Nanostructures taste the rainbow

Engineers at Caltech have for the first time developed a light detector that combines two disparate technologies -- nanophotonics, which manipulates light at the nanoscale, and thermoelectrics, which translates temperature differences directly into electron voltage -- to distinguish different wavelengths (colors) of light, including both visible and infrared wavelengths, at high resolution.

Light detectors that distinguish between different colors of light or heat are used in a variety of applications, including satellites that study changing vegetation and landscape on Earth and medical imagers that distinguish between healthy and cancerous cells based on their color variations.

The new detector, described in a paper in Nature Nanotechnology on May 22, operates about 10 to 100 times faster than current comparable thermoelectric devices and is capable of detecting light across a wider range of the electromagnetic spectrum than traditional light detectors. In traditional light detectors, incoming photons of light are absorbed in a semiconductor and excite electrons that are captured by the detector. The movement of these light-excited electrons produces an electric current -- a signal -- that can be measured and quantified. While effective, this type of system makes it difficult to "see" infrared light, which is made up of lower-energy photons than those in visible light.

Because the new detectors are potentially capable of capturing infrared wavelengths of sunlight and heat that cannot be collected efficiently by conventional solar materials, the technology could lead to better solar cells and imaging devices.

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