Enroute: Electric Field and Current Induced Second Harmonic Generation in Graphene

Mr. Jonas Woeste1, Ms. Nupur Sontakkey2, Mr. David Saleta Reig2, Dr. Michal Swiniarski2, Dr. Klaas-Jan Tielrooij2,3, Dr. Jan-Christoph Deinert4, Dr. Sergey Kovalev5, Dr. Enrico Dietz6, Dr. Hassan A. Hafez7, Dr. Dmitry Turchinovich7, Dr. Nikola Stojanovic6, Prof. Michael Gensch6,1
1Institut für Optik und Atomare Physik, Technische Universität Berlin, Berlin, Germany. 2Catalan Institute of Nanoscience and Nanotechnology (ICN2), BIST and CSIC, Campus UAB, Barcelona, Spain. 3Department of Applied Physics, TU Eindhoven, Eindhoven, Netherlands. 4Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany. 5Fakultät Physik, Technische Universität Dortmund, Dortmund, Germany. 6DLR - Institute of Optical Sensor Systems, Berlin, Germany. 7Fakultät für Physik, Universität Bielefeld, Bielefeld, Germany


Because of its exceptionally high THz nonlinearity, graphene is currently discussed as a technological platform for a variety of THz nonlinear photonic applications ranging from saturable absorbers to THz frequency multipliers. Recently we showed successfully that (i) the nonlinearity of graphene can be controlled over two orders of magnitude by applying moderate gate voltages in the sub-Volt regime and (ii) that a specifically designed grating-graphene meta-material enables further increase in the THz nonlinearity via plasmonic field enhancement. In these previous works, we have focused on studying nonlinearities of odd-orders, since monolayer graphene is a centrosymmetric material, where even-order susceptibilities cancel out. Next step is to investigate if an effective second order nonlinearity (c(2)) can be efficiently generated by applying appropriate in-plane DC electric fields or currents (V or I, see fig. 1 (b), thus breaking the inversion symmetry, such as what has recently been demonstrated and observed in GaAs. We will quantify the achievable magnitude of electric-field induced second-order THz nonlinearity in graphene in order to elucidate its potential for nonlinear photonic applications relying on even-order susceptibilities, such as difference frequency generation. The derived results will directly allow us to evaluate the potential of graphene devices of this type as e.g. efficient mixers in heterodyne spectroscopy applications. Figures 1 (a) and (c) illustrate the introduced PCB design and grating-graphene assembly.