A new way of controlling light with quantum dots provides a platform for optical logic that could replace electronic transistors with optical ones. As demand for computing and communication capacity surges, the global communication infrastructure struggles to keep pace: The light signals transmitted through fiber optic lines must still be processed electronically, creating bottlenecks in telecommunications networks. To get around this problem, scientists have sought to develop optical transistors, but these devices have remained elusive despite years of experiments with various approaches. McGill University researchers have shown that all-optical modulation and basic Boolean logical functionality can be achieved by using laser-pulse inputs to manipulate the quantum mechanical state of a semiconductor nanocrystal. These nanocrystals can form a completely new platform for optical logic, they said. Courtesy of McGill University. Now McGill University researchers have made an important discovery that may help make optical transistors a reality. The investigators have shown that all-optical modulation and basic Boolean logical functionality — key steps in the processing and generation of signals — can be achieved using laser-pulse inputs to manipulate the quantum mechanical state of a semiconductor nanocrystal. “Our findings show that these nanocrystals can form a completely new platform for optical logic,” said Jonathan Saari, a doctoral candidate in the chemistry department. “We’re still at the nascent stages, but this could mark a significant step toward optical transistors.” Professor Patanjali Kambhampati’s group has found a new use for quantum dots — already used in applications such as photovoltaics, LEDs, lasers and bioimaging — based on the ability of these nanocrystals to modulate light in an optical gating scheme. “These results demonstrate the proof of the concept,” Kambhampati said. “Now we are working to extend these results to integrated devices, and to generate more complex gates in hopes of making a true optical transistor.” The findings build on previous research that revealed unobserved light-amplification properties unique to quantum dots. (See: Light Squeezed From QDs) The research was published in Nano Letters (doi: 10.1021/nl3044053). For more information, visit: www.mcgill.ca