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We applied laser THz emission spectroscopy to evaluate the adsorption energy of physisorbed O2 molecules on graphene in a surface area confined within the diameter of the excitation laser beam.
We demonstrate a new parallel plate waveguide (PPWG) based terahertz spectroscopy approach to characterize the electromagnetic properties of low conductive two-dimensional materials. We find that the TE mode is suitable for such prototype of materials.
We demonstrate a parallel plate waveguide (PPWG) based terahertz spectroscopy approach to characterize the electromagnetic properties of two-dimensional (2D) materials. The amount of absorption exponentially increases with the waveguide length, therefore, the minimum detectable conductivity of this method sensitively increases by simply increasing the length of the waveguide along which the THz wave...
Development of techniques for characterization of extremely thin films is an important challenge in terahertz (THz) science and applications. Spectroscopic measurements of materials on the nanometer scale or of atomic layer thickness (2D materials) require a sufficient terahertz wave–matter interaction length, which is challenging to achieve in conventional transmission geometry. Waveguide-based THz...
We developed a dynamic terahertz emission microscope to investigate dynamic response of photoexcited carriers in various kinds of solar cell, e.g. a monocrystalline silicon solar cell, a polycrystalline silicon solar cell, and a GaAs solar sell. We could clearly observe the effects of carrier lifetimes of the different kinds of the solar cells. The image reflected the distribution of screening effect...
We observed THz radiation from the graphene-coated InP (100) surface and found the drastic change of the waveforms of THz radiation with time, which cannot be explained by the simple absorption of graphene.
Stilbazolium derivatives DAST and DASC are organic ionic nonlinear optical materials to efficiently generate terahertz waves. We succeeded in obtaining bulk crystals by using an acetonitrile-added methanol solvent and investigated the properties of THz-wave generation.
We examined various types of solar cells using laser terahertz emission microscope. As a result, we could observe the differences among various solar cells, e.g. grain size, material.
Terahertz (THz) near-field detection of liquid was demonstrated by using a scanning laser THz imaging system. The obtained data indicate sample specific peaks and the technique has a potential for evaluating small amounts of liquid.
We applied a pump-probe laser terahertz emission microscope to investigate dynamic response of photoexited carriers in a solar cell. We could clearly observe the change of terahertz radiation at the grain boundary in the polycrystalline silicon solar cell using the pump-probe methods, which could not be obtained by simple terahertz emission imaging.
We have succeeded in detecting the terahertz waves generated from the solar cell under the irradiation of femtosecond laser pulses. This technique has enabled to visualize instantaneous power generation in the solar cell.
We examined a new type of organic nonlinear optical crystal, 4-dimethylamino-N-methyl-4-stilbazolium p-chlorobenzenesulfonate (DASC) as terahertz (THz) wave source via difference frequency generation (DFG), by comparing the THz-wave radiation from DAST crystal. We demonstrated the possibility that DASC crystal has some advantages as THz-DFG source in efficiency and damage threshold.
We investigated the Cherenkov phase-matched tunable THz-wave radiation via difference frequency generation from a lithium niobate crystal (LN) excited by a dual wavelength Cr:Forsterite laser by using the two types of detectors, Si bolometer and Shottkey barrier diode (SBD). We demonstrated that Si bolometer can be useful in the frequency range of 0.2 to 2.3THz and SBD can be useful in the frequency...
We evaluatetd a GaAs<110> substrate as a two-dimensional (2D) terahertz (THz) emitter by using a recent-fabricated scanning laser terahertz imaging system. As a result, we could observe a certain THz radiation available to a 2D THz emitter plate.
We have developed a scanning laser terahertz imaging system with 1.56 μm femtosecond fiber laser for high-speed and high resolution measurement. Using this system, we succeeded in obtaining high-resolution THz images of various samples. An imaging speed of about 47 seconds/image for 512 × 512 pixels and a spatial resolution of up to 56 μm were achieved.
We propose a non-destructive method to measure a depth of Through-Silicon Via (TSV) using Terahertz Time-Domain Spectroscopy (THz-TDS). TSV with high aspect ratio could be measured from the phase-shift of transmitted THz pulse. We also succeeded in imaging the difference between two areas corresponding to TSVs and unprocessed Si wafer.
Metamaterial active in the terahertz (THz) frequency region is very attractive due to its potential for building unique optical components, such as superlenses, using relative simple fabrication technique. The meta-atom, an elementary unit of the metamaterial, is an electromagnetic resonator with non-zero magnetic and/or electric dipole interacting with free space electromagnetic wave. All present...
Visualization of the dynamics of the electromagnetic resonators used to build metamaterial is presented. Observed data provides detailed information on the interaction between free space radiation and the resonator.
We have investigated the terahertz (THz) emission from lithium ternary chalcopyrite crystals illuminated by 1560-nm femtosecond pump laser pulses. Monocyclic THz emission and narrowband THz emission from the coherent phonons in LiInSe2 and LiGaSe2 were observed at 2.87 and 3.45 THz, respectively.
A characteristic absorption and the dielectric constants of gas hydrates are determined by terahertz (THz) time domain spectroscopy. THz spectroscopy is a potentially useful technique to study gas hydrates for both fundamental and application.
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