Infrared sience and technology has been contributing to the four important national priority researches which are nano-, bio-, information- and environmental technologies. In this manuscript we discuss the current status of the infrared science and technology as well as its crucial role in the four technologies.

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We have designed and prepared the multilayer anti-reflection (AR) and diamond-like carbon (DLC) hard coatings for a large scale polycrystal gallium arsenide (Poly-GaAs) infrared optical window to improve its transmittance and surface hardness. The coatings were deposited on 100 mm diameter Poly-GaAs substrates and their optical properties were analyzed. The optimum optical designs are found to be IRX/Ge/YF₃ with buffer layer Y₂O₃ for AR coating, and DLC/Ge/Y₂O₃ and DLC/BP for DLC hard coating, respectively. Their transmittances are 98% for AR coating and 85-87% for DLC coating, which are 5-10% higher than the values for the conventional infrared protective ZnS windows used for airborne infrared thermal imaging systems.

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Chemical actinometer for UV laser nanoprocessing has been developed using infrared spectroscopy for the photoproduct of UV irradiated acetylacetone. Sample was hexafluoroacetylacetone, HFA, in which the H atoms of two methyl groups of acetylacetone are replaced by F atoms. It was irradiated by a KrF excimer laser with the oscillation wavelength of 248 nm during 100 seconds and the photoproducts were analyzed by transmittance measurement of FT-IR in the spectral region between 3500 cm^-1 and 1300 cm^-1. One of the photoproducts was CO and its formation efficiency was estimated to be approximately 0.6. The photodissociation reaction of HFA is expected to be useful for the actinometer by IR spectroscopy of the photoproduct.

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The performance and design highlights of a multi-gigabit free-space optical communication system with fast and accurate beacon tracking are described. In order to achieve high data-rate as well as eye-safety, transmitting laser beam at a 1552 nm wavelength is collimated to be near diffraction limited and the beacon tracker, operated at a 980 nm wavelength with a Si quadrant photodetector, a miniature fast steering mirror and a wideband proportional-integral-derivative (PID) servo controller, is used to detect the receiving beacon direction and to point the transmitting laser beam to the opposite terminal. A preliminary result of a 10-Gbps bidirectional transmission experiment over 1-km distance at Waseda University and the corresponding link analysis are also presented.

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A reflection-type terahertz (THz) time-domain spectroscopy (TDS) is applied to non-contact and non-destructive diagnosis of the surface and inner-structure of test samples. Raster scan imaging and THz optical coherence tomography (THz-OCT) are demonstrated for a bank bill, a high voltage cable and an indented impression on a memo-pad paper. The watermark of the bank bill, the indented impression, and a flaw in the cable are detected successfully. These results indicate that THz imaging is potentially useful for the analysis of surfaces and inner-structures of products made with various materials.

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For practical use of image reconstruction in a steady-state diffusion optical tomography, a weight function is analytically derived in a linear perturbation approach. We show that the weight function at any voxel in the medium is given by a product of a sensitivity function at the voxel and a mean optical pathlength in the voxel, whose two parameters have independent behavior to each other. By use of Monte Carlo simulation, it is found that the mean path length is easily obtained without stochastic calculation by scattering coefficient in the medium. Weight function derived by the proposed method is in good agreement with exact solution based on Monte Carlo method.

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An experimental apparatus for near-infrared absorption imaging by ultrasonic velocity shift using the 20 MHz ultrasonic transducer was fabricated for basic experiments of tissue characterization. The ultrasonic echo pulse shifts by thermal agitation by light was measured in the scattering medium as the ultrasonic transducer with 0.4mm beam width was translated above the sample. The optical information at the specified depth from the surface of the model tissue sample was obtained by our method.

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We have developed chip scale vacuum packaging for an uncooled IRFPA and successfully obtained excellent IR images less than 60 mK in NETD. This package consists of a device chip and a silicon lid. A 160×120 SOI diode uncooled IRFPA with a 25 μm pixel pitch is used as the device chip in this study. The size of the package is 14.5 (L)×13.5 (W)×1.2 (H) mm. The gap between the device chip and the lid is controlled by the thickness of the vacuum sealing material (solder), which is mounted by our original molten solder ejection method. Patterned thin-film getter is formed on the lid wafer. Due to the use of patterned thin-film getter, there is no need to form a cavity on the lid to allow installation of getter or to insert a spacer between the device chip and the lid. The measured pressure of the package is less than 0.5 Pa, which is sufficient for obtaining high thermal isolation. The package also passed 1000 heat cycle tests from -40 to 125°C. In this technique, only the good dies in a wafer are simultaneously packaged in chip scale. Thus, size and cost reduction of the package has been achieved.

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Atmospheric pressure transient glow discharges in microgap electrodes were generated using high voltage pulse with the nanosecond pulse width ranging from 50 to 300 ns. A short pulse generator using a pulse forming line scheme with a reflected wave absorption circuit was designed and operated. The transient glow discharges developed to arcs when the pulse width was long enough. Their duration decreased with increasing an ambient gas pressure and extended with shorter electrode separation. Utilizing a nozzle-to-sphere electrode system with fast gas flow of helium, a stable atmospheric pressure transient glow discharge was successfully obtained. The injection energy was controlled by changing the applied voltage and the gap length. The peak input power of 25 kW was obtained.

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Fe oxide-coated TiO₂ particles for UV protection cosmetics were produced by means of atmospheric pressure glow discharge using IAA(Iron acethyl acetonato). The particles were also coated by a silica protection layer. To examine the UV catalytic ability of Fe oxide -coated TiO₂, we measured a squalene that contained the powders by GCMS for the gas products after the squalene had been irradiated by a Xe lamp for one hour. Using silica-coated TiO₂ that was coated by Fe oxide, we find almost no signals from any harmful organic oxides in the GC-MS spectra of the UV irradiated squalene. The multi- coated powder shows very fine and flesh like-color with pearl-like glowing.

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A model for atmospheric pressure glow discharge (APGD) plasmas in the nitrogen-oxygen mixtures was constructed. The model is based on electron-neutral, ion-neutral, neutral-neutral gas phase reactions and the one-dimensional fluid equations which consist of particle continuity and Poisson's equations. Optical emission spectroscopy measurements were performed for the APGD plasma at a frequency 100 kHz to evaluate the validity of the model. The emission intensity of the second positive system (SPS) band of nitrogen transition from N₂(C³Π_u) to N₂(B³Π_g) and NO-γ system transition from NO(A²Σ⁺) to ground state were measured as a function of mass fraction of oxygen admixture. The densities of N₂(C³Π_u) and NO(A²Σ⁺) calculated by the model show trends similar to the observed emission intensities of SPS and NO-γ system, respectively.

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