Overcoming the Abbe Diffraction Limit Using a Bundle of Metal‐Coated High‐Refractive‐Index Sapphire Optical Fibers
Kirill I. Zaytsev, Gleb M. Katyba, Nikita V. Chernomyrdin, Irina N. Dolganova, Anna S. Kucheryavenko, A. N. Rossolenko, Valery V. Tuchin, В. Н. Курлов, Maksim Skorobogatiy
Abstract
Abstract 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 > 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.