Spectroscopic and lasing properties of rare earth ion based laser materials

Scope and method of study. The spectroscopic and lasing properties of several rare-earth based laser materials were investigated. The dynamics of energy transfer in Tm,Ho:YAG were studied using time-resolved spectroscopy. The results were used in a rate equation based computer simulation of laser operation. Absorption, fluorescence, and fluorescence excitation spectroscopy were used to investigate the origin of blue emission in Nd:YAG, Nd:GSGG, and Nd:ZBAN. Alexandrite laser pumped lasing properties of Nd:ZBAN were also studied. The effects of a pump wavelength dependent loss mechanism were examined using a rate equation based computer simulation of the Nd:ZBAN laser system.; Findings and conclusions. Evidence for energy migration in the {dollar}rm Tmsp{lcub}3+{rcub} sp3Hsb4{dollar} multiplet was found. A mechanism producing green emission involving excited state absorption of pump photons from the Ho{dollar}sp{lcub}3+{rcub}{dollar} metastable state was also identified. Rate parameters for the relevant energy transfer processes for Tm,Ho:YAG were determined through spectroscopic measurements. Using the spectroscopically determined rate parameters and no fitting parameters, computer simulations of laser operation were able to reproduce the relaxation oscillations and the time delay between the pump and lasing output previously observed experimentally. The origin of the blue emission observed in Nd:YAG and Nd:GSGG was identified as the {dollar}rmsp2Psb{lcub}3/2{rcub}{dollar} multiplet. An excited state absorption process involving a pump photon and an ion excited to the {dollar}rmsp4Fsb{lcub}5/2{rcub}, sp2Hsb{lcub}9/2{rcub}{dollar} multiplets was found to populate the {dollar}rmsp2Psb{lcub}3/2{rcub}{dollar} multiplet. Similar processes were also identified in the Nd:ZBAN system and the first laser operation of this material in bulk form was reported. Computer simulations indicated that only in materials with slow non-radiative decay processes and in systems with high peak power pump sources would excited state absorption of pump photons from levels above the metastable state be an important loss mechanism in Nd{dollar}sp{lcub}3+{rcub}{dollar} based laser materials.