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In this paper we present an all-fiber THz spectrometer based on the OSCAT technique. We investigate its application to non-destructive testing in the polymer industry and analyze a set of polymer samples with different contents of TiO2 as a filler.
We propose a Terahertz quarter waveplate operating at the upper Terahertz band, it is designed with artificial form birefringence through etching micro-grating structures on the high resitivity silicon by using laser micro-fabrication method.
We report on the fabrication of unipolar nanodiodes into an InAs/AlxGa1−xSb quantum-well heterostructure for room temperature microwave detection up to 110 GHz. Electron-beam lithography was combined with both dry- and wet-etching, and we explored the differences in the electric and detection parameters with the two methods.
We present a novel miniature module for terahertz attenuated total reflection spectroscopy. It is made of high resistivity silicon by applying free form optics fabrication and features two parabolic surfaces which act as the sensitive interfaces. Fiber coupling of highly integrated emitter and detector chips provides a high degree of flexibility.
We report on the field ionization process of accepters in p-Ge under intense terahertz (THz) electric field. Broadening of the accepter absorption lines followed by disappearance is observed below 10 kV/cm. In the strong field limit, one can see clearly Drude dispersion. This implies that the THz field ionization takes place quite faster than 1 ps.
Photomixing is an attractive solution for high resolution spectroscopy, nevertheless it has suffered from a lack of frequency metrology to determine the line centre frequencies. Frequency combs can provide excellent metrology of lasers, hence we propose a photomixing source that is phase locked to a frequency comb to overcome this problem. The resulting instrument has an accuracy of ΔνTHz/νTHz = 10...
This paper presents a method for terahertz pulse manipulation. A pair of temporally separated and orthogonally polarized pump lasers is coincident on a (110)-oriented ZnTe crystal. The amplitude and polarity of the terahertz pulse generated based on difference frequency mixing can be controlled by adjusting the temporal separation between the incident pulses. Theoretical derivation and simulation...
New classes of photoconductive THz emitters based on Apollonian as well Sierpinski fractals and their complementary counter parts are presented. It is shown that for each fractal class the emitted THz radiation power increases as the fractal order is increased. It is shown that the self-similarity of plasmonic current present on the antenna surface results in superior performance compared to conventional...
We have measured the dependence of effective mass and electron mobility of high quality n-type (0001) GaN wafers on carrier density in the range of 8×1015 ∼ 8×1017 cm−3 by using THz time-domain magneto-optical ellipsometry. The carrier density dependence of mobility agrees well with the theoretical prediction for low dislocation density sample.
The effect of solvent on the carrier transport in poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) was studied by the combination of THz time-domain transmission spectroscopy (0.1–3 THz) and the broadband reflectance spectroscopy (4–800 THz). While the broadband reflectance showed a plasma edge in the near infrared, the frequency dependence of the THz conductivity of PEDOT:PSS...
The thickness dependence of the terahertz absorption in Bi(001) ultrathin films has been investigated. Both the average carrier density and the damping constant of the plasmon increase as the thickness becomes thinner. The results are consistent with the existence of the surface metallic states.
Carbon Nanotubes show high potential as an additive for polymers to improve mechanical properties and conductivity. For their employment in compounds, a homogenous distribution is crutial. We present THz spectroscopy as a tool for Nanotube content and homogeneity measurements.
We propose diagonally arranged terahertz macrocells for the realization of high Q-factor resonators. Our results show that the double-SRR diagonal macrocell structure exhibits an improved quality factor, while a spectral collapse is noticed for the triple-SRR diagonal configuration. The experimental results are in good agreement with the simulations.
This paper presents a new design for a fully dielectric microwave Lens. The proposed 94GHz lens is silicon-based and has an efficiency of ∼40%. By using side grating for reflection the lens size has been cut into half. The whole structure was optimized using Genetic Algorithm.
The THz emission point on a nonlinear electro-optical crystal for generating broadband THz radiation is modeled as a radiating Gaussian aperture. With the wavelengths of the infrared pump beam being much smaller than the wavelength components of the generated THz pulse, a THz sub-wavelength radiating aperture with Gaussian profile is effectively created. This paper investigates this general modelling...
This paper will describe the new feature, temporal particle-in-cell analysis in Beam Optics Analyzer in detail. Algorithms for pushing particles and field solution will be discussed. Numerical results for a diode as well as a gridded electron gun will demonstrate the implementation.
We apply mid-infrared near-field microscopy with broad-band spectroscopic operation to problems in biomineralization. Inspecting tooth material we find vibrational resonances of phosphate nanocrystals distinctly shifted from bulk phosphates. This is enabled by the extraordinary spectral narrowing promoted by the near-field interaction over far-field FTIR.
A novel power meter operating from 0.1 to 0.2 THz is presented. The power meter has utilized a thin-film metamaterial inspired absorbing layer. This absorber has the desired characteristics such as ultra-wide bandwidth and strong absorption. In a bolometer-like measurement setup, it functions as a wideband high-responsivity THz detector. The absorbing layer consists of a low loss thin dielectric membrane...
In order to enhance the radiation power of the evanescent wave, we adopt double-negative metamaterials (DNMs) to study the electromagnetic radiation at terahertz region in the half-space problem. Numerical results clearly show that the radiation power of the evanescent wave can be greatly enhanced at terahertz frequencies over the normal material case when reversed Cherenkov radiation occurs in the...
We report on experimental observation and theoretical analysis of magnetic-field and gate-voltage tunable magnetoplasmon resonances in grating-gate GaN/AlGaN-based field-effect transistors suitable for detection of THz radiation.
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