Cooling with Polariton

Shining light on an object to reduce its temperature seems a rather strange way, but laser cooling is frequently used in physics, especially to create super-cold samples. Now, however, a US physicist has proposed a way to cool laser semiconductors.

Although Jacob Khurgin of Hopkins University has not yet validated the technology, he quantified that this would lead to a much more efficient way of cooling for infrared receivers and electrical devices. another element ( Phys. Rev. Lett. 98 177401 )

The solid can be cooled if it absorbs a light quantum (photon) at an energy and then re-radiates a photon at a higher energy . As long as the energy generated is slightly larger than the energy collected, the temperature of the object will decrease. This effect, known as anti-Stokes photoluminescence (Skokes), has been used since the mid-90s to cool Yb doped glasses and other heavy rare earth elements.

However, the laser cooling attempt applied to semiconductors is much more difficult because the absorbed photons produce an electron-hole pair that the pair only occasionally reunites to produce. A photon has a higher energy. Instead, the recombination process often results in heat being radiated around the network. Even if re-radiation occurs, it is a good opportunity for the new photon to be reabsorbed by the semiconductor, further increasing the ability of the heating process.

Khurgin's solution is to give a small amount of metal, like silver Ag, about 10 nanometers in size, instead of a semiconductor. This is done to utilize the cooling effect of the plasmon-polariton surface (SPPs), which exists on the metal surface. SPPs are quantum vibrations that arise from the interaction of light with conductive electrons in metals.

While SPPs are normally found on the metal surface, Khurgin calculated that if the metal and semiconductor surfaces are separated by a very narrow slit, SPPs can be created in the semiconductor range. by reuniting process of electronic-hole pairs (see drawing). Khurgin also calculated that nearly all of those SPPs could escape from semiconductors and return up to 99.9% of their energy to metals - and thus cooling the semiconductor.

Khurgin said that if silver Ag is used as a metal and Gallium nitride (GaN) as a semiconductor, each SSP must deliver nearly three times the energy of a photon. He predicted that the device could achieve a cooling efficiency of up to 3%, enough for practical applications. According to Khurgin, technology could allow semiconductors in electronic devices to be cooled directly, rather than having to use external coolers. This may be particularly important for the design of infrared receivers used in Earth observation satellites, or in hand-held night vision devices . This work has just been published in the Physical Review Letters (Phys. Rev. Lett. 98 177401).

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According to PhysicsWeb.org & Physcal Review Letters, Vietnamese Physics