Dielectric nanospheres are important components for photonic applications, where interactions between whispering gallery modes (WGMs) can be used to construct photonic band structures. Using the electromagnetic fields generated by relativistic electrons in a monochromated 200 keV scanning transmission electron microscope, we record electron energy loss spectral features reflecting the density of states (DOS) of the electric-type WGMs in SiO2 nanospheres over an energy range extending into the far-ultraviolet regime. These results demonstrate possibilities for mapping the local DOS of photonic systems in an electron microscope with a spatial resolution of a few nanometers.
|Journal||Applied Physics Letters|
|State||Published - 2008|