Polar structure of disclination loops in nematic liquid crystals probed by second-harmonic-light scattering

Angle-resolved,second-harmonic-lightscattering(SHLS)measurementsarereportedforthreedifferentclasses ofthermotropicnematicliquidcrystals(NLCs):polarandnonpolarrodlikecompoundsandabent-corecompound. Results revealing well-defined scattering peaks are interpreted in terms of the electric polarization induced by distortions of the nematic orientational field (“flexopolarity”) associated with inversion wall defects, nonsingular disclinations, analogous to Neel walls in ferromagnets, that often exhibit a closed loop morphology in NLCs. Analysis of the SHLS patterns based on this model provides a “proof-of-concept” for a potentially useful method to probe the flexopolar properties of NLCs.