Investigation on the characteristics of Q-switched pulses in an EDFL based on the saturable absorption effect of germanene

In this paper, an all-fiber passively Q-switched (QS) Er-doped fiber laser (EDFL) was designed and successfully demonstrated by innovatively employing germanene as saturable absorber (SA). Due to its low-warp honeycomb structure and remarkable zero bandgap property, germanene exhibits excellent potential for highly stable broadband pulse modulation. Based on the saturable absorption effect of germanene, a stable passive QS laser output was successfully achieved at 1530 nm under a threshold pump power of 63.7 mW. With the pump power increasing from 63.7 to 403.5 mW, the pulse repetition rate increases from 48.5 to 121.2 kHz accordingly. Meanwhile, we observe that the pulse width was shortened from 3.54 μs to 890 ns. The experimental results prove that germanene nanosheets have a promising future as a Q-switcher in fiber lasers.