A research team at Singapore’s Nanyang Technological University (NTU) has successfully used a laser to cool down a semiconductor material known as Cadmium Sulfide. The results of the recently published study could lead to the development of self-cooling computer chips and smaller, more energy efficient air conditioners and refrigerators that don't produce greenhouse gases.

Cadmium Sulfide, an inorganic compound, is a type of group II-IV semiconductor commonly used in pigments to form the color yellow. It is also used as a thin-film layer in solar cells, sensors and electronics. Led by Assistant Professor Xiong Qihua from the School of Physical and Mathematical Sciences and the School of Electrical and Electronic Engineering, the research team optically-refrigerated the compound from 20° C (68° F) down to -20° C (-4° F).


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The potential for using semiconductors as the basis for cooling structures powered by light could have some very usable permutations in the real world. Currently, high-powered devices such as Magnetic Resonance Imagers (MRIs), night-vision goggles, satellite cameras, and even air-conditioning systems and refrigerators all have one thing in common: they have bulky, noisy, highly mechanical or complex cooling systems. These systems consume large amounts of power and – in the case of refrigerants especially – often release harmful greenhouse gases into the atmosphere.

As computer chips, or CPUs, become more powerful, they also generate higher amounts of heat, too. Some pundits argue that if new cooling techniques are not found, thus creating a new, lower temperature working environment, then the regular increases in CPU speeds we have become accustomed to will continue to slow.

The breakthrough in laser cooling (aka optical refrigeration) technology could lead to compact, cost effective, vibration-free and cryogen-less cooling systems in many different applications. CPUs could reduce their reliance on external cooling systems like fans and incorporate built-in laser controlled systems instead. The potential for minimized heat and prolonged battery life in items such as tablets and smartphones is another example.

Or as Professor Xiong Qihua says, “If we are able to harness the power of laser cooling, it would mean that medical devices which require extreme cooling, such as MRI which uses liquid helium, could do away with bulky refrigerant systems with just an optical refrigeration device in its place.” And adding to that, “it would also remove the need for compressors and coolants in air-conditioning and refrigerators used in our homes and automobiles, saving space, energy and greenhouse gases.”

In theory, semiconductors can be cooled much further in temperature than minus 20 degrees Celsius. The research team is now looking to bring the laser cooling technique down to liquid helium temperature, at minus 269° Celsius. This is something that researchers at the Niels Bohr Institute managed to achieve with their own laser cooling method.

The experiment was funded by the NTU, Professor Xiong’s National Research Foundation Fellowship grant and the Ministry of Education Academic Research Fund. It took three years complete.

The study was published in January edition of the journal Nature.

Source: Nanyang Technological University