3 research outputs found
Angle-Resolved Cathodoluminescence Imaging Polarimetry
Cathodoluminescence
spectroscopy (CL) allows characterizing light
emission in bulk and nanostructured materials and is a key tool in
fields ranging from materials science to nanophotonics. Previously,
CL measurements focused on the spectral content and angular distribution
of emission, while the polarization was not fully determined. Here
we demonstrate a technique to access the full polarization state of
the cathodoluminescence emission, that is the Stokes parameters as
a function of the emission angle. Using this technique, we measure
the emission of metallic bullseye nanostructures and show that the
handedness of the structure as well as nanoscale changes in excitation
position induce large changes in polarization ellipticity and helicity.
Furthermore, by exploiting the ability of polarimetry to distinguish
polarized from unpolarized light, we quantify the contributions of
different types of coherent and incoherent radiation to the emission
of a gold surface, silicon and gallium arsenide bulk semiconductors.
This technique paves the way for in-depth analysis of the emission
mechanisms of nanostructured devices as well as macroscopic media
Nanoscale Spatial Coherent Control over the Modal Excitation of a Coupled Plasmonic Resonator System
We demonstrate coherent control over
the optical response of a coupled plasmonic resonator by high-energy
electron beam excitation. We spatially control the position of an
electron beam on a gold dolmen and record the cathodoluminescence
and electron energy loss spectra. By selective coherent excitation
of the dolmen elements in the near field, we are able to manipulate
modal amplitudes of bonding and antibonding eigenmodes. We employ
a combination of CL and EELS to gain detailed insight in the power
dissipation of these modes at the nanoscale as CL selectively probes
the radiative response and EELS probes the combined effect of Ohmic
dissipation and radiation
Gallium Plasmonics: Deep Subwavelength Spectroscopic Imaging of Single and Interacting Gallium Nanoparticles
Gallium has recently been demonstrated as a phase-change plasmonic material offering UV tunability, facile synthesis, and a remarkable stability due to its thin, self-terminating native oxide. However, the dense irregular nanoparticle (NP) ensembles fabricated by molecular-beam epitaxy make optical measurements of individual particles challenging. Here we employ hyperspectral cathodoluminescence (CL) microscopy to characterize the response of single Ga NPs of various sizes within an irregular ensemble by spatially and spectrally resolving both in-plane and out-of-plane plasmonic modes. These modes, which include hybridized dipolar and higher-order terms due to phase retardation and substrate interactions, are correlated with finite difference time domain (FDTD) electrodynamics calculations that consider the Ga NP contact angle, substrate, and native Ga/Si surface oxidation. This study experimentally confirms previous theoretical predictions of plasmonic size-tunability in single Ga NPs and demonstrates that the plasmonic modes of interacting Ga nanoparticles can hybridize to produce strong hot spots in the ultraviolet. The controlled, robust UV plasmonic resonances of gallium nanoparticles are applicable to energy- and phase-specific applications such as optical memory, environmental remediation, and simultaneous fluorescence and surface-enhanced Raman spectroscopies