3D Printed Periodic Structures for Subterahertz Sources D. I. Sobolev, M.D. Proyavin, N.Yu. Peskov, V.Yu. Zaslavsky and V.V. Parshin EPJ Web Conf., 195 (2018) 01017 Published online: 23 November 2018 DOI: 10.1051/epjconf/201819501017