Abstract
Lying between optical and microwave ranges, the terahertz band in the electromagnetic spectrum is attracting increased attention. Optical fibers are essential for developing the full potential of complex terahertz systems. In this manuscript, we review the optimal materials, the guiding mechanisms, the fabrication methodologies, the characterization methods and the applications of such terahertz waveguides. We examine various optical fiber types including tube fibers, solid core fiber, hollow-core photonic bandgap, anti-resonant fibers, porous-core fibers, metamaterial-based fibers, and their guiding mechanisms. The optimal materials for terahertz applications are discussed. The past and present trends of fabrication methods, including drilling, stacking, extrusion and 3D printing, are elaborated. Fiber characterization methods including different optics for terahertz time-domain spectroscopy (THz-TDS) setups are reviewed and application areas including short-distance data transmission, imaging, sensing, and spectroscopy are discussed.
Highlights
Terahertz regime in the electromagnetic spectrum lies midway between microwaves and visible light [1,2], loosely covering the frequency range 0.1–10 THz or wavelengths between 3 mm to 30 μm
The authors demonstrated that an absorptive material, placed outside the dielectric tube, reduces the slope of dispersion curves especially in the vicinity of resonant loss maxima, what causes a strong reduction in the group velocity dispersion (GVD), reduction of bending losses and propagation bandwidth much larger that the classical anti-resonant reflecting optical waveguide (ARROW) waveguide [100]
The work on terahertz optical fiber discussed throughout the manuscript combines, the analysis of suitable materials that can be used to make a low loss terahertz optical fiber; a comprehensive review of various geometry including the microstructured photonic crystal fiber, the hollow-core fiber, the antiresonant fiber and the metamaterial-based fibers; the guiding mechanism of each type of fibers; an analysis of different methodology of fiber fabrication and characterization; and an outline of suitable application areas with further directions of future work
Summary
Terahertz regime in the electromagnetic spectrum lies midway between microwaves and visible light [1,2], loosely covering the frequency range 0.1–10 THz or wavelengths between 3 mm to 30 μm. The advance of terahertz technology and the growing interest in applications have increased the demand for developing new sources, detectors, waveguides, and other components for efficient control of terahertz waves. Terahertz has potential for biomedical spectroscopy with a photon energy that is lower than that of mid-IR radiation, yet with stronger polar molecular interactions than microwave radiation [14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34]. We aim to combine the recent development of terahertz optical fibers with different geometries and guiding mechanisms, the background materials, the fabrication and measurement techniques, and potential applications.
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