The role of tungsten oxide in Er(3+)-doped bismuth-germanate glasses for optical amplification in L-band

A series of novel Er(3+)-doped bismuth-germanate glasses containing different tungsten concentrations with a molar composition of 97.5[(75 − x)GeO(2)–25Bi(2)O(3)–(x)WO(3)]–2Sb(2)O(3)–0.5Er(2)O(3) (x = 5, 10, 15, 20, and 25 mol%) were fabricated. Their thermal properties are measured by differential scanning calorimetry. A structural investigation by Raman spectroscopy suggested that changes occurred in the glass network by WO(3) incorporation. By laser excitation at 980 nm, a strong emission from Er(3+) ions at 1532 nm is observed, while the WO(3) addition caused changes in the emission spectra. The emission cross-section spectra of Er(3+) are calculated by both McCumber and Füchtbauer–Ladenburg theories and their comparison showed these theories yielded slightly different results, but in both cases, the calculations showed that a gain signal in L-band can be achieved when 30% of the Er(3+) ions are at the excited state. This study proves that the Er(3+)-doped bismuth-germanate glasses are suitable for optical fiber amplifier applications operating at C- and L-band.