Er-Doped Q-Switched Fiber Laser Based on MoS₂-SAM Fabricated by Langmuir-Blodgett (LB) Technique

In this letter, a Q-switched linear-cavity Er-doped fiber laser was prepared using a reflective molybdenum disulfide saturable absorber mirror (MoS₂-SAM). MoS₂-SAM with high uniformity and compactness was prepared using Langmuir-Blodgett (LB) technology. Films as thin as single molecule can be fabricated by LB technology under suitable conditions and thus, the nonsaturable losses of absorbers can be decreased. The modulation depth of MoS₂-SAM is 9.8%. By inserting MoS₂-SAM in Er-doped fiber lasers, a stable passive Q-switched operation was achieved with repetition rate ranging from 46.21 to 215.45 kHz and pulse duration ranging from 1316 to 319 ns. Under a maximum pump power of 500 mW, the laser still works stably with an average output power of 7.37 mW and a signal-to-noise ratio of 58 dB. Notably, the minimum pulse width is as narrow as 319 ns. This shows that LB method is a practical method to improve the performance of saturable absorbers.