～2 μm All-Fiber Chirped Pulse Amplification And Optical Parametric Oscillation

Mid-infrared lasers have very broad and crucial applications in atmospheric detection,biomedicine,defense and military fields.Compared to traditional lasers,optical parametric oscillators(OPOs)can output longer laser wavelengths and achieve higher power mid-infrared laser outputs,making them one of the significant research hotspots in the mid-infrared laser field.Commercialized PPLN-OPO based on quasi-phase matching technology has been achieved,with most of them using a ～1 μm pumping scheme to obtain ～1-4 μm parametric light output.To achieve higher average power and longer wavelength range of PPLN-OPO output,a ～2 μm pumping PPLN-OPO scheme has been proposed.However,in the existing studies,only a few works have successfully implemented the ～2 μm tuned Q-operation laser pumping scheme.It is worth noting that the research direction of ～2 μm ultrashort pulse pumping has not been reported so far.As the result,it is an urgent need to prove the feasibility of this option.To resolve the above issues,this thesis conducts a study on ～2 μm ultrashort pulse pumping PPLN-OPO as follows.In this thesis,focusing on the perspective of fiber laser-pumped PPLN-OPO,experimental studies were conducted in two parts,including:(1)high-power ～2 μm allfiber chirped pulse amplification(CPA)experimental research and(2)～2 μm ultra-short pulse laser pumped PPLN-OPO experimental research.First,this thesis described the optical soliton theory,the self-phase modulation theory,the evolution of the pulse under the joint action of SPM and GVD,Numerical simulations of the ～2 μm all-fiber CPA structure were also conducted to reveal the feasibility of this CPA system design.In addition,the basic theories of OPO were introduced: light interaction with nonlinear media,three-wave coupling equation,and quasi-phase matching.In the experimental part,a ～2 μm conventional soliton source and its CPA system were built.The seed source was optimized by hybrid mode-locking,and an average power of 3.49 W and a peak power laser output of 6.69 k W were obtained by CPA system.To further improve the CPA power level,the spreading soliton source was built by dispersion management.It solved the negative effect of Kelly’s sideband on optical amplification.Subsequently,the dispersion management and amplifier of the original CPA system were optimized to obtain an average power of 19.72 W and a peak power laser output of 0.573 MW,which means that the power level of the CPA system has been increased from the kilowatt level to the megawatt level.Finally,the resonant cavity of the PPLN-OPO was designed and built.The PPLN-OPO system was experimentally constructed by two CPA systems,and obtained red sum frequency light of 662.9 nm and watt-level frequency doubling light of992 nm.These results demonstrated the feasibility of ～2 μm ultrashort pulse pumping PPLN-OPO.Unfortunatly,the 3-5 μm parametric light output was not measured.But the experimental analysis and optimization and solutions were proposed in this thesis.Overall,this thesis provided a reference scheme for the subsequent ～2 μm ultrashort pulse-pumped PPLN-OPO.Simultaneously,it provided meaningful ideas for extending the parametric optical wavelength of PPLN-OPO and improving its conversion efficiency.