Rydberg Raman Ramsey EIT

Rydberg states of atoms are interesting because of their high electric susceptibility that enable their potential application in sensitive electric field sensors. Electromagnetically induced transparency (EIT) – a two-photon transmission peak induced by interaction of two counter-propagating optical fields at 780 nm and 480 nm – provides easy optical readout, as the change in optical transmission is determined by the applied electric field. However, the sensitivity of such optical detectors is limited by the spectral width of the EIT peak, which in the thermal vapor is limited by the two-photon Doppler broadening to approx 5 MHz. Here we theoretically investigate the possibility to reduce the sensor response by reducing the resonance width using a Ramsey interrogation. Two spatially separated EIT channels create a Ramsey sequence where the atomic Rydberg coherence is prepared in the first region, evolves with no applied optical fields as atoms cross the region between the two channels , and then is probed in the second channel. We show that the linewidth of such Raman-Ramsey fringe can be theoretically reduced to 50 kHz with room temperature Rydberg atoms. This theoretical work suggests a potential solution to have a narrow EIT feature with reduced power broadening that can be potentially beneficial for boosting the sensitivity of EIT-based Rydberg electrometers.