Nanofocusing of UV light in aluminum V-grooves

Abstract

Using the finite difference time domain method, this paper investigates electromagnetic nanofocusing of ultraviolet light incident upon Al V-groove structures. A parametric study of the field enhancement around the V-groove tip area has been conducted through the change of groove depth, width, and the tip angle. A short-wavelength threshold of about 180 nm, lying well above the plasma wavelength of Al, has been identified, below which the electric field enhancement at the tip rapidly decreases. Through simplification of the V-groove model into a metal-dielectric-metal waveguide with gap width corresponding to depth-dependent V-groove width, modal solutions were obtained for the complex propagation constant, from which the adiabatic parameter and mode propagation length were determined. These results suggest that the decrease in propagation length with decreasing wavelength is the underlying cause of the short-wavelength threshold.