Focusing Characteristics And Application Of Tightly Focused Vector Ultrashort Pulse Light Field

With the rapid development of ultra-fast optical technology,various types of ultrashort laser pulses have been obtained,such as radial and azimuthally polarized.In the aspect of laser development,one is to continuously improve the peak power of ultrashort and ultrafast laser,and the other is to continuously shorten the pulse duration.The current research is limited by the super-resolution diffraction and the accelerated light field intensity of the accelerator.The maximum energy that people can accelerate particles to and how small the diffraction limit focal spot can be obtained are unknown.In this paper,the focusing characteristics and the interaction effect with electrons of the tightly focused vector ultrashort pulse are studied.In order to describe the space-time characteristics of this tightly focused ultrashort pulse.The article uses the Complex-source/sink model(CSSM)and the Richards Wolf diffraction integral theory(RWT)to deduce the expressions of tightly focused radially polarized,linearly polarized,and azimuthally polarized electromagnetic fields in the focal plane.The dynamic focusing characteristics of radially polarized and linearly polarized ultrashort pulses as well as the interaction effects of tightly focused azimuthally polarized pulses with electrons are studied.When studying the dynamic focusing phenomenon of radial polarization and linear polarization ultrashort pulses in the focal plane,convergence and divergence motion halos can be observed.Moreover,CSSM can simulate the super-resolution focusing spot by changing only the waist parameters.At the same time,the key convergence angles which can significantly observe the convergence and divergence focusing phenomena are also studied.These studies can be applied to the field of particle manipulation and acceleration.In this paper,the interaction effect of tightly focused vector ultrashort pulses on electrons in vacuum is studied by numerically solving the relativistic Newton Lorentz equation.Taking into account the radiation reaction force,it is found that the tightly focused azimuthally ultrashort pulse can accelerate electrons with initial kinetic energy less than 1MeV to hundreds of MeV,and can confine the electrons to a certain range in the vertical laser propagation direction(lateral)Hundreds of femtoseconds.The maximum kinetic energy gain of the electron accelerated by the tightly focused azimuth polarized pulse is related to the initial kinetic energy,position,emission direction of the electron,and also is related to the phase,intensity,and beam waist of the pulse.The time for the few-cycle pulse to confine the electrons laterally in the accelerating process is three times longer than that of the sub-cycle pulse.The phenomenon of the red-shift and blue-shift of the center frequency of the electron radiation spectrum with the parameter E₀value is found.These studies provide a way to limit the range of electron movement while gaining electron acceleration.