A great advantage of transparent ceramics is the high flexibility of the production process, in particular in terms of shaping and spatial control of distribution of doping ions. In laser gain media a properly designed controlled spatial distribution of the active ion within the medium can reduce undesired thermally induced effects and large temperature gradients, and thus enhance the efficiency and laser beam quality especially under increased thermal load. This is of utmost importance for high-power lasers, for which thermal management is a crucial issue. A very promising system for high-power laser gain media is Yb:YAG. Tape casting was chosen as a production method for bulk multilayered ceramics because it allows a high precision and good control over dopant distribution in the sintered material. Transparent YAG ceramics with structured Yb doping were produced by the tape casting method followed by thermal compression of assembled tapes; the ceramic samples were sintered under high vacuum. The microstructure of sintered materials was characterized by SEM-EDX with particular attention paid to the distribution of Yb across the layers. The thickness of Yb diffusion zones between the layers with different Yb content was measured. Optical homogeneity was evaluated by means of optical transmittance mapping of the samples and by 2D scanning of laser output. Laser performance was measured in quasi-CW and CW regime with different duty factors in order to evaluate the effect of structured dopant distribution. Slope efficiency values exceeding 50% were measured both in quasi-CW and in CW lasing conditions. The obtained experimental results are in good agreement with previously calculated predictions, confirming the advantage of structured doping and enlightening the impact of the residual scattering losses. Compared to other processing methods, such as the pressing of granulated powders, tape casting followed by thermal compression leads to straight and narrow interfaces between layers with different composition and allows to build structures composed of extremely thin layers with defined dopant content.
Transparent layered YAG ceramics with structured Yb doping produced via tape casting
Jan Hostasa;Andreana Piancastelli;Guido Toci;Matteo Vannini;Valentina Biasini;Laura Esposito
2016
Abstract
A great advantage of transparent ceramics is the high flexibility of the production process, in particular in terms of shaping and spatial control of distribution of doping ions. In laser gain media a properly designed controlled spatial distribution of the active ion within the medium can reduce undesired thermally induced effects and large temperature gradients, and thus enhance the efficiency and laser beam quality especially under increased thermal load. This is of utmost importance for high-power lasers, for which thermal management is a crucial issue. A very promising system for high-power laser gain media is Yb:YAG. Tape casting was chosen as a production method for bulk multilayered ceramics because it allows a high precision and good control over dopant distribution in the sintered material. Transparent YAG ceramics with structured Yb doping were produced by the tape casting method followed by thermal compression of assembled tapes; the ceramic samples were sintered under high vacuum. The microstructure of sintered materials was characterized by SEM-EDX with particular attention paid to the distribution of Yb across the layers. The thickness of Yb diffusion zones between the layers with different Yb content was measured. Optical homogeneity was evaluated by means of optical transmittance mapping of the samples and by 2D scanning of laser output. Laser performance was measured in quasi-CW and CW regime with different duty factors in order to evaluate the effect of structured dopant distribution. Slope efficiency values exceeding 50% were measured both in quasi-CW and in CW lasing conditions. The obtained experimental results are in good agreement with previously calculated predictions, confirming the advantage of structured doping and enlightening the impact of the residual scattering losses. Compared to other processing methods, such as the pressing of granulated powders, tape casting followed by thermal compression leads to straight and narrow interfaces between layers with different composition and allows to build structures composed of extremely thin layers with defined dopant content.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
