Studies On Chirped Pulse Amplification System With High Repetition Rate And Femtosecond Optical Parametric Amplification System

Many investigations of nonlinear optics and ultrafast time-resolved spectroscopyrequire tunable sources with high repetition rate and short pulse duration, andfemtosecond optical parametric amplification is the preferred method for obtainingthe sources. Therefore, in this dissertation we theoretically and experimentallyinvestigate the Ti:sapphire nine-pass chirped pulse amplification (CPA) system at 1kHz, and the femtosecond optical parametric amplification (OPA) system based on aBBO crystal pumped by frequency-doubled pulses of the CPA. The main contents andinnovations are summarized as follows.1. The fundamentals and parameters are discussed in detail for the KLM Ti:sapphireoscillator, the Martinez stretcher, the Ti:sapphire multipass amplifier, and thegrating compressor in the CPA system. The spatial chirp and angular dispersionare also calculated and analyzed theoretically for the KLM Ti:sapphire laser.2. We have successfully built a Ti:sapphire nine-pass CPA system at 1 kHz based onmixed grating Martinez stretcher-compressor, and achieved stable systemoperation. Output pulses with a repetition rate of 1 kHz, a central wavelength of810 nm, a spectrum width of 16 nm, a pulse duration of 66.8 fs, and a pulseenergy of 250 μJ are obtained.3. The broadband type-Ⅰ phase-matched femtosecond OPA based on the BBOcrystal is calculated and analyzed theoretically. The conditions to realize thebroadband parametric operation, the phase matching, the noncollinear angle, thespatial walk-off effect, the temporal walk-off effect, the compensation of groupvelocity mismatch, and the choice of the pump effective beam size areinvestigated. Also analyzed are the BBO crystal frequency-doubling, the whitelight supercontinuum generation, the parametric superfluorescence generation,and the second harmonic generation of the idler beam in the femtosecond OPAsystem.4. The noncollinear parametric superfluorescence is obtained, by pumping thetype-Ⅰ phase-matched BBO crystal with the second harmonic of the Ti:sapphirenine-pass CPA at 1 kHz. The angular distribution of the parametric superfluo-rescence intensity is ascribed to phase velocity and group velocity self-matchingamong interacting pulses. Based on the parametric superfluorescence generation,a broadband type-Ⅰ phase-matched femtosecond OPA system is successfullybuilt, and stable system operation is achieved. The amplified signal beamcontinuously tunable from 530 nm to 810 nm and the idler beam from 810 nm to1.7 μm are obtained. The signal gain bandwidth is 207 nm, which can supportpulses of duration less than 5 fs. And the signal pulse energy is 10.8 μJ and theconversion efficiency is greater than 21%. At the same time, without anyadditional frequency-doubling crystal, the idler second harmonic continuouslytunable from 410 nm to 700 nm is also obtained. The idler second harmonic iscascaded with the idler beam, and its pulse energy is 2.6 μJ and the conversionefficiency is greater than 5%.In conclusion, we have obtained femtosecond pulses continuously tunable from410 nm to 1.7 μm with a self-made femtosecond CPA and OPA system at 1 kHz, andhave achieved world-level machining, and a significant light source is provided formore investigations and applications.