Ultrashort in-plane semiconductor microlasers with high-reflectivity microstructured mirrors

Abstract

We present very compact, as short as 20 μm long, low-threshold in-plane semiconductor lasers operating at a wavelength of 980 nm, in which microstructured mirrors have been formed at both cavity ends by deep reactive ion etching (RIE). The back mirror consists of a seven-period third order Bragg reflector with a measured reflectivity of ∼95%. The front mirror has a similar configuration, but consists of three periods with a lower reflectivity (∼80%) in order to allow output coupling. Lasing has been achieved from 20 μm long and 8 μm wide devices exhibiting a current threshold of 7 mA. These are among the shortest in-plane Fabry–Perot electrically pumped lasers demonstrated to date. Design issues are discussed, along with experimental data from which values for the reflectivity of the mirrors are derived. State-of-the-art electron beam lithography (EBL) and high-aspect-ratio RIE have been used for device fabrication, while additional strategies are proposed for the further improvement of the device performance.