Detecting gravitomagnetism with rotation of polarization by a gravitational lens

Abstract

We discuss the effects of an isolated gravitational lens on the rotation of the plane of polarization of linearly polarized light rays, so-called gravitational Faraday rotation, in metric theories of gravity. By applying the thin-lens approximation, we derive simple expressions for extended, rotating astrophysical systems deflecting electromagnetic radiation from background sources. Higher-order corrections and the case of a Kerr black hole are also considered to show how the rotation of polarization is a purely gravitomagnetic effect. Prospects for future detection of gravitational Faraday rotation are examined.