Study On All Fiber TM³⁺-Doped Pulse Laser And Amplifier

2μm lasers which locate in atmospheric transmission window and eye-saferange, are being widely used in the field of laser remote sensing, medical andmaterial processing. In addition,2μm pulsed lasers are excellent pump sourcesobtaining Middle-infrared3⁵μm optical parametric oscillation lasers. Comparedwith2μm solid lasers, all-fiber pulsed Tm³⁺-doped fiber lasers have advantages ofcompact structure and strong anti-interference capability. However, due to thelimition of fiber device technology, all-fiber pulse Tm³⁺-doped fiber lasers andamplifiers are few reported. This thesis investigates the band pumped gain-switched Tm³⁺-doped fiber laser characteristics theoretically and experimentally,in which all-fiber2μm pulse Tm³⁺-doped laser and amplifier with the pulse laseras injected seed laser are taken as the basic starting point. The outputcharacteristics of pulse Tm³⁺-doped fiber amplifier are investigated in detailed.We expect to make some contribution to the development of related fields.Theoretically, the band-pumped Tm³⁺-doped fiber laser rate equation modelis established with power overlapping factor and Stark energy level considered.The expressions of inversion population, intracavity photon density, thresholdenergy, and pulse extraction efficiency are derived. Time characteristic of upper-level population, cavity photo density, pulse built-time and pulse width arediscussed on this basis meanwhile. In addition, the traveling-wave equations ofTm³⁺-doped fiber laser are also established. The change of upper level populationand cavity photo density along fiber axis are discussed, as well as the extractableenergy and output power. Secondly, taking into account the influence of ASEabout LMA highly doped fiber amplifier output characteristics, we established theTm³⁺doped fiber amplifier rate equation model and studied the steady-stateamplification and pulse amplification numerically. In steady-state mode, the upperlevel population, pump light and ASE light distributing along the fiber axis areinvestgated, and the output characteristics of amplifier are also investigated indifferent injection power. In pulse amplification mode, the upper level population,the pump light and ASE light distributing along the fiber axis are investgated, therelationship between output pulse energy, storage energy and repetition rate arealso analysed, establishing a good foundation for next experimental study.Experimentally, the1558nm two stages Er³⁺doped pulse amplifier wasstudied in detailed. The output energy, ASE power and output spectra weremeasured and analysed. The relationship of ASE and amplifier output power wasalso discussed. The experiment of large core double-cladding FBG inscribed by 800nm fs laser was investigated. The output power variation during the process ofinscribing FBG was recorded. Combined to the Tm³⁺-doped fiber laser rateequation model, the FBG reflectivity and the core refractive index modulation areanalysed. The experiment of single mode FBG inscribed by UV exposure methodwas investigated, and the spectra characteristic are measured by a broadband lightsource and high-resolution OSA. The experiment of all fiber gain-switched Tm³⁺-doped fiber laser was investgated, in which the laser output power, pulse widthand pulse built-time were studied. Secondly, the2054nm Q-switchedTm,Ho:YVO4pulse laser was coupled into the core of LMA Tm³⁺-doped fiber.The output power, conversion efficiency, output wavelength, beam quality factor,spot distribution and amplified pulse waveform distortion were all discussed indetailed. The gain-switched1940nm laser was injected into highly Tm³⁺-dopedfiber as a seed laser. The output characteristics of all fiber pulse amplifier werestudied, the output power, peak power, output wavelength, beam quality factor,spot distribution, and the amplified output pulse waveform parameters weremeasured and analysed. The ASE light, parasitic oscillation and self-pulsing effectwere the main reason which influence the amplifier output.