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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.
This work proposes a new type of continuous-wave (CW) terahertz (THz) generation based on vertically integrated LTG-GaAs photomixer and Nanogrid-based transparent top bias-electrode. The THz output power can be increased by higher available photocurrents and smaller device capacitances. A suitable resonant antenna design is proposed.
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...
Intermediate frequency (IF) gain bandwidth (GBW) of terahertz (THz) heterodyne detectors based on superconducting niobium nitride (NbN) hot electron bolometers (HEBs) has been studied in details. Two different methods, resulting in same IF GBW value of about 3.5 GHz are reported here.
Nanomaterials exhibit unique properties and have been receiving considerable interest. The dielectric measurement has been performed on gold nanoparticle dispersions by using a THz-Time domain spectroscopy system to investigate the interaction of THz waves with gold nanoparticles.
We present results from wideband THz, low wave-number Raman, and FTIR measurements on benzoic acid and two of its derivatives. The low energy vibrational modes have been identified and compared with the results from calculations.
Scaled radar cross section measurements are a commonly employed tool in civil and military aviation. We propose a flexible setup which makes use of a fiber-coupled THz time domain spectrometer and a two circle goniometer. Measurements are performed on reference objects and on scale model aircraft.
The single metal wire (SW) is experimentally verified to be an competitive terahertz(THz) transmission line. Making use of the Modified Drude Model (MDM) based on the Sommerfeld theory, the transmission behaviors of Surface Plasmon Polaritons(SPPs) along SW are systemically investigated theoretically for axial symmetric and asymmetric modes. Some important physical phenomena are discussed, and the...
Influences of parameters on the nonlinear power are simulated by using a Hamiltonian model. Results show that the saturation power is mainly determined by the mismatched parameter, and optimum of the mismatched parameter increases the saturation power and shortens the saturation-interaction length. Also, higher beam current leads to a higher saturation power and shorter saturation-interaction length.
We present electrical rectification up to 300 GHz with novel asymmetric nanochannels realized for the first time on AlGaN/GaN material system. At zero bias, sensivities of 100 V/W/Hz1/2 are obtained at room temperature.
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