We have developed and experimentally demonstrated an actively tunable infrared filter that enables modification of the amplitude of reflected long-wave-infrared light. Tunability results from plasmons excited in an unpatterned sheet of chemical-vapor-deposition grown graphene. Through conventional gating using a periodic metal grating, the Fermi level of the graphene can be modified to change the plasmonic response, resulting in changes to reflectance. The filter enables simultaneous modification of two distinct spectral regions between 600 and 1600 cm-1, whose positions are controlled by the device geometry and graphene plasmon dispersion. Within these bands, the reflected amplitude varies by over 15% and reflectance minima can be shifted over 90 cm-1. As demonstrated though electromagnetic simulations, tuning arises from graphene plasmons excited within the graphene via coupling through the metallic grating. The tuning range is determined by a combination of graphene properties, device structure, and the surrounding dielectrics. Using these parameters, the device architecture demonstrated here is applicable to a broad range of infrared wavelengths.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.