Stabilization of Atoms in a Strong Laser Field

Mikhail Vladimirovich Fedorov

А. М. Попов, Olga V. Tikhonova, Ekaterina A. Volkova

Anna R. Dardia, Spencer Walker, Yifei Bai +3 more

Bound quantum states such as atoms can be torn apart by strong oscillating fields. A natural expectation is that stronger fields lead to more certain destruction. In contradiction to this intuition, some theories predict a striking reversal: that as the field intensity is raised above some threshold, bound state wavefunctions can spatially bifurcate and become increasingly stable with increasing field intensity. This ``strong field stabilization'' was predicted decades ago in the context of atoms in pulsed laser fields, but has resisted experimental observation due to extreme laser intensity requirements and theoretical controversy. We report the experimental observation of strong-field stabilization of a ground state, using trapped neutral atoms to emulate the dynamics of atomic electrons in an extremely strong laser field. We directly image the predicted wavepacket bifurcation, measure an ionization rate non-monotonic in field amplitude, and map out the regime of stabilization as a function of laser pulse parameters. We observe that stabilization persists down to surprisingly low drive frequencies, near and below the scale of the lowest-energy excitations of the bound state. These results confirm and extend a long-standing prediction of extreme quantum dynamics, and showcase a complementary tool for probing strong-field phenomena near and beyond the frontier of current laser technology.

Mikhail Vladimirovich Fedorov

The key subject of these lectures is Interference Stabilization (IS) of atoms in a strong laser field. Physics of the phenomenon, its various manifestations, as well as many related subtopics will be discussed. Generalizations to the case of two-colour interference stabilization will be briefly described. As it will be shown, owing to the achievable in this case very high degree of stabilization, the phenomenon appears to be very promising for making progress in such an important field as propagation of laser pulses in a gas medium. Since the first work on IS (Fedorov and Movsesian, 1988), there have been a lot of publications on this subject. I am not going to mention here all the relevant papers.

Nikolai B. Delone, В. П. Крайнов

V. S. Letkhov, Vladimir G. Minogin