Circular Tube lattice fibers for terahertz applications

The development of low loss, broadband, small size and flexible waveguides has become a key issue in terahertz (THz) research due to the poor characteristics of both dielectrics and metals in this frequency range. Hollow core circular tube lattice fibers (HC-CTLFs) have been recently proposed and experimentally demonstrated to match many of these conditions. They are composed of a hollow core surrounded by a circular arrangement of dielectric tubes. CTLFs guide via Inhibited Coupling (IC) which doesn't rely on photonic bandgap and the confinement depends on a strong reduction of the coupling between core modes and cladding modes. The losses in CTLF can be divided into the confinement loss and the absorption loss. Both of them can be reduced by enlarging the fiber core size, but this makes the fiber big and hardly flexible. For an optimized design of the fiber, scaling law analysis plays an important role in determining the best trade-off between low loss and small size. Here the dependence of the confinement and absorption loss on frequency and core radius are numerically investigated. Results show that confinement loss exhibits a stronger dependence of core size and frequency with respect to other hollow core fibers proposed for THz waveguiding such as Kagome, Bragg, and Tube fibers as well as to dielectric absorption loss.