Enhanced measurement of microwave electric fields with collective Rabi splitting

The collective effects of intracavity Rydberg atoms are investigated and proposed to detect microwave (MW) electric (E) fields with collective Rabi splitting (CRS). When a cavity field drives atoms from ground states to their excited states and a control field further drives them to Rydberg states where a MW field couples Rydberg states, the cavity transmission exhibits a four-peak characteristic, and two side peaks represent the CRS. It is interesting to find that the frequency splitting of CRS changes linearly with the MW-field strength, which can be used to probe MW E-field strength. In the strong coupling regime, the collective effect of Rydberg atoms broadens the CRS peak distance and could improve the detection sensitivity by about 7 times under the given conditions, compared with the common electromagnetically induced transparency scheme. The effects of atomic density and control-field strength on the CRS spectrum are also discussed. (C) 2020 Optical Society of America