3 research outputs found
One-Shot Measurement of the Three-Dimensional Electromagnetic Field Scattered by a Subwavelength Aperture Tip Coupled to the Environment
Near-field
scanning optical microscopy (NSOM) achieves subwavelength
resolution by bringing a nanosized probe close to the surface of the
sample. This extends the spectrum of spatial frequencies that can
be detected with respect to a diffraction limited microscope. The
interaction of the probe with the sample is expected to affect its
radiation to the far field in a way that is often hard to predict.
Here we address this question by proposing a general method based
on full-field off-axis digital holography microscopy which enables
to study in detail the far-field radiation from a NSOM probe as a
function of its environment. A first application is demonstrated by
performing a three-dimensional (3D) tomographic reconstruction of
light scattered from the subwavelength aperture tip of a NSOM, in
free space or coupled to transparent and plasmonic media. A single
holographic image recorded in one shot in the far field contains information
on both the amplitude and the phase of the scattered light. This is
sufficient to reverse numerically the propagation of the electromagnetic
field all the way to the aperture tip. Finite Difference Time Domain
(FDTD) simulations are performed to compare the experimental results
with a superposition of magnetic and electric dipole radiation
Mapping the Radiative and the Apparent Nonradiative Local Density of States in the Near Field of a Metallic Nanoantenna
We
present a novel method to extract the various contributions
to the photonic local density of states from near-field fluorescence
maps. The approach is based on the simultaneous mapping of the fluorescence
intensity and decay rate and on the rigorous application of the reciprocity
theorem. It allows us to separate the contributions of the radiative
and the apparent nonradiative local density of states to the change
in the decay rate. The apparent nonradiative contribution accounts
for losses due to radiation out of the detection solid angle and to
absorption in the environment. Data analysis relies on a new analytical
calculation, and does not require the use of numerical simulations.
One of the most relevant applications of the method is the characterization
of nanostructures aimed at maximizing the number of photons emitted
in the detection solid angle, which is a crucial issue in modern nanophotonics
Mapping the Radiative and the Apparent Nonradiative Local Density of States in the Near Field of a Metallic Nanoantenna
We
present a novel method to extract the various contributions
to the photonic local density of states from near-field fluorescence
maps. The approach is based on the simultaneous mapping of the fluorescence
intensity and decay rate and on the rigorous application of the reciprocity
theorem. It allows us to separate the contributions of the radiative
and the apparent nonradiative local density of states to the change
in the decay rate. The apparent nonradiative contribution accounts
for losses due to radiation out of the detection solid angle and to
absorption in the environment. Data analysis relies on a new analytical
calculation, and does not require the use of numerical simulations.
One of the most relevant applications of the method is the characterization
of nanostructures aimed at maximizing the number of photons emitted
in the detection solid angle, which is a crucial issue in modern nanophotonics