The response of laser interferometers to a gravitational wave

TL;DR

This paper demonstrates that laser interferometers detect gravitational waves through frequency modulation sidebands on light, which are equivalent to phase shifts, providing an alternative perspective to the mirror motion explanation.

Contribution

It offers a novel calculation method showing that electromagnetic wave propagation in curved spacetime explains interferometer responses to gravitational waves.

Findings

Frequency modulation sidebands at the GW frequency are produced in the interferometer.

Sidebands are equivalent to phase shifts in the conventional analysis.

The approach links graviton interactions to observable signals.

Abstract

Laser interferometer detectors are now widely used in an attempt to detect gravitational waves (gw). The interaction of the gw with the light circulating in the interferometer is usually explained in terms of the motion of the "free" mirrors that form the interferometer arms. It is however instructive to show that the same result can be obtained by simply calculating the propagation of an electromagnetic plane wave between "free mirrors" in the curved space-time induced by the gw. One finds that the plane wave acquires frequency modulation sidebands at the gw frequency, as would be expected from the absorption and emission of gravitons from and to the gw. Such sidebands are completely equivalent to the time-dependent phase shift imposed on the plane wave, that follows from the conventional calculation.