Excitonic waveguiding and lasing in wide bandgap semiconductor

New type of structures for optoelectronics, we refer to as excitonic waveguides, are proposed and realized. Oppositely 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 (homojunction laser). 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 transformation; (ii) the absorption peak is induced by nanoscale island-like insertions of narrow-gap material in a wide bandgap matrix (quantum dots), preventing free-carrier screening of excitons and, simultaneously, allowing lasing resonant to the spectral range of the enhanced refractive index.

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