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Classical simulations of charge carrier motion within interconnected semiconductor nanoparticles help to characterize the effect of the connectivity between neighboring nanoparticles and of their size on the overall high-frequency photoconductivity spectrum of the nanostructure.
We present experimental and theoretical results on sub-harmonic mixing of THz radiation at 639 GHz with radiation at 213 GHz (both being high above fT) in an antenna-coupled silicon CMOS detector with a fundamental antenna resonance at 213 GHz. The measurements are analyzed in the context of distributed resistive mixing in the channels of the field-effect transistors.
The transient terahertz radiation emitted by a spin coherence optically generated in CdMnTe two-dimensional electron gases is directly measured in the time domain using electro-optic sampling. The spin radiation decays in a few ps at high magnetic fields. We also provide a full theoretical description within first principle calculations of both the generation of spin waves, precession and emission...
We report a novel chemical and biological sensing metrology by combining both frequency-domain terahertz and microfluidic techniques through the quasi-optical approach. Using this sensing platform, a variety of chemicals have been examined over the frequency range of 0.57–0.63 THz. In addition, real-time monitoring and THz mapping of two-stream mixtures and diffusions in a microfluidic device are...
We have studied the relationship between polarization independent terahertz transmission and structural folding angle of plasmonic slots. According to the research, the polarization independent terahertz transmission can be realized in a cross-shaped slot, since the transmission efficiency remains high even though the slot is strongly folded.
We use injection seeding to study the emission of THz quantum cascade lasers (QCLs) on picosecond time-scales. We find pulsed regimes for THz QCLs suggesting a gain recovery times from 10 to 40ps.
We report on THz emission measurements and low temperature scanning laser imaging of Bi2Sr2CaCu2O8 intrinsic Josephson junction stacks. Coherent emission is observed at large dc input power, where a hot spot and a standing wave, formed in the “cold” part of the stack, coexist. By changing bias current and bath temperature the emission frequency can be varied over a wide range of 350–780 GHz; the variation...
We report on the physical principles of operation of a passive terahertz imager based on Pb1−xSnxTe(In). First results on construction of such an imager are presented.
A polarization sensitive scheme of air-biases-coherent-detection (ABCD) is presented for THz-TDS to directly measure the amplitude and polarization angle of the THz filed, which provides a broad bandwidth coverage from 0.3 to 30 THz. All of the information of arbitrary polarized THz wave can be achieved with just single-scan detection.
We proposed a Terahertz waveplate made from plastic A4 transparency and artificial form birefringence effect, it was operating as quarter-waveplate at 330GHz; and as negative quarter-waveplate at 200GHz, and as full-wave waveplate at 270GHz.
A novel type of apertureless near-field microscopy using a knife blade as a scanning probe is proposed and investigated at millimeter wavelengths. Since the knife blade probe is a wider version of the metal tip probe commonly used in this technique, and therefore the interaction area between the probe tip and the sample is larger, an improvement in the intensity of the measured near-field signal,...
Spectral properties of straight hollow core Circular Tube Lattice Fibers in the THz regime are analyzed both numerically and experimentally. Good agreement between simulated and manufactured fibers is found proving that these fibers have high potential for THz applications. Finally, bending properties are investigated with FEM simulations, showing that low-order transmission windows are strongly robust...
The effect of bandgap opening on the intraband nonlinear optical response of graphene in terahertz frequency regime is theoretically investigated. The nonlinear optical response of gapped graphene is found to be sensitively influenced by the bandgap level and temperature.
In this paper, a novel sub-terahertz (THz) extended interaction klystron (EIK) is presented. With the help of a three-dimensional (3D) particle-in-cell (PIC) simulation, design and optimize geometry of THz EIK is performed, which is composed of ladder loaded rectangular waveguide. In present work, the operation center frequency of THz EIK is 94.5GHz, and the CW out power 524W is achieved, the efficiency...
In this paper, a new approach based on the transmission line cascading network, is proposed. It is used to analyze the high-frequency characteristics of ridge-loaded folded-waveguide slow-wave structure. The analytical results agree with those obtained by the 3-D electromagnetic high-frequency simulation software HFSS. It is indicated that the equivalent circuit method is reliable and high efficiency.
China is planing to construct a 5-m THz telescope (DATE5) at Dome A, Antarctic, which is the best site on the earth for astronomical observations in the THz regime. To evaluate the atmospheric transmission at Dome A, we have developed a broadband Fourier transformer spectrometer for 0.75∼15 THz (Dome A FTS). The details of the instrument and measurement results will be presented.
We have observed a significant enhancement in the electro-optic sampling efficiency for THz radiation by using focusing effect in a metallic tapered parallel plate waveguide and also an optical waveguide in LiNbO3 employed as an EO crystal. The total enhancement factor exceeds an order of magnitude as compared to the case with a bulk LiNbO3 crystal coupled with a Si prism.
This paper is devoted to the comparative study of the motion stability of the electrons with off-axis guiding centers in FELs with a conventional and reversed guide magnetic field. Results show that the trajectory divergence mainly comes from the first harmonic of the 3-D wiggler field, and can be effectively suppressed by use of the reversed guide field.
By applying a helical electric field along a plasma region, a revolving electron current is formed along the plasma and an elliptically polarized far-field terahertz wave pattern is observed. The observed terahertz wave polarization reveals the remarkable role of velocity retardation between optical pulses and generated terahertz pulses in the generation process.
A design of subwavelength terahertz waveguides is presented in this manuscript. The structure is composed of a linear chain of split-ring resonators (SRRs), i.e., artificial magnetic atoms. The energy transport along the chain can be described by magnetic plasmon propagation sustained via magnetic dipoles and conductive coupling. The simulation result shows a slow-light effect with minimal loss over...
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