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ABSTRACT: We developed a Cherenkov phase-matching method for monochromatic THz-wave generation using the DFG, process with a lithium
niobate crystal, which resulted in both high conversion efficiency and wide tunability. Although THz-wave generation by Cherenkov
phase matching has been demonstrated using femtosecond pumping pulses, producing very high peak power, these THz-wave sources
are not monochromatic. Our method generates monochromatic and tunable THz, waves using a nanosecond pulsed laser source. We
also show that Cherenkov radiation with waveguide structure is an effective strategy for achieving extremely wide tunable
THz-wave source. We fabricated MgO-doped lithium niobate slab waveguide and demonstrated difference frequency generation of
THz-wave generation with Cherenkov phase matching. Extremely frequency-widened THz-wave generation, from 0.1 to 7 THz was
observed.
Optics and Spectroscopy 04/2012; 108(6):841-845. · 0.61 Impact Factor
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ABSTRACT: The aim of this study was to apply terahertz technology for screening and identification of drugs-of-abuse in mail. We have introduced terahertz spectral imaging and diffuse reflectance spectroscopy using our tunable THz parametric sources.
Lasers and Electro-Optics (CLEO), 2011 Conference on; 06/2011
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ABSTRACT: We have developed a three-dimensional spectroscopic imaging system that uses terahertz waves and is based on transmission computed tomography. Using this system, we demonstrate transmission three-dimensional computed tomography imaging of high refractive index objects, with identification of chemical components, by analyzing spectroscopic information.
Infrared Millimeter and Terahertz Waves (IRMMW-THz), 2010 35th International Conference on; 10/2010
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ABSTRACT: We demonstrate an imaging method combined a terahertz time-domain spectroscopy and an interference effect for label-free protein detection on a membrane filter. Biotin is linked to the membrane using poly ethylene glycol (PEG) or poly ethylene glycol methyl ether (MPEG) to prevent it from being washed off. Binding of the biotin with streptavidin is then observed by measuring the terahertz signal change due to the variation of the membrane refractive index. From result of competition binding experiments, it becomes clear that specific binding of antibody protein are detected by using this imaging method. This technique is used only to detect the existence of the binding. And the selectivity depends absolutely on specific ligand-protein interactions. This measurement principle is suitable to high throughput detection for drug discovery.
Infrared, Millimeter, and Terahertz Waves, 2009. IRMMW-THz 2009. 34th International Conference on; 10/2009
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Applied Physics Express 01/2009; 2:022301. · 3.01 Impact Factor
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ABSTRACT: We report on a sensing method in the terahertz range using metallic mesh (MM). Conventionally, the filter property of an MM can be changed by the geometrical parameters of the MM. Considering that this property is also changed when the medium in the vicinity of the mesh openings has a different permittivity, we were able to measure small amounts of absorbing materials and thin plastic films on the metallic mesh. We observed change of both the transmission characteristics and the images.
Infrared and Millimeter Waves, 2007 and the 2007 15th International Conference on Terahertz Electronics. IRMMW-THz. Joint 32nd International Conference on; 10/2007
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ABSTRACT: In this paper, we demonstrate a non-destructive detection for the soot which adheres to a soot collection filter by using millimeter waves. We constructed a system that measures the millimeter-wave transmittance, which can be an indicator of the soot density.
Infrared and Millimeter Waves, 2007 and the 2007 15th International Conference on Terahertz Electronics. IRMMW-THz. Joint 32nd International Conference on; 10/2007
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ABSTRACT: We had proposed and developed a THz-wave apparatus for the nondestructive detection of illicit drugs and hazardous substances hidden in sealed envelopes. In actual inspection, we have proposed the following procedure: First, X- ray pre-inspection is carried out; second, the measurement of scattered THz waves is applied to pick up suspicious mails; and, third, the identification of the drugs is done by spectral fingerprinting. In this paper, our recent developments of this application and the prototype apparatus for the inspection will be presented.
Infrared and Millimeter Waves, 2007 and the 2007 15th International Conference on Terahertz Electronics. IRMMW-THz. Joint 32nd International Conference on; 10/2007
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ABSTRACT: A series of experiments in the field of THz-wave spectroscopy is described. The measurement of absorption spectra of solid samples, powders, and liquids is demonstrated using various optical setups. One of the sources we used is a widely tunable coherent THz-wave generator relying on an optical parametric process: nanosecond Q-switched Nd : YAG laser light scattering from the polariton mode of a MgO-doped LiNbO<sub>3</sub> crystal. For the measurement of the absorption of THz waves in liquids, a train of waves is allowed to oscillate inside a silicon prism. A liquid placed on a total internal reflection surface lowers the quality factor of the resonator, which allows determining the complex refraction index of the sample by frequency scanning. We have also developed a technique for THz chemical imaging, by introducing the component spatial pattern analysis. The spatial distribution of the chemicals, such as illicit drugs concealed in an envelope, is obtained from terahertz multispectral transillumination images and absorption spectra. To compensate for the low imaging speed, a prescreening step is proposed, by first detecting the presence of powders in the envelopes, which is achieved by measuring in real time the amount of scattering produced by the envelopes. Details and examples are provided.
Proceedings of the IEEE 09/2007; · 6.81 Impact Factor
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ABSTRACT: We have developed compact THz-wave parametric generators with different characteristics that operate at room temperature. One generates high energy and broadband THz waves, being suitable for detecting the transmission of absorptive or diffusive samples, and the other has a potential of wide tunability and narrow linewidth, useful for spectroscopic measurements. Also, we are studying several novel steps toward real-life applications of terahertz waves, such as, noninvasive detection of concealed drugs, observation of MOSFET chips using an laser THz emission microscope, printable terahertz sensors using metal mesh. In this paper, we introduce some of our recent activities.
Microwave Symposium, 2007. IEEE/MTT-S International; 07/2007
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T Taino,
H Ishii,
S Yoshimura,
C Otani,
S Ariyoshi,
H Myoren, K Kawase,
T Shibuya,
H Sato,
H M Shimizu,
S Takada,
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ABSTRACT: We have been developing terahertz (THz) wave detectors using superconducting tunnel junctions (STJs). The STJs consist of the Nb/Al/AlO x /Al/Nb structure. We fabricated THz-wave detectors on LiNbO 3 substrates, that have a high absorption coefficient for the frequency range of 10 12 Hz. Two kinds of signals were detected when the THz-wave was irradiated from the substrate side. One was an indirect signal related to the generation of phonons. The other was a signal that corresponds to directly generated quasi-particles in the Nb electrode of the STJ. The pulse height of the indirect signal was larger than that of the latter signal. To enlarge the detector area, we designed a STJ that has different areas of the base electrode and top electrode. In this paper, the characteristics of the THz-wave detector area will be discussed.
04/2007; 25.
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ABSTRACT: We demonstrated terahertz imaging using a linear array detector with five elements based on superconducting tunnel junctions (STJs). Nondestructive imaging at 0.66 THz was successfully performed for a test metallic pattern and an integrated-circuit card using the STJ linear array, which shortened the total acquisition time.
Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics, 2006. IRMMW-THz 2006. Joint 31st International Conference on; 10/2006
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ABSTRACT: We had proposed and developed a THz-wave apparatus for the nondestructive detection of illicit drugs and hazardous substances hidden in sealed envelopes. A fast process of selecting suspicious envelopes is realized by monitoring the THz waves scattered from the target. In this paper, our recent developments of this application and the prototype apparatus for the inspection will be presented.
Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics, 2006. IRMMW-THz 2006. Joint 31st International Conference on; 10/2006
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ABSTRACT: The absence of practical technology to detect illicit drugs or hazardous substances hidden in sealed envelopes by nondestructive methods has made it extremely difficult to prevent them from being smuggled domestically and across international borders. We are developing a prototype apparatus that can identify these substances concealed inside sealed mail without opening it, by taking advantage of the ability of terahertz waves. We will present and discuss a current status of the development, the system configuration, the performance and the limitation of the prototype.
Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics, 2006. IRMMW-THz 2006. Joint 31st International Conference on; 10/2006
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ABSTRACT: The components of amphetamine-type stimulant (ATS) tablets were analyzed, and their influence on the terahertz spectra was evaluated. The results suggested the possibility of identifying the components of ATS in tablets by direct terahertz spectroscopy coupled with spectral data processing.
Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics, 2006. IRMMW-THz 2006. Joint 31st International Conference on; 10/2006
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ABSTRACT: We report on a novel sensing method in the terahertz (THz) range using thin metallic mesh (TMM). Conventionally, the filter property of a TMM can be changed by the geometrical parameters of the TMM. Considering that it is also change when the medium in the vicinity of the mesh openings has a different refractive index, we inspected this principle. For the biomaterial measurements, we deposited the avidin solution uniformly on the TMM. We observed the change of the transmission characteristics.
Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics, 2006. IRMMW-THz 2006. Joint 31st International Conference on; 10/2006
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ABSTRACT: We developed injection-seeded terahertz wave parametric generator pumped by microlaser. Microlaser is the half palm-sized, LD-pumped single-mode microchip Nd:YAG laser, delivers 1.1 MW peak power pulses (530 muJ/pulse) with 430 ps pulse width at 100 Hz repetition rate. This THz-wave source generated narrow-linewidth THz-wave by injection seeding for the idler-wave. We observed its peak output power of more than 20 mW (2 pJ/pulse) at 1.6 THz and its palm size, portable source offer good advantages for many applications.
Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics, 2006. IRMMW-THz 2006. Joint 31st International Conference on; 10/2006
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ABSTRACT: We demonstrated terahertz imaging using a direct detector based on niobium superconducting tunnel junctions (STJs). The detector is composed of linearly distributed junctions placed on a superconducting microstrip line and is integrated on two wings of a log-periodic antenna. We succeeded nondestructive imaging for an integrated-circuit card and dry material using the detector around its sensitivity peak ( ∼ 0.66 THz). The dynamic range was measured to be higher than 4×107 (76 dB). Thus, the STJ detector is applicable to high-sensitivity and high-speed terahertz imaging for various nondestructive inspection applications.
Applied Physics Letters 05/2006; 88(20):203503-203503-3. · 3.84 Impact Factor
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ABSTRACT: A surface-wave sensor based on the resonant transmission characteristics of metal hole arrays is demonstrated in the terahertz (THz) region. Since the frequency of the transmission peak of a metal hole array, which corresponds to the resonant frequency of the surface waves, is particularly sensitive to the refractive index in the vicinity of the metal surface, a very small change in the substances attached to the surface can be detected by monitoring the transmission spectrum. By attaching a layer of substance (thickness t < 5 microm) much thinner than the wavelength of the THz wave (lambda(THz) = 1 mm at 0.3 THz) to the surface of a metal hole array, we demonstrated that the existence of such a small amount of substance can be detected more easily than without the metal hole array. This demonstration of THz sensing with metal hole arrays indicates the possibility of realizing THz surface-wave sensors for biochemical molecules in the THz region.
Optics Letters 05/2006; 31(8):1118-20. · 3.40 Impact Factor
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ABSTRACT: We demonstrated some imaging applications of THz radiations, such as non-destructive detection of illicit drugs in a envelope. We also demonstrated a high sensitive terahertz sensing application by using a resonant transmission phenomenon of metal hole array which is attributed to a excitation of surface waves.
Lasers and Electro-Optics Society, 2005. LEOS 2005. The 18th Annual Meeting of the IEEE; 11/2005
