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We report on our waveguide hot electron bolometer (HEB) mixer development for the heterodyne focal plane array receiver upGREAT, which is the multi-pixel extension to the German Receiver for Astronomy at Terahertz frequencies (GREAT) currently in operation on the Stratospheric Observatory for Infrared Astronomy (SOFIA). We will present results for our new generation of HEB mixers for operation at...
We suggest to use the effect of cyclotron resonance absorption for modulation of microwave signals. Stationary signal transforms into the sequence of soliton-like pulses during interaction with rectilinear electron beam. For operating frequency of 250 GHz output pulses can possess subnanosecond durations.
The detailed characterization of a modular 260GHz, frequency-tunable, CW-gyrotron equipped with a matching optics unit allowing full-polarization control of the rf-wave is presented. The integration of the gyrotron-system with the NMR spectrometer is outlined.
We present our results on THz pulse generation in the 0.1–2.5 THz band via optical rectification of femtosecond laser pulses in a tapered crystal. A simulation study for visualization of THz wave propagation in the crystal has been performed. It is shown that the mode structure and phase velocity of the THz wave in the crystal are changed.
We propose a novel way to actively control the propagation of THz Surface Plasmon Polariton (SPPs) in plasmonic waveguides structured on semiconductors. The SPP characteristics (field confinement and mode propagation length) can be precisely tuned by optically pumping charge carriers to the conduction band of the semiconductor. This approach can be used to generate active and integrated THz components...
We propose a simple THz wave plate based on the structured parallel metal plates. The fast and slow propagation properties for TE and TM waveguide modes bring in the controllable birefringence in wide frequency region. Using this optics, we experimentally obtained intense single-cycle THz pulse with the circular polarization.
We experimentally study THz evanescent wave coupling in an array of parallel-plate waveguides in close proximity. We observe stronger coupling with larger plate separations and longer propagation paths.
For electron cyclotron resonance heating of the stellarator W7-X at IPP Greifswald, a 140 GHz/10 MW cw millimeter wave system is in construction. Two out of 12 launchers will employ a remote-steering design. This paper describes design issues like input coupling structures, manufacturing of corrugated waveguides, optimization of the steering range, integration of vacuum windows, mitrebends and vacuum...
In this work a compact microprobe for advanced chip-inspection applications is introduced. The probe features integrated photoconductive switches for Terahertz pulse generation and detection. Device application is demonstrated for contact-free high-resolution time-domain reflectometry measurements at silicon-chip test structures.
We demonstrate a single-pole single-throw switch in W-band based on the optical illumination of a defect waveguide in a photonic crystal. Simulations show that an extinction ratio of greater than 40 dB between 89 and 101 GHz is possible. Measurements at 99 GHz confirm this extinction ratio.
A method for the in-situ characterization of spurious modes in high power microwave transmission lines is presented. It uses hole couplers, which are integrated into a mitre-bend. The signals are proportional to the field strength at the mirror and allow to partly reconstruct the mode spectrum in the waveguide. The theoretical background is presented as well as results from measurements on prototypes.
Results on THz pulse generation in the 0.1–2.5 THz band via optical rectification of femtosecond laser pulses in a wedge crystal are presented. The finite-element method was employed to model and simulate the THz wave propagation in a LiNbO3 wedge antenna in order to analyze experimental results; and to visualize how the form of the crystal influences the THz radiation both inside and outside the...
Here, we report on planar photonic transmitters employing high-speed 1.55 µm photodiodes. Within the 200–300 GHz band, the device exhibits a 6-dB bandwidth along with a polarization penalty of ∼2.2 dB. Besides, the chip area is reduced thanks to a novel integration approach in the antenna structure.
A fundamental 1.9–2.8 THz Schottky diode mixer has been modified to enable high harmonic mixing, thus allowing use of the mixer for phase locking of a quantum cascade laser (QCL) to an stable external microwave source. Phase locking to a reference will transfer the spectral line profile of the reference to the THz source; this will control the phase precisely. Stabilizing a QCL for a single frequency...
A new 154GHz/ 1MW gyrotron was developed and installed in the Electron Cyclotron Resonance Heating system of LHD. The maximum output power of 1.16MW/ 1sec was achieved. Total injected power into a plasma reached 4.4MW with the existing three 77GHz gyrotrons' power. The 154GHz gyrotron contributed to extend the plasma parameters to higher temperature and density region.
Introducing antireflection slits at the boundaries of a finite-size coupled terahertz cavity in a metal air-gap waveguide can minimize reflections at the boundaries. The optimal design parameters for the minimal reflection were obtained using the one-dimensional antireflection coating theory and finite-difference time-domain simulations. We experimentally demonstrated that the optimized antireflection...
Terahertz quantum cascade lasers with tapered waveguide structure are reported. It is found there is an optimized tapered angle with which the peak output power of the devices with same total length reaches the maximum. The far-field divergence of the laser beam depends on the tapered angle as well as the driven current. The existence of the optimized tapered angle and the current-dependent far-field...
We developed vertical emitting THz QCL sources having an optical resonator based on a quasi-periodic patterning of the top metal layer of a double-metal waveguide. The designed pattern induces a distributed feedback effect capable of providing optical feedback as well as vertical extraction in a sharply collimated far field.
We present a terahertz quantum cascade laser providing 875 mW two-facet output power in pulsed mode, at a frequency around 4.7 THz and at a heatsink temperature of 10 K. The laser has a single plasmon waveguide. The active region is based on four quantum wells with longitudinal optical phonon extraction.
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