title: Observation of Bloch oscillations in complex PT-symmetric photonic lattices.
abstract: Light propagation in periodic environments is often associated with a number of interesting and potentially useful processes. If a crystalline optical potential is also linearly ramped, light can undergo periodic Bloch oscillations, a direct outcome of localized Wannier-Stark states and their equidistant eigenvalue spectrum. Even though these effects have been extensively explored in conservative settings, this is by no means the case in non-Hermitian photonic lattices encompassing both amplification and attenuation. Quite recently, Bloch oscillations have been predicted in parity-time-symmetric structures involving gain and loss in a balanced fashion. While in a complex bulk medium, one intuitively expects that light will typically follow the path of highest amplification, in a periodic system this behavior can be substantially altered by the underlying band structure. Here, we report the first experimental observation of Bloch oscillations in parity-time-symmetric mesh lattices. We show that these revivals exhibit unusual properties like secondary emissions and resonant restoration of PT symmetry. In addition, we present a versatile method for reconstructing the real and imaginary components of the band structure by directly monitoring the light evolution during a cycle of these oscillations.
authors.affiliation: Institute of Optics, Information and Photonics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstraße 7/B2, 91058 Erlangen, Germany.|Erlangen Graduate School in Advanced Optical Technologies (SAOT), 91058 Erlangen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Wimmer
authors.affiliation: CREOL, College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816-2700, USA.
authors.forename: Mohammed-Ali
authors.initials: MA
authors.lastname: Miri
authors.affiliation: CREOL, College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816-2700, USA.
authors.forename: Demetrios
authors.initials: D
authors.lastname: Christodoulides
authors.affiliation: Institute of Solid State Theory and Optics, Friedrich Schiller University Jena, Max-Wien-Platz 1, 07743 Jena.
authors.forename: Ulf
authors.initials: U
authors.lastname: Peschel