Determination of wavelength dependences of ordinary and extraordinary refractive indices from a single Fabry-Perot interference spectrum

Abstract

An improved interference method is proposed to determine ordinary and extraordinary refractive index dispersions of nematic liquid crystals (LCs). In this method, an LC cell coated with a thin metal layer is used as a Fabry-Perot interferometer which shows us a sharp transmission fringe. In spite of measuring ordinary and extraordinary components, the LC cell, polarizers and other equipment are not rotated during experiment. The index evaluation from a single spectrum avoids errors depending on the measurement position owing to non-uniformities of molecular orientation and cell thickness because we can obtain the two indices at exactly the same position. This system can adapt to a wide frequency range, and does not require any specific wavelength light source or laser. We demonstrate the determination of ordinary and extraordinary refractive index dispersions of a nematic liquid crystal in the visible and near-infrared regions.