Monitoring of microplasma formation and filamentation of tightly focused femtosecond laser pulses in dielectrics

Abstract not reproduced here by request of the publisher. The text is available from http://dx.doi.org/10.1117/12.80885

Frequency conversion of mode-locked and Q-switched CO laser radiation with efficiency up to 37%

Frequency conversion of CO laser radiation was experimentally studied in ZnGeP2 and GaSe nonlinear crystals. T

Frequency conversion of mode-locked and Q-switched CO laser radiation with efficiency up to 37%

Frequency conversion of CO laser radiation was experimentally studied in ZnGeP2 and GaSe nonlinear crystals. T

FORMALISMS, ANALYSIS, RESULTS AND ACCOMPLISHMENTS WITH POPULATION INVERSION OF MATERIALS

During six decades of quantum electronics, a vast majority of new types of quantum generators have been developed. Although the principle of population inversion has united different ranges of electromagnetic spectra (and respective quantum generators), the existence of the title laser without the population inversion, makes that the exception had confirmed the rule, i. e. that this title deserves to be discussed further. Developing of formalisms describing the operation of quantum generators, by now have produced several approaches, which must have a quantum mechanics base. For the practical reasons, negative coefficient of absorption is acquired using classic electromagnetics as well, however for the population purposes, quantum representation must be entered.A few levels of formalisms will be set in this paper, linked to quantum generators accenting the optical portion of the spectra. The lowest level descriptions are based on lumped circuits. This could be expanded to equivalents of other physical problems, using program packages developed for the electrical engineering application purposes (Spice, etc.). Schematics are defined at the macro as well as micro equivalent levels (atomic – electronic levels). The kinetic equations with simpler approach will be considered as well as simplified laser equations based on quantum/ semi-quantum approach. The use of Fourier analysis or other appropriate transformations leads to formulating the main five laser equations which serve as the base for various working regimes of quantum generators and amplifiers (free generation regime, Q switch, synchronization, operation with filters, two modes regime, regime with losses, etc.). The Lyapunov stability theorem has to be included here, etc.For some of the chosen types of quantum generator, analytical modeling will be analyzed as well as the results of program packages developed for the lasers dynamics, regimes and parameters. The systems pumped with electronic beams (relativistic) will be considered and the nuclear physics statements discussed which must be included at the beginning, in order to consider further necessary parts of the condensed – solid state theory and laser techniques, after slowing down towards thermal energies.Existing program packages provide fast modeling and visualization of laser energy distribution, temperature, modes, etc. in active material with or without the resonator. A modeling will be performed for the specified geometries and a temperature distribution in active material will be captured during operation of a chosen laser system. Different pump geometries will be compared. Contemporary lasers with the shortest existing pulse durations demand new formalisms. Areas of nonlinear optics and quantum electrody-namics, Glauber states and similar, are areas that have to be included. Two main formalisms thermodynamical and quantum mechanical with transition probabilities using perturbation methods and secondary quantization naturally had to be complemented if the Brillouin, Raman, Compton, soliton, fiber and other lasers are included more generally

Laser Interaction With Some Metalic and Ceramic Materials

The interactions with CO laser, ruby and Nd:Yag lasers on some metallic, composite and ceramic materials are made. Metallic samples of coldly pressed iron and BiFeO3, were used, synthesized in the respective laboratory conditions. For iron cold consolidation, the Fe powder with average size - 63μm was used with the pressing pressure of 0.5 to 1.0 GPa, the consolidation samples reaching the density from 75% to 85% of theoretically predicted value. BiFeO3 samples were synthesized by the method that in the simplest manner ensures production of relatively pure BiFeO3 phase. The previous grinding of equimolar quantities of initial oxides in the conditions of high mass relation of dense BiFeO3 sample, through the reaction sintering at the temperature considerably lower than the temperature where larger evaporation of Bi-oxide occurs and a partial forming of the phase with Fe oxide. Beside the well known types for the material processing (ruby, Nd:YAG, Co2), the CO laser with the controlled electron beam EBCD laser was used for researches with cryogen cooled installation of active volume 1dm3. Besides those as representative materials we present some other metallic and ceramic materials, including the problems and predicted tasks that involve them

Modification of Arabinogalactan Isolated from Larix sibirica Ledeb. into Sulfated Derivatives with the Controlled Molecular Weights

The process of sulfation of arabinogalactan—a natural polysaccharide from Larix sibirica Ledeb.—with sulfamic acid in 1,4-dioxane using different activators has been studied for the first time. The dynamics of the molecular weight of sulfated arabinogalactan upon variation in the temperature and time of sulfation of arabinogalactan with sulfamic acid in 1,4-dioxane has been investigated. It has been found that, as the sulfation time increases from 10 to 90 min, the molecular weights of the reaction products grow due to the introduction of sulfate groups without significant destruction of the initial polymer and sulfation products. Sulfation at 95 °C for 20 min yields the products with a higher molecular weight than in the case of sulfation at 85 °C, which is related to an increase in the sulfation rate; however, during the further process occurring under these conditions, sulfation is accompanied by the destruction and the molecular weight of the sulfated polymer decreases. The numerical optimization of arabinogalactan sulfation process has been performed. It has been shown that the optimal parameters for obtaining a product with a high sulfur content are a sulfamic acid amount of 20 mmol per 1 g of arabinogalactan, a process temperature of 85 °C, and a process time of 2.5 h