Here’s how the Cornell system works. First, a signal is encoded on laser light using a conventional modulator. The light signal is then coupled into the Cornell chip through an optical-fiber coil, which carries it onto a nanoscale-patterned silicon waveguide. Just as a guitar chord is made up of notes from different strings, the signal is made up of different frequencies of light. While on the chip, the signal interacts with light from a laser, causing it to split into these component frequencies. The light travels through another length of cable onto another nanoscale-patterned silicon waveguide, where it interacts with light from the same laser. In the process, the signal is put back together, but with its phase altered. It then leaves the chip by means of another length of optical fiber, at a rate of 270 gigabits per second.
The physics are complex, but the net effect, says Bergman, is to “take a stream of bits that are kind of slow and make them go much faster.” The time telescope transmits more data in less time, and does so in an energy-efficient manner, because the only power required is that needed to run the laser.
The Cornell device is one of a series of recent breakthroughs in silicon photonics. “Silicon is this amazing electronic material, and for a long time it was viewed as being a so-so optical material,” says Gaeta. Over the past five years, researchers have been overturning this notion. In 2005, researchers at Intel made the first silicon laser; subsequently, other optical components, including modulators–devices for encoding information on light waves–have been made from the material. “People keep saying you have to replace silicon to do very high-speed processing, but silicon may be the way to go,” says Gaeta.
Sticking with silicon has two advantages. First, manufacturers already have the infrastructure for making devices out of silicon. “You can leverage all the technologies that have been developed for electronics to make optical devices,” says Gaeta. And if electronics and optics can be made out of the same material, it could be much easier to integrate them on the same chip and have each do what it does best: processing in the case of electronics, ultrafast data transmission in the case of optics.