Research On Erbium-Doped Fluoride Pulsed Fiber Laser At ? 3?m

In recent years,with the development of laser technology,and the wide applications in national defense,industry,medical treatment,etc.,the mid-infrared laser has become the top priority of scientific research.Fiber laser is an important development direction in the field of laser because of its excellent characteristics such as good beam quality,high conversion efficiency,good heat dissipation performance and large tunable range of output wavelength.In this paper,based on the erbium-doped fluoride fiber laser as the research object,we have carried out some research work in obtaining the 3?m mid-infrared pulse laser.The research content includes the following three parts:(1)By using a SESAM as modulator in the erbium-doped fluoride fiber laser,we achieve stable Q-switching pulse output.The output wavelength of the laser is 2779nm.When the pump power increases from 0.53 W to 6.7 W,the output power raises quasi-linearly from 5 m W to 487 m W,correspondingly,the repetition rate increases from 26.3 k Hz to 150 k Hz,the width of the pulse decreases from 2.472?s to 410 ns.The maximum pulse energy of the laser is 3.6?J.Then,an MXene(Ti₃C₂T_X)saturable absorption mirror which was fabricated by using inkjet printing technology is used as the modulator and obtained the comparative output parameters which can be compared with using SESAM.The maximum average output power of the laser is 227m W,the narrowest pulse width is 640 ns,and the maximum pulse energy is 1.85?J.(2)Based on nonlinear polarization rotation(NPR)mode-locking technology,a very stable mode-locking operation of erbium-doped fluoride fiber laser is achieved.The maximum average output power of the laser is 358 m W,the narrowest pulse width is 243 fs,the pulse repetition frequency and the maximum pulse energy are 43.2MHz and 7 n J respectively,the peak power is 30 k W,and the experimental results shows that the laser signal to noise ratio reaches up to 78 d B,indicating that the laser works in a very stable mode-locked state.By adjusting the wave plate,the second and third harmonic mode-locked pulses are obtained when the pump power is 2.6 W,and the pulse width of the laser in the second harmonic mode-locked operation is 209 fs.(3)On the basis of the above mentioned NPR mode-locked erbium-doped fluoride fiber laser,a diffraction grating is inserted into the cavity to achieve the broadband tunable output of the mode-locked laser.The output wavelength of the laser is tuned from 2720 nm to 2802 nm,the shortest pulse width is 5.3 ps,and the maximum single pulse energy and peak pulse power are 6.4 n J and 1.2 k W respectively.