Optically induced light modulation in epoxy-based polymer dispersed liquid crystals

Abstract

The thermo-optical properties of polymer dispersed liquid crystal (PDLC) films (Epoxy/E7) are investigated and described. The experimental evidence for thermally induced optical bistability at the nematic-isotropic phase transition is presented by analysing the switching effect from the scattering state to the transmission one and vice versa. Optically induced light modulation by a pump beam (Ar+ laser) is probed by a weak He–Ne beam when the two laser beams are incident on the sample simultaneously. The dependence of the hysteresis loop on both the modulation frequency of the incident beam and the sample temperature are also studied. For this PDLC composition, the light intensity and the sample temperature are used to control or adjust the nonlinear part of its refractive index, and the thermo-optical behaviour of the material is strongly affected by both parameters. Our experimental results show such thermally and optically induced light modulation, and demonstrate that the PDLC film used is promising for possible applications in thermo-optical switches, temperature sensoring, or designing devices with thermally modulated light.