Single-mode-fiber saturable absorber

Saturable absorption is performed on a signal in a single-mode fiber by allowing the evanescent field of the guided wave to interact with a saturable-absorbing dye. The evanescent field is exposed by mechanically removing a portion of the fiber cladding. The saturable material is then placed in close proximity to the fiber core. The singlemode-fiber saturable absorber is characterized by a nonlinear transmission versus input optical intensity. Transmissions ranging from 50 to 80% have been demonstrated using Eastman 9860 saturable-absorbing dye and optical pulses from a Q-switched Nd:YAG laser.