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Proceedings Paper

Dynamic and complex optical patterns from colloids of cholesteric liquid crystal droplets
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Paper Abstract

Drops or shells of a planar-aligned short-pitch cholesteric liquid crystal exhibit unique optical properties due to the combination of Bragg reflection in the cholesteric helix and a radial orientation of the helix axis. If such a droplet is illuminated from above, light is reflected into a continuous set of cones, the opening angles of which depend on where on the droplet the light hits its surface. For the wavelength that fulfills the Bragg condition the reflection is dramatically enhanced, yielding the light cones colored. A photonic cross communication scheme arises for certain angles, reflecting light back to the observer from a different droplet than the one originally illuminated. This gives rise to an intricate pattern of colored and circularly polarized spots. A number of interesting applications may be developed based on this pattern, e.g. in identification and authentication devices. We have carried out a detailed spectrophotometric analysis of the patterns, localized to individual spot maxima. A quantitative comparison between the measured spectra and the reflection wavelength expected from a model for the pattern generation allows us to conclude that the droplets are in fact not spherical but slightly ellipsoidal.

Paper Details

Date Published: 11 March 2015
PDF: 9 pages
Proc. SPIE 9384, Emerging Liquid Crystal Technologies X, 93840T (11 March 2015); doi: 10.1117/12.2180516
Show Author Affiliations
JungHyun Noh, Univ. du Luxembourg (Luxembourg)
Irena Drevensek-Olenik, Univ. of Ljubljana (Slovenia)
Jun Yamamoto, Kyoto Univ. (Japan)
Jan P. F. Lagerwall, Univ. du Luxembourg (Luxembourg)

Published in SPIE Proceedings Vol. 9384:
Emerging Liquid Crystal Technologies X
Liang-Chy Chien; Harry J. Coles; Hirotsugu Kikuchi; Ivan I. Smalyukh, Editor(s)

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