Temporal Evolution Kinetics of Upconversion Population Distribution Resulting in Transient Luminescence Enhancement

Upconversion (UC), which enables nonlinear anti‐Stokes emission, exhibits significant potential in fields such as in vivo imaging, optical storage, and computing. However, the transient luminescent kinetics of UC remain underexplored in existing work, thereby hindering practical applications that demand rapid response and high luminescence intensity. To address these challenges, this work reveals upconversion luminescence (UCL) nanosecond kinetics by using spatially and temporally synchronized 808, 976, and 1530 nm ns‐pulsed lasers to excite the same NaYF 4 :Er 3 ⁺ (60 mol%) upconversion nanoparticles (UCNPs). According to experimental results in self‐sensitization upconversion (SSU) processes, the spectral‐temporal resolved UCLs indicate that electron transition pathways are manipulated by the original population distribution. This distribution is established by exogenous wavelength‐dependent excitation, and then its subsequent evolution can be exploited to couple with transition processes to increase transient UCLs. Based on this mechanism, the present work achieves a 10‐fold enhancement for transient UCL at the 540 nm emission band via dual ns‐pulsed combined excitation with 808+1530 nm. The enhancement factor is state‐of‐the‐art in the area of luminescence boost, which only relies on exogenous excitation. This study offers an advanced approach to satisfy fast but bright‐luminescent reequipments in applications including optical storage, optical switching, and biomedical imaging.