Polarization-dependent photonic crystal fiber optical filters enabled by asymmetric metasurfaces.

We demonstrate in-fiber polarization-dependent optical filter by nanopatterning an asymmetric metallic metasurface array on the end-facet of polarization-maintaining photonic-crystal fibers. The asymmetric cross-typed nanoslit metasurface arrays are fabricated on the core of the optical fiber using the focused ion beam milling technique. Highly polarization- and wavelength-dependent transmission with transmission efficiency of ∼70% in the telecommunication wavelength was observed by launching two orthogonal linear-polarization states of light into the fiber. Full-wave electromagnetic simulations are in good agreement with the experimental results. These advanced meta-structured optical fibers can potentially be used as novel ultracompact in-fiber filters, splitters, and polarization converters.