Nanosecond electric modification of order parameter in nematic and isotropic phases of materials with negative and positive dielectric anisotropy

Abstract

We demonstrate nanosecond electro-optic switching in the nematic and isotropic phases of two nematic materials, one with a negative dielectric anisotropy (HNG715600-100) and another with a positive dielectric anisotropy (8CB). In both cases, the effect is caused by the nanosecond electric modification of the order parameter (NEMOP). In NEMOP effect, the electric field is applied in such a way that the director alignment is not distorted. The NEMOP effects in the nematic phases are compared to the Kerr effects of the isotropic phases of the same two materials. Although the amplitudes of NEMOP and Kerr effects are comparable, we observe differences in temperature dependencies. We also observe that the field-induced Kerr birefringence in the isotropic phases does not follow the expected quadratic dependence on the applied field. Namely, it grows slower in the dielectrically negative material and faster in the dielectrically positive material.