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New Research Highlights Recycling Light from Atom Cooling

Researchers from University of Maryland theorize that laser photons used for cooling atoms have a unique thermal distribution

Laser cooling is considered from the perspective of the atoms that are being chilled. However, a new study by Chiao-Hsuan Wang from the University of Maryland and his collogues suggested that the photons that carry away the heat may have a wide variety of useful properties. The researchers modeled the laser cooling of atoms inside a cavity. It was observed that atoms scatter photons that have a thermal energy distribution, which resembles that of interacting particles. The research published in the journal Physical Review A on July 19, 2018, stated that these photons might be recycled and used to mimic other physical systems.

Scattering of light from a gas or other medium leads to its energy distribution, which is a blackbody spectrum. It is characterized by the number of photons per energy ‘bin’ that is determined by temperature. In recent research, the team used semiconductor micro-cavities or molecular dyes to accumulate more photons per energy bin than expected for a blackbody distribution. These system, characterized by a nonzero chemical potential, can act similar to the photon equivalent of a Bose-Einstein condensate (BEC).

The researchers realized that similar photon crowding occurs for the leftover light from laser cooling. The team modelled a cigar-shaped collection of laser-cooled atoms that was confined in an optical cavity. The team then calculated the distribution of scattered photons and the data revealed that it can be characterized by a temperature equal to the temperature of atoms. Moreover, a chemical potential equal to the energy of the laser photons can also define the distribution. With such distribution, photons behave as if they interacted with each other and could be used to carry out optical simulations of many-body quantum phenomena including the quantum Hall effect.