Rostock 2019 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 23: Photonics I
Q 23.4: Vortrag
Montag, 11. März 2019, 17:00–17:15, S Ex 04 E-Tech
Sub-cycle 2D spectroscopy of terahertz intersubband saturable absorbers — •Jürgen Raab1, Christoph Lange1, Jessica Boland1, Enrico Dardanis2, Nils Dessmann2, Lianhe Li3, Edmund Linfield3, Giles Davies3, Miriam Vitiello2, and Rupert Huber1 — 1Department of Physics, University of Regensburg, 93040 Regensburg, Germany — 2NEST, CNR-Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, Pisa I- 56127, Italy — 3School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, UK
Intersubband transitions are promising candidates for terahertz (THz) saturable absorbers, a key ingredient for future passively mode-locked quantum cascade lasers. Here we investigate the saturation dynamics of semiconductor quantum well structures by field resolved 2D THz spectroscopy, which allows us to distinguish between incoherent pump-probe and coherent four-wave mixing signals, on a sub-cycle time scale. These nonlinearities peak at a THz field amplitude of 11 kV/cm and decrease for higher fields, due to THz-driven carrier-wave Rabi flopping. With a microscopic model based on a numerical solution of the Maxwell-Bloch equations, we can quantitatively reproduce our experimental findings and trace the trajectory of the Bloch vector. This theory allows us to design tailored semiconductor structures with optimized dynamical properties for saturable absorbers that could be used in future compact semiconductor-based single-cycle THz sources.