Spectral measurements of THz radiation emitted from intrinsic Josephson junction stacks V.P. Koshelets, N.V. Kinev, A.B. Ermakov, F. Rudau, R. Wieland, D. Koelle, R. Kleiner and H.B. Wang EPJ Web Conf., 195 (2018) 05013 Published online: 23 November 2018 DOI: 10.1051/epjconf/201819505013