Ultrafast nonlinear optical effects in semiconductor quantum wells resonantly driven by few-cycle Terahertz pulses

摘要

The exciton binding energy in GaAs-based quantum-well (QW) structures is in the range of ~10 meV, which falls in the terahertz (THz) regime. THz-induced nonlinear optical effects of excitons in QWs are of great interest because they provide new insights into the quantum coherence and wavepacket dynamics in semiconductors. For example, an experiment/theory study demonstrated that strong single-cycle THz pulses induce coherent extreme-nonlinear optical transients in semiconductor QWs, where the rotating wave approximation breaks down and the ponderomotive effects become prominent [1]. We have conducted a time-resolved study to observe the resonant interactions of strong narrowband THz pulses with coherent excitons in QWs, where the THz radiation is tuned near the 1s-2p excitonic transition and the THz pulse duration (~3 ps) is comparable with the exciton dephasing time.