Optical polarisation control utilising an optical heterodyne detection scheme

An optical polarisation control scheme utilising optical heterodyne detection for coherent transmission is proposed and demonstrated at a wavelength of 1.5 ?m. It converts an arbitrary polarisation state to a linear state at a received optical power level of less than ?70 dBm.     

Epitaxial growth of titanium oxide thin films on MgO(100) single-crystal substrates by reactive deposition methods

We synthesized titanium oxide thin films on MgO(100) single-crystal substrates by two reactive deposition methods and compared the structures of the thin films formed by these methods. In one method (pulsed-molecular-beam deposition method), molecular oxygen is supplied to the substrates by using a pulsed-molecular-oxygen beam source and deposition of one unit layer of titanium and subsequent supply of molecular oxygen are repeatedly performed. In the other method (radical beam deposition method), atomic oxygen is irradiated to the substrates by using an atomic oxygen beam generated by the radical beam source and irradiation of the atomic oxygen and deposition of titanium are simultaneously performed. In the case of the pulsed-molecular-beam deposition method, the crystal structure was changed by increasing the number of oxygen pulses supplied from the beam source. We found that the crystal structure of titanium oxide depended on the composition ratio of O:Ti in the film. The maximum ratio of O:Ti attainable by this method was 1.85, and at this ratio, (100)-oriented pseudorutile was formed. In the case of the radical beam deposition method, (100)-oriented anatase was formed below the titanium deposition rate of 0.10 nm/s and pseudorutile (TiO_2−δ) was formed above 0.15 nm/s. The pseudorutile structure synthesized on this experiment was very stable in air. We concluded that the crystal structure of the pseudorutile is a new crystal structure of titanium oxide.     

Depth profiling of CdS homojunction using AES analysis

Top layer of spray pyrolyzedn-type CdS has been converted intop-type by diffusion of copper which resulted in the formation of homojunction. This is achieved by annealing CdS/Cu bilayer film. The nature of diffusion of copper atoms into CdS has been studied using auger electron spectroscopy (AES).     

Some new binary codes correcting asymmetric/unidirectional errors

The authors give a tabulation of the numbers of codewords in new binary codes with the asymmetric/unidirectional error-correcting capabilities of 3, 4, 5, 6 for lengths 14, 15, . . . , 23. The new codes have greater sizes than the known codes for 14⩽n⩽23 and 3⩽t⩽6     

Characteristic Instabilities in HfAlO Metal–Insulator–Metal Capacitors Under Constant-Voltage Stress

Time-dependent characteristic changes of metal-insulator-metal (MIM) capacitors with HfAlO dielectric prepared by atomic-layer deposition under constant-voltage stress (CVS) were studied. It was found that relative dielectric constant , dielectric loss , temperature coefficient of capacitance , and frequency coefficient of capacitance gradually increase during CVS testing, whereas the voltage dependence of capacitance weakens. It was also found that changes in -value, , and during CVS testing linearly depend on changes in . These three linear relationships are basically explained by a dielectric-response model proposed for a ldquoflat-lossrdquo dielectric. That is, the increases in -value, , and are attributed to the dielectric-loss increase caused by voltage stress. Stress-time dependence of the dielectric-loss increase is expressed very well by a power function. That is, the power exponent obtained by a curve fitting linearly increases with stress voltage and decreases with increasing aluminum concentration in the HfAlO dielectric. This result indicates that aluminum addition into the HfAlO dielectric can improve the characteristic stabilities of a MIM capacitor under voltage stress.     

Analysis of the spectrum behavior below the threshold in DFB lasers

The spectrum behavior below the threshold in DFB lasers has been investigated. Analysis shows that the emission spectrum has peaks predicted by the threshold theory and proper valleys between large peaks. The results of our analysis should aid in the evaluation of DFB structure parameters.     

Recovery of neutron-induced damage of SiC by thermal annealing up to 1400 °C

Recovery of the specimen length of neutron-irradiated SiC was observed using a precision dilatometer. The specimens were heated isothermally and isochronally. The accuracy of length measurement at high temperature using the dilatometer was compared with that of length measurement at room temperature using a micrometer. It was clarified that the dilatometer method showed high accuracy and stability. The dilatometer method was applied to observe length recovery by isothermal annealing at 1200 °C of the neutron-irradiated SiC, and at least two recovery rates were clarified.     

Measurement of thermal expansivity of low-expansion glasses by interferometric methods: Results of an interlaboratory comparison

An interlaboratory testing program on the measurement of the linear thermal expansion coefficient of low-expansion glasses has been carried out. Three different types of interferometric dilatometers, each located at three different organizations, and two kinds of low-expansion glass materials were selected for the experiments. As a result of the comparison, a reasonable agreement among the different measuring instruments was confirmed, and it was determined that the thermal expansion coefficient for low-expansion glasses can be measured with an accuracy of ±4×10^–8 K^–1 by using commercially available interferometric dilatometers.     

Homogeneous and Disordered Assembly of Densely Packed Nanocrystals

A homogeneous and disordered assembly of densely packed nanocrystals is generated without the assistance of organic molecules, from an aqueous solution at room temperature. The densely packed nanocrystals of tin dioxide (SnO₂) and titanium dioxide (TiO₂), 2–3 nm in size, form glassy macroscopic transparent objects of 2–10 mm. The monodisperse nanocrystals, which have a surface hydrated layer and are synthesized in aqueous solution, are densely packed in an homogeneous and disordered assembly through the evaporation of water as the dispersion medium. The formation of transparent bulk objects on the macroscopic scale originates from the homogeneous and disordered nature of the densely packed nanocrystals. The resultant homogeneous architectures are distinguishable from the typical inhomogeneous and disordered aggregates of nanoparticles observed after evaporation of the dispersion medium. Among superstructures based on nanocrystals, such as superlattices and mesocrystals, the resultant homogeneous and disordered assembly can be regarded as a new class of solid‐state material.