[Seminar] Dr. Daniel Siebadji "Broadband UV Pump–Probe Spectroscopy with Supercontinuum Probing: Exciton, Biexciton Dynamics and Spin Implications in ZnO Quantum Wells"

Speaker

Dr. Daniel Siebadji / University of Strasbourg, France

Daniel Siebadji has a PhD in nanophysics from the University of Strasbourg, specializing in ultrafast spectroscopy of wide-bandgap quantum wells. His research explores exciton and biexciton dynamics and their implications for spintronic applications in ZnO-based heterostructures.

Title

Broadband UV Pump–Probe Spectroscopy with Supercontinuum Probing: Exciton, Biexciton Dynamics and Spin Implications in ZnO Quantum Wells

Abstract

Understanding ultrafast carrier dynamics in wide-bandgap quantum wells is essential for advancing next-generation optoelectronic and spintronic devices. In this talk, I will present the design and implementation of a broadband ultraviolet non-degenerate pump–probe setup that combines a 266 nm pump with a supercontinuum probe spanning 340–400 nm. This approach enables simultaneous monitoring of carrier dynamics across multiple timescales, from sub-100 fs to ns, in ZnO/ZnMgO quantum wells. Using this technique, we track the rapid capture of carriers into the well, sub-picosecond exciton formation and thermalization, and the subsequent localization driven by interface disorder. We also identify biexciton formation through photoinduced absorption, extracting binding energies of 18–22 meV, and observe phonon-assisted exciton creation processes. These findings reveal that while strong Coulomb interactions stabilize excitonic complexes, they also enhance exchange-driven spin depolarization and introduce leakage pathways that limit spin injection efficiency.