  In this paper, we investigate the possibility to excite Bloch surface waves
(BSWs) on the tip of single-mode optical fibers. Within this framework, after
exploring an idealized, proof-of-principle grating-coupling-based scheme for
on-tip excitation of BSWs, we focus on an alternative configuration that is
more robust with respect to fabrication-related non-idealities. Subsequently,
with a view towards label-free chemical and biological sensing, we present a
specific design aimed at enhancing the sensitivity (in terms of wavelength
shift) of the arising resonance with respect to changes in the refractive
properties of the surrounding environment. Numerical results indicate that the
attained sensitivities are in line with those exhibited by state-of-the-art
plasmonic bioprobes, with the key advantage of exhibiting much narrower
spectral resonances. This prototype study paves the way for a new class of
miniaturized high-performance surface-wave fiber-optic devices for
high-resolution label-free optical biosensing, and represents an important step
forward in the "lab-on-fiber" technology roadmap.
