We describe the use of two-photon absorption in submicron silicon wire waveguides for all-optical switching by cross-absorption modulation. Optical pulses of 3.2 ps were successfully converted from high power pump to low power continuous-wave signal with a fast recovery time. High speed operation was based on the induced optical absorption from non-degenerate two-photon absorption inside the waveguides.

The switching speed of conventional silicon-based optical switching devices based on plasma dispersion effect is limited by the lifetime of free carriers which introduce either phase or absorption changes. Here we report an all-optical logic NOR gate which does not rely on free carriers but instead uses two-photon absorption. High speed operation was achieved using pump induced non-degenerate two-photon absorption inside the submicron size silicon wire waveguides. The device required low pulse energy (few pJ) for logic gate operation. Ó 2006 Elsevier B.V. All rights reserved.All-optical digital signal processing may be needed in future high capacity optical networks to overcome the speed limitations of electronics. All-optical logic gates such as NOR gate will be needed to perform the optical digital signal processing to accommodate the massive amount of traffic in terabit optical networks [1]. In addition, NOR gate can be used in performance monitoring for error detection, address and header recognition [2], encryption and data encoding [3], etc. Optical logic gates have been demonstrated in nonlinear optical fibers [4], semiconductor optical amplifier (SOA) [5] and InGaAs/AlAsSb coupled double-quantum-well structures [6]. The latency and high optical power level for nonlinear operation make fiberbased devices unattractive for practical applications, while the long carrier lifetime in conventional SOAs may limit the speed unless some complicated differential switching scheme is employed.Submicron size silicon wire waveguides are possible because of the extremely high index contrast (n = 3.5 for silicon, and n = 1.45 for SiO 2 ), which allows the dimension of waveguides to be much smaller than in conventional low index contrast silica waveguidess [7]. The strong optical confinement and small effective modal area (<0.1 lm 2 ) of such waveguides can produce high optical intensities even at input optical powers typically used in telecommunications. The high optical intensities and long interaction lengths in the waveguides allow nonlinear optical effects to be readily apparent. Apart from other nonlinear optical devices such as optical fibers and SOA, silicon wire waveguides have good potential for other nonlinear devices for ultrafast photonics signal processing [8].We demonstrated previously an ultrafast optical switch (<3 ps) with pJ pump pulse energy in wire waveguides [9,10]. In this paper, we develop a high speed all-optical logic NOR gate based on the nonlinear transmission characteristics of two-photon absorption (TPA) in silicon. The direct use of TPA allows operation speeds which are not limited by the slow photo-generated carrier lifetime in the silicon wire waveguides.Since the sum of energies of two photons at 1.55 lm wavelength is greater than the indirect bandgap of silicon, 0030-4018/$ -see front matter Ó

We review the basic linear and nonlinear properties of silicon-on-insulator photonic wire waveguides and their application to nanophotonic circuits. We give an overview of the performance and issues of basic circuit elements such as couplers and intersections and review the achievements in linear wavelength-selective elements, as well as nonlinear applications of wires and resonators for high-speed signal processing.

Ondanks de grote wandaden gedurende de Tweede Wereldoorlog bleek het extreemrechtse segment helemaal niet verdreven te zijn uit de maatschappij. Gewelddaden zoals die van Anders Behring Breivik doen ons terugdenken aan het nazistische beeld van massamoord, vernietiging en verovering. Ook in Vlaanderen werd de maatschappij geconfronteerd met extreemrechts partijen, groeperingen en individuen die radicaal hun stempel wensten te drukken op de hedendaagse samenleving. Politionele en justitie¨le diensten konden aanvankelijk amper in beperkte mate reageren tegen deze vorm van extremisme. Toch kon men in 2010 de activiteiten van groeperingen zoals Blood and Honour sterk terugdringen. kennis van doelgroep en groepsprocessen Belgisch wetenschappelijk onderzoek: focus op partijpolitiek extreemrechts buitenparlementaire extreemrechtse bewegingen Veiligheidsbeleid -Integrale veiligheid Handboek Politiediensten Rechts-extremistische groeperingen in Vlaanderen / 4 Afl. 105, 40, maart 2013 Veiligheidsbeleid -Integrale veiligheid beperkte wetenschappelijke aandacht artikeloverzicht Handboek Politiediensten Veiligheidsbeleid -Integrale veiligheid Afl. 105, 41, maart 2013 Rechts-extremistische groeperingen in Vlaanderen / 5 Rechts-extremistische groeperingen in Vlaanderen

We demonstrate TE/TM mode conversion in silicon waveguides. The application of stress by oxide patches and etched oxide windows respectively enabled over 40% polarization conversion and allowed operation over a wide wavelength range.

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Abstract:We demonstrate for the first time an all-optical logic NOR gate in submicron size silicon wire waveguides. High speed operation at equivalent 80Gbps data rate was achieved using pump induced non-degenerate two-photon absorption inside the waveguides. The device requires low pulse energy (few pJ) for logic gate operation.

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