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Library of paint pigments in 120–0.9 THz spectral range was created using FTIR spectrometer with fixed optical components. Library will allow remote identification of unknown pigments in objects of art.
We discuss measurement system and method for establishing traceability of terahertz (THz) power to NIST standards over a 0.3 to 7.5 THz range. In addition, we describe the performance of an electrically-calibrated thermopile detector, which is used as the NIST standard for THz power measurements. Specifically, we present measurements of the reflectance and spatial uniformity of the thermopile detector.
Considering the frequency dispersion of the complex dielectric permittivity for metals, the accurate radar cross section (RCS) of a copper sphere is given from microwave to the optical frequency. By investigate the effects on the RCS caused by the dispersion of metals, we show that polished copper sphere can be treated as perfectly electrical conductor (PEC) for the RCS prediction at terahertz frequencies.
In this study, we have investigated the temperature dependence of the optical conductivity of poly(3,4-ethylenedioxythiophene): poly(styrene-sulfonate) (PEDOT:PSS) films measured by the combination of THz and infrared-visible spectroscopy to understand the effect of the ethylene glycol (EG) on the carrier transport. The addition of EG to the PEDOT:PSS colloidal dispersion significantly improve the...
Parallel T2 weighted multi slice multi echo (T2w MSME) 7T Magnetic Resonance (MR) scans and terahertz (THz) surface reflectance maps were acquired of a full thickness skin burn in a rat model to investigate the spatiotemporal evolution of terahertz reflectivity in wound responses. A comparison of uninjured and injured regions in the burn neighborhood demonstrates a 3-fold increase in T2 relaxation...
Millimeter-wave (MMW) holographic imaging has been demonstrated effective for security surveillance, especially for personnel surveillance. However, coherent effects, such as speckle, and the low signal-to-noise (SNR) may destroy image clarity and make it difficult for automatic target recognition. In order to improve the image quality of MMW image, an iterative reconstruction method based on total...
A novel fast-scanning Fabry-Perot spectrum nalyzer is presented that uses substrate-based, wire-grid olarizers as the reflectors. One improvement over previous esigns is the continuous tuning of the reflectivity, and hence pectral resolution, via the angular orientation of the wire-grid xis with respect to the incident polarization. Another mprovement is the ability of these polarizing reflectors...
We present a novel active millimeter wave imaging technique that can be used to estimate target surface and reflectivity. This technique requires no mechanical scanning but requires only a sparse array of detectors. The illumination beam requires no focusing or collimation. The reconstruction is based on the time of flight information from the reflected signal.
Electromagnetic modeling predicts that dielectric substrate windows placed above a tissue of interest alter the hydration sensitivity of reflective THz imaging systems. Furthermore, interference effects between layers (the window with the skin layers) cause the window's optical path length to change the depth probed by the imaging system. A pulsed THz imaging system operating at ∼ 500 GHz was used...
Image reconstruction with high resolution based on incoherent detection and phase retrieval algorithm was proposed in Terahertz band. Proof-of-principle experiments were performed to demonstrate the effectiveness of the novel approach, which has potential applications in non-destructive detection of materials with low system cost and complexity.
We have carried out an experimental and theoretical study of the optical transmittance in terahertz to infrared regime of graphene multilayer on Si substrate under moderate electric field. It is shown that graphene multilayer on Si substrate has low resistance at room temperature, less than that of the silicon alone. The theoretical and experimental results also show good convergence at short and...
The n-type Ge-on-Si epitaxial material platform enables a novel paradigm for plasmonics in the mid-infrared, prompting the future development of lab-on-a-chip and subwavelength vibrational spectroscopic sensors. In order to exploit this material, through proper electrodynamic design, it is mandatory to retrieve the dielectric constants of the thin Ge epilayers with high precision due to the difference...
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