| Rare earth doped chalcogenide glasses represent a group of materials that provide new opportunities for fiber amplifier and mid infrared laser applications. This work systematically investigated rare earth doping in a variety of chalcogenide systems, studied physical and chemical properties of rare earth doped chalcogenide glasses, and performed Judd-Ofelt analysis to predict the laser performance of rare earth ions in the new hosts.; The host glasses investigated included binary Ge-S and As-S, and ternary Ge-As-S, Ge-P-S, Ge-Sb-S and Ge-Ga-S systems. The solubility of rare earth is strongly dependent on the glass composition. While binary glasses can only dissolve several hundred ppm of rare earth ions, some selected ternary glass compositions exhibit a rare earth solubility of 1-2 wt%.; The spectroscopy of rare earth ions in sulfide glasses is characterized by a red-shift of the optical transitions and large oscillator strengths that are ascribed to the covalent bonding and high refractive index of the host materials. This host effect is particularly significant for hypersensitive transitions. In addition, the low phonon energy (350 cm{dollar}sp{lcub}-1{rcub}){dollar} of the host glasses leads to a very low nonradiative multiphonon relaxation rate. As a result, radiative transitions that have very high quantum efficiency and are usually completely quenched in oxides can be observed. A Pr-doped Ge-Ga-S glass, for example, showed a quantum efficiency of about 70% and a peak stimulated emission cross section of {dollar}1.33times10sp{lcub}-20{rcub}rm cmsp2/ion{dollar} for the important {dollar}rmsp1Gsb4to{lcub}sp3H{rcub}sb5{dollar} transition at 1.3 {dollar}mu{dollar}m. In fluorozirconate glasses, the quantum efficiency is only about 3% for the same transition. Fluorescence at 1.3 {dollar}mu{dollar}m was also observed in a Dy-doped glass due to the hypersensitive transition {dollar}rmsp6Fsb{lcub}11/2{rcub}to{lcub}sp6H{rcub}sb{lcub}15/2{rcub}{dollar} that is not detectable in other glass hosts. The quantum efficiency and gain cross section for the transition were estimated to be 17% and {dollar}4.35times10sp{lcub}-20{rcub}rm cmsp2/ion,{dollar} respectively. This emission could provide a novel approach for 1.3 {dollar}mu{dollar}m fiber optical amplifiers, provided that excited state absorption from intermediate levels at the signal wavelength does not present a problem.; Fluorescent emission at wavelengths longer than 2 {dollar}mu{dollar}m, especially in the 3-5 {dollar}mu{dollar}m region, was observed for Dy{dollar}rmsp{lcub}3+{rcub}, Hosp{lcub}3+{rcub}, Ersp{lcub}3+{rcub}, and Tmsp{lcub}3+{rcub}.{dollar} This abundance of fluorescence results from the very low phonon energy of the host glasses, and provides great opportunities for mid-IR laser applications. |
