CAVITY-MODE SELECTION IN SPONTANEOUS EMISSION FROM ORIENTED MOLECULESIN A MICROPARTICLE

We observe preferential cavity-mode selection in spontaneous emission by oriented molecules at the surface of a microparticle. Polarization- analyzed images of a levitated microdroplet containing surface active molecules reveal a well-defined system in terms of molecular position and orientation. The measured fluorescence spectrum is compared with t hat of a semiclassical emission-rate-enhancement model that treats the coupling between an excited state and Mie resonances as an oscillatin g dipole interacting with its self-scattered field. By comparing resul ts obtained with this theory with the relative strengths of TE to TM m odes measured in the emission spectrum, we show that one can elucidate the heterogeneity of a particle from this resonant structure and dete rmine the orientation of the emission moments relative to the phase bo undary. (C) 1997 Optical Society of America.