INVESTIGADORES
BRAGAS Andrea Veronica
artículos
Título:
Harmonic demodulation and minimum enhancement factors in field-enhanced near-field optical microscopy
Autor/es:
ALBERTO F. SCARPETTINI; A. V. BRAGAS
Revista:
JOURNAL OF MICROSCOPY-OXFORD
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Lugar: Londres; Año: 2015 vol. 257 p. 54 - 64
ISSN:
0022-2720
Resumen:
Field-enhanced scanning optical microscopy relies on the design
and fabrication of plasmonic probes which had to provide
optical and chemical contrast at the nanoscale. In order to
do so, the scattering containing the near-field information
recorded in a field-enhanced scanning optical microscopy experiment,
has to surpass the background light, always present
due to multiple interferences between the macroscopic probe
and sample. In this work, we show that when the probe?
sample distance is modulated with very low amplitude, the
higher the harmonic demodulation is, the better the ratio
between the near-field signal and the interferometric background
results. The choice of working at a given n harmonic
is dictated by the experiment when the signal at the n+1harmonic
goes below the experimental noise. We demonstrate
that the optical contrast comes from the nth derivative of the
near-field scattering, amplified by the interferometric background.
By modelling the far and near field we calculate the
probe?sample approach curves, which fit very well the experimental
ones. After taking a great amount of experimental
data for different probes and samples, we conclude with a table
of the minimum enhancement factors needed to have optical
contrast with field-enhanced scanning optical microscopy.