Polarization field and orientational order in liquid crystals

Abstract

Optical birefringence is a conveniently measurable quantity that is often used for determining the orientational order in uniaxial liquid crystals. The orientational order parameter is given by S = α_e − α₀/ α_|| − α_⊥ where α_e and α₀ are the polarizabilities of the medium corresponding to the extraordinary and ordinary refractive indices, α_|| and α_⊥ are the corresponding values for a perfectly oriented medium with S = 1.