Reversible orientation first-order transitions induced in a nematic liquid crystal by a spatially limited light beam and a low-frequency electric field

A new type of reversible orientation first-order transitions in a nematic liquid crystal (NLC) in the optical and low-frequency electric fields is studied experimentally and theoretically. It is shown that these transitions, characterised by a distinct bistability of the director field both upon variation of the light beam power P (the low-frequency electric-field voltage U = const) and the electric-field voltage U (P const), are related to a finite diameter of the light beam and the oblique incidence of the beam on the NLC.