A team of researchers led by Osaka University and National Taiwan University created a system of nanoscale silicon resonators that can act as logic gates for light pulses. This work may lead to the next generation of silicon-based computer processors that bridge the gap between electronic and optical signals.

Silicon is among the abundant elements on our planet—and is the basis for all modern computing. That is, from smartphones to mainframes, all computation happens based on electrical signals coursing through transistors. Making switches and from electronic signals is easy, since voltages can control the flow of current in other wires. However, data on the internet is primarily sent as over fiber . The ability to control both data and logic completely with on silicon could lead to much faster devices.

The challenge is that particles of light, called photons, hardly interact with each other, so pulses cannot switch each other on or off to perform logical tasks. Nonlinear optics is the field of study that works to find materials in which beams of light interact in some way. Unfortunately, the non-linearity of single crystal silicon is extremely weak, so in the past, it was necessary to use very intense lasers.

Now, scientists at Osaka University and National Taiwan University have increased the nonlinearity of silicon 100,000 times by creating a nano-optical resonator, so that all-optical switches can be operated using a continuous low-power laser. They accomplished this by fabricating tiny resonators from blocks of silicon less than 200 nm in size. Laser light with a wavelength of 592 nm can become trapped inside and rapidly heat the blocks, based on the principle of Mie resonance. "A Mie resonance occurs when the size of a nanoparticle matches a multiple of the light wavelength," author Yusuke Nagasaki says.

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