Phase modulation and ellipticity of the light transmitted through a smectic C* layer with short helix pitch

Abstract

A chiral ferroelectric smectic C* liquid crystal (FLC) with the helix pitch p ₀ = 330 nm was developed to avoid any scattering of visible light when the helix is not unwound over a certain limit. Planar cells with different FLC layer thickness (16 and 44 μm) have been assembled with helix axis parallel to the glass plates and aligned along the rubbing direction. The ellipticity of the light passing through the cells vs. the electric field was investigated, and a method for evaluating the electrically controlled birefringence via ellipticity measurements has been established. We have found that the FLC cell is an optical retardation layer driven by the electric field, the effective birefringence being proportional to the square electric field. The physical origin of the electrically controlled phase shift of the light passing through the FLC layer has been analysed.

Keywords:

• chiral dopant
• ferroelectric liquid crystal
• helix pitch
• ellipticity
• phase shift

Acknowledgements

The authors are very grateful to Ibrahim Abdulhalim, Ben-Gurion University of the Negev - Faculty of Engineering Sciences, for very useful suggestions. The work was supported by the Russian Foundation of Basic Research, grants NN 08-03-90009, 08-02-01074-a and grants: 07-07-91582-ASP_a, 08-03-90009-Bel_a, 07-02-96610-p; it was partially funded by Fondazione Cassa di Risparmio di Torino (FCRT) in the frame of the bilateral project Piemonte-Russia “Nanotecnologie per le industrie elettromeccaniche, dell'informazione e del medicale (FCRTnano)”. One of the authors (C.A.R. Yednak) acknowledges a grant from Coordenadoria de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Paranà, Brasil; another author (S. Torgova) acknowledges Politecnico di Torino, Dipartimento di Fisica, for financial support.