GTIIT-STU Optics Seminar
Title: Strong-Field Quantum Coherence Effect in Molecular Ion
Speaker: Hongbin Lei
Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences
Abstract
Manipulating light–matter interactions play a fundamental role across multiple cutting-edge disciplines, not only enabling control over macroscopic material properties but also facilitating the development of state‑of‑the‑art light sources. Generally, two fundamental approaches are employed to control these interactions: quantum optics and strong‑field physics. The quantum optical approach relies on resonant excitation between matter and laser, focusing on statistical characteristics and quantum properties of photon. In contrast, the strong‑field approach uses ultrashort intense laser pulses to interact with a medium, where electron dynamics involving hundreds of photons can be understood in terms of semiclassical trajectories and scattering models. Over the past decades, few studies have bridged these two fields due to fundamental differences in the systems studied and the laser parameters employed.
However, molecular ions prepared by ultrashort intense femtosecond laser pulses offer a unique nonequilibrium quantum system: they are naturally shielded from collision‑induced decoherence on picosecond timescales and can maintain strong quantum coherence during the laser interaction. Moreover, molecular ions possess rich vibrational‑rotational level structures with energy interval in the ultraviolet range, can withstand high laser intensities without destruction of structure, and producing high‑order nonlinear responses. These features provide an unprecedented opportunity to explore quantum optical phenomena within the strong‑field regime.
When quantum optics meets strong‑field physics in molecular ions, new phenomena and mechanisms emerge. This talk, focusing on quantum coherence effects of ions in strong fields and taking nitrogen molecular ions prepared and driven by intense lasers as an example, will reveal the role of rotational quantum coherence in coherent ion radiation, discover an efficient photoexcitation mechanism in ion system, and propose a novel scheme for generating ultraviolet supercontinuum radiation driven by strong field quantum coherence in molecular ions.
About the Speaker:
Dr. Hongbin LEI received his Bachelor of Engineering degree from Lanzhou University in 2019, followed by a MSc in Physics in 2021 and a Ph.D. in Physics in 2025 from National University of Defense Technology (NUDT), under the supervision of Prof. Zengxiu Zhao. During his studies, he was awarded the National Scholarship twice, and recognized as a “Deya Student” honor of NUDT. His research focuses on strong-field quantum coherence effect in molecular ion, with 16 academic papers published in journals such as Nature Communications, Physical Review Letters, Physical Review Research, and Photonics Research, including 7 papers as first author or co-first author.