Jiri Smejcky and Vitezslav Jerabek 2020. Differential Gain Comparison of Optical Planar Amplifier on Silica Glasses Doped with Bi-Ge and Er, Yb Ions. Journal of Material Science and Technology Research. 7, (Mar. 2020),  71–79. DOI:https://doi.org/10.31875/2410-4701.2020.07.08.