Phase sensitivity of directional couplers

Directional couplers of various design have been treated widely, both theoretically and experimentally. However, in most cases directional couplers are designed as 1 to 2 port circuits. If both input ports are used, the phase of the guided waves has to be taken into account. The influence of the phase term on the switching behaviour of Δβ-reversal couplers is discussed as an example. It is shown that the phase difference of two waves coupled to both coupler input ports will not affect crossover and straight-through states, but all states in between. Therefore electrical controlled 2 to 2 port switches will become very sensitive, if low crosstalk is required. This effect can be used to design an all optical working switch or optical logic.     

Asymptotic expansion of highly conductive thin sheets

Sensitive measurement and control equipment are protected from disturbing electromagnetic fields by thin shielding sheets. Alternatively to discretisation of the sheets, the electromagnetic fields are modeled only in the surrounding of the layer taking them into account with the so called Generalised Impedance Boundary Conditions. We study the shielding effect by means of the model problem of a diffusion equation with additional dissipation in the curved thin sheet. We use the asymptotic expansion techniques to derive a limit problem, when the thickness of the sheet ε tends to zero, as well as the models for contribution to the solution of higher order in ε. These problems are posed in limit area of vanishing ε with condition for the jump of the solution and it's normal derivative, which avoid to mesh the computational domain, even locally, at the scale of ε. We derive the problems for arbitrary order and show their existence and uniqueness. Numerical experiments for the problems up to second order show the asymptotic convergence of the solution of right order in mean of the thickness parameter ε. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the determination of energy fluxes at plasma–surface processes

A summary is given of different methods for the determination of the energy influx and its influence on the thermal balance and energetic conditions of substrate surfaces during plasma processing. The discussed mechanisms include heat radiation and kinetic and potential energy of charged particles and sputtered neutrals. For a few examples such as magnetron sputtering of a-C:H films, sputter deposition of aluminum on microparticles, and titanium deposition in a hollow-cathode arc evaporation device the energetic balance of substrates during plasma processing is presented. Received: 6 July 2000 / Accepted: 12 December 2000 / Published online: 3 April 2001     

On Integrability of the Camassa–Holm Equation and Its Invariants

Using geometrical approach exposed in (Kersten et al. in J. Geom. Phys. 50:273–302, [2004] and Acta Appl. Math. 90:143–178, [2005]), we explore the Camassa–Holm equation (both in its initial scalar form, and in the form of 2×2-system). We describe Hamiltonian and symplectic structures, recursion operators and infinite series of symmetries and conservation laws (local and nonlocal). This work was supported in part by the NWO–RFBR grant 047.017.015 and RFBR–Consortium E.I.N.S.T.E.I.N. grant 06-01-92060.     

The Thermal Balance of Substrates During Plasma Processing

In this paper an example is given for measurement and calculation of the energy influx towards a substrate during plasma processing in a supersonic reactor. From the results the energy transfer coefficients are obtained for several pressures. Also the evolution of the profile of the temperature is presented.     

Photoluminescence spectra of self-assembling helical supramolecular assemblies: a theoretical study

The reversible assembly of helical supramolecular polymers of chiral molecular building blocks is known to be governed by the interplay between mass action and the competition between weakly and strongly bound states of these building blocks. The highly co-operative transition from free monomers at high temperatures to long helical aggregates at low temperatures can be monitored by photoluminescence spectroscopy that probes the energetically lowest-lying optical excitations in the assemblies. In order to provide the interpretation of obtained spectroscopic data with a firm theoretical basis, we present a comprehensive model that combines a statistical theory of the equilibrium polymerization with a quantum-mechanical theory that not only accounts for the conformational properties of the assemblies but also describes the impact of correlated energetic disorder stemming from deformations within the chromophores and their interaction with solvent molecules. The theoretical predictions are compared to fluorescence spectra of chiral oligo(p-phenylene-vinylene) molecules in the solvent dodecane and we find them to qualitatively describe the red-shift of the main fluorescence peak and its decreasing intensity upon aggregation.