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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...
Terahertz time domain spectroscopy has been used to characterize various tissues in biomedical research to date. In this paper the terahertz properties of three groups of rat skin tissues treated with different injections (normal saline control, high dose of Dotarem, and high dose of Omniscan) are measured. The difference in terahertz properties of the tissues can be clearly observed from the results.
Plasma generated in discharged noble gases has been successfully used for terahertz (THz) wave detection. We theoretically analysed the detection mechanism, and found the electrons in the weakly ionized plasma can obtain energy from the incident THz radiation and convert excitation collisions of electrons with excited neutral atoms into ionization collisions, so the ionization current increases. An...
In this study, we utilize Terahertz imaging to study the effects of hydrofluoric acid on both compact bone tissue and cartilage. We compare the differences observed in the exposure for formalin fixed and raw, dried, tissue as well as those resulting from a change in Hydrofluoric (HF) concentration. Measurements are performed with THz-TDS, and a variety of spectroscopic based image reconstruction techniques...
The terahertz range of the electromagnetic spectrum falls between the more familiar microwave and infrared regions. Advances in pulsed terahertz technology over the past decade have led to the development of commercial instrumentation for spectroscopy and imaging. Terahertz analysis is non-destructive for materials as well as living tissue and its high depth of penetration offers many advantages over...
For electron cyclotron resonance heating of the stellarator W7-X at IPP Greifswald, a 140 GHz/10 MW cw millimeter wave system is in construction. Two out of 12 launchers will employ a remote-steering design. This paper describes design issues like input coupling structures, manufacturing of corrugated waveguides, optimization of the steering range, integration of vacuum windows, mitrebends and vacuum...
Photoconductive Terahertz microprobes have been crystalized as powerful measurement tools for high-resolution conductivity imaging, chip inspection and near-field imaging applications. In this work we demonstrate their integration into a high-speed system with 250 pixels/s data acquisition rate.
This paper describes an example of using a compact Terahertz (THz) system to analyze the layered structure of a composite plastic samples in a non-destructive manner. Time-domain data is analyzed to measure the thickness of each layer of the sample and determine the presence or absence of adhesive bonding the plastic parts. The presence and position of the adhesive is clearly visible in the THz images...
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.
Antenna-coupled field effect transistors have been developed as plasma-wave THz detectors in both InAs nanowire and graphene channel materials. Room temperature operation has been achieved up to 3 THz, with noise equivalent power levels < 10−10 W/Hz1/2, and high-speed response already suitable for large area THz imaging applications.
We present a detailed study of the influence of time jitter in terahertz time-domain measurements. It proves to be particularly important in TDS based imaging measurements and can strongly influence the quality of the images.
Dispersive imagers measure multiple speckle realizations of the object to be estimated. This poses a challenge for coherent imaging as classically objects are backpropagated and then despeckled. We present initial findings on an intensity based method for estimating the scattering density.
Techniques to retrieve reliable images from complicated objects are described, overcoming problems introduced by uneven surfaces, giving enhanced depth resolution and improving image contrast. The techniques are illustrated with application to THz imaging of concealed wall paintings.
In this work we present a novel concept for fast and low-cost terahertz imaging. A fast and stable source for time delay is created by inserting a rotating piece of high-density polyethylene into the THz path of a terahertz time domain spectrometer [1]. We will present the specifications of a first implementation of this device as well as imaging examples.
We present our investigations of solar cell mini modules and metal interconnects using terahertz time-domain spectroscopic imaging. It was demonstrated, that time-domain data can be used to reveal the thickness variation of encapsulating layers and height difference of metal contact surfaces in a vicinity of shunts.
We characterize InGaAs Schottky barrier diodes (SBDs) with a variation in the anode size. High-efficiency terahertz (THz) pulse detection of the InGaAs SBDs is performed in the cases of anode diameters of 2 µm and 3 µm. The uniformity of the fabricated 1 × 20 InGaAs SBD array is measured to be fine. The THz imaging results using the 1 × 20 InGaAs SBD array are presented.
A high-speed room temperature THz imaging system is developed. The sensor consists of an array (64×64) of plasmonic semiconductor detectors. The detectors have broadband responsivity of up to 20 V/W in the frequency range 10 GHz – 1 THz. Pixel-to-pixel deviation of the sensor parameters is not larger than 20%. The sensor with an amplification electrical circuit provide shot times of 100 ms. The sensor...
We designed and fabricated Nb5N6 microbolometers integrated with five staircases square diffractive lens array (DLA) for THz detection. It gives us a method for designing diffractive lens to improve the coupling efficiency of the incident power into the Nb5N6 microbolometers. We measured the voltage response of the Nb5N6 microbolometer integrated with diffractive lens. We find it has 30 times larger...
We investigate the use of real-time THz camera imaging for differentiating between benign and malignant tissues in major human tissue groups. Using broadband time-domain THz spectroscopy, we discriminate between tumor and nerve margins on the basis of different THz refractive indices and reflectivity. Particular focus is given to easily accessible malignancies, such as skin, larynx, esophagus, and...
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