Single longitudinal mode GaAs-based quantum dot laser with refractive index perturbation.

We report on the design, fabrication, and characterization of single longitudinal mode InAs/GaAs quantum dot lasers emitting at the 1.3 µm communication band. The influence of simply etched surface high-order gratings in the ridge of the Fabry-Perot lasers has been studied. A 35th-order surface grating is fabricated by standard photolithography to introduce the refractive index perturbation, which leads to the reduced mirror loss at the desired wavelength and thus realizing single longitudinal mode lasing. Stable single-mode operations are maintained at the injection current range of 45-100 mA with a side-mode suppression ratio up to 33 dB.