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

Single-mode lasers operating at lambda ap 9 mum in continuous wave up to 423 K (150degC) 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 cm
^-1
or 0.9% of the center frequency was achieved by heating the device. The threshold current density varies from 1.1 kA/cm
²
at 303 K to 2.4 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.