One wouldn't expect a laser, which typically gives off heat, to cool water. However, scientists have demonstrated the first example of a laser beam being used to lower the temperature of water or similar liquids, such as saline solution, by roughly 36 degrees Fahrenheit.
The advance could help industrial electronic developers "point cool" tiny areas in, for example, microprocessors, cooling specific components to prevent overheating.
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The laser refrigeration work was done by a team of researchers at the University of Washington, including Peter Pauzauskie, an assistant professor of materials science and engineering.
"It was really an open question as to whether this could be done because normally water warms when illuminated," Pauzauskie told UW Today.
The team used an infrared laser to excite electrons in a single microscopic crystal suspended in water. That produced a unique kind of glow that had slightly more energy than the amount of light absorbed. As a result, the higher-energy glow carried heat away from the crystal and the surrounding water cooled.
While laser refrigeration was first revealed back at Los Alamos National Laboratory back in 1995, it was done in vacuum conditions. The University of Washington's breakthrough marks the first time the process has been demonstrated in everyday conditions.
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Throughout the experiment, the UW team used a less expensive alternative to growing laser crystals: a low-cost hydrothermal process that can be used to manufacture a laser crystal for laser refrigeration. Furthermore, the team designed an instrument that uses a laser trap to "hold" a single nanocrystal surrounded by liquid and illuminate it with the laser.
The study, which was funded by the Air Force Office of Scientific Research and the UW, was published this month in the Proceedings of the National Academy of Sciences.
via University of Washington