Coherent Interband and Intersubband Dynamics in Terahertz-DrivenGaAs Quantum Wells**The project supported by the NationalFund for Distinguished YoungScholars of China under Grant No. 60425415, the Major Project of theNational Natural Science Foundation of China under Grant No. 10390162, theSpecial Funds for Major State Basic Research of China under GrantNo. G20000683, the Shanghai Municipal Commission of Scienceand Technology under Grant No. 03JC14082

Abstract

We theoretically investigate the optical absorption spectra andcharge density by subjecting a GaAs quantum well to both an intense terahertz(THz)-frequency driving field and an optical pulse within the theory ofdensity matrix. In presence of a strong THz field, the optical transitions inquantum well subbands are altered by the THz field.The alteration has a direct impacton the optical absorption and the charge density. The excitonic peak splittingand THz optical sideband in the absorption spectra show up when changing theTHz field intensity and/or frequency. The Autler–Towns splitting is a resultfrom the THz nonlinear dynamics of confined excitons. On the other hand, thecarrier charge density is created as wave packets formed by coherentsuperposition of several eigenstates. The charge density exhibits quantumbeats for short pulses and/or wider wells and is modulated by the THz field.