Superabsorption refers to a 'super' version of absorption just like superradiance is a 'super' version of emission. In superabsorption, correlated atoms collectively absorb light. The light can be absorbed completely and the number of absorbed photons is proportional to the square of the number of atoms. Although superabsorption has been highly anticipated, it has not been realized until now. In a paper recently published in the journal Nature Photonics, the research team led by Prof. Kyungwon An at Seoul National University reports realization of superabsorption by time reversal of superradiance process. In their experiment, barium atoms in a beam were prepared in a superradiant state and interacted with a probe field in a cavity. The phase of the superradiant state was then adjusted to reverse the otherwise superradiant process in time. The atoms then absorbed light instead of emitting light, resulting in superabsorption. The observed absorption rate was about 10 times faster than that of ordinary absorption for the same number of atoms (about 10 atoms in their experiment). Moreover, the light was completely absorbed in a finite time and the number of absorbed photons was proportional to the square of the number of atoms. Superabsorption can be utilized in enhancing absorption efficiency in solar cells and photosynthesis as well as in quantum memory and light-matter quantum interfaces.

Authors: Daeho Yang, Seunghoon Oh, Junseok Han, Gibeom Son, Jinuk Kim, Junki Kim, Moonjoo Lee, and Kyungwon An

Nature Photonics (2021), https://doi.org/10.1038/s41566-021-00770-6

Link: https://www.nature.com/articles/s41566-021-00770-6