All-Dielectric Nanophotonics Enables Tunable Excitation of the Exchange Spin Waves.

Launching and controlling magnons with laser pulses opens up new routes for applications including optomagnetic switching and all-optical spin wave emission and enables new approaches for information processing with ultralow energy dissipation. However, subwavelength light localization within the magnetic structures leading to efficient magnon excitation that does not inherently absorb light has still been missing. Here, we propose to marriage the laser-induced ultrafast magnetism and nanophotonics to efficiently excite and control spin dynamics in magnetic dielectric structures. We demonstrate that nanopatterning by a 1D grating of trenches allows localization of light in spots with sizes of tens of nanometers and thus launch the exchange standing spin waves of different orders. The relative amplitude of the exchange and magnetostatic spin waves can be adjusted on demand by modifying laser pulse polarization, incidence angle, and wavelength. Nanostructuring of the magnetic media provides a unique possibility for the selective spin manipulation, a key issue for further progress of magnonics, spintronics, and quantum technologies.