Abstract
We consider a planar optical cavity with one of its in-plane axis aligned with the Earth’s local gravity field. We examine the motion of a wavepacket of light trapped within the cavity spacer under the action of gravity. Using a general relativity framework, we find that the wavepacket initially at rest in terms of its in-plane group velocity, is subject to a non-relativistic free-fall motion of acceleration in the Earth-bound reference frame.
Highlights
INTRODUCTIONThe effect of gravity on propagating electromagnetic waves leads to several fascinating phenomena such as gravitational lensing [1], redshift [2] and time dilation [3]
The effect of gravity on propagating electromagnetic waves leads to several fascinating phenomena such as gravitational lensing [1], redshift [2] and time dilation [3]. These effects are often associated with light propagating freely over macroscopic distances; and yet, they can show up in photonic devices designed for this purpose such as interferometers
We have shown that when a planar or cylindrical optical cavity is oriented adequately in a gravitational field, an analogous of the gravitational redshift phenomenon takes place
Summary
The effect of gravity on propagating electromagnetic waves leads to several fascinating phenomena such as gravitational lensing [1], redshift [2] and time dilation [3]. Let us mention for instance the Sagnac interferometer routinely used nowadays in inertial navigation [4], and the celebrated giant Michelson interferometers used in the LIGO-Virgo collaborations, that detected recently several gravitational wavetrains from black-holes and neutron stars mergers [5, 6, 7] Another class of photonic device is less frequently considered and yet increasingly relevant in this context: that of optical resonators (i.e. Fabry-Perot optical cavities). Photons can be stored nowadays in a confocal superconducting cavity for as long as 0.13 s [13] which, once unfolded, correspond to a free space travel as large as 39000 km Such space and time scales suggest that the field stored in these cavity might be influenced by earth’s gravity in a measurable way. We show that this behaviour can be understood as a manifestation of gravitational redshift in a cavity
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