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.
Basic principal of stability measurements of laser radiation power and energy, individual uncertainties of measurement results are presented. Two devices for stability measurements are described in brief. Metrological characteristics of these two setups were tested. Individual uncertainties of measurements and the smallest measured relative statistical fluctuation were determined.
The description of designed in the Institute of Physics of NAS of Belarus the device for measurement of attenuation factors of laser radiation attenuators is adduced. The measurement procedure, and realization of calculations and representation of uncertainties of the results of a measurement on the device MAPLR is stated. The results of an attenuator factor calculation for the mechanical attenuator, which is included in a complete set of the laser radiation power and energy meter NM0 -2H and its uncertainty are adduced.
The formula for an evaluation of individual uncertainty of laser radiation power stability measurement due to final number of power measurements, involved in a stability calculation, is derived. There were considered some features imposed by digital power values registration that has resulted in a formula for a stability measurement limit estimation and individual uncertainty of stability measurement caused by an instrument resolution. There was established an influence of drift on measured power radiation stability and the formula of addition drift and fluctuation parts of power stability was checked up.
The opportunity of a Laser Power/Energy meter Laserstar application for determination of power laser radiation stability is considered. Influence of number of power sampling involved for calculation of stability is analyzed. It is established a connection between a digital device resolution and resolution at the determination of power radiation stablility. The examples of power radiation stability measurements for some lasers are given.
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.
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.
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.
The automated device for determining the power stability of cw laser beams pursuant to the requirements of the International Standard ISO 11554 has been created. Using laser radiation intensity measurements in relative units the calculation of mean power values, standard deviations, maximum and minimum readings, power stability and power drift is carried out. The measurements for medium-term (1 min) and long-term (60 min) stability are carried out.
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).
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.
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.
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.
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