Milliwatt level room temperature 2.38 THz quantum cascade laser sources

We demonstrate milli-watt level output power from THz nonlinear quantum-cascade lasers based on a lens coupled Cherenkov radiation scheme, in which obliquely polished semi-insulating InP substrate facet of the device is closely appressed to a high-resistivity silicon lens. This enables much more efficient THz radiation extraction compared with the conventional Cherenkov phase matching scheme by which THz radiation emits to air from obliquely polished substrate facet. The waveguide simulations revealed ~4 times higher output power. Adopting the lens coupled Cherenkov radiation scheme, the device produces ~1 milli-watt peak power at a frequency of 2.38 THz at room temperature, which provided ~0.22 milli-watt with the conventional Cherenkov phase matching approach.