Mathematical modeling of two-photon thermal fields in laser–solid interaction

In this paper, we have developed an analytical model to study the temperature distributions in IR optical materials heated by laser pulses. Our model takes into account the two-photon absorption (TPA). The calculations are based on a three-dimensional model of heat diffusion in solids using the integral transform method. We find out the rigorous analytical expression of the thermal field when one considers both one- and two-photon absorption. The model is valid for any laser–solid system whose interaction can be described by the generalized Beer–Lambert law. Specific results are presented for an application of the model to ZnSe sample. We find out that TPA can produce detectable temperature variation.     

Squeezed states and uncertainty relations since 1991

A brief review of the history of ten workshops/conferences on “Squeezed States and Uncertainty Relations” and main achievements in the related fields of quantum physics for the period from 1991 to 2007 are presented.     

Classical interaction of the electromagnetic radiation with two-level polarizable matter

The interaction of the classical electromagnetic field with an ensemble of polarizable, identical, atomic particles with two energy levels is investigated, and the coupled non-linear equations of motion for the polarization field and the amplitudes of the level occupancies are solved by a perturbation-theoretical method. A small coupling constant is identified, and the solution is represented as a power series in this coupling constant. Explicit results are given for the leading contributions to the solution. In particular, it is shown that an external electromagnetic field may induce a lasing effect in such an ensemble of particles, by populating the (initially empty) upper level.     

On The Cut-off Parameters in the Bosonization Technique

Jordan's boson representation and cut-off repolarization for the one-dimensional two-fermion model (TFT) is used to get the equivalence of the model with the two-dimensional Coulomb gas and sine-Gordon model. The scaling equations for the coupling constants are thereby obtained up to the third order.     

Electron-microscopy investigations of the damage of aluminium mirrors as a result of repeated powerful microsecond pulsed TEA-CO2 laser irradiation in air

Progressive damage of aluminium mirrors subjected to microsecond pulsed TEA-CO₂ laser irradiation in air, at incident intensity levels lower than the thresholds for melting induction and air breakdown ignition, was evidenced by electron microscopy investigations. A simple model was developed accounting for the results of our experimental studies.     

über die ZuverlÄssigkeit von Systemen ausn-Elementen

Ohne Zusammenfassung     

First- and second-order statistics of optical near fields

The statistical properties of the intensity in close proximity to highly scattering, randomly inhomogeneous media are investigated. Whereas the intensity probability density function obeys the same law irrespective of the distance z from the interface, the second-order intensity correlation length changes for distances smaller than the wavelength. Contrary to predictions of the conventional coherence theory, the corresponding field correlation length can be smaller than the wavelength of light.     

Controlled removal of overpainting and painting layers under the action of UV laser radiation

Laser material removal applied to selective overpaintings and subsequent painting layers detachment was studied in order to select the best cleaning practice of painted artworks. The ablation depth as a function of incident laser fluence/intensity and irradiation pulse number was considered as a reference parameter. We have measured the ablation depth with both a contact microprofilometer and a white light interferometer as a function of laser irradiation parameters. The measurements have evidenced that the ablation depth in our experiments varied between 2 and 100 μm making possible selective removal of painting.     

The vaporization of a metallic target by a microsecond pulsed TE-CO2 laser radiation

The analysis of some new experimental data has proved that the evaporation of a stainless steel target in vacuum under the action of powerful TE-CO₂ microsecond pulsed laser radiation is initiated on the initial spike or not at all. The minimum “tail” duration to get evaporation was deduced as a function of the temporal pulse shape characteristics and the metal thermophysical properties. The vaporisation process was accompanied by nonequilibrium heating of vapour clouds leading to the target surface shielding. Two self-regulated evolutions were recognised which were attributed to the intense vaporisation and the target evaporation by the UV plasma emitted radiation, respectively.     

Opto-acoustic modulator with a nematic liquid crystal

A liquid-crystal optical modulator working with acoustic signals is considered. It is shown that it can be operated also with white light up to frequencies of at least 1 MHz.