Optical Transitions And Energy Transfers Of Rare Earth Ions In Tellurite Glasses For Mid-infrared Lasers

Midinfrared laser sources will have wide uses in the fields of transportation industry, shipping industry, medical science, military science and trace gas monitoring, and especially they may have great potential value for applications in maritime aspects, for instance transport guidance, ships navigation, collision avoidance, maritime communication, remote sensing, countermeasures and so on. Therefore, midinfrared laser devices and materials have attracted great attention and much interest from the scientists. Midinfrared lasers based on the rare earth ions doped glasses or monocrystals pumped by near infrared diodes are more preferarable than other kinds. The Er''doped midinfrared laser materials and devices have become a hot spot in the research on rare earth doped crystal and fiber lasers pumped with infrared laser diodes.Aiming at some key problems in the Er3+doped midinfrared laser materials, it is proposed that the tellurite glasses are adopted as host materials and Nd3+ is introduced as sesitizer and quenching center of I13/2 level of Er3+;it is expected that in this way the midinfrared emitting materials with high performance could be obtained. The following results have been achieved:(1) A set of tellurite glasses with composition of 70TeO2-(10-x)PbF2-10AlF3-10BaF2-xRE2O3, where RE is one or two amongst Eu, Nd and Er elements, was designed and prepared successfully. The glasses were found through research to have relatively small phonon energy of about 700 cm-1(2) Optical transition properties of Nd3+ in the tellurite glasses were analyzed in the framework of Judd-Ofelt theory, and optical transition intensity parametersΩ2,Ω4 andΩ6 were obtained accordingly. The theoretical oscillator strengths, radiative transition rates, transition branching ratios and radiative transition lifetimes for Nd3+ in the studied sample were obtained. The emission cross section for 1.06μm emission and the excited-state absorption cross section for 4I11/2→4F3/2 transition of Nd3+ were also obtained rooted in Fuchtbauer-Ladenburg theory. It was found that Nd3+ doped tellurite glass is an excellent infrared laser material based on our evaluation on the laser gain characteristic of 1.06μm emission.(3) Optical transition properties, and the blue, green and red upconversion luminescence mechanisms, as well as the 1.5μm downconversion luminescence mechanism of the desined Er3+ singly doped tellurite glasses were studied. The optical transition intensity parametersΩ2,Ω4 and Q6 of Er3+ were calculated. The oscillator strengths, radiative transition rates, transition branching ratios and radiative transition lifetimes etc. of the energy levels lower than 2H11/2 of Er3+were obtained. The results suggested that this material may be a potential upconversion and downconversion laser material.(4) The up-/down-conversion and midinfrared luminescence properties of the Nd3+/Er3+co-doped tellurite glass were experimentally studied. As a result, the introduction of Nd3+into the glass has effectively quenched the upconversion and infrared emisions of Er3+, and therefore this causes an effective increase in midinfrared emission. The reason for the phenomenon was analysed finally.