Study On Low Repetition Erbium-doped Short Pulse Fiber Laser With Long Cavity

Short pulse laser source with low repetition frequency are widely required in mechanical processing,biomedical detection,lidar,photoelectric detection,and other fields,especially in recent years,along with the growing potential applications of lidar in unmanned pilot,intelligent robots,surveying and mapping measurement.Low frequency high peak power nanosecond laser features low cost,eye safe,compact structure and easy maintenance become the research hot spot.Combined with advantages of fiber laser including compact structure,wide wavelength range,high peak power and easy maintenance,this paper regarding long cavity pulsed fiber laser as the technical scheme of the low frequency short pulse laser source,according to the requirements of lidar,from experimental and theoretical study of low repetition frequency erbium doped fiber laser with long cavity,eventually realized the output of1.5μm low frequency high peak power nanosecond pulse.The main content of this thesis include:1.Introducing the implementation mechanism of long cavity pulsed fiber laser,the development and research progress of the long cavity pulsed fiber laser.Studying the energy level structure of Er³⁺,structural characteristics of SESAM,optical fiber dispersion and nonlinear effect of cavity and their effect to the pulse formation from the perspective of theory.2.Based on experiment platform of SESAM pulsed fiber laser,output pulse characteristics of low repetition short pulse Er³⁺doped fiber laser with long cavity were studied.Linear and ring cavity experiment device and two kinds of different coupling device based on SESAM were introduced.In experiment,by changing the length of extending fiber from 300m to 2267m,output characteristic of conventional soliton output from the laser are analyzed;the process from soliton to noise-like pulse is observed when increasing pump power;by changing cavity dispersion and nonlinearity respectively,output pulse characteristics of different conditions are analyzed.3.In the experiment of laser ranging validation,the nanosecond noise-like pulse from the erbium-doped ring fiber oscillator with long cavity based on SESAM is regarded as seed,delivers laser output with repetition rate of 660 kHz,pulse width of 2.2 ns,center wavelength of 1564 nm,average power of 1.31 W and peak power of 0.9 kW after amplification,finally a set of simple lidar test device for laser ranging validation experiments of the light source was built.