  The field of plasmonics offers a route to control light fields with metallic
nanostructures through the excitation of Surface Plasmon Polaritons (SPPs).
These surface waves, bound to a metal dielectric interface, tightly confine
electromagnetic energy. Active control over SPPs has potential for applications
in sensing, photovoltaics, quantum communication, nano circuitry, metamaterials
and super-resolution microscopy. We achieve here a new level of control of
plasmonic fields using a digital spatial light modulator. Optimizing the
plasmonic phases via feedback we focus SPPs at a freely pre-chosen point on the
surface of a nanohole array with high resolution. Digital addressing and
scanning of SPPs without mechanical motion will enable novel interdisciplinary
applications of advanced plasmonic devices in cell microscopy, optical data
storage and sensing.
