Liquid crystal adaptive optics system for unpolarized light

Abstract

A homogeneous aligned nematic liquid crystal (LC) cell can be used to phase modulate light. It has a series of attractive characteristics of compactness, high density integration, low cost and possibility of batch production in adaptive optics. However a problem has long existed for such devices is that they may be used only to control the phase of light polarized along the LC extraordinary axis since only the extraordinary light index can be varied by the application of the electric field. For a liquid crystal adaptive optics system using for astronomical imaging, low level un-polarized light is collected by the telescope. So the high optical efficiency is important and key factor for an adaptive optics system using for compensate atmosphere turbulence. If a polarizer placed before LC, 50% of incident un-polarized light is wasted. In this paper, a simple method is detailed described for phase modulating un-polarized light. Un-polarized light can be thought of as the superposition of any two orthogonal polarization states that are mutually incoherent. Iceland-spar OE crystal split incident un-polarized light into two polarized light, two same LCs modulated these two polarized light separately. After that, both these two polarized light beam are combined using another Iceland-spar OE crystal. These double LC adaptive optics system can phase modulate all incident un-polarized light, no light intensity is wasted.