Anisotropic Yb:FAP laser ceramics by micro-domain control

We have realized highly transparent Yb:fluorapatite (FAP) ceramics by use of slip casting under rotational magnetic field, even though the main crystal axis become a hard magnetization axis due to the enhancement of magnetic anisotropy by the total angular momentum of 4f electrons in doped rare-earth ions. We confirmed that our Yb:FAP ceramics reached to have a laser-grade quality: it did not interrupt laser oscillation when it was inserted into a lasing cavity. We also evaluate the absorption and the round-trip loss including Fresnel loss of our Yb:FAP ceramics, which were 3.7 cm−1 at 902 nm and 0.26 (11.5% by a single pass) at 1064 nm, respectively.