Planar Resonant Structures for Biosensing Applications

This thesis presents theoretical studies of spontaneous Raman scattering and coherent anti-Stokes Raman scattering (CARS) from molecules on resonant multilayer structures. A simple isotropic model is exploited to describe the Raman polarizability of molecules, and a Green function method is used to calculate the scattering fields from molecules. The response of the multilayer structures to incident fields is characterized through a transfer matrix method that allows derivation of semi-analytic expressions for Raman cross sections and CARS powers in terms of Fresnel coefficients of the structures. The main focus in this thesis is on purely dielectric structures, especially truncated periodic multilayers that support Bloch surface waves (BSW). The dispersion relation of these resonances can be engineered to allow resonant coupling of all incoming and outgoing fields in spontaneous Raman scattering and CARS. As a result, the spontaneous Raman cross section is enhanced up to 10^6 in particular directions and the CARS power from monolayers is significant for millimeter wide incident beams. I compare the spontaneous Raman and CARS powers from thin layers of molecules on multilayer structures supporting BSWs and show how these ratios scale when the molecules form lipid bilayers. I present experimental realizations of surface enhanced Raman scattering from acetone and sulphur molecules on BSW structures and show that the excitation of BSWs results in observation of Raman lines that are not observable on a bare prism. I use a Fresnel coefficient pole analysis to develop a systematic strategy for designing multilayer structures that support long range surface plasmons (LRSPs) and design a periodic multilayer structure that supports a LRSP with propagation length about 2 mm. With a view toward biosensing applications, I derive semi-analytic expressions for a standard surface sensing parameter in arbitrary planar resonant structures and compare the exact and approximate calculations for the designed LRSP structure.Ph.D.2016-06-17 00:00:0