Home – Home – Jornals – Atmospheric and Oceanic Optics 2016 number 3

Based on the optical model of the Earth atmosphere developed by the authors, the numerical simulations of the propagation effectiveness of intense radiation of different laser sources in the near- and mid-IR spectral ranges on high-altitude slant optical paths are carried out. Different laser sources, including chemical oxygen-iodine laser (COIL), chain chemical DF laser, and carbon-oxide (CO) laser are considered upon different optical weather conditions taking into account linear and nonlinear optical effects. We show that in terms of the net laser power transmitted along a path, the most preferable is the use of a COIL source because of low atmospheric linear attenuation and minimum influence of nonlinear effects. This laser source also demonstrates the best performance in terms of the mean radiation intensity at the receiver plane. Among multispectral chemical lasers, DF lasers take the first place when comparing the power transfer function.

Temporal dynamics of maximum intensity and laser power in a finite-size aperture of the focused radiation at a wavelength of 10.6 microns under thermal self-action in a clear turbulent atmosphere is analyzed by means of computer simulation. Propagation of Gaussian beams along up to 160 m path is considered. It is shown that under strong turbulence conditions there are time intervals in which the maximum intensity in the middle of the path of a tightly focused beam is greater than in the focal plane at the end of the path.

Formation of light bullets is numerically investigated during filamentation of near and mid-IR femtosecond pulses in condensed media at anomalous group velocity dispersion. On the example of filamentation of microjoule pulses at wavelengths of 1.4, 1.8, and 2.2 mm in fused silica at powers slightly exceeding the critical self-focusing power, it is established that the subsequent light bullets are not formed if the dispersive length is much bigger and much smaller than the self-focusing length. It is shown that the peak intensity in light bullets does not depend on the initial pulse intensity, is determined by the multiphoton order of laser plasma generation, and increases with the order. In fused silica, the peak intensity in a light bullet makes about 40 TW/cm² during filamentation of microjoule pulses at a wavelength of 1.4-2.2 mm, and in CaF₂, the peak intensity reaches 120 TW/cm² for pulses at a wavelength of 3 mm. The light bullet is a short-lived formation existing on less than 1 mm distance. It is found that the change in the pulse energy at a wavelength of 3 mm during filamentation in CaF₂ influences the number of light bullets and does not increase their time of life.

A new physical mechanism of Gulf Stream abnormally large heating (up to 20 ^oC) and current shifting to the North (~ 200 km) in the summer 2011 off the coast of New Carolina was suggested and discussed. The key point is a tenfold decrease of sea water shear viscosity due to conversion of H₂O para-ortho spin isomers when heated to a temperature singular point (19-20 ^oC). This results in Gulf Stream shifting from the previous trajectory due to an inertial motion in a straight line. The observed phenomenon was triggered by Deepwater Horizon disaster in the Gulf of Mexico in 2010. The huge oil eruption resulted in iridescent film formation over a hundreds of thousands of square kilometers area (http://newsland.com/news/detail/id/1218207). The thin oil film dramatically changed the solar radiation absorbance and sea water thermodynamics, blocked the evaporation.

Fluorescence of thin oil films on the water surface induced by femtosecond UV laser pulse was studied experimentally. A wide range of laser pulse intensity including filamentation mode was studied. Applicability of this method to femtosecond UV pulses with two central wavelengths of 248 and 372 nm were compared. There was demonstrated that the spatial resolution of the fluorescence localization was not worse than 30 cm.

The new atmospheric correction algorithm is presented. The algorithm gives albedo of a heterogeneous lambertian surface taking into account multiple scatterings and reflections of the solar radiation. Test results to demonstrate potential of the algorithm are presented.

In the lidar complex, the combined optical method for sensing the lower and middle atmosphere was used. The method is based on the receiving signals of Rayleigh (elastic molecular scattering of light at a wavelength of 532 nm) and Raman (radiation of the first vibrational-rotational transition of nitrogen molecules at a wavelength of 607 nm when excited by the laser radiation at a wavelength of 532 nm) light scattering. The use of Raman channel made it possible to eliminate the distorting effect of aerosol at altitudes of its localization (up to 25 km) on the accuracy of temperature measurement. Extended temperature profiles at altitudes from 7 to 60 km, covering the upper troposphere and middle atmosphere, were obtained during simultaneous measurements of the signals at two receiving channels. A good agreement of the data with satellite and upper-air measurements and model results was obtained.

We consider the results of remote spectrophotometric and lidar measurements of the total ozone and nitrogen dioxide contents and temperature obtained at the Siberian Lidar Station (SLS) of V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences (Tomsk: 56.5°N, 85.0°E) in comparison with the results of analogous satellite measurements. The ground-based measurements of the total ozone content are performed with the help of a М-124 ozonometer; and the measurements of the NO₂ content are carried out with an automated spectrophotometer. The ground-based lidar measurements of temperature are conducted on the basis of SLS measurement complex. These measurements are compared with data of radiosonde and satellite measurements. The satellite measurements are performed by the TOMS and IASI instrumentation.

The May-July precipitation data for the Russian Southern Ural reconstructed via treatment of the radial growth of larch late Sukachev (Larix sukaczewii Dyl.) were analyzed with a wavelet transform. Next, a cross wavelet transform was used to compare the reconstructed data with the average annual values of Wolf numbers (sunspot numbers (SSN)) and the North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO) indices. The wavelet analysis revealed hidden periodicities in the original series and allowed one to define the relationship with the Wolf numbers and the NAO and AMO variabilities. It was found that the dominant 11-year SSN cycle is present in the reconstructed data almost over the entire time of observation. The reconstructed series of May-July precipitation showed good correlations with the NAO index for 8-11 year periods and with the AMO index for 11-50 year periods. In the analysis, the observation time spans 375 years (1631-2005) for the reconstructed May-July rainfall series, 306 years (1700-2005) for the Wolf numbers, 141 years (1865-2005) for the NAO index, and 150 years (1856-2005) for the AMO index.

The article presents the calculation results of the laser landing system efficiency (LLS) based on the definition of minimum required fluxes of scattered radiation from fixed extended pinpoints (FEPs), which are the LLS indicators at the visual detection of FEPs in the field conditions. It is shown that the minimal power P_min = 0.5 W for  = 0.52 m and  = 0.64 m is required to reliably detect the laser beams of the course glide group at night from distances L » 1.0-1.6 km at S_m = 800 m for deviations from the glide path to the angle  = 0-5. In twilight conditions, the green and red laser beams are visible from the distance L = 1-1.2 km for all S_m. When L = 1.6 km laser beams are visible at S_m > 2 km. The presence of commercially available lasers and the calculations confirm the possibility of creation of the LLS based on a new generation of lasers that can ensure aircraft landing satisfying I Category ICAO.

The paper presents the results of theoretical and experimental studies of the second harmonic generation process in the Ti:sapphire femtosecond complex, which includes generator of the femtosecond pulse, stretcher, regenerative amplifier, two multi-pass amplifiers, compressor, and second-harmonic generator. This complex provides 50-fs pulses with energy of 20 mJ and is used as a master oscillator in the THL-100 hybrid laser system, which operates in the visible region at a wavelength of 475 nm. Experiments and calculations for various beam parameters of the fundamental harmonic, such as radiation intensity, spatial profile of the beam, and the level of the noise component, were performed. It is theoretically shown that in the absence of the noise component in the beam of the fundamental wave a good homogeneity of the second harmonic should be observed. When making the amplitude inhomogeneities in the first harmonic even greater inhomogeneities in the second harmonic appeared. It is experimentally shown that the inhomogeneity of the second harmonic beam increases with the beam energy.

The paper presents first results on how CuBr laser active media can be used for high speed nanomaterial production process imaging. Various visualization circuits are considered. The results of visualization obtained using these circuits are given. The possibility of full suppression of stray background light, which is the laser monitor main advantage for diagnostics, is demonstrated. The application areas for each circuit are discussed.