Experimental study of the influence of laser radiation power on the reflection coefficient of germanium and silicon at a wavelength of 355 nm

The dependences of the reflection coefficients at a wavelength of λ = 355 nm for germanium and silicon single crystals on the energy density of impacting laser radiation in the range 0.01 - 0.1 J/cm2 have been measured. Analytical expressions were obtained. It is assumed, that they are also valid in the range 0.1 - 1.0 J/cm2. With a further increase in the energy density, the dependence should acquire a more complex character due to the resulting optical breakdown.

National primary standard for the unit of average laser radiation power GET 28-2016

The description of the National primary standard for the unit of average laser radiation power GET 28-2016 with a power range from 10–9 to 5·10–3 W is described. The principle of operation of a standard based on a photoelectric trap detector in the range from 10–9 to 5·10–3 W is described. As a result of metrological studies at National primary standard, it was determined that the value of the total standard uncertainty of reproduction and transmission of an average power unit for the range from 10–9 to 5·10–3 W is no more than 0.36 %. The model and theoretical characteristics of the measuring beam splitter, allowing to expand the range of the National primary standard to the range of kilowatt power levels, are presented. National primary standard allows solving the problems of metrological support of promising low-level laser ranging systems both in the ground and in the aerospace field, ensuring the uniformity of measurements of radiometric parameters of low-intensity laser radiation fluxes.

CONTROL OF CO2 LASER POWER BY ACOUSTIC FIELDS

The present study investigates the optimization of the operation of the CO2 laser in the acoustoplasma mode (i.e., dependence of the laser radiation power on the composition of the working mixture, pressure, value of the direct component of the discharge current, frequency, and modulation depth). A three-dimensional dependence on the frequency and modulation depth of the discharge current is experimentally obtained for the normalized efficiency of the conversion of the electric power supplied to the discharge tube into laser power. The maximum gain when transition to the acoustoplasma mode exceeds 2.5 times. The optimum depth of the discharge current modulation is 0.5–0.7. The laser radiation power modulation caused by the discharge current modulation is measured. Laser power is not modulated at modulation frequencies of current >1 kHz. Meanwhile, at current modulation frequencies <0.5 kHz, the modulation depth of the laser radiation power nonlinearly depends on the modulation depth of the discharge current and has a threshold character. The modulation depth of the laser radiation power is associated with the creation of an acoustoplasma and not simply with the discharge current modulation.

Noncontact Control by Laser Conoscopy of Optical Homogeneity of Heavily Doped LiNbO3: Zn

A non-contact method using laser conoscope the studies of optical homogeneity of a series of heavily doped LiNbO3crystals (4.46–4.69 mol. % ZnO). For all crystals not detected additional anomalies in сonoscopic patterns at increase of laser radiation power up to 90 mW, due to the presence of static and fluctuating defects induced in the photorefractive crystal by laser radiation.