Investigation of single-mode anti-resonant hollow-core THz fibers

Single-mode fiber plays an important role in the applications of THz technology. Serving as one of the optimal choices of THz fiber, hollow-core anti-resonant fiber (ARF) with single-layer anti-resonant elements has advantages of low transmission loss, high damage threshold, low dispersion but disadvantage of single mode which can by realized by the high-order-mode (HOM) suppression effect. In this paper, the key factor affecting the HOM suppression effect in THz ARF is investigated and confirmed to be the cross-sectional area ratio of cladding tubes inner side with fiber core, besides, the ratio will slightly change with the variation of the anti-resonant period of THz ARF where the cladding tubes have different shell thickness. By optimizing the anti-resonant elements of THz ARF from round tubes to semielliptical tubes, a high-performance single-mode THz fiber is proposed and the confinement loss of high-order-mode is confirmed larger than 24 dB/m at the same time that of fundamental-mode is controlled less than 0.4 dB/m.