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We experimentally observe broadband Terahertz pulse propagation in flexible metal helix waveguides. Our measurements are in very good agreement with finite-difference time domain simulations. The waveguides have a constant attenuation coefficient of 0.2 cm−1 in the region between 0.3 and 0.9 THz. The measured temporal signals indicate that the THz pulse is confined to the core of the helical waveguide...
We propose a novel THz material analysis approach which consists of a combination of a stratified dispersive model, an appropriate measurement configuration and a time-domain based fitting procedure. The measurement configuration is modeled as a stratified system where for each layer the light-matter interaction is realistically described. The method is illustrated for the industrial quality control...
A square helix slow wave structure is proposed for high gain millimeter wave TWTs. The electromagnetic characteristics of this structure are calculated by HFSS. It is shown that, compared with the equivalent circular helix with the same cross section perimeter, the square helix structure holds higher interaction impedance and lower normalized phase velocity, which indicates higher output power and...
A theoretical model for the arbitrarily-shaped groove staggered double-grating array waveguide (SDGAW) slow-wave structure (SWS) is used to calculate the characteristics of dispersion and coupling impedance for a step-shaped staggered double-grating slow wave structure for W band TWT application. The results are compared with those obtained by CST-MWS code simulation.
Propagation of a pulse THz radiation through molecular gas mediums has series of features. In the paper three of them (giant light speed reduction, commensurate echoes, and non-Faraday rotation of polarization) are presented. The effects were measured directly in real time by a powerful pulse radiation of the Novosibirsk terahertz free-electron laser and our ultrafast detection technique.
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.
A three dimensional (3D) linear theoretical modal for a sine waveguide sheet beam travelling wave tube is developed based on the field matching method. The dispersion curve for a 0.22THz sine waveguide slow wave structure is given. The effects of the beam parameters on the beam-wave interaction are discussed.
In the summer of 2011, I was awarded a Consolidator Grant by the European Research Council titled “Advanced Antenna Architectures for THz Sensing Systems (AAATSI)”. The grant lasts 5 years and is aimed at solving the “antenna dispersion problem”: i.e. improving the efficiency x Bandwidth product in THz antennas. To achieve this goal an enhanced Fourier Optics methodology is being developed and three...
An original integral method (MR-GEC) based on an impedance operator and orthogonal wavelets is developed to overcome the drawbacks of the moment method through the analysis of dispersion characteristics of shielded microstrip lines.
Studies are presented of a series of computer simulations, using CST (Microwave Studio), of novel waveguide components for a mm-wave gyro-TWA. Each component has a range of operation that can be optimised through observations of the S-parameters and the phase data, while altering geometric parameters in the simulations. This approach allows optimum performance of mm-wave gyro-TWAs.
Using the simple unified theory, the beam-wave interactions are analyzed in high-power Cerenkov-type microwave generators composed of periodic metal slow-wave structure (SWS) with a magnetized plasma column.
Cold test results of a G-band sheet beam backward wave oscillator (BWO) with a double grating waveguide, fabricated by wire cutting and a 3D printing technique, are presented in this paper. The dispersion curve and S-parameters of the BWO slow wave circuit and Bragg reflector were measured and the results compared to the numerical modelling and analytical theory.
The qualitative and quantitative analysis of amino acids by terahertz (THz) refractive index spectra is discussed. The frequency band of anomalous dispersion emerging in the spectra is unique for the amino acids, L-glutamine (Gln) and L-histidine (His). The refractive indices of the amino acids were found to be linearly proportional to the concentrations. The calibration models were established to...
We demonstrate a low-loss terahertz waveguide Bragg grating (TWBG) fabricated using a plasmonic two-wire waveguide and a micromachined paper grating for potential applications in THz communications. Two TWBGs were fabricated with different periods and lengths and investigated experimentally. TWBG modal dispersion relations, modal loss, and field distributions were studied numerically. Additionally,...
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