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The reflection properties of porcine skin are examined in the terahertz (THz) frequency range utilizing a Fourier transform infrared spectrometer with a reflection unit. Their dependence on the frequency and other parameters such as the surface structure is analyzed in order to determine whether porcine skin can be used as surrogate for human skin in the THz frequency range.
Terahertz ATR spectroscopy was used to monitor the crystallization of sugar on confectionary products. The time-dependent spectroscopy could used to follow phase transition from the aqueous phase into a glassy state followed by a crystallization of the sugar on the ATR window. Terahertz pulsed imaging was also used to investigated the final product.
We report on the experimental and theoretical study of the Reststrahlen Band assisted photocurrents in epitaxial grown graphene on SiC. We show that excitation of graphene with infrared radiation results in a dc current. We demonstrate that photocurrent in response to linearly polarized radiation exhibit a resonance enhancement in the frequency range of the Reststrahlen Band of the SiC substrate....
We present a novel approach to determine the individual layer thickness in a dielectric multilayer sample using pulsed terahertz spectroscopy in reflection geometry. In a first step, the optical parameters of each layer have to be determined. Based on these parameters, we simulate the reflected THz-pulse from the multilayer system and compare it to the measurement. A genetic algorithm is used to determine...
A single flange 2-port TRL calibration and measurement setup for accurate THz S-parameter characterization of integrated membrane circuit devices is proposed. The proposed setup facilitates shorter access waveguides, which greatly improves the calibration uncertainty.
Terahertz pulsed imaging (TPI) was used to analyse the diffusion of water into hydroxypropyl methyl cellulose (HPMC) matrices as well as acrylate copolymer matrices in reflection. Using TPI it is possible to monitor the phase changes that occur in the polymer matrix, investigate the growth kinetics of the process as well as follow the water diffusion front as it propagates through the porous polymer...
Video-rate THz reflection imaging, at 450 GHz using a high-resolution INO 384×288 pixel camera core, of pills in blister packs further contained within their final commercial packages is reported. These results open the door to deployable real-time THz cameras for see-through imaging applications, providing a tool for NDE quality control and security inspection of goods within their final packaging.
In this work a compact microprobe for advanced chip-inspection applications is introduced. The probe features integrated photoconductive switches for Terahertz pulse generation and detection. Device application is demonstrated for contact-free high-resolution time-domain reflectometry measurements at silicon-chip test structures.
Terahertz (THz) has been well known for its unique ability to propagate through non-polar packaging material. At the same time, THz wavelengths are small enough to provide meaningful imaging resolution, leading to their large potential in non-destructive evaluation. Correlation processing is a technique that has been shown to detect phase resonances in illicit chemicals, and in this paper, is extended...
We use reflection THz spectroscopy to produce three-dimensional images of air gaps between stones that resemble fractures of sub-wavelength thicknesses.
We demonstrate a parameter extraction algorithm based on a theoretical transfer function, which takes into account a converging THz beam. We use material parameter extraction as a way to determine the angular profile of the apparatus.
It has been found that the sensitivity of the terahertz attenuated total reflection spectroscopy was enhanced five times by using a metallic mesh. Using this method, reflectances of various ionic solutions were measured. As a result of measurement, hydrated states of ionic molecules were evaluated.
Introducing antireflection slits at the boundaries of a finite-size coupled terahertz cavity in a metal air-gap waveguide can minimize reflections at the boundaries. The optimal design parameters for the minimal reflection were obtained using the one-dimensional antireflection coating theory and finite-difference time-domain simulations. We experimentally demonstrated that the optimized antireflection...
For the modeling and design of communication systems in the lower THz frequency range the propagation conditions need to be known. We show a comparison of ultra broadband channel measurements from 50 GHz to 325 GHz in different scenarios related to typical office and industry environments.
We study the terahertz response of vertically aligned carbon nanotubes (VA-CNT) using THz time-domain spectroscopy, in order to determine optimal conditions for their use as THz-based gas sensors. The morphology of such films must be considered to reconcile the reflected signals and extract the complex conductivity spectra.
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.
During tests of a megawatt-class 140 GHz gyrotron for the fusion experiment Wendelstein 7-X, a window RF arc was documented with a high-resolution spectral measurement system. The arc event coincided with strong perturbations of the nominal cavity mode TE-28,8 and a final mode switch to a neighbor mode. Simulations using a self-consistent interaction code (SELFT) have reproduced the main features...
We propose using frequency selective surfaces as resonant sensors for simultaneous measurement of several optical properties of thick films placed in contact with a flat part of the device. Changes in refractive index, losses and thickness of a film can be measured by detecting changes in the spectral position, and amplitude of the transmission peaks in the THz fiber spectrum. As an example, our simulations...
Future communication systems in the Terahertz range are promising very high data rates. Here a measurement setup designed for short intra- or range inter-device communication is presented. Exemplary measurement results are given for waveguide-like ABS structures. In addition the possibility to model the propagation properties with a ray tracing approach is evaluated.
Reflection and transmission properties of materials common in electronic devices are investigated for the frequency ranges of 50 GHz to 75 GHz as well as 270 GHz to 320 GHz. Material parameters are extracted by fitting the measurement results with Transfer Matrix Method simulations.
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