Abstract
Internal laser characteristics of two heterostructures with an active region based on CdSe quantum dots (QDs) embedded in a complex (2-3) nm ZnCdSe/ZnSe quantum well (QW) were determined by measuring the differential laser efficiency and the laser threshold of a set of samples with different cavity lengths. Due to changing the CdSe QD nominal thickness and the ZnCdSe QW composition, the lasing wavelength for the two structures was tuned over wide ranges: green-yellow (556-573 nm) and yellow-orange (583-593 nm), depending on the cavity length. Maximum optical characteristic gain and internal quantum efficiency were measured as high as Gamma G(0) = 54 cm(-1), eta(i) = 83% (for green-yellow structure) and Gamma G(0) = 81 cm(-1), eta(i) = 72% (for yellow-orange one), while the transparency threshold I-T was lower for the former structure: 0.6 vs. 1.2kW cm(-2), with the internal optical loss of alpha(i) similar to 4.6 cm(-1) being equal for both structures. The possible reasons of the high value of the characteristic gain as well as the long-wavelength shift of the QDs emission are discussed. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim