Single-mode surface-emitting microcylinder/microring laser assisted by a shallowly-etched top grating

Semiconductor lasers based on microcylinder/microring cavities supporting high-quality factor modes are promising candidates of optical sources for optical interconnect. However, their multi-mode lasing performance and non-directional emission characteristic restrict their applications. In this paper, a single mode surface-emitting laser at O-band based on a second-order grating shallowly etched on the top of the microcylinder/microring cavity is proposed and demonstrated. The second-order top grating cannot only scatter the whispering gallery modes vertically to form surface emission but also select a single mode to lase. The laser is electrically pumped and continuous wave operated in a wide temperature range with side-mode suppression-ratio larger than 40 dB. The upward surface-emitting optical power exceeds 1 mW. Except for O-band, the laser can be easily realized at other long-wavelength communication bands, such as C-band and L-band.