title: Nonlinear optics of fibre event horizons.
abstract: The nonlinear interaction of light in an optical fibre can mimic the physics at an event horizon. This analogue arises when a weak probe wave is unable to pass through an intense soliton, despite propagating at a different velocity. To date, these dynamics have been described in the time domain in terms of a soliton-induced refractive index barrier that modifies the velocity of the probe. Here we complete the physical description of fibre-optic event horizons by presenting a full frequency-domain description in terms of cascaded four-wave mixing between discrete single-frequency fields, and experimentally demonstrate signature frequency shifts using continuous wave lasers. Our description is confirmed by the remarkable agreement with experiments performed in the continuum limit, reached using ultrafast lasers. We anticipate that clarifying the description of fibre event horizons will significantly impact on the description of horizon dynamics and soliton interactions in photonics and other systems.
authors.affiliation: Department of Physics, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Webb
authors.affiliation: Department of Physics, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Miro
authors.initials: M
authors.lastname: Erkintalo
authors.affiliation: 1] Department of Physics, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand [2] Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Yiqing
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Department of Physics, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Neil G R
authors.initials: NG
authors.lastname: Broderick
authors.affiliation: Université de Franche-Comté, Institut FEMTO-ST, CNRS UMR 6174, 25030 Besançon, France.
authors.forename: John M
authors.initials: JM
authors.lastname: Dudley
authors.affiliation: Optics Laboratory, Department of Physics, Tampere University of Technology, PO Box 692, 33720 Tampere, Finland.
authors.forename: Goëry
authors.initials: G
authors.lastname: Genty
authors.affiliation: Department of Physics, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Stuart G
authors.initials: SG
authors.lastname: Murdoch