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A. V. Maslov and V. N. Astratov
strated. One more technique includes integration with interferometric methods which
allowed achieving axial resolution on the order of few nanometers still keeping the
lateral resolution around 112 nm for visible light illumination [56].
In this section, we concentrate on one more approach which can be viewed as
the most natural way of enhancing the resolution capability of MN based on integration with structured illumination microscopy (SIM). At this point, we will move
away from imaging the nanoplasmonic structures themselves and switch to imaging nanoscale objects, for example, dielectric nanospheres or biomedical structures
placed at the top of such arrays. We are primarily interested in situations where
different periodic (or not periodic) nanoplasmonic structures are used in near-field
proximity to the objects of interests to increase the amount of information which
can be used for reconstructing images with high spatial frequencies exceeding the
classical diffraction limit. To this end, we will use examples of using dye-doped fluorescent objects as opposed to label-free imaging. We need to clarify that the physical
mechanisms of super-resolution considered in this Section are not based on special nonlinear properties of such FL objects. They were selected only to increase the
brightness and contrast of nanoscale objects selected for the resolution quantification.
We begin in Sect. 16.5.1 with introducing a basic principle of SIM in which the
illumination with an interference pattern is used. After that, we consider a series of
techniques where a similar principle is realized using plasmon-assisted SIM (PSIM),
localized PSIM (LPSIM), and eventually, LPSIM integrated with MN. These methods can be viewed as far-field techniques based on out-of-plane diffraction caused
by periodic surface modulation. These methods require obtaining multiple images
and post-imaging processing. After that, in Sect. 16.5.2 we consider a method based
on plasmon coupled leakage radiation (PCLR) which allowed a modest twofold
increase of resolution compared to standard microscopy without post-imaging processing. Finally, in Sect. 16.5.3 we suggest a novel way of near-field illumination
of objects using plasmonic “hot spots” in short-period nanoplasmonic arrays which
cannot be resolved in the far field, but can contribute to super-resolution imaging of
objects placed in contact with such arrays. For arrays with sufficiently short periods
(<150 nm) the coupling to surface lattice resonances becomes inefficient, and more
likely mechanism of imaging is the coupling to the closest LSPRs or “hot spots” containing near fields with very large in-plane k-vectors. We believe that in the latter case
the super-resolution stems from the coupling of the emission of nanoscale objects to
the closest LSPRs in the underlying plasmonic metasurface. In its turn, such highly
localized, plasmonic-mediated emitters are evanescently coupled into high-index
microspheres and form magnified virtual images of such nanoscale objects with the
participation of their optical near fields.
16.5.1 Principles of SIM, PSIM, and LPSIM
In classical SIM the objects are illuminated with a periodically modulated interference pattern and their high spatial frequency information gets “smeared across
A. V. Maslov and V. N. Astratov
strated. One more technique includes integration with interferometric methods which
allowed achieving axial resolution on the order of few nanometers still keeping the
lateral resolution around 112 nm for visible light illumination [56].
In this section, we concentrate on one more approach which can be viewed as
the most natural way of enhancing the resolution capability of MN based on integration with structured illumination microscopy (SIM). At this point, we will move
away from imaging the nanoplasmonic structures themselves and switch to imaging nanoscale objects, for example, dielectric nanospheres or biomedical structures
placed at the top of such arrays. We are primarily interested in situations where
different periodic (or not periodic) nanoplasmonic structures are used in near-field
proximity to the objects of interests to increase the amount of information which
can be used for reconstructing images with high spatial frequencies exceeding the
classical diffraction limit. To this end, we will use examples of using dye-doped fluorescent objects as opposed to label-free imaging. We need to clarify that the physical
mechanisms of super-resolution considered in this Section are not based on special nonlinear properties of such FL objects. They were selected only to increase the
brightness and contrast of nanoscale objects selected for the resolution quantification.
We begin in Sect. 16.5.1 with introducing a basic principle of SIM in which the
illumination with an interference pattern is used. After that, we consider a series of
techniques where a similar principle is realized using plasmon-assisted SIM (PSIM),
localized PSIM (LPSIM), and eventually, LPSIM integrated with MN. These methods can be viewed as far-field techniques based on out-of-plane diffraction caused
by periodic surface modulation. These methods require obtaining multiple images
and post-imaging processing. After that, in Sect. 16.5.2 we consider a method based
on plasmon coupled leakage radiation (PCLR) which allowed a modest twofold
increase of resolution compared to standard microscopy without post-imaging processing. Finally, in Sect. 16.5.3 we suggest a novel way of near-field illumination
of objects using plasmonic “hot spots” in short-period nanoplasmonic arrays which
cannot be resolved in the far field, but can contribute to super-resolution imaging of
objects placed in contact with such arrays. For arrays with sufficiently short periods
(<150 nm) the coupling to surface lattice resonances becomes inefficient, and more
likely mechanism of imaging is the coupling to the closest LSPRs or “hot spots” containing near fields with very large in-plane k-vectors. We believe that in the latter case
the super-resolution stems from the coupling of the emission of nanoscale objects to
the closest LSPRs in the underlying plasmonic metasurface. In its turn, such highly
localized, plasmonic-mediated emitters are evanescently coupled into high-index
microspheres and form magnified virtual images of such nanoscale objects with the
participation of their optical near fields.
16.5.1 Principles of SIM, PSIM, and LPSIM
In classical SIM the objects are illuminated with a periodically modulated interference pattern and their high spatial frequency information gets “smeared across