Super-resolution microscopy by microspheres emerged as a simple and broadband imaging technique; however, the mechanisms of imaging are debated in the literature. Furthermore, the resolution values were estimated based on semi-quantitative criteria. The primary goals of this work are threefold: i) to quantify the spatial resolution provided by this method, ii) to compare the resolution of nanoplasmonic structures formed by different metals, and iii) to understand the imaging provided by microfibers. To this end, arrays of Au and Al nanoplasmonic dimers with very similar geometry were imaged using confocal laser scanning microscopy at λ = 405 nm through high-index (n~1.9-2.2) liquid-immersed BaTiO3 microspheres and through etched silica microfibers. We developed a treatment of super-resolved images in label-free microscopy based on using point-spread functions with subdiffraction-limited widths. It is applicable to objects with arbitrary shapes and can be viewed as an integral form of the super-resolution quantification widely accepted in fluorescent microscopy. In the case of imaging through microspheres, the resolution ~λ/6-λ/7 is demonstrated for Au and Al nanoplasmonic arrays. In the case of imaging through microfibers, the resolution ~λ/6 with magnification M~2.1 is demonstrated in the direction perpendicular to the fiber with hundreds of times larger field-of-view in comparison to microspheres.
This work takes inspiration from chemistry where the spectral characteristics
of the molecules are determined by hybridization of electronic states evolving
from the individual atomic orbitals. Based on analogy between quantum mechanics
and the classical electrodynamics, we sorted dielectric microspheres with
almost identical positions of their whispering gallery mode (WGM) resonances.
Using these microspheres as classical photonic atoms, we assembled them in a
wide range of structures including linear chains and planar photonic molecules.
We studied WGM hybridization effects in such structures using side coupling by
tapered microfibers as well as finite difference time domain modeling. We
demonstrated that the patterns of WGM spectral splitting are representative of
the symmetry, number of constituting atoms and topology of the photonic
molecules which in principle can be viewed as "spectral signatures" of various
molecules. We also show new ways of controlling WGM coupling constants in such
molecules. Excellent agreement was found between measured transmission spectra
and spectral signatures of photonic molecules predicted by simulation.Comment: This is the pre-peer reviewed version of the following article
submitted to Laser Photonics Rev. on October 17, 2016. Revisions have been
made in the published version. "Whispering gallery mode hybridization in
photonic molecules", Y. Li, F. Abolmaali, K. W. Allen, N. I. Limberopoulos,
A. Urbas, Y. Rakovich, A. V. Maslov, and V. N. Astratov, Laser Photonics Rev.
DOI: 10.1002/lpor.201600278 (2017
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.