Experimental study of an actively mode-locked fiber ring laser based on in-fiber amplitude modulation

We report an experimental study of an actively mode-locked fiber ring laser based on the development of an efficient in-fiber amplitude modulator. Intermodal coupling induced by standing flexural acoustic waves permits the implementation of broad bandwidth (1.5 nm), high modulation depth (72%), low-insertion-loss (0.75 dB), in-fiber amplitude modulators, operating in the MHz frequency range. The experimental characterization of the laser as a function of the radio frequency voltage that controls the modulator, the length of the active fiber, and the optical bandwidth of an intracavity filter implemented with a fiber Bragg grating has led to an improved performance of the Erbium-doped fiber laser: optical pulses of 34-ps temporal width, 1.4-W peak power, and 4.75-MHz repetition rate.