Transfer of Angular Monentum by Circularly Polarized Near Fields

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The project exploits the fact that a locally rotating electrical near field generated by special nanoantennas has properties similar to a circularly polarized plane light wave. In particular, the photons of the near field possess spin momenta of ± ћ and all effects related to the photon spin (dichroism, optical spin orientation and all-optical magnetisation switching) exist for near fields as well. In the following funding period we will apply the circular polarized near-field for the case of switching the magnetization states of nanoparticles using a plasmon-assisted all-optical switching scheme and for the case of fabrication of spin-polarized field emitters with unprecedented brightness and spin-polarization. The all-optical magnetic switching scheme will be applied to ferromagnetic GdCoFe films that are deposited in-situ in UHV using molecular beam epitaxy. Control of the magnetization switching will be gained by measuring the spin of electrons that are photoemitted by the enhanced near field using spin-polarized photoemission electron microscopy. Field emitters are developed on the basis of strained GaAs multilayer structures providing almost complete spin polarization. The combination of temporal resolution using a pump-probe scheme with spatial resolution gains a deep understanding of the underlying photoemission mechanism.