Ultrafast two-dimensional field spectroscopy of terahertz intersubband saturable absorbers

Intersubband (ISB) transitions in semiconductor multi-quantum well (MQW) structures
are promising candidates for the development of saturable absorbers at terahertz (THz)
frequencies. Here, we exploit amplitude and phase-resolved two-dimensional (2D) THz spectroscopy on the sub-cycle time scale, to observe directly the saturation dynamics and coherent control of ISB transitions in a metal-insulator MQW structure. We demonstrate that this behavior is a fingerprint of THz-driven carrier-wave Rabi flopping. A microscopic model allows us to design tailored MQW structures with optimized dynamical properties for saturable absorbers that could be used in future compact semiconductor-based single-cycle THz sources.

The publication can be found here here