Strong-field effects in Rabi oscillations between a single state and a superposition of states

TL;DR

This paper investigates how broadband femtosecond laser pulses induce Rabi oscillations between a ground state and a superposition of excited states, revealing complex phase dependencies influenced by strong-field effects.

Contribution

It demonstrates the occurrence of Rabi oscillations involving superpositions of states driven by broadband pulses and provides a theoretical model explaining the observed phenomena.

Findings

Wavepacket phase depends intricately on laser intensity

Strong-field effects significantly influence Rabi oscillations

Experimental results align with numerical simulations

Abstract

Rabi oscillations of quantum population are known to occur in two-level systems driven by spectrally narrow laser fields. In this work we study Rabi oscillations induced by shaped broadband femtosecond laser pulses. Due to the broad spectral width of the driving field, the oscillations are initiated between a ground state and a coherent superposition of excited states, or a "wavepacket", rather than a single excited state. Our experiments reveal an intricate dependence of the wavepacket phase on the intensity of laser field. We confirm numerically that the effect is associated with the strong-field nature of the interaction, and provide a qualitative picture by invoking a simple theoretical model.