Generation of electromagnetic doughnuts

Abstract

We propose from the first time a practical way of generating flying electromagnetic doughnuts, ultra-short electromagnetic pulses that are exact solutions to Maxwell's equations, distinguished by a doughnut-like configuration of electric and magnetic fields, strong longitudinal field components along the propagation direction, and unique spatiotemporal coupling [1, 2]. Flying doughnuts (FDs) are single-cycle, wide bandwidth pulses that propagate in free-space at the speed of light. In contrast to conventional families of pulses, the spatial and temporal dependence of the FD pulse cannot be separated. FD pulses interact with matter in unique ways, including non-trivial field transformations upon reflection from interfaces and the excitation of strong toroidal response in dielectric particles [3].