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

Intraexciton transitions in semiconductor quantum wells are modulated by strong and tunable few-cycle terahertz pulses. Time-resolved terahertz-pump and optical-probe measurements demonstrate that the 1s heavy-hole and light-hole exciton resonances undergo large-amplitude spectral modulations when the terahertz radiation is tuned near the 1s–2p intraexciton transition. The strong nonlinear optical transients exhibit the characteristics of Rabi sidebands. The spectral features also reveal the dephasing properties of the optically dark 2p states. A microscopic theory shows that the 2p-dephasing rate is three times that of the 1s-state. The ultrafast nonlinear optical effects and their quantum nature suggest promising applications to ultrahigh-speed optical signal processing and quantum information processing in the THz region.