Measuring magnetic field inside a microwave cavity via Rabi resonances   in Cs atoms
  We present a technique for measuring microwave (MW) field based on Rabi resonances induced by the interaction of atoms with a phase-modulated MW field. A theoretical model of field measurement is used to calculate Rabi frequency. Single-peak feature of the measurement model makes the technique a valuable tool for simple and fast field measurement. As an example, we use the technique to determine the MW field strength inside a Cs vapor cell in the X-band rectangular cavity for applied power in the range of -21 dBm to 20 dBm. The results show that this proposed technique is capable for detecting the field over a broad dynamical range. 
Fuyu Sun, Dong Hou, Qingsong Bai, Xianhe Huang, Jie Ma, and Xiaofeng   Li
physics.atom-ph