Experimental realization of strong coupling between a cold atomic ensemble and an optical fiber microcavity

The cavity quantum electrodynamics (QED) system is a promising platform for quantum optics and quantum information experiments. Its core is the strong coupling between atoms and optical cavity, which causes difficulty in the overlap between the atoms and the antinode of optical cavity mode. Here, we use a programmable movable optical dipole trap to load a cold atomic ensemble into an optical fiber microcavity and realize the strong coupling between the atoms and the optical cavity in which the coupling strength can be improved by polarization gradient cooling and adiabatic loading. By the measurement of vacuum Rabi splitting, the coupling strength can be as high as gN = 2 pi x 400 MHz, which means the effective atom number is Neff = 16 and the collective cooperativity is CN = 1466. These results show that this experimental system can be used for cold atomic ensemble and cold molecule based cavity QED research.

Automated summary

This experimental study achieved a strong coupling between a cold atomic ensemble and an optical cavity by using a programmable movable optical dipole trap to load the atomic ensemble into an optical fiber microcavity. By measurement of the vacuum Rabi splitting, a high coupling strength and effective atom number were obtained. This experimental system has important implications for research on cold atomic ensemble and cold molecule based cavity QED.