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Sapphire fiber bundles for terahertz imaging with spatial resolution beyond the Abbe limit

K.I. Zaytsev (1,2,*), G.M. Katyba (1,3), N.V. Chernomyrdin (1,2), I.N. Dolganova (2,3),
A.S. Kucheryavenko (1,3), A.N. Rossolenko (1,3), V.V. Tuchin (4,5), V.N. Kurlov (2,3), and M. Skorobogatiy (6)

1 - Prokhorov General Physics Institute of RAS, Russia
2 - Institute for Regenerative Medicine, Sechenov University, Russia
3 - Institute of Solid State Physics of RAS, Russia
4 - Saratov State University, Russia
5 - Institute of Precision Mechanics and Control of RAS, Russia
6 - Polytechnique Montreal, Canada

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While fiber bundles attract much interest in optics, their resolution is limited by the individual fiber size, which can be as large as a wavelength λ for common fiber optics materials. In order to increase fiber bundle resolution, in our work, high-refractive-index sapphire fibers (n>3), which were fabricated using the Edge-defined Film-fed Growth (EFG) technique [1], are employed in the terahertz (THz) range. They ensure strong confinement of the guided modes and enable a fiber bundle resolution beyond the 0.62λ Abbe limit of free space optics [2]. A sapphire fiber bundle is fabricated and its advanced resolution is experimentally demonstrated, using both analysis of the pair correlation function of the disordered fiber packing and continuous-wave THz imaging. The resolution varies across the aperture with the mean value of 0.53λ, while it is as low as 0.3λ at certain regions of the bundle. The developed principles can be translated to any spectral range where high-refractive index fiber optics materials are available.

This work was partially supported by the Russian Science Foundation, Projects #17-79-20346 and #19-12-00402.

[1] Progress in Crystal Growth & Characterization of Materials 64(4), 133–151 (2018), DOI: 10.1016/j.pcrysgrow.2018.10.002.
[2] Advanced Optical Materials, in press (2020), DOI: 10.1002/adom.202000307.


Kirill I. Zaytsev
Prokhorov General Physics Institute of RAS


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