Fast-Light in a Photorefractive Crystal for Gravitational Wave Detection

TL;DR

This paper demonstrates superluminal light propagation in a photorefractive crystal using a gain doublet, with potential applications in enhancing gravitational wave detectors by exploiting anomalous dispersion.

Contribution

It introduces a novel method to achieve superluminal light in a photorefractive crystal via a gain doublet, with implications for improving gravitational wave detection sensitivity.

Findings

Achieved 0.28 sec time advance for a 2Hz gain separation

Demonstrated anomalous dispersion profile in the crystal

Proposed application in enhancing LIGO sensitivity-bandwidth

Abstract

We demonstrate superluminal light propagation using two frequency multiplexed pump beams to produce a gain doublet in a photorefractive crystal of Ce:BaTiO3. The two gain lines are obtained by two-wave mixing between a probe field and two individual pump fields. The angular frequencies of the pumps are symmetrically tuned from the frequency of the probe. The frequency difference between the pumps corresponds to the separation of the two gain lines; as it increases, the crystal gradually converts from normal dispersion without detuning to an anomalously dispersive medium. The time advance is measured as 0.28 sec for a pulse propagating through a medium with a 2Hz gain separation, compared to the same pulse propagating through empty space. We also demonstrate directly anomalous dispersion profile using a modfied experimental configuration. Finally, we discuss how anomalous dispersion produced this way in a faster photorefractive crystal (such as SPS: Sn2P2S6) could be employed to enhance the sensitivity-bandwidth product of a LIGO type gravitational wave detector augmented by a White Light Cavity.