Authors
Zhanke Zhou, Yuxin Yang, Lin Sun, Xin Guo, Limin Tong
Published in
The Review of scientific instruments. Volume 97. Issue 9. Sep 01, 2026.
Abstract
Generation and characterization of ultra-confined optical fields are of great importance in fundamental optics and optical technologies. A dielectric nanoslit waveguide formed by a coupled nanofiber pair (CNP) can provide such a field openly accessible on its endface, exhibiting extreme confinement down to the sub-nanometer level. However, its direct imaging, which is critical for its characterization and applications, remains challenging, as such a field exists in the near field of the suspended microscale waveguide endface with ultra-small feature sizes. Here, we demonstrate the first near-field imaging of an ultra-confined optical field on the endface of a silica CNP based on a custom-built waveguiding-excited scattering-type scanning near-field optical microscopy system. Using the fiber-taper-assisted waveguiding excitation technique, we excite the nanoslit waveguiding mode with an efficiency of up to 89%. Leveraging the flexible configuration of the piezo-probe for precise engagement on the endface, we resolve the ultra-confined optical near field of the nanoslit mode at a 630-nm wavelength, with a spatial resolution of ∼20 nm under an optimized probe tapping amplitude of 35 nm. The near-field imaging approach shown here enables in situ characterization of and direct access to the ultra-confined optical field on the endface of a nanoslit waveguide, which may lead to a variety of possibilities from nanometer-scale light-matter interaction to optical nanoscopy and atom/molecule manipulation.
PMID:
42720503
Bibliographic data and abstract were imported from PubMed on 10 Sep 2026.
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