Multiple filamentation of laser beams with different diameters in the air at a 100-meter path

Results of experiments on controlling the position and length of the filamentation zone of femtosecond laser pulses in atmospheric path length 110 m using different initial spatial focusing and defocusing. The obtained distribution of filaments along the filamentation zone, measured dependence the length of the filamentation zone of the numerical aperture of the beam, its initial radius and pulse power

Global self-focusing and features of multiple filamentation of radiation of a subterawatt Ti:sapphire laser with a centimeter output aperture along a 150-m path

The formation and propagation of postfilamentation channels along a controllable path 150 m long are studied experimentally for collimated beams of different diameters. During multiple filamentation, a laser beam is compressed into a global focus, after passing which its angular divergence is much greater than the divergence of postfilamentation channels generated during the filamentation. It is shown that the intensity of the postfilamentation channels is sufficient for starting multiple filamentation in optical elements at distances much longer than the filamentation region length

Multiple filamentation of laser beams with different diameters in the air at a 150-meter path

Results of experiments on controlling the position and length of the filamentation zone of femtosecond laser pulses in atmospheric path length 150 m using different initial spatial focusing and defocusing. The obtained distribution of filaments along the filamentation zone, measured dependence the length of the filamentation zone of the numerical aperture of the beam, its initial radius and pulse power

Filamentation of terawatt laser pulses along hundred-meter atmospheric paths

Results of the experimental study of filamentation of terawatt femtosecond pulses of a Ti:Sapphire laser along an atmospheric path 106 m long using different spatial focusing and pulse power are presented. The control of filamentation region position and length by means of changing the initial laser beam focusing is shown to be highly effective. Dependencies are derived of filamentation region position and length on the initial degree of focusing, pulse power, and the number of filaments along the filamentation region. The obtained data on the filamentation region length and the number of filaments are compared with the results of our previous experiments and data from other authors

Modeling of multiple filamentation of terawatt laser pulses on a hundred-meter air path

The results of numerical simulation of multiple filamentation of terawatt femtosecond pulse Ti:Sapphire laser performed on the experimental data obtained in the airway of a length of 106 m when changing the initial spatial focusing and laser power

Localized high-intensity light structures during multiple filamentation of Ti:sapphire-laser femtosecond pulses along an air path

The results of experimental studies of the transverse structure of a laser beam after multiple filamentation are presented. A ring structure of radiation is formed around individual filaments in a beam cross section inside the multiple filamentation domain, and at a dozen meters from it a common ring structure starts forming surrounding postfilamentation light channels (PFC). It is shown that the spectra of the PFC, rings, and beam are significantly different. The ring spectrum broadens asymmetrically relative to the carrier wavelength and is mainly concentrated in the short wavelength region. The PFC spectrum has a significant and more symmetrical broadening and covers the range 630–1000 nm

Multiple filamentation of laser pulses in the glass

Results are presented of experiments on investigation of the spatial characteristics of multi-filamentation region of giga- and terawatt pulses of a Ti:sapphire laser in a glass. Dependences are obtained of the coordinate of the beginning of filamentation region, number of filaments, their distribution along the laser beam axis, and length of filaments on the pulse power. It is shown that with increasing radiation power, the number of filaments in the multi-filamentation region decreases, whereas the filament diameter has a quasiconstant value for all powers realized in the experiments. It is shown that as a certain power of the laser pulse with Gauss energy density distribution is reached, the filamentation region acquires the shape of a hollow cone with apex directed toward the radiation source

Filamentation of collimated Ti:sapphire-laser pulses in the glass

The results of experiments to study the spatial characteristics of multiple filamentation gigawatt laser pulses in the glass are presented. It is shown that with increasing pulse power multiple filamentation region increases in length and diameter, the distribution of filaments within the region has a maximum value when the power > 105 Pcr area filamentation takes the form of a hollow cone, the apex directed to the source of the laser radiation

ВЛИЯНИЕ РАЗБАВИТЕЛЕЙ НА КИНЕТИКУ ОБЪЕМНОЙ УСАДКИ И НАПРЯЖЕНИЙ ПРИ ОТВЕРЖДЕНИИ ЭПОКСИДИАНОВЫХ ОЛИГОМЕРОВ

It is known that for decrease in viscosity polymeric binding on the basis of epoxy oligomers in their composition injecting solvents of the different nature and thermodynamic compatibility. In this paper the dependences describing influence on shrinkage, kinetics of increase and maximum level of strains from diluents content and temperature of curing of epoxy oligomers are established. Introduction about 20 % of the active diluents (DEG-1 and SO-3) in system on the basis of epoxy oligomers leads to decrease in viscosity in ~3 times, to improvement of imbibition quality of fibrous fillers, increase of volume contraction (on ~2.5. %) and decrease in residual stresses in ~6 times as a result of increase of mobility of pieces of a polymeric chain in a three-dimensional grid, and also to decrease in glass transition temperature no more than ~20°C.Рассматривается влияние активных и инактивных разбавителей на кинетику объемной усадки и напряжений при отверждении эпоксидиановых олигомеров. Установлены зависимости, описывающие влияние на усадку, кинетику нарастания и максимальный уровень напряжений содержания разбавителей и температуры отверждения эпоксидных олигомеров. Введение до ~20% активных разбавителей (ДЭГ-1 и СО-3) в систему на основе эпоксидных олигомеров приводит к снижению вязкости в ~3 раза, улучшению качества пропитки волокнистых наполнителей, увеличению усадки (на ~2,5.%) и уменьшению остаточных напряжений в ~6 раз в результате увеличения подвижности сегментов полимерной цепи в трехмерной сетке, а также к снижению температуры стеклования не более чем ~20°С

Влияние разбавителей разной природы на кинетику объемной усадки эпоксидиановых олигомеров при отверждении

Diane epoxy oligomers (EO) are the most widespread among epoxies, their production makes more than 70% from the general release. To improve the impregnation of fibrous filler to create a polymer composite material (PCM) to reduce the viscosity of the binder and to that end the low viscosity diluents. This article presents the results of investigation of the influence of the various nature diluents on kinetics and value of the ED-20 brand and the EHD chlorine-containing brand epoxy oligomers final volume shrinkage is surveyed at solidification with the different types of low-viscosity liquid curing agents. Kinetic dependences of volume shrinkage of epoxy oligomer for different types of diluents are received at various concentration and dependence of shrinkage to answering point of jellification and shrinkage to answering point of the beginning of jellification from concentration of diluents. It is established that using active diluents to 20% mass decreases viscosity of the epoxy oligomers, but the kinetics of shrinkage and final shrinkage practically don't change. Introduction of active low-viscid diluents in EHD brand EO to 20 wt.% practically doesn't change kinetics of shrinkage and value of final shrinkage and allows to reduce by 2-4 times viscosity binding that leads to the referred adjustment of technical characteristics polymeric binding and conditions of processing of systems on the basis of EHD. Final heat treatment of samples at an increased temperature practically has no impact on shrinkage, however its carrying out is expedient as it leads the glass transition temperature increase.Ассматривается влияние разбавителей различной природы на кинетику и значение конечной объемной усадки эпоксидных олигомеров марки ЭД-20 и хлорсодержащей марки ЭХД при отверждении. Получены кинетические зависимости объемной усадки эпоксидных олигомеров для активных и неактивных разбавителей при различных концентрациях. Установлено, что при использовании активных разбавителей до 20% мас. снижается вязкость эпоксидного связующего как на основе ЭО марки ЭД-20, так и на ЭО марки ЭХД, а кинетика усадки и конечная усадка практически не изменяются