Kevin G. Sullivan

Enhancement and inhibition of electromagnetic radiation in plane-layered media. I. Plane-wave spectrum approach to modeling classical effects

Using a Greens function technique and the plane-wave spectrum, we formulate a classical theory for the calculation of radiative effects for a source in the presence of a planar interface or structure. The analysis focuses on understanding the roles of radiative and nonradiative energy transfer in the coupling processes and discusses the implications of modal-induced effects. This understanding is important for the design of a class of practical applications, including enhanced-sensitivity optical waveguide sensors.

Directional, enhanced fluorescence from molecules near a periodic surface

We extend the research of Holland and Hall on the use of waveguide modes to enhance the fluorescent signal from a layer of molecules [Opt. Lett. 10,414 (1985)] by incorporating a grating into the basic sample structure. Our measurements show that the combination of the directionality imposed by the grating and the previously reported enhancement mechanism has the effect of increasing the intensity of the signal detected over a narrow angular range from a layer of fluorescing molecules by a factor of ~ 1000 over that from a reference sample. Simultaneously our method allows for both polarization and wavelength discrimination of the emitted radiation because of the characteristic nature of the incorporated grating.

Enhancement and inhibition of electromagnetic radiation in plane-layered media. II. Enhanced fluorescence in optical waveguide sensors

A classical model of radiation reaction is applied to an enhanced molecular-fluorescence system incorporating an optical waveguide. The mechanisms responsible for the enhanced-fluorescence phenomena are identified, and the magnitude and guide-thickness dependence of the enhancement are determined numerically and shown to be in good agreement with previously reported experimental results.

Green's function approach to the coupled-amplitude equations for codirectional coupling☆

A scalar Greens function technique is used to obtain the coupled-amplitude equations for copropagating, transverse electric polarized waves in the parallel waveguide, or directional coupler, geometry. The results are briefly compared to those from conventional formulations, and extension of the technique to transverse magnetic polarized waves is discussed.