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Controlling Plasmonic Coupling with Geometry

Dr Nil Rotenberg

FOM Institute AMOLF, Amsterdam, The Netherlands

2:00 pm Friday, 8 February 2013, EN313 Lecture Theatre (EN Building), Hawthorn.

It's been over 100 years since the first observations of a periodic structure coupling light to surface modes of metal film. These modes, which are known as surface plasmon polaritons, can be used to both guide light and enhance local electric fields and consequently can be found in diverse nanophotonic applications ranging from bio-sensing, to quantum optics, or optical signal processing. However, exciting these modes is not straightforward: the reason that they are bound to the metal's surface is that they have a higher momentum than free-space light and hence cannot radiate. For excitation, this momentum mismatch must be overcome. One solution is to use periodic structures, such as gratings, where diffraction provides the necessary momentum and resonantly couples light to the surface plasmon polariton.

In this talk I will address how the geometry of a periodic structure, beyond its periodicity or amplitude can be used to control how this plasmonic coupling occurs. Specifically, I will introduce the concept of a phase that is intrinsic to the coupling process, and which can be tuned with the geometry of the structure, to, for example, turn the plasmonic coupling on or off. I will show that relatively simple structures can act as one-way plasmonic couplers, and explain the underlying physics behind this surprising phenomenon.

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