Chromatic dispersion compensation of a ferroelectric liquid crystal modulator for optical switching applications

Abstract

In this work we present a characterization of the phase shift chromatic dispersion introduced by a ferroelectric liquid crystal modulator. Maximum optical contrast is obtained when the proper design wavelength illuminates the device. In this situation the modulator acts as a perfect half-wave plate. However, for many applications the illuminating sources available are different from the design one and the optical contrast is reduced. In a previous work we proposed an optimization method to increase the optical contrast ratio by illuminating the device with an optimal elliptically polarized light. Here, we explore further the optimization of the ferroelectric modulator performance as an optical switching device for different monochromatic and polychromatic sources. For that purpose we use an achromatic quarter wave-plate placed in front of the modulator. For the optimal situations, the two output states of the modulator will be almost linear and orthogonal providing a highly contrasted modulated optical signal. Experimental results are obtained using a commercially available single pixel ferroelectric liquid crystal modulator from CRL-Opto, model LCS2N-G, with an active area of 25.5×25.5 mm².