Time-resolved optical waveguide spectroscopy: Application to a study of the switching process of a nematic liquid crystal under the influence of an electric field

We report a novel optical spectroscopy, time-resolved optical waveguide spectroscopy. This technique was developed in order to investigate the transient behavior of the dielectric constants of thin dielectric medium, e.g., changes of the refractive indices induced by an external trigger such as light, electric field, etc. Optical guided waves propagate in a thin dielectric medium whose optical properties, in particular film thickness and anisotropic dielectric tensor diagonals in molecular and laboratory coordinates, can be evaluated with high accuracy. We employed this technique to a nematic liquid crystal (5CB) as a thin dielectric medium, and molecular reorientation on the switching process was observed through the recording of transient waveguide patterns.