Estimation of order parameter of a liquid crystal variable retarder using Haller's approximation.

We use a liquid crystal variable retarder (LCVR) for polarization modulation of the input beam in a polarimeter intended for solar observations. It is known that the retardance of LCVR depends on the voltage and temperature. Voltage at a constant temperature is used for fast modulation.

Experimentally determined r13 electro-optic coefficient for a lithium niobate crystal.

Experimental determination of the electro-optic coefficient r13 of a lithium niobate crystal is described. The crystal in this experiment is z cut, used as a substrate for a Fabry-Perot etalon. I computed the r13 coefficient from the measured voltage tuning curve of the Fabry-Perot etalon.