Dynamics of a Rabi oscillation under a pulsed perturbation

We study how a Rabi oscillation is affected by a periodic pulsed perturbation. Unlike a continuous perturbation, which simply shifts the resonance frequency, a pulsed perturbation splits the Rabi resonance into two lines separated by the pulse repetition rate. When the perturbation integrated over one pulse is equal to π, the resonance splits into two symmetrically placed lines at ± half the pulse repetition rate. When it is 2π, the Rabi oscillation is unaffected by the perturbation. We demonstrate these behaviors using the ground hyperfine transition of cesium atoms in a magneto-optical trap. The pulsed perturbation is introduced by a periodic magnetic field pulse. The 2π case is compared with the self-induced transparency, and its implications for optical frequency metrology using a pulsed optical trap is discussed.