• DOI:10.1364/OE.27.002248
• Corpus ID: 73417385

Ultrafast two-dimensional field spectroscopy of terahertz intersubband saturable absorbers.

@article{Raab2019UltrafastTF,
  title={Ultrafast two-dimensional field spectroscopy of terahertz intersubband saturable absorbers.},
  author={J{\"u}rgen Raab and Christoph Lange and Jessica L. Boland and Ignaz Laepple and Martin Furthmeier and Enrico Dardanis and N. De{\ss}mann and Lianhe Li and Edmund Harold Linfield and A. Giles Davies and Miriam Serena Vitiello and Rupert Huber},
  journal={Optics express},
  year={2019},
  volume={27 3},
  pages={
          2248-2257
        }
}

• J. Raab, C. Lange, +9 authors R. Huber
• Published 25 January 2019
• Physics
• Optics express

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. Clear signatures of incoherent pump-probe and coherent four-wave mixing signals are recorded as a function of the peak electric field of the single-cycle THz pulses. All nonlinear signals reach a pronounced maximum for a THz electric field amplitude of 11 kV/cm and decrease for higher fields. We demonstrate that this behavior is a fingerprint of THz-driven carrier-wave Rabi flopping. A numerical solution of the Maxwell-Bloch equations reproduces our experimental findings quantitatively and traces the trajectory of the Bloch vector. This 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.