Regenerative similariton laser

Self-pulsating lasers based on cascaded reshaping and reamplification (2R) are capable of initiating ultrashort pulses despite the accumulation of large amounts of nonlinearities in all-fiber resonators. The spectral properties of pulses in self-similar propagation are compatible with cascaded 2R regeneration by offset filtering, making parabolic pulses suitable for the design of a laser of this recently introduced class. A new type of regenerative laser giving birth to similaritons is numerically investigated and shows that this laser is the analog of regenerative sources based solely on self-phase modulation and offset filtering. The regenerative similariton laser does not suffer from instabilities due to excessive nonlinearities and enables ultrashort pulse generation in a simple cavity configuration. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)

1.3 Octave Supercontinuum Generation in Highly Ge-doped Photonic Crystal Fiber

We present a flat, visible 1.3-octave supercontinuum generated in a GeO2-doped photonic crystal fiber owing to an overlap of the modulation instability and Raman gain regions resulting in efficient energy transfer to new frequency component

Mid-infrared supercontinuum generation in a SiN waveguide pumped at 1.55 micron

We report supercontinuum generation extending to 3.6 micron in silicon-nitride waveguides pumped by a commercial source at 1.55 micron. The span is a bandwidth record for the platform and demonstrates its potential as mid-infrared source

CESA5 Is Required for the Synthesis of Cellulose with a Role in Structuring the Adherent Mucilage of Arabidopsis Seeds

Imbibed Arabidopsis (Arabidopsis thaliana) seeds are encapsulated by mucilage that is formed of hydrated polysaccharides released from seed coat epidermal cells. The mucilage is structured with water-soluble and adherent layers, with cellulose present uniquely in an inner domain of the latter. Using a reverse-genetic approach to identify the cellulose synthases (CESAs) that produce mucilage cellulose, cesa5 mutants were shown to be required for the correct formation of these layers. Expression of CESA5 in the seed coat was specific to epidermal cells and coincided with the accumulation of mucilage polysaccharides in their apoplast. Analysis of sugar composition showed that although total sugar composition or amounts were unchanged, their partition between layers was different in the mutant, with redistribution from adherent to water-soluble mucilage. The macromolecular characteristics of the water-soluble mucilage were also modified. In accordance with a role for CESA5 in mucilage cellulose synthesis, crystalline cellulose contents were reduced in mutant seeds and birefringent microfibrils were absent from adherent mucilage. Although the mucilage-modified5 mutant showed similar defects to cesa5 in the distribution of sugar components between water-soluble and adherent mucilage, labeling of residual adherent mucilage indicated that cesa5 contained less cellulose and less pectin methyl esterification. Together, the results demonstrate that CESA5 plays a major and essential role in cellulose production in seed mucilage, which is critical for the establishment of mucilage structured in layers and domains

Broadband self-pulsating sources based on nonlinear effects

In this thesis, three architectures of self-pulsating erbium laser sources are studied. Through experimental and numerical investigations, the generation of ultrashort and broadband pulses is enabled. In a first phase, a numerical analysis assesses the pulse ignition and steady-state operation of self-pulsating sources composed of self-phase modulation spectral broadening andoffset filtering regenerators in closed loop. An experimental setup results from the conclusions of this analysis, and a multiwavelength source generating aperiodic light pulses in the range of the picosecond is presented. In a second phase, a new kind of self-pulsating source based on optical regeneration as well as soliton self-frequency shift is introduced. Via a numerical analysis as well as direct measurements, the role of modulation instability in the generation of femtosecond pulses is highlighted. This laser emits bursts of stochastic pulses at the repetition rate of the cavity, and results on the average in a flat supercontinuum, spreading beyond 1900 nm. Finally, the emission of pulses in the noiselike regime is studied in two different cavities. Via nonlinear polarization rotation, pulses spreading over tens of nanometers are generated. By means of stimulated Raman scattering, the production of noise pulses is demonstrated in the U-band (1625 nm to 1675 nm) and beyond. The bandwidth of such pulses spreads over 84 nm, from 1616 nm to 1700 nm. These three sources find applications in low-coherence interferometry for imagery, or the characterization of components. LIDAR applications for aerosols or distance measurements, as well as spectroscopy for the detection of chemicals are enabled by such lasers.Dans cette thèse, trois architectures de sources laser erbium auto-pulsantes et large bande sont étudiées. Au travers de ces architectures simulées et réalisées expérimentalement, la génération d'impulsions ultra courtes et large bande est rendue possible. Dans un premier temps, une analyse numérique s'intéresse au démarrage et au fonctionnement de sources auto-pulsantes composées de régénérateurs à étalement spectral par auto-modulation de phase et filtrage décalé, dans une configuration en boucle fermée. Un montage expérimental découle des conclusions de ces simulations, et une source multi-longueurs d'onde générant des impulsions apériodiques de l'ordre de la picoseconde est présentée. Dans un second temps, une nouvelle sorte de source auto-pulsante basée sur la régénération optique ainsi que l'auto-décalage fréquentiel de soliton est présentée. Par une analyse numérique ainsi que des mesures directes, le rôle de l'instabilité de modulationdans la génération des impulsions femtosecondes est mis en évidence. Ce laser émet des séquences d'impulsions stochastiques au taux de répétition de la cavité, et dispose en moyenne d'un continuum plat s'étendant au delà de 1900 nm. Finalement, l'émission d'impulsions en mode "noiselike" est étudié au travers de deux cavités. Via la rotation nonlinéaire de polarisation, des impulsions s'étendant sur plusieurs dizaines de nanomètres sont générées. Grâce à l'effet Raman stimulé, la production d'impulsions de bruit dans la bande U (1625 nm – 1675 nm) et au delà est démontrée. La bande passante de ces dernières peut s'étendre sur 84 nm, entre 1616 nm et 1700 nm. Ces trois sources trouvent des applications en interférométrie à faible cohérence pour l'imagerie ou la caractérisation de composants, pour l'estimation de distances ou aérosols dans les applications LIDAR, ainsi que pour la détection d'éléments chimiques

Compact and high-brightness helmet-mounted head-up display system by retinal laser projection

A compact binocular heads-up display integrated in a motorcycle helmet is presented and characterized. The use of a laser micro-projector using a 2D MEMS-mirror enables the formation of a bright image, superimposed on the user vision. A fully-functional and adjustable 3D-printed prototype, thereby fitting the morphology of most users, is presented

Lightweight high-brightness helmet-mounted head-up display system

We present a compact binocular head-up display for integration in a motorcycle helmet. A 2D MEMS-mirror reflecting laser beams enables the formation of a bright image superimposed on the user vision by means of retinal scanning. A 3d-printed prototype including the required optical components is presented and characterized. It fits the morphology of most users thanks to several degrees of freedom accessible to the user for fine-tuning

Aluminium coordination complexes in copolymerization reactions of carbon dioxide and epoxides

Al complexes are widely used in a range of polymerization reactions (ROP of cyclic esters and cationic polymerization of alkenes). Since the discovery in 1978 that an Al porphyrin complex could copolymerize propylene oxide with carbon dioxide, Al coordination compounds have been studied extensively as catalysts for epoxide-carbon dioxide copolymerizations. The most widely studied catalysts are Al porphyrin and Al salen derivatives. This is partially due to their ability to act as mechanistic models for more reactive, paramagnetic Cr catalysts. However, this in depth mechanistic understanding could be employed to design more active Al catalysts themselves, which would be beneficial given the wide availability of this metal. Polymerization data (% CO3 linkages, Mn, Mw/Mn and TON) for these complexes are presented and mechanisms discussed. In most cases, especially those employing square-based pyramidal Al complexes, co-catalysts are required to obtain high levels of carbon dioxide incorporation. However, in some cases, the use of co-catalysts inhibits the copolymerization reaction. Lewis acidic Al phenolate complexes have been used as activators in CHO-carbon dioxide copolymerizations to increase TOF and this has recently led to the development of asymmetric copolymerization reactions. Given the ready availability of Al, the robustness of many complexes (e.g. use in immortal polymerizations) and opportunity to prepare block copolymers and other designer materials, Al complexes for copolymerization of carbon dioxide are surely worth a second look