Noise analysis of an electro-optic sensor system

Optical Review - This paper describes the noise analysis of an electro-optic (EO) sensor system based on experimental and simulation results. We developed a polarization simulator of the EO sensor...     

Fluorogenic probes for aldol reactions: tuning of fluorescence using π-conjugation systems

Fluorogenic aldehydes or probes for monitoring of the progress of aldol reactions have been developed. Fluorescence of benzaldehydes conjugated with aryl groups via a double or triple bond and of their aldol products was evaluated in aqueous solutions. Based on the fluorescence, fluorogenic aldol reaction substrates and retro-aldol reaction substrates were identified. Use of the probe system with optimal fluorescence properties for aldol reactions was demonstrated in assays with purified protein catalysts and with overproduced crude protein catalysts in cell lysates.     

Signal measurement system for intra-body communication using optical isolation method

In this paper, we describe an induced signal measurement on the human body for developing a high-performance transceiver of an intra-body communication system. It is important to isolate awearable transceiver from an electrical instrument for precise measurement. We have developed a probe system using an optical isolation method including a laser diode, photo-diode, and optical fiber. The probe system can be successfully applied to the precise measurement of a receiving signal power at a wearable transceiver. We verify that the experimental results agree with the simulation results based on our previous channel model of intra-body communication.     

Optical characteristics of one-dimensional photonic crystals composed of high-aspect-ratio Si walls fabricated on V-grooved wafer

We demonstrate optical properties of one-dimensional photonic crystals (PC), which are fabricated using high-aspect-ratio etching on a V-grooved silicon wafer. The measured transmission spectrum has an obvious band gap; the suppression is over 30 dB. The quite small insertion loss of 1.9 dB is achieved by induced coupled plasma (ICP) cryogenic etching and direct coupling to the optical fiber aligned in the V-groove. We also successfully observed peaks originating from a localized cavity mode. Such a microcavity enables control of the light, which qualifies photonic crystal as a fundamental structure of optical functional devices. These results lead to achievement of integrated Si-based photonic circuits.     

Applying a Mode Selector to Improve the Pulse-Compression Performance of Asymmetric-Coupled-Waveguide-Based Dispersion Compensators

An InGaAsP slab-type asymmetric-coupled-waveguide-based dispersion compensator with a mode selector has been designed and fabricated. The mode selector is necessary to select either a symmetric [with a positive group-velocity dispersion (GVD)] or antisymmetric (with a negative GVD) supermode. These supermodes exist simultaneously in the dispersion-compensation region of the device. Pulse-compression experiments were used to test the dispersion compensator, evaluating the function of the mode selector. A theoretical study of the experimental results shows that the mode selector obtains a very strong selectivity (nearly 100%) for the antisymmetric supermode.     

Reconstitution of a Type II Polyketide Synthase that Catalyzes Polyene Formation

While type II polyketide synthases (PKSs) are known for producing aromatic compounds, a phylogenetically new subfamily of type II PKSs have been recently proposed to synthesize polyene structures. Here we report in vitro analysis of such a type II PKS, IgaPKS for ishigamide biosynthesis. The ketoreductase (Iga13) and dehydratase (Iga16) were shown to catalyze the reduction of a β‐keto group and dehydration of a β‐hydroxy group, respectively, to form a trans double bond. Incubation of the acyl carrier protein (Iga10), the ketosynthase/chain length factor complex (Iga11–Iga12), Iga13 and Iga16 with malonyl and hexanoyl‐CoAs and NADPH followed by KOH hydrolysis resulted in the formation of four unsaturated carboxylic acids (C₈, C₁₀, C₁₂, and C₁₄), indicating that IgaPKS catalyzes tetraene formation by repeating the cycle of condensation, keto‐reduction and dehydration with strict stereo‐specificity. We propose “highly reducing type II PKS subfamily” for the polyene‐producing type II PKSs.     

Size, position and direction control on GaAs and InAs nanowhisker growth

The self-organized, position-controlled and parallel growth of GaAs and InAs nanowhiskers is successfully demonstrated by using a metal–organic chemical vapour deposition method. The growth takes place preferentially along the 111 As direction with the aid of the catalytic effect of Au nanodroplets, and not along 111 Ga or In directions. The diameter and length of the whisker can be controlled artificially down to 10 nm and to over 1 μm, respectively. Doping and composition control of p- or n-type such as GaAs–InAs heterostructure formation are possible along the length direction of the whisker by changing the source gases. In order to control the growth position of the whisker, positioning of a Au nanodroplet is essential and realized by a lithographic method. By choosing the [111]B direction to the substrate surface and normal to the patterned side edges, and by positioning the Au nanodroplet on the side wall, the positioned planar nanowhisker growth and bridging are successfully demonstrated. The growth mechanism of the nanowhiskers is revealed by the scanning and transmission electron microscope observations. Nanometer-size Au-alloy droplets play an important role in the growth of the whiskers. The whisker growth process is governed by the vapor–liquid–solid growth mechanism.     

57Fe and57Co Mössbauer studies of highT c Y-Ba-Cu oxides

The⁵⁷Co emission Mössbauer spectra from YBa₂Cu₃O_6.92 (1-2-307) and YBa₂Cu₃O_6.00 (1-2-306) have been measured and compared with the⁵⁷Fe absorption spectra from YBa₂Cu_2.95Fe_0.05O_7?δ in order to clarify decisively the site assignments for the⁵⁷Fe quadrupole-split doublets in these compounds. Mössbauer spectra obtained from both specimens consist of four components whose hyperfine interaction parameters well agree with each other. It is shown that the Co and Fe atoms mainly substitute at Cu1 chain sites in 1-2-307, but in 1-2-306 the Co atoms occupy randomly the Cu2 plane sites and indicate magnetically-split sextet which converts to a paramagnetic doublet of S-state Fe³⁺ in 1-2-307 by a post-annealing in O₂ gas.     

Refractive index behavior of SiO2-P2O5 glass in optical fiber application

The refractive index of SiO₂-P₂O₅ glass prepared by a modified chemical vapor deposition method is measured using an interference microscope. It is found that the refractive index in bulk form increases linearly at 9.5×10^-4 (mol.%)^-1 as the P₂O₅ concentration increases. It is also found that quenching at extremely high speed reduces the refractive index over 2 mol.% P₂O₅. The wavelength dispersion of the refractive index dn/dλ is constant up to 5 mol.% P₂O₅ producing a refractive index difference of 5×10^-3 compared with fused silica. Consequently, this glass materials is thought to be suitable for wide band-width optical fiber applications.     

Synthesis of 4,6-disubstituted 2-methylpyridines and their 3-carboxamides

A new one-pot synthesis of title compounds by the reactions of α,β-unsaturated carbonyl compounds with β-aminocrotononitrile in the presence of sodium hydroxide is described.