Time behavior of focused vector beams.

Abstract

We elucidate the pecularities of time behavior of focused vector optical fields. In particular, for linear or radial incident polarizations, we demonstrate explicitly the π/2 phase delay between transverse and longitudinal components of the field generated at the focus, i.e., their appearance and reaching the peak at different instances of the optical period. For clockwise circular polarization with -1 order vortex the longitudinal component is in phase with the transverse one. For clockwise circular polarization, the same circular polarization with a +1 order vortex and for radial polarization with +1 order vortex the longitudinal field component has a constant, azimuthally rotating in time shape and it coexists with one or simultaneously with both x and y field components. In addition, we show that the recently studied ultrafast rotating dipole produced by focusing an azimuthally polarized vortex beam [Opt. Lett.41, 1605 (2016)OPLEDP0146-959210.1364/OL.41.001605] differs significantly from a pattern obtained by focusing circularly polarized light. The numerically calculated field component distributions are verified by simplifying the system with an application of a narrow ring aperture allowing precise analytical expressions to be obtained confirming the phase relations between different field components. These findings will have to be taken into account or can be taken advantage of when using vector beams in studying light-matter interactions (particle manipulation and acceleration) and especially ultrafast optical phenomena.