Quadratic soliton collisions

The details of two soliton collision processes were investigated in detail in a 1 cm long periodically poled KTP crystal for the case when the solitons were excited by inputting only the fundamental beam. The effects on the collision outcomes of the distance of the collision into the sample, collision angle and phase mismatch were measured for different relative phases between the input beams. At small angles ( around 0.4(0)) fusion, repulsion and energy transfer processes were observed, while at the collision angles approaching 3.2(0) the two output soliton beams were essentially unaffected by the interaction. The phase mismatch was varied from 3.5 to - 1.5pi for the 0.4(0) collision angle case. The output soliton separation at p input phase difference showed strongly asymmetric behavior with phase mismatch. In general, the measurements indicate a decrease in the interaction strength with increasing phase mismatch. All collision processes were performed in the vicinity of a non-critical phase matching

High-visibilty two-photon interference at a telecom wavelength using picosecond regime separated sources

We report on a two-photon interference experiment in a quantum relay configuration using two picosecond regime PPLN waveguide based sources emitting paired photons at 1550 nm. The results show that the picosecond regime associated with a guided-wave scheme should have important repercussions for quantum relay implementations in real conditions, essential for improving both the working distance and the efficiency of quantum cryptography and networking systems. In contrast to already reported regimes, namely femtosecond and CW, it allows achieving a 99% net visibility two-photon interference while maintaining a high effective photon pair rate using only standard telecom components and detectors.Comment: to appear in PRA as a rapid communicatio

Interférences à deux photons à 1550 nm pour les communications quantiques

Cette thèse présente l étude et la réalisation d une expérience d interférence à deux photons de type Hong-Ou-Mandel appelé aussi coalescence des photons. L originalité de notre travail réside dans l utilisation de deux sources de photons uniques annoncées indépendantes dont le fonctionnement requiert l utilisation de guides d ondes intégrés sur un substrat de niobate de lithium polarisé périodiquement (PPLN). Les photons acteurs de l interférence sont créés par génération paramétrique à la longueur d onde de 1550 nm nous assurant ainsi une compatibilité avec le réseau des fibres optiques télécom. Les guides PPLN présentent l avantage majeur d avoir une forte efficacité de conversion, mais ils permettent également de récolter aisément les photons à l aide d une fibre optique. Le travail effectué nous a conduit à étudier le comportement des guides dans différents régimes de fonctionnement : continu et impulsionnel. En effet, comparativement aux expériences de coalescence réalisés part le passé, nous avons choisi de travailler en régime picoseconde afin de faciliter l obtention de l interférence en regard de la synchronisation électronique et du filtrage a effectué. Les visibilités obtenus (99%) sont proches des limites théoriques et ces résultats montrent que le protocole expérimental mis en place peut devenir l un des éléments clés des futurs protocoles des communications quantiques utilisant les phénomènes de coalescence.This thesis presents the study and the realisation of a Hong-Ou-Mandel two-photon interference experiment, also known as photons coalescence. The originality of our work concerned is attached to dealing with two separate sources of independent unique photons whose operative mode requires using guide beams integrated on a periodically polarised lithium niobate substratum (PPLN). The photons, actors of the interference work, are created by parametric down conversion to 1550 nm beam wavelength insuring a compatibility with the telecom optic fibres network. The PPLN guides are particularly profitable because of their very strong conversion efficiency, but they also allow easy photons harvesting through an optic fibre. The work undertaken led us to study the guide s behaviour under different office regimes: continuous and impulsional. In fact, and in comparison to coalescence experiments formerly realised, our option was to perform in a picosecond s regime, aiming to obtain more easily the interference in regard of the electronic synchronisation and the strain filter to be realised. The 99 % visibilities, thus obtained are very close to the theoretical limits, and these results demonstrate that the experimental procedure realised can be one of the key elements of future quantum communication protocols exploiting the coalescence phenomenon.NICE-BU Sciences (060882101) / SudocSudocFranceF

Lateralization of the Vocal Fold: Results of an Exclusive Transoral Approach

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