Interference Ring Patterns from Cholesteric Liquid Crystal Cells

Abstract

An interference ring pattern is observed from cholestric liquid crystal cells. Quételet scattering light interference contributes to the ring, and defect walls among uniform aligned cholesteric liquid crystal domains serve as scatterers in the cell. A simple theory is developed to explain the observed scattering light interference in the far field condition. Changes in interference ring intensities and optical microscope images are investigated. Experimental results show that cell thickness and applied voltage significantly affect the number of defects and hence affect the ring intensity and the clarity of the observed ring pattern. The multiple diffuse reflections and the polarization changes of the incident light beams in the liquid crystal material affect the contrast ratio in the ring image, and the location of a specific order can be directed by controlling the incident angle. The results introduce the possibility of realizing defects and impurities in a liquid crystal device using scattering light interference. The liquid crystal cells may also serve as candidates for producing a conical interference ring.