Fiber bundle

Materials science

Refractive index

Optical fiber

Computer science

Limit (mathematics)

Fiber optic sensor

Wavelength

Resolution (logic)

Photonic-crystal fiber

Sapphire

Laser

Physics

Mathematics

Optics

Mathematical analysis

Artificial intelligence

Composite material

Fiber

High-refractive-index polymer

Bundle

Graded-index fiber

Diffraction

Optoelectronics

Advanced Optical Materials

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 this work, high‐refractive‐index sapphire fibers with n &gt; 3 are employed in the terahertz (THz) range, which ensures strong confinement of the guided modes and enables a fiber bundle resolution beyond the 0.62λ Abbe limit of free space optics. 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 vares across the aperture with the mean value of 0.53λ, while, at certain regions of the bundle, it is as low as 0.3λ. The developed principles can be translated to any spectral range where high‐refractive‐index fiber optics materials are available.

Overcoming the Abbe Diffraction Limit Using a Bundle of Metal‐Coated High‐Refractive‐Index Sapphire Optical Fibers