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

Abstract

Abstract-In this paper, the design and measurement of a 3D-printed low-loss asymptotically single-mode hollow-core terahertz Bragg fiber is 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.Index Terms-Bragg fiber, electromagnetic propagation, millimeter wave technology, photonic crystals, three-dimensional printing.

Investigation of electromagnetic mode transition and filtering of an asymptotically single-mode hollow THz Bragg fibre

“…Based on the cut-back method by comparing the amplitude of Ey at the start ( mm) and the end ( mm) of the zone III, the propagation loss of the fibre is estimated to be 4.78 dB/m, which is comparable to the experimental result of 3 dB/m in our previous experimental work [2].…”

“…However, it is challenging to fabricate extreme thin dielectric layer and long fibre using this technique, mainly limited by the printing resolution and the overall building space of the 3D printer. The complex refractive index of HTM140 used in this paper is based on the measurement results shown in [2].…”

“…In this paper, we investigate the mode transition and filtering phenomenon by using a 3D full-wave simulation of the EM wave propagation inside and along the length of a hollow all-polymer THz Bragg fibre, using directly measured material dielectric properties and with real geometric parameters [2]. The THz Bragg fibre discussed here can achieve asymptotical single-mode pattern propagation with large loss discrimination between the fundamental and other higher-order modes.…”

3D Printed Hollow-Core Terahertz Fibers

“…This fiber can propagate with low-loss propagation of 0.15 cm −1 (0.65 dB/cm) over frequencies higher than 0.35 THz. The cross-section of the single-mode and low-loss terahertz Bragg fiber presented in [71] can be seen in Figure 1h. The authors reached single mode propagation and Figure 1.…”

“…The authors reached single mode propagation and Figure 1. (a) Porous polymer terahertz fiber design [38] (b) First all-dielectric 3D printed terahertz waveguide [64]; (c) 3D printed terahertz waveguide based on Kagome photonic crystal structure [65]; (d) Hollow-core with negative curvature [67]; (e) 3D-printed polymer antiresonant waveguide [68]; (f) 3D printed terahertz Bragg [69]; (g) Bragg waveguide with defect layers [70]; (h) Single-mode Bragg waveguide [71].…”