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Intermediate frequency (IF) gain bandwidth (GBW) of terahertz (THz) mixers based on superconducting niobium nitride (NbN) hot electron bolometers (HEBs) has been improved. The IF GBW has been measured by 2 different methods and same values up to 7 GHz have been obtained.
We discuss basic considerations for and recent developments of short-range THz communication systems which may replace or supplement present WLAN systems in 15 to 20 years from now.
A U-shaped quasi-parallel-plate (QPP) slow wave structure (SWS) for 1 THz backward wave oscillator (BWO) has been investigated in this paper. The radio frequency characteristics and beam-wave interaction of the structure are calculated. The results show that such BWO can operated at a low voltage (< 10 kV), and potentially be used in THz wave radiation source.
The design of a high power gyroklystron amplifier operating with circular TE011 cavity modes is presented. The amplifier will be driven by a 70-kV, 6-A electron beam with a pitch angle (vt/vz) of 1.4 and velocity spread of 2.4% generated by a double-anode magnetron injection gun (MIG). The amplifier is predicted by particle-in-cell simulation to generated 145 kW at 94.1GHz with 35% efficiency, 38-dB...
A gyrotron traveling wave amplifier (gyro-TWA) with a cusp electron gun and a helically corrugated waveguide operating in the W-band is presented. When driven by an electron beam of energy 40 keV and current 1.5 A, the simulated microwave output power is 5 kW (CW) with a 3 dB frequency bandwidth of 90–100 GHz and a saturated gain of 37 dB. Linear analyses, numerical simulation and the latest experimental...
This contribution presents the design of a dual polarized leaky lens antenna coupled to a Kinetic Inductance Detector (KID) in order to enable a broadband THz detector for future space applications. The designed antenna presents high aperture efficiency and clean symmetric patterns.
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...
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...
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...
We propose an achromatic wave plate in the high THz frequency region based on the artificial medium. It is composed of the stacked parallel metal plates with a pillar array, which bring in the controllable birefringence in an effectively lossless medium. We experimentally demonstrate that the artificial medium operates as the quarter wave plate from 2.05 to 3.26 THz.
We developed a THz imaging system based on a broadband thermal source (at 500 °C) and an asymmetric semiconductor nanochannel, the self-switching nanodiode (SSD), as a room-temperature detector. The maximum resolution was better than 0.5 mm full width at half maximum. The radiation was coupled to the SSD through a microantenna, whose geometry determined the frequency bandwidth of the system. While...
We performed THz pulse generation and detection beyond 4 THz by using a 1.04-μm Yb-doped fiber laser with a pulse duration of 480 fs. Owing to higher-order nonlinear processes in LiNbO3 crystals, THz pulses can be emitted with a bandwidth extending beyond the excitation pulse limitation. Emitted THz pulses are detected by using a stable sampling pulse that is temporally compressed by an optical fiber.
CMOS Technology for THz communication has been discussed in recent years, however many practical challenges remain for such data-links to be commercialized. We provide a brief overview of the wireless market and where THz may and may not fit in. Also, while the RF issues of THz links are well known, even more difficult issues in the baseband and modem still need to be addressed. This article discusses...
We present a time-domain terahertz spectrometer based on 1550 nm fiber laser technology and InGaAs photoconductive switches. The system features a voice-coil delay stage, which offers a high scanning speed of up to 60 traces per second. Owing to a precise reconstruction of the time axis, the system achieves a high dynamic range: a single pulse trace of 50 ps is acquired in only 44 ms, and transformed...
We investigate the pump-power dependent emission bandwidth of a CW THz emitter which is based on intra-cavity difference frequency generation in a two-color vertical-external-cavity surface-emitting laser. Two Michelson interferometers are employed to investigate the two color laser output and the originating CW THz signal, respectively. This allows a study of the optical modes which contribute to...
A novel slow wave structure (SWS) called sine ridge waveguide (SRWG) has been proposed for a wideband high-power terahertz radiation source. The cold bandwidth of the SRWG is similar to the sine waveguide structure. Meanwhile, the interaction impedance of the SRWG is about 70% higher than sine waveguide at 0.65THz with the same dimensional parameters. Furthermore, it possesses low ohmic losses and...
In the summer of 2011, I was awarded a Consolidator Grant by the European Research Council titled “Advanced Antenna Architectures for THz Sensing Systems (AAATSI)”. The grant lasts 5 years and is aimed at solving the “antenna dispersion problem”: i.e. improving the efficiency x Bandwidth product in THz antennas. To achieve this goal an enhanced Fourier Optics methodology is being developed and three...
We report the observation of negative group delay in a simple anisotropic cylindrical waveguide in the millimeter-wave region. With a 45° linearly polarized input, a relatively broad band of negative group delay was observed with 3.57% bandwidth, where the maximum group advancement achieved was about 24 times greater than the luminal delay, implying a fractional advancement of 13.32%. The peak advancement...
A highly efficient terahertz photoconductive antenna (THz-PCA) has been developed as a wideband terahertz detector for terahertz time-domain spectroscopy (THz-TDS) systems with a periodic bias line structure to remove unwanted reflections and enhance the frequency resolution. This novel THz-PCA is characterized in a THz-TDS system using a 100 fs optical pulse excitation from which a terahertz pulse...
We have analyzed the effects of LO phase noise on submillimeter-wave (submm) spectrometers. The phase error integrated from half the spectrometer bandwidth must be < 45 degrees to not distort the spectrometer response. For a phase noise spectrum with f−3 rolloff, the noise level at 1 MHz offset must be < −96 dBc for a 100 kHz spectrometer channel width.
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