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A gyrotron was constructed with an inside quasi-optical system to convert the wave into gaussian beam. The experiments showed an output power of 23.9kW while the frequency was 95.1GHz, which was in accordance with the design. The threshold current and the output power under different parameters were measured, which showed some discrepancies at parts of the charts between the calculations and the experiments,...
We present an analytical model carefully describing the time-frequency behavior of all the stages composing our whole Terahertz Time Domain Spectroscopy laser based system, from the THz pulses generation via Optical Rectification, to their detection through Electro-Optic Sampling technique, by way of diffraction, collecting and focusing effects. In order to prove the effectiveness of our work, we...
We investigate the spectral broadening of the transmitted radiation of conically tapered apertures made in a split metallic plate. We further propose a tapered shell structure to realize strong broadband field concentration.
The design of dielectric wedge-scanned millimeter wave lens antennas with measured results is presented. The diffractive lens antenna (DLA) is treated; it incorporates a lens that transforms the radiation pattern of a scalar feedhorn. A schematic diagram of a zoned dielectric wedge-scanned DLA with Fresnel spherical surface is presented. An efficient device for scanning the beam produced by a DLA...
In this paper, we have microfabricated a 6.4 mm diameter silicon lens array on a 4 inch silicon wafer using silicon micromachining technique. The goal of this lens array is to build a 2×2 lens antenna array for 1.9 THz receiver application. It requires multiple thick photoresist coatings and long selective etching of silicon and photoresist after thermal reflow process. To the authors' knowledge,...
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The experimental study of the quasi-optical mode convertor for 0.42THz, TE26 mode terahertz gyrotron has been carried out. The results show that the power conversion efficiency is more than 80%, and the gaussian content of the field at the output window is about 80%.
We show the coherent detection of the laser emission from seeded terahertz (THz) quantum cascade lasers (QCL) with metal-metal waveguides using free-space coupling of a THz pulses to the sub-wavelength waveguide. We implement a simple, monolithic planar horn antenna design on the metalmetal waveguide that reduces the impedance mismatch to the waveguide. The laser emission is seeded and coherently...
We report on the development of a 4.7-THz local oscillator (LO) for the heterodyne spectrometer GREAT on SOFIA. The design of the LO and its performance in terms of output power, frequency accuracy, frequency stability, and beam profile as well as its implementation in GREAT will be presented.
We investigate the ion effect on 1, 2-ditetradecanoyl-sn-glycero-3-phosphocholine lipid hydration with attenuated total reflection terahertz time domain spectroscopy. The absorption difference between lipid solutions and buffers (water and NaCl solution) shows that lipid-ion interaction accelerates the water reorientation motion confined in nanometer scale structure.
The "Abbe barrier" may be completely broken by curvilinear (conical) 3D diffractive lenses with unique 3D super resolution (∼0.4λ0 and ∼0.8λ0 for transverse and axial respectively), but in contrast to the flat diffractive optic the curvilinear 3D diffractive conical optic allow to overcome 3D Abbe barrier with focal distance F more than F>2λ.
Intense terahertz pulses are used to investigate nonlinear carrier dynamics in Au thin films with different morphologies. From THz field-dependent transmission measurements, we found that the conductivity in percolated Au nanostructures increases with increasing the incident field strength. The measured complex dielectric dispersion was analyzed using the Drude-Smith model to discuss the dynamics...
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...
Optimizing high-power ultrashort pulse amplifier using double-clad Yb-doped fiber, maximum output power of >3 W with a pulse width of 110 fs without pedestal component is obtained. Using this pulse, high-power high-efficiency broadband THz pulse generation is expected.
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)...
The design of a 340GHz two-beam folded waveguide (FW) traveling-wave amplifier with >4 W of power over with the input power of 20mW is presented. The amplifier is driven by two electron guns (70mA×2, 14.9kV) and 1T magnetic field. The design is performed by CST Particle Studio. Particle-in-cell (PIC) simulations were carried out to predict and optimize the performance of the folded waveguide TWT.
We present recent work to develop and demonstrate nanosatelite technologies for earth atmospheric remote sensing using microwave radiometry. Microwave instrumentation is particularly well suited for nanosatellite implementation, as the sensor requirements for power, pointing, and spatial resolution (aperture size) can be accommodated by a nanosatellite platform. The Microsize Microwave Atmospheric...
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