Search results for "Waveguide"

Spectroscopic Investigations Of LB Mono- And Multilayers Of 2-docosylamino 5-nitropyridine; Promising Candidates For Non-linear And Integrated Optics

2005

Alkylamino-5-nitropyridineshavemently been introduced forthepreparation of a novel type of non-centrosymmetric Langmuir-Blodgett (LB) multilayer (1,2). Hitherto, second order non-linear optical investigations have been resmcted toLB-films oftwomaterialsinaltematinglayerstructureand to films of a single material with head to tail arrangement of the molecules, both of whicharedifficulttoobtain (seerefs. quotedin 1 and2.1. Incontrast,allpresent data indicate that LB-filmsof 2-aUcylamino-5-nitropyridines are head-to-head and tail-to-tail (Y-type) multilayers with a rather strong tilt-angle of the alkyl chains (Fig. I). The most effective substance for second order non-linear optical experiments…

Biosilica-based immobilization strategy for label-free OWLS sensors

2013

Abstract In the last years, a new group of enzymes, so-called silicateins, have been identified and characterized, which form the axial filaments of the spicules of the siliceous sponges, consisting of amorphous silica. Silicateins are able to catalyze the polycondensation and deposition of silica at mild conditions (low temperature and physiological pH). By means of these enzymes it is possible for the first time to produce silica nanostructures biocatalytically, which opens new ways for construction of biosensors. The cDNAs encoding the responsible enzymes have been isolated and the proteins can be produced in a recombinant way. Here we demonstrate the silicatein-mediated biosilica format…

Discrete exterior calculus for photonic crystal waveguides

2022

The discrete exterior calculus (DEC) is very promising, though not yet widely used, discretization method for photonic crystal (PC) waveguides. It can be seen as a generalization of the finite difference time domain (FDTD) method. The DEC enables efficient time evolution by construction and fits well for nonhomogeneous computational domains and obstacles of curved surfaces. These properties are typically present in applications of PC waveguides that are constructed as periodic structures of inhomogeneities in a computational domain. We present a two-dimensional DEC discretization for PC waveguides and demonstrate it with a selection of numerical experiments typical in the application area. …

SU-8 viļņvadu izveide ar tiešā ieraksta lāzera litogrāfijas tehniku un to optisko īpašību raksturošana

2016

Kopš 20.gs. beigām lieli pūliņi ieguldīti telekomunikāciju attīstībā, arvien tiek meklēti jauni materiāli, lai aizvietotu elektroniskās komponentes integrētajās shēmās, jo tās ir ierobežojošais faktors informācijas pārvades ātrumam. Viens no risinājumiem būtu veidot shēmas, kas satur tikai optiskās komponentes. Optisko komponenšu pamatā ir viļņvadi, kuriem jābūt ar noteiktām optiskām īpašībām. Viena no perspektīvākajām materiālu klasēm pielietojumiem fotoniskās integrālās shēmās ir organiskie materiāli. Darbā aprakstīta tīru un funkcionalizētu organisku SU 8 viļņvadu izgatavošana ar tiešā ieraksta lāzera litogrāfijas tehniku. Ir aprakstīti viļņvadu izgatavošanas soļi un metodes ierobežojumi…

Multipactor radiation analysis within a waveguide region based on a frequency-domain representation of the dynamics of charged particles

2009

[EN] A technique for the accurate computation of the electromagnetic fields radiated by a charged particle moving within a parallel-plate waveguide is presented. Based on a transformation of the time-varying current density of the particle into a time-harmonic current density, this technique allows the evaluation of the radiated electromagnetic fields both in the frequency and time domains, as well as in the near- and far-field regions. For this purpose, several accelerated versions of the parallel-plate Green's function in the frequency domain have been considered. The theory has been successfully applied to the multipactor discharge occurring within a two metal-plates region. The proposed…

Multiobjective muffler shape optimization with hybrid acoustics modelling

2010

Shape optimization of a duct system with respect to sound transmission loss is considered. The objective of optimization is to maximize the sound transmission loss at multiple frequency ranges simultaneously by adjusting the shape of a reactive muffler component. The noise reduction problem is formulated as a multiobjective optimization problem. The sound attenuation for each considered frequency is determined by a hybrid method, which requires solving Helmholtz equation numerically by finite element method. The optimization is performed using non-dominated sorting genetic algorithm, NSGA-II, which is a multi-objective genetic algorithm. The hybrid numerical method is flexible with respect …

Äänenvaimentimien mallinnuspohjainen monitavotteinen muodonoptimointi

2011

Multiobjective muffler shape optimization with hybrid acoustics modelling

2011

This paper considers the combined use of a hybrid numerical method for the modeling of acoustic mufflers and a genetic algorithm for multiobjective optimization. The hybrid numerical method provides accurate modeling of sound propagation in uniform waveguides with non-uniform obstructions. It is based on coupling a wave based modal solution in the uniform sections of the waveguide to a finite element solution in the non-uniform component. Finite element method provides flexible modeling of complicated geometries, varying material parameters, and boundary conditions, while the wave based solution leads to accurate treatment of non-reflecting boundaries and straightforward computation of the …

Electromagnetic wave propagation in non-homogeneous waveguides

2015

We investigate an electromagnetic waveguide, having several cylindrical ends. The waveguide is assumed to be empty and to have a perfectly conductive boundary. We study the electromagnetic field, excited in the waveguide in the presence of charges and currents. The field can be described as a solution of the stationary Maxwell system with conductive boundary conditions and “intrinsic” radiation conditions at infinity. We prove the problem to be well-posed. Electromagnetic waves propagation in the waveguide can be described by means of a scattering matrix. We introduce such a matrix for all values of the spectral parameter k in the waveguide continuous spectrum and study its properties. Moreove…

Microwave gas sensor based on graphene aerogel for breath analysis

2022

Exhaled breath can be used for early detection and diagnosis of diseases, monitoring metabolic activity, and precision medicine. In this work, we design and simulate a microwave sensor in which thin graphene aerogels are integrated into rectangular microwave waveguides. Graphene aerogels are ideal sensing platforms for gases and volatile compounds as they combine extremely high surface-to-volume ratio and good electrical conductivity at RF and microwave frequencies. The latter is modified by exposure to different gases, and -when integrated into a waveguide- these changes result in significant shifts in transmission and reflection scattering parameters. We model the aerogel as a graphene gr…