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O: Fachverband Oberflächenphysik

O 31: Nano-optics of metallic and semiconducting nanostructures (theory)

O 31.2: Vortrag

Mittwoch, 25. März 2009, 10:45–11:00, SCH A216

Impedance matching and emission properties of optical antennas in a nanophotonic circuit — Jer-Shing Huang, •Thorsten Feichtner, Paolo Biagioni, and Bert Hecht — Nano-Optics & Biophotonics group, Department of Experimental Physics 5, University of Würzburg, Germany

An experimentally realizable prototype nanophotonic circuit, consisting of a receiving and an emitting nano antenna connected by a two-wire optical transmission line is studied using finite-difference time- and frequency-domain simulations. It is pointed out, that nanoantennas can efficiently convert propagating photons into plasmonic excitations of a transmission line, whose effective wavelength is determined with both a mode solver and a reflection coefficient analysis. The coupling between the nanophotonic circuit elements is optimized applying impedance matching concepts in analogy to radio frequency technology. It will be shown that the degree of impedance matching, and in particular the impedance of the transmitting nano antenna, can be inferred from the standing wave pattern on the transmission line. We demonstrate the possibility of matching the nano antenna impedance to the transmission line characteristic impedance by variations of the antenna length and width realizable by modern microfabrication techniques. The radiation efficiency of the transmitting antenna also depends on its geometry but is independent of the degree of impedance matching. Our systems approach to nanophotonics provides the basis for realizing general nanophotonic circuits and a large variety of derived novel devices.