Modal expansion of optical far-field quantities using quasinormal modes Felix Binkowski, Fridtjof Betz, Rémi Colom, Martin Hammerschmidt, Lin Zschiedrich and Sven Burger EPJ Web Conf., 238 (2020) 05007 Published online: 20 August 2020 DOI: 10.1051/epjconf/202023805007