Visible up-conversion photoluminescence from IR diode-pumped SiO2–TiO2 nano-composite films heavily doped with Er3+–Yb3+ and Nd3+–Yb3+

Efficient infrared-to-visible conversion is reported in thin film nano-composites, with composition 90% SiO2–10% TiO2, fabricated by a spin-coating sol–gel route and co-doped with Er3+ Yb3+ and with Nd3+:Yb3+ ions. The conversion process is observed under 808 nm laser diode excitation and results in the generation of green (526 and 550 nm) and red (650 nm) emissions: from the former, and blue (478 nm) and green (513 and 580 nm) emissions from the latter. The main mechanism that allows for up-conversion is ascribed to energy transfer among Er3+ and Yb3+ ions in their excited states. Up-conversion efficiency for red emission predominates in samples doped with Er3+:Yb3. The results illustrate the large potential of this class of materials for photonic applications in optoelectronics devices.