A research team led by Professor Liu Xiaoze from the School of Physics and Technology at Wuhan University has made a significant advancement in nonlinear optics.

Their pioneering study on phonon-assisted upconversion mechanisms has been published in the esteemed journal Science Advances. The paper, titled "Giant single-step upconversion via sub–35-fs phonon dynamics in the nonlinear optical regime", represents a major leap forward in the understanding and application of upconversion processes.

The team has demonstrated a novel mechanism of coupling organic phonon vibrations with inorganic excitons. This breakthrough has enabled the realization of a single-step upconversion energy of approximately 200 meV in the nonlinear regime, with a time scale of less than 35 femtoseconds — approaching the phonon-dynamic limit of about 23 femtoseconds.

The study employed steady-state spectroscopy, transient absorption spectroscopy, and phonon characteristic analysis to reveal the unique electron-phonon coupling between organic vibrations and inorganic lattice excitons in two-dimensional hybrid perovskites.

The main findings of the research include:

Giant single-step upconversion energy: By harnessing the resonant vibration of organic ligand molecules, the team achieved single-step electro-phonon coupling, resulting in energy upconversion exceeding 200 meV and dynamics within 35 fs.

Collaborative upconversion in both linear and nonlinear regimes: The synergy between single-step upconversion and two-photon absorption (TPA) has been observed in the nonlinear regime for the first time.

Applications in high-resolution imaging: This research facilitates high-resolution infrared imaging applications by utilizing an innovative UC mechanism, termed TP-ASPL.