Degenerate Backward wave Optical Parametric Oscillator Patrick Mutter, Andrius Zukauskas, Anne-Lise Viotti, Valdas Pasiskevicius and Carlota Canalias EPJ Web Conf., 243 (2020) 18003 Published online: 15 October 2020 DOI: 10.1051/epjconf/202024318003