The absence of non-destructive inspection techniques for illicit drugs hidden in mail envelopes has resulted such being smuggled across international borders freely. We have developed a novel basic technology terahertz imaging, which allows detection and identification concealed envelopes, by introducing the component spatial pattern analysis. distributions targets are obtained from multispectral transillumination images, using absorption spectra measured with tunable terahertz-wave source....

The hottest frequency region in terms of research currently lies the 'frequency gap' between microwaves and infrared: terahertz waves. Although new methods for generating radiation have been developed, most sources cannot generate high-brightness beams. Here we demonstrate generation ultrabright waves (brightness ~0.2 GW/sr·cm2, brightness temperature ~1018 K, peak power >50 kW) using parametric wavelength conversion a nonlinear crystal; this is brighter than many specialized such as...

Widely tunable terahertz (THz) wave generation by optical parametric processes based on laser light scattering from the polariton mode of nonlinear crystals is reviewed. Using oscillation LiNbO3 or MgO-doped crystal pumped a nanosecond Q-switched Nd : YAG laser, we have realized widely coherent THz-wave sources in range between 0.7 and 3 THz, with simple configuration. For efficient coupling THz wave, monolithic grating coupler an Si-prism array was used. We report detailed characteristics...

Coherent THz-wave generation is demonstrated utilizing a grating coupler fabricated on the surface of LiNbO3 crystal pumped by Q-switched Nd:YAG laser. Wide tunability, sharp directivity, and high efficiency were achieved.

We present an imaging system designed for use in the terahertz range. As radiation source a backward-wave oscillator was chosen its special features such as high output power, good wave-front quality, stability, and wavelength tunability from 520 to 710 GHz. Detection is achieved with pyroelectric sensor operated at room temperature. The alignment procedure optical elements described, several methods reduce etalon effect that are inherent monochromatic sources discussed. spot size sample...

A label-free biological sensor, which is based on the resonant transmission phenomenon of a thin metallic mesh, proposed in terahertz wave region. By using this we demonstrate highly sensitive detection small amounts protein horseradish peroxidase. For quantitative investigation sensitivity our peroxidase was printed mesh surface by commercial available printer. distinct shift dip frequency observed for 500pg∕mm2 (11fmol) indicating significantly high sensor.

High-resolution tomographic imaging is demonstrated using a reflection-type terahertz time-domain spectroscopy. To realize practical system for general use, robust all-fiber laser was used as the pump light source. Broadband waves were generated with combination of optical pulses compressed to 17 fs fibers and DAST crystal. Using deconvolution signal processing, wideband spectrum provided high-axial resolution leading successful multilayered structure containing 2-microm-thin GaAs layer. our...

In 2003, we reported the first-ever development of a spectral imaging system for illicit drugs detection using terahertz (THz) wave parametric oscillator (TPO) [K. Kawase et al., Opt. Exp. 11(20), 2549 2003]. The has dynamic range below four orders magnitude, which enables it to identify reagents only through thin envelopes imaging. Recently, succeeded in developing high power and sensitivity THz injection-seeded generation detection. A excess 80 dB been obtained, is much higher than that...

The injection-seeded terahertz (THz) parametric generator (is-TPG) is one of the most high-power single-longitudinal mode THz-wave sources. Our system less influenced by scattering, refraction, and multiple reflections samples because it a narrow-linewidth source, detection area THz detector large. Thus, suitable for nondestructive inspection practical in real world. In 2003, we reported on development mail that employed oscillator. However, with dynamic range than four orders magnitude,...

Among nonlinear materials, the organic ionic salt crystal 4-dimethylamino- N -methyl-4-stilbazolium-tosylate (DAST) is known for its large nonlinearity. We generated a coherent terahertz (THz) wave, using DAST, from difference frequency between two oscillating wavelengths of an electronically tuned Ti:sapphire laser. In LiNbO(3), LiTaO(3), KTiOPO(4), and GaP crystals, THz-wave generation was not observed under same experimental conditions. This result proves high efficiency DAST crystals...

A laser terahertz-emission microscope (LTEM) system is proposed and developed for inspecting electrical faults in integrated circuits (IC). We test a commercial operational amplifier while the operating. Two-dimensional images of IC chip are clearly observed scanned with femtosecond laser. When one interconnection lines cut, damaged has LTEM image different from that normal chips. The results indicate potential tool inspection.

The first known demonstration of tunable terahertz-wave generation by difference-frequency dual signal-wave quasi-phase-matched optical parametric oscillation was performed with periodically poled LiNbO3 (PPLN) a series gratings. An organic ionic salt, 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST), used as nonlinear crystal. A compact source resulted, and changing the temperature PPLN permitted wavelength to be varied from 120 160 µm. could tuned 100 700 µm proper selection combinations

We demonstrate terahertz-wave (THz-wave) surface-emitted difference frequency generation with nanosecond pulse duration. A slant-stripe-type periodically poled lithium niobate (PPLN) crystal was used to realize the quasi-phase-matching in two mutually perpendicular directions of optical and THz-wave propagation. a wavelength near 200 μm generated by mixing radiation dual-signal-wave parametric oscillator based on phase-reversed PPLN crystal.

An injection-seeded nanosecond terahertz (THz) wave parametric generator was demonstrated using nonlinear crystals that were pumped by a single frequency Nd:yttrium–aluminum–garnet laser. Spectrum narrowing to the Fourier transform limit (ν=1.58 THz, Δν<200 MHz) achieved injection seeding idler (near-infrared Stokes). This resulted in THz-wave output power (900 pJ/pulse, >100 mW peak) approximately 300 times higher than of conventional generator, which has no seeder. compact...

Coherent tunable terahertz waves were generated successfully using a terahertz-wave parametric oscillator (TPO) based on laser light scattering from the A/sub 1/-symmetry polariton mode of LiNbO/sub 3/. This method has several advantages, such as continuous and wide tunability (frequency: 0.9-3.1 THz), relatively high peak power (more than few milliwatts), compactness its system (tabletop size). In addition, simply requires fixed-wavelength pump source it is easy to tune. paper deals with...

We demonstrated the separation of component spatial patterns chemical samples in transillumination terahertz (THz) images using known spectral curves. The and data were measured between 1.3 1.8 THz, a widely tunable coherent THz-wave parametric oscillator source. This method could be effective for analyzing concentrations components with various compositions.

We present the redesign and improved performance of laser terahertz emission microscope (LTEM), which is a potential tool for locating electrical failures in integrated circuits. The LTEM produces an image THz waves emitted when circuit irradiated by femtosecond laser; amplitude proportional to local electric field. By redesigning optical setup improving spatial resolution system below 3 microm, we could extend its application examining large-scale integration As example show pattern field...

Until fairly recently, the terahertz range was considered little more than dark gap that separated two halves of electromagnetic spectrum. Now scientists have come to view it as a bridge rife with possibilities for new applications and research.

A surface-wave sensor based on the resonant transmission characteristics of metal hole arrays is demonstrated in terahertz (THz) region. Since frequency peak a array, which corresponds to surface waves, particularly sensitive refractive index vicinity surface, very small change substances attached can be detected by monitoring spectrum. By attaching layer substance (thickness t < 5 microm) much thinner than wavelength THz wave (lambda(THz) = 1 mm at 0.3 THz) we that existence such amount...

Using the high penetrability of terahertz waves and characteristic absorption spectra in this frequency range, we have built a noninvasive mail inspection system targeting drugs explosives. The is composed two stages; first stage, scattering continuous wave used for selecting that contains concealed powder; second spectrum suspicious measured material identified using database. We evaluated performance limits system.

We report on the development of a high-peak-power, single-longitudinal-mode and tunable injection-seeded terahertz-wave parametric generator using MgO:LiNbO3, which operates at room temperature. The high peak power (> 120 W) is enough to allow easy detection by commercial calibrated pyroelectric detectors, spectral resolution (< 10 GHz) Fourier transform limit sub-nanosecond pulse. tunability (1.2-2.8 THz) small footprint size (A3 paper, 29.7 × 42 cm) are suitable for variety applications.

A widely tunable THz wave has been parametrically generated and reported recently by us utilizing a LiNbO3 crystal with monolithic grating coupler under noncollinear phase matching condition. However, the output direction of is strongly dependent on frequency due to nature matching, as well coupler. In this letter, novel method for coupling proposed using low dispersion prism eliminate almost completely beam deflection entire tuning range. The unidirectional radiation was confirmed...