Rotation of polarization in the gravitational field of a laser beam - Faraday effect and optical activity

Understand

We investigate the rotation of the polarization of a light ray propagating in the gravitational field of a circularly polarized laser beam.

• The rotation consists of a reciprocal part due to gravitational optical activity, and a non-reciprocal part due to the gravitational Faraday effect.
• We discuss how to distinguish the two effects: Letting light propagate back and forth between two mirrors, the rotation due to gravitational optical activity cancels while the rotation due to the gravitational Faraday effect accumulates.
• In contrast, the rotation due to both effects accumulates in a ring cavity and a situation can be created in which gravitational optical activity dominates.