Low-Loss Asymptotically Single-Mode THz Bragg Fiber Fabricated by Digital Light Processing Rapid Prototyping

In this paper, the design and measurement of a three-dimensional-printed low-loss asymptotically single-mode hollow-core terahertz Bragg fiber are reported, operating across the frequency range from 0.246 to 0.276 THz. The HE11 mode is employed as it is the lowest loss propagating mode, with the electromagnetic field concentrated within the air core as a result of the photonic crystal bandgap behavior. The HE11 mode also has large loss discrimination compared to its main competing HE12 mode. This results in asymptotically single-mode operation of the Bragg fiber, which is verified by extensive simulations based on the actual fabricated Bragg fiber dimensions and measured material parameters. The measured average propagation loss of the Bragg fiber is lower than 5 dB/m over the frequency range from 0.246 to 0.276 THz, which is, to the best of our knowledge, the lowest loss asymptotically single-mode all-dielectric microstructured fiber yet reported in this frequency range, with a minimum loss of 3 dB/m at 0.265 THz.