High-frequency dielectric relaxation of liquid crystals: THz time-domain spectroscopy of liquid crystal colloids
Oh-e, Masahito; Yokoyama, Hiroshi; Koeberg, Mattijs; et al.Hendry, Euan; Bonn, Mischa
Date: 13 November 2006
Journal
Optics Express
Publisher
Optical Society of America
Publisher DOI
Abstract
Terahertz time-domain spectroscopy has been used to study the dielectric relaxation of pure 4’–n-pentyl–4–cyanobiphenyl (5CB) liquid
crystal (LC) and its mixtures with 10 µm SiO2 particles in the frequency
range 0.2–2 THz. For the pure sample, we find that spatial inhomogeneities
consisting of oriented domains, comparable in size ...
Terahertz time-domain spectroscopy has been used to study the dielectric relaxation of pure 4’–n-pentyl–4–cyanobiphenyl (5CB) liquid
crystal (LC) and its mixtures with 10 µm SiO2 particles in the frequency
range 0.2–2 THz. For the pure sample, we find that spatial inhomogeneities
consisting of oriented domains, comparable in size to our probe area (~1
mm2), cause a large scatter in the measured dielectric function, due to varying
contributions from the ordinary and extraordinary components. In the
LC/particle mixtures, ordering of the LC at the surface of the SiO2 particles
results in a break-up of these domains, giving rise to a spatially much more
homogeneous dielectric response. The inferred dielectric function can be
interpreted using effective medium theory and the Debye relaxation model.
We observe this stabilizing effect for interparticle distances < ~30 µm,
setting a lower limit for the size of oriented domains in the bulk LC.
Physics and Astronomy
Faculty of Environment, Science and Economy
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