Vladimir A. Grigor'ev

Nonlinear optical limiters of laser radiation based on reverse saturable absorption and stimulated reflection

We presented wide range of laser-radiation optical limiters that are based on different physical principles, operating in 400-12000 nm spectral range with rate 100-1 ns and providing wide dynamic range of limiting required for eye and sensor protection. We propose and investigate a method for reduction of the optical limiting threshold due to the Bragg reflection in a system with distributed feedback. The limiting threshold with the Borman effect, accompanying by diffractional absorption suppress and stimulated reflection from the LC Bragg grating, is about (mu) J/cm2 for nano seconds pulse. We investigate nonlinear optical limiters of laser radiation based on fullerene-contained materials, operating on the basis of reverse saturable absorption (RSA) as well as stimulated nonlinear reflection of laser radiation. Fullerenes C60, C70 and C84 were studied with the second harmonic of Nd:YAG laser, 532 nm, single-mode radiation pulses of 30 ns duration and maximum energy 0.35 J. Definite thresholds of RSA limiting vary from 0.05 to 0.1 J/M2) depending on fullerene density and limiting scheme. Dynamic range of limiting sufficiently increases for multi-pass trains, the fluence decreases up to 10000 times. We elaborate 3000-12000 nm laser-radiation attenuators based on multi-layer interference containing vanadium-dioxide film. It is shown that these attenuators can operate due to both amplitude and diffraction effect. Attenuation is up to 1x103- 1x105 times for 1 MW/cm2 beams, operating time being 30-100 ns. For sensors in cooled optical systems, radiation attenuators can be used with vanadium oxides having the phase transition at cryogen temperatures.

Photodynamics of nonlinear fullerene-containing media

The results of theoretical and experimental studies on photodynamics and mechanism of nonlinear optical processes, responsible for optical limiting of power radiation in the wavelength range from 0.3 to 1.3 microns, are presented. Peculiarities in the mechanisms of optical limiting for different fullerene-containing matrices, including solutions, solid-state and polymer systems, are shown.

Possibility of realizing fullerene-oxygen-iodine laser with solar pumping (sun-light FOIL)

We consider the possibility to design the fullerene-oxygen- iodine laser with optical pumping (solar, particularly). It is assumed that singlet oxygen is formed at pass of molecular oxygen through (and interaction with) mixture of lower and higher fullerenes in the triplet metastable state obtained at illumination of fullerenes. The presented results of estimates by a photokinetic model show the opportunity to reach the efficiency of the FOIL with solar pumping at the level of several tens of percents. We present the results of experimental and theoretical studies of singlet oxygen yield at interaction of optical pumping with fullerene in solutions. Laser radiation with wavelength of 532 nm and wideband lamp radiation for imitation of solar radiation were used as pumping.

Light-induced scattering in laser radiation nonlinear optical limiting based on fullerene-containing media

The contribution of light induced scattering to nonlinear optical limiting is theoretically and experimentally investigated. It is shown that light induced scattering is caused by fine-scale (1 divided by 10 micrometer) inhomogeneities formation, very low (comparable to spontaneous noise) laser beam inhomogeneities can evolve into light induced scattering. The numerical modeling of scattered radiation angular distribution and laser radiation attenuation in optical limiters was performed. The modeling results were compared with the experimental ones.

Complex studies of formation and transportation of high-power CO2 laser radiation along a horizontal atmospheric path

In the present paper, theoretical and experimental studies of formation and transportation of radiation of a high-power repetitive pulsed CO2 laser in the optical system and along the 0.5 km horizontal atmospheric path have been performed. As is shown, the use of a light- guide, cooled metallic optics and adaptive system in the telescope provides efficient delivery of the high-power radiation.

Photoluminescence of singlet oxygen in solutions of fullerenes and suspensions of fulleroids

tum Molecular oxygen in the singlet state plays an import role in nature and technology. It participates in a number photobiological processes, being an active product in ph dynamic oxidation reactions of organic and biological co pounds. In particular, for example, singlet oxygen exe photodynamic action on genetic material, proteins, me branes, and the retina of the eyes, and singlet oxygen carcinogenic properties. 1 The activity of singlet oxygen can be used in photochemotherapy for directed action on tu cells and viruses. 2

Nonlinear optical systems based on fullerene-containing media

We present the results of theoretical and experimental studies on creation of nonlinear optical systems on a base of fullerene-containing media: power radiation limiters, photorefractive media for dynamic hologram recording, and devices for controlling spatial and temporal parameters of radiation.

Far-field distribution of pulse-repetitive CO2-laser radiation after propagation along strongly turbulent horizontal and slope atmospheric beamlet

In conditions of high turbulence, propagation of laser radiation along the horizontal path is characterized by significant decrease of intensity in far zone. Due to different factors, opportunities of adaptive means for atmospheric compensation in this case are rather poor. The possible way for overcoming the turbulence is to elevate the output aperture of the laser optical system over the most perturbed atmospheric layers. As the performed calculations have shown, the elevation up to 15 meters allows us to increase the tolerated turbulence range almost eight-fold.

FULLERENE-BASED NONLINEAR OPTICAL DEVICES FOR FAST CONTROL OF SPATIAL, POWER, AND TEMPORAL CHARACTERISTICS OF LASER RADIATION

We present the results of experimental and theoretical study of opportunities for improving of spatial homogeneity in the near field of Nd:YAG-laser radiation at (lambda) 532 nm by means nonlinear optical limiting of laser radiation, that take place in fullerene-containing medium (with C60). A scope for the smoothing out a profile of generation impulse was studied. The experiments were performed with fullerene- containing composites C60-solution. The mechanism of optical limiting is discussed.

Effective transportation of laser radiation through the atmosphere

Peculiarities of constructing adaptive optical systems for forming and transportation of laser radiation through the atmosphere are considered. Results on elaboration and testing of the elements and the adaptive schemes on the special test-bench are given. The results on investigation of real-time compensation of the atmospheric phase disturbances using the adaptive optical train with the heterodyne wavefront analyzer, the electro-optical phase corrector, and the data-processing system based on the neural network are also reported. We analyze possible means of construction of adaptive optical trains to one-channel laser radiators and multi-channel phased systems.