We describe a film of highly-aligned single-walled carbon nanotubes that acts as an excellent terahertz linear polarizer. There is virtually no attenuation (strong absorption) when the polarization perpendicular (parallel) to nanotube axis. From data we calculated reduced dichrosim be 3, corresponding nematic order parameter 1, which demonstrates nearly perfect alignment well intrinsically anisotropic response in film.

We demonstrate a terahertz polarizer built with stacks of aligned single-walled carbon nanotubes (SWCNTs) exhibiting ideal broadband properties: 99.9% degree polarization and extinction ratios 10–3 (or 30 dB) from ∼0.4 to 2.2 THz. Compared structurally tuned fragile wire-grid systems, the performance in these polarizers is driven by inherent anistropic absorption SWCNTs that enables physically robust structure. Supported scalable dry contact-transfer approach, SWCNT-based are for emerging...

Cherenkov phase-matched terahertz (THz) wave generation from a MgO:LiNbO3 ridge waveguide was studied using optical rectification. Pumping achieved 20 and 60 fs laser pulses fiber centered at 1.56 μm. Time-domain spectroscopy (TDS) results showed single-cycle pulse with pumping near-single-cycle pumping. The spectrum covered the range of 0.1-7 THz, signal-to-noise ratio over 50 dB. output power measured by Si bolometer deuterated triglycine sulfate pyroelectric detector is shown compared to...

When combined with a nonlinear waveguide crystal, Cherenkov phase matching allows for highly effective generation of high power and broadband terahertz (THz) waves. Using ridged Lithium Niobate (LiNbO3) coupled specially designed silicon lens, we successfully generated THz waves intensity approximately three orders magnitude stronger than those from conventional photoconductive antenna. The spectrum was 0.1 to 7 maximum dynamic range 80 dB. temporal shape time domain pulse is regular single...

The thermal stability of γ-ray-induced methyl radicals in methane hydrate was studied using the ESR method at atmospheric pressure and 210−260 K. radical decay proceeded with second-order reaction, ethane molecules were generated from dimerization process. proceeds by two different temperature-dependent processes, that is, respective activation energies these processes are 20.0 ± 1.6 kJ/mol for lower temperature region 210−230 K 54.8 5.7 higher 235−260 former agrees well enthalpy change...

Electron spin resonance measurement of gamma-ray-irradiated propane hydrates shows that the normal propyl radical withdraws hydrogen from adjacent molecule through hexagonal planes hydrate cage without water bridging.

We have obtained efficient terahertz (THz)-wave generation from surface-emitting or waveguide propagation using Cherenkov-type radiation with nonlinear optical (NLO) crystals. This approach presented the following advantages: 1) many crystals can be used as THz-wave emitters; 2) it is not necessary to satisfy phase-matching condition inside crystal; and 3) suppressed by absorption in crystal. demonstrated that was enhanced 50× suppressing phase mismatch a surfing configuration for bulk...

We demonstrate a compact, broadband, and high-power terahertz wave-generation scheme via optical rectification of femtosecond pulses in 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) crystal. used fiber laser with high repetition rate an average power few hundred milliwatts to illuminate the DAST The waves emitted from crystal were measured using calibrated pyroelectric sensor. obtained 18 µW, more than two orders magnitude greater by typical photoconductive antenna.

The two stilbazolium derivatives, 4-dimethylamino- N -methyl-4-stilbazolium tosylate (DAST) and p -chlorobenzenesulfonate (DASC), are organic ionic nonlinear optical materials that have a tendency to form bulk crystals when grown in mixed solvent of methanol acetonitrile. We observed the generation broadband high-power terahertz (THz) waves from DASC. DASC superior transmission characteristics THz band than DAST crystals, it is expected generated using will higher power those crystals.

We measured the real and imaginary dielectric constants, ' '', of H2O D2O ice over frequency range 0.2–1.4 THz temperature 20–240 K using terahertz-time domain spectroscopy a gas-cooled cryostat. The constant increased with frequency; numerical calculations indicated local maximum in at few terahertz. polarizability α obtained from exhibited linear increase respect to squared (T2). which is mainly influenced by infrared phonon absorption, entire considered this study. A mathematical model...

This is the first report of single-cycle terahertz (THz)-wave pulse generation with a wide band (over 6 THz) and high dynamic range 70 dB) using an organic nonlinear optical crystal, 4-dimethylamino-N'-methyl-4'-stilbazolium tosylate (DAST), prism-coupled Cherenkov phase-matching method. The approach allowed use DAST crystal as Cherenkov-type emitter for reduced light absorption by resulting in single- half-cycle THz shapes, which were detected dipole bow-tie antennas, respectively. suitable...

We developed a broadband terahertz wave circular polarizer that consists of two-dimensional (2D) array three-dimensional metallic helices. Each helix operates in an axial mode operation where the wavelength resonance is comparable to dimensions helix. evaluated performance using standard time domain spectroscopy, and we confirmed helices transmits circularly polarized with opposite handedness as The covers frequency range from 117 GHz 208 GHz, close one octave. obtained ellipticity unity this band.

The applications of terahertz (THz) waves have been increasing rapidly in various fields, and there is a strong demand for efficient, robust, low-cost optical components working the frequency region. Bamboo, being one naturally occurring renewable resources, it has potential to be used as an easily accessible sustainable material fabrication components. In this article, transmission mode time domain spectroscopy (THz-TDS) investigate properties, such refractive index absorption coefficient...

Synthetic methane hydrate irradiated by γ-rays at 77 K has been measured electron spin resonance (ESR). The quartet signal g=2.0029±0.0005 with the intensity ratio of approximately 1:3:3:1 and hyperfine coupling constant A=2.3±0.1 mT was identified as methyl radical (CH3·). dose response its intensities showed that radicals were formed linearly up to 10 kGy G-value [the formation efficiency pairs per 100 eV (16 aJ)] 0.05. According annealing experiments, became unstable over 200 K, which...

We have investigated terahertz (THz) emission from lithium ternary chalcopyrite crystals LiInSe2, LiGaSe2, LiInS2, and LiGaS2 that were illuminated by 1560 nm femtosecond pump laser pulses. Monocyclic THz caused nonlinear optical effects was initially observed in all the crystals. Narrow-band coherent phonons LiInSe2 (2.87 THz) LiGaSe2 (2.60 3.45 THz). These phonon modes most likely impulsive stimulated Raman scattering.

For the nondestructive inspection of gas hydrates, terahertz (THz) time-domain spectroscopy (TDS) was applied to tetrahydrofuran (THF) hydrate and propane hydrate. The absorption monotonically increases with frequency, similar case ice, while THF has a characteristic broad peak at 0.5 THz corresponding dipole moment molecules. refractive indices hydrates are 1.725 1.775 1 THz, respectively, show slight but clear difference from index ice (1.79). THz-TDS is potentially useful technique for hydrates.

Electron spin resonance (ESR) spectra of butyl radicals induced with γ-ray irradiation in the simple isobutane (2-methylpropane) hydrate (prepared deuterated water) were investigated. Isothermal annealing results γ-ray-irradiated reveal that isobutyl radical a large cage withdraws hydrogen atom from molecule through shared hexagonal-faces adjacent cages. During this “hydrogen picking” process, is apparently transformed into tert-butyl radical, while sum and remains constant. The apparent...

Twisted nematic type THz polarization control devices using liquid crystal immersed membrane films were fabricated by simple stacking process. First of all, we verify the alignment effect in various kinds films. From Time-Domain Spectroscopy measurements, apparent refractive index anisotropy was observed Polytetrafluoroethylene and Polyolefin Furthermore, transmission properties twisted device are rough agreement with 4 × matrix calculation data. We believe that primary characteristic TN can...

Terahertz time-domain spectroscopy (THz-TDS) employs a mechanical stage to introduce the time delay between pump and probe optical pulses during sampling process of electric field terahertz pulse. The positioning error limited resolution cause an inaccurate In this study, we numerically experimentally investigated influence on major characteristics THz-TDS, such as bandwidth dynamic range system, along with signal-to-noise ratio (SNR) intensity spectra. We demonstrate that in not only...

Electron spin resonance (ESR) studies have been performed to investigate radicals induced in ethane hydrate irradiated by γ-rays at 77 K. Two ESR spectra are observed and identified as the ethyl radical (g=2.0031±0.0005, Aα⊥=2.2±0.1 mT, Aα|| =2.5±0.1 Aβ=2.7±0.1 mT) atomic hydrogen (g=2.0026±0.0005, A=50.5±0.1 mT). From results of analysis gas mass spectroscopy, it is concluded that decays into butane dimerization first-order reaction temperature region 250–265 The activation energy decay...