Phase reconstruction of strong-field excited systems by transient-absorption spectroscopy

TL;DR

This paper demonstrates a method to reconstruct quantum phases of atomic systems using transient-absorption spectroscopy, linking spectral features to quantum dynamics in strong-field interactions.

Contribution

It introduces a scheme to interpret how atomic phases are encoded in absorption spectra during pump-probe experiments, advancing towards full quantum phase reconstruction.

Findings

Experimental application to atomic Rb shows phase encoding in spectra.

Analysis relates quantum evolution to spectral absorption profiles.

Provides a pathway for quantum holography in strong-field physics.

Abstract

We study the evolution of a V-type three-level system, whose two resonances are coherently excited and coupled by two ultrashort laser pump and probe pulses, separated by a varying time delay. We relate the quantum dynamics of the excited multi-level system to the absorption spectrum of the transmitted probe pulse. In particular, by analyzing the quantum evolution of the system, we interpret how atomic phases are differently encoded in the time-delay-dependent spectral absorption profiles when the pump pulse either precedes or follows the probe pulse. We experimentally apply this scheme to atomic Rb, whose fine-structure-split $5s\,^2S_{1/2}\rightarrow 5p\,^2P_{1/2}$ and $5s\,^2S_{1/2}\rightarrow 5p\,^2P_{3/2}$ transitions are driven by the combined action of a pump pulse of variable intensity and a delayed probe pulse. The provided understanding of the relationship between quantum phases and absorption spectra represents an important step towards full time-dependent phase reconstruction (quantum holography) of bound-state wave-packets in strong-field light-matter interactions with atoms, molecules and solids.