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Boffins stumble upon method to make silicon control lasers

Quantum experiment may clear the way for viable silicon photonics – chips with electronic and photonic interconnects

Researchers in a team led by the University of Surrey reckon they have accidentally found a new way to use silicon as a powerful photonic informational manipulation material, potentially making it possible to produce viable silicon devices that can control multiple lasers.

The discovery could be significant because silicon is a fabulous semiconductor yet it has long been thought to be a poor choice for photonics applications. The researchers behind this work say nobody has bothered to commercialise silicon light-emitting diodes, lasers, or displays.

However, the industry has long dreamed of achieving practical silicon photonics, devices built on silicon that offer both electronic and optical interconnects. Such machines promise both to speed up computer networking and processing, and to take advantage of the world's substantial investment in silicon-based manufacturing processes.

Ben Murdin, co-author of the study and a physics professor at Surrey Uni in England, explained the discovery in a canned statement on Tuesday:

Our finding was lucky because we weren't looking for it. We were trying to understand how a very small number of phosphorus atoms in a silicon crystal could be used for making a quantum computer and how to use light beams to control quantum information stored in the phosphorus atoms.

We were astonished to find that the phosphorus atoms were re-emitting light beams that were almost as bright as the very intense laser we were shining on them.

optic fibre

The good optics of silicon photonics: Light sailing serenely down a fibre


The science behind it boils down to nonlinearity: by filtering the beam through a material, one changes the wavelength, affecting things like color and even making nonvisible light visible. This is basically how green laser pointers work, an invisible infrared diode's output is modified by a nonlinear crystal and voila, the wavelength is halved, and it's visible as green.

But nonlinear optics doesn't stop there: it can also be used to control the direction of the beam's information. Furthermore, stronger nonlinearities are easily controlled with weaker input beams and the researchers discovered that silicon possesses the strongest nonlinearity of its type ever found.

As the boffins put it in their paper, published in the journal Light: Science and Applications:

The immediate implication of our results is the efficient generation of intense coherent THz light via upconversion (also a χ(3) process), and they open the door to exploitation of non-degenerate mixing and optical nonlinearities beyond the perturbative regime.

Funnily enough, the researchers had shelved the data for a few years after their first observations while they scratched their heads on how to prove the origin of the beams, we're told. Now, they've presented their findings. ®

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