Q-Switched Raman Fiber Laser with Molybdenum Disulfide-Based Passive Saturable Absorber

We demonstrate a Q-switched Raman fiber laser using molybdenum disulfide (MoS_2) as a saturable absorber (SA). The SA is assembled by depositing a mechanically exfoliated MoS_2 onto a fiber ferrule facet before it is matched with another clean ferrule via a connector. It is inserted in a Raman fiber laser cavity with a total cavity length of about 8 km to generate a Q-switching pulse train operating at 1560.2 nm. A 7.7-km-long dispersion compensating fiber with 584 ps\cdotnm^-1km^-1 of dispersion is used as a nonlinear gain medium. As the pump power is increased from 395 mW to 422 mW, the repetition rate of the Q-switching pulses can be increased from 132.7 to 137.4 kHz while the pulse width is concurrently decreased from 3.35 μs to 3.03 μs. The maximum pulse energy of 54.3 nJ is obtained at the maximum pump power of 422 mW. These results show that the mechanically exfoliated MoS_2 SA has a great potential to be used for pulse generation in Raman fiber laser systems.