Cavity-enhanced optical bistability of Rydberg atoms

Optical bistability (OB) of Rydberg atoms provides a new, to the best of our knowledge, platform for studying nonequilibrium physics and a potential resource for precision metrology. To date, the observation of Rydberg OB has been limited in free space. Here, we explore cavity-enhanced Rydberg OB with a thermal cesium vapor cell. The signal of Rydberg OB in a cavity is enhanced by more than one order of magnitude compared with that in free space. The slope of the phase transition signal at the critical point is enhanced more than 10 times that without the cavity, implying an enhancement of two orders of magnitude in the sensitivity for Rydberg-based sensing and metrology.