Fewcycle excitation of atomic coherence: an analytical solution beyond the rotatingwave approximation
Abstract
Developing an analytical theory for atomic coherence driven by ultrashort laser pulses has proved to be challenging due to the breakdown of the rotating wave approximation (RWA). In this paper, we present an approximate analytical solution that describes a twolevel atom under the excitation of a faroffresonance, fewcycle pulse of arbitrary shape without invoking the RWA. As an example of its applicability, a closedform solution for Gaussian pulses is explicitly given, and the result is used to analyse the impact of carrier envelope phase on atomic population ratios. Comparisons with numerical solutions validate the accuracy our solution within the scope of the approximation. Finally, we outline an alternative approach that can lead to a more accurate solution by capturing the nonlinear behaviors of the system. The work lays out feasible theoretical paths toward analytically describing twolevel atoms driven by ultrashort pulses.
 Publication:

Journal of Physics Communications
 Pub Date:
 July 2022
 DOI:
 10.1088/23996528/ac7eaf
 arXiv:
 arXiv:2111.13965
 Bibcode:
 2022JPhCo...6g5005P
 Keywords:

 quantum coherence;
 twolevel system;
 fewcycle pulses;
 rotating wave approximation;
 Schrödinger equation;
 analytical solution;
 Quantum Physics;
 Physics  Optics