- Transparent Co 2+ doped MgAl 2 O b4 spinel was fabricated by SPS consolidation followed by and HIP treatment. It was established that HIP treatment significantly improved transparency of the ceramic in a wide range of wavelengths, especially, in a range, which is relevant for Q-switching. Nonlinear absorption was demonstrated and the ground and excited state absorption cross sections were estimated. The positive effect of the HIP treatment on the optical properties is related to an elimination of extremely fine porosity and to the location of Co ions at Mg 2+ sites in the spinel ionic structure. The experimental results indicate that the fabricated specimens can be used as a passive laser Q-switching material.