August 2, 2018

World’s first all-optical calculator built at Aalto

Scientists around the globe are searching for ways to harness photonics to enable the next generation of computing.
Scientists around the globe are searching for ways to harness photonics to enable the next generation of computing.
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An interdisciplinary team of researchers at Aalto University has taken a pivotal step in the journey towards optical computing by becoming the first in the world to demonstrate nanoscale all-optical logic circuits.

The nanowire-based structure developed by the team enables light to perform logic functions such as addition and subtraction.

“We’re able to perform binary number calculations and show, for instance, how this nanostructure can carry out these functions just like a simple pocket calculator – except that instead of using electricity, the nanostructure uses only light in its operation,” says Henri Jussila, the project co-ordinator at Aalto University.

Photonics has garnered considerable attention as scientists around the globe search for ways to enable the next generation of computing and as electronic processors, which perform the basic arithmetic, logical and control operations for devices such as smartphones, are approaching their limits.

Jussila and his research team built the nanostructure by assembling semiconductor nanowires from two different materials – indium phosphide and aluminium gallium arsenide – both of which have a one-dimensional structure that allows them to function like nano-sized antennas for light.

The wires were then aligned perpendicularly to each other by repeatedly using a simple combing technique – one that is similar to how people comb their hair in the morning, according to Jussila.

“The one-dimensional and crossbar structures are at the core of our calculations because they enable the input light to choose which nanowire it interacts with,” explains He Yang, a post-doctoral researcher at Aalto University.

Whether it is the indium phosphide or aluminium gallium arsenide nanowire that interacts with the light depends on the linearly polarised light direction and its wavelength. As the materials respond to light differently, the output of the nanostructure can be switched to perform logic operations by adjusting light direction and wavelength.

The findings of the research team were published in Science Advances.

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