A theoretical study of the interaction of intense terahertz transients and broadband optical pulses in quantum wells is presented. The approach is based on a numerical solution of the anisotropic semiconductor Bloch equations and includes, self-consistently, both continuum and excitonic effects. In the optical regime we recover the dynamic Franz–Keldysh effect showing THz sidebands in the optical absorption spectrum. In the THz regime we discern a series of harmonically generated upshifted THz transients. It is demonstrated pictorially that the upshifted transients are formed by the creation of highly anisotropic interfering, relative-motion electron–hole wave packets. We also investigate the influence of ellipticity of the driving field and chirped optical pulses. The field interaction with the quantum well is shown to be highly nonperturbative for typical free-electron laser fields. A series of propagating charge-carrier wave packets are analyzed, and a connection is made to analogies in the high-field physics of atomic ensembles.
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