Generating intense sub-half-cycle terahertz pulses
We developed a novel, flexible and scalable emitter of extremely asymmetric and intense terahertz field transients together with the groups of Dominique Bougeard (UR) and Mackillo Kira (University of Michigan) as well as collaborators from the Helmut Schmidt University and the Justus Liebig University Gießen. Making use of shift currents and local charging dynamics in asymmetrically coupled epitaxial semiconductor heterostructures, we generated waveforms exhibiting less than an oscillation half-cycle, peak fields above 1.1 kV cm-1 and spectra spanning into the mid-infrared, marking a milestone for next-generation high-repetition-rate (multi-)terahertz sources.
Press release (University of Michigan) in English
Press release (Mirage) in English
Press release (Laser Focus World) in English
The results have been published in Light: Science & Applications....
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In collaboration with the group of Ermin Malic (University of Marburg), we used ultrafast near-field microscopy to study the Mott transition of strongly-bound excitons in an atomically thin heterostructure of WSe2, unveiling pronounced nanoscale modulation in the dynamics of the transition. These findings underscore how nanoscale disorder plays a pivotal role in the dynamics of many-body phase transitions within a broad range of van der Waals materials.
Collaborating with partners from Germany, France, UK and Sweden we observed high-order terahertz nonlinearities directly in a free-running quantum cascade laser. With field-resolved two-dimensional spectroscopy we revealed up to eight-wave-mixing processes in a regime of negative absorption as well as the laser’s sub-cycle gain dynamics. High-order nonlinearities of this kind have the potential for various future applications, ranging from efficient intracavity frequency conversion and mode proliferation to passive mode locking.
