Collection of Propagating Electromagnetic Fields by Uncoated Probe

TL;DR

This study demonstrates that uncoated fiber probes can effectively collect nearfield electromagnetic signals with minimal perturbation, achieving high-resolution imaging of sub-wavelength features, unlike coated probes that distort fields.

Contribution

It provides experimental and simulation evidence that uncoated fiber probes outperform coated ones in nearfield microscopy by reducing field perturbation and improving resolution.

Findings

Uncoated probes achieve ~23 nm optical resolution.

Metallic coating distorts nearfield electromagnetic fields.

Uncoated probes successfully image second-harmonic light from sub-surface features.

Abstract

Understanding light-matter interaction at the nanoscale by observation of fine details of electromagnetic fields is achieved by bringing nanoscale probes into the nearfield of light sources, capturing information that is lost in the far field. Although metal coated probes are often used for nearfield microscopy, they strongly perturb the electromagnetic fields under study. Here, through experiment and simulation, we detail light collection by uncoated fiber probes, which minimize such perturbation. Second-harmonic light from intensely-irradiated sub-wavelength sub-surface features was imaged to avoid otherwise dominating fundamental light background, yielding clear nearfield details through a 50 nm aperture uncoated probe with ~23 nm optical resolution. Simulations shows how a metallic coating distorts optical nearfields and limits optical coupling into the probe in comparison to an uncoated probe.