All-fiber lasers actively modelocked by acousto-optic modulation

The development of all-fiber lasers is of high interest because of the intrinsic robustness, compactness and energy efficiency. In-fiber amplitude modulators based on acousto-optic modulation of fiber Bragg gratings (FBG) permit the implementation of novel all-fiber actively modelocked lasers. Using either traveling or standing longitudinal acoustic waves, optical pulses between 500 and 100 mW peak powers and ~700 ps temporal width were obtained at 4.1 and 9 MHz repetition rates, respectively. Implementing a simultaneous active Q-switching, we have demonstrated a doubly active Q-switching and mode-locking of two different all-fiber laser configurations. In the case of the laser based on traveling acoustic wave modulation of a FBG, we obtained trains of 16-18 modelocked pulses (700 ps), within an envelope of 1.4 μs, an overall energy of ~0.68 μJ and a peak power higher than 200 W (1 kHz repetition rate, 270 mW pump power). In the case of the laser based on standing acoustic wave modulation of a FBG, the trains had 12-14 modelocked pulses (1 ns), within an envelope of 550 ns, an overall energy of 0.65 μJ and a peak power higher than 250 W (500 Hz repetition rate, 100 mW pump power).