Sol–gel-derived Yb:YAG polycrystalline ceramics for laser applications

Yb-doped YAG single crystal is commonly used as the active material in high power lasers. Sol–gel processing is a possible alternative to prepare a similar active polycrystalline ceramic at lower cost. This work describes the preparation of YAG matrix ceramics by sol–gel with a continuous replacement of Y3+ by Yb3+ in the YAG structure. X-ray diffraction showed that the cubic YAG phase was obtained for all Yb doping levels. Structural characterization by infrared and Raman spectroscopies followed the replacement of Y by Yb. Finally, Yb3+ photoluminescence spectra were recorded, together with lifetime measurements, which yielded values in the range of 0.5–0.9 ms. Using Er co-doping as an internal standard, the absolute intensities of the Yb3+ photoluminescence peaks were compared and the optimum Yb concentration for maximum photoluminescence efficiency was determined at ~50 mol% Yb. Based on the photoluminescence efficiency and the lifetime values, a figure of merit for laser operation was maximum for the 40 mol% Yb concentration.