External-cavity quantum cascade laser using intra-cavity out-coupling

We describe an external-cavity quantum cascade laser with an intra-cavity out-coupling optical system, tunable from 8.4 μm to 10.8 μm. The new optical configuration allows higher output power compared to a conventional Littrow-type external cavity approach, while keeping the broad tunability of wavelength. We achieved 1 W output power at the maximum in pulse-mode operation, which is more than twice the optical power using the Littrow design with the same gain chip.