Real-time ab initio description of the photon-echo mechanisms in extended systems: the case study of bulk GaAs

Abstract

In this paper we present an ab-initio real-time analysis of free polarization decay and photon echo in extended systems. As a prototype material, we study bulk GaAs driven by ultra-short laser pulses with a FWHM of 10 fs. We compute the electronic polarization P(t) and define a computational procedure to extract the echo signal. Results are obtained in both the low and high field regime, and compared with a two-levels system (TLS) model, with parameters extracted from the ab-initio simulations. An optimal agreement with the TLS is found in the low-field case, whereas some differences are observed in the high-field regime where the multi-band nature of GaAs becomes relevant.