Surface-emitting distributed feedback quantum-cascade lasers

We report on the realization of second-order distributed feedback quantum-cascade lasers at lambda=9.35 mu m, where the active region consists of GaAs, AlGaAs, and strained InGaAs grown on GaAs. A metal-stripe surface grating structure allows a high surface emission efficiency for the TM-polarized light. The emitted power via the surface is in the range of 100 mW and exceeds the emitted power from one facet. A double-lobed surface-emission far-field pattern is obtained for the lasing mode. The single-mode emission wavelength is continuously tunable by the heat sink temperature. (C) 2000 American Institute of Physics. [S0003-6951(00)00340-5].