Terahertz (THz) wave generation based on nonlinear frequency conversion is promising way for realizing a tunable monochromatic bright THz-wave source. Such development of efficient and wide source depends discovery novel brilliant crystal. Important factors crystal are, 1. High nonlinearity 2. Good transparency at THz region. Unfortunately, many crystals have strong absorption The fact limits generation. Here, we show that Cherenkov radiation with waveguide structure an effective strategy...

A series of experiments in the field THz-wave spectroscopy is described. The measurement absorption spectra solid samples, powders, and liquids demonstrated using various optical setups. One sources we used a widely tunable coherent generator relying on an parametric process: nanosecond Q-switched Nd : YAG laser light scattering from polariton mode MgO-doped LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> crystal. For THz waves...

We demonstrated a Cherenkov phase-matching method for monochromatic THz-wave generation using the difference frequency process with lithium niobate crystal, which resulted in high conversion efficiency and wide tunability. successfully generated THz waves across range 0.2-3.0 THz. obtained efficient energy low region below 0.5 THz, achieved flat tuning spectrum by varying pumping wavelength during tuning.

We have enhanced the tunability of a terahertz-wave parametric generator using MgO:LiNbO3 pumped by subnanosecond, passively Q-switched, microchip Nd:YAG laser. This pump source allows high-intensity pumping without damage to nonlinear crystal and generates narrow linewidth tunable terahertz wave with injection seeding an external cavity diode laser for idler wave. The causes gain curve broadening generation, especially in high-frequency region. obtained output tuning range 0.9-3 THz...

Terahertz (THz) wave generation based on nonlinear frequency conversion is a promising method for realizing tunable monochromatic high-power THz-wave source. Unfortunately, many crystals have strong absorption in the THz region. This limits efficient and widely generation. The Cherenkov phase-matching one of most techniques overcoming these problems. Here, we propose prism-coupled (PCC-PM) method, which prism with suitable refractive index at frequencies coupled to crystal. has following...

We demonstrated a Cherenkov-type phase-matching method for monochromatic THz-wave generation using the difference frequency process with lithium niobate crystal. In process, when bulk crystal is used, beam diameter of pump waves causes phase mismatching generating THz-wave. decreased phase-mismatch by optimizing shape cylindrical lenses, and ensured high conversion efficiency especially in high-frequency region. successfully generated THz across 0.2- to 4.0-THz range simple configuration.

We report an extremely widely tuneable monochromatic Cherenkov phase-matched terahertz (THz) wave generator using a bulk lithium niobate crystal. This was achieved by optimizing the incident conditions of pump beams, and surface-emitting condition produced total internal reflection beam at THz output surface nonlinear optical Effective generation higher frequencies realized reducing absorption inside crystal, as result, we tuning range from 0.2 to 6.5 with very simple configuration.

We demonstrated a Cherenkov phase matched THz-wave generation with surfing configuration for bulk lithium niobate crystal. output was enhanced about 50 times by suppressing mismatching propagation direction. The suppression achieved combining two pumping waves dual wavelength finite angle, and THz-frequency controllable changing the angle within 2.5 degrees range. Higher frequency at around 4.0 THz successfully obtained method.

The aim of this study was to apply terahertz (THz) technology security applications, and in particular, for screening identification drugs-of-abuse mail. Comparison made transmission spectra obtained with both THz time-domain spectroscopy a tunable source, the effects sample configuration on resulting were examined. utility diffuse reflectance using source also A non-invasive mail inspection system targeting explosives built, exploiting ability frequency waves penetrate packaging materials...

We have proposed and been developing a new broad-band terahertz (THz) radiation detector using Nb-based superconducting tunnel junction (STJ). The STJ's were fabricated on LiNbO/sub 3/ LiTaO/sub mono-crystal substrates. radiated monochromatic THz pulses in the range 1-2 with pulse repetition rate of 49 Hz, successfully detected corresponding periodic signals via charge-sensitive preamplifier. current signal obtained by derivative output gave time response about 15-20 microseconds. frequency...

We successfully demonstrated pulsed high-peak-power millimeter wave generation using periodically poled lithium niobate (PPLN) under collinear phase matching. fabricated 0.5-mm-thick PPLN with a 40 mm interaction length for generating 250 and 300 GHz waves. Pump waves very close dual wavelength output from KTiOPO4 (KTP) optical parametric oscillator had pulse energy of 2 mJ, duration 15 ns, around 1300 nm. Millimeter were generated successfully, the highest peak power obtained was estimated...

We demonstrated that annealing 4-dimethylamino- N -methyl-4-stilbazoliumtosylate (DAST) crystals near their melting point improves tolerance to laser-induced damage. Their laser-induced-damage characteristics were evaluated and confirmed using difference-frequency THz generation. The DAST employed in this study all approximately the same size. wave output did not decrease about 80% annealed. Microscopy images revealed crystallinity orientation of crystal improved by annealing. Moreover,...

We succeeded in generating terahertz waves using difference-frequency generation (DFG) an organic 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) crystal under intra-cavity conditions. constructed a dual wavelength output optical parametric oscillator (OPO) with two potassium titanium oxide phosphate (KTP) crystals for the DFG pumping source, and placed DAST inside OPO cavity to act as nonlinear conversion element. Our experimental measurements confirmed that was possible level...

Terahertz (THz) beam steering is demonstrated based on the phased-array antenna principle without using actual phase shifters. A periodically-poled lithium niobate crystal pumped with infrared radiation generated from a dual-wavelength optical parametric oscillator. The THz via difference-frequency mixing and emission angle could be varied by tilting one of incident pump beams. This effect equivalent to phase-shifter array for front radiation. technique has advantage high speed, wide angular...

We demonstrated that annealing 4-dimethylamino-N-methyl-4-stilbazoliumtosylate (DAST) crystals near their melting point improves tolerance to laser-induced damage. Their laser-induced-damage characteristics were evaluated and confirmed using difference-frequency THz generation. The DAST employed in this study all approximately the same size. wave output did not decrease about 80% annealed. Microscopy images revealed crystallinity orientation of crystal improved by annealing. Moreover, plane...

We developed a Nd:YAG multi-mode laser-pumped injection-seeded terahertz-wave parametric generator (is-TPG), and compared its terahertz (THz)-wave output energy to that of single-mode is-TPG system. The oscillation threshold the was approximately 73% lower than system, system produced higher THz-wave with same pump energy. required seed power for much laser compact, inexpensive, simpler handle device. This resulted in room-temperature generation could produce sufficient THz spectroscopy.

The aim of this study was to apply terahertz technology for screening and identification drugs-of-abuse in mail. We have introduced spectral imaging diffuse reflectance spectroscopy using our tunable THz parametric sources.

We have suggested a wide range of real-life applications using novel terahertz imaging techniques. A high-resolution tomography was demonstrated by ultra short pulses optical fiber and nonlinear organic crystal. also describe non-destructive inspection system that can monitor the soot distribution in ceramic filter millimeter-to-terahertz wave computed tomography. Further we report on thickness measurement very thin films high-sensitivity metal mesh filter. These techniques are directly...