Results are presented, for the first time, regarding the spectroscopy
and the laser performance of a fluorozirconate fibre codoped with thul
ium and terbium (0.1 % : 1 %). This doping scheme relies on concentrat
ion induced cross-relaxation effects to relieve population bottlenecke
d in Tm H-3(4) to Tb F-7(0). A minimum threshold of 5.5 mW and a maxim
um slope efficiency of 16% with respect to launched pump power has bee
n observed for operation on the 1-47 mum transition.