Action Of Powerful Laser Pulses Research Articles

Mechanoluminescence and Optically Stimulated Antistokes Luminescence of Composites Based on Epoxy Resin and Strontium Aluminate Phosphors SrAl<sub>2</sub>O<sub>4</sub>:Eu<sup>2+</sup>,Dy<sup>3+</sup> and Sr<sub>4</sub>Al<sub>14</sub>O<sub>25</sub>:Eu<sup>2+</sup>, Dy<sup>3+</sup>

Composite mechanoluminescent materials (composites) based on epoxy resin transparent in the visible range of spectrum and fine-dispersed powders of mechanoluminescent phosphors SrAl2O4:Eu2+, Dy3+ and Sr4Al14O25:Eu2+, Dy3+ were obtained. The mechanoluminescence and photoluminescence spectra of composites under the combined influence of short-wave (λ = 405 nm) and long-wave (λ = 1.06 µm) laser radiation were studied. The attenuation of optically stimulated antistokes luminescence of the composite under the influence of a sequence of pulses of longwave laser radiation was investigated. The composite was pre-irradiated with shortwave laser radiation. The obtained composite was used to visualize heat propagation and thermal deformations in metal plates arising under the action of powerful laser pulses and distribution of deformations under mechanical impact. For this purpose, a thin layer of the composite was applied to the surface of the materials under study. The composite had good adhesion to the surface of the materials and a high yield of mechanoluminescence, which allowed to visualize the distribution of temperature and surface deformations with a good spatial and temporal resolution.

Investigation of propagation dynamics of material deformations caused by laser pulse action

The mechanoluminescent materials attract increasing attention of scientists due to their capability of visualizing the mechanical stresses and deformations experienced by them. The deformations of materials arising under the action of powerful laser pulses were studied. The composite mechanoluminescent materials based on the polymer and phosphor powder were used for visualization and registration of deformation evolution dynamics. The mechanoluminescent materials were deposited on the surface of the materials under study. It has been shown that the spatial distribution of glow intensity of the mechanoluminescent layer and the rate of its change make possible judging the value and rate of material deformation under laser pulses.

On possibility of high-power terahertz emission from target under the action of powerful laser pulses

The possibility of terahertz (THz) emission from a target irradiated by short (∼0.1 ns) high-intensity (I ∼ 1018–1019 W/cm2) laser pulses has been studied by numerical simulations using a relativistic electromagnetic PIC code. The laser pulse action on the target generates plasma and the runaway electrons form a virtual cathode, which oscillates in the intrinsic field of electrons and the field of plasma ions. These oscillations account for the emission of radiation in a THz range. The generation efficiency is about three times as high as that in the absence of ions (according to the conventional reditron mechanism). Explanation of the observed phenomena is proposed.

Nonlinear spectroscopy of photocoloured polytungstic acid nanocomposites

Picosecond absorption spectroscopy was used in an investigation of nonlinear optical processes in nanostructured composites based on polytungstic acid, which were photocoloured by preliminary UV irradiation. The absorption bands responsible for the photocoloration and associated with intervalent charge transfer were bleached by the action of powerful laser pulses. The characteristic monoexponential relaxation time of the process was ~300 ps. The results obtained were analysed taking account of the special features of the splitting of the energy levels of tungsten ions with different degrees of oxidation and of delocalisation of the valence states within separate elements of the polytungstic acid structure.