Researches On 2?m Mode-locked Thulium-doped Fiber Laser And Raman Shift Solitons

2?m fiber lasers have been massive applications in both commercial and academic field,such as atmosphere monitoring,medical treatment,military radar.As a result,it's of great significance to study 2?m fiber laser.Herein,five main chapters based on 2?m fiber laser have been listed below:1.The application and significance of 2?m fiber lasers have been mianly discussed,followed by some background researches on 2?m fiber lasers as well as 2?m raman soliton fiber lasers.2.The mechanism and types of mode-locking have been introduced,with an emphasis on saturable absorption mode-locking;After that soliton pulse,dispersion-managed pulse,dissipative soliton pulse are listed and their mechanism and typical features have been discussed.3.The theory of raman soliton frequency shift including raman scattering and soliton effect is mainly discussed;basing on the theory,a numerical simulation with nonlinear schrodinger equation have been made,with the controlled parameter consisting of peak power,pulse width,and fiber length.The conclusion is with higher peak power,shorter pulse width and longer fiber length,the raman soliton will shift further.4.Three fiber lasers including soliton pulse fiber laser,dispersion-managed soliton pulse fiber laser and dissipative soliton pulse fiber laser have been set up.The soliton pulse fiber laser output 7.8mW laser with the pump power of 200 m W,and its spectrum centered at 1958 nm with broad spectrum width of 6nm,its frequency is 55 MHz with SNR of 58 dB and pulse width of 725 fs.To further compressed pulse width,the dispersion-managed soliton pulse fiber laser is set up with 3.6m-long UHNA4 joining the cavity,and its output power is 3mW when the pump power is 515 mW.Its center wavelength is 1931 nm with spectrum width of 32 nm.With 4mlong UHNA4 joining the cavity,the dissipative soliton pulse fiber laser output 2mW laser with the pump power of 576 m W,and its spectrum centered at 1930 nm with spectrum width of 52 nm,its frequency is 23.3MHz with SNR of 55 dB.After 10m-long SMF-28 e,the dissipative soliton pulse is compressed to 170 fs of pulse width.Increasing pump power until output power is 4.85 mW,the pulse is compressed to 152 fs pulse width with 0.2nJ pulse energy.This is so far the shortest pulse width and highest pulse energy achieving in CNT mode-locking fiber lasers.5.Seeded with the soliton fiber laser,and amplified with two stage amplification,the raman soliton fiber laser is successfully set up.The tunable wavelength ranges from 2000 nm to 2321 nm with all pulse width below 150 fs,and the max output power is 945 m W,with the max energy of 17 n J.The highest conversion efficiency is 96% according to spectrum integral.On this condition,a long bandpass filter placing after the fiber laser,a single soliton fiber laser is fabricated.The soliton can shift from 2000 nm to 2325 nm with pulse width below 150 fs without higher level soliton distracting energy.Last,We come up with the method utilizing the measured power after bandpass filter to calculate the conversion efficiency foe the first time.This method is much more accurate,and the max conversion efficiency is 86%.