title: Enhanced Nonlinear Refractive Index in ε-Near-Zero Materials.
abstract: New propagation regimes for light arise from the ability to tune the dielectric permittivity to extremely low values. Here, we demonstrate a universal approach based on the low linear permittivity values attained in the ε-near-zero (ENZ) regime for enhancing the nonlinear refractive index, which enables remarkable light-induced changes of the material properties. Experiments performed on Al-doped ZnO (AZO) thin films show a sixfold increase of the Kerr nonlinear refractive index (n_{2}) at the ENZ wavelength, located in the 1300 nm region. This in turn leads to ultrafast light-induced refractive index changes of the order of unity, thus representing a new paradigm for nonlinear optics.
authors.affiliation: Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.
authors.forename: L
authors.initials: L
authors.lastname: Caspani
authors.affiliation: Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.
authors.forename: R P M
authors.initials: RP
authors.lastname: Kaipurath
authors.affiliation: Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.|School of Engineering, University of Glasgow, Glasgow G12 8LT, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Clerici
authors.affiliation: Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Ferrera
authors.affiliation: Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.
authors.forename: T
authors.initials: T
authors.lastname: Roger
authors.affiliation: School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, 1205 West State Street, West Lafayette, Indiana 47907-2057, USA.
authors.forename: J
authors.initials: J
authors.lastname: Kim
authors.affiliation: School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, 1205 West State Street, West Lafayette, Indiana 47907-2057, USA.
authors.forename: N
authors.initials: N
authors.lastname: Kinsey
authors.affiliation: SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Pietrzyk
authors.affiliation: SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Di Falco
authors.affiliation: School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, 1205 West State Street, West Lafayette, Indiana 47907-2057, USA.
authors.forename: V M
authors.initials: VM
authors.lastname: Shalaev
authors.affiliation: School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, 1205 West State Street, West Lafayette, Indiana 47907-2057, USA.
authors.forename: A
authors.initials: A
authors.lastname: Boltasseva
authors.affiliation: Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.
authors.forename: D
authors.initials: D
authors.lastname: Faccio