New milestone in laser cooling: Research team cools quartz glass to a record breaking 67 Kelvin

A group of researchers from the Fraunhofer Institute of Applied Optics and Precision Engineering IOF and the University of New Mexico successfully cooled silica glass by 67 Kelvin for the first time using optical laser cooling. Researchers from Jena and Albuquerque have published their results in the journal Optics Letters.

Cutting, drilling, welding - We usually associate laser with the heating of materials, such as working precisely on objects made of metal or stone. But in specific cases, materials can also be cooled through laser radiation - an effect known for the Doppler cooling of gases. However, laser radiation can also cause solid cooling.

This contradictory effect becomes possible through the so-called anti Stokes fluorescence cooling. In this process, a special high-purity material is excited by laser radiation. Due to the energy difference between the excitation laser and the radiation emitted by the material, energy is extracted from the material in the form of heat - it is cooled.

A research team composed of researchers from Fraunhofer IOF and the University of New Mexico studied laser cooling of doped quartz glass and made significant progress in their paper.

For many years, the cooling of quartz glass has been considered impossible. But in 2019, researchers from Jena and Albuquerque first demonstrated laser cooling of ytterbium doped quartz glass.

At that time, the cooling temperature only reached 0.7 Kelvin of room temperature. In order to overcome the previous cooling threshold, the specific process and exact composition of manufacturing doped materials were optimized. In addition, the excitation laser used for measurement at the University of New Mexico has been improved in close collaboration with Fraunhofer IOF researchers.

Therefore, researchers have now achieved a new record breaking cooling: by emitting radiation from ytterbium doped silica rods using an excitation laser with a power of 97 watts and a wavelength of 1032 nanometers, researchers were able to demonstrate a 67 Kelvin decrease in room temperature within two minutes.

Due to this new development, new and extremely stable lasers and low noise amplifiers can be developed for precision metrology or quantum experiments in the future. In addition, optimized processes can promote vibration free cooling, thus opening up new potential applications in material analysis and medical diagnosis through cryomicroscopy and gamma spectroscopy.

The potential use of this material in fibers is particularly interesting. In the future, new technologies can be used to develop high-performance fiber lasers without dealing with the limiting effects of thermal instability.

The new process represents a significant progress in laser cooling, and according to expert theoretical considerations, the use of laser has not yet achieved the maximum possible temperature reduction.

Source: Laser Net