Influence of the substrate material on the knife-edge based profiling of tightly focused light beams

TL;DR

This study investigates how the substrate material affects the accuracy of knife-edge beam profiling for tightly focused light, revealing that substrate choice significantly influences measurement outcomes.

Contribution

The paper introduces an analytical model showing the substrate's impact on knife-edge beam profiling and validates it with numerical and experimental results.

Findings

Substrate material alters beam projection reconstructions.

Physical effects cause polarization-dependent beam shifts.

Beamwidth measurements vary with substrate and knife-pad height.

Abstract

The performance of the knife-edge method as a beam profiling technique for tightly focused light beams depends on several parameters, such as the material and height of the knife-pad as well as the polarization and wavelength of the focused light beam under study. Here we demonstrate that the choice of the substrate the knife-pads are fabricated on has a crucial influence on the reconstructed beam projections as well. We employ an analytical model for the interaction of the knife-pad with the beam and report good agreement between our numerical and experimental results. Moreover, we simplify the analytical model and demonstrate, in which way the underlying physical effects lead to the apparent polarization dependent beam shifts and changes of the beamwidth for different substrate materials and heights of the knife-pad.