Finite Element Analysis of Thermal Characteristics in Continuous Wave Long Wavelength Surface Emitting Lasers (II): Semiconductor Distributed Bragg Reflectors

We have numerically analyzed some thermal characteristics of cw long wavelength surface emitting lasers with epitaxially grown semiconductor distributed Bragg reflectors (DBRs). It was shown that the device thermal resistance for GaAs/AlAs DBRs epitaxially fused to GalnAsP/InP emitting layers is 1/3 of that for GalnAsP/InP DBRs and almost comparable to that for the optimum dielectric cavity. The threshold current lower than 10 mA and the electrical resistance lower than 100 Ω are necessary to obtain the cw operation beyond room temperature     

Absolute Measurement of Second-Order Nonlinear Optical Coefficient of LiNbO3 by Parametric Processes

We have redetermined the absolute values of the nonlinear optical coefficient, d₃₁, of LiNbO₃ by parametric fluorescence and, for the first time, by difference frequency generation measurements to resolve the considerable discrepancy that existed between the values determined by second-harmonic generation (SHG) and parametric fluorescence. We obtain d₃₁ = 4.8±0.5 and 4.3±0.5 pm/V at the pump wavelengths of 488 and 532 nm, respectively, in reasonable agreement with the SHG data. It appears that the previous parametric fluorescence value, d₃₁=5.8 pm/V, was overestimated.Author to whom correspondence should be addressed.     

Chemical analysis of impurity boron atoms in diamond using soft X-ray emission spectroscopy

To analyze the local structure and/or chemical states of boron atoms in boron-doped diamond, which can be synthesized by the microwave plasma-assisted chemical vapor deposition method (CVD-B-diamond) and the temperature gradient method at high pressure and high temperature (HPT-B-diamond), we measured the soft X-ray emission spectra in the CK and BK regions of B-diamonds using synchrotron radiation at the Advanced Light Source (ALS). X-ray spectral analyses using the fingerprint method and molecular orbital calculations confirm that boron atoms in CVD-B-diamond substitute for carbon atoms in the diamond lattice to form covalent B-C bonds, while boron atoms in HPT-B-diamond react with the impurity nitrogen atoms to form hexagonal boron nitride. This suggests that the high purity diamond without nitrogen impurities is necessary to synthesize p-type B-diamond semiconductors.     

A facile ring opening reaction of furfuryl selenides. Highly efficient method for dienones

Treatment of furfuryl phenyl selenides with butyllithium or metallic lithium induces the facile ring opening reaction of their furan ring and the corresponding dienones are obtained in high yields.     

Distribution of inorganic arsenic and methylated arsenic in marine organisms

Inorganic arsenic and methylated arsenic compounds in 60 specimens of marine organisms were investigated by hydride generation derivatization and cold-trap gas chromatography–mass spectrometry (GC MS). Chloroform–methanol extracts from seaweeds, shellfish, fish, crustaceans and other marine organisms were separated into water-soluble and lipid-soluble fractions. The arsenic compounds in each fraction were identified and analysed as arsine, methylarsine, dimethylarsine and trimethylarsine. Trimethylarsenic compounds were distributed mainly in the water-soluble fraction of muscle of carnivorous gastropods, crustaceans and fish. The amounts of dimethylated arsenic compounds were found to be larger than that of trimethylated arsenic in the lipid-soluble fraction of fish viscera. Dimethylated arsenic compounds were distributed in the water-soluble fraction of Phaeophyceae.     

Polarized Cu K-edge XANES of square planar CuCl42− ion. Experimental and theoretical evidence for shake-down phenomena

To elucidate the origin of the shoulder structure which is known to appear about half-way up the Cu K-edge in the X-ray absorption spectra of Cu(II) compounds, polarized X-ray absorption spectra were measured on the single crystal of (creatinium)₂CuCl₄ by using synchrotron radiation. The transition responsible for the shoulder structure was found to be exclusively polarized in the direction normal to the molecular plane of the CuCl₄^2? ion. The polarization dependence of other structures in the XANES spectra was also examined and compared with the results of ab initio SCF CI calculation. It is shown that the structure half-way up the Cu K-edge is due to the shake-down accompanying the 1s-4p= excitation, arising from the ligand-to-metal charge transfer induced by the core-hole creation. Structures attributable to the shake-down accompanying the 1s-4pσ and 1s-5p=, σ excitations were also found.     

Compactifications determined by subsets of C1(X)

It is well known that every compactification of a completely regular space X can be generated, via a Tychonoff-type embedding, by some suitably chosen subset of C¹(X). Different subsets may give rise to equivalent compactifications, and we are concerned with the problem of finding all subsets of C¹(X) which yield a given compactification αX. The problem is easier if generalized: we say that a subset F of C¹(X) “determines” the compactification αX if αX is the smallest compactification to which every element of F extends, and give a simple necessary and sufficient condition for F to determine a given compactification αX. A number of sufficient conditions for two sets to determine the same compactification are given, and the relation between sets which determine αX and those which generate αX (via an embedding) is considered. Generally, a much smaller set of functions is required to determine αX than to generate it; the number needed to determine αX is never more than the weight of αX?X, while the number required to generate it is, if infinite, equal to the weight of αX.     

Cycloadditions of 1,2-dihydrocyclobuta[c]quinolin-3 (4H) ones to olefins: new aza-analogues of ortho-quinodimethanes1

An usefulness of 1,2-dihydrocyclobuta[c]quinolin-3 (4) ones as synthons for organic synthesis for aza-analogues of benzocyclobutenes was demonstrated by their inter- and intramolecular cycloadditions to olefins.