Transfer of Angular Monentum by Circularly Polarized Near Fields

该项目利用了这样一个事实，即由特殊的纳米天线产生的局部旋转的近场具有类似于圆偏振平面光波的特性。特别是，近场的光子具有±ћ的自旋动量，所有与光子自旋有关的效应(二色性、光学自旋取向和全光磁化开关)也存在于近场。在接下来的资助期，我们将把圆偏振近场应用于利用等离子体辅助全光开关方案来切换纳米粒子的磁化态的情况，以及用于制造具有前所未有的亮度和自旋极化的自旋偏振场发射体的情况。这种全光磁开关方案将应用于采用分子束外延技术在超高真空中原位沉积的GdCoFe铁磁性薄膜。磁化转换的控制将通过使用自旋极化光电子显微镜测量由增强近场光电发射的电子的自旋来实现。场发射器件是在提供几乎完全自旋极化的应变多层结构的基础上发展起来的。使用泵浦-探测方案的时间分辨率与空间分辨率的结合使人们对潜在的光电发射机制有了更深的理解。

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.