Characterization of a Far-Field Microwave Magnetic Field Strength Sensor Based on Double Radiooptical Resonance

We experimentally investigated the resonance interaction of laser and microwave fields with $^{133}$Cs atomic gas in far-field and free-space conditions. The observed double radiooptical resonance (DROR) on the D$_2$ line of Cs atoms was used as a novel-type field sensor, based on the laser spectroscopy technique, for the detection and investigation of the time-varying magnetic field. The effects of the Cs cell length, both laser and microwave powers, and their polarizations to the changing amplitude of the DROR signal were investigated. Almost linear dependencies of the DROR signal amplitude with both laser and microwave powers have been observed. The splitting of DROR signal under a constant magnetic field was detected. The time response of the sensor system was investigated under pulsed microwave. The amplitude fluctuation of the microwave magnetic field was measured using the DROR signal and the isotropic probe simultaneously. The stability of amplitude fluctuations of the microwave field with time was analyzed by using Allan variance statistics.