Optical-acoustic effect in laser optics investigations

Parameters of the acoustic signals (AS) excited in the massive Al, Be and Cu mirrors by TEA CO2- and Nd : glass-laser pulses were investigated. Correlations between the AS parameters and an emergence of different types of laser-induced damage such as evaporation of heat insulated defects, melting and optical breakdown off irradiated surface have been found. The possibility to make a nondisturbing prediction of the metal mirror resistance to laser-induced damage has been shown

Optical-acoustic effect in laser optics investigations

Parameters of the acoustic signals (AS) excited in the massive Al, Be and Cu mirrors by TEA CO2- and Nd : glass-laser pulses were investigated. Correlations between the AS parameters and an emergence of different types of laser-induced damage such as evaporation of heat insulated defects, melting and optical breakdown off irradiated surface have been found. The possibility to make a nondisturbing prediction of the metal mirror resistance to laser-induced damage has been shown.Les paramètres des signaux acoustiques générés par des impulsions de lasers TEA-CO2 et Nd-glass dans des miroirs massifs en Al, Be et Cu ont été étudiés. Nous avons trouvé des corrélations entre les signaux acoustiques et l'apparition de dommages variés induits par laser tels que l'évaporation de défauts isolés thermiquement, la fusion et le breakdown optique des surfaces illuminées. La possibilité de faire une prédiction non destructive de la résistance de miroirs métalliques à l'endommagement laser est démontrée

Structure, optical and spectral characteristics of epicuticular wax of blue spruce needles

A method for separating clean plates of epicuticular wax has been proposed. The use of water, which can penetrate deeply into wax structures under the influence of van der Waals forces and expand upon freezing, allows to quickly obtain uncontaminated wax plates with a native structure without any third-party chemical impurities. Using scanning electron microscopy, images of blue spruce (Picea pungens Engelm.) needle wax were obtained. Its morphological and structural characteristics have been determined. A distinctive feature is the presence of wax nanotubules with a characteristic diameter of ~150 nm and a length of 3–5 μm. Nanotubes lie on top of each other in stacks, forming a one-dimensional long-period lattice. Microscopic observations of the wax were made in reflected and transmitted light. It has been shown that the coating of blue spruce needles consists of microparticles of wax with a structural color. In a wide spectral range, individual particles change color from blue to red, as a result, large conglomerates of particles are white. Fluorescence spectra of needles with native wax cover and the same needles after wax removal were obtained. When comparing the width of fluorescence lines at half-height of blue spruce needles with and without wax, the influence of the wax layer on the lifetime of excited electrons in photosystem II was revealed, thereby establishing a connection between the wax cover and the process of photosynthesis. Using the matrix transfer method, transmission spectra were calculated for a lattice similar to a waxy structure, a chloroplast, and a combination of a waxy structure with a chloroplast. In the latter version, the long-wave zone of selective reflection is much wider than in individual cases. When examining a structure containing a chloroplast and epicuticular wax, there is a slight splitting of the stop zone, as if there were a defect, which contributes to a high concentration of energy at the site of splitting. Due to an increase in energy concentration, the density of photonic states at the corresponding wavelengths increases. This effect is important for photosynthesis because, according to Fermi’s golden rule, the rate of reaction is proportional to the density of photonic states. The calculation results are in good agreement with the experimental spectra