Elimination of collisional dephasing by control laser fields

Arjun G. Yodh, J. E. Golub, THOMAS W. MOSSBERG

Arjun G. Yodh, J. E. Golub, THOMAS W. MOSSBERG

Anil K. Patnaik, Sukesh Roy, James R. Gord +2 more

A six-level model is developed and used to study the effects of collisional energy transfer and dephasing on electronic-resonance-enhanced coherent anti-Stokes Raman scattering (ERE-CARS) in nitric oxide. The model includes the three levels that are coherently coupled by the three applied lasers as well as three additional bath levels that enable inclusion of the effects of electronic quenching and rotational energy transfer. The density-matrix equations that describe the evolution of the relevant populations and coherences are presented. The parametric dependencies of the ERE-CARS signal on collisional energy transfer and dephasing processes are described in terms of both a steady-state analytical solution and the numerical solutions to the governing equations. In the weak-field limit, the ERE-CARS signal scales inversely with the square of the dephasing rates for the electronic and Raman coherences. In accord with published experimental observations [Roy et al., Appl. Phys. Lett. 89, 104105 (2006)], the ERE-CARS signal is shown to be insensitive to the collisional quenching rate. Parametric dependencies on quenching, rotational energy transfer, and pure electronic dephasing are presented, demonstrating reduced collisional dependence for saturating laser fields.

Shuwu Xu, Lingxiao Wang, Haizhi Fang +2 more

Suppressing molecular alignment dephasing is of significant practical value for applications involving nonrigid rotors. In this work, we propose a strategy that employs a train of time-delayed, phase-modulated laser pulses to achieve the elimination of alignment dephasing over an extended temporal window. Our findings demonstrate that for molecules with short rotational periods, such as CO or N 2 used in this study, dephasing can be completely eliminated for at least a dozen revival periods, thereby restoring alignment approaching the rigid-rotor limit. For molecules exhibiting longer revival periods, however, the effectiveness of this approach is somewhat diminished. While complete dephasing elimination is not achieved in such cases, the method remains sufficiently effective for most practical applications. We also qualitatively analyze the underlying reasons for the reduced performance in molecules with longer rotational periods.

Arturo Bambini, P. R. Berman, Roberto Buffa +2 more

Paul W. Brumer