Single-Mode Hollow-Core Anti-Resonant Waveguides for Low-Loss THz Wave Propagation

A single-mode hollow-core anti-resonant (HC-AR) waveguide designed for low-loss terahertz (THz) wave propagation is fabricated by three-dimensional (3D) printing. Compared to similar structures reported recently, the rotating-nested semi-elliptical tubes (SETs) in the HC-AR THz waveguide cladding suppress multiple high-order modes (LP11, LP21, and LP02 modes) at the same time giving rise to enhanced single-mode transmission and low losses. Three HC-AR THz waveguides with different wall thicknesses are produced using two photosensitive resins and analyzed by THz time-domain spectroscopy (THz-TDS). The experimental results show that the electric field distributions at the output end of these waveguides have a Gaussian-like distribution reflecting that of the single mode. The smallest transmission losses determined by the ‘cut-back’ method are 0.03 cm−1 at 0.31 THz for sample A, 0.02 cm−1 at 0.4 THz for sample B, and 0.01 cm−1 at 0.23 THz for sample C. The consistent experimental and simulated results reveal that the HC-AR THz waveguide has many advantages over current ones by achieving low losses and single-mode operation simultaneously.