Interaction of highly focused vector beams with a metal knife-edge

TL;DR

This study combines theoretical modeling and experimental analysis to understand how highly focused vector beams interact with metal knife-edges, revealing material-dependent shifts influenced by electric field orientation.

Contribution

It introduces a theoretical model considering eigenmodes of metal-insulator-metal structures to explain the interaction, aligning well with experimental observations.

Findings

Material and sample dependent spatial shifts observed

Electric field orientation significantly affects the interaction

Theoretical eigenmode model agrees qualitatively with experiments

Abstract

We investigate the interaction of highly focused linearly polarized optical beams with a metal knife-edge both theoretically and experimentally. A high numerical aperture objective focusses beams of various wavelengths onto samples of different sub-wavelength thicknesses made of several opaque and pure materials. The standard evaluation of the experimental data shows material and sample dependent spatial shifts of the reconstructed intensity distribution, where the orientation of the electric field with respect to the edge plays an important role. A deeper understanding of the interaction between the knife-edge and the incoming highly focused beam is gained in our theoretical model by considering eigenmodes of the metal-insulator-metal structure. We achieve good qualitative agreement of our numerical simulations with the experimental findings.