Nanoscale optics for data transmission

Researchers from Rice University have gained new insights into nanoscale optics by discovering "a universal relationship between the behavior of light and electrons."

I've already written about plasnomics, this new field which aims to develop optical components and systems similar in size with current integrated circuits (check "A plasmonic revolution for computer chips?"). Now, researchers from Rice University have gained new insights into nanoscale optics by discovering "a universal relationship between the behavior of light and electrons." These new findings could be used to develop nanoscale antennae "that convert light into broadband electrical signals capable of carrying approximately 1 million times more data than existing interconnects." If this looks appealing, don't expect any kind of commercial product in the short term.

Light and electrons both can behave as waves or particles. But the Rice researchers at the Laboratory for Nanophotonics (LANP) have discovered how light-like waves, or plasmons, can interact with nanoparticles of gold or silver.

In recent years there has been intense interest in developing ways to guide and manipulate light at dimensions much smaller than optical wavelengths. Metals like gold and silver have ideal properties to accomplish this task. Special types of light-like waves, called plasmons, can be transmitted along the surfaces of metals in much the same way as light in conventional optical fibers.
When small metallic nanoparticles are positioned on the metal film, they behave like tiny antennae that can transmit or receive light; it is this behavior that has been found to mimic that of electrons. Until now, the coupling of light waves into extended nanoscale structures has been poorly understood.

So how did these researchers set up their experiments?

In the latest research, Halas' graduate student Nyein Lwin placed a tiny sphere of gold -- measuring about 50 nanometers in diameter, within just a few nanometers of a thin gold film. When a light excited a plasmon in the nanosphere, this plasmon was converted into a plasmon wave on the film, for certain specific film thicknesses.

The diagram below shows how looks like a plasmon oscillation for a sphere (Credit: J. Phys. Chem. B, 2003, 107, 668-677). The oscillation frequency is determined by four factors: the density of electrons, the effective electron mass, the shape of the charge distribution, and the size of the charge distribution.

Plasmon oscillation for a sphere

But when will see these nanoscale interconnects carrying approximately 1 million times more data than existing ones or plasnomic components running at frequencies 100,000 times greater than the ones of current microprocessors? It's really too early to tell.

For more information, you should check this page about plasmonics at LANP. And their latest research work has been published online by Nano Letters under the name "Plasmons in the Metallic Nanoparticle-Film System as a Tunable Impurity Problem" (September 14, 2005). It will appear in an upcoming print edition, but here is a link to the abstract.

Finally, here are two links to recent papers related to plasmons and nanoshells, even if they're not centered on electronics, Shining a Light on Cancer Research (PDF format, 3 pages, 472 KB) and Plasmonic Nanoshells (PDF format, 23 pages, 667 KB). The above illustration has been extracted from this presentation.

Sources: Rice University, September 14, 2005; and various web sites

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