title: Stokes-parameter analysis of the polarization of light transmitted through a chiral nematic liquid-crystal cell.
abstract: A spectroscopic Stokes polarimeter is used to directly measure the linearly, circularly, and randomly polarized components of light obtained on transmission of unpolarized light through thick chiral nematic liquid-crystal cells in the stop band. The Stokes parameters are simulated to fit the experimental data by use of the Berreman 4 x 4 transfer matrix by means of the Jones and Stokes vectors and taking into account multiple reflections at the interfaces of the cell. Excellent agreement is obtained. The transmitted light through a commercial cell is mainly circularly polarized at normal incidence, but a significant linearly polarized component is also observed. The model shows that this results from refractive-index mismatching at the liquid-crystal-alignment-layer interface, but a small linearly polarized component remains even with optimized index matching. An improved device configuration incorporating random defects at the exit boundary of the liquid crystal gives a highly circularly polarized output with virtually no linear or unpolarized components.
authors.affiliation: Department of Physics, University of Hull, Cottingham Road, Hull HU6 7RX, UK.
authors.forename: Kai L
authors.initials: KL
authors.lastname: Woon
authors.forename: Mary
authors.initials: M
authors.lastname: O'Neill
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Richards
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Aldred
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Kelly