Polarization dependent oscillator strengths in (cadmium,manganese)tellurium and (zinc,manganese)selenium multiple quantum well structures
Abstract
Multiple quantum well (MQW) structures display an optical anisotropy for light propagating in the plane of the layers. This anisotropy is such that the TE polarization (electric field in the plane of the layers) couples principally to the heavy hole - conduction band transition while the TM polarization (electric field perpendicular to the plane of the layers) couples exclusively (at k = 0) to the light hole - conduction band transition. The relative positions of the heavy and light hole bands were directly observed in a qualitative manner from the relative positions of the TE and TM absorption edges in polarization dependent absorption spectra measured from a cleaved edge. In the (Cd,Mn)Te MQW's examined the effects of strain and quantum confinement act in concert to make the heavy hole - conduction band transition the lowest energy transition. In the (Zn,Mn)Se MQW's examined, however, the effect of strain opposes (and in fact dominates) the effect of quantum confinement to make the light hole - conduction band transition the lowest energy transition. Optically pumped platelet lasers were demonstrated for both a (Cd,Mn)Te and (Zn,Mn)Se MQW structure. The lasing of the (Zn,Mn)Se MQW structure is the first reported stimulated emission from a ZnSe MQW structure. In order to investigate the polarization dependence of the stimulated emission polarization dependent gain spectra were measured from a cleaved edge for both a (Cd,Mn)Te and a (Zn,Mn)Se MQW structure. Because a population inversion is most readily obtained for the lowest energy transition, it is expected that the polarization dependence of the lowest energy transition should determine the dominant polarization of the stimulated emission. For the (Cd,Mn)Te MQW it was observed that the TE mode gain dominated, as is case for (Ga,Al)As MQW's. For the (Zn,Mn)Se MQW, however, the TM mode gain was observed to dominate. This is the first report of TM dominance of the gain from a MQW structure.
Degree
Ph.D.
Advisors
Datta, Purdue University.
Subject Area
Electrical engineering
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