2, Vanderbilt University, Nashville, Tennessee, United States
Surface phonon polaritons (SPhPs) have seen a recent surge in interest due to their ability to bring the optical confinement of plasmonics in to the Mid-IR/THz regime, without any of the associated losses. By creating metamaterials and multicomponent superlattices made out of polar dielectric materials (i.e. SiC) SPhPs can be manipulated to achieve active tunability, second harmonic generation enhancement, and structure-induced hyperbolic permittivities. For nanoscale complex structures such as these localized SPhP measurements are key to understanding the interplay between the different components.
Electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) has been a highly successful method of locally measuring optical properties of nanostructures. However, up until recently the Mid-IR/THz regime was inaccessible due to the energy spread of the field emission electron guns. Recent breakthroughs in STEM monochromation have reduced the background in the Mid-IR by orders of magnitude, allowing for low-efficiency signals to be tracked and measured through EELS. Here we examine nanostructured SiC metamaterials in a monochromated STEM to map the excitation of SPhPs directly at the nanoscale.
This work is supported by the Center for Nanophase Materials Sciences (CNMS), which is sponsored at ORNL by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy