Singlemoded THz guidance in bendable TOPAS suspended-core fiber directly drawn from a 3D printer

Abstract

Terahertz (THz) technology has witnessed a significant growth in a wide range of applications, including spectroscopy, bio-medical sensing, astronomical and space detection, THz tomography, and non-invasive imaging. Current THz microstructured fibers show a complex fabrication process and their flexibility is severely restricted by the relatively large cross-sections, which turn them into rigid rods. In this paper, we demonstrate a simple and novel method to fabricate low-cost THz microstructured fibers. A cyclic olefin copolymer (TOPAS) suspended-core fiber guiding in the THz is extruded from a structured 3D printer nozzle and directly drawn in a single step process. Spectrograms of broadband THz pulses propagated through different lengths of fiber clearly indicate guidance in the fiber core. Cladding mode stripping allow for the identification of the single mode in the spectrograms and the determination of the average propagation loss (~ 0.11 dB/mm) in the 0.5-1 THz frequency range. This work points towards single step manufacturing of microstructured fibers using a wide variety of materials and geometries using a 3D printer platform. Terahertz (THz) waves or T-waves occupy a window of electromagnetic waves with frequency ranging from ν ~ 0.1 THz to ν ~ 10 THz (corresponding to the wavelength range from λ ~ 30 µm to λ ~ 3 mm). Over the last decade, THz waves have been exploited in many applications owing to their unique characteristic such as ability to penetrate in most of dielectric materials and provide improved resolution when compared to micro-or millimeter waves. Security scanning, non-destructive testing and imaging are some of the most noteworthy application of THz technologies 1,2. Because of their non-ionizing nature, THz waves can be used to detect organic tissue without causing damage, and can be safely applied for medical and biomedical sensing 3,4. THz waves have great potential to be exploited for detecting chemicals, pharmaceuticals and biological agents, as the main rotational modes of many macromolecules have a strong absorption in the THz region 5,6. They can also be used in wireless communications to increase data transmission, due to the large bandwidth of the THz band 7 , and in astronomy, to locate cold matter in space or for imaging applications in deep space 8,9. Although THz waves have shown strong potential for imaging and sensing, most of the THz systems are based on free-space optics that are quite delicate. Hence, a significant amount of research has focused on achieving low-loss and low-dispersion THz waveguiding. Metal wires were the very first material used in THz waveguides due to their low material absorption 10,11 : square and circular metallic waveguides have been demonstrated at the beginning of this century for very dispersive and low loss THz propagation 12. In 2001, two thin metallic strips were used to construct a parallel plate THz waveguides for low loss and low group velocity dispersion 13. The combination of metallic and polymer for fabricating THz waveguide was pro...

Ultra-High Sensitivity Terahertz Microstructured Fiber Biosensor for Diabetes Mellitus and Coronary Heart Disease Marker Detection

“…For the length of terahertz MSF, 50 mm~100 mm is usually set as appropriate. If the fiber length is too low, the number of terahertz wave oscillations inside the fiber is too few to form a stable mode field distribution, and at the same time, it will enhance the difficulty of experimental operation; if the MSF length is too long, the MSF biosensor may face problems such as output signal attenuation, sensitivity to bending loss, and more likelihood of fiber defects during the manufacturing process [ 20 , 34 , 35 ].…”

“…The combination of 3D printing and extrusion technologies enables rapid and precise fabrication of MSFs, which typically involves extruding a molten cyclic olefin polymer through a 3D printing nozzle and stretching it directly to the size required for THz sensing [ 20 , 35 ]. Compared with other traditional techniques for fiber preparation, this technique simplifies the fiber prefabrication and enables precise manufacturing of MSF structures with large duty cycles [ 35 ]. In recent years, by continuously optimizing MSF end face design and 3D printing fabrication schemes, the prepared fibers have achieved low-loss operating performance over a wide frequency range [ 34 ].…”

Hollow-core antiresonant terahertz fiber-based TOPAS extruded from a 3D printer using a metal 3D printed nozzle

“…High ultraviolet transmission has been observed in a TOPAS polymer with optimized grade, providing an attractive alternative to quartz glass for analytical and diagnostic applications. The transparency of TOPAS in the THz regime has led to the fabrication of polymer spherical planoconvex lenses for THz frequency [45] and also of THz waveguides [26,34,37,46,47].…”

“…A table-top fiber drawing tower was recently demonstrated using an FDM 3D printer with built-in filament heating and supply system [47,48]. Compared with other techniques, extrusion is a single-step process that has significant potential for the fabrication of soft glass and polymer optical fiber preforms with noncircular patterns [49][50][51].…”

“…A second lens with a focal length of 50 mm was positioned at the other end of the holder for collimation. The THz source and detector used in this work are the same as reported in our previous THz setup for characterizing solid-core THz fiber [47]. The source and detector are active up to ν ∼ 2.5 THz and ν ∼ 4 THz, respectively, but the spectroscopic dynamic range is limited by ambient noise and component misalignment, which in particular limits the high end of the frequency range.…”