Study On Picosecond Laser Transmission In Hollow-Core Fiber And Gas Nonlinear Effection

Since the birth of the first anti-resonant hollow core fiber(AR-HCF)in 2011,this new type of fiber with a different conduction mechanism from conventional solid-core fibers has attracted the interest of researchers at home and abroad with its extremely low transmission loss and ultra-wide transmission bandwidth in specific wavelength bands.When filling the hollow core of AR-HCF with gaseous media,the interaction between light and media will be strictly limited to a very small space within the core,and the interaction distance will be greatly increased,providing ideal conditions for the study of light-gas nonlinear interactions.In this thesis,theoretical and experimental studies are carried out around AR-HCF based high peak power picosecond pulse transmission and nitrogen Raman lasers under different atmospheric conditions,which are mainly as follows:Firstly,a model is established regarding the AR-HCF light-guiding mechanism.The mode characteristics of the AR-HCF are simulated and optimized using the commercial finite element simulation software COMSOL,and the stimulated Raman scattering is briefly introduced.Secondly,experimental and theoretical studies of flexible transmission of AR-HCFbased high peak power picosecond pulses under air conditions is carried out.The laser flexible transmission system was built using AR-HCF,which is at low loss in the nearinfrared band,and the stable and lossless transmission of picosecond pulsed laser with peak power in the MW class in the 1064 nm band was successfully achieved.The power,spectrum,pulse width and beam quality of the output laser were measured to demonstrate the spectral broadening and pulse compression caused by the self-phase modulation during the transmission process,and the experimental process was simulated by the Step-by-step Fourier method,and the simulation results were in good agreement with the experimental results.Thirdly,AR-HCF-based picosecond pulse transmission experiments under vacuum conditions were carried out.A high-pressure sealed gas chamber suitable for the high peak power gas stimulated Raman effect was fabricated and evacuated.We have successfully achieved megawatt-level picosecond laser transmission without significant nonlinear effects,and the transmission efficiency is efficient and stable,and the accuracy of the experiment is verified by simulation.Finally,the study of AR-HCF-based nitrogen second-order excited Raman lasers was carried out.The high peak power,high pulse energy 2.1 μm picosecond laser output was successfully achieved using nitrogen Raman wavelength conversion.Using this gas Raman laser source to pump a homemade germanate fiber,a significant broadening of the output spectrum occurred.