Fig. 2: Power-dependent UC-SF spectra and decay curves of 100Nd@Y UCNPs.
From: Ultrafast upconversion superfluorescence with a sub-2.5 ns lifetime at room temperature
a UC-SF spectra and (b) decay curves (λem = 588 nm) of 100Nd@Y UCNPs upon fs-pulsed laser excitation at 800 nm with different power densities. The inset in (b) shows the UC-SF image of the UCNP assemblies. c Power-dependent UC-SF decay curves (λem = 588 nm) of 100Nd@Y UCNPs at the initial stage, showing the decreased delay time with increasing the excitation power density. d The delay time (τD) and radiative decay time (τR) of Nd3+ at 588 nm as a function of excitation power density. e Schematic of the SF dynamics of the collective N-atom SF system based on the Dicke model.
