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Scientists at North Carolina State University have successfully “squeezed” infrared light to 10 percent of the wavelength while retaining its frequency.
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This breakthrough was achieved using a thin membrane of strontium titanate and the phonopolaritons it produced after using synchrotron near-field spectroscopy.
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This thin film could lead to a variety of new infrared imaging devices and other thermal management systems, potentially releasing heat by converting it into infrared light.
The human eye is a natural wonder, the result of millions of years of evolutionary tinkering, and… remarkable restrictive. Our eyes can only see a small part of the electromagnetic spectrum, so if we want to see anything else, we have to rely on technology that can glimpse these ‘invisible’ wavelengths.
One of the most useful of these wavelengths is infrared, whose waves extend between 760 nanometers and 100,000 nanometers (the name comes from the fact that it just now longer than the color red, the longest wavelength in the visible spectrum). Infrared is used in a variety of applications, especially in imaging, and being able to manipulate this wavelength can produce better results.
That’s why scientists at North Carolina State University have been working to successfully “squeeze” infrared light down to 10 percent of its wavelength while preserving its frequency. The researchers achieved this breakthrough by using a special class of oxide membranes instead of bulk crystals, which is traditionally only possible hardly squeeze infrared light. The results of this study were published earlier this month in The New York Times magazine log Nature communication.
“We have shown that we can limit infrared light to 10% of the wavelength, while maintaining its frequency. This means that the time it takes for a wavelength to change is the same, but the distance between the peaks of the wave is the same. much closer together,” Yin Liu, a co-author of the study, said in a press statement. “Bulk crystal techniques limit infrared light to about 97% of the wavelength.”
According to the statement, the researchers used “transition metal perovskite materials” in the study. Using pulsed laser deposition – which involves a powerful pulse laser beam in a vacuum chamber – the researchers grew a 100-nanometer-thick membrane made of an oxide of strontium and titanium called strontium titanate (SrTiO3). Once completed with very few defects, the films were removed from that substrate and placed on a silicon substrate.
To test this new device and see if it could “squeeze” infrared light to a useful degree—an idea that the researchers say was only theoretical until now—the team turned to the Advanced Light Source at Lawrence Berkeley National Laboratory . This research facility manages a infrared program able to investigate materials on a micro and nano scale. The team performed synchrotron near-field spectroscopy on the strontium titanate thin film, and what was once theoretical became very practical.
Understanding what happened next requires a quick trip to particle physics 101. Photons are particles of light and the fundamental unit of the electromagnetic spectrum. Phonons, on the other hand, are “a nice word for a heat particle” (according to MIT), but can also be thought of as sound energy. Both photons and phonons are concerned with excitations and vibrations. However, when an infrared photon is coupled to an optical phonon (also called a phonon that can emit or absorb light), it forms a quasiparticle called a ‘phonon polariton’. ” It is these polaritons that cause the squeezing.
“Theoretical papers proposed the idea that transition metal perovskite oxide membranes would allow phonon polaritons to confine infrared light,” Liu said. “And our work now shows that the phonon polaritons trap the photons and also keep the photons from extending beyond the surface of the material.”
Liu and his colleagues said this breakthrough could lead to a whole new generation of infrared imaging technologies and thermal management devices. “Imagine,” Liu said, “if we could design computer chips that could use these materials to release heat by converting it into infrared light.”
Thanks to this breakthrough, we may not have to imagine it for much longer.
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