Distributed-Feedback Quantum-Cascade Lasers at 9 $mu$m Operating in Continuous Wave Up to 423 K

Single-mode lasers operating at $lambdaapprox 9 muhbox{m}$ in continuous wave up to 423 K (150 $^{circ}hbox{C}$) were achieved by the combination of strong distributed-feedback coupling, a narrow gain active region design, low intersubband, and free-carrier losses as well as a good thermal management. Tuning of 10 $hbox{cm}^{-1}$ or 0.9% of the center frequency was achieved by heating the device. The threshold current density varies from 1.1 $hbox{kA/cm}^{2}$ at 303 K to 2.4 $hbox{kA/cm}^{2}$ at 423 K. Other devices with low electrical power consumption of 1.6 and 3.8 W for an optical output power of 16 and 100 mW have been demonstrated at 263 K.