Optimal non-circular fiber geometries for image scrambling in high-resolution spectrographs

Optical fibers are a key component for high-resolution spectrographs to attain high precision in radial velocity measurements. We present a custom fiber with a novel core geometry - a 'D'-shape. From a theoretical standpoint, such a fiber should provide superior scrambling and modal noise mitigation, since unlike the commonly used circular and polygonal fiber cross sections, it shows chaotic scrambling. We report on the fabrication process of a test fiber and compare the optical properties, scrambling performance, and modal noise behavior of the D-fiber with those of common polygonal fibers.Comment: 7 pages, 6 figures, submitted to SPIE Astronomical Telescopes & Instrumentation 2016 (9912-192

LASER EFFICACE A FIBRE DOPEE THULIUM SYNTHETISEE PAR FRITTAGE ET VITRIFICATION DE POUDRES DOPEES

National audienceUn laser à fibre dopée thulium a été réalisé à partir d'une fibre synthétisée par une méthode alternative nommée Repusil. Ce laser présente une très bonne qualité de faisceau émis proche de la limite de diffraction et une pente d'efficacité de 43% pour une concentration en ions Tm 3+ de 0,93 poids% validant le procédé de fabrication. Une puissance laser de 9W a été obtenue, valeur limitée par la puissance de la diode de pompe

Micro-fluorescene lifetime and spectral imaging of ytterbium doped laser materials

We present the application of a confocal fluorescence microscope to the analysis of Yb-doped solid-state laser materials, with examples of Yb-doped crystals, photonic crystal fibers and fiber preforms made with different manufacturing processes. Beside the fluorescence lifetime image itself, a microscopic spectral fluorescence emission analysis is presented and spatially resolved emission cross sections are obtained. Doping concentration and its distributions and other laser optical parameters are measured, which help to analyze manufacturing steps. Further properties like photodarkening and saturation are addressed

Mode-resolved gain analysis and lasing in multi-supermode multi-core fiber laser

Multi-core fibers (MCFs) with coupled-cores are attractive large-mode area (LMA) specialty fiber designs that support the propagation of a few transverse modes often called supermodes (SMs). Compared to other LMA fibers, the uniqueness of MCF arises from the higher degrees of design space offered by a multitude of core-array geometries, resulting in extended flexibility to tailor SM properties. To date, the use of MCF as gain media has focused on lasers that operate in only one selected SM, typically the lowest order in-phase SM, which considerably limited the potential of these multi-core structures. Here, we expand the potential of MCF lasers by investigating multi-SM amplification and lasing schemes. Amplifier and laser systems using a 7 coupled-cores Yb-doped MCF as gain medium were successfully designed and assembled. Individual SM could be decomposed using the correlation filter technique mode analysis and the modal amplification factors (gamma(i)) were recorded. With access to amplification characteristics of individual transverse modes, a monolithic MCF laser was demonstrated that operates simultaneously on the two SMs carrying the highest optical gain

LASER THULIUM EFFICACE BASE SUR UNE FIBRE A GRANDE AIRE MODALE A TRIPLE GAINE FABRIQUEE PAR LA METHODE REPUSIL

National audienceNous rapportons ici une fibre à large aire modale de 18 µm de diamètre de coeur dopée thulium fabriquée par un procédé alternatif nommé Repusil et présentant un profil à triple gaine. Cette fibre, caractérisée en configuration laser, nous a permis d'obtenir un faisceau monomode transverse proche de la limite de diffraction (M x,y 2 < 1,1) avec une efficacité laser de 50,4%

All-solid aperiodic Large Pitch Fibers for operation in high power regime

International audienceThis communication intends to summarize the recent strides carried out by the study of original Very Large Mode Area fibers (VLMA) that offer remarkable beam qualities. This work also aims in pushing farther the threshold of appearance for non-linear processes as well as thermal induced beam degradation hindering the power scaling in optical fibers. So as to fulfil this objective, thorough investigations of fibers modal content has been performed, leading to the evidencing of primordial statements for exacerbation of the beam quality and its robustness. Theoretical principles driven toward the conception of aperiodic Large Pitch Fibers (LPFs) will be reported together with experimental validation into passive fiber designs. The relevance of these original structures will then been discussed in regard to the power scaling

New solid fully-aperiodic large pitch fibers with non-filamented core for high-power singlemode emission

International audienceWe report on the first high power laser emission of a solid triple-clad fully-aperiodic large mode area fiber with non-filamented core based on Repusil process. The average power is 184 W with a singlemode fashion

Ultra large mode area fibers with aperiodic cladding structure for high power single mode lasers

International audienceThis communication presents the latest designs, fabrication steps and first results of large mode area fibres with aperiodic cladding structure for high power singlemode emission. Pre-compensation of thermal loading and first laser emission are detailed

Fiber Fabry-Perot interferometer for curvature sensing

A curvature sensor based on an Fabry-Perot (FP) interferometer was proposed. A capillary silica tube was fusion spliced between two single mode fibers, producing an FP cavity. Two FP sensors with different cavity lengths were developed and subjected to curvature and temperature. The FP sensor with longer cavity showed three distinct operating regions for the curvature measurement. Namely, a linear response was shown for an intermediate curvature radius range, presenting a maximum sensitivity of 68.52 pm/m-1. When subjected to temperature, the sensing head produced a similar response for different curvature radii, with a sensitivity varying from 0.84 pm/°C to 0.89 pm/°C, which resulted in a small cross-sensitivity to temperature when the FP sensor was subjected to curvature. The FP cavity with shorter length presented low sensitivity to curvature