Spectral interferometric microscopy reveals absorption by individual optical nanoantennas from extinction phase.
Optical antennas transform light from freely propagating waves into highly localized excitations that interact strongly with matter. Unlike their radio frequency counterparts, optical antennas are nanoscopic and high frequency, making amplitude and phase measurements challenging and leaving some information hidden. Here we report a novel spectral interferometric microscopy technique to expose the amplitude and phase response of individual optical antennas across an octave of the visible to near-infrared spectrum. Although it is a far-field technique, we show that knowledge of the extinction phase allows quantitative estimation of nanoantenna absorption, which is a near-field quantity. To verify our method we characterize gold ring-disk dimers exhibiting Fano interference. Our results reveal that Fano interference only cancels a bright mode's scattering, leaving residual extinction dominated by absorption. Spectral interference microscopy has the potential for real-time and single-shot phase and amplitude investigations of isolated quantum and classical antennas with applications across the physical and life sciences.
Department of Physics, The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK.
Sylvain D
SD
Gennaro
Department of Physics, The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK.
Yannick
Y
Sonnefraud
1] INPAC, K. U. Leuven Celestijnenlaan 200 D, Leuven B-3001, Belgium [2] IMEC, Kapeldreef 75, Leuven 3001, Belgium.
Niels
N
Verellen
1] INPAC, K. U. Leuven Celestijnenlaan 200 D, Leuven B-3001, Belgium [2] IMEC, Kapeldreef 75, Leuven 3001, Belgium.
Pol
P
Van Dorpe
INPAC, K. U. Leuven Celestijnenlaan 200 D, Leuven B-3001, Belgium.
Victor V
VV
Moshchalkov
Department of Physics, The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK.
Stefan A
SA
Maier
Department of Physics, The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK.
Rupert F
RF
Oulton
D006046:Gold; D007368:Interferometry / Q000379:methods; D008027:Light; D008857:Microscopy, Interference / Q000379:methods*; D049329:Nanostructures / Q000737:chemistry*; D055095:Optics and Photonics
D006046:Gold