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 at 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 10¹¹ W/cm² laser field, which reflects a selective enhancement by a factor of ∼6. Our scheme offers a promising tool to control, probe, and tailor magnetic nanodomains in femtosecond time scales through pure magnetic interaction by using structured laser beams.