Wednesday, November 30, 2011

Antennas for light + ionics at the nanoscale

A (revised) particularly excellent review article was posted on the arxiv the other day, about metal nanostructures as antennas for light. This seems to be an extremely complete and at the same time reasonably pedagogical treatment of the subject. While in some sense there are no shocking surprises (the basic physics underlying all of this is, after all, Maxwell's equations with complicated boundary conditions and dielectric functions for the metal), there are some great ideas and motifs: the importance of the optical "near field"; the emergence of plasmons, the collective modes of the electrons, which are relevant at the nanoscale but not in macroscopic antennas for, e.g., radio frequencies; the use of such antennas in real quantum optics applications. Great stuff.

I also feel the need for a little bit of shameless self-promotion. My colleague and I have an article appearing in this month's MRS Bulletin, talking about the importance of ion motion and electrochemistry in nanoscale structures. (Sorry about not having a version on the arxiv at this time. Email me if you'd like a copy.) This article was prompted in part by a growing realization among a number of researchers that the consequences of the motion of ions (often neglected at first glance!) are apparent in a number of nanoscale systems. Working at the nanoscale, it's possible to establish very large electric fields and concentration/chemical potential gradients that can drive diffusion. At the same time, there are large accessible surface areas, and inherently small system dimensions mean that diffusion over physically relevant distances is easier than in macroscale materials. While ionic motion can be an annoyance or an unintended complication, there are likely situations where it can be embraced and engineered for useful applications.

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