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We present sub-millimeter wave transceiver modules intended for imaging radar applications. In particular a novel circuit architecture that operates in homodyne FMCW radar mode will be highlighted [1], and the trade-offs between performance and circuit complexity will be discussed. The transceiver units are based on monolithically integrated Schottky diodes fabricated on 3 μm thick membranes. Radar...
Coherent detection of very weak THz signals is important in astronomy, spectroscopy, and communications. We report on coherent up-conversion of THz radiation into the optical telecommunication range. All resonant phase-matched conversion can be achieved in a whispering gallery mode (WGM) resonator. Furthermore we present first results on WGM resonators that can be coupled to both THz radiation as...
The miniature cold field emitters are very attractive for utilization in low-power gyrotrons operating in range of short millimeter and terahertz waves. But such emitters are usually nondurable when exploiting in technical vacuum. Multi-tip field emitters with protective coatings developed and investigated by the authors are promising for use in short-wave gyrotrons operating in a technical vacuum.
Scattered x-rays were utilized for determination of the electron energy distributions at a gyrotron collector. Performed calculations and experiments demonstrated that scattering in the diagnostic window has only minor effect on the radiation spectra in the gyrotron-relevant conditions. The primary advantage of the proposed diagnostic scheme consists in reduction of the density of treated x-rays flux...
A numerical procedure to implement non-reflecting radiation boundary conditions, based on the Laplace Transform, is described in details and tested successfully on a simple two frequencies test problem. The method is then implemented in the time-dependent gyrotron simulation code TWANG. In the case for which the code exhibits a multi-frequency spectrum with the same transverse mode, it is shown that...
Diamond windows have an important role in fusion power applications, as this material only currently enables both tritium confinement and transmission of mm-wave power in the MW range. Diamond window units are safety related components and therefore their integrity has to be guaranteed both during normal and accidental operation, like, for example, in absence of coolant flow. In this work, a beam...
First reported by our research group in 2007, AlN tunnel barriers grown by ICP nitridation of thin Al overlayers offer a promising alternative to Al oxide barriers for high current density SIS junctions used in quantum limited THz heterodyne receivers [1]. However, the growth rate of AlN is heavily dependent on ICP operating conditions and as new uncharacterized nitridation processes are investigated,...
We report on the development of a tunable antenna coupled intersubband terahertz (TACIT) detector based on GaAs/AlGaAs two dimensional electron gas. A successful device design and micro-fabrication process have been developed which maintain the high mobility (1.1×106 cm2/V-s at 10K) of a 2DEG channel in the presence of a highly conducting backgate. Gate voltage-controlled device resistance and direct...
We are studying resonant-tunneling diodes (RTDs) with strong back injection of electrons from collector into quantum well. Such RTDs exhibit large negative differential conductance and they operate up to 1.46 THz in oscillators.
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 have phase locked a 4.7 THz Quantum Cascade Laser (QCL) to a stable microwave reference signal. The QCL is a 3rd order distributed feedback (DFB) laser with a low power consumption of 0.5 W and radiation power of about 0.25 mW. One of the key elements in our experimental setup is a superlattice diode operating as a harmonic mixer and providing the beat signal between the QCL and the 24th harmonic...
The combination of a terahertz parametric oscillator and a large size surface-emitted injection-seeded terahertz parametric generator was used to generate nanosecond THz pulses. The obtained THz pulse energy at 1.74 THz was 6.5 µJ. This is the highest nanosecond THz pulse energy of the terahertz parametric sources.
We present the demonstration of the first traveling wave tube circuit fabricated using ultraviolet photolithography. The complete amplifier demonstrated over 60 W output power at 214.5 GHz with 15 GHz bandwidth in the small signal regime at 14 dB gain. A high-gain 233 GHz amplifier is now under development and predicted to reach over 100 W output power. We present several microfabrication advancements...
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...
Theophylline anhydrite single crystal thin enough for wide range THz transmittance spectroscopy could be grown by Temperature Difference Method in aqueous solution. Polarization dependent THz transmittance spectra of the crystal at 70 K were obtained by using a GaP CW THz spectrometer. Absorption lines existing at close frequency could be resolved each other successfully. Assignments of absorption...
In this paper, we present the particle-in-cell(PIC) simulation results of a novel Ka-band ring-shaped microstrip meander-line slow-wave structure(SWS). This study shows that, this miniature millimeter-wave power amplifier is capable of delivering an average output power greater than WOW within the bandwidth from 28 to 38 GHz, when the beam voltage and the beam current are 11411Vand 200mA, respectively.
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...
An optical steerable terahertz zone plate is achieved utilizing the localized distribution of the transient electron plasma on a silicon wafer. Its focusing and imaging performances are experimentally demonstrated. The research prompts the development of steerable optical imaging elements.
The analysis of petrochemical samples by Terahertz (THz) spectroscopy is investigated. THz spectroscopy is a nondestructive, contact-free analysis method for the study of many different materials. In this work, we show that the THz spectra can be used to get different chemical and structural information from a potential hydrocarbon source. Density of the geological samples has the potential for valuable...
This work demonstrates THz wave amplification in a non-linear MgO:LiNbO3 crystal using a parametric process. The amplifier has gain in excess of 55dB. This system has potential applications in non-destructive sensing and imaging of a wide variety of materials.
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