Improved emission of Tm(3+)-doped glass for a 1.4-mum amplifier by radiative energy transfer between Tm(3+) and Nd(3+).

We prepared a Tm-doped glass composite with a Nd-doped layer as a model 1.4-mum thulium-doped fiber amplifier (TDFA) to investigate the effect of energy transfer on the emission spectra of the composite. The competitive 0.8-mu;m emission from the Tm:(3)H(4) level, which had a branching ratio ten times larger than that of the 1.4-mum emission, was reduced to 1/6 of its previous value by radiative transfer to the Nd layer. Also, the 1.06-mum emission from the excited Nd(3+) was found to contribute to the upconversion pumping scheme for population inversion between the (3)i(4) and (3)F(4) levels of Tm(3+) . The Nd-doped glass phase can be used as a cladding material for an efficient TDFA.