EXCITON DIFFUSION AND MULTIMODE BEHAVIOUR IN ELECTRON-BEAM-PUMPED CDS LASERS

From CdS platelet crystals coherent radiation can be obtained resulting from the decay of free excitons to photons and longitudinal optical phonons (line ALO). In semiconductor lasers as CdS with a homogeneously broadened spontaneous emission line spatial inhomogeneity of the inverted population can lead to multimode oscillation. The number of axial modes oscillating simultaneously for a given excitation value above the threshold depends on the diffusion velocity of the inverted carriers, whereby the diffusion is smoothing out the spatial inhomogeneities. The fitting of the experimental data by the theory of Statz and Tang enables us to determine the exciton diffusion length at liquid‐air temperature; we find LDiff = 0.1 μm. Copyright © 1969 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim