Nonlinear optical processes driven by superfluorescent fields and their controllability with external laser fields

We investigated nonlinear optical processes driven by superfluorescent (SF) fields and their controllability with external laser fields. Cesium atoms were excited from the $6S$ ground state to the $8P$ state by a femtosecond laser pulse. The cascaded SF decay, $8P\ensuremath{\rightarrow}8S\ensuremath{\rightarrow}7P$, created coherence between the $7P$ and ground states, and led to the emission of a 455-nm pulse. A nanosecond laser pulse was applied to switch the $8S\ensuremath{\rightarrow}7P$ transition to the $8S\ensuremath{\rightarrow}6P$ one and newly generate an 852-nm pulse. At the same time, the nanosecond pulse suppressed the 852-nm emission through the inhibition of the development of the SF field between the $8P$ and $8S$ states, which led to the saturation of the 852-nm power with the increase of the nanosecond pulse power. The presented results offer an approach to investigate cooperative radiation processes in many-body systems and to develop an alternate light source.