Chiroptical effect induced by gravitational waves

TL;DR

This paper introduces a novel gravitational analog of the chiroptical effect, showing how gravitational waves can reverse photon chirality via angular momentum exchange, offering new ways to probe gravity and early universe physics.

Contribution

It is the first to propose and analyze the gravitational chiroptical effect, establishing the theoretical framework for photon-GW angular momentum exchange based on field spin properties.

Findings

Gravitational waves can induce photon chirality reversal.

Selection rules depend on the spin-2 nature of GWs.

The effect can probe chiral structures of GWs and test gravity theories.

Abstract

We propose the gravitational analog of the chiroptical effect for the first time, demonstrating that gravitational waves (GWs) can induce a reversal of photon chirality through the exchange of angular momentum, namely the spin-2-gravitation chiroptical effect. By analyzing the interaction between photon spin angular momentum (SAM) and GWs, we derive the selection rules governing this exchange, which are strictly dictated by the spin-1 and spin-2 nature of the electromagnetic and gravitational fields, respectively. We find that the gravitational chiroptical effect reflects the local nature of SAM which prevents the accumulation of gravitational perturbations over spatial phase windings, and offers a theoretically rigorous tool to probe the chiral structure of GWs. This mechanism provides a novel observational pathway to constrain modified gravity theories, measure the asymmetric properties of compact binaries, and explore parity-violating physics in the early universe.