Friedrich-Alexander-Universität Erlangen-Nürnberg

Wireless communication between nano-antennas

Wireless communication between nano-antennas

Wireless transfer of electromagnetic radiation requires antennas with well-designed directivity and high efficiency. In optics, those antennas offer particularly interesting applications in the intermediate domain between the far- and near- field ; integrating wireless transfer channels with highly confined plasmonic circuitry can significantly decrease losses, thus avoiding the major disadvantage of nanoplasmonics . Our method allows for the probing of nano-structures which were previously only accessible by Near-field Scanning Optical Microscopy (NSOM).

Respective structures are investigated theoretically (see Fig. 1) and experimentally (see Fig. 2a) by etching into a silver film on a silica substrate using a focused ion beam machine. To probe the structure we excite a mode of a plasmonic gap waveguide by a linearly polarized laser beam (λ=1.55µm) focused onto the optical antenna (see Fig. 2, A in). A  gap waveguide transfers the energy to antenna B which is resonantly coupled to another antenna (C). C feeds a second, but bent waveguide, which turns the polarization by 90° and emits at its end D (see Fig. 2b). By using a polarizer in front of the observing IR CCD camera, the scattering from the bent waveguide and D becomes visible with significantly increased signal-to-noise ratio (see Fig. 2b, D, out).

Since the coupling efficiency between antennas B and C depends on the distance like 1/d2, wireless connections between two ports can enormously reduce losses compared to the intrinsic losses of gap waveguides, causing an exponential decay.

Collaboration with Jing Wen, Arian Kriesch IOIP Uni Erlangen/ MPL.

Fig. 1: FDTD simulation for investigating the coupling between two optical antennas. The mode source is placed in the waveguide at x=0.4µm launching a SPP mode traveling to antenna B acting as an emitter. The radiation is collected by antenna C. Intensity plot in log10-scale.
Fig. 2: a SEM image of a structure for investigating coupling between two optical antennas. A highly focused laser beam is efficiently coupled into antenna A. A gap SPP waveguide delivers the wave to antenna B, which couples to antenna C (see inset). b Spatial distribution of the light emitted in reflection (150x optical magnification), acquired with an IR CCD. Light with horizontal polarization is coupled into antenna A (in). The emission from D (out) is polarized parallel to a polarizer in front of the CCD. This emission shows qualitatively the operation of the wireless interconnect.



  1. Wen, J., et al. “Excitation of plasmonic gap waveguides by anoantennas”, Opt. Express 17, 5925-5932 (2009)
  2. Wen, J., et al. “Experimental cross-polarization detection of coupling far-field light to highly confined plasmonic gap modes via nanoantennas”, APL 98, 101109 (2011)
  3. Ploss, D., Kriesch, A., Wen, J., Peschel, U. (2011), Low loss wireless interconnects in plasmonic nanocircuitry. CLEO/ Europe Conference. Optical Society of America. Retrieved from:
  4. Alù, A., et al. “Wireless at the Nanoscale: Optical Interconnects using Matched Nanoantennas”, Phys.Rev.Lett. 104, 213902 (2010)




SAOT provides an interdisciplinary research and education program of excellence within a broad international network of distinguished experts to promote innovation and leadership in the areas

Optical Metrology
Optical Material Processing
Optics in Medicine
Optics in Communication and Information Technology
Optical Materials and Systems
and Computational Optics.