Search results for "Waveguide"
showing 10 items of 311 documents
Random quasi-phase matching in congruent lithium tantalate waveguides by proton exchange
2012
A report is presented on broadband second-harmonic generation in the range between 930 and 970 nm using random quasi-phase matching in a planar waveguide fabricated by soft proton exchange in congruent lithium tantalate. Bulk and waveguide measurements are compared, outlining the averaging role of guided-wave modes and their interactions with respect to spectral acceptance and near-field profile.
CAD of complex passive devices composed of arbitrarily shaped waveguides using Nyström and BI-RME methods
2004
In this paper, a novel computer-aided design (CAD) tool of complex passive microwave devices in waveguide technology is proposed. Such a tool is based on a very efficient integral-equation analysis technique that provides a full-wave characterization of discontinuities between arbitrarily shaped waveguides defined by linear, circular, and/or elliptical arcs. For solving the modal analysis of such arbitrary waveguides, a modified version of the well-known boundary integral-resonant-mode expansion (BI-RME) method using the Nyström approach, instead of the traditional Galerkin version of the method of moments, is proposed, thus providing significant savings on computational costs and implement…
FDTD characterization of evanescent modes-multimode analysis of waveguide discontinuities
2000
In this paper, a finite-difference time-domain numerical dispersion relation for evanescent waves is derived, and its impact on the modeling accuracy is studied. The numerical evanescent constant is found to differ from the analytical one. As a result, a correction must be used to compute discontinuity parameters. This influences the reference plane chosen for the analysis of propagating modes. Moreover, on calculating multimode transmission and reflection coefficients, the dispersion for evanescent higher order modes is determinant. The dispersive relation is derived, discussed, and used to correct the evanescent constants for the multimode analysis of a waveguide discontinuity.
Kinetic evidence for the solubilization of pyridine-2-azo-p-dimethylaniline in alkanediyl-α,ω-bis(dimethylcetylammonium nitrate) surfactants. Role of…
2004
The incorporation of the bidentate ligand pyridine-2-azo-p-dimethylaniline (PADA) into micellar aggregates of the dimeric cationic surfactants propanediyl-, hexanediyl- and dodecanediyl-alpha,omega-bis(dimethylcetylammonium nitrate) (16-3-16,2NO(3)(-), 16-6-16,2NO(3)(-) and 16-12-16,2NO(3)(-), respectively) has been studied at 25 degreesC by examining the kinetics of the complexation reaction of the Ni(II) ion with this ligand. For comparison, cetyltrimethylammonium nitrate ( CTAN), which can be considered as the "monomeric'' surfactant of 16-3-16,2NO(3)(-), has also been used. The kinetic data have shown that, for 16-3-16,2NO(3)(-) and CTAN, at a surfactant concentration below the critical…
STUDIO DEI DIFFUSORI DI SCHROEDER E MODELLAZIONE MEDIANTE DWM (DIGITAL WAVEGUIDE MESH)
2012
Sono stati trattati due differenti argomenti: lo studio della diffusione delle onde acustiche per mezzo dei diffusori di Schroeder e la modellazione acustica tramite la Digital Waveguide Mesh (DWM). E’ stato prima affrontato lo studio delle sequenze numeriche a spettro costante e il modo in cui esse vengono generate. La progettazione dei diffusori è stata studiata, partendo da una formulazione semplificata in campo lontano e variando i parametri di progetto sono stati ricavati i diagrammi polari di diffusione. In particolare, mediante i diagrammi polari in campo lontano è stata considerata la variazione della diffusione al variare della classe di sequenza (QRD, PRD, MLS), della lunghezza N …
Towards Si-based photonic circuits: Integrating photonic crystals in silicon-on-insulator platforms
2007
In the context of Si-based photonics, we report on a strategy to integrate two optical components, a 3D photonic crystal light emitter and a waveguide, in a silicon-on-insulator patterned substrate. Self-assembled colloidal photonic crystals are produced with high crystalline quality and spatial selectivity. Plane wave expansion and finite-difference time-domain have been used to find suitable configurations for positioning emitters and waveguides. The first steps toward the realisation of these configurations are presented.
Exploiting the optical quadratic nonlinearity of zinc-blende semiconductors for guided-wave terahertz generation: A material comparison
2010
We present a detailed analysis and comparison of dielectric waveguides made of CdTe, GaP, GaAs and InP for modal phase matched optical difference frequency generation (DFG) in the terahertz domain. From the form of the DFG equations, we derived the definition of a very general figure of merit (FOM). In turn, this FOM enabled us to compare different configurations, by taking into account linear and nonlinear susceptibility dispersion, terahertz absorption, and a rigorous evaluation of the waveguide modes properties. The most efficient waveguides found with this procedure are predicted to approach the quantum efficiency limit with input optical power in the order of kWs.
Telecom-compatible, affordable and scalable quantum technologies
2022
The realistic implementation of quantum architectures relies on the development of scalable, resource-efficient platforms that are compatible with CMOS technologies as well as fiber networks. This work demonstrates novel schemes utilized for time-/frequency-bin entanglement generation and processing by leveraging existing telecommunications and integrated photonics infrastructures.
Advanced Signal Processing for Ultrasonic Structural Monitoring of Waveguides, in Bridge Maintenance, Safety Management, Health Monitoring and Inform…
2008
Ultrasonic Guided Waves (UGWs) are a useful tool in those structural health monitoring applications that can benefit from built-in transduction, moderately large inspection ranges and high sensitivity to small flaws. This paper describes a damage detection method, based on wavelet transform and outlier analysis for structural waveguides. The method combines the advantages of UGW inspection with the outcomes of the Discrete Wavelet Transform (DWT) that is used for extracting defect-sensitive features that can be combined to perform a multivariate diagnosis of damage. In particular, the DWT is exploited to generate a set of relevant wavelet coefficients to construct a uni-dimensional or multi…
Advanced nonlinear signal processing in silicon-based waveguides
2015
This talk presents recent progress in optical signal processing based on compact waveguides fabricated mainly using silicon germanium alloys. Applications include supercontinuum generation, wavelength conversion and signal regeneration.