Study Of The Focal Specialities Of Femtosecond Radially Polarized Light Beam

The radially polarized light has stronger longitudinal electric field and sharper focal spots, and it is the unique qualities that make the radially polarized light more valuable than the linearly polarized light and circularly polarized light, as well as more attentions, besides, it will have attractive applied prospect. The ultrashort intense femtosecond laser pulse possesses large peak power and spectral width, which is the important tool to realize laser-produced fusion and laser grain accelerator. Then the femtosecond radially polarized light has the specialities of both the radially polarized light and the ultrashort intense femtosecond laser pulse, and its excellent focused features which have been found will be helpful to the research of laser grain acceleration.This paper combines the numerical simulation and experimental test and analysis, analyzes the focused specialities and rules of light under different focused conditions, and analyses the condition of light path to make the femtosecond radially polarized light get tinier focal spots. In order to make sure of the veracity and facticity of measuring the size of the focal spots, the method of combing recording and measuring is used in the experiments. Record the focal spots with high-resolution photosensitive materials, scan longitudinally and transversely by nanometer resolution ratio, combine the precision measurement method of recording faculas, and make sure to get the tiniest focal spots from the faculas, and obtain the change rule of the faculas near the focal spots.To make use of the measuring focal spots project, compare the size of focal spots of radially polarized light and linearly polarized light under the same condition, combine the result of numerical analysis, the conclusion that the focal spots of the radially polarized light are smaller than those of the linearly polarized light under the condition of high numerical apertures. At the same time, the specialities of different focal spots shapes of the two kinds of polarized light are also found. Besides, we find the differences between the results of numerical simulation and experimental measurement, and analyze the reasons of the differences and affecting the size of focal spots, getting the common conclusions of the focusing of femtosecond radially polarized light.The experimental analysis and results in this paper builds a nice base for a further study on ultrashort intense laser pulse radially polarized light, to get the best focused program and it is helpful to study the three dimensional transient characteristics of femtosecond radially polarized light, which will push the research on laser particle acceleration with radially polarized light.