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This paper presents the comparative study on the gyrotron cold-cavity simulation for a 94 GHz gyrotron using commercially available PIC codes: MAGIC and VSIM. The purpose of this paper is to prove the reliability and accuracy of the VSIM tool in gyrotron cavity simulations by comparing its results with the MAGIC results. We have carried out the cold cavity simulation of a 94 GHz gyrotron for TE6, 2...
The Facility for Accelerator science and Experimental Tests (FACET) at SLAC National Accelerator Laboratory provides a 23-GeV high charge, sub-picosecond bunched electron beam that is ideal for pulsed THz light generation in the few-THz range. Pulsed THz lights based on coherent transition radiation have been demonstrated at FACET, with high peak electric field and high pulse energy. The intense TeraWatt...
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...
Recent simulation and experimental work has resulted in the realization of low-cost, substrate-based, THz wire-grid polarizers fabricated on crystalline-quartz substrates that exhibit both high extinction ratios and low insertion losses. The broad bandwidth performance of these high fill-factor wire-grid polarizers are characterized using terahertz time-domain spectroscopic techniques over a frequency...
With the development of high power magnetron, cathode is researched a lot to endure higher temperature and intense electron bombardment. In order to decrease the central part temperature of cathode in magnetron and extend magnetron's lifetime, a kind of variable pitch helical cathode is proposed in this paper. Computer simulations are adopted to verify whether cathode surface electric field distribution...
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 report the first observation of THz-field-induced electromigration in sub-wavelength metallic gap structures after exposure to intense single-cycle, sub-picosecond electric field transients of amplitude up to 400 kV/cm.
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...
Near-field electric field distribution in the Sierpinski metallic bow-tie antenna is determined by the terahertz microscope system. The resonance frequency clearly depends on the location, indicating site-selective local-field enhancement due to the self-similarity of the fractal structure.
Many potential applications of THz-Time Domain Spectroscopy in science or industry call for highest acquisition speed and stability. Our approach of single-shot detection provides the full temporal information on the ultrashort THz electric field with variable window of several 10 picoseconds at kHz repetition rates. We use this technique to image moving objects and to study transient phenomena.
The effect of cathode emission nonuniformities on electron beam quality in gyrotrons and a method for suppressing this effect by optimization of the electric field distribution in the gun region are studied experimentally and using computer modelling.
Negative-type liquid crystal material, which has an inverse dielectric anisotropy for the low frequency, is introduced on a microstripline for modulating its dielectric constant with low driving voltage and low power consumption. Since the molecular orientation response for the driving voltage is inverted in comparison with positive-type LC materials, the transmission MMW phase magnitude decreases...
Terahertz photoconductive antenna arrays with interdigitated electrodes are laid down on GaAs substrates in which different geometries are assessed for their ability to enhance performance of a time-domain spectrometer (TDS) system.
A systematic study of strained SrTiO3/DyScO3 heterostructures was performed using time-domain terahertz spectroscopy in the temperature range from 20 to 294 K. Interdigitated electrodes deposited on top of the structures allowed probing of the terahertz response upon an applied electric field. We explored a possibility to increase the total thickness of SrTiO3 layers while maintaining the epitaxial...
Surface plasmon polaritons at the n-GaN/vacuum interface are investigated. Experimental studies of terahertz radiation reflection and emission are performed on heavily silicon-doped GaN epitaxial layers grown on sapphire substrates. To provide interaction of THz radiation with the surface plasmon polaritons, a regular grating was fabricated on the outer surface of the epitaxial layer. Study of terahertz...
We demonstrate ultrafast temporal slicing of phase-locked multi-THz pulses using a photoinduced electron-hole plasma in germanium. This approach enables us to extract single-cycle transients with a peak electric field of 10 MV/cm from a multi-cycle waveform at a carrier frequency of 24 THz.
We experimentally show that metallic dipole antennas emit ultraviolet radiation when illuminated with ultrashort high-power terahertz pulses due to ultrafast electron field emission from the metal and consecutive ionization and excitation of atmospheric gas molecules.
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