We report an experimental technique for determining phase-resolved radiation patterns of single nanoantennas by phase-retrieval defocused imaging. A key property of nanoantennas is their ability to imprint spatial coherence, for instance, on fluorescent sources. Yet, measuring emitted wavefronts in absence of a reference field is difficult. We realize a defocused back focal plane microscope to measure phase even for partially temporally coherent light and benchmark the method using plasmonic bullseye antenna scattering. We outline the limitations of defocused imaging which are set by spectral bandwidth and antenna mode structure. This work is a first step to resolve wavefronts from fluorescence controlled by nanoantennas.

Atomic and Molecular Physics, and Optics
OSA
European Union Horizon 2020 , NWO
doi.org/10.1364/oe.410344
Opt. Express
Resonant Nanophotonics

Schilder, N.J, Wolterink, T.A.W, Mennes, C, Röhrich, R, & Koenderink, A.F. (2020). Phase-retrieval Fourier microscopy of partially temporally coherent nanoantenna radiation patterns. Opt. Express, 28(25), 37844–37859. doi:10.1364/oe.410344