abberior dyes & labels
Designing chromatic optical retarder stacks for segmented next-generation easySTED phase plates
Johann Engelhardt, Beatrice Ellerhoff, Clara-Marie Gürth, Steffen J Sahl, Stefan W Hell
fluorescence nanoscopy, intensity minimum, phase plate, polarisation, RESOLFT, STED
Fluorescence nanoscopy methods based on the RESOLFT principle, such as beam-scanning STED nanoscopy, require the co-alignment of optical beams for molecular state (on/off) switching and fluorescence excitation. The complexity and stability of the beam alignment can be drastically simplified and improved by using a single-mode fibre as the sole light source for all required laser beams. This in turn then requires a chromatic optical element for shaping the off-switching beam into a focal-plane donut while simultaneously leaving the focal intensity distributions at other wavelengths shaped as regular focal spots. Here we describe novel designs of such so-called ‘easySTED phase plates’ and provide a rationale how to find the desired spectral signature for combinations of multiple wavelengths.