Flexible Terahertz Photonic Light-Cage Modules for In-Core Sensing and High Temperature Applications

Abstract

Terahertz technology is a growing and multidisciplinary research field, particularly in applications relating to sensing and telecommunications. A number of terahertz waveguides have emerged over the past few years, which are set to complement the capabilities of existing and bulky free-space setups. In most terahertz waveguide designs, however, the guiding region is physically separated from the surroundings, making any interaction between the guided light and the environment inefficient. Here, we present photonic terahertz light cages (THzLCs) operating at terahertz frequencies, consisting of freestanding dielectric strands, which guide light within a central hollow core with immediate access to the environment. We experimentally show the versatility and design flexibility of this concept by 3Dprinting several cm-length-scale modules on the basis of a single design, using four different polymer and ceramic materials, which are either rigid, flexible, or resistant to high temperatures. We characterize both propagation and bend losses for straight and curved waveguides, which, in the range 0.25−0.7 THz, are of order ∼1 dB/cm in the former and ∼2−8 dB/cm in the latter for bend radii below 10 cm and are largely independent of the chosen material. Our transmission experiments are complemented by near-field measurements at the waveguide output, which reveal the antiresonant guidance for straight THzLCs and a deformed fundamental mode in the bent waveguides, in agreement with numerical conformal mapping simulation models. We show that these THzLCs can be used as (i) flexible, reconfigurable, and bendable modular assemblies; (ii) in-core sensors of resonant structures contained directly inside the hollow core; or (iii) high-temperature waveguide sensors, with potential applications in industrial monitoring and sensing. Finally, we introduce and discuss appropriate figures of merit for quantifying the performance of light cage guidance with respect to free-space propagation. The 3D-printed light cages presented are a novel and useful addition to the growing library of terahertz waveguides, marrying the waveguidelike advantages of reconfigurable, diffractionless propagation with the free-space-like immediacy of direct exposure to the surrounding environment. KEYWORDS: terahertz photonics, hollow core waveguide, 3D printing, terahertz spectroscopy, antiresonant guidance, figure of merit ■ INTRODUCTIONRecent years have been marked by a rapid development in sources, detectors, and waveguides operating in the terahertz frequency range (∼0.1−10 THz), a range which has the unique capability of serving a number of far-reaching and diverse applications areas. 1,2 These areas include sensing and spectroscopy (e.g., of gases, 3 molecules, 4 or DNA 5,6 ), imaging and security, 7−9 pharmaceutical research, 10 broadband wireless communication (6G), 11 and industrial applications. 12 The significance and history of systems operating in this frequency range are broadly appreciated, 13 but even as the number of THz sources and detectors...

Broadband Terahertz Near-Field Excitation and Detection of Silicon Photonic Crystal Modes

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Subwavelength terahertz imaging via virtual superlensing in the radiating near field

“…Further details of the experimental setup are described in ref. 33 . The phase fluctuation, obtained from the standard deviation of the phase of the Fourier transform of 850 consecutive measurements, is between 0.05–0.35 rad between 0.2–1.5 THz, as shown in Supplementary Fig.…”

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Specularly-Reflected Wave Guidance of Terahertz Plasmonic Metamaterial Based on the Metal-Wire-Woven Hole Arrays: Functional Design and Application of Transmission Spectral Dips

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