High-temperature operation of a low-threshold 5.3 mum quantum-cascade distr
ibuted feedback laser is presented. The emission spectrum was single mode w
ith more than 20 dB side mode suppression ratio for all investigated temper
atures and up to thermal rollover. For 1.5% duty cycle and at 0 degreesC, t
he laser emitted 1.15 W of single mode peak power; at 120 degreesC, a value
of 92 mW was seen. For a 3 mm long device, we observed a room-temperature
threshold current density of 3.6 kA/cm(2). This remarkable performance is m
ainly due to a 4 quantum-well active region using a double phonon resonance
for the lower laser level. (C) 2001 American Institute of Physics.