Why so deep research on Yb3+-doped optical inorganic materials?

The state-of-art of Yb3+-doped inorganic materials will be presented due to strong interests in basics research and applied research. 4f13 configuration will be illustrated by few examples such as optical transition assignments in the IR range, diode pumped-IR laser, figure-of-merit of laser crystals, concentration quenching studies, evidence of Yb3+ pairs, the advance of Yb3+-doped cubic ceramics for laser sources, Yb3+ as sensitizer of activator ions and Yb3+ ion as structural probes of hosts. The last results analysed will concern charge transfer processes of Yb3+ in oxides and the interests in luminescence.