We report on transmission enhancement and suppression in rectangular aperture arrays at terahertz range. Experiments
and simulations reveal that transmission maxima and minima of metal film perforated with rectangular apertures arrays
are caused by the shape resonance and the interference between surface waves respectively. To further investigate the
relative contributions of shape resonance and interference between SPPs, we have examined the density of electrons
whose distribution property is identified to the normal component of E-filed which clearly shows that transmission
resonance stems from excitation of shape resonance at the edge of the hole. This resonance dominated by cutoff function
is responsible for resonance peak at transmitted spectrum. The interference of SPPs originated at surface further
enhances the resonances and gives a set of minima in the transmittance spectrum. This study contributes a better
understanding of fundamental physics behind the extraordinary transmission of aperture arrays at THz range and
provides a simple method for the design of THz devices.
We study a coaxial terahertz waveguide with low transmission loss and broad bandwidth. The coaxial transmission line is
composed of an aurum line in the center, which ento-ectad covered with Teflon layer, wire-mesh, and the dielectric layer
for protection. In this paper, we utilize the finite element method (FEM) to numerically analyze the transmission mode,
the attenuation constant, and the bandwidth of the waveguide. The major transmission properties of the coaxial terahertz
waveguide are calculated for different diameters of aurum axes and different thicknesses of dielectric layers. We also
compare two waveguides with different Teflon thicknesses for getting broader transmission bandwidth. The simulation
results indicate that the optimum dimension of coaxial terahertz waveguide is the aurum axes of 700μm diameter, the
Teflon of 900μm thickness. With these parameters, the average attenuation constant of the waveguide can be as low as
2.44 x 10-4 dB/m in the frequency range 1.0-2.2THz. As these excellent transmission properties and simple structure of
the coaxial waveguide, it can be expected that it will be widely used in terahertz wave communications and the
fabrication of terahertz system integration.
A terahertz time-domain spectrometer is employed to study various properties of jade, including the
kind identification and polarization analysis. The characteristic absorption spectra and refractive index
of jade are obtained in the range of 0.2 to 2.6 THz. Studying the absorption spectra and the
transmission temporal THz waveform with two peaks, which were confirmed to be coming from
ordinary and extraordinary beams, respectively, and result in fake absorption features. A practical ways
are suggested to remove the fake absorption features and therefore the real absorption spectra of jade
which accurately indicate the information of the samples can be obtained.
KEYWORDS: Absorption, Terahertz radiation, Spectroscopy, Imaging spectroscopy, Inspection, Quantitative analysis, Terahertz spectroscopy, Pharmaceutical inspection, Chemical analysis, Signal to noise ratio
A new method for quantitative analysis of mixtures of illicit drugs with THz time domain spectroscopy was
proposed and verified experimentally. In traditional method we need fingerprints of all the pure chemical components. In
practical as only the objective components in a mixture and their absorption features are known, it is necessary and
important to present a more practical technique for the detection and identification. Our new method of quantitatively
inspect of the mixtures of illicit drugs is developed by using derivative spectrum. In this method, the ratio of objective
components in a mixture can be obtained on the assumption that all objective components in the mixture and their
absorption features are known but the unknown components are not needed. Then methamphetamine and flour, a illicit
drug and a common adulterant, were selected for our experiment. The experimental result verified the effectiveness of
the method, which suggested that it could be an effective method for quantitative identification of illicit drugs. This THz
spectroscopy technique is great significant in the real-world applications of illicit drugs quantitative analysis. It could be
an effective method in the field of security and pharmaceuticals inspection.
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