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NEUMAN, T. ALONSO-GONZÁLEZ, P. GARCÍA-ETXARRI, A. SCHNELL, M. HILLENBRAND, R. AIZPURUA, J.
Original Title
Mapping the near fields of plasmonic nanoantennas by scattering-type scanning near-field optical microscopy
Type
journal article in Web of Science
Language
English
Original Abstract
Near-field optical microscopy techniques provide information on the amplitude and phase of local fields in samples of interest in nanooptics. However, the information on the near field is typically obtained by converting it into propagating far fields where the signal is detected. This is the case, for instance, in polarization-resolved scattering-type scanning near-field optical microscopy (s-SNOM), where a sharp dielectric tip scatters the local near field off the antenna to the far field. Up to now, basic models have interpreted S- and P-polarized maps obtained in s-SNOM as directly proportional to the in-plane (inline image or inline image) and out-of-plane (inline image) near-field components of the antenna, respectively, at the position of the probing tip. Here, a novel model that includes the multiple-scattering process of the probing tip and the nanoantenna is developed, with use of the reciprocity theorem of electromagnetism. This novel theoretical framework provides new insights into the interpretation of s-SNOM near-field maps: the model reveals that the fields detected by polarization-resolved interferometric s-SNOM do not correlate with a single component of the local near field, but rather with a complex combination of the different local near-field components at each point (inline image, inline image and inline image). Furthermore, depending on the detection scheme (S- or P-polarization), a different scaling of the scattered fields as a function of the local near-field enhancement is obtained. The theoretical findings are corroborated by s-SNOM experiments which map the near field of linear and gap plasmonic antennas. This new interpretation of nanoantenna s-SNOM maps as a complex-valued combination of vectorial local near fields is crucial to correctly understand scattering-type near-field microscopy measurements as well as to interpret the signals obtained in field-enhanced spectroscopy.
Keywords
plasmonics; optical nanoantennas; scattering theory; scattering-type near-field optical microscopy; s-SNOM
Authors
NEUMAN, T.; ALONSO-GONZÁLEZ, P.; GARCÍA-ETXARRI, A.; SCHNELL, M.; HILLENBRAND, R.; AIZPURUA, J.
RIV year
2015
Released
15. 11. 2015
ISBN
1863-8899
Periodical
Laser and Photonics Reviews
Year of study
9
Number
6
State
Federal Republic of Germany
Pages from
237
Pages to
249
Pages count
13
BibTex
@article{BUT123967, author="Tomáš {Neuman} and Pablo {Alonso-González} and Aitzol {García-Etxarri} and Martin {Schnell} and Rainer {Hillenbrand} and Javier {Aizpurua}", title="Mapping the near fields of plasmonic nanoantennas by scattering-type scanning near-field optical microscopy", journal="Laser and Photonics Reviews", year="2015", volume="9", number="6", pages="237--249", doi="10.1002/lpor.201500031", issn="1863-8899" }