Emission properties of an oscillating point dipole from a gold Yagi-Uda nanoantenna array

TL;DR

This paper numerically analyzes how a periodic array of gold Yagi-Uda nanoantennas can significantly enhance and direct the emission of an oscillating point dipole, with potential applications in nano-optics.

Contribution

It demonstrates strong near-field enhancement and directional emission of a dipole near a nanoantenna array, highlighting the effects of dipole position, orientation, and frequency.

Findings

Emission can be enhanced by a factor of 100 near the feed element.

The far-field emission pattern is highly directional despite only one director per nanoantenna.

Radiative efficiency is approximately 20%.

Abstract

We investigate numerically the interaction of an oscillating point dipole with a periodic array of optical Yagi-Uda nanoantennas in the weak coupling limit. A very strong near-field enhancement of the dipole emission by the resonant plasmon mode in the feed element is predicted in this structure. It is shown that the enhancement strength depends strongly on the dipole position, the direction of the dipole moment, and the oscillation frequency. The radiative intensity of the point dipole from appropriate places next to one feed element may exceed the radiative intensity of an equivalent dipole in free-space by a factor of hundred. In spite of only one director used in each nanoantenna of the array, the far-field emission pattern is highly directed. The radiative efficiency (the ratio of the radiative to the full emission) appears to be around 20%.