An Ultra-Wide Single-Mode Frequency Bandwidth and Low-Flattened Dispersion Hollow-Core Negative-Curvature THz Waveguide

An ultra-wide single-mode (SM) frequency bandwidth and low-flattened dispersion hollow-core negative-curvature (HC-NC) terahertz (THz) waveguide is proposed. SM guidance is achieved by introducing 5-tube nested semi-elliptical tubes (SETs) in the cladding to couple high order modes (HOMs) and cladding modes (CMs). By rotating the nested SETs at the appropriate angle, the HC-NC THz waveguide can achieve excellent SM guidance with HOM extinction ratio (HOMER) >100 within an ultra-wide bandwidth of 460 GHz from the frequency of 0.70 THz to 1.16 THz. The low transmission loss of fundamental mode (FM) (<0.12 dB/m) and low-flattened dispersion (−0.085 ± 0.08 ps/THz/cm) can be obtained simultaneously. To the best of our knowledge, our proposed THz waveguide creates a record of ultra-wide SM frequency bandwidth among the current hollow-core anti-resonant (HC-AR) THz waveguides. Besides, an ultra-high HOMER of 380 and FM loss of only 0.05 dB/m can be achieved at 0.90 THz. In addition, the waveguide also exhibits a good fabrication tolerance. These excellent performances make the proposed HC-NC THz waveguide a great application potential for THz transmission.