Researchers develop light modulator to transfer Gigabyte files in less than a second
The University of California has created a miniature optical device that could enable the large data files for 3D movies to be downloaded to a smartphone in seconds.
The engineering team’s breakthrough system uses the “wonder compound” graphene to flash a light on and off as a network modulator, a speed controller for transmitting data. Professor Xiang Zhang and his researchers have tuned the graphene electrically to absorb light wavelengths used in communications.
“Graphene enables us to make modulators that are incredibly compact and that potentially perform at speeds up to ten times faster than current technology allows,” said Zhang. “This new technology will significantly enhance our capabilities in ultrafast optical communication and computing.”
Extremeband Rather Than Broadband
Graphene is being seen as a cheaper substitute for silicon and in Zhang’s implementation, very little of the material is required for use in the new modulator. The team claimed that the carbon in a “lead” pencil can provide enough graphene to make a billion optical modulators which brings the price and the size down to levels that would allow widespread use in smartphones.
By layering graphene on top of a silicon waveguide in the optical modulator, the researchers claim to have achieved a modulation speed of a gigahertz. They further estimate that this could, theoretically, reach 500 gigahertz, or around 500Gbits per second.
The Fermi level, or energy of the graphene’s electrons, quickly changes as volotage is applied, determining whether light is absorbed or not. With a negative voltage, electrons are pulled out of the graphene to stop the absorb of photons. When a positive voltageis applied, the electrons can pass photons but the team had to find the optimumvoltage because too much packs the electrons so tightly they cannot absorb photons, giving the same effect as a negative voltage.
Graphene-based modulators would only measure 25 square microns, compared with the comparitively large few square millimeters of a typical modulator currently in production. The graphene devices could be available for mobile devices in the “next few years”, Zhang said.
“Graphene-based modulators not only offer an increase in modulation speed, they can enable greater amounts of data packed into each pulse,” says Zhang. “Instead of broadband, we will have ‘extremeband’.”