Monday, 26 October 2015, 15:00
Sala Grande Palazzina B via alla Cascata 56/C
Transparent YAG ceramics for laser applications
Institute of Science and Technology for Ceramics (CNR ISTEC),
Via Granarolo 64, Faenza
Yb-doped yttrium aluminium garnet (Yb:YAG) is an important IR solid state laser gain medium, which allows significantly higher doping (one order of magnitude) compared to the generally more frequently used Nd:YAG. The preparation of transparent polycrystalline Yb:YAG ceramics for laser applications via vacuum sintering will be presented. The effect of Yb on the microstructure, optical quality and material properties (thermal and mechanical properties both at room temperature and at elevated temperatures) was studied. Samples with optical transmittance higher than 80 % were prepared and slope efficiency more than 70 % was obtained in the case of 5 at. % and 10 at. % Yb doped ceramics. The effect of the possible presence of secondary phases or pores on the optical transmittance of YAG ceramics via light scattering will be discussed with reference to known relations (Rayleigh and Fraunhofer), and an approximating approach is shown, which allows to predict transmittance with respect to the size and quantity of pores or inclusions. Finally, the lecture will discuss the advantages of ceramic processing for the preparation of layered composite materials which allow better thermal management and mitigating of thermal effects, in particular thermal lensing, and reports on the obtained results.
Keywords: Laser ceramics; Yb:YAG; Scattering; Laser performances.