Regularities of changing of polarization characteristics of He-Ne laser radiation reflected and transmitted by
inhomogeneous media illuminated with super Gaussian or Bessel beams are investigated. As the inhomogeneous media
the (35 ± 5) μm thickness "cigarette" paper has been chosen.
In this work the abilities of a polymeric polyvinyl alcohol (PVA) films modified by ultradisperse silver nanoparticles to
polarized incident radiation and to form an illumination background close to diffuse scattering with the minimal power
losses were studied.
Laser national standards of Belarus, identical to the international standards, are prepared and accepted. Techniques for laser radiation measurements and measuring instruments calibration are worked out. Measuring systems for metrological maintenance of laser technical equipment have been created.
The electron beam irradiation effect on optical characteristics of polystyrene films modified by carbon nanoparticles is investigated. It was found that reflectance and transmittance of films modified by nanotubes, are in some times less, than corresponding reflectance and transmittance of polystyrene films without additives or films, modified by C60. The electron irradiation of samples modified by nanoparticles results to the decreasing of depolarization degree of laser radiation reflected and transmitted by investigated films.
By means of goniophotometric Stokes polarimeter angular distribution of polarization characteristics of He-Ne laser radiation
reflected by polyvinyl alcohol (PVA) films modified with SiO2 nanosol was investigated. Increasing of nanosol
content in PVA films caused increasing of intensity of diffuse component and decreasing of polarization degree of radiation
reflected at the angles from 20° to 60-70°.
By IR spectroscopy methods the structural changes of high molecular polymers irradiated by CW CO2-laser radiation was investigated. Some changes in the structural sensitive regions at 1250 - 950 and 950 - 850 cm-1 of the IR spectra of the investigated polysaccharides [pullulan (molecular mass of 14500) and microcrystalline cellulose (structural modifications I and II)] were exhibit. These changes indicated that the degree of conformational order of polysaccharide molecules increases under the laser irradiation, while its structural order always decreases as a result of heating by traditional thermal sources.
Systematic errors of the Mueller matrix elements for optical properties of objects caused by a misalignment of initial positions of waveplates principal directions and an analyzer transmission axis are considered. The examination is made for the device, in which the probing radiation polarization properties change at different installations of the first waveplate, and the polarization analysis of a scattered light is carried out using a Fourier series expansion of a signal, which one is produced by a photodetector at a rotation of the second waveplate placed before the fixed analyzer. The estimating equations of these errors arising at a separate misalignment of anisotropic optical elements in illuminating and perceiving radiation channels of the measuring device, and equations on which it is possible to judge about a correctness of these anisotropic elements setting are derived. Combined influence of different inaccuracies of anisotropic element installations is considered by the mathematical simulation method and it is compared to experimentally determined behavior of the Mueller matrix elements measurement systematic errors depending on a misalignment of initial position of the first waveplate principal directions.
By laser reflectometry methods the oxide films characteristics formed on the copper cathode surface in the self-maintained glow discharge in helium at the atmospheric pressure was obtained. During the discharge burning the investigations of the oxide films growth dynamics are carried out.
A laser nephelometer for determination of Mueller matrices of the optical properties of objects transforming radiation has been designed. The nephelometer scheme and operation method are described. There have been derived formulas for matrix elements calculation with operating of the nephelometer designed. The polarization characteristics of the probing radiation in the nephelometer are changed by different setting of the first waveplate retarder, and the polarization analysis of the scattered light is carried out with the use of the Fourier expansion of the signal recorded by a photodetector in the process of rotation of the second retardation waveplate retarder placed in front of an immovable analyzer. The absolute error of the Mueller matrix elements measurement have been determined experimentally.
Directional hemispherical reflectance at 10.6 μm of three modification of carbon-carbon (c/c) composites heated in the air by CW CO2-laser radiation with irradiances ranged from 90 to 16000 Wcm-2 was measured. At the incident beam intensity of 90 Wcm-2 the investigated materials reflectance were found to increase with increasing temperature. When irradiance is more than 200 Wcm-2 the c/c composites reflectance at 10.6 μm is not only temperature dependent but materials modification, and laser irradiance dependent.
It is shown that the largest differences in the angular distribution and meanings of the polarization characteristics of radiation reflected by different plant's leaves are observed for leaves illuminated at the angle of 55 degrees by a He-Ne laser radiation ((lambda) equals 0.63 micrometer) linearly polarized in the plane of incidence. It has been revealed that radiation reflected by a leaf becomes elliptically polarized at observation angles of 55 degrees plus or minus 10 degrees. The ellipticity of radiation reflected by leaves depends on the leaf thickness and the position of the top or bottom of the leaf surface relative to the direction of illumination.
The Stokes parameters of He-Ne laser radiation ((lambda) equals 0.63 micrometer) reflected at the angles of incidence from 5 to 70 degrees by glass reinforced silicon polymer before and after its heating up to 1200 K by CW CO2-laser radiation were measured. The He-Ne laser radiation was linearly polarized either parallel, or perpendicular to the plane of incidence. It is shown that radiation reflected in the specular direction by samples illuminated at near the Brewster angle ((theta) approximately equals 56 degrees) by radiation linearly polarized in the plane of incidence contains an elliptically polarized component. Simultaneously, the change of polarization azimuth of reflected radiation is observed.
The results of investigation of the Stokes parameters of He- Ne-laser radiation reflected by different zones of the material precipitated from the plasma torch formed by the interaction of the linearly polarized pulse Nd-laser radiation with a solid target (tantalum) are presented. It was found out, that the intensity ndicatrixes of reflected radiation depends on the deposited layer position. The dependencies of reflection character of the probing radiation on the types of the mentioned above layers are presented.
The dynamic type Stokes polarimeter is created to measure the polarization characteristics of radiation emitted, reflected, and scattered by objects at different angles to the surface. An analysis of the versions of processing of measurement results has shown that the dependence of a random error in determination of the parameters on the number of positions N of a quarter-wave plate, at which the radiation intensity is measured, is of a similar nature as the dependence on the number of independent measurements of the same quantity (approximately 1/(root)N).
Unidirectional composite materials based on organic (polymer) fibers suffer from anisotropy of optical and thermophysical properties. The anisotropy was experimentally examined by using a He-Ne laser ((lambda) equals 632.8 nm) and measuring the degree and azimuth of optical polarization, and the indicatrix of reflected-light intensity. Samples with smooth, relief, and carbonized surfaces were investigated.
An experimental set-up for the measurement of light reflectance at wavelengths 0.63, 1.15, 3.39, and 10.6 um as well as of surface temperature of composite materials, based on polymer fibers, was developed, and reflectivity of composite samples heated in air and inert (argon) atmospheres was measured. Radiation with a flux density as high as up to 1000 W/cm square from a cw CO2 laser was used for heating the samples under study.
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