Two-photon processes with chirped laser pulses

Zhaopeng Sun, Jing Han, Wenkai Zhao +2 more

Abstract The effects of pulse chirping on the excitation and ionization process in hydrogen atoms are theoretically investigated by numerically solving the full time-dependent Schrödinger equation with a pseudospectral method. We specifically compare the dynamical results of single-photon resonant ionization (SRI) and two-photon resonant ionization (TRI) across laser intensities ranging from 10 12 to 10 14 W cm 2 . The ionization probabilities of SRI and TRI tend to exhibit opposite chirp dependent behaviors as the laser field changes from weak to strong, which are elucidated with the strong field approximation theory. Furthermore, the sensitivity of ionization probability to chirp can be suppressed at specific laser intensities when the laser field is synthesized by two-color resonant chirped pulses. Our study provides a basis for theoretical investigations into chirp effect on atomic photoionization, offering new insights into the coherent control of electron dynamics.

R. Stephen Berry

Y. B. Band, O. Magnes

We study the dynamics of chirped adiabatic passage (CHIRAP) with temporally delayed pulses to selectively and fully transfer population in atoms and molecules. We show that the transfer of population via stimulated Raman adiabatic passage (STIRAP) and stimulated two-photon adiabatic absorption with temporally delayed laser pulses is not adversely affected by applying a chirp to the pulses, provided the intensity of the laser is sufficiently large to allow adiabatic passage. We then proceed to consider systems in which a near degeneracy of terminal state levels results in nonselective population of the terminal levels using nonchirped STIRAP or two-photon absorption stimulated passage, because the dynamics within the nearly degenerate pair of levels is not adiabatic. However, the CHIRAP process selectively populates only one of the terminal levels.

Guy Mayer, J. Sevin

Minhua Zhang

Based on the second-order perturbation theory,the two-photon processes in the atom system excited by a shaped chirped-pulse are analyzed.The evolution of the two-photon transition probability is studied under the two cases of non-resonance and resonance.It′s shown that the transition probabilities disappeared at some corresponding frequencies under the non-resonance case,and thus the laser pulse can get through the medium without loss. Meanwhile,the maximum two-photon transition probability is obtained by choosing the best shaping function under the resonance case.