A simple way to prepare Co:MgAl2O4 transparent ceramics for saturable absorber

Co-doped magnesium aluminate (Co:MgAl 2 O 4 ) transparent ceramics were obtained by pre-sintering in air and hot isostatic pressing (HIP) with commercial spinel and CoO powders as raw materials. The influences of the pre-sintering temperature on the microstructure and optical quality of the 0.05 at% Co:MgAl 2 O 4 ceramics were studied. It is found that the relative density of Co:MgAl 2 O 4 ceramics increases from 96.8% at 1500 °C to 98.7% at 1600 °C and then decreases with further increasing the pre-sintering temperature. The average grain size of Co:MgAl 2 O 4 ceramics increase from 4.6 μm to 19.2 μm with the increase of pre-sintering temperature from 1500 to 1700 °C. For the sample pre-sintered at 1600 °C for 5 h and HIP post-treated at 1800 °C for 3 h, the average grain size is about 23.0 μm and the near in-line transmittance reaches 75% at the wavelength range of 1700–2400 nm. The ground state absorption cross section at 1540 nm of the optimal 0.05 at% Co:MgAl 2 O 4 ceramics is calculated to be 2.9 × 10 −19  cm 2 .