Seeded and unseeded high order parametric down conversion

Spontaneous parametric down conversion (SPDC) has been one of the foremost tools in quantum optics for over five decades. Over that time it has been used to demonstrate some of the curious features that arise from quantum mechanics. Despite the success of SPDC, its higher-order analogues have never been observed, even though it has been suggested that they generate far more unique and exotic states than SPDC. An example of this is the emergence of non-Gaussian states without the need for post-selection. Here we calculate the expected rate of emission for nth-order SPDC with and without external stimulation (seeding). Focusing primarily on third-order parametric down-conversion (TOPDC), we estimate the photon detection rates in a rutile crystal, for both the unseeded and seeded regimes.Comment: 11 pages, 6 figure

Specialty Photonic Crystal Fibers and Their Applications

This year not only commemorates the 60th anniversary of nonlinear optics with the seminal experiment of second harmonic generation [...

Travel and activity time allocation: An empirical comparison between eight cities in Europe

A study of daily time allocation to travel and out-of-home activity is conducted across eight European cities over three countries: France (Lyon, Grenoble, Strasbourg and Rennes), Switzerland (Geneva, Bern and Zurich) and Belgium (Brussels), based on individual travel survey data collected between 1997 and 2006. The effects of socio-demographic, spatial context, transport availability and city-specific variables are investigated thanks to the Cox proportional hazard model. The results indicate that socio-demographic characteristics and city (or country) specific effect play a major role while residential density and proximity to high level road or public transport networks have a very limited impact on time budgets for travel and out-of-home activities.Travel ; Activity ; Time allocation ; Cities ; Europe ; Duration model

Comment mesurer l'impact érosif des dynamiques de l'occupation du sol ? Approche pluridisciplinaire dans la vallée de la Choisille (Indre-et-Loire, France)

International audienceThe Choisille valley, in the north of Tours (37), has been a laboratory for a multidisciplinary experiment which was aimed at measuring the impact of human activities on soil erosion, conducted within the ECLIPSE II program. We propose a synthesis of the acquired knowledge about land use evolution based on archaeological, written and environmental data analyzed within a GIS. This information documents the settlement and landscape dynamics at different time and space scales, and provides a partial explanation to the variation of sediments recording within the Choisille valley.La vallée de la Choisille au nord de Tours (37) a été un laboratoire pour une expérience multidisciplinaire visant à mesurer l'impact des activités anthropiques sur l'érosion des sols, expérience réalisée dans le cadre du programme ECLIPSE II. Nous proposons la synthèse des connaissances acquises sur l'évolution de l'occupation du sol à partir des données archéologiques, écrites, planimétriques et environnementales analysées au sein d'un SIG. Ces informations documentent les dynamiques de l'habitat et du paysage à différentes échelles de temps et d'espace, et permettent en partie d'expliquer les variations de l'enregistrement sédimentaire au sein de la vallée de la Choisille

Low-noise supercontinuum generation in chiral all-normal dispersion photonic crystal fibers

We present the advantages of supercontinuum generation in chiral, therefore circularly birefringent, all-normal dispersion fibers. Due to the absence of nonlinear power transfer between the polarization eigenstates of the fiber, chiral all-normal dispersion fibers do not exhibit any polarization instabilities and thus are an ideal platform for low-noise supercontinuum generation. By pumping a chiral all-normal dispersion fiber at 802 nm, we obtained an octave-spanning, robustly circularly polarized supercontinuum with low-noise.Comment: 4 pages, 5 figure

Exponential decay for the damped wave equation in unbounded domains

We study the decay of the semigroup generated by the damped wave equation in an unbounded domain. We first prove under the natural geometric control condition the exponential decay of the semigroup. Then we prove under a weaker condition the logarithmic decay of the solutions (assuming that the initial data are smoother). As corollaries, we obtain several extensions of previous results of stabilisation and control