Gold, Copper, Silver and Aluminium Nanoantennas
for Enhancing Spontaneous Emission
Ahmad Mohammadi1, Vahid Sandoghdar2 and Mario Agio2
1. Persian Gulf University, Department of Physics, 75195 Bushehr, Iran
2. ETH Zurich, Laboratory of Physical Chemistry, 8093 Zurich, Switzerland
mario.agio@phys.chem.ethz.ch
Controlling the spontaneous emission of quantum emitters with a nanoantenna has recently attracted great attention [1].
Nanoantennas enable the study of fundamental physical processes that govern light-matter interaction at the nanoscale
and hold promise for the realization of smaller and more efficient light-emitting devices. At a first sight, nanoantennas
might be conceived as a downscaled version of conventional antennas operating at radio and microwave frequencies.
However, their electromagnetic resonance is not only determined by the geometry and the surrounding medium, but
also by the optical constants of the material they are made of. A comprehensive analysis, including the effect of
material properties, has been indeed carried out a few decades ago in the context of surface-enhanced Raman scattering,
where only the field enhancement and the resonance wavelength matter [2]. A quantitative treatment of the
modification of spontaneous emission and fluorescence also requires a careful consideration of the antenna quantum
efficiency, which is strongly influenced by the material properties of the nanoantenna [3].
Figure 1 Purcell factor (a) and quantum efficiency (b) of an emitter coupled to nanoantennas made of copper. The inset
in (b) shows the nanoantenna geometry, the emitter position and orientation. The distance between the two spheroids
and the other important parameters are given in the legend in (a).
In this work, we investigate nanoantennas as a function of both geometrical and material parameters to identify and
compare the various effects that determine the main features [4,5]. For instance, as presented in Fig. 1, we demonstrate
that materials like copper can be interesting for the realization of nanoantennas, providing Purcell factors as high as 400
and quantum efficiencies close to 70% at the relatively large emitter-particle separation of 10 nm.
References
[1] J.-J. Greffet, Science 308, 1561 (2005).
[2] E.J. Zeman, and G.C. Schatz, J. Phys. Chem. 91, 634 (1987).
[3] L. Rogobete, F. Kaminski, M. Agio, and V. Sandoghdar, Opt. Lett. 32, 1623 (2007).
[4] A. Mohammadi, V. Sandoghdar, and M. Agio, J. Comput. Theor. Nanosci. 6, 2024 (2009).
[5] A. Mohammadi, V. Sandoghdar, and M. Agio, New J. Phys. 10, 105015 (2008).