Quantum Control

Two photon absorption in strong field

A shaped ultrafast pulse makes it possible to stir a quantum system and thus control a quantum process via light-matter interaction. Two photon absorption(TPA) process in two-level atoms is one of the good testbed for coherent control. We study coherent control schemes for a TPA process in a strong field. For a optimal coherent scheme to enhance TPA, strong field effects(dynamic Stark shift) have been considered.

Fig.1: schematic diagram of the experimental setup

In weak field reigme, a transform-limited pulse is a optimal pulse to enhance a TPA. But it is not a optimal solution in strong field. The dynamic Stark shift disturbs a TPA process.

Fig.2: fluoresence as a function of chirp rates and transform-limited intensity of pulses

A linear chirped pulse is more optimal than a transform-limited pulse.

Fig.3: fluorescence as a function of detuning and chirp rates