Characterization of optical absorption and polarization dependence of single-layer graphene integrated on a silicon wire waveguide

Optical absorption efficiency of graphene integrated onto a silicon photonic platform was characterized at around 1.55-µm optical telecommunications wavelength. Micro-Raman spectroscopy performed after the completion of all fabrication processes confirmed that transferred chemical-vapor-deposited graphene is a single layer (>90% coverage) without any significant damage. Absorption efficiencies of the single-layer graphene (SLG) on a silicon wire waveguide, obtained by measuring different lengths (cutback method) of the SLG from 2.5 to 200 µm, were 0.09 and 0.05 dB/µm for TE- and TM-polarized light. The unusual relationship in the polarization dependency can be explained by strong surface-plasmon-porlariton support in the TM mode.