Study On Widely Tunable Ultrashort Pulse Fiber Laser Around 2?m And Its Application

2 ?m femtosecond pulse fiber lasers have wide applications in basic science researches,biomedicine,material processing,environmental pollution monitoring and military affairs because of their outstanding features of ultrashort pulse width,higher peak power and broader spectral range.The all-fiber widely tunable ultrashort pulse fiber lasers near 2 ?m have attracted much attentions in recent years as an important branch in the filed of the fiber lasers.As for the diverse tuning devices,multimode interference filters(MMIFs)have many advantages such as high compactness,simple fabrication process and good compatibility with optical fibers.However,all-fiber widely tunable ultrashort pulse fiber lasers near 2 ?m based on MMIFs have not yet been demonstrated.In addition,2 ?m femtosecond pulse fiber laser has the advantage of obtaining higher conversion efficiency mid-infrared supercontinuum generation because of its longer wavelength in the mid-infrared.However,using 2 ?m femtosecond pulse fiber lasers to achieve coherent supercontinuum generation is reported fewer.To solve above problems,the main works during the doctoral years were rsearching novel tuning techniques for 2 ?m femtosecond pulse fiber lasers and using the 2 ?m femtosecond pulse fiber lasers to obtain the coherent supercontinuum generation.Details are as follws:(1)A homemade MMIF with three main transmission peaks was used firstly to obtain a widely tunable mode-locked 2 ?m fiber laser by the bending method.The tunable range of the mode-locked 2 ?m fiber laser was 1919.6~2014.9 nm.Our results showed the designed MMIF could be used to construct all fiber widely tunable mode-locked lasers.(2)A widely tunable 2 ?m ultrashort pulsed fiber laser with a tuning range of 1611~1984 nm was obtained by the Raman soliton self-frequency shift technology.In the experiment,a 1560 nm pulsed fiber laser as the pumped source,a 10 m long silica fiber with the high nonlinear coefficient as the nonlinear media,the widely tunable Raman soliton laser was achieved by optimizing the parameters of the pumped source and high nonlinear coefficient fiber.(3)A 2 ?m femtosecond fiber laser with the 2.1 W average power and 170 fs pulse width was achieved from a Chirped Pulse Amplication(CPA)system.By using this 2 ?m femtosecond fiber laser as the pump source,a fluorotellurite microstructured fiber(MF)as the nonlinear media,the coherent supercontinuum generation from 1.4 to 4 ?m was obtained firstly.