Highly efficient Er³⁺ doped fibre lasers pumped at 980nm

The Er3+ fibre laser operates at a wavelength between 1.5 and 1.6 microns and is thus of interest for both telecommunication purposes and, since it can be Q-switched to give high pulse powers, in eye-safe range-finding systems. To date, ~810nm has been the preferred pump wavelength owing to the ready availability of laser diodes. However, the 810nm pump band of Er3+ suffers from the serious disadvantage of pump excited-state absorption (ESA). As a result much of the pump light is wasted in exciting ions from the metastable level to a still higher energy level, rather than producing stimulated emission. This is reflected in the best reported slope efficiency of 17%, obtained for Er3+ sensitized with Yb3+