Solid-state lasers have aroused many researchers’ interests for a variety of applications in military and industrial fields. Because of the preference for increased output power, Nd:YAG single crystals, which are the most widely used gain media, should be replaced by other more suitable candidates. Polycrystalline sesquioxide ceramics show great potential for use as gain media because their thermal and mechanical characteristics are suitable for use with high-energy laser systems. Recently, novel concepts of the gain media were also introduced. Herein, while briefly looking back on the progress of polycrystalline laser ceramics, we will discuss new interests in host materials and systems.