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A step toward optical transistors?

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(Image credit: McGill University)

As demand for computing and communication capacity surges, the global communication infrastructure struggles to keep pace since the light signals transmitted through fiber-optic lines must still be processed electronically, which creates a bottleneck in telecommunications networks. While the idea of developing an optical transistor to get around this problem is alluring to scientists and engineers, it has also remained an elusive vision, despite years of experiments with various approaches. Now, McGill University researchers have taken a significant, early step toward this goal by showing a new way to control light in the semiconductor nanocrystals known as “quantum dots.” In results published online recently, PhD candidate Jonathan Saari, Prof. Patanjali (Pat) Kambhampati and colleagues in McGill’s Department of Chemistry show that all-optical modulation and basic Boolean logic functionality – key steps in the processing and generation of signals – can be achieved by 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,” says Saari. “We’re still at the nascent stages, but this could mark a significant step toward optical transistors.” Quantum dots already are used in applications ranging from photovoltaics, to light-emitting diodes and lasers, to biological imaging. The Kambhampati group’s latest findings point toward an important new area of potential impact, based on the ability of these nanocrystals to modulate light in an optical gating scheme.