Effective bandwidth of terahertz antiresonant reflecting pipe waveguide.

We numerically investigate the transmission of the antiresonant-reflection-based terahertz (THz) pipe waveguide in which the cladding layer is very thin or the cladding index is close to one. It is found that robustness of the waveguide confinement is maintained when the cladding thickness is small, while the guiding ability deteriorates when the cladding index approaches to one. Hence, to increase the effective bandwidth of the pipe waveguide, reducing the cladding thickness is more desirable. Moreover, we also examine the effective bandwidth under the condition that the pipe waveguide is subject to a fixed ratio of core diameter to cladding thickness. Numerical result indicates that, as the ratio increases, the effective bandwidth increases as well.