An Overview on Yb-Doped Transparent Polycrystalline Sesquioxide Laser Ceramics

This paper is devoted to summarizing and discussing the scientific progress achieved during the past decade in diode-pumped ytterbium-doped solid-state lasers. The output radiation centered on the 1-μm region is of particular interest for the well-known applications of previously developed Nd
³⁺
lasers. Several hosts have been studied and tested in recent years. Due to the enormous number of papers dealing with ytterbium, Yb
³⁺
, doped hosts, we will limit our report here to materials based on transparent polycrystalline sesquioxide laser ceramics, such as Lu
₂
O
₃
, Sc
₂
O
₃
, and Y
₂
O
₃
. The reason is basically due to the wider emission band of ytterbium-doped sesquioxides as compared with more commonly used hosts such as YAG. The higher thermal conductivity with respect to hosts such as CaF
₂
makes them very interesting for applications requiring both good thermal conductivity and a wide fluorescence emission band, as well as for short pulse generation at high average power levels. Furthermore, the replacement of trivalent Yb in sesquioxides does not require any charge compensation (as is the for instance case of the replacement of divalent Ca in CaF
₂
), which makes their fabrication easier, in particular at high doping levels.