Designing chromatic optical retarder stacks for segmented next‐generation easySTED phase plates

Authors:

Johann Engelhardt, Beatrice Ellerhoff, Clara-Marie Gürth, Steffen J Sahl, Stefan W Hell

Keywords:

Fluorescence nanoscopy, STED, RESOLFT, intensity minimum, phase plate, polarization

Abstract:

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 fiber 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.

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