The Research On Single Frequency Fiber Lasers Based On MoS₂ And Yeterbium Doped Fiber Saturable Absorber

Single-frequency lasers, especially the SF fiber lasers with wavelength around 1?m, with narrow linewidth, high signal.to.noise ratio, low intensity noise, wide tuning range of wavelength, have been attracted intense interest of investigators. Due to the excellent characteristics, these SF lasers have widely applications coherent communications, optical fiber sensors, laser ranging, materials processing and so on. In this paper, the single frequency fiber laser based on MoS₂, ytterbium.doped fiber as the saturable absorber is studied and achieved 1064nm,1083nm single frequency laser with narrow linewidth. The main work and the experimental results are as follows:Firstly, we introduced the energy structure and spectroscopic properties of ytterbium ions, and theoretically analyzed the small signal gain of ytterbium fiber with different lengths. Meanwhile, we theoretically calculated the power distribution in the resonant cavity, the change trend of output power with the gain fiber length. We also introduced several methods of measuring the single frequency laser linewidth, and explained the advantages and disadvantages. Besides, we explained the mechanism of the fiber loop mirror and loop mirror filter, and provided a theoretical basis for our experiment.Then, we present a single.frequency fiber laser at 1064 nm with linewidth of<12 kHz, by incorporating a molybdenum disulfide film ?MoS₂? saturable.absorber mounted on a fiber loop mirror with FC/PC connector. The structure of our configuration combined the advantages of LMF and MoS₂, which was simple, compact and high reliability. Furthermore, a polarization controller was introduced to suppress the spatial hole burning effect in the linear resonator. The maximum output power reached 15.3 mW with the optical signal to noise ratio larger than 50 dB. The maximum optical.to.optical conversion efficiency and slope efficiency were 11.6% and 15.3%, respectively. The output power and spectrum fluctuations of the proposed fiber laser for an hour were less than ±2.7% and 0.3%, respectively. The experimental results demonstrated that MoS₂ film could act as a promising filter for single.frequency laser systems.Finally, we adopted the linear cavity to achieve a single frequency 1083nm laser with a linewidth of 4 kHz. The maximum output power reached 46 mW with the optical signal to noise ratio larger than 60dB. The maximum optical.to.optical conversion efficiency was 23% and the slope efficiency was 33.3%, respectively, and the output power and spectrum fluctuations of less than ±3% and 0.9%, respectively. Besides, we also adopted the ring cavity to achieve a single frequency laser with a linewidth of 1 kHz. The centre wavelength was 1083.06nm. The maximum output power was 2.04mW with the optical signal to noise ratio less than 55dB. The slope efficiency was very low ?less than 3%?.