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Single-cycle Terahertz transients at high fields are a powerful tool to explore fundamental properties of condensed matter and ultimately to initiate coherently collective processes by nonionizing light [1]. While intense pulses at mid-infrared frequencies between 20–100 THz (15 μm–3 μm) have been demonstrated [2], the production of high-energy single-cycle pulses with fields of several MV/cm in the...
Control of terahertz (THz, 1 THz=1012 Hz) wave is still a big challenge in the THz community. We present here a flexible coding metamaterial, which is composed of “0” and “1”elements, i.e., 1-bit coding case, to shape the reflection and scattering of THz wave. The far-field patterns can be varied by adjusting the digital sequence. We also demonstrate a low-reflection-and-scattering metamaterial, which...
A fast rotary delay line is fabricated and characterized for terahertz (THz) frequencies. With this new device, we present dynamic measurements of spray painting process and fast moving objects detection along with thickness determination.
We consider superradiance from an extended relativistic electron bunch moving in a periodically corrugated cylindrical waveguide for the generation of multi-megawatt terahertz pulses. To study this process, we have developed a self-consistent, quasi-optical theory which includes a description of the formation of evanescent wave near a corrugated surface and its excitation by RF current induced in...
Optically controlled mode switching in the split-ring resonators deposited on the lattice-matched InGaAs/InP was demonstrated at excitation wavelengths 900–1200 nm. Using tunable excitation wavelength as well as split-ring resonators of different configurations attempts were made to optimize the mode switching conditions for application of tunable metamaterial for high-speed narrow-band THz modulation.
We realize the relativistic Doppler reflection of THz light from a counter-propagating plasma mirror in silicon (Si) with a practically simple geometry, which allows us to easily apply the frequency up-shift to the THz optics. The average frequency of the reflected THz light is 1.4 times higher than that of the input THz light. In view of application, the important facts are that the frequency up-shift...
Based on 16QAM modulation, a 2×40 Gbps wireless communication demonstration system using 0.14 THz band oritho-mode transducer (OMT) is presented in this paper. The OMT is used for polarization division multiplex (PDM) transmission of the 0.14 THz band wireless link. The measured cross polarization discrimination (XPD) of the designed OMT is more than 30 dB at 0.14 THz band, while the insertion loss...
Using terahertz spectroscopy we investigate the charge transport in Sb-doped SnO2 nanoparticles pressed into pellets. Doped and undoped samples are shown to have different mechanisms of intrinsic conductivity. We systematically study the influence of annealing on intra- and inter-nanoparticle charge transport.
Debris on the airport surface such as on runways may cause severe damage to aircraft. To detect these obstacles, we have been developing a radio-over-fiber (RoF) connected foreign object debris detection 96 GHz millimeter-wave radar system. This paper discusses the fundamental field evaluations of the developed RoF based radar system at Sendai Airport. The radar transmission signal is delivered to...
Utilizing THz wave to transmit data for communication and imaging places high demands in phase and amplitude modulation. In this paper we combined a metamaterial array with HEMT structure to form an ultrafast electronic grid-controlled THz modulator. By controlling the carrier concentration of 2DEG, a resonant mode conversion between two different dipolar resonances has been realized. In the real-time...
Thermistor mounts are served as transfer standards which are calibrated in microcalorimeter. A correlation between the effective efficiency of thermistor mount and the relative humidity of the laboratory has been observed. The difference of effective efficiency measurement in 20% and 50% humidity level can be about 9 times the k=1 uncertainty. The effects of humidity on thermistor mounts can result...
This paper presents a novel differentially-driven planar aperture antenna for circularly-polarized (CP) radiation. The proposed antenna is simple in structure and is constructed on only a single layer laminate using standard printed-circuit-board (PCB) technology. Circular polarization is realized by rotationally-symmetric windmill-shaped aperture-strip formation with travelling wave distribution...
We characterized a 3THz continuous wave generated by photomixing two optical modes of a broadband optical frequency comb. This optically generated THz wave and the output beam of a 3THz quantum cascade laser phase-locked to a THz reference were coupled onto a hot electron bolometer mixer operated at 4K and the beat signal was precisely evaluated. This direct comparison at 3THz reveals that the optically...
We propose a novel bandgap fiber for the transmission of terahertz (THz) radiation based on a Kagome lattice of air holes. The fiber core comprises a triangular lattice of air holes having the same or a smaller size than the cladding air holes. Numerical simulation of a 19-cell fiber is carried out using finite element method. Proper design of the fiber parameters allows the transmission of broadband...
In this work we describe the effect of the electron momentum relaxation time on the terahertz properties of periodically-patterned graphene plasmonic structures; more specifically, its effect on the quality of the characteristic plasmonic resonances. From analytical theory as well as numerical simulations, it is observed that the electron momentum relaxation time heavily affects the quality factor...
In this paper, the thermoelectric conversion power sensor, which is the key part in the WR-6 (110 GHz–170 GHz) rectangular waveguide microcalorimeter, was designed and evaluated. The ANSYS simulation software was used to evaluate the quantitative relation between the THz power and DC power for the power sensor.
Terahertz (THz) metamaterials have recently attracted much interest due to their ability to tune propagation properties using sub-wavelength structures. In this paper we demonstrate the first metamaterial device developed by patterning a vanadium dioxide (VO2) wire-grid structure onto a c-sapphire substrate. Temperature and polarization dependent THz time-domain spectroscopy transmission measurements...
Through integrating materials susceptible to optical intensity and electric field, the self-resonance and coupling of individual meta-atoms have been tailored with different excitations, achieving the dynamical modulation of broadband plasmon induced transparency, adjacent coupling and Schottky effect in terahertz metamaterials.
We demonstrate high-performance THz QCLs lasing at 2.2, 2.53, 3.5 and 4.7 THz, which target absorption lines of water, methane, hydroxyl and atomic oxygen respectively. Reliable single-mode targeting of gas species is obtained through the use of a photonic lattice design. A highly reproducible micro-machined waveguide block yields narrow beam-divergence and enables future integration of a complete...
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