title: Nonlinear diffraction from a virtual beam.
abstract: We observe experimentally a novel type of nonlinear diffraction in the process of two-wave mixing on a nonlinear quadratic grating. We demonstrate that when the nonlinear grating is illuminated simultaneously by two noncollinear beams, a second-harmonic diffraction pattern is generated by a virtual beam propagating along the bisector of the two pump beams. The observed diffraction phenomena is a purely nonlinear effect that has no analogue in linear diffraction.
authors.affiliation: Nonlinear Physics Center and Laser Physics Center, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200, Australia.
authors.forename: Solomon M
authors.initials: SM
authors.lastname: Saltiel
authors.forename: Dragomir N
authors.initials: DN
authors.lastname: Neshev
authors.forename: Wieslaw
authors.initials: W
authors.lastname: Krolikowski
authors.forename: Noa
authors.initials: N
authors.lastname: Voloch-Bloch
authors.forename: Ady
authors.initials: A
authors.lastname: Arie
authors.forename: Ole
authors.initials: O
authors.lastname: Bang
authors.forename: Yuri S
authors.initials: YS
authors.lastname: Kivshar