Intensity Distribution Of Laser Radiation Research Articles

Experimental study of the filamentation phenomenon and measurement of filaments parameters

The article experimentally investigated the phenomenon of filamentation in the propagation of femtosecond laser radiation in transparent solid media. The experimental scheme for measuring the parameters of filaments using spherical and cylindrical optics was developed and assembled. A series of experiments on the spatial ordering of filaments was carried out. The sample was structured in the filamentation mode with a predetermined distribution of laser radiation intensity. The spatial redistribution of laser radiation passing through the formed structures in the quartz glass sample is also investigated.

Study of the Filamentation Phenomenon of Femtosecond Laser Radiation

The filamentation phenomenon during propagation of femtosecond laser radiation in transparent solid media is experimentally studied. An experimental scheme for measuring the filament parameters using spherical and cylindrical optics is developed and assembled. The sample is structured in the filamentation mode, which makes it possible to obtain a specified distribution of laser radiation intensity.

The Influence of Laser Plasma on Spatial-time Distribution of High-power Laser Radiation Intensity

Spatial distribution of laser radiation intensity can be changed during the process of interaction with plasma or another substance with low density. This effect may occur due to spatial laser plasma inhomogeneity. For such investigations powerful laser was used. The energy of laser pulse is about 28J.

Visualization of the simulation results for multi-dimensional interaction of laser radiation with a photonic crystal

The article describes a software interface for the visualization of multidimensional time-dependent intensity distribution of laser radiation propagating in a photonic crystal. The intensity distribution is displayed in a three-dimensional space in color, which makes it possible to model the fourth dimension. The program constructs different sections of the intensity distribution, charts the evolution of the surface with a given intensity increment, and writes avi files. It allows viewing selected regions with different levels of detail and if necessary interpolates the computation results to achieve the required smoothness of the intensity distribution. The software has been validated and tested for the problem of transmission of laser radiation through a photonic crystal formed by polymer-filled spheres.

Extension of the possibilities of a commercial digital camera in detecting spatial intensity distribution of laser radiation

Performance capabilities of commercial digital cameras are demonstrated by the example of a Canon EOS 400D camera in measuring and detecting spatial distributions of laser radiation intensity. It is shown that software extraction of linear data expands the linear dynamic range of the camera by a factor greater than 10, up to 58 dB. Basic measurement characteristics of the camera are obtained in the regime of linear data extraction: the radiometric function, deviation from linearity, dynamic range, temporal and spatial noises (both dark and those depending on the signal value). The parameters obtained correspond to those of technical measuring cameras.

Peculiarities of the angular distribution of laser radiation intensity scattered by laser-spark plasma in air

The spatiotemporal study of the diagram of laser radiation scattering by the laser-spark plasma produced by 3-ns and 50-ns pulses is performed. It is shown that radiation appearing outside the laser beam cone is scattered during the first one — two nanoseconds after the air breakdown, when the spark plasma is located in the vicinity of the laser beam waist and has a shape close to spherical.

Propagation of an optical discharge through optical fibres upon interference of modes

The propagation of an optical discharge (OD) through optical fibres upon interference of LP01 and LP02 modes is studied. Under these conditions after the OD propagation through the fibre, the formation of an axially-symmetric group sequence of voids with a spatial period equal to that of mode interference (200—500 μm depending on the parameters of the fibre) is observed. The groups of voids are formed near the sections of the fibre with a minimal diameter of the intensity distribution of laser radiation. Large spaces between voids in the fibre have allowed us to measure accurately the difference Δn of refractive indices of the fibre core and cladding and distribution of dopants in different cross sections of the fibre after the OD propagation. A substantial increase in Δn (up to ten times) is observed. Approximately half this increase is caused by compression and densification of the fibre material after the propagation of the optical discharge.

Distribution of the laser radiation intensity in turbid media: Monte Carlo simulations, theoretical analysis, and results of optoacoustic measurements

The spatial distribution of laser radiation intensity in turbid condensed media is studied analytically, numerically, and experimentally by the optoacoustic method. Based on optoacoustic measurements and Monte Carlo numerical simulations, the relation is obtained between the optical characteristics of a scattering medium and the position of the maximum of the spatial distribution of radiation intensity in the medium. It is shown that, when the anisotropy factor exceeds 0.8, this dependence has a universal type in the ranges of absorption and scattering coefficients typical for biological tissues. The method is proposed for measuring the extinction and absorption coefficients in light scattering media from the temporal shape of an optoacoustic pulse detected in relative units. An approximate method for solving a radiation transfer equation is verified, and the regions of application of the P3 and P5 approximation are established.

Influence of Conversion Nonlinearity of a Bolometer on the Results of Measuring Nonuniformity of the Intensity Distribution of Laser Radiation

A derivation is given of the dependence of the nonuniformity coefficient of the intensity distribution of laser radiation, measured using a profile bolometer transducer, on the nonlinearity of the bolometer conversion characteristic and the effective power level or effective specific energy. The random error of the measured coefficient is estimated.

Turbulent mixing investigations at the ISKRA-4 facility

Results of turbulent mixing research of thin Al and Au layers under laser acceleration of the three-laser targets Si/Al/Au are presented. Analyses of experimental data under the program SND-TUR, where the Nikiforov model is used for turbulent mixing description, testify to the essential impact of hot spots on the examined processes in distribution of laser radiation intensity on the surface of the target. Experimental setup on the laser beams' smoothing by the “foam” coated on the target, has been considered. The results of the first experiments are presented.

Measurement of the intensity distribution of laser radiation using Bragg diffraction of light

The necessary, estimates were obtained and it was demonstrated experimentally that the Bragg diffraction of light by ultrasonic waves in air may be used to measure the intensity distribution of laser radiation. A transducer utilizing an X-cut quartz crystal was developed to implement this technique. Measurements were made of the angular distribution of the ultrasonic field and its divergence was determined as 4×10–3 rad at 0.9 MHz. In order to confirm this possibility, measurements were made of the laser radiation distribution at λ = 0.6328 μ in the incident and Bragg-diffracted radiation.

Determination of spatial-temporal distribution of laser radiation intensity

An analysis is made of the determination of the transverse distribution of intensity in a laser beam when this distribution departs strongly from the Gaussian form. It is shown that in some cases a one-dimensional distribution can be approximated by a Charlier-type curve. The results are given of experimental investigations of a laser with a spherical confocal resonator; it is shown that the experimental curves can be approximated to within 10% by a Charlier distribution.