PT Journal AU Kaiser, T Falkner, M Qi, J Klein, A Steinert, M Menzel, C Rockstuhl, C Pertsch, T TI Characterization of a circular optical nanoantenna by nonlinear photoemission electron microscopy SO Applied Physics B: Lasers and Optics PY 2016 BP 53 VL 122 IS 3 DI 10.1007/s00340-015-6312-9 LA english ER