Enhancement of luminescence quantum yield of 1.5 μm emission from Er-doped SiO_2 sensitized with Si nanocrystals

摘要

Excitation of multiple Er~(3+) ions upon absorption of a single high-energy photon increases Errelated emission at 1.5 μm, and therefore enhances UV/visible-to-IR photon conversion efficiency. Here we investigate this effect for layers of Er-doped SiO_2 sensitized with silicon nanocrystals by measuring the quantum yield of 1.5 μm Er-related emission. We demonstrate dramatic increase of the emission commencing for excitation energies above a certain threshold value, as the number of Er~(3+) ions excited upon absorption of a single incoming photon increases. By comparing differently prepared materials, we show that the actual value of this threshold energy and the rate of the observed increase of the quantum yield depend on sample characteristics - the size of Si nanocrystals and the ratio of Er~(3+) ions and nanocrystals concentrations.