March 4th, 2015
Imagine refrigeration without the vibrations, noise, and the need for cooling chemicals. The answer, which has been experimented with since the 1980’s, is known as laser cooling. Just as the name suggests, the idea is to use a laser light field to reduce the average motion of atoms, which then lowers the object’s temperature. This had worked successfully only with gases, until now.
This week the news hit that a research team in Singapore had successfully used laser cooling on a semiconductor at room temperature, lowering its temperature by 40 degrees Kelvin. The achievement opens the door to cooling larger objects, specifically as an ideal solution for cooling satellites. Even further than its possibilities for space applications, this could also be a way for a laser to cool itself.
The semiconductor that was used in this latest development was an extremely thin ribbon, often referred to as a “nanobelt”, of cadmium sulphide (CdS). As Physics World explains it: ” …the transition involves an absorbed photon being converted into an electron–hole pair. This “exciton” annihilates and the semiconductor emits a higher-energy photon – with the extra energy coming from the annihilation of phonons. As a result, the sample loses phonons and cools.”
According to the team in Singapore this process is easy to miniaturize, which again leads to the excitement at possible applications in the near future. The obstacle now is to replicate this cooling process on materials that are larger than the CdS ribbon. Once that happens, the world of technology will get even cooler.
Source: Physics World
Photo: fatllama / flickr
cooling technology, laser refrigerator