Sub-diffraction-limit Fourier-plane laser scanning microscopy

Resolving features that are smaller than the diffraction limit is an intricate yet fascinating challenge that many scientists are working on. Heretofore, most techniques that can circumvent this resolution limit, such as super-resolution microscopy or electron microscopy, lead to a permanent modification of the sample. Consequently, noninvasive approaches are of special interest. Here we introduce an all-linear far-field measurement and imaging modality for the investigation of ensembles of sub-diffraction-limit sized nanostructures. Our technique is based on laser scanning, polarization resolved Fourier-plane measurements and optimizing a theoretical model of the investigated system to resemble the measurement. As an experimental demonstration, we apply this method to gold nanoparticle clusters and derive their positions and respective sizes with an accuracy down to several nanometers, even if multiple particles are located directly adjacent. Our technique showcases the capabilities of microscopy techniques when combined with careful analysis of light scattered off a specimen. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement