Controlled fluorescence emission via surface modes on dielectric and metallo-dielectric multistack

An alternative method to plasmon techniques for the enhancement, control and detection of fluorescence is proposed. The role of the metallic layer is played by a silicon-based one-dimensional photonic crystal that can sustain Bloch surface waves (BSWs), which can be regarded as the dielectric analogue of surface plasmon polaritons (SPPs) for metals. Throughout the paper we explore the route that leads to an enhanced, directionally-controlled and selfreferencing fluorescence-detection scheme. We first consider a 1DPC that is functionalized with a thin, flat and homogeneous polymeric layer decorated with a fluorescent dye. The enhancement of the BSW-coupled fluorescence emission is studied against a similar scheme that uses a common thin glass coveslip. An enhancement as large as 560 is found. We further investigate the BSW coupling of the illuminating laser light into 30-nm thin polymeric waveguides. Imaging the BSW-coupled emitted fluorescence through the leakage radiation microscopy is used for the purpose. The possibility of coupling BSWs into nanometric guiding ridges makes feasible the design of a spatially-resolved and multiplexing fluorescence-detection scheme, which can be most useful for self-referencing in the biosensing field. We conclude the paper by investigating the effects on the fluorescence emission of a multistack that consists of a dielectric multilayer and a thin metallic layer deposited on top. The implications of using a metallo-dielectric structure for the coupling of the emitted fluorescence with BSW and SPP modes is discussed.