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We report a novel approach using terahertz (THz) photo-induced coded-aperture imaging (PI-CAI) technique to characterize a WR-1.5 (500–750 GHz) diagonal horn antenna at 590 GHz. The measured antenna beam profiles show decent Gaussian shape and propagation properties, as expected. Antenna far-field radiation patterns extracted from beam images agree well with theory and simulation. On the basis of...
Bow-tie antenna coupled field-effect transistors have been implemented in 0.25 μm AlGaN/GaN process technology and have been mounted on an aplanatic hemispherical silicon substrate lens. By asymmetric coupling of 590-GHz radiation to the channel, the transistors are used as direct power detectors, achieving system noise-equivalent power values of 166 pW/√Hz at 590 GHz (referred to the total beam power)...
A dimer is the simplest form of cluster that exhibits some of the salient properties resulting from coupling interactions between the particles. The semiconductor nanodimer is a self-contained nanostructure supporting the intensification of the local electric field as a result of plasmon resonance and proximity effects. By means of a simulation framework based on charge transport analysis for the...
We use unpolarized synchrotron radiation to probe the temperature dependent transmittance of single crystal Sr14Cu24O41 in the spectral range 15–110 cm−1 (0.45–3.3 THz). At high temperature we identify a conductivity band, which we assign to hole hopping between neighboring chains. At low temperatures we identify 14 resonance bands, 11 of which are previously unreported. Analysis of the absorption...
The extended interaction oscillator (EIO) is regarded as a novel type of high power terahertz (THz) source, which has promising application prospects in radar, medical imaging etc. Up to now, CPI and other institutes have developed many types of EIO. For satisfying with the application request, the EIO with operation frequency exceeding 300GHz is designed and studied with three-dimensional particle-in-cell...
Structures based on a periodic surface lattice (PSL) of planar geometry have been studied. It is shown that volume and surface fields can couple to form a cavity eigenmode, demonstrating the potential for novel mm-wave sources when combined in appropriate configurations with an electron beam.
The analytical expressions of the beam-wave coupling coefficients, the beam-loaded conductance and bunching current in the multi-gap coupled cavity are derived based on space-charge wave theory. Through calculating those expressions in a Ka-band three-gap coupled cavity for modes 2π, π and π/2 respectively, the mechanism of the beam-wave synchronization and coupling in the three-gap coupled cavity...
We show that due to Rashba spin-orbit coupling two-dimensional semiconductors can exhibit strong nonlinear optical response in the terahertz frequency regime. The spin-split of the parabolic energy band in semiconductors allows multiple-photon process to occur via inter-subband transitions. The steplike edges in the optical process correspond to the cut-off effect produced by the multiple-photon process.
We experimentally demonstrate single-mode broadband THz propagation in hollow core waveguides fabricated with a 3D printer with metallic inclusions. The measurement data obtained from the Terahertz (THz) Time Domain spectroscopy experiments show low loss guidance and low dispersion characteristics, and these are in very good agreement with the results obtained from numerical simulations of the investigated...
We present a novel method for calculating the linearly polarized mode contents in an overmoded corrugated waveguide. The proposed method is based on calculating the low order irradiance moments of the measured radiated intensity profiles at several distances from the waveguide aperture. The method is validated by the data measured from a 63.5 mm diameter corrugated waveguide at 170 GHz and a 19 mm...
This study is aimed at development of a moderate power sheet-beam traveling wave tube (TWT) amplifier with grating slow-wave structure (SWS). A fast and accurate code for calculation of eigenwaves in the grating SWS is developed, and results of numerical modeling of a G-band TWT are presented. Electron gun producing an intensive sheet electron beam is developed. Beam focusing and transportation is...
We investigate through numerical simulation the coupling properties of a novel, AC-coupled, contact-free probe. The new probe couples radiation from a CPW-embedded device-under-test via polarization current, which is then transformed to conduction current in the probe and down-converted in frequency to baseband by an optically-pumped photomixer. Numerous simulations have been realized in order to...
Backward wave oscillation modes in a TE01 Gyro-TWT are researched by a nonlinear theory with consideration of electrons misalign. The results show the output power of most oscillation modes decreases with the increment of misaligns distance.
Terahertz metamaterial technique enables a sophisticated electromagnetic excitation of materials. Here, we demonstrate resonant excitation of spin precession motion of canted antiferromagnet ErFeO3 using the magnetic near-field produced by split ring resonator (SRR). When the resonance frequency of spin precession was near the magnetic resonance mode of SRR, we observed substantial increase of precession...
We implement optical pulse shaping into a photo-conductive antenna (PCA) based THz time domain spectroscopy (THz-TDS) system using fiber coupling between emitter and pulse shaper. We use phase-only pulse shaping for the generation of bit patterns. An additional phase mask is applied in the pulse shaper to cancel dispersion introduced by the optical fiber. The generated waveforms are coupled into a...
Whispering gallery mode (WGM) resonators have high Q factors and small modal volumes and can thus show strong non-linear interactions. Most of the interesting non-linear materials are crystalline and feature high refractive indices such that efficient coupling to the resonator is challenging. We present a study on high refractive index WGM resonators and show that coupling via a crystalline dielectric...
A two-stage oscillator consisting of two coupled three cavity klystrons is studied. A small-signal theory of this oscillator is developed, which predicts start-oscillation current and oscillation frequency. Results of 1-D particle-in-cell simulation of the W-band oscillator are presented. The numerical results are in good agreement with the small-signal theory. The simulations predict over 400 W output...
Classic analog of the electromagnetically induced transparency (EIT) in metamaterials has been demonstrated extensively by its attractive potential applications in light storage, slow light and sensing. However, the counterpart of EIT, electromagnetically induced absorption (EIA) has been studied rarely in coupled metamaterial systems. Here, we present the observation of the EIA effect in a vertically...
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