In-line polarizers and filters made of metal-coated tapered fibers: resonant excitation of hybrid plasma modes

In-line single-mode-fiber (SMF) filters and polarizers require the interaction of electric fields which, in principle, are essentially confined to the fiber core. The reduction of the core and cladding diameters in a tapered fiber cause the evanescent field to extend beyond the outer boundary. Thus, when a metal film is evaporated on a tapered fiber, the surface plasma modes cause coupling to the fiber mode. Our experimental and theoretical results demonstrate that such coupling leads to the resonant excitation of surface plasma modes and allows for the design of filters, polarizers, and sensors.