Surface plasmon, surface wave, and enhanced evanescent wave microscopy

This chapter gives an overview of the formation of evanescent fields excited by an objective lens. We discuss some of the different phenomena that emerge at the interface between a high index couplant and relatively low index sample. We show how surface plasmons are excited in the presence of a thin gold film. We discuss the application of surface waves microscopy with excitation of microscopic objectives and conclude that significant applications reside in the area of localized measurement of refractive index. A key challenge in surface microscopy is to maintain the high spatial resolution in the presence of waves that propagate relatively long distances along the sample surface, methods to achieve this high resolution are discussed in some detail. For cellular imaging while surface plasmons can give good images, evanescent waves generated by excitation from light incident above the critical angle can produce very high quality images of the sample surface, without needing to address the problems introduced by lateral propagation of the waves. Finally, we discuss potential new directions for imaging and localized sensing using these waves.