A metasurface structure-assisted terahertz negative curvature fiber

Abstract Negative curvature fibers have the benefits of high bandwidth, low loss, and provide higher transmission performances. Birefringence of the fiber is particularly important, with potential application value in communication, imaging and other fields. In this paper, a metasurface structure-assisted terahertz negative curvature fiber is designed to improve the birefringence characteristic. This work breaks through the conditional design ideas, and theoretically analyzes the effect of adding gold microstructures in the cladding structures on the transmission characteristics of negative curvature fibers. The investigation results show that the birefringence of the designed fiber exhibits a significant increase in most frequency range between 1.75 - 2.4 THz compared to the results before adding gold microstructures. The maximum birefringence reaches as high as 0.00216 when the frequency is 2.175 THz and θ is 90°. Compared to the original frequency, the birefringence has increased by nearly an order of magnitude. The highest birefringence has been increased to 3.5 times. In addition, the influences of the gold microstructures on the confinement loss, waveguide dispersion, and effective mode field area are also investigated. This fiber provides a reference for the design of high birefringence terahertz fibers in the future.