Rare Earth Doped To The Study Of Energy Conversion Efficiency And Mechanism

Due to the development of semiconductor laser technology and the urgent requirement of blue-green compact solid laser which can be applied to develop disk technology, information technology, color display, color printing, medicine diagnosis and under water optical communication, great progress was achieved in the process of developing blue-green compact solid laser output pumped with high power semiconductor laser. But up to date, laser materials, which can be directly used to realize laser operation, is still in shortage. Therefore, it抯 extraordinary important to study the influence of host materials on up-conversion efficiency and the up-conversion mechanism of rare-earth ions.In order to discuss the influence of host on the up-conversion efficiency of rare-earth ions, the maximum phonon energy of host materials as well as the relation between the quasi-field parameter M of host materials and the coefficient M of rare-earth compound were investigated. The conclusion was drawn out that hosts with low phonon energy are beneficial to energy up-conversion. It is also found that when the value of quasi field Ki of host is adjusted near to that of the doped rare earth, the materials show high up-conversion efficiency. Selecting suitable excitation photon energy to match the level of activated ions and/or sensitizer ions is a necessary condition for high up-conversion efficiency.The up-conversion processes of Er3~-Yb3~ co-doped and Ho3~-Yb3~ co-doped systems were analyzed by applying rate equations. It is found that the direct up-conversion sensitization luminescence is the main up-conversion mechanism in Er3~-Yb3~ co-doped system. While in Ho3~-Yb3~ co-doped system. It is found that the efficiency of greenVemission (S2 ??) can be enhanced by restraining the transition of 5S2 ?5J7 since the two kinds of radiation both initiate on ~S2 level. Thus a significant approach to enhance an expected up-conversion emission has been proposed.It is interesting that we firstly found many novel emissions with strong intensities of Yb3~ ions. In chapter four the corresponding values of the novel spectral lines are calculated by quasi- hydrogen atom model and the up-conversion mechanism is explained with collision model.Additionally, in order to quest for appropriate rare-earth doped concentration in host, we also studied concentration-quenching effect in several kinds of hosts and found out the optimal rare-earth doped concentration range in the hosts.