121 120 Principal Scientist Profiles Ulf Peschel Ulf Peschel Principal Scientist Profiles PROFESSOR OF THEORETICAL PHYSICS AND SOLID STATE OPTICS In 2014, Ulf Peschel became a chairholder at the Institute of Solid State Theory and Optics, where he is currently the Institute’s director. Prof. Peschel is a Senior Fellow of the Optical Society of America and Dean of the Faculty of Physics and Astronomy. ULF PESCHEL RESEARCH AREAS Ulf Peschel has been working in the field of optics for more than 20 years, both theoretically and experiment-ally, with a focus on integrated optics, nanophotonics, nonlinear dynamics and electromagnetic modelling. He theoretically investigates the interaction between light fields and quantum systems on the nanoscale leading to nonlinear optical effects as higher harmonics generation or exciton-polariton condensation in semiconductor nanostructures. He also performs experiments on the field evolution in optical fiber systems, in which discreteness is realized in the temporal domain, and where gain, loss and phase modulation can be tuned to experimentally realize new phenomena as topological protection, parity-time symmetry, entanglement or superfluidity of light. TEACHING FIELDS Prof. Peschel is currently giving lectures in the theoretical physics including the linear and nonlinear aspects of optics and light-matter interaction. RESEARCH METHODS A computer cluster including respective software and licenses is hosted and maintained in Ulf Peschel’s group. The group has vast experience in the numerical solution of various optical problems and uses a lot of standard methods of electromagnetic modeling, including the beam propagation method, finite difference time domain (FDTD) codes and eigenmode solvers. A running fiber loop setup is available for proof-of-principle experiments on linear and nonlinear dynamics in optical systems. RECENT RESEARCH RESULTS Some of Prof. Peschel’s current research activities focus on the time evolution of optical pulses in fiber systems. Together with his group, he for the first time realized a discrete system in the time domain and investigated time discrete temporal solitons [1]. He could demonstrate that the dimensionality of a fiber system can be increased by will thus allowing for the demonstration of genuine two-diemnsional effects in originally one-dimensional settings [2]. He currently studies optical systems with balanced gain and loss, which obey parity-time (PT) symmetry, which allow for sudden phase transitions and unidirectional invisibility [3]. The group observed the first PT-symmetric optical solitons in one [4] and two transverse dimensions [5]. Studies on topological effects resulted in the first experimental measurement of the Berry curvature in an optical system [6]. Prof. Peschel is modelling activities focus on the efficient investigation of exciton-polariton dynamics in resonantly excited semiconductor resonators, in particular on condensation and soliton formation in these structures [7] implementation of codes simulating lightmatter interaction in semiconductor nanostructures based on finite-difference time domain (FDTD) codes coupled with semiconductor Maxwell-Bloch equations [8]. Ulf Peschel is currently the speaker of the cooperative research center SFB 1375 „Nonlinear Optics down to Atomic scales (NOA)“. His research activities focus on the modeling of quantum effects stimulated by strong light fields. OPTICAL DIAMETRIC DRIVES Newton’s third law demands that, for every action, there is an equal and opposite reaction. If for some reason, one of the masses of two mutually attracting particles is negative as m1=-m2, both bodies will indefinitely accelerate in the same direction while keeping a constant distance among themselves (see Figure a). Quite recently, we have reported the first experimental demonstration of this intriguing effect for pulses propagating in a nonlinear optical mesh lattice. Pulses circu- lating in two coupled fiber loops of different lengths (see Figure b) experience a band structure with two bands of opposite curvature or group velocity dispersion (see Figure c). Similar to two particles with opposite masses, pulses from different bands accelerate in the same direction due to the action of nonlinear cross-phase modulation (see Figure d). As a result, a bound state experiencing perpetual acceleration is established, provided that the power in both field distributions is appropriately chosen [Wimmer et al. Nature Phys. 9, 780 (2013); Batz and Peschel, Phys. Rev. Lett. 110, 193901(2013)]. [1] Bersch et al., Phys. Rev. Lett. 109, 093903 (2012). [2] Muniz et al., Scientific Reports 9, 9518 (2019). [3] Regensburger et al., Nature 488, 167 (2012). [4] Wimmer et al., Nature Comm. 7782 (2015). [5] Muniz et al., Phys. Rev. Lett. 123, 253903 (2019) [6] Wimmer et al., Nature Physics 13, 545 (2017). [7] Egorov et al., Phys. Status Solidi B 2019, 1800729 (2019). [8] Buschlinger et al., Phys. Rev. B 91, 045203 (2015). Contact: Phone: + 49 3641 9-47170 Email: ulf.peschel@uni-jena.de
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