Microwave-induced three-photon coherence of Rydberg atomic states

• In this paper, we present a study of three-photon coherence (TPC) of Rydberg states in a ladder system where the upper transition is a microwave coupling between close lying Rydberg states for the 5S1/2(F=3)–5P3/2(F′=4)–50D5/2–51P3/2 transition of 85Rb atoms.
• The main results of the paper are numerically analyzed the spectral features of the Rydberg TPC from two viewpoints, Autler–Townes splitting (AT-splitting) of the Rydberg EIT and three-photon electromagnetically induced absorption (TPEIA).
• We determine the criterion to differentiate between AT-splitting of the Rydberg EIT and TPEIA in the Doppler-broadened ladder-type atomic system.
• We believe that our results contribute to an understanding of multi-photon coherence effects in the Rydberg states with microwave interactions.

We investigate the three-photon coherence (TPC) effects of the Rydberg state in a Doppler-broadened four-level ladder-type atomic system for the 5S1/2(F=3)–5P3/2(F′=4)–50D5/2–51P3/2 transition of 85Rb atoms. Upon interaction of the Rydberg Rb atom of the ladder-type electromagnetically induced transparency (EIT) scheme with a resonant microwave (MW) field, we numerically analyze the spectral features of the Rydberg TPC from two viewpoints, Autler–Townes splitting (AT-splitting) of the Rydberg EIT and three-photon electromagnetically induced absorption (TPEIA). We determine the criterion to differentiate between AT-splitting of the Rydberg EIT and TPEIA in the Doppler-broadened ladder-type atomic system.