Replacing electrons with photons

Left: Illustration of terahertz optical switches shows the vanadium dioxide nanoparticles coated with a "nanomesh" of smaller gold particles. Right: Scanning electron microscope image of the switches at two resolutions. Credit: Haglund Lab / Vanderbilt

We have available an amazing transportation capacity through optical fibre, trillions of bits per second and more. The limits are actually far higher but we are constrained by the electronic-photonic transformation process. Today electronics can reach 40 Gbps in the conversion from electrons through photons via a laser and these laser are, relatively speaking, bulky. To reach capacity of the order of trillion of bits we use DWDM techniques where we have many conversion of electrons into photons going on in parallel, each one reaching a maximum of 40Gbps (normally the work at 10 Gbps since the components involved are cheaper and more stable).

Finding ways for increasing this conversion speed is the dream, and goal, of several researchers. The problem is that the silicon used in laser can only go that fast.

Now researchers at the Vanderbilt University have found a way to increase a thousands fold the conversion speed by using vanadium dioxide based chips. And these "chips" measure just 200nm, that is 500 times less than a human hair.

The researchers have managed to create a metamaterial, not existing in nature, by using nanoscale of VO2 and gold particles. The nanoscale of VO2 can be transparent or opaque and by changing their state you can use them as an optical switch. They are both incredibly small and incredibly fast, being able to switch several trillions times per second.

Besides, the manufacturing process is compatible with the manufacturing of silicon chips, so it is possible to integrate them in silicon, they can operate in the visible and infrared light spectrum, the one used in telecommunications and consume extremely little power, 10 trillionths of a calorie per bit (100 FemtoJoule).
although the properties of VO2 have been known for many decades it is only through the use of massive computational power in these last years that have been possibile to understand the physics behind them and therefore start to find ways to exploit them.

Author - Roberto Saracco

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