Photon cutting for excitation Er3+ions in SiO2 sensitized by Si qunatum dots

We present evidence of a mechanism for the indirect excitation of Er3+ ions in a SiO2 matrix sensitized with Si quantum dots (SiQDs). The proposed process enables the simultaneous and rapid excitation of two proximal Er3+ ions upon absorption of a single high-energy photon in a SiQD. The experimental evidence leading to the identification of this energy-transfer path is obtained from investigations of the photoluminescence quantum yield of two Er-related emission bands at 1.54 and 0.98 μm in SiO2 layers doped with small (∼2-nm-diam) SiQDs and a high concentration of Er3+ ions, prepared by sputtering on hot substrates. In contrast to the previously considered mechanisms for the indirect excitation of Er3+ ions in SiO2, this excitation process offers an advantage of efficient suppression of the most important channels of nonradiative deexcitation—the Auger energy transfer to free carriers as well as the so-called energy back transfer of excitation reversal. This feature revives hopes for the practical application of Er-doped SiO2 sensitized by SiQDs.