[en] We calculated “density”/“molecular weight” ratio of glass former oxides and modifier oxides to increase a number density of rare-earth ions in glass phosphor. Based on the calculated results, GeO_2 and ZnO were chosen for the glass former oxide and the modifier oxide, respectively. The effects of substituting GeO_2 for B_2O_3, ZnO for Sb_2O_3, or ZnO for Bi_2O_3 on luminescence spectra in Sm"3"+-doped glass were not observed. On the other hand, a drastically luminescence spectrum changing of Pr"3"+-doped glass was observed by substituting GeO_2 for B_2O_3. The output power of Sm"3"+ -doped glass and that of Pr"3"+ -doped glass increased with substituting ZnO for Bi_2O_3. We successfully achieved an ultra-wideband luminescence from 760 nm to 1100 nm with the output power of 2.5 mW by combining a blue LED with 0.15Sm_2O_3-0.12Pr_6O_1_1-10ZnO-45Sb_2O_3-45GeO_2 glass in one package. (paper)