Comparison of STED, confocal and optical microscopy of ultra-short pitch cholesterics

The goal of this work is to compare experimentally achievable resolution limits of three different optical microscopy techniques in chiral nematic liquid crystals: (i) standard optical polarisation microscopy, (ii) confocal optical microscopy using fluorescently labelled liquid crystal and (iii) Stimulated Emission Depletion (STED) microscopy using custom synthesised fluorescent dyes. The microscopy experiments on micrometre thin LC samples reveal that the lateral resolution better than ~90 nm can be achieved using STED technique in thin layers of liquid crystals. The standard optical microscopy with index matching between the objective and the sample cover glass in combination with short-wavelength narrow-band optical illumination is quite competitive to STED technique and optical details as small as ~150 nm could be resolved using aberration limited microscope.