Reference : Dynamic and complex optical patterns from colloids of cholesteric liquid crystal droplets

	Document type :	Scientific congresses, symposiums and conference proceedings : Paper published in a journal
	Discipline(s) :	Engineering, computing & technology : Materials science & engineering
	To cite this reference:	http://hdl.handle.net/10993/20840

Title :	Dynamic and complex optical patterns from colloids of cholesteric liquid crystal droplets
Language :	English
Author, co-author :	Noh, Junghyun [University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit >]
	Drevensek-Olenik, Irena [University of Ljubljana > Faculty of Mathematics & Physics]
	Yamamoto, Jun [Kyoto University > Department of Physics]
	Lagerwall, Jan [University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit >]
Publication date :	2015
Journal title :	Proceedings of the SPIE
Publisher :	Bellingham, Wash. : The International Society of optical engineering.
Volume :	9384
Special issue title :	Emerging Liquid Crystal Technologies X
Pages :	93840T1-9
Peer reviewed :	No
On invitation :	Yes
Audience :	International
e-ISSN :	1996-756X
Event name :	SPIE Opto
Event date :	February 7-12, 2015
Event organizer :	SPIE
Event place (city) :	San Francisco
Event country :	USA
Keywords :	[en] Cholesteric liquid crystals ; colloidal crystals ; selective reflection ; Bragg reflection ; photonics ; pattern formation ; microfluidics
Abstract :	[en] 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.
Funders :	National Research Foundation (NRF, Korea), NRF-JSPS
Name of the research project :	grant numbers 490-20110016 and 490-20130024
Target :	Researchers ; Professionals ; Students
Permalink :	http://hdl.handle.net/10993/20840
DOI :	10.1117/12.2180516
Other URL :	http://dx.doi.org/10.1117/12.2180516
Mentions required by the publisher for OA :	JungHyun Noh, Irena Drevensek-Olenik, Jun Yamamoto, and Jan P. F. Lagerwall, “Dynamic and complex optical patterns from colloids of cholesteric liquid crystal droplets,” Emerging Liquid Crystal Technologies X, Liang-Chy Chien, Harry J. Coles, Hirotsugu Kikuchi, Ivan I. Smalyukh, Editors, Proc. SPIE 9384, 93840T (2015). Copyright 2015 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

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