Dual-wavelength nanosecond pulsed excitation for enhanced upconversion luminescence and fast imaging

Upconversion (UC) enables anti-Stokes emission with promising applications in bioimaging, optical storage, and computing. Nevertheless, the transient luminescence enhancement of UC remains insufficiently explored, limiting its use in applications requiring high-speed and intensity. In this work, we investigate nanosecond UCL kinetics in high-doped NaYF4: Er3+ (60 mol%) nanoparticles using spatially and temporally synchronized 808 and 1530 nm ns-pulsed lasers, which demonstrate that dual-wavelength excitation (simultaneous excitation at 808 nm and 1530 nm) promotes electron population coupling at the 4I9/2 energy level, resulting in a 10-fold enhancement of transient UCL at 540 nm. This strategy facilitates imaging of fast-moving objects with micron-sized light sources and reduces the demands on camera performance. Our approach offers significant potential for optical switching, data storage, and bioimaging applications.