Abstract

We report the study of nonlinear transparency effect given by the light-induced creation of an isotropic droplet in a twisted nematic liquid crystal cell bounded by two dichroic polarizers. It is well known that a couple of crossed (parallel) polarizers is opaque (transparent). However, if we insert a π/2 twisted nematic liquid crystal cell between them the behavior of the device is reversed since the cell, because of the adiabatic following of the light wave traveling along the twisted structure, acts as a tr/2 polarization rotator, so that the device is 'transparent (opaque) for crossed (parallel) polarizers. When the nematic-isotropic phase transition of the liquid crystal occurs, the system goes back to the usual behavior, and the sample switches to an opaque (transparent) state. Another way to break the twisted configuration is to apply an electric field in the direction orthogonal to the cell: the nematic liquid crystal configuration changes from twisted to horneo tropic.

© 1996 Optical Society of America