Transformative Research Area "Fast Electron Nano Optics"

Saito is a representative of Group A3 in a transformative research area ” Fast electron nano-Optics (FENO)” (Area representative: Takumi Sannomiya @Tokyo Institute of Technology, HP: http://www.sannomiya.iem.titech.ac.jp/FENO/), and aims to realize new nanoscale light measurement methods using electron beams. Saito’s group will particularly work on developing an advanced method to measure “invisible light” confined in nanostructures by transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS). EELS contains all information about the excitations in matter by an electron beam. It is well known that EELS provides information on electronic states in materials like X-ray absorption spectroscopy (XAS). In recent years, it has become possible to obtain information corresponding to light absorption thanks to advancement of electron beam monochromators. The advantage of using a fast electron beam for optical excitations is not only the localized excitation volume (=high spatial resolution), but also that it allows non-dipole transitions due to the nature of point-charged particle, which is difficult with light illumination. This means that a fast electron beam can easily access nonradiative which can not be converted to light. We aim to establish a measurement technology that can decompose EELS, which contains an extremely large amount of information, in multiple dimensions such as space, momentum, and energy.