Room-temperature continuous wave operation of distributed feedback quantum cascade lasers with watt-level power output

We demonstrate surface-grating distributed feedback quantum cascade lasers (QCLs) with a watt-level power output at $4.75\mu \text{m}$ . A device with a 5 mm cavity length exhibits an output power of 1.1 W in room-temperature cw operation. Single-mode operation with a side mode suppression ratio of 30 dB is obtained in the working temperature of $15–105°\text{C}$ . A double-lobed far field with negligible beam steering is observed. The significance of this demonstration lies in its simplicity and readiness to be applied to standard QCL wafers with the promise of high-power performances.