241 research outputs found
Metallopolymer Organohydrogels with Photo-Controlled Coordination Crosslinks Work Properly Below 0 degrees C
Light-Switchable Polymer Adhesive Based on Photoinduced Reversible Solid-to-Liquid Transitions
Spatial Optical Solitons due to Multistep Cascading
We introduce a novel class of parametric optical solitons supported
simultaneously by two second-order nonlinear cascading processes,
second-harmonic generation and sum-frequency mixing. We obtain, analytically
and numerically, the solutions for three-wave spatial solitons and show that
the presence of an additional cascading mechanism can change dramatically the
properties and stability of two-wave quadratic solitary waves.Comment: 6 pages, 4 figure
Amorphous crystalline silicon heterojunction solar cells with black silicon texture
Excellent passivation of black silicon surfaces by thin amorphous silicon layers deposited with plasma enhanced chemical vapor deposition is demonstrated. Minority charge carrier lifetimes of 1.3 milliseconds, enabling an implied open circuit voltage of 714 mV, were achieved. The influence of amorphous silicon parasitic epitaxial growth and thickness, as well as of the texture depth is investigated. Furthermore quantum efficiency gains for wavelenghts above 600 ,nm, as compared to random textured solar cells, are demonstrated in 17.2 efficient amorphous crystalline silicon heterojunction solar cells with black silicon textur
Multistep cascading and fourth-harmonic generation
We apply the concept of multistep cascading to the problem of fourth-harmonic
generation in a single quadratic crystal. We analyze a new model of parametric
wave mixing and describe its stationary solutions for two- and three-color
plane waves and spatial solitons. Some applications to the optical frequency
division as well as the realization of the double-phase-matching processes in
engineered QPM structures with phase reversal sequences are also discussed.Comment: 3 pages, 3 figure
Study of the influence between the strength of antibending of working rolls on the widening during hot rolling of thin sheet metal
Based on the variation principle of Jourdan was developed a mathematical model of the process of widening freely in hot rolling of thin sheet metal. The principle applies to rigid-plastic materials and for the cinematically admissible area of speeds. The developed model allows to study the distribution of the widening on the length of the deformation zone depending on the parameters of the rolling process and sheet metal. Results are obtained, characterizing the size of the widening and effectiveness of the process control on tension at the entrance and exit from the stand. The widening is dependent on the strength of anti bending
From macro to mesoporous zno inverse opals; Synthesis, characterization and tracer diffusion properties
Black Silicon with high density and high aspect ratio nanowhiskers
Physical properties of black Silicon (b-Si) formed on Si wafers by reactive
ion etching in chlorine plasma are reported in an attempt to clarify the
formation mechanism and the origin of the observed optical and electrical
phenomena which are promising for a variety of applications. The b-Si
consisting of high density and high aspect ratio sub-micron length whiskers or
pillars with tip diameters of well under 3 nm exhibits strong photoluminescence
(PL) both in visible and infrared, which are interpreted in conjunction with
defects, confinement effects and near band-edge emission. Structural analysis
indicate that the whiskers are all crystalline and encapsulated by a thin Si
oxide layer. Infrared vibrational spectrum of Si-O-Si bondings in terms of
transverse-optic (TO) and longitudinal-optic (LO) phonons indicates that
disorder induced LO-TO optical mode coupling can be an effective tool in
assessing structural quality of the b-Si. The same phonons are likely coupled
to electrons in visible region PL transitions. Field emission properties of
these nanoscopic features are demonstrated indicating the influence of the tip
shape on the emission. Overall properties are discussed in terms of surface
morphology of the nano whiskers
Fabrication of Anticounterfeiting Nanocomposites with Multiple Security Features via Integration of a Photoresponsive Polymer and Upconverting Nanoparticles
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