Scanning near-field optical probe with ultrasmall spot size

TLDR

The study theoretically investigates a novel light‑emitting probe for scanning near‑field optical microscopy. The probe, a fully metal‑coated dielectric tip, is modeled by solving the 3‑D vectorial Helmholtz equation with the multiple‑multipole method, and its power transmission and spot size are studied as functions of tip radius, taper angle, and metal thickness. The probe delivers a single near‑field spot with a full‑width at half maximum below 20 nm.

Abstract

A novel light-emitting probe for scanning near-field optical microscopy is investigated theoretically. The three-dimensional vectorial Helmholtz equation is solved for the new probe geometry by using the multiple multipole method. The novel probe consists of a dielectric tip that is entirely metal coated. It provides a single near-field spot that can be smaller than 20 nm (FWHM). The dependence on tip radius, taper angle, and metal thickness in front of the tip is investigated for the power transmission through the probe as well as for the spot size.