Tunable microsecond Q-switched fiber laser using an all-fiber deionized water saturable-absorber

We experimentally demonstrated a tunable microsecond passively Q-switched fiber laser using deionized water (DIW) as a saturable absorber (SA). The DIW-SA was integrated into an all-fiber device by filling the gap between two cleaved fiber facets with DIW, which were enclosed in a glass ferrule. We observed a high nonlinear transmission through DIW-SA and implemented it in an erbium-doped fiber ring laser cavity. Microsecond Q-switched pulse trains were produced tunable from 1564.3 to 1603.4 nm using a fiber-optic Fabry-Perot interference filter within the cavity, avoiding peak water absorption while maintaining stable operation. Tunable and robust Q-switching of a fiber laser using water would open a new avenue of nonlinear aqua-photonics.