Analytical and numerical study on grating depth effects in grating coupled waveguide sensors

The in-coupling process for grating-coupled planar optical waveguide sensors is investigated in the case of TE waves. A simple analytical model based on the Rayleigh–Fourier–Kiselev method is applied to take into account the depth of the grating coupler, which is usually neglected in the modeling. Analytical expressions are derived both for the position and width of the in-coupling peaks to illustrate the effects of grating depth on the guided mode resonances in grating coupled waveguide sensors. Numerical computations verify the model for shallow gratings both in terms of peak shape and position and provide the limitations for the analytical formulas.     

Stereoselective formation of silylketene acetals from esters and trialkylsilyl perchlorates.

Alkanoate esters react with triethylsilyl perchlorate and trialkylamines at low temperature to yield O-silylketene acetals. The $\text{Z}$ isomer is obtained in excellent yield.     

Solution of the differential equation (∂2∂x∂y + ax∂∂x + by∂∂y + cxy + ∂∂t) P(x,y, t) = 0 and the Bogoliubov transformation

An eigen function expansion for the solution of the Lambropolous partial differential equation is obtained by the use of a transformation similar to the Bugolubov transformation familiar in Bose gas theory. Also the technique of normal ordering of operators is employed. The orthogonality properties of such solutions are also analysed.     

Monolithic two-dimensional surface emitting arrays of GaAs/AlGaAs lasers

Surface emitting lasers are of interest for various applications such as monolithic two-dimensional arrays and optical interconnects for integrated optics. Moreover, surface emitting lasers offer the advantage of wafer processing and testing. Several approaches for achieving surface emission are described. In addition, TRW s fabrication of a large monolithic two dimensional array of GaAs/AlGaAs surface emitting lasers which contains a total of 100 lasers is reported.     

Synthesis and properties of unusual π-networks : Cycloocta[1,2,3,4]-def]benzo[3,4]cyclobuta[6,7[biphenylene

The title compound, an example of a hydrocarbon containing three linearly fused 4n-membered rings, has been synthesized and characterized as a thermally stable species possessing no unusual chemical reactivity. Despite the presence of these conventionally antiaromatic structural units this hydrocarbon is predicted to have a net diamagnetic ring current. The NMR results, which are discussed in some detail, are shown to be consistent with this expectation. The impact of this result on the NMR criterion of aromaticity is discussed briefly.     

A new approach to c-glycoside congeners: Metal carbene mediated methylenation of aldonolactones.

Versatile intermediates for the synthesis of C-glycosides and oxygen heterocycles are readily available through titanium mediated methylenation of aldonolactones.Aldonolactones may be alkylated using the titanium carbene complex 2. The resulting enol ethers are of value as potential substrates for glycosidase enzymes. A high yield two step process for alkylation of these enol ethers was described. The products and procedures are relevant to the synthesis of mycotoxins, including citreoviridin and aurovertin B.