New sensing strategies based on surface modes in photonic crystals

During the past decade the investigations on the use of optical nanostructures for sensing applications has become an active area of research. The near-field interactions of sensed analytes with optical modes sustained by photonic crystals have resulted in a general increase of the detection performances, both in labelled and label-free configurations. As a particular case, one-dimensional photonic crystals (1DPC), represents an interesting opportunity for enhancing the light-matter interaction mediated by Bloch Surface Waves (BSWs). In this chapter we introduce the concept of surface modes on planar and corrugated 1DPC based on dielectric stratified structures providing several illustrative examples in sensing applications. The use of 1DPC surface modes as optical transducers presents some advantages, such as spectral and polarization tunability and low losses. Moreover, functionalizing layers tailored for specific applications can be included within the definition of the photonic crystal itself, thus leading to hybrid organic/inorganic structures. Some recent advances on the use of a photonic crystal platform for biosensing applications are presented and discussed, including label-free and improved fluorescence-based approaches wherein the intimate coupling of organic emitters to BSWs can be fruitfully exploited.