Hybrid nested negative curvature fiber with ultra-low-loss in the terahertz band

A novel hybrid nested negative curvature fiber (NCF) based on the three-layer anti-resonant effect is described. The elliptical tubes cladding structure exhibits the advantage of flexible design and can effectively reduce propagation losses. The influences of the nested methods and structural parameters on the propagation characteristic are analyzed numerically. Since high-resistance silicon (HRS) has an ultra-low absorption coefficient in the THz frequency range, the effective material loss is reduced. Meanwhile, the three-layer nested structure suppresses the confinement loss, the total loss is as low as 6.62 x 10-5 dB/m at 1.1 THz. The effects of the number of cladding tubes and dielectric layers on the propagation loss are compared and analyzed. The optimized NCF shows a loss of less than 10-4 dB/m between 1 and 1.06 THz and 1.1-1.24 THz. The result reveals a new method to design broadband ultra-low-loss hollow-core NCFs.