Concentric re-emission pattern from a planar waveguide with a thin uniform luminescent layer.

When a beam of light excites a single spot on a thin luminescent layer embedded in a planar waveguide, a concentric re-emission pattern is observed. An analytical expression is formulated by following the series of events in the waveguide: generation of angle-dependent photoluminescence spectra, reflection at the waveguide-air boundary, absorption by the luminescent layer, and generation of next-generation photoluminescence. The formula reproduces the peak radii observed in the experiments with some organic dyes. It provides insights for the re-emission events in a luminescent solar concentrator and the cross talk in an energy-harvesting display based on photoluminescence.