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

ABSTRACT

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.

Graphical abstract

KEYWORDS:

• Sections
• STED
• optical microscopy
• confocal microscopy
• lateral resolution
• short pitch cholesteric
• fingerprint texture

Acknowledgments

We acknowledge Dr. David Wilkes, Merck KGaA for providing the cholesteric samples used.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded by Slovenian Research Agency (ARRS) through the contracts PR-08332 (J.P.) and P1-0099 (I.M., G.P.); Javna Agencija za Raziskovalno Dejavnost RS.