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SUMMARY:Three-dimensional liquid crystalline superstructures for photonics
  (** joint talk with I-CAMP) - Ravnik\, M (University of Ljubljana)
DTSTART:20130628T080000Z
DTEND:20130628T084500Z
UID:TALK45976@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Liquid crystalline materials allow for formation of complex op
 tical and photonic patterns the superstructures- within the bulk of the ma
 terial or by adding colloidal inclusions. Memory [1]\, self-assembly [2]\,
  topology [3]\, and material flow [4] can serve as guiding and controlling
  mechanism of the structures\, offering possible competitive advantages to
  be used in complex optics and photonics. Here\, we present three dimensio
 nal colloidal and bulk liquid crystal superstructures\, as recently achiev
 ed by numerical modelling and experiments. Central to the superstructures 
 are complex conformations of topological defects\, as they can bind\, stab
 ilise\, or distort the structure. We show that 3D colloidal crystals can b
 e assembled from elastic dipoles of spherical beads in nematic liquid crys
 tals [5] or via inherently inhomogeneous order profiles in bulk and confin
 ed cholesteric blue phases [6]. Colloidal crystals are generalised to clos
 e-packed colloidal lattices\, which we show can serve as natural templates
  for defect networks [7]. Finally\, photonic bands are calculated for sele
 cted structures and possible defects in the structure are discussed [8].\n
 \n[1] T. Araki\, M. Buscaglia\, T. Bellini\, H. Tanaka\, Nature Materials 
 10\, 303 (2011). [2] P. Poulin\, H. Stark\, T. C. Lubensky\, D. A. Weitz\,
  Science 275\, 1770 (1997). [3] U. Tkalec\, M. Ravnik\, S. Copar\, S. Zume
 r I. Musevic\, Science 333\, 62 (2011). [4] A. Sengupta\, U. Tkalec\, M. R
 avnik\, J.M. Yeomans\, C. Bahr\, S. Herminghaus\, Phys. Rev. Lett. 110\, 0
 48303 (2013). [5] A. Nych\, U. Ognysta\, M. karabot\, M. Ravnik\, S. umer\
 , I. Muevič\, Nature Comm. 4\, 1489 (2013). [6] M. Ravnik\, G. P. Alexand
 er\, J. M. Yeomans\, S. Zumer\, Proc. Natl. Acad. Sci. USA 108\, 5188 (201
 1). [7] S. Copar\, N.A. Clark\, M. Ravnik\, S. Zumer\, Elementary building
  blocks of densely packed 3D colloidal lattice entangled by nematic discli
 nations\, accepted in Soft Matter. [8] M. Stimulak and M. Ravnik\, Photoni
 c bands in blue phase colloidal crystals\, to be submitted\; \n\n
LOCATION:Centre for Mathematical Sciences\, Meeting Room 2
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