Linear optical absorption spectra of mesoscopic structures in intense THz fields: free particle properties

TL;DR

This paper develops a theoretical framework using non-equilibrium Green functions to analyze how intense THz fields affect the optical absorption spectra of mesoscopic semiconductor structures, revealing phenomena like blue-shifts, sidebands, and dynamical localization effects.

Contribution

It introduces a comprehensive theoretical approach to study the impact of THz radiation on optical spectra of mesoscopic structures, including analytical predictions of dynamical localization effects.

Findings

Blue-shift and sidebands in bulk-like structures due to THz fields

Appearance of stable steps in superlattice absorption spectra

Prediction of dynamical localization effects in superlattices

Abstract

We theoretically study the effect of THz radiation on the linear optical absorption spectra of semiconductor structures. A general theoretical framework, based on non-equilibrium Green functions, is formulated, and applied to the calculation of linear optical absorption spectrum for several non-equilibrium mesoscopic structures. We show that a blue-shift occurs and sidebands appear in bulk-like structures, i.e., the dynamical Franz-Keldysh effect [A.-P. Jauho and K. Johnsen, Phys. Rev. Lett. 76, 4576 (1996)]. An analytic calculation leads to the prediction that in the case of superlattices distinct stable steps appear in the absorption spectrum when conditions for dynamical localization are met.