| Abstract: | An actively tunable optical filter can control the amplitude of reflected
infrared light. The filter exploits the dependence of the excitation
energy of plasmons in a continuous and unpatterned sheet of graphene, on
the Fermi-level, which can be controlled by conventional electrostatic
gating. An exemplary filter enables simultaneous modification of two
distinct spectral bands whose positions are dictated by the device
geometry and graphene plasmon dispersion. Within these bands, the
reflected amplitude can be varied by over 15% and resonance positions can
be shifted by over 90 cm.sup.-1. Electromagnetic simulations verify that
tuning arises through coupling of incident light to graphene plasmons by
a nanoantenna grating structure. Importantly, the tunable range is
determined by a combination of graphene properties, device structure, and
the surrounding dielectrics, which dictate the plasmon dispersion. Thus,
the underlying design is applicable across a broad range of infrared
frequencies. |