Soon we will be computing at the speed of light, if these engineers have anything to say about it. Just as optical fiber is replacing copper wires and the resultant data is made up of a photonic as opposed to an electronic stream, processing photonic signals on silicon chips is the next frontier in the evolution of computing.

Photonic signals travel hundreds of times faster than electronic signals, and unlike electronic signals they are not as suscpetible to signal loss or interference. However, the problem that has been holding back development of photonic ICs for the past 20 years is the issue of light isolation. Light by its very nature is omnidirectional. If light is piped into an optical circuit, it has the tendency to travel in two directions, which from a computing standpoint makes circuits unreliable.

In order for electronic circuits to function properly, a diode acts as a gate isolating electronic signals and only allowing them to pass in one direction. In order for photonic circuits to work, the world has been waiting for the equivalent of a photonic diode. A postdoctoral scholar at CalTech seems to have developed just that. Liang Feng, along with research and engineering colleagues, have come up with a new type of waveguide that solves this decades old problem.

According to Dr. Liang, “Normally, a light beam has exactly the same properties when it moves forward as when it’s reflected backward. In order to isolate light, its properties need to somehow change when going in the opposite direction. An optical isolator can then block light that has these changed properties, which allows light signals to travel only in one direction between devices on a chip.”

The new silicon device is 0.8 micron optical waveguide that allows light to travel syncronously in one direction, but when reflected back it becomes an asynchronous signal. As the signals are different there is no interference, and an optical isolator can now block the asynchronous signal effectively creating a one way photonic stream. While work so far has been for proof-of-concept, the researchers are already building an optical isolator that can be integrated onto a silicon chip.

In addition to CalTech, researchers at UCSD and Nanjing National Laboratory of Microstructures in China also contributed to the work in progress. What’s interesting is that this work is being funded by the US National Science Foundation and DARPA. Expect the Chinese to flood the market with a cheap knockoff as soon as the technology matures.

Source: Futurity

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