The paper compares the absorption and emission properties of bulk glasses prepared by sintered in an iridium crucible
and optical fibers fabricated by the powder-in-tube method. Both the bulk glasses and fibers were prepared from
identical mixtures. The emission properties of the bulk samples and fibers were similar, while the "gray losses" in the
fibers were an order of magnitude lower than those in the crucible melted glasses.
Watt-level Bi fiber lasers have been demonstrated at 1280, 1330, 1340, 1360 and 1480 nm with the maximum output
power of up to 10W and with the efficiency of up to 50% for the first time. The bismuth-doped phosphogermanosilicate
fiber amplifiers operating within the wavelength range 1300-1500 nm have been developed. The net gain of more than
20 dB at the wavelengths of 1320 and 1440 nm under the 200-300 mW pump power was obtained. The 3 dB bandwidth
of the amplifiers was larger than 30 nm, the noise figure being 4-6 dB.
The fast mode of optical discharge propagation in optical fibres was observed. In contrast to the known fibre fuse effect
such optical discharge propagation is accompanied by fibre cracks and velocity reaches≈3km/s under the intensity 40W/ μm<sup>2</sup>.
Highly phosphorus doped (7 - 17 mol%) single-mode fibers for the application in Raman laser have been manufactured. It has been established that with increasing the P<SUB>2</SUB>O<SUB>5</SUB> concentration level, both optical losses and the fiber Raman gain coefficient increase. Using the fiber technology developed, the maximum efficiency of a single-cascaded Raman laser is achieved at a phosphorous pentoxide doping level of 12 - 14 mol% P<SUB>2</SUB>O<SUB>5</SUB>.
The results of experimental research and numerical modeling of the 1.3 micrometers Raman fiber amplifier based on the high Gao<SUB>2</SUB> doped fiber are presented. The Raman amplifier was pumped by the P<SUB>2</SUB>O<SUB>5</SUB>-doped fiber Raman laser. The measurements of gain and noise figure in broad range of experimental conditions are fulfilled. The amplifier gain coefficient was measured to be 42 dB/W.
Extremely simple and efficient 1.24 micrometers phosphosilicate fiber-based Raman laser was developed. The cavity of the Raman laser was formed by the Bragg gratings written directly in the phosphosilicate fiber. The investigation of the laser parameters, mathematical simulations and optimization of the Raman laser were carried out. As a result of optimization the 1.24 micrometers output power of 2.4 W was reached at the neodymium fiber laser pump power of 3.6 W, that corresponds to the Raman laser quantum efficiency of 77%.
The interference structure of the laser light scattering cone behind the laser spark was observed for the first time. We propose consideration of the observed structure as a result of interference of the laser radiation, scattered by two or more self-focusing centers in laser spark air plasma. We have investigated the spatial distribution of the laser radiation scattered by the laser spark. These experiments differ from the previous ones by use of the four harmonics of Nd-laser radiation. As a source of radiation the Nd-laser installation was used with the master oscillator, operated on one transverse and longitudinal mode. The pulse duration was 10 ns, pulse energy -- up to 20 J and beam divergence -- 8 (DOT) 10<SUP>-5</SUP> rad. After the frequency conversion by means of the KDP crystals the second, third, and fourth harmonics radiation appeared with the energy up to 10 J (in fourth harmonic). In each of our experiments one laser harmonic radiation was focused into the hermetical chamber, filled with air (10 divided by 760 mm Hg). For the scattered radiation registration we photographed the scattering flat white screen, illuminated by this radiation. This screen was disposed parallel to the laser beam axis at the distance of 2 - 6 mm from it. We observed a cone-like symmetric respectively to the laser beam axis radiation scattering in the spark. That enables us to determine the maximum angle alpha of laser radiation deviation as a function of pressure p and wavelength lambda (or number of harmonic N).
The process of fourth harmonic generation in multicascade laser installation is experimentally investigated. The operative correction of phase synchronism in nonlinear crystals permits to compensate an installation parameters drift and provides stable radiation conversion to the 4th harmonic with efficiency 0.4 divided by 0.5 at E<SUB>4</SUB> approximately 10 J.