Laser induced broadband Vis and NIR emission from Yb:YAG nanopowders

What is it about?

The laser induced broadband emission (LIBE) of (YbxY1−x)3Al5O12 nanocrystals was investigated in vacuum using the focused infrared laser beam. The samples were prepared via Pechini's technique. The different shapes of LIBE spectra were observed. The LIBE characteristics including an order of the process, rise and decay times, were independent on the type of emission spectra and concentration of Yb3+ ions. Intensity of the emission spectra decreased/increased with time after switching off/on the laser excitation, while the shape of the emission spectra remained approximately the same. This is consistent with the colour of the emission, which remains white even after significant decrease in intensity. For the first time, the generation of broadband emission begins after reaching a certain “time threshold” in range 0–10 s, and disappearing afterwards. Beforehand, several possible LIBE mechanisms have been proposed for different materials, however they don’t cover all aspects of this phenomenon. In the present article, the intervalence charge transfer (IVCT) model is considered as general for RE doped phosphors. The features of LIBE have been described within this model

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Photo by Tim Oun on Unsplash

Photo by Tim Oun on Unsplash

Why is it important?

In the present paper, IVCT mechanism of broadband light emission is discussed by considering electron transfer between Yb3+/Yb2+ valence pair. IVCT is an optical transition that involves transfer of an electron in Yb2+/Yb3+ mixed valence pair and most likely occurs between two closely spaced Yb2+ and Yb3+ ions, e.g., in an oxygen linkage (Yb2+-O-Yb3+) in the YAG crystal. Due to the fact that the concentration of Yb2+ ions is lower than that of Yb3+, one can assume that the number of photons, decay and rise times, emission intensity etc, which are LIBE parameters, are determined by the concentration of Yb2+ ions in the sample.

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