Collective radiation effects in rubidium vapor beyond the yoked superradiance

It is known that being pumped with infrared light an ensemble of Rb atoms can demonstrate an upconversion and re-emit blue light at 420 nm. In pulsed regime this radiation can be enhanced by collective effects, which is called yoked superradiance. Here we demonstrate that not only the blue-light emission is affected by collective effects, but also the red light scattering. This becomes possible due to the coupling between different non-diagonal elements of the atomic density matrix. We develop a simple self-consistent model of the coupled atom-field system and numerically simulate its dynamics. We test the sensitivity of blue- and red-light pulse profiles on the density of Rb atoms and the background gas pressure.