High-power CW mid-IR quantum cascade lasers

We report the cw operation of quantum cascade lasers that do not require cryogenic cooling and emit at lambda = 4.7-6.2 mu m. At 200 K, more than 1 W of output power is obtained from 12-mu m-wide stripes, with a wall-plug efficiency (eta(wall)) near 10 %. Room-temperature cw operation has also been demonstrated, with a maximum output power of 640 mW (eta(wall) = 4.5 %) at 6 mu m and 260 MW (eta(wall) = 2.3 %) at 4.8 mu m. Far-field characterization indicates that whereas the beam quality remains close to the diffraction limit in all of the tested lasers, in the devices emitting at 6.2 mu m the beam tends to steer by as much as 5-10 degrees in either direction with varying temperature and pump current.