The basis for quantum-optical application are suitable sources for quantum light. Our research is concentrated on sources for quantum states of light containing exactly two photons, the so-called photon pairs. Photon pairs can be generated using parametric nonlinear processes, where one or two pump laser photons are spontaneously transformed into an entangled photon pair. Such spontaneous nonlinear conversion processes, like spontaneous down conversion or spontaneous four-wave mixing, are governed by the same rules as classical parametric nonlinear processes. Hence, the investigation of classical parametric processes as e.g. second-harmonic generation is an important part of our work.

Micro- and nano-structured optical elements allow for control of the spatial and spectral dispersion of optical fields. Hence, they are ideal to control classical and spontaeous nonlinear conversion processes, which depend on the field overlap and the propagation constants of the interacting modes. We aim to theoretically describe such processes in structured environments, design and rigorously simulate structures to allow for experimental observation and finally characterize manufactured samples in the lab. Among the investigated structures are coupled and nanostructured waveguides, resonant nanoantennas, and atomically thin membranes.

Array of coupled waveguides for photon-pair generation.
  • F. Löchner, A. Fedotova, S. Liu, G. Keeler, G. Peake, S. Saravi, M. Shcherbakov, S. Burger, A. Fedyanin, I. Brener, T. Pertsch, F. Setzpfandt, and I. Staude, "Polarization-Dependent Second Harmonic Diffraction from Resonant GaAs Metasurfaces," ACS Photonics 5, 1786 (2018)
  • S. Saravi, T. Pertsch, and F. Setzpfandt, "Generation of Counterpropagating Path-Entangled Photon Pairs in a Single Periodic Waveguide," Phys. Rev. Lett. 18, 183603 (2017)
  • F. Setzpfandt,  A. S. Solntsev, J. Titchener, C. W. Wu, C. Xiong, R. Schiek, T. Pertsch, D. N. Neshev, and A. A. Sukhorukov, "Tunable generation of entangled photons in a nonlinear directional coupler," Laser & Photonics Review 10, 131 (2016)
  • R. Geiss, S. Saravi, A. Sergeyev, S. Diziain, F. Setzpfandt, F. Schrempel, R. Grange, E.-B. Kley, A. Tünnermann, and T. Pertsch, "Fabrication of nanoscale lithium niobate waveguides for second-harmonic generation," Opt. Lett. 40, 2715 (2015)
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