Nanoscale optical tomography with cathodoluminescence spectroscopy

Abstract

Tomography has enabled the characterization of the Earth's interior, visualization of the inner workings of the human brain, and three-dimensional reconstruction of matter at the atomic scale. However, tomographic techniques that rely on optical excitation or detection are generally limited in their resolution by diffraction. Here, we introduce a tomographic technique--cathodoluminescence spectroscopic tomography--to probe optical properties in three dimensions with nanometre-scale spatial and spectral resolution. We first obtain two-dimensional cathodoluminescence maps of a three-dimensional nanostructure at various orientations. We then use the method of filtered back-projection to reconstruct the cathodoluminescence intensity at each wavelength. The resulting tomograms allow us to locate regions of efficient cathodoluminescence in three dimensions across visible and near-infrared wavelengths, with contributions from material luminescence and radiative decay of electromagnetic eigenmodes. The experimental signal can be further correlated with the radiative local density of optical states in particular regions of the reconstruction. We demonstrate how cathodoluminescence tomography can be used to achieve nanoscale three-dimensional visualization of light-matter interactions by reconstructing a three-dimensional metal-dielectric nanoresonator.

Engineering Symmetry‐Breaking Nanocrescent Arrays for Nanolasing

“…Symmetry plays a key role in determining the optical response of metal nanostructures such as resonance characteristics and electric‐field enhancement that are critical for applications including lasing, sensing, and plasmon‐enhanced luminescence . Fully symmetric structures support spectrally observable (bright) dipolar localized surface plasmons (LSPs) but subradiant (dark) in‐plane quadrupolar modes.…”

Unveiling quasi-dark surface plasmon modes in Au nanoring cavities by cathodoluminescence

“…As an alternative, electron beams allow excitation of plasmons with fine spatial precision and retrieval of information on their local properties, with much higher spatial resolution down to few nanometer level 11, 12 . In this context, cathodoluminescence (CL) spectroscopy in which the emitted photons are detected 13–17 and electron energy loss spectroscopy (EELS) through the detection of energy loss suffered by the inelastically scattered transmitted electrons 18–21 are used to probe plasmons modes in metallic nanoparticles.…”

Electron-beam spectroscopy for nanophotonics

“…d 3D tomographic reconstruction using CL (30 keV) of the plasmonic field distributions for different light wavelengths in a 230-nm-diameter polystyrene/Au-nanoshell geometry. After Ref 67. .…”