Mode Locking And Spectral Broadening Of High Average Power Femtosecond Solid-State Laser

Benefiting from the rapid development of the high-power and high-brightness laser diodes,solid-state lasers have achieved great progresses and been widely applied in the field of industry,laser communication,biomedicine and the basic research and so on.It is of great significance to develop new solid-state lasers with higher output power and shorter pulse duration.Pumping by fiber laser is a good choice for bulk gain media to obtain high power Kerr-lens mode-locking?KLM?operation.Another way is based on thin-disk technology and mode-locked thin-disk oscillators.Because of the excellent thermal conductivity,thin-disk oscillators could deliver extremely high-power pulses with excellent beam quality,which result in people's more and more attention on the thin-disk oscillators.This thesis focuses on high power solid state lasers,including high power and high efficiency Yb:GSO laser pumped by fiber laser,and high power thin disk oscillators by semiconductor saturable absorber mirror?SESAM?and KLM mode-locking.Besides,based on KLM Yb:YAG thin disk oscillator,some applications,such as second harmonic generation?SHG?,supercontinuum generation and spectral broadening,were performed.The main work and innovation of this dissertation are summarized as follows:1.The spectral properties of Yb:GSO crystal were studied and the properties of 980nm fiber laser and 980 nm laser diode were compared.Pumped by a 980 nm fiber laser,SESAM and KLM Yb:GSO oscillators were achieved.Particularly,efficient KLM Yb:GSO oscillator was obtained with the maximum output power of 4 W and pulse duration of 249 fs?In this case,the corresponding optical-to-optical efficiency was about 50%,which is the highest efficiency obtained from high power KLM bulk oscillators.2.A high power SESAM mode-locked Yb:YAG thin disk oscillator was demonstrated.Pumped by a 940 nm fiber-coupled laser diode,12.1 W mode-locked pulses were ob-tained with pulse duration of 698 fs at the repetition rate of 57.43 MHz.Measurement showed that the beam quality was close to the diffraction limit.Corresponding results have been published in Chinese Physics B 25,054205?2016?,and have been also applied for a national invention patent?201510260423.1?.3.High-power KLM Yb:YAG thin-disk oscillator was developed.15-W,272-fs pulses were realized at a repetition rate of 86.7 MHz with an additional Kerr medium and a 2.5 mm hard aperture in the cavity.The measured RMS fluctuation is less than0.4%.Corresponding results have been published in Chinese Physics B 25,094207?2016?,and have been also applied for a national invention patent?201510317077.6?.4.Based on a 247-fs,11 W KLM Yb:YAG thin disk oscillator,we performed the second harmonic generation,supercontinuum generation and spectral broadening ex-periments.In SHG progress,by a 1.7-mm-long LiB₃O₅?LBO?crystal,the SH laser power of 5 W was achieved with the corresponding optical-to-optical efficiency of 60%?In supercontinuum generation,high power supercontinuum spectra were obtained.In spectral broadening experiment,after a broadening and compression stage,2.6 W,102fs pulses were obtained.