Experimental study on relaxation oscillation in a detuned FM harmonic mode-locked Er-doped fiber laser

We experimentally studied the relaxation oscillation characteristics in a FM harmonic mode-locked fiber laser when the modulation frequency has a small detuning. The relaxation oscillation can lower the laser output power and make the amplitudes of output pulses uneven both in normal and abnormal dispersion cavities. While combined with self-phase modulation and the optical filter, the abnormal intra-cavity dispersion can suppress the relaxation oscillation phenomenon.