Photoluminescence spectroscopy of rare earth doped materials: Why measure at the quantum limit?

Ultra-broadband near-infrared upconversion for solar energy harvesting

“…In both configurations, the UCPL from the surface of the sample at variable solar concentration (Fig. S2) was detected with minimal reabsorption, as in prior fluorescence measurements [51], [52]. The difference in the collection efficiency of the two optical systems resulted in different integrated UCPL intensities.…”