GaAs/AlxGa1-x as quantum cascade lasers

A unipolar injection quantum cascade (QC) laser grown in an AlGaAs/GaAs mat erial system by molecular beam epitaxy, is reported. The active material is a 30 period sequence of injectors/active regions made from Al0.33Ga0.67As/ GaAs-coupled quantum wells. For this device a special waveguide design, whi ch complies with a GaAs heavily doped substrate and very short Al0.90Ga0.10 As cladding layers, has been optimized. At a heat-sink temperature of 77 K, the laser emission wavelength is 9.4 mu m with peak optical power exceedin g 70 mW and the threshold current density is 7.3 kA/cm(2). The maximum oper ating temperature is 140 K. This work experimentally demonstrates the gener al validity of QC laser principles by showing laser action in a heterostruc ture material different from the one used until now. (C) 1998 American Inst itute of Physics. [S0003-6951(98)01150-4].