Fabrication and spectral properties of hot-pressed Co:MgAl2O4 transparent ceramics for saturable absorber

Cobalt-doped magnesium aluminate spinel (Co:MgAl2O4) could be the most effective saturable absorber (SA) for Q-switching solid-state lasers operating at 1.5 μm. Using LiF as the sintering aid, highly transparent Co:MgAl2O4 ceramics were fabricated by hot pressing (HP) of the commercial spinel and the co-precipitated Co:MgAl2O4 powder mixture. The optical properties of Co:MgAl2O4 ceramics were investigated, and the ground state absorption cross section (σgas) of Co2+ was calculated from the curve of the absorption coefficient. For the Co:MgAl2O4 ceramics hot-pressed at 1600 °C for 2 h under 30 MPa with 1 wt.% LiF addition, the in-line transmittance reaches about 77% at 1000 nm and 1700 nm, and the ground state absorption cross section of Co2+ is 2.55 × 10−19 cm2 at the wavelength of 1540 nm, which is promising as a saturable absorber for solid-state pulse laser operating at 1.5 μm.