| Ultrashort pulses with high power,high energy and high beam quality play very important roles in medical cosmetology,eye safety,laser radar and other fields.Among them,ytterbium-doped crystal lasers have become the focus of research in recent years due to their excellent laser performance in the 1 μm band.This thesis investigates ytterbium-doped solid-state lasers and fiber lasers.The main content of the thesis is as follows:The research background and research significance of ytterbium-doped solid-state lasers are introduced.The research progress of solid-state lasers includes Yb: GYSO,Yb: LSO and new ytterbium-doped laser crystals in recent years are researched.The Yb-doped fiber laser system is summarized.The research background,research significance and research progress of ytterbium-doped fiber amplifier are introduced.Systematic laser experiments on Yb: GYSO and Yb: LSO laser crystals are carried out.Yb: GYSO crystal is used as the gain medium,three resonant cavity types are designed and built.The stable Q-switched pulse output is realized by using SESAM as the saturable absorber,and the experimental results are compared and analyzed.Based on the spectral characteristics of Yb: GYSO crystal,a single-wavelength to threewavelength switchable Q-switched pulse output is realized by using a spatial aperture.Yb: LSO crystal is used as the gain medium,four different types of SESAMs as saturable absorbers,a W-shaped resonator is designed and built.Systematic study the output characteristics of lasers,including laser spectrum,average output power and pulse sequence.In Yb: LSO solid-state laser,the output of dark pulse,bright-dark pulse pair and bright pulse Q-switched pulse are obtained for the first time,and analyze their spectra respectively.The bidirectional pumped ytterbium-doped fiber amplifier is experimentally studied.The working principles of fiber amplifiers under three pumping configurations are theoretically expounded.In the experiment,firstly,a mode-locked fiber laser based on spatial light NPR is built as the seed source,and the laser amplifier is built using a large mode-field area ytterbium-doped fiber.The output pulse characteristics of the amplifier stage under the three pumping configurations are compared.Using bidirectional pumping,the evolution of dissipative soliton pulses to noise-like pulses is obtained by controlling the injection power of forward and backward pumping.The intermediate states of dissipative solitons and noise-like pulses are observed by autocorrelator.The autocorrelation traces of them show that the sidebands had oscillating structures. |
