Generation And Control Of High-Average Power Ti:sapphire Femtosecond Lasers And Few-Cycle Laser Pulse

High average power femtosecond laser have extensive applications in physics,chemistry,biomedical,micro-processing and so on.In order to obtain a high average power,short pulse,stable performance femtosecond laser,theoretical and experimental studies of dispersion management and energy amplification in chirped pulse amplification system were carried out in this dissertation.For attosecond laser pulse generation,experimental progress in carrier-envelope phase stabilization of the few-cycle laser pulse was also demonstrated.The main research works and the innovative results are summarized as follows:1.Aiming at solving the problem of dispersion management in CPA system,we theoretical analysized the influence of group delay dispersion(GDD)and third-order dispersion(TOD)on the pulse profile.We systematically investigated the dispersion arisen from the Martinez stretcher,grating pair compressor and materials.Program for global optimization of entire system dispersion was carried out,which provide a very useful instruction for the next step of high power ultrafast laser design.A compact aberration free stretcher based on concentric reflective structure was proposed and constructed.Compared with Martinez and Offner stretcher,it produces less residual group delay and is very suitable for TW level amplification laser system.2.A compact Ti:sappphire regenerative amplifier(RGA)with a thermal insensitive cavity was demonstrated by compensation of thermal lens through adjusting the cavity mode size.The amplified power of 6.5W was obtained under the pump power of 20 W at 1kHz using this cavity.The amplification efficiency was up to 32.5%.The theoretical analysis and experimental results show this cavity developed in this work is very suitable for high power and high efficient amplification of femtosecond Ti: sapphire pulses.3.Based on the study of high efficiency cavity mode adjustable RGA,we designed and built a two-stage high average power femtosecond Ti:Sapphire amplifier.Pumped by 88 mJ kilohertz 532 nm Q-switched laser,the Ti:Sapphire was cooled to 125 K using a liquid-nitrogen Dewar to reduced the thermal-lensing.Maintaining a balance between the thermal lens focusing and the Gaussian beam divergence,we constructed a four-pass bow-tie amplifier.The laser delivered 22.8mJ,25.4fs pulses at 1kHz repetition rate.4.The generation of isolated attosecond pulses could be driven by carrier-envelope phase stable,few-optical-cycle pulses.On the basis of a commercial nine-pass pre-amplifier,webuilt a two-pass secondary amplifier to boost the energy from 1.8mJ to 5mJ by using a20 m J greenlight Q-switched laser as pump source.The shortest pulse duration of 27 fs is obtained with the output energy of 3.9m J after compression.Through the differentially pumped hollow-core fiber,the broadened spectra covered from 400 nm to 950 nm,and subsequently compressed pulse with duration of 4.6fs had been obtained.The beam fluctuation were stabilized by employing a feed back beam lock system.Separated CEP locking for the oscillator and amplifier were carried out by using 0-f and f-2f self-referencing methods.5.A drawback of traditional hollow fiber pulse compression is its energy scaling.We demonstrated a technique of using multiple thin plates of fused silica to generate an white-light continuum spanning more than one octave.By strategically placing seven pieces of 100?m thin solid plates near the focused waist of incident 0.8mJ,25 fs laser pulses,we had obtained an octave-spanning spectrum which covered from 460 to 950 nm.Finally,7.1fs pulses were generated after compensating the dispersion by chirped mirrors.We performed high harmonic generation experiment with the intense ultrashort pulses.