Sublevel echoes selectively excited by light-pulse trains: synchronized-quantum-beat echoes

Abstract

We report on a new type of sublevel echoes, synchronized-quantum-beat (SQB) echoes, generated by a successive application of two resonant light-pulse trains. The echoes are selectively generated for a sublevel pair whose frequency splitting is equal to an integral multiple of the repetition frequency of the light pulses. By using mode-locked laser pulses tuned to the D₁ transition, we observed SQB echoes (and free induction decay) for all Zeeman and hyperfine transitions in the ground state of sodium atoms in low magnetic fields.