Generation And Amplification Of Ultra-broadband Femtosecond Pulses And Carrier-envelop Phase Offset Stabilization

As a frontier field of laser technology,ultrashort pulse laser has gradually developed into a fundamental science in modern science and technology,greatly promoting the rapid development of related high-tech and interconnections,and has made a series of significant breakthroughs in the application of strong field physics,biochemistry,and micro-and nano-scale three-dimensional microstructure preparation.Among the ultrashort pulse laser technologies,obtaining high power ultra-broadband femtosecond lasers,broadband femtosecond laser pulse amplification and control of the carrier envelope phase shift of ultra-broadband femtosecond pulses are several important research directions.For these aspects,this thesis carries out experimental research on the design of ultra-broadband femtosecond lasers,experimental research on the amplification and compression of broadband femtosecond lasers,and research on the control of the carrier envelope phase shift,which becomes an important driving light source for conducting experiments on the generation of high harmonic and attosecond pulses.The main research works and the innovative results are summarized as follows:1.The theoretical analysis and simulation of the global dispersion management of the oscillator,amplifier and compressor are presented.The theoretical derivation of the Martinez stretcher and compressor,which are commonly used in CPA systems,is carried out using the ray-tracing method.The analytical expressions for the accurate calculation of the dispersion introduced by each unit module are obtained,and the dispersion characteristics of common dielectric materials and the advantages and disadvantages of different dispersion compensation methods are analyzed,which provide the theoretical guidance and design basis for subsequent chirped-pulse amplification experiments.2.The experimental study of a high average power Kerr-lens mode-locked femtosecond Ti:sapphire laser was carried out considering the realistic demand for average power of femtosecond light sources in some applications.A high average power output of 2.1 W was obtained at a pulse repetition frequency of 75.5 MHz pumped by a continuous laser of 10 W.The spectrum of 12 nm(FWHM)and the pulse duration of 96 fs was measured.3.In response to the low output power of octave-spanning Ti:sapphire oscillators,an experimental study of a megawatt peak power octave-spanning sub-10-fs Ti:sapphire oscillator was carried out.The specially designed double-chirped mirrors were used to compensate for material dispersion and fused silica plates were inserted into the oscillator to precisely balance the dispersion as well as greatly enhance the self-phase modulation effect.The octave-spanning spectrum covering 550-1100 nm and average power of up to 880 mW were directly obtained at pulse repetition frequency of 80 MHz.The pulse duration as short as 6.6 fs was measured,corresponding to about 2.4 optical cycles.To our knowledge,this is the highest average power ever obtained from an octave-spanning Ti:sapphire oscillator.4.The 0-f method for measuring the carrier envelope phase shift has the advantages of the higher long-term stability,relatively low cost and low noise introduced by the measurement,but the method requires an octave-spanning or quasi-octave-spanning spectrum femtosecond laser,which is quite difficult to build.We have carried out an experimental study on the measurement and control of the envelope phase shift of a high average power sub-10-fs Ti:sapphire oscillator based on a narrow band spectrum.A sub-10-fs Ti:sapphire oscillator was firstly constructed with the average power of 660 mW at 4.5 W pump power at a pulse repetition frequency of 170 MHz.The spectrum covering 650-950 nm and the pulse duration of 9 fs were obtained.The carrier envelope phase shift signal with a signal-to-noise ratio of 44 dB was then measured using a single PP-MgO:LN crystal based on the self-difference frequency method.90-minute locking of the CEO was realized,The integrated phase noise of 138 mrad in the 1 Hz to 1 MHz range was achieved,corresponding to a 63 as time jitter(central wavelength 790 nm).5.A ring Ti:sapphire regenerative amplifier was designed and constructed.Steady running amplifier had been achieved at the repetition rate of 1 kHz.The amplified output power of 3.3 W was obtained under the pumped power of 16 W.The pulse duration of 31 fs was measured by the autocorrelator.Considering the large thermal lens effect existed in Ti:sapphire amplification,a novel multi-pass pumped thin-disk Ti:sapphire regenerative amplifier was designed and constructed.Based on the scheme of chirped-pulse amplification,the output power of 1.8 W was attained under the pumped power 16 W.After the compressor,output power of 1.45 W and pulse duration of 38 fs were attained,corresponding to the compression efficiency of 80%.The beam quality M2 around 1.1 was measured.Although experiment shows that the thin-disk Ti:sapphire amplified scheme is beneficial to improve the beam quality of the amplifier,the multi-pass pumped structure and the welding scheme of thin-disk Ti:sapphire needs to be optimized to obtain the higher output power and the better beam quality at the same time.