Optical nanoantennas tailor the transmission and reception of optical signals. Owing to their capacity to control the direction and angular distribution of optical radiation over a broad spectral range, nanoantennas are promising components for optical communication in nanocircuits. Here we measure wireless optical power transfer between plasmonic nanoantennas in the far-field and demonstrate changeable signal routing to different nanoscopic receivers via beamsteering. We image the radiation pattern of single-optical nanoantennas using a photoluminescence technique, which allows mapping of the unperturbed intensity distribution around plasmonic structures. We quantify the distance dependence of the power transmission between transmitter and receiver by deterministically positioning nanoscopic fluorescent receivers around the transmitting nanoantenna. By adjusting the wavefront of the optical field incident on the transmitter, we achieve directional control of the transmitted radiation over a broad range of 29°. This enables wireless power transfer from one transmitter to different receivers.

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We give a general introduction into polarized imaging and report on a Jones-pupil approach for a complete evaluation of the resulting optical performance. The Jones pupil assigns a Jones matrix to each point of the exit pupil describing the impact of both the global phase and the polarization on imaging. While we can learn already a lot about the optical system by taking a close look at the Jones pupil -and starting imaging simulations from it -a quantitative assessment is necessary for a complete evaluation of imaging. To do this, we generalize the concept of scalar Zernike aberrations to Jones-Zernike aberrations by expansion of the Jones pupil into vector polynomials. The resulting method is nonparaxial, i.e. the effect of the polarization dependent contrast loss for high numerical apertures is included. The aberrations of the Jones-matrix pupil are a suitable tool to identify the main drivers determining the polarization performance. Furthermore, they enable us to compare the polarized and the unpolarized performance of the such characterized lithographic system.

In radiofrequency antenna engineering, the array factor made long-distance communication with steerable transmission and receiving possible. At optical frequencies, low-loss signal transmission via free space by using nanoantennas is still in its infancy. Here, we suggest applying the array factor to the optical frequency regime by shaping the radiation pattern of plasmonic metasurfaces featuring nanoantenna arrays. We arrange dipolar gold nanoantennas operating at 785 nm wavelength in wavelength-sized arrays and control the phase that drives the antenna elements. We obtain collimated and unidirectional radiation from this metasurface upon illumination with circularly polarized light, which is not prone to major losses as in common plasmonic waveguide structures. We furthermore demonstrate switching the unidirectional emission to opposite directions with additional beamsteering by modifying the array factor. Our experiment corroborates the evidence for spin–orbit coupling between the helicity of light and suitably designed plasmonic metasurfaces, which can exhibit the spin-Hall effect for light.