Theory and fabrication of evanescently-coupled photoluminescent devices

Abstract

This thesis discusses the theory and implementation of evanescently-coupled photoluminescent devices. We demonstrate the feasibility of efficient, spectrally tunable lighting devices through quantum dot photoluminescence. Devices that enjoy both great efficiencies and excellent color temperatures are the goal of current lighting research. They are a "have your cake and eat it too," achievement that are not realized with current technologies. It has long been recognized that the narrow and tunable emission spectra of quantum dots allows access to an unprecedented range of colors, with which one could construct a spectrally perfect white light. However, current quantum dot photoluminescent devices suffer efficiency losses due to high reabsorption of emitted light. We demonstrate that the idea of evanescent coupling permits use of a thin film geometry, whereby thick films and their associated inefficiencies can be avoided. Specifically, QDs are stabilized in the cladding of a waveguide and excited by the evanescent field of the guided modes rather than by direction illumination. As an additional advantage, the pump light and emission can be spatially distant; this decoupling promises to alleviate engineering headaches related to heat dissipation.