Broadband amplified spontaneous emission from an Er(3+)-Tm(3+)-codoped silica fiber

A new type of amplified spontaneous emission (ASE) based on an Er-Tm-codoped silica fiber is reported. When the fiber was pumped at 980 nm, the emission yielded a 3-dB bandwidth over 90 nm (1460-1550 nm) without any external filters, which is twice larger than that produced by conventional Er-doped fiber ASE sources. We believe that the superposition of two ASE bands, one from Er ions near 1530 nm and the other from Tm ions near 1450 nm, results in the broad bandwidth. Temperature-dependent ASE powers and fiber-length-dependent spectra strongly suggest that photon-assisted energy transfer between the sensitizing ion, Er, and the acceptor ion, Tm, plays an important role in changes in the bandwidth's size.