The optical properties of polymers and glasses useful for terahertz applications are experimentally characterized using terahertz time-domain spectroscopy (THz-TDS). A standard system setup utilizing transmission spectroscopy is used to measure different optical properties of materials including refractive index, relative permittivity, loss tangent, absorption coefficient, and transmittance. The thermal and chemical dependencies of materials are also studied to identify the appropriate materials for given terahertz applications. The selected materials can then be utilized for applications such as in waveguides, filters, lenses, polarization preserving devices, metamaterials and metasurfaces, absorbers, and sensors in the terahertz frequency range.

As technology continues to advance, the development of novel sensing systems opens new possibilities for low-cost, practical biosensing applications. In this Letter, we demonstrate a localized surface plasmon resonance system that combines both wave-guiding and plasmonic resonance sensing with a single microstructured polymeric structure. Characterizing the sensor using the finite element method simulation shows, to the best of our knowledge, a record wavelength sensitivity (WS) of 111000 nm/refractive index unit (RIU), high amplitude sensitivity (AS) of $2050{\mathrm{RIU}}^{-1}$, high sensor resolution and limit of detection of $9\times {10}^{-7}$ RIU and $8.12\times {10}^{-12}{\mathrm{RIU}}^2/\mathrm{nm}$, respectively. Furthermore, these sensors have the capability to detect an analyte within the refractive index range of 1.33–1.43 in the visible to mid-IR, therefore being potentially suitable for applications in biomolecular and chemical analyte detection.

We propose and numerically analyze various hollow-core antiresonant fiber (HC-ARF) for operation at terahertz frequencies. We compare typical HC-ARF designs with nested and adjacent nested designs while analyzing performance in terms of loss and single-mode guidance of terahertz waves. With optimized fiber dimensions, the fundamental core mode, cladding mode, core higher-order modes (HOMs), and the angle dependence of adjacent tubes are analyzed to find the best design for low loss terahertz transmission. Analysis of the fiber designs shows that the nested tube-based antiresonant fiber exhibits lower transmission loss and superior HOM suppression, exceeding 140. The nested HC-ARF is feasible for fabrication using existing fabrication technologies and opening up the possibility of efficient transmission of terahertz waves.

A hollow core antiresonant photonic crystal fiber (HC-ARPCF) is analyzed for terahertz applications. A numerical analysis of the proposed fiber is first carried out to minimize coupling between the core and cladding modes. The modeling of the scaled-up and inhibited coupling fiber is carried out by means of a Finite Element Method (FEM), which is then demonstrated using a Zeonex filament fiber, fabricated by fused deposition modeling (FDM) of 3D printing technology. The simulation is carried out to analyze both the transmission and possibility of refractometric sensing, whereas, the experimental analysis is carried out using terahertz time domain spectroscopy (THz-TDS), and supports our numerical findings, illustrating how the proposed fibers can be used for low loss transmission of terahertz waves. The simplicity of the proposed fiber structures facilitates fabrication for a number of different transmission and sensing applications in the terahertz range.

A hollow core antiresonant photonic crystal fiber (HC-ARPCF) with metal inclusions is numerically analyzed for transmission of terahertz (THz) waves. The propagation of fundamental and higher order modes are investigated and the results are compared with conventional dielectric antiresonant (AR) fiber designs. Simulation results show that broadband terahertz radiation can be guided with six times lower loss in such hollow core fibers with metallic inclusions, compared to tube lattice fiber, covering a single mode bandwidth (BW) of 700 GHz.

Amid the search for efficient terahertz transmission and gas sensing, all‐polymer terahertz waveguides attract significant interest due to their compactness and capability for providing environmentally robust systems. The high loss within metals and dielectrics in the terahertz range makes it challenging to build a low loss, mechanically stable, and broadband terahertz waveguides. In this context, hollow waveguides made of Zeonex are promising for attaining low transmission loss in the terahertz range. Herein, a microstructured hollow hexagonal‐core fiber (HCF) is investigated, which exhibits low loss, near‐zero dispersion, wide operating bandwidth, and is suitable as a gas sensor. Notably, HCF fabrication is carried out by exploiting an efficient single‐step extrusion method—by a standard filament extruder and a puller; hence the production cost is low compared with conventional extrusion methods. This introduces a novel way of fabricating complex and low‐loss terahertz fibers. The experiments demonstrate that an HCF can achieve remarkably low attenuation and near‐zero flattened dispersion as compared with any other terahertz fibers. The resulting HCFs are easy to handle and have high thermal and chemical stability. These results bring significant advancements for terahertz fiber fabrication, low‐loss ultrafast short‐distance terahertz transmission, and sensing in the terahertz spectral domain.