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arXiv · 1304.4139

Near-field focusing of dielectric microspheres: Super-resolution and field-invariant parameter scaling

Zengbo Wang·Yi Zhou·Boris Luk'yanchuk
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Abstract

Optical near-fields of small dielectric particles are of particular importance and interests for nanoscale optical engineering such as field localization, fabrication, characterization, sensing and imaging. This paper represents a systematic investigation on the focusing characteristics (focal length, field enhancement, spot size) for a given refractive-index microsphere (n=1.6) with a varying size parameter across the range of pi<q0<20*pi. Conditions for super-resolution foci were analysised in details. Particularly strong super-resolution foci with spot size falling at least 50% below the diffraction limit were identified and possible new applications were suggested. To understand how the super-resolution conditions could be scaled to other refractive-index particles or background medium, principles of field-invariant parameters scaling (size, wavelength, and refractive index) were revealed and demonstrated with example cases. It offers the new freedom to choose particles and background medium to gain super-resolution at any frequency across the whole electromagnetic spectrum.

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Zengbo Wang, Yi Zhou, Boris Luk'yanchuk. 2013-04-23. Near-field focusing of dielectric microspheres: Super-resolution and field-invariant parameter scaling. https://arxiv.org/abs/1304.4139

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