Experimental quantum cosmology in time-dependent optical media

Westerberg, N., Cacciatori, S., Belgiorno, F., Piazza, F. D. and Faccio, D. (2014) Experimental quantum cosmology in time-dependent optical media. New Journal of Physics, 16(7), 075003. (doi:10.1088/1367-2630/16/7/075003)

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Abstract

It is possible to construct artificial spacetime geometries for light by using intense laser pulses that modify the spatiotemporal properties of an optical medium. Here we theoretically investigate experimental possibilities for studying spacetime metrics of the form ${\rm d}{{s}^{2}}={{c}^{2}}{\rm d}{{t}^{2}}-\eta {{\left( t \right)}^{2}}{\rm d}{{x}^{2}}$. By tailoring the laser pulse shape and medium properties, it is possible to create a refractive index variation $n=n\left( t \right)$ that can be identified with $\eta \left( t \right)$. Starting from a perturbative solution to a generalized Hopfield model for the medium described by an $n=n\left( t \right)$, we provide estimates for the number of photons generated by the time-dependent spacetime. The simplest example is that of a uniformly varying $\eta \left( t \right)$ that therefore describes the Robertson–Walker metric, i.e. a cosmological expansion. The number of photon pairs generated in experimentally feasible conditions appears to be extremely small. However, large photon production can be obtained by periodically modulating the medium and thus resorting to a resonant enhancement similar to that observed in the dynamical Casimir effect. Curiously, the spacetime metric in this case closely resembles that of a gravitational wave. Motivated by this analogy, we show that a periodic gravitational wave can indeed act as an amplifier for photons. The emission for an actual gravitational wave will be very weak but should be readily observable in the laboratory analogue.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Faccio, Professor Daniele
Authors: Westerberg, N., Cacciatori, S., Belgiorno, F., Piazza, F. D., and Faccio, D.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:New Journal of Physics
Publisher:IOP Publishing
ISSN:1367-2630
ISSN (Online):1367-2630
Copyright Holders:Copyright © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft
First Published:First published in New Journal of Physics 16(7):075003
Publisher Policy:Reproduced under a Creative Commons License

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