Scattering in random photonic networks

• Antragsteller: Professor Dr. Ulf Peschel
• Fachliche Zuordnung: Statistische Physik, Nichtlineare Dynamik, Komplexe Systeme, Weiche und fluide Materie, Biologische Physik
• Förderung: Förderung von 2010 bis 2015
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 24367642

• Erstellungsjahr: 2014

Zusammenfassung der Projektergebnisse

The main aim of the project was the investigation of coherent transport and scattering in optical media in the presence of refractive index structures and nonlinearities. As spatial systems turned out to be less stable, more expensive and less technically relevant we shifted our focus to temporal ones, where dynamics is based on the evolution of pulses in optical fibers. In temporal systems transport is usually realized by dispersive spreading of pulses. In addition coupling fiber loops of different length allows pulses to vary the time per round trip by either choosing to pass the long or the short loop. This also results in an effective dispersive spreading of a pulse sequence. In the course of the project we followed both approaches. By exclusively employing equipment originally developed for optical communication we managed to construct technically relevant and easy to handle model systems consisting of fiber loops. We could follow the wave evolution with high precision and over a propagation length, which cannot be reached in spatial systems. Thus we studied the interaction of linear and nonlinear waves with arbitrarily shaped effective potentials which were induced by phase modulators. In addition amplifiers and amplitude modulators allowed tuning gain and loss. As obtained with similar equipment all results of the project may become relevant for the development of fiber lasers and for signal transmission in optical communication systems. In the framework of the project a lot of peer reviewed journal articles as well as conference contributions have been published. Some of our publications resulting from the project have attained considerable attention, even beyond the community, which is usually affected by the activities of the Forschergruppe. In the context of the project we realized for the first time a discrete system in the temporal domain by inscribing a periodic phase modulation onto the field during each round trip through a fiber loop (see Bersch Phys. Rev. Lett. 2012). This phase modulation acted like an effective potential and confines pulses to the potential minima thus effectively discretizing the system. As a result nonlinear effects can be observed at extremly low power levels. We managed to excite a discrete soliton with a peak power of less than 30mW, which was only based on the fast, but extremely weak Kerr nonlinearity of the optical fiber. As gain and loss can easily induced in fiber based systems we further developed our set-up consisting of two coupled fiber loops of different length by realizing also complex valued effective potentials. Thus we could create the first PT-symmetric system with transverse degrees of freedom. Results of respective investigations were published in Nature in August 2012. Due to the inherent periodicity of the wave propagation in the coupled fiber loop set-up respective fields are well characterized by a band structure consisting of two bands with opposite curvature corresponding to positive and negative masses or anomalous and normal group velocity dispersion. Based on the versatility of our set-up we could study for the first time the nonlinear interaction between fields having effective masses of opposite sign. We observed the creation of self-accelerated bound states of light, where a Schrödinger soliton is pushing forward a negative mass wave in front of it, but is simultaneously attracted by this wave.

Projektbezogene Publikationen (Auswahl)

• Photon propagation in a discrete fiber network: an interplay of coherence and losses, Phys. Rev. Lett. 107, 233902 (2011)
  A. Regensburger, C. Bersch, B. Hinrichs, G. Onishchukov, A. Schreiber, C. Silberhorn, and U. Peschel
  
• Optical gap solitons and truncated nonlinear Bloch waves in temporal lattices, Phys. Rev. Lett. 109 , 093903 (2012)
  C. Bersch, G. Onishchukov, and U. Peschel
  
• Optical mesh lattices with PT symmetry, Phys. Rev. A 86, 023807 (2012)
  M.-A. Miri, A. Regensburger, U. Peschel, and D. N. Christodoulides
  
• Parity-time synthetic photonic lattices, Nature 488, 167-171 (2012)
  A. Regensburger, C. Bersch, M.-A. Miri, G. Onishchukov, D.N. Christodoulides, and U. Peschel
  
• Observation of Defect States in PT -Symmetric Optical Lattices, Phys. Rev. Lett. 110, 223902 (2013)
  A. Regensburger, M.-A. Miri, C. Bersch, J. Näger, G. Onishchukov, D. N. Christodoulides, U. Peschel,
  
• Optical diametric drive acceleration through action-reaction symmetry breaking, Nature Physics 9, 780-784 (2013)
  M. Wimmer, A. Regensburger, C. Bersch, M.-A. Miri, S. Batz, G. Onishchukov, D. N. Christodoulides, and U. Peschel