Measurement of birefringence of nematic liquid crystal material by multiple-wavelength interferometry using nearly
Abstract:
We report the measurement of birefringence of nematic liquid crystal (NLC) material using multiple-wavelength interferometry. A nearly common path single-stage Mach-Zehnder interferometer was used for recording interferograms of high stability. The Fourier transform fringe analysis technique was used to reconstruct the two-dimensional phase maps of interferograms consisting of the entire active area of the liquid crystal cell. Change in phase as a function of applied voltage to a liquid-crystal cell was measured for blue, green, and red color laser light, keeping the temperature constant during the experiment. From the change in phase, the birefringence for three colors, i.e., red, green, and blue light, was determined. It is found that the birefringence of NLC material for red, green, and blue colors decreases with the increase in wavelength in the visible range. The present method is noncontact, nonmechanical scanning and highly stable due to a common path interferometer.
