Amplification Of Ultrashort Pulse Laser And Generation Of Mid-infrared Femtosecond Pulses

Ultrafast laser has been widely applied in scientific and industrial researches due to its ultrashort pulse duration and ultra high peak power,such as transient process analysis,high-field physics,nano-optics and precise micro-machining.In recent years,mid-infrared femtosecond laser supplies great opportunities as wide requirements in the studies on high-field physics,attosecond seciend,etc.This dissertation focuses on amplification of ultrashort pulse laser and generation of mid-infrared femtosecond pulses.It covers amplifications of all solid-state picosecond laser,amplification of high-power Ti:sapphire femtosecond laser,generation of mid-infrared femtosecond pulses,generation of ultra-broadband super-continuum white-light laser and related instrumental development.The main innovative results are summarized as follow:1,We designed and built a high-power picosecond oscillator and realized 6-W 72.6-MHz 23-ps picosecond mode-locking output under 15-W 808-nm pumping with optical-optical conversion efficiency of 40%.Based on regenerative and travelling-wave amplification,we realized 6-W and 20-W output respectively working at a few hundreds of kilohertz.And 1-kHz 9-mJ high-energy picosecond pulses were realized based on the combination of regenerative and travelling-wave amplification.2,We obtained 510-mW 8.2-fs broadband femtosecond pulses from a Ti:sapphire oscillator based on all-chirped-mirror dispersion compensation.By using picosecond green laser as pump source,we realized self-initiating Kerr-lens modelocking in Ti:sapphire oscillator with output pulse duration of 9.4 fs.Based on chirped pulse amplification,we realized 25-mJ 27.1-fs pulses output with repetition rate of 1 kHz,reaching to 0.92 TW.3,To do theoretical calculation on broadband parametric amplification,we developed broadband nonlinear coupled-wave theory.The calculated results facilitate non-collinear optical parametric amplification to generate broadband mid-infrared femtosecond laser pulses.4,We built an optical parametric amplifier(OPA)containing four stages of non-collinear OPA which is pumped by our home-made high power Ti:sapphire femtosecond amplifier.With 12-mJ pump energy being applied in our experiment,we realized signal pulse amplification with output pulse energy of 1.8 mJ and central wavelength at 1.1 ?m.Meanwhile 521-?J broadband idler pulse generation was realized with central wavelength at 2.86 ?m and spectral bandwidth of 525 nm.The pulse duration of mid-infrared laser was measured to be around 95 fs by means of cross-correlation measurement.Besides,the central wavelength of the mid-infrared laser can be tuned from 2.86 ?m to 3.6 ?m.5,Based on our home-made mid-infrared femtosecond laser system,we realized several individual orders of harmonics generation from one 20-mm MgO-doped chirped periodical poled lithium niobate(MgO:CPPLN)by focusing the mid-infrared femtosecond pulses into it.The white-light laser spectrum ranges from 400 nm to 2400 nm.The output power of the white-light laser was 16.5 mW,corresponding to an up-conversion efficiency of 36.7%.The poled period was designed to offer a broadband reciprocal vector to compensate the phase mis-matching of different orders of harmonics generation.6,We've done instrumental research and development on ultrafast lasers.Targeting on different applications,we designed and developed femtosecond Ti:sapphire oscillator,high-power picosecond laser,picosecond green laser,picosecond travelling-wave amplifier,etc.