A simple inverter for polarization transformations

TL;DR

This paper presents a simple optical device using birefringent and halfwave plates to invert polarization transformations, enabling switching of optical properties without moving parts.

Contribution

It introduces a novel configuration of birefringent elements and halfwave plates to invert polarization transformations electrically.

Findings

The device can invert the eigenstates and eigenvalues of polarization transformations.

It allows switching the sign of optical activity or rotating polarization by 90 degrees electrically.

No moving parts or additional linear polarizers are needed.

Abstract

It is shown that a transparent birefringent element whose eigenstates are a pair of elliptical polarizations with principalaxes along the x and y axes, sandwiched between a pair of orthogonal halfwave plates with principal axes along directions at 45 deg to the x and y axes, is equivalent to an element with the same eigenstates and eigenvalues but with the fast and the slow eigenstates interchanged. The device thus produces the inverse of the original unitary transformation. A similar result holds for a puredichroic element. With electrically switchable halfwave plates such a device can be used to switch the sign of optical activity or to rotate through 90 deg, without any moving parts, a linear retarder or a linear polarizer.