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Coupling light waves to gravitational waves

Stefanos Fr. Koufidis ^* and Martin W. McCall

Blackett Laboratory, Department of Physics, Imperial College of Science, Technology and Medicine, Prince Consort Road, London SW7 2AZ, United Kingdom

^*Contact author: steven.koufidis20@imperial.ac.uk

Phys. Rev. D 112, 104033 – Published 12 November, 2025

DOI: https://doi.org/10.1103/g96h-6dg6

Abstract

We demonstrate analytically that gravitational waves, upon interacting with copropagating electromagnetic radiation in a plasma, induce distinctive sidebands on the modulated light, thereby providing a detectable signature of their presence. Employing a fully covariant coupled-wave framework, we envision gravitational waves as phase-insensitive luminal moving gratings and derive explicit phase-matching conditions that articulate such an interaction while conserving both energy and momentum. Beyond preserving the directional signature of gravitational waves, the coupling mechanism imposes no coherence requirements on the photon-by-graviton scattering, hence enabling possibilities for exploiting cosmic microwave background radiation. Although detection at low frequencies is constrained by the requirement of long interaction lengths, advances in laser technology are poised to enable high-frequency gravitational wave detection, potentially unveiling insights into the primordial spacetime ripples that have been traversing the cosmos since the inflationary epoch.

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Phys. Rev. D 112, 104033– Published 12 November, 2025

Vol. 112, Iss. 10 — 15 November 2025

Received 5 March 2025
Accepted 21 October 2025

DOI: https://doi.org/10.1103/g96h-6dg6

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

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Coupling light waves to gravitational waves

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