To realize the goal of mid-infrared lasing in rare-earth-ion-doped chalcogenide glass fibers, it is important to achieve as
large a concentration as possible of the rare earth ion dopants in the host chalcogenide glass matrix, while minimizing
optical loss. However, when a large amount of rare earth dopant is added to the chalcogenide glass, solubility problems
can emerge which decrease glass stability and also impair optical properties. In this paper, the nature of the rare earth
additive is demonstrated to be pivotal, affecting both the chalcogenide glass stability and the optical scattering loss.
Dysprosium in the form of dysprosium metal foil, or as the salt dysprosium trichloride, is added to the
Ge16.5As9Ga10Se64.5 batch and glasses are obtained using the melt-cool method. The nominal Dy3+ concentration is 2000
ppm. The glass melting results, and powder X-ray diffraction and Fourier transform infrared spectrometry
characterization of the products, indicate major improvement in bulk glass stability, glass surface quality and optical loss
when the dysprosium additive to the glass batch is in the form of Dy0 (metal foil) rather than DyIIICl3. Reasons for this improvement are suggested.