Eight-wave mixing process in a Rydberg-dressing atomic ensemble.

We investigate the eight-wave mixing (EWM) process involving highly excited Rydberg states with the assistance of coexisting electromagnetically induced transparency (EIT) windows in a thermal 85Rb vapor both theoretically and experimentally. By use of a disturbance-free optical detection method, the Rydberg EWM characterized by multiple sets of spin coherence is presented via the interplay and competition between the dressing-state effects and excitation blockade caused by strong Rydberg-Rydberg interaction. Such interplay and competition can be demonstrated by the intensity evolutions of multi-wave mixing (MWM) signals via controlling the atomic density, the frequency detuning and Rabi frequencies of corresponding laser fields. The observed Rydberg EWM tailored by EIT windows can possess of much narrower linewidth <30MHz and provide a new way for the study of Rydberg effect in the atomic ensemble above room temperature.