Tapered-amplified AR-coated laser diodes for Potassium and Rubidium atomic-physics experiments

We present a system of room-temperature extended-cavity grating-diode lasers (ECDL) for production of light in the range 760-790nm. The extension of the tuning range towards the blue is permitted by the weak feedback in the cavity: the diodes are anti-reflection coated, and the grating has just 10% reflectance. The light is then amplified using semiconductor tapered amplifiers to give more than 400mW of power. The outputs are shown to be suitable for atomic physics experiments with potassium (767nm), rubidium (780nm) or both, of particular relevance to doubly-degenerate boson-fermion mixtures

Kilohertz-resolution spectroscopy of cold atoms with an optical frequency comb

We have performed sub-Doppler spectroscopy on the narrow intercombination line of cold calcium atoms using the amplified output of a femtosecond laser frequency comb. Injection locking of a 657-nm diode laser with a femtosecond comb allows for two regimes of amplification, one in which many lines of the comb are amplified, and one where a single line is predominantly amplified. The output of the laser in both regimes was used to perform kilohertz-level spectroscopy. This experiment demonstrates the potential for high-resolution absolute-frequency spectroscopy over the entire spectrum of the frequency comb output using a single high-finesse optical reference cavity.Comment: 4 pages, 4 Figure

An Ultra-Stable Referenced Interrogation System in the Deep Ultraviolet for a Mercury Optical Lattice Clock

We have developed an ultra-stable source in the deep ultraviolet, suitable to fulfill the interrogation requirements of a future fully-operational lattice clock based on neutral mercury. At the core of the system is a Fabry-P\'erot cavity which is highly impervious to temperature and vibrational perturbations. The mirror substrate is made of fused silica in order to exploit the comparatively low thermal noise limits associated with this material. By stabilizing the frequency of a 1062.6 nm Yb-doped fiber laser to the cavity, and including an additional link to LNE-SYRTE's fountain primary frequency standards via an optical frequency comb, we produce a signal which is both stable at the 1E-15 level in fractional terms and referenced to primary frequency standards. The signal is subsequently amplified and frequency-doubled twice to produce several milliwatts of interrogation signal at 265.6 nm in the deep ultraviolet.Comment: 7 pages, 6 figure

Atomic fountains and optical clocks at SYRTE: status and perspectives

In this article, we report on the work done with the LNE-SYRTE atomic clock ensemble during the last 10 years. We cover progress made in atomic fountains and in their application to timekeeping. We also cover the development of optical lattice clocks based on strontium and on mercury. We report on tests of fundamental physical laws made with these highly accurate atomic clocks. We also report on work relevant to a future possible redefinition of the SI second

De los escenarios a las trayectorias de desarrollo para la seguridad alimentaria bajo cambio climático en Honduras. Serie 1. Impacto Nacional

Los escenarios futuros son una excelente oportunidad de capturar las principales preocupaciones de los múltiples actores de una región. Al igual que contribuir con las discusiones orientadas a la priorización y planeación de sus intervenciones. Los escenarios futuros dibujan una potencial vulnerabilidad del sistema nacional de alimentos bajo dos estrategias de estímulo al sector agrícola, comercial y asociado a seguridad alimentaria. Toda vez que las condiciones climáticas futuras exacerbarían las productividades, el uso del suelo y el posicionamiento en el comercio mundial. Dada las características de la dieta, la geografía económica y los procesos de urbanización, los escenarios en su capacidad de simplificación dejan entrever la necesidad de estimular y desarrollar las capacidades de adaptación local. Para ello, el rol de las instituciones y en general de todos los involucrados en ejercicios de prospectiva estratégica, reduce la incertidumbre futura y mejora la priorización de las acciones colectivas.Future scenarios are an excellent opportunity to capture the main concerns of the multiple actors in a region. As well as contributing to the discussions aimed at prioritizing and planning their interventions. Future scenarios draw a potential vulnerability of the national food system under two strategies to stimulate the agricultural, commercial and food security sector. Since future weather conditions would exacerbate productivity, land use and position in world trade. Given the characteristics of the diet, economic geography and urbanization processes, the scenarios in their capacity for simplification suggest the need to stimulate and develop local adaptation capacities. For this, the role of institutions and in general of all those involved in strategic prospective exercises reduces future uncertainty and improves the prioritization of collective actions

Distribución espacial de la vulnerabilidad futura bajo escenario de cambio climático. Serie 3. Análisis municipal para Corredor Seco hondureño.

Mediante la prospectiva estratégica y la ciencia de los datos, se puede dibujar diferentes trayectorias del impacto futuro al sistema agrícola hondureño en respuesta al cambio climático. Los escenarios proyectan tendencias negativas en los cultivos básicos en la demanda de los hogares y cultivos con gran valor comercial. El cambio climático afectaría la aptitud de los territorios para la siembra de cultivos de alta importancia en la dieta local. Esto podría influir en la distribución del suelo y el ordenamiento del espacio rural. La vulnerabilidad en el Corredor Seco en el futuro presentaría patrones claros de aglomeración. Entendiendo que estos fenómenos indeseables pueden ser persistentes en el tiempo, se demandaría una política integral que armonice las acciones locales y nacionales, coordinando el actuar de múltiples instituciones publico privadas en la región del Corredor Seco.Through the strategic prospect and data science, different trajectories of the future impact on the Honduran agricultural system can be drawn in response to climate change. The scenarios project negative trends in basic crops in the demand of households and crops with great commercial value. Climate change would affect the territories' ability to plant crops of high importance in the local diet. This could influence the distribution of land and the arrangement of rural space. Vulnerability in the Dry Corridor in the future would present clear agglomeration patterns. Understanding that these undesirable climatic events can be persistent over time, a comprehensive policy that harmonizes local and national actions would be demanded, coordinating the actions of multiple public-private institutions in the Dry Corridor regio

El espacio de las capacidades de adaptación a nivel municipal frente al cambio climático. Serie 2. Análisis local para el Corredor Seco hondureño.

La adaptación al cambio climático a nivel local es un asunto prioridad, especialmente en regiones vulnerables como el corredor seco de Honduras. El desarrollo humano de los municipios del corredor seco configura unos patrones aglomerados de alto y bajo desarrollo. Los cuales han sido persistentes en el tiempo, manteniendo cierta desigualdad entre unos y otros. El indicador de las capacidades de adaptación al cambio climático (CCVA) refleja una importante debilidad en la respuesta municipal al integrar el vector de las variables (educación, infraestructura, gobernanza, etc.). Este desempeño evidencia un espacio regional desigual en el indicador, encontrando aglomeraciones de municipios con alto y bajo CCVA. La multidimensionalidad de la adaptación al cambio climático demanda una intervención nacional y local. Esta última mediante los planes de desarrollo municipal donde se prioricen los aspectos menos valorados en el indicador. Adaptation to climate change at a local level is a priority issue, especially in vulnerable regions such as the Dry Corridor of Honduras. The human development of the municipalities of the Dry Corridor configures agglomerated patterns of high and low development. Which have been persistent over time, maintaining some inequality between them.The indicator of climate change adaptation capacities (CCVA) reflects an important weakness in the municipal response by integrating the vector of the variables (education, infrastructure, governance, etc.). This performance shows an unequal regional space in the indicator, finding agglomerations of municipalities with high and low CCVA. The multidimensionality of adaptation to climate change demands national and local intervention. The latter through municipal development plans that prioritize the aspects less valued in the indicator

Ultrastable lasers based on vibration insensitive cavities

We present two ultra-stable lasers based on two vibration insensitive cavity designs, one with vertical optical axis geometry, the other horizontal. Ultra-stable cavities are constructed with fused silica mirror substrates, shown to decrease the thermal noise limit, in order to improve the frequency stability over previous designs. Vibration sensitivity components measured are equal to or better than 1.5e-11 per m.s^-2 for each spatial direction, which shows significant improvement over previous studies. We have tested the very low dependence on the position of the cavity support points, in order to establish that our designs eliminate the need for fine tuning to achieve extremely low vibration sensitivity. Relative frequency measurements show that at least one of the stabilized lasers has a stability better than 5.6e-16 at 1 second, which is the best result obtained for this length of cavity.Comment: 8 pages 12 figure

Appuyer les organisations de producteurs

Ce guide très accessible et pratique étudie les moyens qui existent pour renforcer les organisations de producteurs et améliorer leur relation avec l'environnement. Déjà nombreuses et actives dans la modernisation de l'agriculture dans le Sud, les organisations de producteurs ont malgré tout du mal à avoir accès à suffisamment d'informations et de ressources pour répondre aux besoins de leurs membres. Illustré de manière utile et présentant de nombreux exemples, ce livre a pour but d'aider le lecteur à poser les bonnes questions pour relever ces défis

Accuracy Evaluation of an Optical Lattice Clock with Bosonic Atoms

We report the first accuracy evaluation of an optical lattice clock based on the 1S0 - 3P0 transition of an alkaline earth boson, namely 88Sr atoms. This transition has been enabled using a static coupling magnetic field. The clock frequency is determined to be 429 228 066 418 009(32) Hz. The isotopic shift between 87Sr and 88Sr is 62 188 135 Hz with fractional uncertainty 5.10^{-7}. We discuss the conditions necessary to reach a clock accuracy of 10^{-17} or less using this scheme.Comment: 3 pages, 4 figures, uses ol.sty fil