Spatially structured photons that travel in free space slower than the speed of light

Giovannini, D., Romero, J., Potoček, V., Ferenczi, G., Speirits, F., Barnett, S. , Faccio, D. and Padgett, M. (2015) Spatially structured photons that travel in free space slower than the speed of light. [Data Collection]

Original publication URL: http://dx.doi.org/10.1126/science.aaa3035
Enlighten Publications URI: http://eprints.gla.ac.uk/id/eprint/102869

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That the speed of light in free space is constant is a cornerstone of modern physics. However, light beams have finite transverse size, which leads to a modification
of their wavevectors resulting in a change to their phase and group velocities. We study the group velocity of single photons by measuring a change in their arrival time that results from changing the beam’s transverse spatial structure. Using time-correlated photon pairs we show a reduction of the group velocity of photons in both a Bessel beam and photons in a focused Gaussian beam. In both cases, the delay is several micrometers over a propagation distance of the order of 1 m. Our work highlights that, even in free space, the invariance of the speed of light only applies to plane waves.

College / School: College of Science and Engineering > School of Physics and Astronomy
Date Deposited: 02 Apr 2015 09:28
Enlighten Publications URL: http://eprints.gla.ac.uk/102869/
Funder's Name: Engineering and Physical Sciences Research Council (EPSRC), European Research Council (ERC), Engineering and Physical Sciences Research Council (EPSRC)
URI: http://researchdata.gla.ac.uk/id/eprint/157

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Giovannini, D., Romero, J., Potoček, V., Ferenczi, G., Speirits, F., Barnett, S. , Faccio, D. and Padgett, M. (2015); Spatially structured photons that travel in free space slower than the speed of light

University of Glasgow

DOI: 10.5525/gla.researchdata.157

Retrieved: 2019-09-18