First demonstration of rare-earth-doped anisotropic ceramic laser

Transparent polycrystalline ceramics have attracted much attention as new laser gain media due to their capability for engineered structure and improved high fracture toughness [1]. On the other hand, rare-earth-doped hexagonal fluorapatite crystals show excellent optical properties for extremely high power laser operation such as large stimulated emission and absorption cross-sections, as well as long fluorescence lifetimes [2]. However, it is difficult to obtain large-size and composite media by using conventional crystal growth method. Therefore, transparent polycrystalline (ceramic) laser media made of anisotropic materials are expected to provide the new generation high power laser oscillators. Recently, we have succeeded in fabricating highly transparent calcium fluorapatite (Ca 10 (PO 4 ) 6 F 2 , FAP) ceramics by applying rare-earth assisted magnetic grain orientation method (imposing 1.4 T magnetic field during slip casthing) and subsquent HIP sintering process [3, 4]. Here, we report about the microdomain-oriented Nd:FAP anisotropic ceramic laser.