Bend losses in flexible polyurethane antiresonant terahertz waveguides

TL;DR

This paper demonstrates flexible, low-loss terahertz waveguides made of polyurethane with antiresonant structures, enabling practical and reconfigurable millimeter-wave guidance with minimal bend losses.

Contribution

It introduces polyurethane-based antiresonant terahertz waveguides that combine low loss and high flexibility, a novel approach compared to traditional rigid waveguides.

Findings

Loss below 1 dB/cm in sub-THz bands.

Bend loss increases by 1 dB/cm at 10 cm radius.

Flexible waveguides comparable to optical fibers.

Abstract

The quest for practical waveguides operating in the terahertz range faces two major hurdles: large losses and high rigidity. While recent years have been marked by remarkable progress in lowering the impact of material losses using hollow-core guidance, such waveguides are typically not flexible. Here we experimentally and numerically investigate antiresonant dielectric waveguides made of polyurethane, a commonly used dielectric with a low Young's modulus. The hollow-core nature of antiresonant fibers leads to low transmission losses using simple structures, whereas the low Young's modulus of polyurethane makes them extremely flexible. The structures presented enable millimeter-wave manipulation in centimeter-thick waveguides in the same spirit as conventional (visible- and near-IR-) optical fibers, i.e. conveniently and reconfigurably. We investigate two canonical antiresonant geometries formed by one- and six-tubes, experimentally comparing their transmission, bend losses and mode profiles. The waveguides under investigation have loss below 1 dB/cm in their sub-THz transmission bands, increasing by 1 dB/cm for a bend radius of about 10 cm, which is analogous to bending standard $125 \mu{\rm m}$ diameter fiber to a 1.2 mm radius.