Reducing the free-space group velocity of single photons by transverse structuring
Journal article published in 2015 by
Daniel Giovannini,
Jacquiline Romero,
Vaclav Potoček,
Gergely Ferenczi,
Fiona Speirits,
Stephen M. Barnett,
Daniele Faccio 
,
Miles J. Padgett
,
Miles J. Padgett
Abstract
The group velocity of light in free space is decreased by controlling the transverse spatial structure of the beam. We present experimental results in the single-photon regime, supported by a simple geometric argument and a full theoretical treatment.