title: Optical two-beam coupling for a surface-induced photorefractive effect in undoped liquid crystals.
abstract: We report beam-coupling measurements of undoped nematic planar cells, for which the surface-induced photorefractive effect (SIPRE) has been confirmed to be due to photoelectric interface activation. We show that the energy transfer strongly depends on experimental geometry. Diffraction efficiency and beam-coupling analyses suggest that the unusual local and (or) nonlocal behavior can be ascribed to an additional in-phase-modulated longitudinal electric field component, unaccountable by standard photorefractivity. We consider a simple charge distribution model of the SIPRE, which produces a space-charge field having two orthogonal modulated components, in phase and pi/2 out of phase. Through the liquid crystal's electric response, the exploited geometries verify the presence of the two components.
authors.affiliation: Dipartimento di Fisica, Liquid Crystals Laboratory, Istituto Nazionale per la Fisica della Materia, Universitá della Calabria, I-87036 Arcavacata di Rene (CS), Italy.
authors.forename: Pasquale
authors.initials: P
authors.lastname: Pagliusi
authors.forename: Gabriella
authors.initials: G
authors.lastname: Cipparrone