Multiphoton pi pulses

Phys Rev Lett. 2002 Dec 23;89(26):263001. doi: 10.1103/PhysRevLett.89.263001. Epub 2002 Dec 9.

Abstract

Multiphoton excitation in a two-level system is exceedingly weak because of small multiphoton coupling strengths, large ac Stark shifts, and ionization. I will discuss a three-level system in which the ac Stark shift is greatly reduced and the multiphoton coupling strength is greatly enhanced over a two-level system, to such an extent that multiphoton pi pulses can be produced. I will also present two-electron calculations in a model potential, including ionization that shows a 12-photon pi pulse driven with 800-nm photons. This three-level configuration may provide the basis for an amplifying medium in the vacuum ultraviolet, as well as multiphoton adiabatic passage and innershell ionization.