Excitonic Gain, Laser Action, and the role of Many-body effects in ZnSe-Based Quantum Wells,
BROWN UNIV PROVIDENCE RI
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Among potential applications of wide-gap II-VI compound semiconductor quantum wells QW and superlattices at short visible wavelengths are lasers and nonlinear optical devices. Substantial progress has been recently made with ZnSe-based heterostructures in particular Zn,CdSeZnSe QWs have shown pulsed room temperature laser action in optical pumping experiments in both multiple and single well structures. At the same time, these QWs have also been found to display strong excitonic absorption features a 105 cm-1, which are well preserved up to room temperature and beyond. This raises the question about the origin of the gain for lasers, that is, the role of Coulomb effects when compared to the usual inversion from an electron-hole plasma encountered e.g. in GaAs quantum well lasers. Here we show initial results of pump-probe experiments and laser studies which indicate the presence of excitonic gain up to temperatures at least as high as 200 K. Moreover, with increasing pair density, the gain evolves directly from saturation of the excitonic gain in the Zn,CdSeZnSe quantum wells.
- Electrooptical and Optoelectronic Devices