Application of Automatic Chromatic Dispersion Compensation for Realization of All-Optical Network

We have studied the algorithm for the automatic chromatic dispersion compensation using bit error rate (BER) and Q-factor optimization for realization of dynamically reconfigurable all-optical network. We have made sure good performance using the compensation system by laboratory experiments.     

Combined system of optical coherence tomography and fluorescence spectroscopy based on double-cladding fiber

We report the development of an all-fiber multimodal system, based on a double-cladding fiber (DCF) and related devices, suitable for simultaneous measurements of optical coherence tomography (OCT) and fluorescence spectroscopy (FS). The DCF together with a DCF coupler and a single-body DCF lens has assisted in the realization of a multimodal but single-unit probe for the combined system. The DCF lens allowed simultaneous focusing of input beams for OCT and FS and also the effective collection of both signal beams from a sample. The DCF coupler could extract the OCT signal via the core channel and the FS signal through the cladding channel. The OCT image and the fluorescence spectra of a plant tissue were then simultaneously measured to validate the performance of the proposed multimodal system.     

Synthesis of new N-arylpyrimidin-2-amine derivatives using a palladium catalyst

New N-aryl-4-(pyridin-3-yl)pyrimidin-2-amine derivatives were synthesized from the corresponding amines, applying optimized Buchwald-Hartwig amination conditions using dichlorobis(triphenylphosphine)Pd(II), xantphos and sodium tertbutoxide in refluxing toluene under a nitrogen atmosphere. The target N-aryl derivatives were obtained in moderate to good yields ranging from 27% to 82%. The procedure described could be widely employed for the preparation of new heterocyclic compounds. The structures of the new compounds were confirmed by FT-NMR, FT-IR and elemental analysis.     

Novel chiral cyclic polysulfides with a biphenyl backbone: investigation of atropisomerism and pentathiepin ring inversion

Novel axially chiral benzopolysulfides were synthesized on biaryls by sulfurization of dithiastannoles. Pentathiepin, trithiole, and trithiole 2-oxide rings were observed as single isomer on 1,1′-biaryls. The rotational energy barrier of chiral axis was increased by incorporation of a methyl group at ortho-position. In that case, both trithiole oxide and pentathiepin rings appeared as diastereomer. ortho-Tolyl functionality was also replaced by naphthyl moiety to create more rotational hindrance. Chiral axis was incorporated at the neighborhood of polysulfide functionality by Suzuki-Miyaura cross-coupling reaction. Calculated rotational energy barriers were very much consistent with experimental observations to show atropisomerism. Energy barrier for the inversion of pentathiepin ring was experimentally determined by variable temperature ¹H NMR. The kinetic data suggested that pentathiepin ring inversion was prompt in solution. Insufficient rotational energy barriers of chiral axis and pentathiepin ring inversion make substantially impossible to separate optically pure diastereomer even by chiral chromatography [Preliminary report: Sato, R.; Ohta, H.; Yamamoto T.; Nakajo, S.; Ogawa, S.; Alam, A. Tetrahedron Lett.2007, 48, 4991-4994.].     

Infinitely many shape invariant discrete quantum mechanical systems and new exceptional orthogonal polynomials related to the Wilson and Askey–Wilson polynomials

Two sets of infinitely many exceptional orthogonal polynomials related to the Wilson and Askey–Wilson polynomials are presented. They are derived as the eigenfunctions of shape invariant and thus exactly solvable quantum mechanical Hamiltonians, which are deformations of those for the Wilson and Askey–Wilson polynomials in terms of a degree ?   (?=1,2,…$?=1,2,\dots$) eigenpolynomial. These polynomials are exceptional in the sense that they start from degree ??1$??1$ and thus not constrained by any generalisation of Bochner's theorem.     

Synthesis of Eu x Si6? z Al z O z N8? z green phosphor and?its?luminescent properties

Rare-earth-doped oxynitride or nitride compounds have been reported to be photoluminescent and may then serve as new phosphors because of their good thermal and chemical stabilities. In this work, Eu²⁺-doped β-SiAlON phosphor with a composition of Eu _x Si_6−z Al _z O _z N_8−z (x=0.018, z=0.23) was prepared by gas-pressured solid state reaction. The crystallinity and particle morphology of the prepared phosphor were characterized. The Stokes shift and zero-phonon line were calculated mathematically and estimated from the spectral data. The temperature dependence of photoluminescence was measured from 25 to 250°C. The prepared Eu²⁺-doped β-SiAlON green phosphor showed superior thermal quenching property compared to silicate (SrBaSiO₄:Eu²⁺) green phosphor. The white light-emitting diode (LED) back-lighting unit (BLU) using the prepared β-SiAlON:Eu²⁺ green phosphor exhibited higher color gamut than a commercial silicate phosphor.