1.6-μm emission from Ho3+-doped fluoride glasses

We have investigated the spectroscopic properties of the 1.6-mum emission from the I-5(5) --> I-5(7) transition of Ho3+ ions in fluoride glasses for use in U-band fiber amplifiers. The intensity profile of the emission peaks at similar to1660 nm, with a full width at half-maximum of similar to60 nm. The measured lifetime and emission cross section are similar to230 mus and similar to5.4 x 10(-21) cm(2), respectively. Frequency upconversion. to the F-5(1) state occurs simultaneously with excitation of the 1.6-mum emission, so the shorter-wavelength side of the I-5(8) --> I-5(5) absorption spectrum is favorable for population of the I-5(5) state. Codoping with rare earths such as Tb3+, Dy3+, Eu3+, and Nd3+ decreases the lifetimes of the lower-lying I-5(6) and I-5(7) levels and as a result would be of benefit in achieving population inversion between the fluorescing level and the lower-lying levels. (C) 2003 Optical Society of America.