Multiphoton atomic ionization with ultra-short laser pulses

Andre Charles Adler

Rutger B. Vrijen, Lambertus D. Noordam

王培杰, 方炎

Louis A. Lompre, G. Mainfray, C. Manus +1 more

This paper reports the four-photon ionization of caesium atoms when the laser frequency is tuned through the resonant three-photon transition 6S → 6F. This experiment was performed by using a tunable-wavelength bandwidth-limited subnanosecond laser pulse at 1.06 μm, in the 108-109 W.cm-2 laser intensity range. Pulse widths of 1.5 ns, 50 ps, and 15 ps were used. The resonant character of the multiphoton ionization process was observed, even with the shortest pulse of 15 ps. Nevertheless the influence of a temporal effect is demonstrated according to theoretical predictions. The resonance shift ΔE of the 6S → 6F transition energy was found to be linear with the laser intensity I within the range 108-109 W.cm-2. ΔE = α I, with α = 2 cm-1/GW.cm-2. This result confirms previous measurements performed with single-mode 35 ns laser pulses and is in very good agreement with calculated resonance shifts.

Gerd Leuchs

George N. Gibson, Richard R. Freeman, Thomas J. Mcilrath

We investigate the relative importance of resonant enhancement and real population transfer in short-pulse multiphoton ionization. Total ionization and excited state population after the laser pulse are calculated numerically by integrating the time dependent Schödinger for a two level atom in a short-pulse high-intensity laser field.