Preparation of transparent cobalt doped glass ceramic and application as saturable absorber Q switch for 1.54 μm Er-glass laser

Glass with composition of 51SiO2–24.5Al2O3–23MgO–1.5K2O doped with Co2+ ions was prepared by conventional melting method. The glass sample was heated at 900 °C for 360 min under atmosphere, and the powder XRD measurement showed that crystalline phase successfully precipitated in the sample. As is compared with standard JCPDS card, the crystalline phase identified as a mixture of zirconium titanate (ZrTiO4) and one of the compounds of magnesium aluminum oxide. The crystallite size was confirmed by transmission electron microscope (TEM) observation; it could be estimated as 30 nm in diameter from the TEM image. Based on the area ratio of crystalline phase and residual glass phase, the precipitated crystallite phase volume ratio can be estimated to be not higher than 30% in the Co2+ doped glass ceramic sample. The absorption coefficient at 1.54 μm for transparent glass ceramic sample is clearly higher than that in base glass, which can be explained by the fact that Co2+ ions entered into the precipitated nano-sized crystal phase and led to higher absorption coefficient at 1.54 μm for tetrahedral coordinated Co2+ ion. Consequently, the Co2+ doped transparent glass ceramic sample with thickness of 0.35 mm was used as a saturable absorber for 1.54 μm Er-glass laser oscillation, and Q switched pulses with pulse energy of 40 mJ, pulse width of 42 ns, and peak power of 0.95 mW were shown in the experiments.