Q-switching of a distributed feedback fiber laser by using longitudinal acoustic waves

This paper reports an actively, Q-switched distributed feedback (DFB) laser based on the dynamic generation of a defect, by means of the propagation of a longitudinal acoustic pulse along an uniform FBG. The acoustic pulse stretches locally a section of the grating, causing a narrow transmission peak within the reflection band of the grating. The dynamic nature of this technique arises from the fact that the transmission window is opened up only during the time that the pulse travels along the FBG. Then, by launching acoustic pulses into the FBG, the transmission peak is switched on and off, according to the repetition rate of the acoustic pulses