Strong light-matter coupling: coherent parametric interactions under cavity and free-space conditions

This paper presents a theoretical and experimental study of coherent interaction between laser pulses and a dense ensemble of resonant atoms both in a cavity and free-space. The experiments are carried out in a plasma of pulsed and dc neon discharges. It contains a considerable amount (up to 10¹³ cm^-3) of neon atoms at the metastable level, which is used as a lower state of a resonant optically dense medium without population inversion under analysis.