Gravitational waves on the optical bench

Gravitational waves dynamically modulate the local refractive index of a manifold, whence emerges a moving scaffold that facilitates interactions with lightwaves in relative motion. Conservation of energy and momentum mandates the appearance of sidebands in the spectrum of forward-propagating subluminal light-an effect that is intrinsically directional yet imposes no coherence requirements on the interacting fields. Its kinship with synthetic traveling-wave modulations engineered in meta-optics suggests that such index perturbations could emulate spacetime ripples. In this Letter, we propose a fully covariant, all-optical analog framework for mimicking Brillouin-like forward scattering of light in a plasma by spacetime distortions in laboratory settings.