Sub-10 ns mode-locked fiber lasers with multimode fiber saturable absorber

Sub-10 ns mode-locked fiber lasers with multimode fiber saturable absorber (SA) were demonstrated. The all fiber SA has a structure of single mode fiber -graded index multimode fiber - single mode fiber (SMF-GIMF-SMF). Inserting such SA in the designed long laser cavities with normal and anomalous dispersion, the mode locking nanosecond pulses were directly produced. In an anomalous dispersion cavity, the resultant output pulses had central wavelength, pulse duration, and repetition rate of 1560 nm, 4.0 ns and 1.87 MHz. The obtained maximum single pulse energy was 6.68 nJ. In a nomalous dispersion cavity, a 5.8 ns dissipative soliton pulses were realized at the central wavelength of 1558 nm. And the maximum pulse energy was 2.2 nJ at the fundamental repetition rate of 4.6 MHz. Such sub-10 ns lasers with nanojoule energy based on an all fiber SA can be feasible seeds for fiber amplifications in many applications.