title: Observation of defect states in PT-symmetric optical lattices.
abstract: We provide the first experimental demonstration of defect states in parity-time (PT) symmetric mesh-periodic potentials. Our results indicate that these localized modes can undergo an abrupt phase transition in spite of the fact that they remain localized in a PT-symmetric periodic environment. Even more intriguing is the possibility of observing a linearly growing radiation emission from such defects provided their eigenvalue is associated with an exceptional point that resides within the continuum part of the spectrum. Localized complex modes existing outside the band-gap regions are also reported along with their evolution dynamics.
authors.affiliation: Institute of Optics, Information, and Photonics, SAOT, University of Erlangen-Nuernberg, 91058 Erlangen, Germany.
authors.forename: Alois
authors.initials: A
authors.lastname: Regensburger
authors.forename: Mohammad-Ali
authors.initials: MA
authors.lastname: Miri
authors.forename: Christoph
authors.initials: C
authors.lastname: Bersch
authors.forename: Jakob
authors.initials: J
authors.lastname: Näger
authors.forename: Georgy
authors.initials: G
authors.lastname: Onishchukov
authors.forename: Demetrios N
authors.initials: DN
authors.lastname: Christodoulides
authors.forename: Ulf
authors.initials: U
authors.lastname: Peschel