Threshold Laws for the Break-up of Atomic Particles into Several Charged Fragments

The processes with three or more charged particles in the final state exhibit particular threshold behavior, as inferred by the famous Wannier law for (2e + ion) system. We formulate a general solution which determines the threshold behavior of the cross section for multiple fragmentation. Applications to several systems of particular importance with three, four and five leptons (electrons and positrons) in the field of charged core; and two pairs of identical particles with opposite charges are presented. New threshold exponents for these systems are predicted, while some previously suggested threshold laws are revised.Comment: 40 pages, Revtex, scheduled for the July issue of Phys.Rev.A (1998

Theoretical study of ionization of an alkali atom adsorbed on a metal surface by laser assisted subfemtosecond pulse

The first numerical simulation of the process of ionization of an atom adsorbed on a metal surface by the subfemtosecond pulse is presented. The streaking scheme is considered, when a weak sub-femtosecond pulse comes together with a strong IR pulse with a variable delay between them. The problem is analyzed with numerical solving the non-stationary Schroedinger equation in the cylindrical coordinate. The results obtained are compared with ones in the gas phase. We show that the surface influences the DDCS, but the observation of this influence, beside the trivial polarization shift of the energy of the initial state, requires a quite high experimental resolution

Ultrafast Laser Nanostructured ITO Acts as Liquid Crystal Alignment Layer and Higher Transparency Electrode

Electrodes with higher transparency that can also align liquid crystals (LCs) are of high importance for improved costs and energy consumption of LC displays. Here we demonstrate for the first time alignment of liquid crystals on femtosecond laser nanostructured indium tin oxide (ITO) coated glass exhibiting also higher transparency due to the less interface reflections. The nano paterns were created by fs laser directlly on ITO films without any additional spin coating materials or lithography procces. Nine regions of laser-induced nanostructures were fabricated with different alignment orientations and various pulse energy levels on top of the ITO. The device interfacial anchoring energy was found to be comparable to the anchoring energy of nematic LC on photosensitive polymers. The device exhibits contrast of 30:1 and relaxation time of 330ms expected for thick LC devices. The measured transparency of the LC device with two ITO nanograting substrates is 10% higher than the uniform ITO film based LC devices. The alignment methodology presented here paves the way for improved LC displays and new structured LC photonic devices

Femtosecond laser nanostructuring of transparent materials: from bulk to fiber lasers

Progress in high power ultra-short pulse lasers has opened new frontiers in the physics of light-matter interactions and laser material processing. Recently there has been considerable interest in the application of femtosecond lasers to writing inside transparent materials and in particular to fabrication of three-dimensional microstructures

Self-assembled nanostructuring of a-Si:H films with ultrashort light pulses

For several decades, hydrogenated amorphous silicon (a-Si:H) has been playing a significant role in the world's production of photovoltaic modules. In this work, we investigate different types of modifications induced by a femtosecond laser in a-Si:H thin films. We demonstrate that several distinctive modification regimes with peculiar optical properties can be obtained in a narrow range of the laser pulse energies

SnO₂ nanoparticles in silica: nanosized tools for femtosecond-laser machining of refractive index patterns

We show that SnO2 nanoclusters in silica interact with ultrashort infrared laser pulses focused inside the material generating a hydrostatic compression and photoelastic response of the surrounding glass. This effect, together with the laser-induced nanocluster amorphization, gives rise to positive or negative refractive-index changes, up to 10–2, depending on the beam-power density. This result points out a wide tuning of the refractive index patterns obtainable in silica-based optical technology