Pulse wave velocity measurement with soft-polymer optical fibers for wearable continuous blood pressure monitoring

Stefani, Alessio; Rukhlenko, Ivan D.; Ward, Rebecca H.; Prinable, Joseph; Large, M. I.; Fleming, Simon

doi:10.1364/cleopr.2020.c2d_3

Cited by 1 publication

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References 3 publications

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“…Finally, we note that the ability to fabricate such waveguides using standard fiber drawing techniques [40] is critical for producing long waveguide lengths. Further harnessing the extensive amount of ongoing research on antiresonant fibers at higher frequencies is likely to improve their performance and extend their operating frequency, complementing ongoing efforts in fabricating extremely flexible fibers for a wide variety of optoelectronic applications [41][42][43][44][45]. In the specific context of terahertz technology, this work demonstrates the potential of antiresonant polyurethane waveguides for making guided waves in this frequency range more practical, flexible, and accessible.…”

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confidence: 76%

Bend losses in flexible polyurethane antiresonant terahertz waveguides

Stefani,

Skelton,

Tuniz

2021

Preprint

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The quest for practical waveguides operating in the terahertz range faces two major hurdles: large losses and high rigidity. While recent years have been marked by remarkable progress in lowering the impact of material losses using hollow-core guidance, such waveguides are typically not flexible.Here we experimentally and numerically investigate antiresonant dielectric waveguides made of polyurethane, a commonly used dielectric with a low Young's modulus. The hollow-core nature of antiresonant fibers leads to low transmission losses using simple structures, whereas the low Young's modulus of polyurethane makes them extremely flexible. The structures presented enable millimeter-wave manipulation in centimeter-thick waveguides in the same spirit as conventional (visible-and near-IR-) optical fibers, i.e. conveniently and reconfigurably. We investigate two canonical antiresonant geometries formed by one-and six-tubes, experimentally comparing their transmission, bend losses and mode profiles. The waveguides under investigation have loss below 1 dB/cm in their sub-THz transmission bands, increasing by 1 dB/cm for a bend radius of about 10 cm, which is analogous to bending standard 125 µm diameter fiber to a 1.2 mm radius. I. INTRODUCTIONTerahertz frequencies (0.1-10 THz), located between the microwave and infrared, can be harnessed across a wide range of application areas, including molecular [1], gas [2] and DNA [3] sensing, imaging and security [4-6], pharmaceutical research [7], short-haul communication (6G) [8], and other industrial applications [9]. Owing to the relative infancy of accessible THz sources and detectors [10], devices in this range are relatively underdeveloped, with most systems still relying on free space propagation, in contrast to near-infrared and visible frequencies, where optical fibers and photonic circuits are decades ahead [11,12].To address this limitation, the past few years have shown rapid development of novel terahertz waveguides, e.g., polymer-based [13], sub-wavelength [14], porous [15], and hollowcore tubes/fibers [16,17] We refer the reader to some excellent recent reviews on terahertz fibers [18][19][20], which discuss common structures and the physics underlying their guidance mechanisms in great detail.

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