CyI Colloquium: Coherent phenomena in light absorption by metallic nanostructures

Dates: 
7 January, 2010 - 18:00
Speaker(s): 
Prof. Vassilios Yannopapas, Department of Materials Science, University of Patras, Greece
Venue: 
The Cyprus Institute, Guy Ourisson Building, Athalassa Campus (Higher Technical Institute - HTI, grounds)
Abstract

Nanostructured metals are known to be very good absorbers of visible light since they allow light to penetrate within the structure. Light absorption and emission is traditionally considered as an incoherent phenomenon due to the stochastic nature of the processes involved in absorption/ emission. However, very close to the material surfaces and in the near-field limit of electromagnetic radiation, light absorption can be affected by the state of coherence of absorbed/ emitted light as well as by the local density of states of the photon field. In this colloquium, we will examine specific examples where light absorption/ emission are essentially coherent processes. First we will examine the case of a two-dimensional lattice of metallic nanoparticles on top of a guiding substrate. If the substrate supports guided modes which fall within the surface-plasmon absorption band of the lattice of nanoparticles then one can quench light absorption via a mechanism which resembles electromagnetically-induced transparency in atomic gases [1]. Alternatively, the substrate can make metal absorb light in spectral regions well above the surface-plasmon band where metal is essentially transparent [2,3]. Secondly, we will examine the degree of coherence and polarization of the thermal (blackbody) radiation emitted by a single as well as arrays of metallic nanomitters. In particular, very close to the metallic surface and around the surface-plasmon frequency of a metallic nanoparticle, thermal radiation is both coherent and polarized [4]. Moreover, in the far-field, thermal radiation can also be highly directive with an emission spectrum resembling that of a conventional antenna [5].

References
[1] V. Yannopapas, E. Paspalakis, and N. V. Vitanov, Phys. Rev. B 80, 035104 (2009).
[2] V. Yannopapas and N. Stefanou, Phys. Rev. B 69, 012408 (2004).
[3] G. Gantzounis, N. Stefanou and V. Yannopapas, J. Phys.: Condens. Matter 17, 1791 (2005).
[4] V. Yannopapas and N. V. Vitanov, Phys. Rev. B 80, 035410 (2009).
[5] V. Yannopapas and N. V. Vitanov, Phys. Rev. Lett. 99, 053901 (2007).

For more information contact Dr. Emmanouil Lioudakis email m [dot] lioudakis [at] cyi [dot] ac [dot] cy or tel. +357 22208600