| With its advantages of narrow pulse width,high single pulse energy,and high peak power,ultrashort pulse lasers are important tools for applications such as satellite laser ranging,micro-nano processing,and laser surgery,and the important foundation of cutting-edge research such as mid-infrared OPCPA,optical frequency comb,and attosecond generation.With the rapid development of laser technology,ultrashort-pulse solid-state lasers based on crystal material can provide pulse energy on the order of Joules,peak power on the order of watts,and beam quality near the diffraction limit.Due to the thermal effect of crystal materials,the reported repetition rate is low and the average output power is limited.Ultrashort-pulse fiber lasers can output hundreds of watts of average power due to their excellent heat dissipation performance and high gain.However,due to the nonlinear effect in the fiber,the reported repetition rate is high and the pulse energy that can be obtained by a single fiber stays on the order of hundreds of microjoules.In recent years,thanks to the stability of fiber lasers and the high energy of solid-state lasers,the technical solution of using mode-locked fiber lasers as the front end and crystal-based solid-state amplification has been widely adopted by research institutes and companies,and has developed rapidly.Single-crystal fiber is a gain medium between fiber and rod crystal,with a diameter of less than 1 mm.The very low roughness of its outer surface allows the pump light to be transmitted within the single-crystal fiber.Due to the waveguide function of the pump light,the pump light is evenly distributed in the single-crystal fiber with a high intensity.In recent years,single-crystal fiber has received extensive attention and research due to its large mode field area which is larger than fiber,its excellent heat dissipation performance which is better than rod crystal,and its high Raman threshold which is higher than quartz glass,providing new ideas for the development of amplifiers.This thesis focuses on the research of polarization-maintained all-fiber passively mode-locked oscillators and high-repetition-rate Yb:YAG single-crystal fiber regenerative amplifiers.The applications of regenerative amplifiers in satellite laser ranging and mid-infrared 2.8 ?m simulated Raman pulses generation are introduced and explored.The research work of this thesis is mainly divided into the following aspects:1.Theoretical and experimental research on polarization-maintained all-fiberstructured passively mode-locked oscillatorTheoretically,the influence of fiber dispersion on the characteristics of modelocked pulses is analyzed;the mode-locking mechanism of nonlinear amplifier loop mirrors and nonlinear polarization rotation based on polarization-maintaining fibers is studied.It was found that the transmission of light in the fast and slow axes of polarization-maintaining fibers can form a virtual saturable absorber caused by the nonlinear effect of the fiber.Experimentally,in the 1.5 ?m,using a "ring cavity" and "figure-of-9 cavity" to build a polarization-maintained all-fiber-structured passively mode-locked oscillator,respectively,achieving a repetition frequency of 25 MHz,a soliton pulse width of 650 fs,and a repetition frequency of 15.4.MHz,soliton pulse width of 700 fs;in the 1.03 ?m,a polarization-maintained all-fiber-structured passively mode-locked oscillator was built using a "figure-of-8 cavity" to achieve a dissipative soliton with a repetition rate of 21.1 MHz and a pulse width of 5.3 ps.2.Experimental research on high repetition rate Yb:YAG single crystal fiber regenerative amplifierTheoretically,different gain materials based on ytterbium ions were analyzed,fiber amplifiers and solid-state amplifiers were compared,and the advantages and disadvantages of each gain medium were weighed.In the end,Yb: YAG single-crystal fiber was selected as the amplification gain medium.The cavity of single crystal fiber regenerative amplifier was calculated,and the multi-pulse energy and period doubling effect of regenerative amplifier at high repetition rate were numerically simulated.Experimentally,the seed pulse with a pulse energy of 190 p J was regeneratively amplified to avoid the unstable factors caused by complex laser systems and longdistance transmission as much as possible.Finally,the average power of 21 W and 10.4 W were obtained,respectively,at the repetition rate of 200 k Hz and 100 k Hz.The pulse width can be compressed to 1 ps by using grating pair.3.Application of high-repetition-rate regenerative amplification laser system in satellite laser rangingThe high-energy pulse output by the regenerative amplifier is an excellent light source for satellite laser ranging.Satellite laser ranging based on high-repetition-rate regenerative amplification laser system is on the cutting edge of this field with the advantages of high sampling rate and low statistical error.Through the development of high-repetition-rate Nd:YVO4 regenerative amplification laser system,the satellite laser ranging based on high repetition rate was explored at the Shanghai Observatory.Experimentally,a 1064 nm picosecond pulse output with a tunable repetition rate of 100 k Hz to 1 MHz was achieved,and an average power of 14 W was achieved at different repetition rates.After temperature phase matching,the 532 nm green light with an average power of 9.4 W was obtained,and the frequency-doubling efficiency was 67%. |
PDF Full Text Request