Arbitrary-to-arbitrary polarization controller using nematic liquid crystals

In the study of lightwave systems, polarization related effects have become important considerations. This has led many researchers to focus on developing practical means of controlling the state of polarization of light. This paper demonstrates a polarization controller, consisting of a stack of three homogeneous nematic liquid crystal cells, that is capable of changing any state of polarization of light from one arbitrary state to another. by adjusting the voltages applied across each cell, the state of polarization can be controlled. The mathematical algorithm and the principles of this polarization controller are developed in the framework of the Stokes parameters, allowing an easy visualization and better understandings using Poincare sphere representation. In addition to providing the transformation functions for converting an arbitrary input polarization state to any output state, this paper describes the experiments that were carried out to illustrate and confirm the arbitrary polarization transformations.