We have developed some high birefringence (Delta n greater than or similar to 0.3 at lambda = 633 nm) and relatively low viscosity nematic mixtures using isothiocyanato tolanes. These mixtures exhibit a high figure-of-merit (FoM) which is desirable for reducing the device response time. Using such a high FoM liquid crystal mixture in a 2-mu m homogeneous cell, we demonstrate a 1 pi phase modulator at lambda = 633 nm with submillisecond response time.