Magnetometry using sodium fluorescence with synchronous modulation of two resonant light fields

We report a new technique to observe magneto-optical resonance with synchronous modulation of two resonant light fields. The resonance is created through coherent population trapping (CPT) by virtue of Raman excitation due to resonant light fields. Due to higher resonance amplitude at longer light duty cycle close to 50%, the magnetic field sensitivity is improved in comparison to the conventional single resonant beam case. We achieve an average magnetic field sensitivity of 41 pT Hz-1/2 for duty cycle ranging between 35% to 10%. We have developed a theoretical model based on density matrix equations to verify our experimental observations. This technique could be used in remote magnetometry with mesospheric sodium for improving the sensitivity in geomagnetic field measurement.