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Terahertz (THz) imaging and tomography are modern imaging techniques allowing 2D and 3D inspection of objects over a broadband frequency range. However, the transfer of this technique to medical applications is limited to surface or subsurface inspection due to the large concentration of water molecules which are an intrinsic characteristic of biological tissues. Then, we report the results of investigations...
We show that the mechanism of structural arrest in colloidal dispersions can be revealed by the dielectric properties at THz frequencies. This opens ways to in situ study layered dispersions, which cannot be probed with existing techniques. This vivid topic in colloidal science is moreover of high relevance for applications such as quality control of functional materials.
In this work, the concept of a solid-state amplifier based on the slow-wave interaction with drifting electron flow in a metal periodic structure is proposed for application in the low THz frequency range. Results of calculations at 330 GHz show the linear gain up to 50 dB/cm, including ohmic losses in the metal.
This work presents the performance analysis of a compact electrical permittivity sensor based on monopoles-coupled Split Ring Resonator to measure the dielectric properties changes in liquids. The sensor was designed and fabricated on standard FR4 substrate with a dielectric constant εr=4.4 with 1.56 mm of thickness and the optimized dimension of 35 × 50 mm2. Simulation results are made using finite...
We report on a technique for tuning a resonant frequency and enhancing transmission of a bull's eye (BE) plasmonic antenna by forming dielectric materials on a sub-wavelength aperture. We observed that the use of the dielectric material shifted the peak frequency of terahertz (THz) transmission through the aperture and also enhanced the transmittance. These results indicate the usefulness of dielectric...
Optical damage of congruent lithium niobate (LiNbO3) is a long-known problem. A popular method to limit this damage is doping LN with magnesium. Here, the dielectric permittivity of pure and magnesium-doped lithium niobate was characterized depending on the crystal orientation over a broad frequency range: 1 mHz to 0.75 PHz (λ=300 nm), using impedance measurements, quasi-optical free-space characterization,...
Surface Plasmon Polariton Light Radiation Source (SPCLS) combines electronics and photonics to generate coherent, enhanced and tunable radiation ranging from terahertz to ultraviolet. To further improve its performance, an extension structure of SPCLS (ESPCLS) is proposed: two silver films with different thickness are deposited on two dielectric substrates to establish a new unsymmetrical structure...
Precise temperature-control is necessary for many spectroscopic measurements. We present the temperature-dependent complex THz refractive index of liquid samples measured in a flowcell, analysed by a numerical method that allows simultaneous extraction of the sample's thickness to verify the temperature-stability of the cell.
We experimentally demonstrate an isolator suitable for the THz spectral regime. The isolator is designed by combining a polarizing beamsplitter with a quarter-wave plate, both based on the same artificial-dielectric technology. The artificial-dielectric medium comprises of a stack of 30 μm thick metal plates that form an array of parallel-plate waveguides. The isolator exhibits an isolation of 52...
Today X-ray tomography and Ultrasound Synthetic Aperture Focusing Techniques are representative examples for defect imaging in the field of nondestructive testing. THz time domain spectroscopy (TDS) operates with short electromagnetic pulses. The sensitivity of the pulses to optical material property changes makes THz-TDS attractive for the detection of flaws in dielectric materials. Unfortunately,...
Five cuvettes for extraction of dielectric parameters of low absorbing liquids are assembled and characterized. A test liquid is used for a statistical determination of the experimental error of refractive index and absorption coefficient as a consequence of mounting, cuvette fabrication, and characterization errors.
Graphene has been shown to be capable of supporting surface plasmon polaritons whose frequency is in the terahertz regime. We demonstrate that, due to the enhanced energy of surface plasmon in graphene, an optical bistability can occur in an air-graphene-dielectric structure.
This paper considers Terahertz (THz) sensing of contents on a single-layer object with time-domain spectroscopy (TDS) in a reflection mode. With an extremely small pulse width, the THz-TDS sensing is highly sensitive to non-ideal configurations such as a tilted or uneven sample, depth variation due to mechanical scanning operations, and intra-layer reflections. One consequence is sweep distortion...
Free standing films of bacterial cellulose and its composites with conducting polymer complex PEDOT/PSS have been studied by terahertz time-domain spectroscopy. Considerable increase in the imaginary part of dielectric permittivity of bacterial cellulose films modified with the conductive polymer with respect to that of pristine bacterial cellulose films was found out.
A dielectric loaded cavity operating in TM012 mode is designed to be used as electron injector into a THz accelerator. The designed cavity works at 360 GHz and uses about 3mJ of Thz energy. The designed gun is capable of generating electron bunches with 200 keV average energy. The bunch length and the transverse emittance of the bunch at gun exit are 5 μm and 25 π nm rad respectively. Furthermore...
In this paper we present the development of a noninvasive method for the evaluation of the degree deterioration of the diabetic foot using terahertz time domain spectroscopy. The study is based on the monitoring of hydration of the skin on the sole of the foot.
The origin of fast relaxation water in the terahertz frequency range have been elusive for years. In this contribution we have experimentally investigated the change in dynamical structure of water in salt solution using broadband dielectric relaxation spectroscopy (DRS) in the GHz to THz region to study the fast water. Numerical simulations have been conducted to quantify the dynamical properties...
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