Thanh Nam Nguyen

Fourth-order cascaded Raman shift in AsSe chalcogenide suspended-core fiber pumped at 2 μm

Cascaded Raman wavelength shifting up to the fourth order ranging from 2092 to 2450 nm is demonstrated using a nanosecond pump at 1995 nm in a low-loss As(38)Se(62) suspended-core microstructured fiber. These four Stokes shifts are obtained with a low peak power of 11 W, and only 3 W are required to obtain three shifts. The Raman gain coefficient for the fiber is estimated to (1.6±0.5)×10(-11) m/W at 1995 nm. The positions and the amplitudes of the Raman peaks are well reproduced by the numerical simulations of the nonlinear propagation.

High order FE derivatives versus geometric parameters. Implantation on an existing code

In this paper, the authors present the design of a high order sensitivity analysis that is realised in an existing large FE code. They are interested in the implantation in that respect as much as possible of the original FE program structure and the existing classical tools. The goal is then to obtain the Taylors development of solution (and of all basic entities) that reports to the sensitivity parameters. The mesh derivation module and the parametrized FE solving stage are the two main design steps here. Many tools have been introduced for accelerating the expensive parametrized calculus. Once the parametrized solution is established, the rapidity of its evaluation could increase the utility of FE analysis and allows to realise some new applications. For one of those possibilities, they propose here a procedure that will allow one to define the device equivalent model from the results of parametrized analysis.

A study on nano-wear at laser-textured bump tips and the failure mechanism at the head-bump-interface

The disk laser-texture technique has been developed to provide a more controllable head-bump-interface (HBI) for low stiction and low glide. However, this new interface also introduced some new tribology issues, such as the possibility of more catastrophic failures at the HBT. This paper presents a study on nano-scaled sliding wear and fatigue wear on crater-type laser-bumps. To understand the failure mechanism, the cyclic loading-unloading, impacts, and stress during CSS cycles were analyzed for bumps having different rim-sizes (2-14 /spl mu/m) and densities (spacing 10-100 /spl mu/m). Stress wear tests using altitude chambers and CSS tests were conducted for bump-size 5-15 /spl mu/m and bump-spacing 20-60 /spl mu/m to further examine the HBI wear behavior. The experimental results agreed with the analytical study on the bump design safe regime for minimum wear failure.

Recent advances in the development of holey optical fibers based on sulphide glasses

Microstructured optical fibers as new optical objects have been developed in the recent past years, firstly from silica glass and then from other oxide glasses such as tellurite or different heavy cations oxide glasses. However very few results have been reported concerning non-oxide glasses and more particularly chalcogenide glasses. In a photonic crystal fiber the arrangement of air holes along the transverse section of the fiber around a solid glassy core leads to unique optical properties, such as for example broadband single-mode guidance, adjustable dispersion, nonlinear properties. Since the effective modal area is adjustable thanks to geometrical parameters, chalcogenide microstructured fibers with small mode area are of interest for nonlinear components because of the intrinsic non linearity of chalcogenide glasses, several order of magnitude above these of the reference silica glass (100 to 1000 times the non linearity of silica glass). On the other hand, chalcogenide holey fibers with large mode area are of interest for infrared power transmission, in a wavelength range out of reach of silica fibers, and more particularly in the 3-5 μm atmospheric window. The aim of this paper is to present more specifically the recent results that have been achieved in the elaboration, light guidance and characterization of photonic crystal fibers from the sulfide Ge20Ga5Sb10S65 glass, which presents a large transparency window from 600 nm to 11 μm.

Effect of isotropic sub-micron crystallized texture of glass-ceramic disks on low glide, stiction, and CSS

Near contact recording requires smoother surfaces with ultra-low Ra. Thus, micro-texture features at asperity-level which affect the overall tribological performance should be described by more surface parameters and/or their combinations instead of only those roughness height-dependent parameters. Our studies on sub-micron crystallized glass-ceramic disks indicate that the glide height avalanche for isotropic surfaces decreases with reductions in most parameters related to asperity height and profile shape, but it varies inversely with asperity spacing-related parameters. With proper combination of profile shape and spacing features, low stiction in 1-rpm and CSS tests on low Ra glass-ceramic disks can be achieved over larger ranges of roughness and lubricant thickness compared to cross-hatch textured NiP/Al disks.