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We report on intense, tunable, continuous, and coherent THz electromagnetic waves observed from differently shaped triangular mesas of the intrinsic Josephson junctions in single crystalline high-Tc superconducting Bi2Sr2CaCu2O8+δ. All samples are fabricated by focused ion beam milling.
A tunable double-channel narrowband terahertz filter integrated with parallel plate waveguide cavities is described. The filter is formed by machining two rectangular grooves into upper and bottom plates of parallel plate waveguide, respectively. Tuning is achieved by a relative lateral shift of two metal plates with rectangle grooves. Simulation results show that both the resonance frequency and...
Multi-line far-infrared (FIR) gas lasers from a single laser cavity have been development in order to apply ITER diagnostics. By using two pump CO2 lasers with different wavelength and mixed gas of CH3OH and CH3OD, we succeeded in the simultaneous oscillations of three-color FIR lasers of 48, 57, 119 µm in wavelength.
In order to study the nonlinear beam-wave interaction for sheet beam klystrons more efficiently, a calculation code of SBK2D based on a 2D rod shaped macro-particle model is developed and used to simulate and analyze a high power W-band sheet beam klystron with 8 multiple gap barbell cavities. More than 50kW high frequency output with the efficiency of 20% and gain of 38 dB are observed, and the results...
A W-band reflective gyrotron backward wave oscillator (Gyro-BWO) is fabricated to systematically study the physics of competition between backward wave and forward wave. Two cavities, namely a single cavity and complex cavity, will be tested. Theoretical investigation indicates that the competition in a complex cavity is much improved and is capable of generating much stronger efficient radiation.
Nonresonant tunneling in short-period InAs/AlSb superlattices (SLs) was studied. Several equidistant maxima appeared on current-voltage characteristics of the SLs were shown to be due to the influence of optical cavity on optical transitions within quantum wells (Purcell effect).
Design and results of experimental tests of a high-power sub-terahertz gyrotron with a pulse solenoid for remote detection of radioactive materials are presented. Operating frequency corresponds to the atmospheric transparency window (0.66–0.67 THz). The 200 kW output power in pulses up to 30 microsecond duration were obtained.
Pseudospark electron beams of micro-sizes have been measured recently and their application to millimeter-wave and terahertz radiation generation is being investigated. A three cavity 94 GHz klystron using a micro-sized beam has been designed and simulated and is currently being constructed.
A complex cavity with gradual transition is employed in the 94 GHz gyrotron. A self-consistent field nonlinear theory has been used and numerical simulations for electron beam interaction with RF modes are given. A pulse output power of 235.2 kW is obtained by simulation at a beam voltage of 60 kV with beam current of 10 A, a velocity ratio of 1.45, and magnetic field 17kG, corresponding to an efficiency...
A new dual port input coupler structure is designed and simulated in 140GHz confocal waveguide Gyro-TWT amplifier. The input coupler can transform the input rectangle waveguide mode TE10 to operation mode HE06 in the confocal waveguide and give the speed modulation to electron beam. The efficiency of the mode power transform is about 70%. The band width of simulation is about 4GHz. The simulation...
Gyrotron FU CW CI is developed as one of sub-THz gyrotrons included in the FU CW series. The advantage of the gyrotron is compactness using a compact superconducting magnet and compact power supply system, which makes the accesses of the gyrotron to applied large-scale devices easier and extends the applications of gyrotron to wider fields. The designed frequency and cavity mode are 394.5 GHz and...
It is important to keep the frequency of higher-frequency operating mode twice or triple as large as that of the lower-frequency operating mode in the dual-frequency operation terahertz coaxial gyrotron with two electron beams. From the practical point of view, the effects of a possible tilted or shifted inner rod of a coaxial gyrotron cavity on the ohmic loss distribution, the resonant frequency,...
We report a very compact, laser diode-pumped, frequency-tunable THz source (1.65 – 2.65 THz) based on Stimulated Polariton Scattering in Mg:LiNbO3. The system operates with very low threshold (∼ 2.5 W diode pump power) and outputs a maximum average power of 6.45 µW at 2 THz, at a pulse repetition frequency of 3 kHz.
Using a cavity based on a periodic-surface-lattice (PSL) the concept of a high-power, 200GHz Cherenkov source is developed. If the PSL satisfies certain defined conditions single mode operation is observed.
A longitudinal computer-generated hologram is incorporated into the Fabry-Pérot cavity of a terahertz quantum cascade laser which displays two distinct spectral gain peaks. The combined cavity and hologram feedback mechanisms lead to digitally selective dual-mode emission with a difference frequency which may be electronically tuned from 190 GHz to 267 GHz.
The multi-frequency gyrotron are under development in JAEA. Oscillations at 170 GHz, 137 GHz and 104 GHz are demonstrated with the Gaussain beam output. At present, 0.9 MW/70 sec, 1.1 MW/5 sec were obtained at 170 GHz. In parallel, a fast frequency control was demonstrated between 170 GHz and 167 GHz using a super-conducting sweeping coil.
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