Effect of the relief material of a zone plate on the focusing of an ultrashort cylindrical vector beam

Abstract

In this research, the process of focusing of femtosecond cylindrical vector beam with second order by binary zone plate is studied applying the frequency-dependent finite-difference time-domain method. We have demonstrated that the material of zone plates significantly influenced on the electromagnetic field formed at the focus. We also shown that, tight focusing of a second-order cylindrically polarized laser pulse produced an energy backflow in the focal plane of phase and aluminum binary zone plates. However, there is no reverse energy flux in the focus of binary zone plate made in thin gold film.