Quasienergy Spectroscopy of Excitons

TL;DR

This paper theoretically investigates the nonlinear optical response of excitons under intense THz radiation, revealing complex spectral features linked to quasienergy structures and avoided crossings.

Contribution

It introduces a transparent expression for susceptibility and connects spectral features to quasienergy spectra, advancing understanding of exciton behavior under strong fields.

Findings

Rich spectral structures due to quasienergy crossings

Resonantly enhanced nonlinear sidebands

Direct manifestation of avoided crossings in spectra

Abstract

We theoretically study nonlinear optics of excitons under intense THz irradiation. In particular, the linear near infrared absorption and resonantly enhanced nonlinear sideband generation are described. We predict a rich structure in the spectra which can be interpreted in terms of the quasienergy spectrum of the exciton, via a remarkably transparent expression for the susceptibility, and show that the effects of strongly avoided quasienergy crossings manifest themselves directly, both in the absorption and transmitted sidebands.