Finnish team builds world's first all optical calculator

July 30, 2018 // By Nick Flaherty
Researchers at Aalto University in Finland have developed the first binary calculator that entirely uses light instead of current.

The interdisciplinary team have shown how a new type of nanowire-based nanostructure enables light to perform logic functions, allowing simple addition and subtraction operations. The study, published in Science Advances , is the first to demonstrate nanoscale all-optical logic circuits.

'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,' said Dr Henri Jussila.

To build the nanostructure, the team took a novel approach to assemble two different semiconductor nanowires, indium phosphide and aluminum gallium arsenide. The one-dimenional nanowires function like nanosized antennas for light and the key is in the alignment. 'We used a simple combing technique, similar to how people comb their hair in the morning, to assemble these nanostructures,' said Jussila.

With this mechanical combing method, nanowires can be aligned in any specific direction, which differs from the randomly aligned nanowires typically used. This repetition is vital to get the antennas into ideal alignment. "Repeating the combing method allows us to build integrated devices of nanostructures in which two different types of nanowires are perpendicular to each other,' said Professor Zhipei Sun, who leads the Photonics group at Aalto University. 'The one-dimensional and crossbar structures are the core of our calculations because they enable the input light to choose which nanowire it interacts with--either the indium phosphide or the aluminum gallium arsenide,' said colleague Dr. He Yang.

Depending on the input, in this case the linearly-polarized light direction and its wavelength, the nanowires either interact with the input light or not. This is similar in practice to how the antennas used in old radio receivers work; they only receive signals when pointing in the optimal direction, typically upwards. Since the response of the different nanomaterials is different, the light output of the fabricated nanowire structure can be switched with different wavelengths and light direction for the successful


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