Transparent Cobalt-Doped Yttrium Aluminum Garnet (Co2+:Yag) Ceramics-An Innovatory Fast Saturable Absorber

Highly transparent Y3Al5O12 (YAG) ceramics doped with 0.025 and 0.05 at.% Co ions were prepared for the first time by the freeze granulation process and reaction sintering. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed to analyze the microstructure and crystal structure of the samples. The absorption spectra of the Co2+:YAG ceramics were measured at room temperature, and significant absorption bands at 600 nm, as well as at 1535 nm, were observed. The nonlinear behavior of the received material was experimentally demonstrated. Due to the short relaxation time of investigated ceramics, we considered them as fast saturable absorbers. The influence of the postsintering annealing process was examined. The values of saturation intensities of YAG ceramics with different concentrations of cobalt were estimated by fitting experimental data to the theoretical model for fast saturable absorbers.