Vol 29, No 4 (2016)

The effectiveness of the use of intense radiation from different near- and mid-IR laser sources propagating along high-altitude slant optical paths is numerically estimated on the basis of the optical model of the Earth’s atmosphere developed by the authors. Different laser sources, including chemical oxygeniodine laser (COIL), chain chemical DF laser, and carbon-monoxide (CO) laser are considered with different optical weather conditions taking into account linear and nonlinear optical effects. A COIL source is shown to be the most preferable in terms of the total laser power transmitted along a path, because of weak atmospheric attenuation and minimal effects of nonlinear factors. In addition, this laser source shows the best performance in terms of the mean radiation intensity at a receiver. Among chemical multiwavelength lasers, DF lasers lead in terms of the power transfer function.

A new physical mechanism is suggested to explain unprecedented (about 200-km) northward Gulf Stream shift during summer–fall of 2011 near the Carolina coasts. It is substantiated that inertial motion along straight line and “sliding” off the former trajectory during eastward turn were due to anomalous water heating to a specific temperature (19–20°C), which caused a several-fold reduction in sea water shear viscosity as a result of thermally induced conversion of H₂O spin para-/ortho-isomers. It is shown that the anomalous water heating is a consequence of the Deepwater Horizon disaster in the Gulf of Mexico and associated oil spill; this has led to rainbow film formation over the area of a hundred thousand square kilometers (http://newsland.com/news/detail/id/1218207), thus ensuring extra ocean warming.

A new algorithm of retrieving the surface albedo by values of the coefficient of reflected solar radiation brightness is described. The algorithm returns the albedo of a spatially inhomogeneous Lambertian surface under multiple radiation scattering in the atmosphere and multiple radiation reflection from the surface. Results of solving model problems are presented to demonstrate the algorithm’s capabilities.

The paper presents calculation results obtained for the laser landing system (LLS) efficiency on the base of determining minimum required scattered radiation fluxes from fixed extended landmarks (FELs) which are LLS indicators in the case of visual FEL detection in real operational conditions. It is shown that the minimum required powers for a reliable detection of course glide beams in night conditions from distances L ≈ 1.0–1.6 km at meteorological visibility S_m = 800 m are P_min = 0.5 W for λ = 0.52 and 0.64 µm for deviations from the glide path to the angle φ = 0°–5°. In twilight conditions, green and red laser beams are visible from distances L = 1–1.2 km. The performed calculations corroborated the possibility of creating a new generation laser-based LLS capable of ensuring aircraft landing in conditions of International Civil Aviation Organization (ICAO) category 1.

Gas-dynamic processes that run in pulse-periodic discharges initiated by runaway electrons in atmospheric pressure air are studied with CuBr-laser based laser monitor and schlieren method. Voltage pulses (U = 13 kV, FWHM is 10 ns, front length is 4 ns, negative polarity, f = 60–3200 Hz) applied to a coneshaped copper cathode with cone base diameter, apex angle, and corner radius of cone vertex of 6 mm, 30°, and 0.2 mm, respectively. A flat copper anode was located at a distance of 2 mm from the cathode. It is established that discharge plasma products with copper vapors are carried in a radial direction along the anode surface to a distance of 24 mm for 2.5 ms. The temperature of the gas heated is ~1 × 10³ K. It is shown that the use of the laser monitor in transmitted light provides for contrast images of optical inhomogeneities that appear in gas discharges.

This work reports the synthesis of transparent composite ceramics consisting of Nd:YAG in the central part and Cr⁴⁺:YAG in the edge cladding. The central part of ceramics was shaped like 14-mm-diameter disk or 11-mm-side square and an outer diameter of the edge cladding was 18 mm or 23 mm, respectively. The central part of ceramics had an optical transmittance of ~84% at a wavelength of 1.06 µm. The concentration of Cr⁴⁺ in Cr⁴⁺:YAG ceramics of three different compositions was estimated from the transmission spectra measured and known absorption cross sections. The optimal composition of edge cladding was estimated to be 2.5 mol % Cr + 0.5 mol % Ca + 97 mol % YAG to avoid self-excitation in Nd:YAG.

Laser parameters in He–Ar(Kr, Xe)–F₂ and He–F₂ gas mixtures under pumping by runawayelectron preionized diffuse discharge (REP DD) are studied. It is shown that a REP DD is an efficient XeF* and KrF* laser emission source. Lasing on transitions of molecular fluorine in the VUV region (at 157 nm) was obtained for the first time. It is shown that high homogeneity of REP DD allows an increase in the pulse length in rare gas fluorine lasers. Lasing parameters under the REP DD pumping are comparable with those obtained under pumping by commonly used transverse discharges with preionization.