Nanofocusing in the graphene-coated tapered nanowire infrared probe

We conduct analytical and numerical investigations of graphene-coated tapered nanowire probe and determine the optimal conditions and structural parameters for achieving maximal possible local field enhancement at the probe tip. Based on the adiabatic approximation, analytic methods are adopted in the investigation of modal performances and field enhancement of the probe, showing good consistence with the rigorous numerical simulations up to the taper angle near 24 degrees. Both the adiabatic theory and numerical simulation have shown the existence of optimal conditions and structural parameters. The dependencies of tip field enhancement as well as the optimal structure parameters on geometric parameters, chemical potential, nanowire permittivity, and tip radius have been intensively investigated with the electric field amplitude and can be enhanced as high as 24 times. The proposed probe and the corresponding discussion may have promising applications for single molecule detection, measurement, and nanomanipulation technique. (C) 2015 Optical Society of America