THz step-index fibers development based on crystalline

Abstract

This paper considers step-index optical fibers operating on the principle of total internal reflection. The fibers are based on the low-absorbing crystalline materials, namely shaped sapphire and lithium fluoride (LiF). The aim of this work is the numerical and experimental investigations optical properties of THz fibers.
The modal structure and propagation losses of the sapphire fibers with diameters of 200, 300, and 400 µm are simulated both at room and cryogenic (~77 K) temperatures using liquid nitrogen as the external medium. The finite-difference eigenmode (FDE) method is used to calculation of the modal electromagnetic field distribution, effective refractive index, and propagation losses. Furthermore, a similar fiber, based on the LiF is developed. The optical properties of the bulk monocrystal LiF are experimentally investigated in the wide frequency range 0.2-3.0 THz. Numerical modeling was performed for a LiF fiber with a diameter of 250 µm to evaluate its waveguiding performance across the investigated THz frequency range.
The simulation results show good localization of the fundamental mode in both Al2O3 and LiF fibers. They also confirm a significant reduction of the fiber losses at cryogenic temperature in the frequency range of 0.25-1.0 THz. Such fibers could find application in the flexible delivery of THz radiation over short distances (1–3 meters) with low losses.

Speaker

Polina Tsabolova
Prokhorov General Physics Institute of the Russian Academy of Sciences; Osipyan Institute of Solid State Physics Russian Academy of Sciences
Russia

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