  In this letter we exploit the extended coherence length of mixed
plasmon/exciton states to generate active metasurfaces. For this purpose,
periodic stripes of organic dye are deposited on a continuous silver film.
Typical metasurface effects, such as effective behavior and geometry
sensitivity, are measured for periods exceeding the polaritonic wavelength by
more than one order of magnitude. By adjusting the metasurface geometry,
anisotropy, modified band structure and unidimensional polaritons are
computationally simulated and experimentally observed in reflectometry as well
as in emission.
