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Absorption spectra of smoke produced from polyvinyl chloride (PVC) and molded charcoal at high temperature are investigated between 500 and 950 GHz. Observed peaks at 626 GHz for PVC and at 692 and 921 GHz for molded charcoal are respectively assigned as the spectral signature of hydrogen chloride and carbon monoxide contained in smoke. Smoke from molded charcoal also showed absorption peaks of hydrogen...
In the paper we show that under the excitation of a line current, a dielectric medium loading in the lower half-space of the sub-wavelength holes array brings surprising changes to the diffraction radiation. In the lower half-space, the surface wave becomes a radiation wave. The fundamental space harmonic is transformed into Cherenkov radiation with unique characteristics and the first negative space...
We demonstrate the ultra-fast detection of terahertz pulses from a quantum cascade laser (QCL) using superconducting NbN and YBCO detectors. This has enabled both the intrapulse and interpulse dynamics of a THz QCL to be measured directly, including interpulse heating effects on sub-µs timescales.
Passive millimeter-wave microscopy that enables imaging of the thermal radiation emitted from a viewed sample with a spatial resolution below the diffraction limit is investigated. Experiments performed at 50 GHz (λ = 6 mm) at various sample temperatures demonstrate the feasibility of our passive millimeter-wave microscope to image thermal radiation even in the low temperature range where passive...
We have developed the λ/4 phase-shifted 1.3-µm dual mode laser as an optical beat source of continuous-wave (CW) terahertz (THz) generation. The mode beat frequency is continuously tuned from 230 to 1485 GHz via integrated micro-heaters. The CW THz system is also demonstrated with low-temperature-grown InGaAs photomixers.
While most scientific experiments take place in a controlled laboratory environment systems for industrial applications have to cope with instable temperatures. We investigate the performance of InGaAs/InAlAs THz antennas for the temperature from −20 to 80 degrees Celsius.
We demonstrate the concept of an anti-rod dimer planar metamaterial with strong birefringence and optical activity in the THz range. The retrieval of circular transmission components shows an asymmetric transmission effect for right-to-left and left-to-right polarization conversion.
This study proposes a theory to separately diagnose the beam-wave dynamics of backward wave (BW) and forward wave (FW) interactions in the frequency-tunable gyrotron. It is clarified that the BW interaction would dominant the feedback mechanism regardless of the cavity structure resonance. The FW interaction effect is found to be minor in small signal regime but critical in the large signal regime...
In this paper, the dumbbell resonant cavity frequency tuning method and beam wave interaction system of W band sheet beam Klystron (WSBK) has been studied. Under the designed value of beam voltage 75kV, beam current 3.8A, and beam size of 10*0.5 mm2, the structures and high frequency parameters of single gap and multi-gap cavities are tested and discussed to achieve the higher output power in detail...
Terahertz absorption spectra were measured for nylon-6/6, nylon-6, nylon-11 and nylon-12 by Fourier transform far-infrared spectroscopy. Different spectral features among the four species were interpreted as the characteristics of crystalline conformations of nylons.
We report on our terahertz study of the reduction effect on graphene oxide films grown on fused silica substrates by spin-coating. The optical characteristics before and after thermal reduction were studied by terahertz time-domain spectroscopy.
We performed terahertz time domain spectroscopy on erbium orthoferrite. The spin reorientation transition was observed as switching of magnetic radiation mode between F and AF mode, and the change in the polarization of the radiation.
Terahertz (THz) reflection spectroscopy has the potential to extract unique spectral signatures from various materials of interest, but these signatures can be distorted by rough surface scattering, low signal strength, and alignment errors. One method of addressing these challenges and increasing gain is to coherently combine information across frequency bands. This method, called correlation processing,...
We present a THz scattering-type scanning near-field optical microscope (THz s-SNOM) system. To estimate pure material resolution of our THz s-SNOM system, near-field images were obtained for embedded metallic grating. The pure material resolution of our THz s-SNOM system was estimated to be less than 100 nm.
We demonstrate the phase-locking of a 2.5 THz Quantum Cascade Laser (QCL) to an air-propagating, 6 octaves-spanning, THz Optical Frequency Comb Synthesizer (OFCS). We directly observe the beating signal using a commercial detector, therefore proving that this approach provides a mature metrological tool in the THz region. We show that only a small fraction (<100 nW) of the radiation emitted...
We report on the method that terahertz generation and detection were simultaneously performed via non-collinear optical parametric interaction in a nonlinear crystals using a Si-photodiode. The bandwidth manipulation between broad 3.3 THz and narrow 45GHz bandwidths was demonstrated at single quasi-phase-matching crystal using the position-dependence of the crystal.
A VOx microbolometer detector coupled with thin-film spiral antenna was fabricated by metal-organic decomposition. Temperature coefficient of resistance of the microbolometer was 4.7 %/K at 300 K and the responsivity was 120 V/W for 94 GHz electromagnetic wave radiation at a bias current of 0.5 mA.
We report the measured performance characteristics of a broadband (0.2 – 10 THz) bolometer instrument based on thin film superconducting technology. The technology is designed for operation both in liquid helium cryostats but also in an electrical cooling platform. We report a number of significant advantages that accrue to superconducting technology compared to semiconductor devices. Single pixel...
We demonstrate high-efficiency terahertz pulse generation via optical rectification in LiNbO3. We avoid the spectral broadening of an excitation pulse via the stimulated Raman scattering process by the bandwidth control of the excitation pulse and achieve the highest efficiency of 0.21% for energy conversion into THz pulse.
Data processing of Terahertz signals for reliable explosives detection via Terahertz time-domain spectroscopy is investigated. Wavelet denoising, wavelet power spectrum estimation, and wavelength selection show promising results. Experiment results for Composition B-3 and Pentolite are presented.
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