title: Focusing-to-defocusing crossover in nonlinear periodic structures.
abstract: We demonstrate experimentally a transition from nonlinear beam trapping to defocusing in a two-dimensional periodic photonic structures by varying the modulation depth of the lattice. The observed effect illustrates the fundamental crossover from discrete to cw transport mechanisms. At the threshold modulation, the output beam is highly sensitive to refractive index and power variations, which can be potentially applied for high-sensitivity refractive index or temperature sensing.
authors.affiliation: Nonlinear Physics Centre, Research School of Physics and Engineering, Australian National University, 0200 Australian Capital Territory, Canberra, Australia. fhb124@rsphysse.anu.edu.au
authors.forename: Francis H
authors.initials: FH
authors.lastname: Bennet
authors.forename: Inés A
authors.initials: IA
authors.lastname: Amuli
authors.forename: Andrey A
authors.initials: AA
authors.lastname: Sukhorukov
authors.forename: Wieslaw
authors.initials: W
authors.lastname: Krolikowski
authors.forename: Dragomir N
authors.initials: DN
authors.lastname: Neshev
authors.forename: Yuri S
authors.initials: YS
authors.lastname: Kivshar