Design of the low-loss wide bandwidth hollow-core terahertz inhibited coupling fibers

A multi-perspective numerical analysis of propagation loss in inhibited coupling fibers (ICFs) in terahertz (THz) band is presented. It is shown that the core boundary strut shape is a critical factor affecting the confinement loss. The simulation results demonstrate that the closer to a circular arc the struts, the lower the confinement loss. Furthermore, the strut thickness and the material refractive index determine the frequencies and the bandwidths of the low loss region. With the decrease of the strut thickness and material refractive index, the low loss region will be shifted toward the higher frequency, and the widths of low loss regions will be broadened. Besides, when material absorption is considered in simulation, the ICFs averaged propagation loss is still about three orders of magnitude lower than the material absorption loss itself. The conclusions could give valuable guidance for the design and fabrication of THz ICFs.