Abstract
Along with the observation of smaller and faster objects, requirements of the light source used on observation are more demanding. So far, linearly-polarized high harmonics generation (HHG) has been used on many experiments such as resolving nanostructure of materials, molecules dynamics, pump-probe experiment and so on. However, for the magnetic materials and chiral compounds, they are very sensitive to circularly polarized light instead of linearly polarized one. Until now, there are few approaches to produce circularly-polarized attoseocnd (as) pulses, but all of them demonstrated so far are limited to as pulse trains, which limit the temporal resolution of the pump-probe experiments. Isolated circularly-polarized as pulses have been proposed in theory, but our team for the first time succeeded in producing isolated circularly-polarized as pulses and characterized its properties in details in this thesis. In the experiment, we combined two counter-rotating circularly-polarized solid-state white light laser (MPContinuum / MPC) to produce HHG, which generated two counter-rotating polarized EUV beams with the same ellipticity simultaneously. By observing the supercontinuum spectrum, spanning from 25eV to 40eV, measured by EUV spectrometer and the trace of an E-field autocorrelation, indicating that those pulses are temporally isolated. Most importantly, we have built one EUV polarimeter which can unambiguously analyze the helicity and ellipticity of those two isolated as beams with ellipticity of +0.9 and -0.93 ( + : represents positive helicity, -：negative helicity). By further extending the non-collinear geometry for HHG, we are even able to convert the ellipticity of fundamentals to that of HHG, while keep the same conversion efficiency.