Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Excitation and Imaging of Resonant Optical Modes of Au Triangular
  Nano-Antennas Using Cathodoluminescence Spectroscopy   Cathodoluminescence (CL) imaging spectroscopy is an important technique to
understand resonant behavior of optical nanoantennas. We report high-resolution
CL spectroscopy of triangular gold nanoantennas designed with near-vacuum
effective index and very small metal-substrate interface. This design helped in
addressing issues related to background luminescence and shifting of dipole
modes beyond visible spectrum. Spatial and spectral investigations of various
plasmonic modes are reported. Out-of-plane dipole modes excited with vertically
illuminated electron beam showed high-contrast tip illumination in panchromatic
imaging. By tilting the nanostructures during fabrication, in-plane dipole
modes of antennas were excited. Finite-difference time-domain simulations for
electron and optical excitations of different modes showed excellent agreement
with experimental results. Our approach of efficiently exciting antenna modes
by using low index substrates is confirmed both with experiments and numerical
simulations. This should provide further insights into better understanding of
optical antennas for various applications.

16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci