Injectorless quantum cascade laser operating in continuous wave above room temperature

In this paper, an injectorless quantum cascade laser (QCL) device operating in continuous wave (cw) above room temperature is presented. The pulsed performance shows a threshold current density of 1.2 kA cm^-2 at 300 K and a maximum operation temperature of 420 K. According to the thermal resistance of 16 K W^-1 in continuous wave operation, a room temperature threshold current density of 2.4 kA cm^-2 and a maximum operation temperature of 310 K have been achieved. Using very narrow ridges (∼4 νm), which were formed by a combination of dry and wet etching, the overall optical power reached 12 mW at 292 K and a slope efficiency of 220 mW A^-1 for both facets. The low-temperature (80 K) cw threshold current density is as low as 0.3 kA cm^-2, showing the potential of injectorless devices.