After 15 years of wildly mixed results from colloidal quantum dot light-amplification experiments, many researchers were convinced that some unknown law of physics was stymieing their efforts to drive forward telecommunications technology. Now Patanjali Kambhampati begs to differ.
Kambhampati and his colleagues in the Department of Chemistry have successfully amplified light using this once inconsistent technology. In telecommunications, data is encoded into beams of high-powered coherent light and transmitted through fibre-optic cables—but, because these laser signals diminish over distance, they must be amplified to maintain data integrity. The best available amplification technology is the quantum well, a thin sheet of semi-conductor material that confines electrons to a one-dimensional plane. But, for over 10 years, researchers hoped that colloidal quantum dots, a three-dimensional box for electrons that is a billionth of a meter across, would yield superior results, and at a cheaper cost. In some cases the dots worked, and in many cases they didn’t, and nobody knew why. Until now.
Kambhampati and his team discovered there was nothing wrong with the dots themselves—it was the light being sent into the dots. The McGill researchers discovered that the dots absorb different colours of light in crucially distinct ways. “If you’re not careful in colour choice, you could get no amplification or huge amplification,” explains Kambhampati. “We figured out which colours are useful and which aren’t.” Now that the basic science has been ironed out—and the results published in the March 2009 issue of Physical Review Letters—the team is collaborating with Zetian Mi in the Department of Electrical and Computer Engineering to invent a new amplification device.
This research received funding from the Canada Foundation for Innovation, the Natural Sciences and Engineering Research Council of Canada and the Fonds québécois de la recherche sur la nature et les technologies.