Study Of Novel Mode-locked Fiber Laser At 2?m

2?m region has a variety of attractive applications in the fields of industrial processing,biological medicine,communication and remote sensing.Recent years,the research on short-pulsed fiber lasers at 2?m region has been developed increasingly in the international front domain.In this paper,mode-locked thulium-doped fiber laser at 2?m region are studied.Two new types of mode-locked fiber laser at 2?m region are designed to achieve wide wavelength-tunable range and long pulse duration/ duty cycle,respectively.The primary contents are shown as follows:1.All-fiber wavelength-tunable thulium-doped fiber laser mode-locked by SESAM is designed and achieved.Using an EYDFL at 1.5?m as the pump and a diffraction grating based tunable filter as the wavelength selection device,the tuning range of 121 nm,from 1862 nm to 1983 nm,is obtained.The range is the widest among the reported fiber laser mode-locked by SESAM.Temporal characteristics,optical spectrum and the signal-to-noise ratio are all measured accurately.The influence of devices on the tuning range including pump's wavelength and the length of gain fiber is also studied.3.A thulium-doped fiber laser mode-locked by SESAM in the dissipative soliton resonance(DSR)region with net normal dispersion is designed and achieved.Ultrahigh numerical aperture fiber and chirped fiber Bragg grating are used to adjust the net dispersion and optical chirp in the cavity.In this work,DSR generation with >800ns pulse width and >84% duty cycle is demonstrated.To the best of our knowledge,this result presents the longest DSR pulse duration and the highest pulse duty cycle that has been achieved for any fiber laser operating in the DSR regime.Moreover,soliton molecules and bunched soliton are studied in a thulium-doped fiber laser mode-locked by the combination of SESAM and nonlinear optical loop mirror.