Fabrication and characterization of ytterbium doped transparent laser ceramics

Abstract

Transparent laser ceramics have shown great application potentials as the host materials of solid state lasers, because of their excellent physical and stable chemical properties.Solid state lasers have wide applications in the fields of industry, communication, medical and military, such as laser drilling and welding, laser surgery and even laser weapons. Compared with their single crystal counterparts, polycrystalline ceramics possess various advantages, such as shorter fabrication period, higher yield for mass production, higher ion doping concentration, feasibility to be large sizes with complex shapes and structures, and overall lower fabrication cost.Among various laser ceramics, ytterbium (Yb 3+ ) ion doped ones have been considered to be very attractive solid state laser materials. Yb 3+ ion has unique properties, including high quantum efficiency, long fluorescence lifetime and broad emission spectrum. Its broad absorption band is especially useful for direct laser diode pumping. Yttrium aluminum garnet (YAG) is a very popular laser host materials, because of its high hardness, high thermal conductivity and stable chemical property. Its cubic crystal structure is also important to achieve high optical transparency. However, processing and fabrication of transparent ceramics with high optical transparency is still a challenge.The work in this thesis is focused on the development of ytterbium doped transparent laser ceramics, mainly based on YAG garnet. By using high purity Yb2O3, Al2O3 and Y2O3 powders as starting materials, ytterbium doped YAG (Yb:YAG) ceramics with different concentrations of Yb were fabricated by using the conventional solid-state reaction process, combined with vacuum sintering technique. XRD results showed that all samples obtained were of pure garnet phase. SEM characterization results revealed that all samples had very dense and pore-free microstructure, with the average grain size of about 10 µm. demonstrated in the previous chapter. Characterizations of in-house fabricated Yb:GdYAG ceramics are also carried out. CW and mode-locked laser operations of the samples are successfully demonstrated. Chapter 6 presents the development of the YLuAG garnet ceramics as an alternate host material for the Yb ion. The new type of Yb:LuAG ceramics have been obtained