Research On Key Technologies Of 3?m Ultrashort Pulse Fiber Lasers

The mid-infrared?mid-IR? ultrashort pulses with wavelengths at from 3 to 5 ?m possess very narrow pulse width ?picosecond to femtosecond order?, corresponding to a high peak power of vital importance application. The bandwidth of the mid-infrared laser at 3 to 5 ?m is the atmosphere of a transmission window. Because of its extremely high instantaneous power, the mid-IR ultrashort pulses at 3-5 can cause the saturation of photoelectric detector easily and instantly. Especially, the water molecules has a strong absorption peak in around 3 ?m. The skin tissue is highly absorptive when interacting with the mid-IR ultrashort pulses at 3 ?m. The 3 ?m mid-infrared ultrashort pulses utilized in laser surgery can make blood clot immediately and have the advantages of small wound, good hemostatic, remove surface layer quickly and accurately. Therefore, the mid-infrared ultrashort pulse laser in the near 3 ?m promises a bright prospect of applications in the fields of military and medical treatment. Fiber lasers show several advantages over other types of lasers. They are efficient, compact, and rugged since they require few bulk components and are virtually unaffected by the surrounding environment. Therefore, the study of mode-locked mid-infrared fiber lasers in the near of 3 ?m is significant importance. So far, the theory simulation of the mid-infrared ultrashort pulse near 3 ?m is limited. This paper mainly aimed at the theory of simulation of the mid-infrared ultrashort pulse fiber laser near 3 ?m.Firstly, this paper introduce the research and application status of the near 3 ?m mid-infrared ultrashort pulse fiber laser, and analyzed several key factors in achieving a stable 3 ?m mid-infrared ultrashort pulse generation. Secondly, according to the nonlinear Schrodinger equation ?NLSE?, a theoretical model of passively mode-locked Er2+-doped fluoride fiber laser using a saturable absorber is set up. Some mechanisms included saturable absorber unsaturated loss, Er³⁺doped fluoride fiber laser oscillator net intracavity dispersion, Er³⁺ doped fluoride gain fiber length and the small signal gain for generating mid-IR ultrashort pulse in fiber lasers are investigated. Finally we design the graphene saturable absorber for 3 ?m mid-infrared ultrashort pulse mode locking fiber laser based on which and we designed a passively mode-locked Er³⁺ doped fluoride fiber oscillator.Based on the nonlinear Schrodinger equation ?NLSE?, a theoretical model of passively mode-locked Er³⁺-doped fluoride fiber laser using a saturable absorber is set up.Some mechanisms included saturable absorber unsaturated loss, Er2+doped fluoride fiber laser oscillator net intracavity dispersion, Er³⁺ doped fluoride gain fiber length and the small signal gain for generating mid-IR ultrashort pulse in fiber lasers are investigated. The Er³⁺ doped fluoride fiber laser oscillator parameters were optimized.We researched based on graphene saturable absorber in 3 ?m mid-infrared ultrashort pulse mode locking fiber laser; and passively mode-locking Er³⁺-doped fluoride fiber oscillator we design based on graphene saturable absorber scheme.This work may be beneficial to the design of experiments for achieving more narrow pulse duration, wider spectral width, and higher peak power in mid-infrared ultrashort pulse.