Digitally graded GaAs/Al0.44Ga0.56As quantum-cascade laser

A method for the optimal design and realization of a GaAs/Al0.44Ga0.56As quantum-cascade laser (QCL) is presented. Firstly, an optimal, smooth active region profile is derived, using inverse spectral theory. A digitally graded laser structure is then designed, having an approximately equivalent potential profile. The gain and threshold current of the optimized device are calculated using a 15-level self-consistent rate equation model, and are shown to represent substantial improvements over the figures obtained, using the same calculation method, for the recently reported room temperature GaAs/Al0.44Ga0.56As QCL of Page et al. (Appl. Phys. Lett. 78 (2001) 3529).