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Coherent Different Radiation (CDR) produced by ultrashort electron beam is in THz region and has the characteristics of broadband, high peak power, and tunable frequency. CAEP free electron laser (FEL) beamline provides 54.167MHz electron beam bunches with picosecond longitudinal length, which are suitable to generate high repetition high average power THz CDR. In this paper, the characteristics of...
An application of terahertz metamaterials as transducer elements for chemical sensors is reported. A planar array of split-ring resonators was formed from gold on the surface of silicon wafer and coated by polyaniline. Analyte binding to polyaniline leads to well measurable changes of the resonance frequency.
For many years the Astronomy Instrumentation Group (AIG) of Cardiff University have lead the world in the design and implementation of far infrared and submillimetre (now THz) filters, which can have low-pass, high-pass and band selection (or rejection) properties. These devices rely on the precise stacking of many patterned metallic frequency selective elements into a single bonded multi-layer assembly...
THz devices depend on precise knowledge of material parameters, which, as the frequency coverage of VNA's pushes into the THz region, can be obtained from free space measurements. However the interpretation of the results generally assumes an infinite plane wave propagating through the sample, whereas in practice a Gaussian beam-waist is typically located there. We discuss the error introduced by...
We report on the observation of terahertz radiation induced photocurrents in single-layer graphene samples subjected to an in-plane magnetic field. The photosignal is observed for both, linearly and circularly polarized radiation. A remarkable effect is that the current inverts its sign not only by switching the magnetic field direction, but as well by changing the radiation helicity from left- to...
A novel room-temperature microbolometer for terahertz wave is described in this paper. Each microbolometer in the array consists of a Nb5N6 thin film microbridge and a dipole planar antenna. Such antenna-coupled microbolometer behaves very well for detecting signals from 0.2 THz to 0.32 THz, thanks to the fact that the temperature coefficient of resistance of the Nb5N6 thin film is as high as −0.7%...
Possibility of generation of multi-megawatt terahertz pulses based on undulator and Cherenkov mechanisms of superradiance from electron bunches formed by photo injection guns has been studied. Theoretical analysis was performed in the frame of average approach and confirmed by direct PIC simulations.
In this study, the dispersion relation of the waves in the plasma guided by a coaxial dielectric loaded slow wave structure has been derived and solved. Results show that there are two different waves propagating in this structure. The associated physical mechanisms will be presented.
A polarization sensitive millimeter-wave sensor operating at 77 GHz is built and characterized. The sensor is scalable to a distributed aperture architecture and results are presented from using multiple antennas. Imagery is also presented from a 30-element distributed aperture system that is only sensitive to one polarization.
We show an example of a purely magnetic spin resonance in EuTiO3 and the resulting new record high Faraday rotation of 590°/mm at 1.6 T for 1 cm wavelengths probed by a novel technique of magneto-optical GHz time-domain ellipsometry.
We discuss methods of adapting carbon nanotube arrays to various thermal detector platforms. In addition we present measurement results that underscore their merit. Specifically, we present reflectance measurements in the far infrared (30 THz to 0.5 THz) and spectral responsivity of pyroelectric and thermopile detectors.
Long-wave studies of condensed phase matter have been successfully conducted at the Far-IR/THz beamline of Australian Synchrotron for a few years and applications range from nanotechnology, geology, renewable energy sources, forensics, biology, engineering and the environment. In this paper, we will present some of these applications and current techniques, as well as new techniques which are under...
We report on time-resolved photoluminescence of excitons and electron-hole plasma in GaAs quantum wells under intraband excitation by a free-electron laser in resonance with intersubband and intraexcitonic transitions, respectively, to study relaxation and intraexcitonic scattering.
Metal-coated polymers shaped by 3D stereolithography are introduced as a new manufacturing method for passive components for millimeter to terahertz electromagnetic waves. This concept offers increased design capabilities and flexibilities while shortening the manufacturing process of complex shapes. Tests in the W-band are reported.
We present an all-electronic raster-scan imaging system for 220 GHz which is fully based on planar CMOS integrated circuit components. The emitter has been implemented in 90-nm CMOS process and delivers up to 50 µW at 220 GHz. The detector, based on a patch-antenna-coupled field-effect transistor pair has been implemented in a 150-nm CMOS process and exhibits a maximum responsivity of 180 V/W at 213...
This study focuses on the seals of validation, sealing written documents, used in the Western Middle Ages, especially wax seals. We use THz spectroscopy and imaging for non-destructive evaluation of natural materials within those seals. Using a time domain THz spectroscopy and imaging system, THz transmission images are generated in the 0.1–3 THz range and demonstrate that the spectral properties...
A differential transmission line sensor at 100 GHz is designed and analyzed. Artificial transmission lines are used in a coplanar waveguide configuration. Its high sensitivity to dielectric changes in thin layers enables detection of DNA hybridization or antibody-antigene binding processes for biomedical applications. It is simple, cheap and easy to combine with semiconductor mm-Wave sources and detectors.
Transmission spectra of wet human teeth and dentin slices, together with blood of different flow rates were investigated over a wide spectral range, from visible to terahertz (THz) light. The results make it possible to find the optimum light frequency for an all-optical determination of pulpal blood flow and, consequently, for clinically diagnosis of tooth vitality.
In this paper, the analysis of a conventional W-band gyrotron oscillator operating with TE02 mode has been investigated through the particle-in-cell (PIC) simulation. The influence of the variations of the operating parameters (such as beam voltage, beam current, velocity ratio) on the output power and electron efficiency has been studied in detail. The PIC simulation predicts 33.4kW output power...
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