  This chapter discusses a hydrodynamics-inspired approach to trap and
manipulate light in plasmonic nanostructures, which is based on steering
optical powerflow around nano-obstacles. New insights into plasmonic
nanofocusing mechanisms are obtained by invoking an analogy of the 'photon
fluid' (PF). By proper nanostructure design, PF kinetic energy can be locally
increased via convective acceleration and then converted into 'pressure' energy
to generate localized areas of high field intensity. In particular, trapped
light can be molded into optical vortices -tornado-like areas of circular
motion of power flux - connected into transmission-like sequences. In the
electromagnetic theory terms, this approach is based on radiationless
electromagnetic interference of evanescent fields rather than on interference
of propagating waves radiated by the dipoles induced in nanoparticles. The
resulting ability to manipulate optical powerflow well beyond the diffraction
limit helps to reduce dissipative losses, to increase the amount of energy
accumulated within a nanoscale volume, and to activate magnetic response in
non-magnetic nanostructures. It also forms a basis for long-range on-chip
energy transfer/routing as well as for active nanoscale field modulation and
switching.
