Study of liquid crystal phase retardation of wave plate under external electric field

As one kind of phase delay devices, wave plates can provide an optical retardance between two orthogonal components of incident polarized light, and change the light’s polarization state. It’s a kind of important polarization devices. Liquid crystal wave plate is a new type of phase delay devices, which is based on liquid crystal (LC) electrically controlled birefringence effect, and is also known as liquid crystal variable phase retarder(LCVR). LCVRs are being widely used as replacements of other typical retarders in optical systems because of their capacity to provide a real time and controlled variable optical retardance between two orthogonal components of incident polarized light by means of an applied voltage, and without the need of any moving mechanical parts. They also have other advantages, such as low driven voltage and power consumption, and simple structure. For phase delay devices, the retardation is a very important parameter, which can largely impact the precision of optical systems. Since LCVRs’retardation is controlled by voltage, to improve the optical system’s precision, it’s of a very important significance to study the LCVRs’retardation change characteristics under the applied voltages.The main research of this paper includes:1. Based on liquid crystal’s continuous elastic theory, a numerical model and calculation program to calculate LCVRs’retardation under the external electric field is proposed. And utilizing the model, retardations of kinds of LCVRs with different molecule arrangements cell thicknesses, LC material parameters and wavelength are simulated.2. Based on the measuring method with a quarter wave plate, a measuring system with high compatibility and good precision is eastablished. Comparing with the traditional systems, the new design system is effective with variety modes of phase delay devices, which is a big advantage.3. Kinds of LCVRs are made.4. By the measuring system established in the paper, various types of LCVRs’ phase retardations under external electric field are experimental measured. The results prove the effectiveness and correctness of the numerical model and calculation program proposed in the paper.