Observations of ultrafast superfluorescent beatings in a cesium atomic vapor excited by femtosecond laser pulses

Abstract

Picosecond and femtosecond superfluorescent beatings are observed from a dense atomic vapor. Cesium atoms are excited by femtosecond laser pulses via two-photon processes into their coherent superpositions of the ground 6S and excited 8S states. The yoked superfluorescent blue light at lower transitions of 6S – 7P is recorded and studied. Delayed buildup time of this blue light is measured as a function of the input laser beam power using a high-resolution 2 ps streak camera. At low power and density, a beating with a period of approximately 100 picoseconds is observed as we believe that represents the ground state splitting. The autocorrelation measurements of the generated blue light exhibit a beating with a quasi-period of 200 ± 60 fs corresponding to the splitting of the 7P level. Our experimental observations may hold a promising direction for investigation of cooperative radiation in many-body systems including solid-state materials.