Light scattering by radiation fields: the optical medium analogy

TL;DR

This paper develops an analogy between radiation fields in general relativity and optical media, analyzing how light scattering occurs in inhomogeneous and anisotropic or isotropic media created by gravitational or electromagnetic waves.

Contribution

It introduces an optical medium analogy for radiation fields in general relativity, comparing light scattering in media generated by gravitational and electromagnetic waves.

Findings

Inhomogeneous and anisotropic medium for gravitational waves

Inhomogeneous and isotropic medium for electromagnetic waves

Differences in light deflection due to medium properties

Abstract

The optical medium analogy of a radiation field generated by either an exact gravitational plane wave or an exact electromagnetic wave in the framework of general relativity is developed. The equivalent medium of the associated background field is inhomogeneous and anisotropic in the former case, whereas it is inhomogeneous but isotropic in the latter. The features of light scattering are investigated by assuming the interaction region to be sandwiched between two flat spacetime regions, where light rays propagate along straight lines. Standard tools of ordinary wave optics are used to study the deflection of photon paths due to the interaction with the radiation fields, allowing for a comparison between the optical properties of the equivalent media associated with the different background fields.