Cancellation of simple optical anisotropies without use of a Faraday mirror

TL;DR

This paper demonstrates a method to cancel simple optical anisotropies using a specific optical setup with quarterwave plates and a mirror, enabling a liquid crystal device to act as a polarization-independent phase modulator.

Contribution

It introduces a novel optical configuration that cancels anisotropies without a Faraday mirror, allowing for polarization-insensitive phase modulation with liquid crystals.

Findings

The derived Jones matrix describes double passage through reciprocal media.

The setup effectively makes an anisotropic medium behave isotropically.

A liquid crystal device is demonstrated as a polarization-independent phase modulator.

Abstract

We first derive the round-trip Jones matrix for double passage through a reciprocal optical medium by means of reflection off a plane mirror that could be optically anisotropic. We then show that if a medium with only linear birefringence and linear dichroism is placed between a pair of orthogonal quarterwave plates with principal axes at 45 deg to that of the medium and the sandwich is placed in front of an isotropic mirror it behaves, under double passage, like an isotropic medium. We describe a simple liquid crystal device that behaves, in reflection, as an isotropic medium whose refractive index can be varied by application of an electric field, thus acting as a phase only modulator for light in any polarization state.