High-performance unidirectional electrooptic modulator based on polymeric highly multi-mode waveguides

A unidirectional electrooptic modulator based on an asymmetrical highly multi-mode waveguide coupler is proposed. Firstly, the energy distributions of all the modes within two highly multi-mode waveguides are analyzed with eigenstate theory. Then, to achieve high switching performance in a guided-wave coupler, a dumping wall is placed on the larger waveguide of an asymmetric pair of waveguides, so that the larger waveguide has a dumping effect. This dumping effect makes the asymmetric highly multi-mode waveguide coupler possess a highly efficient unidirectional coupling process. Due to the large cross-section of the waveguide, a new modulation electrode structure is built. Based on this dumping effect, the unidirectional coupling process is theoretically modeled. Furthermore, in both scenarios, i.e., the unmodulated state and the electrooptically modulated state, the unidirectional coupling efficiencies are studied. As a result, not only can a high unidirectional coupling efficiency of 100% be achieved, but a high electrooptic modulation depth more than 90% can also be implemented in theory, and a high thermooptic modulation depth more than 90% under a low modulation voltage of 30 volts is also experimentally achieved. This device can be used for multi-mode optical interconnection systems such as data communication and fiber sensor networks.     

Smiles rearrangement—XV: The S→N type rearrangement in uracil derivatives

The reaction of 1,3-dimethyl-6-(2-acetamidophenylthio)uracil 6 with caustic alkali followed by methylation gave 1,3-dimethyl-6-(2-methylthioanilino)uracil 7 accompanied with 1,3-dimethyl-5-acetyl-6-(2-methythioanilino)uracil 8. Pyrimido[1,5]benzothiazepine 10 was obtained in high yield by the Smiles rearrangement of 6, trapping of the resulting thiolate ion with formalin and subsequent acid-catalysed cyclization. Treatment of 1,3-dimethyl-6-(2-aminophenylthio)uracil 5 with hot acetic acid gave 1,3-bis[(2-benzothiazolyl)acetyl]-1,3-dimethylurea 12. Upon heating 5 or N-acetyl derivative 6 in dimethylsulfoxide, 5-thiaisoalloxazine 3 was obtained in moderate yield. Mechanisms of the observed reactions were discussed.     

Stability of helical textures in 3HeA in the presence of superflow

We analyze the stability of a variety of uniform textures in superfluid ³HeA in the presence of superflow p. We find below T_ins a class of stable helical l? textures, where l? is no longer aligned with p but winds around it with a constant pitch .     

Infrared spectrum of boron chloride (BCl)

The spectrum of the Δv = 1 band of BCl was measured between 828 and 870 cm^?1 with a tunable diode laser. The absorptions of the v = 1-0, 2-1, 3-2, and 4-3 transitions of BCl were observed in both a microwave discharge and a dc discharge through BCl₃. Spectra of ¹¹B³⁵Cl, ¹¹B³⁷Cl, ¹⁰B³⁵Cl, and ¹⁰B³⁷Cl were observed in natural abundance. A set of eight Dunham coefficients was determined by fitting the data for all observed isotopic species with the appropriate reduced mass factors. A BCl bond distance, r_e = 0.1715283(31) nm, was determined which agrees with the value derived from the electronic spectrum of BCl. The band center for the v = 1-0 transition of ¹¹B³⁵Cl is ν₀ = 829.4087(8) cm^?1.     

Effect of Br− ions on the F-center formation in KCl crystals under u.v. light irradiation

The relative efficiency of the F-center formation, Y_F in KCl crystals has been studied as a function of photon energy of u.v. light between 5.7 and 10.0 eV. Y_F is maximum at the peak of the absorption band due to the localized excitons at Br^? ions, and increases with Br^? concentration. Results suggest an important role of the localized excitons in the F-center formation.     

Carbon background in P-based III-V semiconductors grown by metalorganic molecular beam epitaxy using ethyl-metalorganic sources

Electrical properties of InP, GaP, InGaP and AlGaP, grown by metalorganic molecular beam epitaxy (MOMBE) using ethyl-metalorganics (triethyl-indium, -gallium and -alluminum), are discussed in connection with the carbon background. More C atoms are incorporated into epilayers in the order of AlGaP, GaP and InP. The C atoms act as accepters in AlGaP and GaP epilayers, but they probably work as donors in InP. InGaP showed highly resistive or compensated possibly due to the amphoteric nature of C atoms.     

Magnetosonic wave in the A1 phase of superfluid 3He

The dispersion of the spin wave as well as the magnetosonic wave in the A₁ phase is determined. The magnetosonic wave is the fourth sound accompanied by the magnetization, which provides almost unique means to determine the spin orientation of the condensate in the A₁ phase.