The Research On Wavelength-Tunable Pulsed Fiber Lasers Around 3?m

In recent years,tunable mid-infrared pulsed fiber lasers emitting at around 3?m with high energy and high peak power have attracted tremendous attention due to their wide range of potential applications in laser surgery,industry materials modification and nonlinear frequency conversion.In this thesis,we have studied the tunable pulsed fiber lasers emitting at around 3?m,and the main research contents are as follows:?1?Using Fe²⁺:ZnSe crystal as a saturable absorber,the high-power and high-energy tunable passively Q-switched Er³⁺-doped fiber laser is realized.In this laser,the pulses dynamics at different pump powers are studied.At the highest pump power,the Q-switched pulses with the highest tunable spectral range of 90 nm?2762.5 nm²852.5nm?are achieved.In addition,within 76.1 nm spectral range,the average output powers are over 4 W,and can reach as high as 5.16 W at 2811.7 nm.Moreover,the highest pulse energy of 27.7?J is achieved at 2834.6 nm.Until now,the average power and pulse energy are the recorded levels in 3?m passively Q-switched fiber lasers.?2?Using semiconductor saturable absorption mirror?SESAM?based Q-switched Ho³⁺/Pr³⁺codoped ZBLAN fiber as a seed source,the dynamics of pulses amplified by the master oscillator power amplifier?MOPA?structure are studied.When the launched power of the master oscillator is at 93 mW,the average output power of amplified Q-switched pulses reaches 798 mW at a slope efficiency of 23.7%,which reaches the recorded level in Q-switched Ho³⁺/Pr³⁺codoped ZBLAN fiber lasers.?3?The passively mode-locked Ho³⁺/Pr³⁺codoped ZBLAN fiber laser based on SESAM is realized,the central wavelength is 2869.8 nm,with a 10.03 MHz repetition rate and 18 ps pulse duration,and the highest output power is 184.3 mW.?4?Using a blazed grating as the wavelength selector,a tunable passively mode-locked fiber laser based on SESAM is realized at around 3?m.The fiber laser exhibits stable continuous-wave mode-locking operation over a wide wavelength tuning range of34 nm?2842.2 nm²876.2 nm?,with a 10.17 MHz repetition rate and 22 ps pulse duration.Moreover,maximum average output power of 127.7 mW and the corresponding pulse energy of 12.56 nJ are achieved.