Observation of superfluorescence and stimulated emission in Bi I after nonresonant two-photon pumping

We report the observation of superfluorescence and of stimulated emission in the near-infrared at 965.69 nm in atomic Bi. The atoms are prepared in the 6p²(³P₀)7p_3/2 upper state by nonresonant two-photon excitation. The cooperative character of the emission is demonstrated by the delay of the light pulses and their N² dependence upon the atomic density.