Transfer of Angular Monentum by Circularly Polarized Near Fields

该项目利用了这样一个事实，即由特殊纳米天线产生的局部旋转电近场具有类似于圆偏振平面光波的特性。特别地，近场的光子具有± 10的自旋动量，并且与光子自旋相关的所有效应（二向色性、光学自旋取向和全光学磁化切换）也存在于近场。在接下来的资助期内，我们将应用圆偏振近场，用于使用等离子体辅助全光开关方案切换纳米颗粒的磁化状态的情况，以及制造具有前所未有的亮度和自旋偏振的自旋偏振场发射器的情况。全光磁开关方案将适用于铁磁GdCoFe薄膜，原位沉积在超高真空中使用分子束外延。磁化切换的控制将获得通过使用自旋极化光发射电子显微镜测量由增强的近场光发射的电子的自旋。场致发射体是在提供几乎完全自旋极化的应变GaAs多层结构的基础上开发的。使用泵浦-探测方案的时间分辨率与空间分辨率的组合获得了对潜在光电发射机制的深入理解。

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.