The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Dielectric reflectarray antennas are proposed as a possible low-loss solution for high gain THz antennas. A 3-D printing technology is utilized to fabricate the antenna, and numerical and experimental results are presented for a prototype operating at 100 GHz. This study shows that the proposed design approach is well suited for high gain THz antennas.
The dielectric properties of nematic liquid crystal (LC) mixtures are measured from 300 GHz to 1500 GHz. Measurements are performed in a standard THz TDS setup. Refractive index and extinction coefficient for parallel and perpendicular orientation are calculated and compared to results obtained at 19 GHz. The investigated mixtures are of interest for Terahertz devices as their properties stay almost...
Complex dielectric susceptibilities of MWCNT/PE composites with various contents of nanotubes were measured using THz-TDS and cw THz BWO-spectrometer in the frequency range 100 GHz – 2.2 THz and THz peak powers from microwatts to hundred kilowatts.
In this study, we developed a simple method for alcohol content analysis in fuel oils by Time-Domain Terahertz (THz) Spectroscopy. Frequency dependent absorption coefficients, refractive indices, and dielectric constants were calculated from the measurements of pure fuel oils and their mixtures with ethanol. Ethanol mixtures of gasoline were modeled successfully with a simple model in which the mixture...
We have investigated dielectric relaxation in aqueous ionic solutions by terahertz time-domain spectroscopy to elucidate the ionic hydration effect on the structure of water. Our finding suggests the dissolved ion induces the “structure breaking effect” which weakens the hydrogen bonding of water beyond the ion hydration shell.
Mode profiles, transmission attenuation and dispersion in flexible dielectric-lined hollow metallic cylindrical waveguides are analyzed experimentally and numerically. Using dielectric coatings made of different materials and different thicknesses, we show the crossover between the fundamental TE11 and TM11 modes and the hybrid HE11 mode.
Transmission-type THz-TDS was applied to characterize water on super-hydrophilic surface of anatase-TiO2 layer fabricated by plasma-assisted deposition. Absorption coefficient of water with the thickness of 300 mm on the layer was in good agreement to that of free water before the surface was converted to the super-hydrophilicity but decreased on the super-hydrophilic surface after UV-irradiation...
We report on the coherent control of terahertz (THz) spin waves in a canted antiferromagnet, YFeO3, associated with a quasi-ferromagnetic spin resonance at a frequency of 0.3 THz, using a single THz pulse. The intrinsic dielectric anisotropy of YFeO3 in the THz range allows for coherent control of both amplitude and phase of the excited spin wave.
Spiral antenna is widely used in THz regime as a ultra wide band-width feed for dielectric lenses. Indeed such antenna show a very flat behavior over a very wide band. Conversely these feeds generate very wide radiation patterns inside the lens which illuminate the lens in an inefficient way. In this contribution we want to show how is possible improving the performances of these types of antenna...
We study theoretically, numerically and experimentally deeply sub-wavelength dielectric ridge terahertz waveguides on the surface of finite size photonic bandgap structures. We show that their dispersion relation can be described in a numerically stable closed form. We present the fundamental properties of surface modes on multilayers made of silicon and cyclo-olefin copolymer and study them experimentally...
To confirm the feasibility of applying THz time domain spectroscopy (TDS) technique to nondestructive evaluation (NDE) of wood, the relation of relative permittivity to density for specimens of 12 wood species was investigated using THz-TDS transmission measurement system. The dielectric anisotropy, the difference in the relative permittivity in the fiber and transverse direction of wood, was also...
We present unique phenomena of enhanced transmission of terahertz (THz) waves through a self-organized eutectic metamaterial1. Our experimental results in combination with theoretical calculations show that the experimentally observed enhanced transmission is associated with sub-wavelength waveguiding within the dielectric rods lattice embedded in an epsilon-near zero polaritonic host.
The design and simulation of a dielectric lens for beam deflection in the terahertz range is presented. The device consists of a lattice of sub-wavelength holes in a rectangular dielectric slab, and by varying the radii of the holes with respect to position, a gradient index (GRIN) lens can be realised. Beam deflection is achieved by giving the refractive index a ramp-like characteristic. The lens...
A simple MM-wave imaging system based on high-performance metamaterial MM-to-IR converter and IR camera is proposed, theoretically and experimentally investigated. The energy conversion efficiency of MM waves into IR radiation is over 90%. The main characteristics of MM-wave imager are discussed.
We propose to measure the THz surface plasmon signal transmitted after a long distance propagation over a conductive sample in view of determining the THz properties of the sample material. We demonstrate this very sensitive method on a highly-doped silicon samples. The surface permittivity differs from the Drude model prediction.
We have measured the temperature dependent changes in the terahertz spectra of three different amorphous polyols: sorbitol, glycerol and xylitol. As samples of each material are heated from temperatures well below its glass transition temperature, Tg, to temperatures close to its melting point a clear change in absorption coefficient at Tg is observed in all three samples. In addition, the spectra...
We explore the degree to which infrared thermal emission can be tailored using an array of dielectric spheres coated with a negative permittivity material. The spheres themselves have absorption peaks in the IR. The emission spectrum is then modified using the arrangement of the spheres.
We have fabricated Sb2Te3 thin films, with different thicknesses by controlling the deposition times, using pulsed laser deposition. We studied the dielectric properties using terahertz time domain spectroscopy (TDS). The real and imaginary parts of the complex refractive index of Sb2Te3 thin films were presented.
We show that shrinking the transverse size of metallic waveguides always leads to solutions with extreme field confinement at THz frequencies, regardless of the materials used and of the system geometry. We provide a unified framework to understand such universal behaviors, which will benefit future developments in THz science and technology.
Terahertz imaging, is the latest entry into the crowded field of imaging technologies. Many applications are emerging for the relatively new technology. THz radiation penetrates deep into nonpolar and nonmetallic materials such as paper, plastic, clothes, wood, and ceramics that are usually opaque at optical wavelengths. In contrast to X-rays, the T-rays have large potential in the field of hidden...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.