Optical anisotropy of multilayer graphene probed by coupled plasmon- waveguide resonators

The characterization of the optical constants of single layer graphene has been subject of deep investigation in the last two decades and the optical anisotropy has been discovered to be an important parameter linked to the structural defects of the plane of the carbon atoms. Using graphene loaded coupled plasmon-waveguide resonator, which offer pure transverse electric or transverse magnetic electromagnetic modes, we demonstrate the possibility to characterize the optical anisotropy using evanescent electromagnetic fields in the visible and middle infrared range of a single, double and triple layer of graphene. On the assumption that a universal opacity of graphene holds for both in-plane and out-plane electronic displacement, we extract the anisotropic coefficient of the graphene layers with an accuracy of about 20%. The results are coherent with the literature and indicate that coupled plasmon-waveguide resonator spectroscopy is a valid low-cost and simple technique for the alternative optical characterization of uniaxial anisotropic bidimensional materials.