Gain to absorption conversion by increasing excitation density in excitonic waveguides

Exciton waveguiding was proposed to improve optical confinement of II-VI lasers. Strong resonant exciton absorption induces a refractive index enhancement (An! on the low-energy side of the absorption peak. By stacking sheets of submonolayer (SML) CdSe insertions into a ZnSe matrix, we fabricated a region in ZnSe with strong resonant exciton absorption. In this region, the k-selection rule is lifted due to exciton localization by the SML islands. Therefore, a zero-phonon lasing mechanism resonant to the exciton waveguiding region could be realized. Using the variable-stripe-length method, we study the intensity-dependent optical gain of the ZnSe/CdSe submonolayer superlattices in a ZnS0.06Se0.94 matrix. (C) 1998 Elsevier Science B.V. All rights resented.