Complete polarization control of light from a liquid crystal spatial light modulator

Ignacio Moreno,David Sand,Jeffrey A Davis,Don M Cottrell,Travis M Hernandez

doi:10.1364/oe.20.000364

Abstract

We present a method to generate complete arbitrary spatially variant polarization modulation of a light beam by means of a parallel aligned nematic liquid crystal spatial light modulator (SLM). We first analyze the polarization modulation properties in a transmission mode. We encode diffraction gratings onto the SLM and show how to achieve partial polarization control of the zero order transmitted light. We then extend the technique to a double modulation scheme, which is implemented using a single SLM divided in two areas in a reflective configuration. The polarization states of the transmitted beam from the first pass through the first area are rotated using two passes through a quarter wave plate. The beam then passes through the second area of the SLM where additional polarization information can be encoded. By combining previously reported techniques, we can achieve complete amplitude, phase and polarization control for the diffracted light that allows the creation of arbitrary diffractive optical elements including polarization control. Theoretical analysis based on the Jones matrix formalism, as well as excellent experimental results are presented.

Highlights

The generation of two dimensional polarization distributions and polarizing diffractive elements is interesting for many applications including polarization imaging [1], data encoding, and polarization multiplexing [2]
Some other approaches for spatial polarization control have been reported that obtain different polarization states on different diffraction orders [5], or that use a split screen configuration on a spatial light modulator (SLM) so different actuation can be performed onto two different polarization components
We have shown the possibility to achieve total spatial polarization control with a diffractive optical system based on a single parallel aligned liquid crystal display

Summary

Introduction

The generation of two dimensional polarization distributions and polarizing diffractive elements is interesting for many applications including polarization imaging [1], data encoding, and polarization multiplexing [2]. Different methods to generate light beams with spatially structured polarization have been theoretically proposed and experimentally probed, including sub-wavelength grating structures [3] and liquid crystal spatial light modulators (LC-SLM) [4]. The latter are interesting because they have the advantage of providing programmable elements. The screen of the display was again divided in two halves, and a half-wave plate had to be placed in the beam reflected in only one half of the screen In this work it was demonstrated how the addition of a phase bias in one half of the screen with respect to the other allows control of the polarization state of the generated traps.

Single modulation theory and experimental results

Double modulation theory and experimental results

Phase only polarization selective multiplexed computer generated holograms

Computer generated holograms reconstruction with polarization control

Fully complex polarization computer generated holograms

Conclusions