Determination of nematic polar anchoring from retardation versus voltage measurements

The popular “high-electric-field” technique to determine the polar anchoring coefficient W of a nematic–substrate interface requires the simultaneous measurement of the capacitance and optical phase retardation of a liquid crystal cell as a function of applied voltage. We develop a generalized model that makes it possible to eliminate the capacitance measurement. The new technique, called the $\mathrm{RV}$ (retardation versus voltage) technique, requires only the measurement of retardation as a function of applied voltage, and allows for the determination of W by a linear fit over a prescribed voltage window. The technique is not sensitive to uniformity of the cell thickness, does not require patterned electrodes, and allows for the local probe of the surface. The value of W obtained by the $\mathrm{RV}$ technique is the same as W obtained by the traditional technique.