Ultrafast nonlinear optical (NLO) technology combines femtosecond-resolved spectroscopy with nonlinear excitation to reveal how quantum nanomaterials respond under strong optical drive. By integrating broadband pump–probe and multiphoton excitation, I demonstrated that single-photon and multiphoton excitations share similar excited-state filling dynamics, and used this insight to develop a unified method for directly measuring absorption cross-sections from single- to high-order multiphoton regimes. This approach produces photon-order–resolved cross-section maps that greatly simplify the acquisition of key photon-harvesting metrics and accelerate materials optimization and discovery. Moving forward, I will both deepen methodological capabilities and apply them to fundamental studies of quasiparticles—excitons, phonons, and polaritons—under NLO states, with the aim of linking ultrafast mechanisms to rational design of materials for nonlinear optics, quantum photonics, and photon-harvesting technologies.

Calculated measurable σ_n boundaries (the vertical axis represents the logarithm of σ_n) and state-of-the-art σ_n of existing materials, demonstrating the universality of the developed measurement system.

Related Publications:
1. H. He, et al., Direct Determination of Multiphoton Absorption Cross-Sections by Transient Absorption Spectroscopy. Chem. Sci. 2025, Advance Article.
2. H. He, et al., Single Crystal Perovskite Microplate for High-Order Multiphoton Excitation. Small Methods 2019, 3, 1900396.