Study On The High Power CW And Q-switched Pulse Fiber Lasers In Mid-IR

In recent years,high power and high energy fiber lasers operating at 3?m wavelength region have aroused the wide attentions of researchers because of their wide applications in laser surgery,material processing,countermeasures,scientific research etc.On the other hand,compared to other types of lasers,the fiber based lasers have exhibites a series of merits e.g.,compactness,great beam quality,excellent heat dissipation,high efficiency and good flexibility.In this dissertation,our study mainly focus on the high power CW fiber lasers and the high energy pulse fiber lasers at 3?m based on above superiority.The main research achievements can be divided into following three sections:?1?Based on the transition process of the heavily Er³⁺-doped ZBLAN fiber,a comprehensive numerical model mainly involving rate equations,power evolution equations and the boundary conditions capable of describing the heavily Er³⁺-doped ZBLAN fiber laser was built.A set of significant parameters including gain fiber length,dopant concentration,output coupling and pump wavelength were optimized taking the slope efficiencies,threshold and thermal dissipation all into consideration.?2?Using a 4.1m Er³⁺-doped ZBLAN fiber as gain fiber,the heavily Er³⁺-doped ZBLAN fiber laser was constructed and its performance was investigated.At last,a maximum output power of 7.11 W at the wavelength of 2802 nm was achieved,whose fluctuation range is 4.3%.The slope efficiency reached 36.06%,more than 34.3% of the stokes limit.?3?Firstly,a SESAM based passively Q-switched Er³⁺-doped ZBLAN fiber laser was built and stable Q-switched pulses was observed.The pulse characteristics under different pump power were studied.The pulses with maximum pulse energy of 3.52?J,average power of 0.252 W,repetition rate of 71.43 kHz,and pulse duration of 1.7?s at the wavelength of 2786.8nm were obtained.Secondly,a MOPA?Master Oscillator Power Amplifier?system based on heavily Er³⁺-doped ZBLAN fiber was constructed,and the Q-switched pulses was immited into the MOPA system.Then,we explored the performance of the MOPA system at different laser reflections of the fiber end.Finally,the amplified pulses with maximum average power of 4.2W,pulse energy of 58.87?J,pulse duration of 2.29?s,repetition rate of 71.73 k Hz,slope efficiency of 30.79% at the wavelength of 2786.8nm were obtained.