Observation of superradiance in Rb vapour

Using laser excitation of the 6 2 P levels in the natural isotopic mixture of Rb atoms, modulation of superradiance intensity from some transitions to the lower levels was observed. On the transition 6 2 P 1/2 -6 2 S 1/2 this effect is interpreted as a quantum beat between the hyperfine-structure transitions of the Rb 85 and Rb 87 isotopes. A nearly 'single-pulse' superradiant signal was obtained on the 6 2 P-4 2 D transitions. When a magnetic field was applied transverse to the direction of the laser beam, the pulses obtained showed the properties forecast by two-level superradiance theory. Preliminary results are reported.