Phase control of a two-photon transition with shaped femtosecond laser-pulse sequences

Abstract

Phase effects in a quantum control experiment on the two-photon transition $4s\phantom{\rule{0.3em}{0ex}}\ensuremath{\leftarrow}\ensuremath{\leftarrow}\phantom{\rule{0.3em}{0ex}}3s$ of atomic sodium are studied. In our experiment, we combine the generation of phase-locked interferometrically generated pulses with pulse-shaping techniques to study in detail the interplay of optical and quantum-mechanical phases. Subtle differences in the physical realization of the pulse sequences produce large difference in the control objective---the $4s$ population. The control mechanisms of more complex pulse sequences generated by periodic and discontinuous phase-modulation functions are investigated systematically and analyzed on the basis of quantum-mechanical interference.