulation bandwidth of 12 and 14 GHz of GAMSELs with radius of about 8 and 10 μm are obtained, respectively. Besides, effects of the duty cycle of the top and side gratings, scattering losses of the cavity, gain peak of the epitaxial wafer and ion implantation are experimentally investigated.