The Autler-Townes Effect Revisited

Yu Bai

Arnoldas Seputis

In this thesis the effect of Autler-Townes splitting is revisited and the dynamics of a 2- and 3-level quantum systems, exhibiting this effect, is studied. This effect is a special case of the Stark effect, where the spectral lines of an atom are modified due to an external driving electromagnetic field. Two different articles, describing the Autler-Townes splitting, are studied, where one solves the time-dependent equations of the semi-classical model and the other studies the time-independent Hamiltonian for the system, which is described completely quantum mechanically. In our work, we proceed by employing the semi-classical model but transforming the Hamiltonian into a time-independent form, which makes the model easier to study. Subsequently, we also study the atom as an open quantum system and investigate the effect that the decay of an atom to a vacuum field has on the Autler-Townes splitting. Throughout the thesis, we present the density matrices, and hence the time-evolution of the dynamics, in the Bloch-vector description in an attempt to understand the geometrical nature of the dynamics and, in effect, the Autler-Townes phenomenon.

William George Unruh

Sajid Qamar, Shi-Yao Zhu, Muhammad Suhail Zubairy

Autler–Townes spontaneous emission spectroscopy is revisited for a time-dependent case. We report the results of spontaneous emission spectra for nonstationary scattered light signals using the definition of the time-dependent physical spectrum. This is a rare example of problems where time-dependent spectra can be calculated exactly.

Pierre Meystre

Ayoub Ait Elarabi, András Csehi

Recent studies have shown that both Rabi oscillations (ROs) and dynamic interference (DI) lead to pronounced multipeak patterns in the spectrum of ionized photoelectrons. These two prominent dynamical effects---characteristic of intense, short, and (near-)resonant laser pulses interacting with matter---usually coexist, and are thus hard to distinguish. Here, we revisit the multipeak pattern of the Autler-Townes doublet to uncover its physical origin, by calculating the photoelectron spectrum accurately. Our joint analytical and numerical analysis reveals that selectively populating the two emerging dynamically dressed states is key to an efficient balancing between ROs and DI. We demonstrate physical situations where either ROs or DI dictate the spectrum shape, and explore the transition between these regimes. The present work provides further insight into our results reported in a previous work [Phys. Rev. A 108, L061101 (2023)].