Figure 4: Excitation intensity dependence of the CEP film.
From: Experimental demonstration of photon upconversion via cooperative energy pooling
(a) Log-log plot of upconverted emission from the CEP film at 440±20 nm as a function of 540 nm excitation intensity. The coloured lines are quadratic (blue) and linear (red) fits to the first and last three data points, respectively. The green line is a fit to the CEP kinetic model, discussed below. Excitation-induced film degradation precluded the collection of data at higher excitation intensities. The inset shows the same figure but scaled linearly. (b) Instantaneous power-law dependence of measured and modelled excitation dependence curves, showing a progression toward linear power-law dependence at higher excitation intensities. The power-law dependence was determined by the slope of a linear fit to a sliding boxcar window of six data points from the log–log plot of intensity dependence in a.
