To Catch a Rainbow, New Material Slows Light

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Engineers trying to develop new materials with practical applications are no longer just chasing rainbows- they’re also catching them.

A University of Buffalo engineering team, led by Qiaoqiang Gan, PhD, has come up with an efficient way to absorb different frequencies of light, an improvement that could lead to advances in solar energy, stealth technology, and other fields.

The “hyperbolic metamaterial waveguide” developed by Gan and his team functions like a microchip made of alternate ultra-thin films of metal, semiconductors, and insulators. The waveguide stops and absorbs each frequency of light at slightly different places in a vertical direction, allowing it to catch a “rainbow” of wavelengths.

“Electromagnetic absorbers have been studied for many years, especially for military radar systems,” Gan said. “However, it is still challenging to realize the perfect absorber in ultra-thin films with tunable absorption band.

We are developing ultra-thin films that will slow the light and therefore allow much more efficient absorption, which will address the long existing challenge.”

Because light photons move so quickly, they’re very difficult to tame without the use of freezing materials, like cryogenic gases, that can only be used inside a laboratory. But this new metamaterial waveguide provides a more practical way for engineers to slow down light, one that can be put to use in the real world.

Researchers believe this efficient hyperboloid film- which can capture visible, near-infrared, mid-infrared, terahertz, and microwave wavelengths- could be used on solar panels and other energy-harvesting devices. Gan said its ability to absorb mid-infrared wavelengths might make it especially useful in devices that recycle heat after sundown.

And the material’s ability to absorb many different wavelengths, including some commonly used for location and detection, also means it might be used as a coating material on objects like the stealth bomber or be useful in developing new military technology.

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