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A laser source for bleaching passive Q-switches of erbium - ytterbium lasers is developed and studied. The developed and studied compact pulsed module (peak power exceeding 10 W in a pulse with a duration of 1 us at a wavelength around 1550 nm) is made on the basis of a semiconductor lasers with an ultra-narrow waveguide integrated with a pulsed pump card. To optimise the output laser characteristics, a series resistance was used in the laser pump circuit. The powers of the free-space and fibre-coupled modules at a temperature of 25 degC are 15 and 12 W, respectively, at a pulse shape close to rectangular.

A model system of two differential rate equations is proposed to describe the temporal characteristics of the radiation of a solid-state laser with high-energy pumping. Using a laser head with a YAG:Nd active element and a side-pumped laser diode array unit as an example, a method is discussed of determining the excitation levels of the active elements at which the amplified luminescence and the nonaxial (stray) lasing modes begin to manifest themselves in the output radiation dynamics all the way to the limitation of the maximum pulse energy generated by a solid-state laser in the Q-switched regime. The proposed approach to analyzing the role of the processes associated with the formation and evolution of amplified luminescence fluxes and nonaxial (stray) lasing modes in the active media can also be applied to other types of laser radiators.

A method of modelling the conditions for side pumping a passively Q-switched erbium laser with linear laser-diode arrays is proposed that makes it possible to determine the most efficient geometry for the placement of the linear arrays relative to the active element, taking into account the characteristics of not only the diode arrays and the active element, but also of the optical cavity that is used. The results of the modelling make it possible to choose the distance between the linear arrays and the active element and the allowable shift of the linear arrays relative to each other, and this optimizes the matching of the excitation and lasing conditions. The proposed optimization method takes into account the divergence and polarization of the radiation of the diode arrays, the geometrical and optical properties of the active element, and the configuration of the lasing mode. The theoretical results of the modelling are compared with the experimental data.

The spatial, temporal, and spectral characteristics of the output radiation of diode-pumped laser systems and optical amplifiers with active elements made of Nd : YAG ceramics are studied. It is shown that the divergence of radiation in the subthreshold regime has the form of concentric nested cones emerging from the active element (AE) faces at angles of 2 – 4°. A model explaining the experimentally observed phenomenon is proposed based on the mechanism of scattering of the generated beam from the granular structure of the optical ceramics. Analysis of the divergence pattern makes it possible to estimate the grain size and the optical quality of ceramics. The output beam divergence in the lasing regime is determined mainly by the cavity parameters and does not exceed several milliradians. The scattering events in this case serve as sources of additional optical losses. Luminescence enhancement and parasitic oscillations in the AE volume restrict the possibility of using Nd : YAG ceramics for fabricating AEs of high-power optical amplifiers.

An all-solid-state multiwave laser radiator (lasing wavelengths 1064, 532, and 355 nm), integrated in a single implement with a telescope, has been developed for use in aerosol lidars. The main radiator is the master laser and an amplifier based on a YAG:Nd crystal, excited by laser diode arrays using a transverse pumping layout. In the Q-switched regime, the energy of the output pulses of the YAG:Nd laser radiator reaches 400 mJ (1064 nm). With simultaneous lasing at three wavelengths, the radiator forms radiation pulses at 1064, 532, and 355 nm, with energies of 170, 150, and 80 mJ, respectively. The pulse width is 8–11 ns at a repetition rate of 10 Hz. The developed multiwave laser radiator is effective for use as a component of aerosol lidars with an atmospheric probing range of up to 40 km.

The energy levels of gallium and arsenic vacancies as well as silicon impurities in the band gap of InxGa1 − xAs have been found as functions of the indium content. The effect of defects on the lasing output power and on the optimal reflection coefficient of output mirrors of laser diode arrays (LDAs) based on the In0.11Ga0.89As/AlGaAs heterostructures has been estimated. It has been shown that the lasing output power of LDAs whose active level contains defects with deep energy levels in the band gap is substantially lower (with other conditions being the same) than that of LDAs with shallow level defects in their active layers.

A Q-switched Nd : YAG laser with a high-power transverse diode pumping and injection of seed radiation generated by a single-frequency semiconductor laser is described. The threshold seed radiation power at which the Q-switched Nd : YAG switches to the single-frequency mode is 0.44 mW (radiation intensity 5.6 x 10-2 W cm-2). With increasing injection power, the spectral and power characteristics of the Q-switched laser almost do not change at a constant excitation of its active medium. The spectral linewidth of the Q-switched Nd : YAG laser with injection from a TLD-1060-14BF single-frequency semiconductor laser module does not exceed 90 MHz (wavelength 1064 nm).

A compact tunable source of laser radiation has been created on the basis of an Al_2O_3:Ti^3+ crystal, with an energy per pulse of up to 85μJ, a pulse width of 5ns, and an M^2 parameter of the order of 1.1, pumped with the second-harmonic radiation of a neodymium laser with longitudinal diode pumping. A KTP crystal with 58% conversion efficiency was used to convert the neodymium laser's radiation to the second harmonic. The external differential quantum yield of the titanium-sapphire laser with respect to the second-harmonic radiation was 41%.

A slab laser based on borosilicate phosphate glass doped with erbium and ytterbium with transverse diode pumping has been developed and investigated. In the passive Q-switching regime, using a shutter based on a glass-crystalline material with nanosize spinel doped with divalent cobalt ions, the energy of the output radiation was 1.3mJ with a pulse width of 19ns. With active Q switching, the energy of the developed laser was 2.3mJ. The internal optical losses are estimated, and the parameters of the passive shutter are determined.

The propagation parameter M^2 of the beam of an ytterbium-erbium glass laser with transverse diode pumping has been experimentally investigated for various cavity configurations. The polarization characteristics of the laser radiation are presented for cases in which the active medium is excited by two and four linear laser-diode arrays.

1.The concentration dependences of the activation energy of electric conductivity in solid solutions with spinel structure can provide valuable information on the type of short-range order in the octahedral sublattice.2.In the octahedral sublattice of solid solutions with type 2–3 spinel structure there exist type 1:7, 1:3, 3:5, and 1:1 short-range order configurations of differently charged cations.3.Making use of the composition dependence of the activation energy of electric conductivity, one may calculate the cation distribution in the sublattices for systems characterized by more than one cation distribution function.4.Knowing the cation distribution in a solid solution, it is possible to predict the concentrations at which minimal and maximal activation energies should be expected.

The properties of an ordering solid solution are substantially dependent on the long-range and short-range order parameters; a method is given for representing a binary solid solution as a set of cluster components whose short-range order parameters are incorporated out to the second coordination sphere. The scheme is illustrated via the lattice parameter and Debye temperature for Ti-Mo alloys (bcc lattice) and via the magnetic moment of Fe-Pd alloys (fcc lattice). The method allows one to describe nonmonotonic composition-property relationships and to define the values of properties for ordered structures.

A model is proposed for representing microinhomogeneities of disordered alloys as cubic structural domains. The concept of an effective atom introduced in this article made it possible to express the relation between property and composition in terms of property parameters of nearest atom pairs, the domain size, and the short-range parameter of the first coordination sphere a1. Using as an example the concentration dependence of the Young modulus, the thermal linear expansion coefficient, and the magnetic anisotropy constant we have determined the property parameters of atom pairs and the composition dependence of a1 and of the domain size of disordered alloys of the Ni1-cFec, system (0=c=0.25).

A scheme is proposed for calculating the short-range order in the method of cluster components for an n-component solid solution, taking into account an arbitrary number of spheres. The calculation of a single-, two-, and three-coordination spheres for a binary system and a calculation of a single sphere for a triple system are considered in detail. In the case of a binary system the possible type of property-composition dependence for a random distribution of the atoms in the case of one, two, and three coordination spheres are analyzed. The method is illustrated using a calculation of the concentration dependence of the elasticity constants of a KIcBr1-c solid solution.

We have grown films of magnesium, lithium, zinc, and nickel-zinc ferrites, varying in thickness from 0.5 to 8 μm on polycrystalline sapphiresubstrates by coating the surface of the substrate with an aqueous nitric acid solution of salts of the elements which compose the ferrite. The lattice parameter of the ferrite film increases with the film thickness and becomes constant at thicknesses greater than 8 μm. We have determined the ratio of the theoretical strength limit to the macroscopic one in the film based on the change in the interplanar distanced220and the lattice parameter calculated from it, under the assumption that the changeΔa(h)=a∞=a(h) results from macroscopic stresses in the film. This ratio shows that whenh=1μm the microstresses in the film are an order of magnitude smaller than the theoretical strength limit. At larger film thicknesses this macroscopic stress becomes even lower, and at the external surface of thick films it goes completely to zero.

The structure and magnetic and electrical properties of solid solutions of NiFe2(1-cCr2cO4 (a compound with the spinel structure) are studied. These properties depend on the way in which the samples are produced and on the cation distribution with respect to the crystal lattice points. In order to find the cation distribution with respect to the crystal lattice points the method of cluster components is employed.

The concentration dependences of the crystal lattice parameter and the Curie temperature of the magnetic ceramic, obtained in air at a calcination temperature of 1100°C from charges with the composition (1-x)MgFe2O4+x(0.5 CuO × 1.25 Fe2O3), where 0=x=1, were studied. The dependences of the magnetic parameters of the hysteresis loop as well as the resistivity on the composition of the charge were investigated. The single-phase ceramic, having the structure of spinel, is formed for x < 0.5, and in samples with x > 0.5 a tetragonal phase and a-Fe2O3 are present. The maximum squareness ratio of the hysteresis loop (SHL) is observed in the region x=0.1-0.4. The region of high values of the squareness ratio is also the region of solid solutions containing defects, when ?-Fe2O3 quasiparticles, having the structure of imperfect spinel, are present in the solution.

The density, residual magnetic induction, coercive force, and energy product of barium ferrites were investigated as a function of the amount of glass added to the batch and duration of sintering at 1150°C. The compressive strength as a function of the concentration of glass added to the batch was found in sintering for 90 min. For a mass concentration of glass of 2%, the compressive strength was 4.7·l108Pa, which is almost 2 times higher than for pure barium ferrite.

The density, residual magnetic induction, coercivity, energy product, and ultimate compressive strength are investigated as functions of the amount of glass introduced into the charge of strontium hexaferrite and of the sintering time of the specimens. The optimum highly coercive isotropic ferrites contain 2 and 3% glass and are sintered for 15–17 min at a temperature of 1150°C.

The power and spatial characteristics of a longitudinally diode-pumped laser based on a composite YVO4/Nd:YVO4crystal are studied. It is shown that the use of a composite crystal allows one to increase the external slope quantum efficiency from 36% to 41% and decrease the quality factor M2of the output beam from 2 to 1.5 compared to these parameters for a Nd:YVO4crystal.