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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.
The paper describes the method of modelling a microstrip transmission line fabricated on FR-4 substrate in the GHz frequency range. The model is based on the real part of high frequency complex electric permittivity of the dielectric measured with THz time domain spectrometer. The microstrip measurement results are used to analyse the model accuracy.
A dual-frequency laser coupled to a unitravelling carrier photodiode is used to produce a highly coherent THz wave. THz signal is detected by a subharmonic mixer coupled to an electrical spectrum analyzer. All components involved in this experiment operate at room temperature and no active stabilization is used. The measured linewidth is better than 30 kHz and tunable from DC to 1 THz. The dynamic...
A low frequency magnetic excitation in Cu3Bi(SeO3)2O2Cl has been studied through complementary spectroscopic techniques which utilised terahertz radiation from a synchrotron, a mercury arc lamp, and a two-colour photomixing system. The excitation has been studied at temperatures down to 5K and in magnetic fields up to 10T.
Latest results from a second harmonic gyro-TWA experiment at Strathclyde University are presented. The Ka-band experiment uses a helically corrugated waveguide. Simulations have been performed to predict the amplifier gain and bandwidth. The simulations are compared to laboratory measurements of the cold waveguide dispersion using a new, improved design of polarization converter.
We present experimental and theoretical studies on terahertz (THz) notch filter having a wide THz frequency range and low-pass filter (LPF) having a 0.78 THz cutoff frequency. The notch filter has a dispersion-free and low-loss transverse magnetic (TM) mode. On the other hand, the cut off frequency of the LPF was determined using a Bragg stop band, which depends on slit period.
We have experimentally investigated the terahertz (THz) transmission properties of metalized-film attenuators (MFAs) with base film thicknesses of 6 µm and 25 µm. Transmittance of the MFAs was measured by a THz time-domain spectrometer. Good flatness and repeatability of the transmittance were verified for the 6 µm-thick MFA in the frequency range up to 3 THz.
The Smith-Purcell radiation (SPR) in metallic metamaterial grating is studied theoretically. This metallic metamaterial is a one-dimensional array of slits with sub-wavelength period perforated on a perfect metallic film, which supports discrete guided modes in presence of convective electron bunch near its surface. It is also found that SPR intensity is enhanced when guided modes couple with diffraction...
Results on identification of liquids by a Josephson detector with a dielectric waveguide coupling are presented. Broadband and frequency-selective modes of the Josephson detector were used to extend a spectral bandwidth from 1 GHz to 500 GHz. A characterization of a liquid identifier was demonstrated for alcohols, acetone and water.
The electromagnetic response properties of PMMA based composites containing multiwalled carbon nanotubes (MWNT) produced using different time of ultrasonic treatment are investigated in the terahertz frequency range.
A quasi-optical transmissometer driven by a vector network analyzer is used to investigate the crystallization of n-octadecane under different thermal processing. The observed spectra prove there is no weak intermolecular vibration modes present.
The frequency-dependent conductivity of Polyaniline (PAni)-Polyethylene (PE) composites were measured at different mass concentrations using terahertz time-domain spectroscopy. The frequency-dependent behavior followed the Mott-Davis behavior, which showed variations of the fitting parameter S with different mass fractions of PAni. The parameter S revealed a major influence of the insulating part...
We demonstrated THz pulse propagation through hollow core fibers with two or four embedded indium wires. In the frequency range from 0.65 to 1.05 THz, the attenuation coefficient was measured to be 0.3 cm−1 in average for the two-wire and 0.4 cm−1 for the four-wire configuration, respectively. The low dispersion characteristics predicted by numerical simulations agrees well with the experimental measurements...
We present two designs of planar terahertz metamaterials for strain sensing. A series of resonance frequency shifts are obtained with differing gap widths when the sensor is under mechanical compression. The subwavelength metamaterial structures exhibit a high-Q resonance resulting in a good sensitivity to mechanical deformation. Because of the penetrability and relatively high spatial resolution...
Gyrotron FU CW CI is developed as one of sub-THz gyrotrons included in the FU CW series. The advantage of the gyrotron is compactness using a compact superconducting magnet and compact power supply system, which makes the accesses of the gyrotron to applied large-scale devices easier and extends the applications of gyrotron to wider fields. The designed frequency and cavity mode are 394.5 GHz and...
The responsivity of a Golay cell detector for continuous-wave 2.52 THz radiation is measured under the modulation frequency from 2 to 50 Hz. Theoretical analysis of the detector output signal is performed by modeling the detection process as a response to a sequence of rectangular pulses. Calibration of the detector with different input powers is achieved by using a thermopile calorimeter as the reference...
A longitudinal computer-generated hologram is incorporated into the Fabry-Pérot cavity of a terahertz quantum cascade laser which displays two distinct spectral gain peaks. The combined cavity and hologram feedback mechanisms lead to digitally selective dual-mode emission with a difference frequency which may be electronically tuned from 190 GHz to 267 GHz.
We report the first measurement of the frequency independent refractivity of water vapor from 0.1 to 1 THz. The humidity dependent transit time of THz pulses through a 170 m long round trip path was measured to a precision of 0.1 psec, using a mode-locked laser as an optical clock.
We characterize the multiple THz superconducting gaps of Fe-based superconducting films form different families. We discuss with special emphasis the role of the film thickness in affecting the structure of the superconducting gaps.
We report spatially resolved measurements of frequency, phase, and amplitude of GHz and THz emitters employing an unstabilized THz frequency comb. Different detection methods are compared regarding accuracy and invasiveness.
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