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Scientists from North Carolina State University successfully “squeezed” infrared light to 10 percent of its wavelength while maintaining its frequency.
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This breakthrough was achieved using a thin membrane of strontium titanate and the phono polaritons 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 shedding heat by turning it into infrared light.
The human eye is a natural wonder, the result of millions of years of evolutionary tinkering, and… remarkably limiting. Our eyes can only see a small sliver of the electromagnetic spectrum, so to see anything else requires relying on technology that can glimpse these “invisible” wavelengths.
One of the most useful of these wavelengths is infrared, the waves of which stretches between 760 nanometers to 100,000 nanometers (the name comes from the fact that it’s just longer than the color red, the longest wavelength in the visible spectrum). Infrared is used in all sorts of applications—especially imaging—and being able to manipulate this wavelength can produce better results.
That’s why scientists from North Carolina State University worked to successfully “squeeze” infrared light to 10 percent of its wavelength while maintaining its frequency. The researchers achieved this breakthrough by using a special class of oxide membranes rather than bulk crystals, which can traditionally only barely squeeze infrared light. The results of this study were published earlier this month in the journal Nature Communications.
“We’ve demonstrated that we can confine infrared light to 10% of its wavelength while maintaining its frequency—meaning that the amount of time that it takes for a wavelength to cycle is the same, but the distance between the peaks of the wave is much closer together,” Yin Liu, a co-author of the study, said in a press statement. “Bulk crystal techniques confine infrared light to around 97% of its wavelength.”
According to the statement, the researchers made use of “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 flaws, 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 had insofar only been theoretical, according to the researchers—the team turned to the Advanced Light Source at the Lawrence Berkeley National Laboratory. This research facility runs an infrared program capable of probing materials at micro- and nano-scales. The team performed synchrotron near-field spectroscopy on the thin strontium titanate film, and what was once theoretical became very much practical.
To understand what happened next requires a brief foray into Particle Physics 101. Photons are particles of light and the fundamental unit of the electromagnetic spectrum. Phonons, on the other hand, are “a fancy word for a particle of heat” (according to MIT), but can also be thought of as sound energy. Both photons and phonons deal in the realm of excitations and vibrations—however, when an infrared photon is coupled with an optical phonon (a.k.a. a phonon that can emit or absorb light), then it forms a quasi-particle called a “phonon polariton.” It’s these polaritons that do 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 demonstrates that the phonon polaritons do confine the photons, and also keep the photons from extending beyond the surface of the material.”
Liu and his colleagues said that this breakthrough could lead to a whole new generation of infrared imaging technologies and thermal management devices. “Imagine,” Liu said, “being able to design computer chips that could use these materials to shed heat by converting it into infrared light.”
Well, thanks to this breakthrough, we may not have to imagine for long.
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Source Agencies
