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Recycling light

CAMBRIDGE, Mass. — Humanity started recycling relatively early in its evolution: there are proofs that trash recycling was taking place as early as in the 500 BC. What about light recycling? Consider light bulbs: more than one hundred and thirty years ago Thomas Edison patented the first commercially viable incandescent light bulb, so that “none but the extravagant” would ever “burn tallow candles”, paving the way for more than a century of incandescent lighting. In fact, emergence of electric lighting was the main motivating factor for deployment of electricity into every home in the world. The incandescent bulb is an example of a high temperature thermal emitter. It is very useful, but only a small fraction of the emitted light (and therefore energy) is used: most of the light is emitted in the infrared, invisible to the human eye, and in this context wasted.

Now, in a study published in Nature Nanotechnology on January 11th 2016 (online), a team of MIT researchers describes another way to recycle light emitted at unwanted infrared wavelengths while optimizing the emission at useful visible wavelengths. The paper was co- authored by MIT scientists: postdoc Ognjen Ilic, principal research scientist Ivan Celanovic, professors Gang Chen, John Joannopoulos, Peter Bermel (now at Purdue), and Marin Soljacic. While as a proof-of-concept the research group built a more energy-efficient incandescent light bulb, the same approach could also be used to improve the performance of other hot thermal emitters, including thermo-photovoltaic devices.

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