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This paper shows simulated and measured results of ultra-low cost metal mesh filters on electrically thick substrates for millimeter-wave and THz bands. It provides a broad overview of metal mesh filters currently available and suggest why it is worth moving to an electrically thick substrate for ultra-low cost applications. We demonstrate scalable traditional metal mesh filters on 525 µm thick fused...
To improve the coupling efficiency of Quantum Well Infrared Photo-detector (QWIP), a new grating was proposed. By optimizing the grating, it can work in 3∼5µm and realize an enhanced peak at 4.5µm. With the uniform result of simulation and experiment, an optimizing metallic grating was designed.
First reported by our research group in 2007, AlN tunnel barriers grown by ICP nitridation of thin Al overlayers offer a promising alternative to Al oxide barriers for high current density SIS junctions used in quantum limited THz heterodyne receivers [1]. However, the growth rate of AlN is heavily dependent on ICP operating conditions and as new uncharacterized nitridation processes are investigated,...
Intense terahertz pulses are used to investigate nonlinear carrier dynamics in Au thin films with different morphologies. From THz field-dependent transmission measurements, we found that the conductivity in percolated Au nanostructures increases with increasing the incident field strength. The measured complex dielectric dispersion was analyzed using the Drude-Smith model to discuss the dynamics...
Topological insulators represent a new state of matter where bulk insulators exhibit metallic surfaces that are protected by time reversal symmetry. However, in common transport measurements residual bulk conductivity hinders the properties of the topologically protected surfaces. Alternatively, terahertz spectroscopy has recently been shown to be capable of discerning the bulk and surface carrier...
Terahertz ellipsometric and polarimetric measurement systems have been commissioned with the Novosibirsk free electron laser (FEL) being a source of monochromatic radiation. Calibration experiments with semiconductors and metamaterials showed correct operation of these systems. Blood films, monosaccharide, amino acids, and culture medium were studied.
We overview the technology of superconducting Hot-Electron Bolometer mixers in the field of terahertz heterodyne detection. HEB mixer performance is analyzed vs competing technologies and application fields, with emphasize on radio astronomy. We discuss materials which have been reported in the past to be used for such devices with both phonon-substrate and electron-diffusion cooling mechanisms. It...
We have reported on terahertz magnonics, which is a signal transmission with high-energy spin waves (electromagnons) excited by THz wave. As source and medium for electromagnons, we choose Sm3Fe5O12 ultrathin films whose magnetic properties are modified by applying an epitaxial strain. Electromagnons are successfully detected in the strained Sm3Fe5O12 ultrathin film, using a transmittance THz time-domain...
This paper describes non-uniformity reduction in terahertz (THz) imaging system, using a coherent THz source and a THz camera. The beam wobbling technique reduces the interference pattern, but illumination distribution often remains. In order to reduce the illumination distribution, post-image process is applied. In this method, the raw image is divided by the reference image without the sample, which...
We report the tunable conductivity of single walled carbon nanotubes and multi-walled carbon nanotubes with their surface walls decorated by Gold nanoparticles in the elusive THz frequency range (0.3–2.0 THz). Colloidal gold nanoparticles were synthesized by the reduction of gold chloride solution using tri-sodium citrate. A simple chemical route is followed to attach Au NP on the surfaces of carbon...
Measurement accuracy of material parameters is highly influenced by the difficulty in distinguishing terahertz (THz) signals from many unwanted signals. We introduce a novel method to effectively extract and separate THz signals from such effects. The proposed algorithm is assessed in terms of extraction efficiency, model validity and material parameter calculation accuracy, demonstrating significant...
We have measured the spectral response of sensitive Transition Edge Sensors (NEP ∼ 10−18 W/√Hz) in the frequency range from 1 to 10 THz. The TES sensors have been developed for the SAFARI instrument on SPICA and operate at 70 mK. The sensor is placed in a horn-coupled integrating cavity. We have developed a system with a light pipe that couples radiation from a room temperature Fourier Transform Spectrometer...
We present a design of periodically arranged microslits in a gold film for nonlinear terahertz phonon spectroscopy. Global optimization of array parameters gives a field enhancement of more than 50, due to plasmonic coupling between individual slits.
We discuss properties of the frequency selective THz components and plasmonic structures produced by direct laser patterning of various metals. Research was focused on finding the optimal parameters for fast fabrication procedure maintaining shape, width, and depth of the specified apertures.
Dielectric films with a thickness much less than a wavelength pose a challenge in transmission-mode terahertz time-domain spectroscopy (THz-TDS). A small signal change induced by such films is likely to be obscured by system uncertainties. In this abstract, several possible thin-film measurement procedures are carefully considered. It is found that an alternating sample and reference measurement approach...
We demonstrated broadband terahertz (THz) wave emission from thin metal (gold) films excited by two-color laser fields synthesized by an in-line phase compensator. By driving the electrons in thin metal films asymmetrically, THz wave emission is observed at normal incidence of the two-color pump beams in a transmission geometry. Similar to the air-plasma THz source excited by two-color laser fields,...
We report on the observation of the significant photocurrent response of a carbon nanotube (CNT) heterostructure device illuminated by continuous-wave terahertz (THz) radiation. The device consists of a double-walled CNT macrobundle contacted with two metallic nickel electrodes. A room-temperature current responsivity up to ∼0.3 mA/W was obtained when THz radiation was incident on the position of...
We report on a non-contact, non-destructive evaluation system which utilizes frequency-domain THz transmission spectroscopy to examine the temperature and magnetic field-dependent conductivity of thin film on substrate materials.
Terahertz (THz) neutral density (ND) filters are a useful components in THz system, and have recently attracted s much interest. In this paper we report on the potential of d PEDOT/PSS conductive polymer thin film doped with a polar i organic compound dimethylformamide (DMF) as a THz ND filter. The THz transmission through the thin film is controlled by the DMF doping concentration.
Coherent-source THz spectroscopy was employed to measure the charge carrier dynamics and excitations of ultrathin superconducting films at low temperatures. While the properties of weakly disordered superconductors can be well described by the BCS theory, significant deviations are observed as disorder increases towards the superconductor-insulator transition. A comparative study including tunneling...
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