Laser characteristics of a heterostructure with a five Cd(Zn)Se QD sheet active region embedded in non-symmetrical superlattice graded-index waveguide.

Optically pumped green-emitting (545-551 nm) ZnSe-based laser heterostructures grown by molecular-beam epitaxy have been elaborated and studied. The optimized II-VI laser heterostructure involves a non-symmetrical Zn(Mg)SSe/ZnSe superlattice (SL) graded-index waveguide and an active region comprising five CdSe quantum dot sheets each placed in the centre of a 2 nm-thick ZnSe quantum well. Such a structure design provides both large optical confinement factor and high homogeneity of excitation. Internal laser parameters were determined by measuring the laser threshold and differential quantum efficiency as functions of the cavity length. The values of internal quantum efficiency, internal optical losses, characteristic gain and transparency threshold have been estimated to be ηi = 80.5%, αi = 3.2 cm-1, ΓG0 = 135 cm-1, and IT = 1.35 kW/cm2, respectively. Based on the defined parameters, the values of minimum threshold power and corresponding optimum cavity length have been derived. It is shown that the minimum threshold power decreases significantly (by more than 20%) in comparison with that for the heterostructure with conventional flat-band SL waveguide (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]