Optical gain of inelastic exciton-exciton scattering in CdS nanowires

Abstract

We have performed a variable stripe length method at 5 K to measure the optical gain of CdS nanowires. When the excited carrier density is lower than the Mott density, we found that various inelastic scatterings of excitons and LO-phonons are involved. As a consequence of inelastic exciton-exciton scattering, the excitons scattered down to the low polariton branch cause P-emission lasing, and the excited excitons also result in a population inversion through intra-relaxation. When LO-phonon scatterings are involved, a broad optical gain spectrum is observed resulting from exciton-LO and P-LO scatterings.