Q-switched ring-cavity erbium-doped fiber laser based on tungsten disulfide (WS2)

Applying liquid-phase exfoliation method, we prepare WS2 dispersions with ethanol and fabricate WS2-PVA polymer composite film. As a saturable absorber, the WS2-PVA film is used to Q-switch a ring-cavity erbium-doped fiber laser. The Q-switched fiber laser can generate stable pulses when the pump power varies from 400 mW to 720 mW. The repetition rate and pulse duration can be tuned with pump power from 47 kHz to 77 kHz and from 6.7 μs to 4.1 μs, respectively. The radio frequency (RF) spectrum with a 58 dB extinction ratio at fundamental frequency also shows a good stability of Q-switching operation. Our work provides an easy and feasible method to fabricate WS2-PVA polymer composite film and demonstrates the possibility for WS2 to be a promising saturable absorber for Q-switched laser or even mode-locked laser.