Sellmeier and thermo-optic dispersion formulas for RbTiOPO4

The thermo-optic constants for RbTiOPO₄ were measured from 20.0 to 120.0 °C in the 0.532–1.571 μm range. The Sellmeier and thermo-optic dispersion formulas that reproduce well the temperature-dependent phase-matching conditions for the normal and periodically poled crystals are presented.     

A low-power low-noise accurate linear-in-dB variable-gain amplifierwith 500-MHz bandwidth

A linear-in-dB variable-gain amplifier (VGA) using a pre-distortion circuit to generate the gain-control signal is fabricated in a BiCMOS process with f_T=20 GHz. The VGA comprises two cascaded stages of signal-summing VGA and has a variable-gain range of over 70 dB. It can operate at up to 500 MHz and dissipates 36 mW from a 3-V supply. A noise figure of below 5 dB and IIP3 of over -38 dBm at 43-dB gain were obtained. The VGA achieved a gain error of less than 2 dB over 70-dB gain range, and it occupies approximately 1 mm². The VGA is applicable to future code division multiple access (CDMA) receivers     

Simulations of friction anisotropy on ordered organic monolayer

A method of molecular dynamics is used to investigate friction anisotropy observed on a hexagonally packed organic monolayer of straight-chain molecules, which tilt in a specific direction. A rigid gold slider with a single atomic protuberance is used as a model of a typical atomic force microscope tip apex. The friction anisotropy is observed at 50 K, which is below the melting point of rotation around a long axis of the molecule. The anisotropic frictional behavior is that sliding in directions normal to the direction of the collective tilt of the molecules results in the maximum friction force. The origin of the anisotropy is attributed to anisotropy in lateral compliance in the monolayer.     

Growth of well-aligned carbon nanotubes by RF-DC plasma chemical vapor deposition

Highly aligned carbon nanotubes (CNTs) were grown under high sheath electric field and gas pressure conditions by the radio frequency (RF) plasma-enhanced direct current (DC) plasma chemical vapor deposition (CVD) method due to a stabilized DC discharge. The uniform growth of highly aligned multi-walled CNTs was achieved over the entire surface area of a 50 × 50 mm² iron foil. The growth of multi-walled CNTs on a 75 × 75 mm² iron foil was also confirmed.     

Drastic suppression of the optical reflection of flash-lamp-crystallized poly-Si films with spontaneously formed periodic microstructures

Polycrystalline Si (poly-Si) films formed by flash lamp annealing of precursor a-Si films on glass substrates have periodic surface roughness spontaneously formed through crystallization, which effectively acts to decrease optical reflection. The surface roughness initially decreases, and then reversely increases with increase in the duration of wet etching, performed to modulate the surface morphology and to reduce optical reflectance. This curious phenomenon can be understood as the selective removal of surface projections, which contain a number of voids, and as different etching rates of large-grain and fine-grain regions. The antireflection effect is enhanced not by the variation of the surface roughness, but rather by the removal of the voids near the surface. The etched poly-Si films covered with antireflection films show remarkably low average reflectance of 3% without any complicated texturing processes, which will lead to the fabrication of high-efficiency solar cells by a simple process.     

NOX reduction over paper-structured fiber composites impregnated with Pt/Al2O3 catalyst for exhaust gas purification

Pt/Al₂O₃ catalyst powder was successfully incorporated in a microstructured paper-like matrix composed of a ceramic fiber network, by use of a simple papermaking technique. As-prepared composite, denoted paper-structured catalyst, was applied to the reduction of nitrogen oxide (NO _X ) in the presence of propene, for exhaust gas purification. The paper-structured catalyst demonstrated higher NO _X reduction efficiency and more rapid thermal responsiveness than a conventional Pt-loaded honeycomb catalyst, indicating that the paper-like structure with interconnected pore spaces contributes to effective transport of heat and reactants to the catalyst surfaces. Furthermore, the paper-structured catalyst with the appearance of flexible paperboard has a high degree of utility. The efficiency of utilization of Pt catalyst was improved by using hierarchically assembled paper-structured catalysts with preferential location of Pt catalyst in the upper part. The paper-structured catalyst composite with paper-like utility and porous microstructure is thought to be a promising catalytic material for efficient NO _X gas purification.     

Sum-frequency-generation system for differential absorption lidar measurement of atmospheric nitrogen dioxide

A sum-frequency-generation system for differential absorption lidar measurement of atmospheric nitrogen dioxide in the lower troposphere was developed. The system uses a combination of a pair of KD*P crystals and a tunable dye laser with LDS 765 dye pumped by the second harmonic of a Nd:YAG laser to generate lambdaon and lambdaoff alternatively. Compared with the conventional system that uses Coumarin 445 dye pumped by the third harmonic, the output energy and long-term stability were improved. By use of this system, atmospheric NO2 concentrations of approximately 10-50 ppb were measured, with an instrumental error of approximately 7 ppb.     

Development of a differential-absorption lidar system for measurement of atmospheric atomic mercury by use of the third harmonic of an LDS-dye laser

A differential-absorption lidar system that uses a long-life transmitter for monitoring of atomic-mercury concentrations in the atmosphere has been developed. The third harmonic of a tunable dye laser with LDS 765 dye pumped by the second harmonic of a Nd:YAG laser was used as the emitted beam from the transmitter. By use of this system, atmospheric concentrations of atomic mercury of less than 0.4 part in 10(12) were measured. The time trend of the measured concentration agreed with that obtained by a conventional gold amalgamation method combined with atomic absorption spectroscopy on the ground.