Gain studies and lasing in excitonic waveguides of II–VI submonolayer structures

Abstract

In this paper we report on gain studies and lasing in excitonic waveguides of CdSe–ZnSe submonolayer structures. In contrast to conventional waveguides and double heterostructure lasers, no significant difference in the average refractive index between the cladding and the active layers is necessary, and these regions can be fabricated from the same matrix material. In this approach: (i) the waveguiding effect has a resonant nature and appears on the low-energy side of the strong exciton absorption peak in agreement with the Kramers–Kronig equation (ii) the absorption peak is induced by nanoscale island-like insertions of narrow-gap material in a wide-bandgap matrix. Gain spectra up to 1 kW/cm 2 demonstrate that here the excitonic-waveguide mechanism dominates. At high excitation densities the gain is additionally influenced by the formation of localized biexciton complexes.