Monolithic master oscillator power amplifier at 1.58 µm for lidar measurements

Nowadays the interest in high power semiconductor devices is growing for applications such as telemetry, lidar system or free space communications. Indeed semiconductor devices can be an alternative to solid state lasers because they are more compact and less power consuming. These characteristics are very important for constrained and/or low power supply environment such as airplanes or satellites. Lots of work has been done in the 800-1200 nm range for integrated and free space Master Oscillator Power Amplifier (MOPA) [1]-[3]. At 1.5 ?m, the only commercially available MOPA is from QPC [4]: the fibred output power is about 700 mW and the optical linewidth is 500 kHz. In this paper, we first report on the simulations we have done to determine the appropriate vertical structure and architecture for a good MOPA at 1.58 ?m (section II). Then we describe the fabrication of the devices (section III). Finally we report on the optical and electrical measurements we have done for various devices (section IV).

Do pingers cause stress in fish? An experimental tank study with European sardine, Sardina pilchardus (Walbaum, 1792) (Actinopterygii, Clupeidae), exposed to a 70 kHz dolphin pinger

Date of acceptance: 06/12/2014 Acknowledgments The study was funded by the Portuguese Ministry of Science (Fundac¸a˜o para a Cieˆncia e Tecnologia– FCT) through a PhD Grant of SG (SFRH/BD/47931/2008). We would like to thank the captain of the purse-seiner (Jose´ Manuel Saveedra) and his crew for facilitating the capture and transport of live fish. Moreover, we want to thank Ana Marc¸alo for suggestions on the experimental design, Manuel Garci for technical advice on underwater video recordings and James Turner from the company Future Oceans for providing technical details on the 70 kHz dolphin pingers. We would also like to acknowledge the scientific advice of Dr. Jose´ Iglesias and the technical and logistic support for the preparation of the laboratory and the materials for tank experiments by Enrique Martı´nez Gonza´lez, Ricardo Pazo´and other staff at the aquaculture facilities of the Spanish Institute for Oceanography (IEO) and the Marine Sciences Station of Toralla (ECIMAT) in Vigo. Furthermore, we are grateful to Francisco de la Granda Grandoso for his practical assistance during the fish tank experiments and to Juan Santos Blanco for helping with statistical analysis. Finally, we would like to thank Pilar Riobo´ Agula, Amelia Fernandez Villamarin, Jose´ Franco Soler, Jose´ Luis Mun˜oz, Angela Benedetti, Marcos Antonio Lopez Patin˜o and Marta Conde Sieira for scientific advice and practical support with cortisol analysis and Rosana Rodrı´guez for preparing histological samples for us.

The hydration of paper studied with solid-state magnetisation-exchange H-1 NMR spectroscopy

The wide-line H-1 nuclear magnetic resonance (NMR) spectrum of paper in equilibrium with ambient humidity consists of super-imposed relatively broad and narrow lines. The narrower line is of the order of 2 kHz wide at half the maximum height, while the broader line is of the order of 40 kHz in width at half height. On the basis of these line widths, the narrow line is assigned to water sorbed to the paper, and the broad line to the polymeric constituents of the paper. It was not possible to distinguish between the various polymeric components of paper contributing to the H-1 NMR spectra. A modified Goldman-Shen pulse sequence was used to generate a spatial magnetisation gradient between the polymer and water phases. The exchange of magnetisation between protons associated with water and those associated with the macromolecules in paper was observed. The exchange of magnetisation is discussed within a heat transfer model for homonuclear dipolar coupling, with exchange being characterised by a spin-diffusion coefficient. Consideration of the magnitude of the initial rate of the exchange process and estimates of the spin-spin relaxation times based on H-1 line widths indicate that some water must exist in a sufficiently immobile state as to allow homonuclear dipolar interactions between adjacent polymer and water protons. Thus, water sorbed onto paper must exist in at least two states in mass exchange with each other. This observation allows certain conclusions to be drawn about the ratio of free/bound water as a function of moisture content and the dispersal of water within the polymer matrix.