Light replaces wires




photo credit: Vuckovic Lab 


Light is much more efficient at transmitting data than electricity can through wires, but getting it to work reliably in a computer has been somewhat problematic. A team of engineers have just announced a new “optical link” device made out of silicon that is able to bend light at right angles, which is an important advancement toward replacing electric wires in computers with optics. The research was led by Jelena Vuckovic of Stanford University. The paper was published in the journal Scientific Reports.

 "Light can carry more data than a wire, and it takes less energy to transmit photons than electrons," Vuckovic said in a press release.

The current paper builds off of the lab’s previous work, in which Vuckovic’s team developed an algorithm that allowed for necessary optical devices to be developed automatically. It also allowed them to design the nanostructures necessary to manipulate light for optical data transmission. 

It was that algorithm that allowed the team to build the optical link: a very small piece of silicon with nanoscale vertical etchings. The eight-micron-long link acts like a prism, breaking down beams of light based on wavelength. The etchings are shaped so they direct the light at 90 degree angles in opposite directions, forming a T. The ability to manipulate the light in this manner is a significant step forward in optical data transmission.

The link is made out of silicon because its index of refraction (an indicator of how quickly light travels through a certain material) is 3.5. This is much slower than infrared light moves through water (1.3) or air (just about 1). The spaces between the etched lines allow the researchers to precisely manipulate how the light will be reflected and transmitted as the light passes between air and silicon.

"We wanted to be able to let the software design the structure of a particular size given only the desired inputs and outputs for the device," Vuckovic explained. "For many years, nanophotonics researchers made structures using simple geometries and regular shapes. The structures you see produced by this algorithm are nothing like what anyone has done before.”

Though the link is an impressive device now, the algorithm first approached it as an ordinary piece of silicon. The etched lines were added and tweaked as necessary, based on the success predicted by the computational model's use of convex optimization. Though the computer needs to run several hundred trials to make sure the optical link is calibrated correctly, it only takes about 15 minutes to do.

"There's no way to analytically design these kinds of devices," lead author Alexander Piggott added, speaking to the superlative advantage the algorithm brings.

In addition to the T-shaped beams of light generated by the link in this study, the algorithm makes it possible to have endless ways to manipulate light, which could be very useful in optic data transmission as the field progresses.

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