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The alignment properties and distribution of flow speed during Poiseuille flow through a microchannel of a nematic liquid crystal in a cell with homeotropic surface alignment has been measured using a combination of conoscopy, fluorescence confocal polarizing microscopy, and time-lapse imaging. Two topologically distinct director profiles, with associated fluid velocity fields, are found to exist with the preferred state dictated by the volumetric flow rate of the liquid crystal. The results show excellent agreement with model data produced using the Ericksen-Leslie nematodynamics theory.

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Optical excitation of a half leak guided modes has been used for characterising in detail the optical tensor profile in a homeotropically aligned ferroelectric liquid crystal (SCEB) layer.In the S, phase it is found, by careful fitting of multilayer Fresnel theory to angle dependent transverse magnetic to transverse electric conversion reflectivity data, thatat 1°C above the S; to S, phase transition there is a finite pre-tilt of the S, layers.Further fitting of similarly recorded data in the Sy phase gives details of the cone angle and the chiral pitch of the Sz phase. These results not only serve to obtain material parameters for this Sz phase but also illustratee fully the enormous potential of the half leaky guided mode technique.