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Abstract: Nowadays the focus concerning electromagnetic surface modes is strictly related to the manipulation of light.
It means that the core concept lies in the capability of nanostructures made of dielectric, metallic, and hybrid materials of
concentrating electromagnetic field on length scales smaller than the diffraction limit, thus obtaining huge field intensity enhancement.
Entering into more physical details, surface plasmons are electromagnetic modes combined to coherent oscillations of free
electrons in metals that have been deeply investigated for improving the performances of photonic and optoelectronic devices being, in
addition, very sensitive to local refractive index variations in the surrounding medium and such a feature is crucial for optical sensing
technologies.
Besides metal-dielectric interfaces and metallic nanostructures, another important means to manipulate and modify light propagation is
represented by photonic crystals (PhCs). On this hand, Bloch surface waves (BSWs) are propagation modes at the surface of a distributed
Bragg reflector characterized by a frequency within the photonic band gap, so light cannot propagate through the periodic structure, and
near-interface localization is achieved owing to total internal reflection at the surface of the bounding medium.
Both platforms are very interesting to focus on pushing the detection to the limit of sensitivity by controlling the local electromagnetic
environment being successfully applied to label-free chemical and biological sensing, where it has proven to be an excellent method for
sensing DNA hybridization, protein binding events, and even single molecules. In addition, it bears great promise for rapid
identification of viruses and bacteria, potentially enabling whole-organism fingerprinting.