Sapphire Photonic Crystal Waveguides for Terahertz Sensing in Aggressive Environments (original) (raw)
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Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques, 2020
The paper is devoted to problem of waveguide designing for the THz frequency range of electromagnetic spectra. We proposed different types of THz waveguides on the base of the sapphire shaped crystals. Due to the advantages of the shaped crystal growth technique and unique combination of sapphire physical properties, the sapphire waveguides with relatively low losses, near-zero dispersion and inertness of the waveguide characteristics with respect to external conditions can be used effectively for guiding of the THz radiation in the harsh environments.
Optical Materials for the THz Range
Optics and Spectroscopy, 2018
The properties of optical materials usable in the terahertz (THz) spectral range, which is the boundary between the optical and radio ranges, are examined. The relevance of the research field associated with the optics of THz devices is largely governed by intensified activity on creating lasers operating in the THz range and the discovery of substantial problems in the use of optical materials for these applications in general. The present study is devoted to analyzing the properties-especially optical properties-of the THz materials used. The characteristics are given, and the physical, chemical, and optical properties of conventional and new materials, including crystalline (silicon, sapphire, quartz, diamond, germanium, and silicon carbide), as well as a number of polymers (polymethylpentene, polyethylene, and polytetrafluoroethylene), are discussed and compared.
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Journal of the Optical Society of America B, 2000
Quasi-optical techniques are used to efficiently couple freely propagating pulses of terahertz (THz) electromagnetic radiation into circular and rectangular metal waveguides. We have observed very dispersive, low-loss propagation over the frequency band from 0.65 to 3.5 THz with typical waveguide cross-section dimensions on the order of 300 m and lengths of 25 mm. Classical waveguide theory is utilized to calculate the coupling coefficients into the modes of the waveguide for the incoming focused THz beam. It is shown that the linearly polarized incoming THz pulses significantly couple only into the TE 11 , TE 12 , and TM 11 modes of the circular waveguide and the TE 10 and TM 12 modes of the rectangular guide. The propagation of the pulse through the guide is described as a linear superposition of the coupled propagating modes, each with a unique complex propagation vector. This picture explains in detail all the observed features of the THz pulse emerging from the waveguide. We demonstrate both theoretically and experimentally that it is possible to achieve TE 10 single-mode coupling and propagation in a suitably sized rectangular waveguide for an incoming focused, linearly polarized THz pulse with a bandwidth covering many octaves in frequency and that overlaps more than 35 waveguide modes. Finally, to facilitate the application of these THz waveguides to THz time-domain spectroscopy of various configurations of dielectrics in the waveguide including surface layers, we present analytic results for the absorption and the dispersion of such layers.
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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 transmiss...
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Transmission characteristics of lens-duct, Cytop planar photonic crystal waveguide (PPCW) and hollow-core microstructured optical fiber were analyzed in the terahertz (THz) region. The lens duct was able to channel and couple the THz radiation into a Teflon waveguide with a loss of about 0.7 dB. Single-mode propagation and frequency-selective properties were achieved using PPCW whose central frequency is at 0.45 THz. Results of time-domain spectra of the hollow-core microstructured polymer optical fiber showed a difference of about 20 ps between the THz waves that propagated in the core and cladding. Frequency shift of the transmission bands between waveguides of different size suggested photonic bandgap guidance. Finite-difference time domain calculations agreed relatively well to the experimental results of PPCW and hollow-core fibers.
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8th International Conference on Electrical and Computer Engineering, 2014
THz is an emerging technology with many important applications in imaging and sensing, but due to lack of suitable low-loss waveguides future progress can be limited. A rigorous full-vectorial modal solution approach based on the computationally efficient finite element method is used to find the propagation properties of THz waveguides. Design approaches are presented to reduce the modal loss of such waveguides. Designs of several THz devices, including quantum cascade lasers, power splitters and narrow-band filters are also presented.