Plasmonic Laser Heralds New Generation of Computing

If you’re into buzzwords, nanoplasmonics is one you ought to know about. Nanoplasmonics, we’re told, is the next big thing–the field that will allow us to sense and manipulate the world on the smallest of scales.

Plasmons, of course, are waves in the sea of free electrons inside and on the surface of metals. These waves are nanoscopic in size and have a frequency measured in attoseconds (equivalent to the optical range of UV to infrared). They are quantized, which means they can demonstrate the strange properties of quantum mechanics. And they are incredibly sensitive to the world around them. This makes plasmons perfect for sensing everything from photons, magnetic fields and electrons. They promise a new generation of photodetectors, scanning microscopes and various biomedical devices.

But there’s a problem. There is currently no active device that can generate and amplify nanoplasmonic signals to make them easier to monitor.

What’s needed, says Mark Stockman at the Max Planck Institute for Quantum Optics in Germany, is the nanoplasmonic equivalent of a transistor and he has come up with a device that can do the trick.

His device is the nanoplasmonic equivalent of a laser. He calls it a spaser (Surface Plasmon Amplification by Stimulated Emission of Radiation). In a spaser, a surface plasmon plays the same role as a photon in a laser.

So the idea is that a plasmon enters a resonator in the form of a nanoparticle that is embedded in some kind of gain material containing chromophores such as semiconductor nanocrystals or dye molecules. Obviously, the gain medium must be capable of population inversion which allows it to lase (or “spase” in this case).

Stockman introduced the idea of a spaser a few years ago and the first one was built earlier this year by a group in the US. But today, Stockman reveals its full power in the first full quantum mechanical description of the device. And it looks mighty useful too.

A spaser is, in effect, a nanoscale plasmon amplifier. But it can also generate plasmons as well as store them. That’s roughly what an ordinary field effect transistor does with electrons but Stockman has calculated that it can do all this roughly three orders of magnitude faster. Yep, that’s a thousand times faster.

Stockman has an powerful vision for his device:

“One may envision ultrafast nanoplasmonic chips with a high degree of integration where spasers communicate and control each other through their near fields or are connected with nanoplasmonic wires. These can perform ultrafast microprocessor functions.”

What he’s describing, of course, is a new generation of ultrafast computers based on plasmonics.

That’s ambitious. What he’ll need are powerful backers with deep pockets and he might just get them. Because spasers are based on metals rather than semiconductors, they are much more resistant to ionising radiation. That means they will be of special interest to the nuclear and aerospace industries and of course to the military.

Expect to hear a lot more about them.

Ref: arxiv.org/abs/0908.3559: Spaser as Nanoscale Quantum Generator and Ultrafast Amplifier