Characterization Of Attosecond Pulses Through Attosecond Streaking Photoelectron Spectrogram

Tracking and controlling the dynamic evolution of matter has always been a goal that scientists in various fields such as physics,chemistry,biology and other fields are engaged in and are still pursuing.In the microcosm,the motion of electrons follows the laws of quantum mechanics and evolves on attosecond timescales.Limited by the huge amount of calculation,the dynamic system that can be completely solved in theory is extremely limited,and more research work is carried out experimentally.With the development of pulsed laser technology,the research objects of scientists have gradually expanded from macroscopic to microscopic,from the rotation and vibration of molecules to the dynamic process of electrons in atoms.At the beginning of this century,the characterization of attosecond bursts and isolated attosecond pulses advanced pulsed laser technology to shorter time scales and also provided direct tools for experimentally studying ultrafast processes.At present,high-order harmonics are mainly generated through gaseous media,and attosecond pulses are measured using attosecond streak cameras.In the attosecond streak camera,the attosecond pulse ionizes the noble gas atom to produce a photoelectron pulse,and the synchronously propagating few-cycle femtosecond laser maps the phase information of the photoelectron pulse to the energy spectrum,thereby realizing the measurement of the attosecond pulse.In the early days,limited by the energy and conversion efficiency of the driving laser,the energy of the attosecond pulse generated in the laboratory was extremely low,resulting in a very small number of photoelectrons,which was very difficult to detect.In recent years,with the further development of femtosecond driven lasers,high-energy,lowrepetition attosecond lasers have begun to enter the field of vision of scientists,and such low-repetition attosecond lasers are difficult to characterize with traditional attosecond stripe cameras.To overcome the low effiency of photoelectron generation caused by the low attosecond pulse energy,the magnetic bottle time-of-flight electron spectrometer was first studied,designed and then built in the lab.For low repetititon rate attosecond laser pulses,a new method is proposed to realize the measurement of attosecond pulses.The relative delay information between the two lasers is mapped into space by the noncollinear propagation of the attosecond pulse and the streaking infrared laser to complete the pulse measurement in one pass without the need for time-delay scanning.The dissertation focuses on the measurement of attosecond pulses,and the main research and innovation contents are as follows:1.A magnetic bottle electron spectrometer is built in the lab,which is aimed to detect the XUV photoelectron energy from the time-of-flight information without spatial resolution.By measuring the width of the high harmonic peaks,the relative energy resolution of this home-built spectrometer is determined to be better than 5%.With this,an isolated attosecond pulse with duration of 159 as are characterized,which is the first report from a home-made high collection efficiency attosecond streak camera in the nation.After optimization of the generation system,high harmonic peaks around110 eV photon energy are observed,indicating the energy resolution better than 3eV@90 eV.2.A non-collinear attosecond streaking scheme is theoretically proposed to apply for the low repetition rate high energy attosecond pulses.With an angle in between the measured attosecond pulse and the streaking IR laser,the time delay between the pulses are mapped into the propagation space along the attosecond laser pulse,which enables the spectrogram to be during one integration with the time delay scan.With this,it is possible to realize realtime attosecond pulse characterization.Spatial-temporal coupling of the non-collinear attosecond streaking setup on the longitudinal cross section is investigated.The time-delay between the non-collinearly propagated two pulses would remain unchanged along one special direction on the plane.It means that,signals can be accumulated along this special direction to enhance the signal-to-noise ratio,which is very important in the detection of photoelectrons pumped by a pulsed laser.It could be a possible method to realize single shot attosecond streaking in the future.With space resolved photoelectron spectrogram,the tilt of the XUV pulse front and the aberrations of the XUV wave front can be calculated.3.In order to meet the need of the spatial resolution from the proposed noncollinear attosecond streak camera,Computer Simulation Technology(CST)has been employed to model,simulate and redesign the magnetic bottle electron spectrometer.By using a pinhole array,adjusting the distance between the pinhole array and the electron source,the spatial resolution of the updated magnetic bottle electron spectrometer can meet the requirement of the proposed non-collinear method.The calculation and the simulation also show that a small iris near the electron source will change the transmission energy spectrum of the electrons.This modification to the transmission spectrum can be calculated in theory to compensate the experimental spectrum.