Yb3+-doped Gd3Ga5O12 garnet single crystals grown by the micro-pulling down technique for laser application. Part 2: Concentration quenching analysis and laser optimization

This article is following the first part published recently in this journal [S. Chénais, F. Druon, F. Balembois, P. Georges, A. Brenier, G. Boulon, Opt. Mater. 22 (2003) 99]. Yb3+ concentration dependence of the 2F5/2 excited level experimental decay time in GGG laser crystal was analyzed in order to understand involved concentration quenching mechanisms. Under Yb3+ ion infrared pumping, self-trapping and up-conversion non-radiative energy transfer to rare earth impurities (Er3+, Tm3+) have been observed in visible region and interpreted by a limited diffusion process within the Yb3+ doping ion subsystem towards impurities. OH− quenching centres, Yb2+ ions and color centres may also be involved in such processes but Yb3+ pairs do not seem efficient. Main parameters useful for the optimization of laser potentiality have also been given from a new model which has been published recently.