Hollow polycarbonate waveguides with inner Cu coatings for delivery of terahertz radiation

Rutgers, The State University of New Jersey, Нью-Брансуик, New Jersey, United States
Optics Express (Impact Factor: 3.49). 11/2004; 12(21):5263-8. DOI: 10.1364/OPEX.12.005263
Source: PubMed


Terahertz (THz) radiation has important applications in spectroscopy, imaging, and space science. Fiber optics for the THz region have been limited to rigid hollow metallic waveguides or short lengths of solid-core transparent dielectrics such as sapphire and plastic. We have fabricated flexible, hollow polycarbonate waveguides with interior Cu coatings for broadband THz transmission using simple liquid-phase chemistry techniques. The losses for these hollow-core guides were measured using a tunable, cw single-mode far IR laser. The losses for the best guides were found to be less than four dB/m and the single mode of the laser was preserved for the smaller bore waveguides.

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    • "Several waveguide geometries have been demonstrated at terahertz frequencies, including metal wires [14], parallel plate transmission lines [15], hollow polycarbonate waveguides [16] and corrugated metallic surfaces [17]. At terahertz frequencies, most metals behave as a perfect electrical conductor, which does not support a bound plasmonic mode at a planar interface. "
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    • "With this nanoparticle layer deposition (NLD) method, an even deposition of NP is possible without the threat of damaging the thin struts of the fiber. Possible fields of applications include surface-enhanced raman spectroscopy (SERS) [4] and surface-enhanced fluorescence , which use the field enhancement near the particle surface [5], refractive index measurement, biomolecule detection [6], or THz waveguiding [7], respectively. Metal NP are under investigation in LSPR sensors as transducers for signal transfers. "
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    • "The more commonly used TE mode contains both the tangential and the normal components near the metallic surface. This mode exhibits intermediate loss figures: in a 3 mm bore copper waveguide we measured loss of 3.9 dB/m at 1.89 THz [6]. It is important to realize that minimizing losses in hollow core THz waveguides inevitably leads to designs where the core is much larger than the wavelength. "
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    ABSTRACT: Research on reducing material absorption in Tera-hertz (THz) waveguides has lead to development of guiding struc-tures with transmission losses as low as 1 dB/m. Among waveg-uides that exhibit low loss at THz frequencies are the dielectric-lined hollow cylindrical metallic waveguides. Loss reduction in this waveguide is attributed to an ideal profile of the dominant hybrid HE mode. This mode profile also results in relatively low dis-persion and very high coupling efficiency. In this contribution we overview properties of dielectric-lined hollow cylindrical metallic waveguides for THz waves, their design principles and the fabri-cation process. The impact of the mode profile on losses and dis-persion at THz frequencies is confirmed experimentally by THz near-field imaging and THz time-domain spectroscopy and numer-ically by the finite element method.
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