Ultraintense femtosecond magnetic nanoprobes induced by azimuthally polarized laser beams

We report a novel scheme to generate laser-induced, ultrafast, intense (Tesla scale), spatially isolated, magnetic fields. Three-dimensional particle-in-cell simulations show that a femtosecond azimuthally-polarized infrared vector beam, aimed to a conducting circular aperture, produces an intense axially polarized tip-shaped femtosecond magnetic field, extending over micrometer distances and being isolated from the electric field. Our results are backed-up by an analytic model, demonstrating the underlying physics and guiding for optimal parameters. In particular, we find the conditions under which the magnetic nanoprobe is substantially enhanced, reaching 4 T when driven by a $10^{11}$ W/cm$^2$ laser field, which reflects a selective enhancement by a factor of $\sim$6. Our scheme offers a promising tool to control, probe and tailor magnetic nanodomains in femtosecond timescales through pure magnetic interaction by using structured laser beams.