Yu. A. Morozov

Effect of pump reflections in vertical external cavity surface-emitting lasers

A numerical analysis of the influence of pump reflections on the carrier generation rate and the uniformity of carrier population in the quantum wells (QWs) of vertical-cavity surface-emitting lasers is presented. We have applied an approach allowing us to study the carrier distribution over the absorbing layers and the QW layers of the structure which is quite general and for an arbitrary function of the local carrier generation rate. When analysing the dual-wavelength VECSEL (Leinonen T et al 2007 Opt. Express 15 13451–6), we have found that application of carrier transport blocking layers can result in a highly uniform QW carrier population. The pump reflections are shown to have a great impact on the carrier distribution in the device under study.

Pull-apart formation mechanism of Cenozoic basins in the Tien Shan and their transpressional evolution: Structural and experimental evidence

The geodynamic settings of the evolution of Cenozoic basins in the North and Middle Tien Shan and their Paleozoic framework have been estimated from a kinematic analysis and detailed structural geological mapping of key sites. Two stages of their development in different geomechanical settings are distinguished. It is suggested that in the late Oligocene, Miocene, and early Pliocene, the pull-apart basins developed under the setting of simple left-lateral shear or transtension. Presumably in the late Pliocene and Quaternary, this setting gave way to right-lateral transpression; extension in the basins was changed by compression with the formation of local fold-thrust structural elements. The reconstruction of geomechanical sections was tested by analog tectonophysical simulation. The natural and experimental structural assemblies and patterns reveal satisfactory convergence.

Study of nanocrystals in the dynamic slip zone

Mineral composition is studied and a search to detect nanocrystals is conducted in the surface layers of slickensides formed due to dynamic slip in arkose sandstone. The infrared and Raman spectroscopy show that the slickensided layer is composed of nanocrystals of montmorillonite and anatase measuring ≈15 nm and 3 nm, respectively. The crystalline lattice of the nanocrystals of montmorillonite is stretched by ≈2.5% while the lattice of the nanocrystals of anatase is compressed by ≈0.12%. Deeper than 3 mm below the slickenside surface, the sandstone contains nanocrystals of montmorillonite, beidellite and nontronite, quartz, plagioclase, and anatase. The nanocrystals of anatase have a linear size of ≈8 nm. Their crystalline lattice is compressed by ≈0.03%. It is supposed that montmorillonite in the slickensides was formed due to hydrolytic decomposition of silicates under friction of the fault planes sliding past each other.

Effects of high pressure and temperature on the properties of nanocrystals in rocks: Evidences from Raman spectroscopy

A search is conducted to detect nanocrystals in a sample of apogranitic pseudotachylite, which is a product of extremely strong crushing of granite in a seismogenic fault. Raman spectroscopy revealed nanocrystals of quartz measuring approximately 17 to 25 nm and low-temperature albite ranging from 8 to 30 nm. The crystallographic cell in the nanocrystals is deformed. The internal stresses which might have been responsible for these deformations vary from approximately −300 (compression) to +480 (tension) MPa. It is found that after having been exposed to high pressure (1 GPa) and temperature (470–500°C for 10 minutes and 550–600°C for 16 minutes), the nanocrystals of quartz reduced in size to ≈10 nm, and the nanocrystals of albite, to 13 nm. At the same time, the level of tension in the lattice spacing of quartz increased.

Nonlinear-optical frequency conversion in a dual-wavelength vertical-external-cavity surface-emitting laser

A nonlinear-optical conversion process in a dual-wavelength vertical-external-cavity surface-emitting laser that leads to the generation of difference-frequency radiation in the long-wavelength part of the mid-infrared range (∼17.7 μm) is analyzed numerically. The nonlinear crystal of GaAs is incorporated in the output-coupler mirror and, at the same time, is placed in a Fabry-Perot cavity tuned to the difference frequency. It is shown that the dependence of the nonlinear-conversion efficiency on the GaAs crystal thickness exhibits a pronounced resonance behavior and that the peak power of the radiation in the mid-infrared range can be as high as a few milliwatts with the parameters of the laser and the optical pump readily attainable experimentally.

Nanostructures in the deep xenolite before and after straining

A search for nanocrystals in the sample of deep rock, mantle xenolite from the kimberlitic tube, was carried out. With the use of the Raman spectroscopy method pyrope nanocrystals measuring ∼18 nm and omphacite nanocrystals measuring ∼13 nm were identified. The dimensions of the crystallographic cell in nanocrystals were increased in comparison with macrocrystals. The internal tensile stresses, which could cause these changes, were evaluated by a value of ∼1.1 GPa. The action of quasihydrostatic compression pressure with a value up to 2.5 GPa on a change in the structure and properties of nanocrystals was investigated. As a result of the compression, the sizes of pyrope nanocrystals did not change, but the dimensions of the crystallographic cell increased. The method applied did not make it possible to reliably determine the changes as a result of the pressure of the internal stresses and the sizes of the omphacite nanocrystals.

The posthumous tectonics and mechanism of exhumation of granitic plutons: The case of the Transbaikal region and the Tien Shan

The study of granitic plutons of the Baikal Highland and the Tien Shan has made it possible to establish new features of their posthumous (after incorporation into the consolidated Earth’s crust) structural reworking and to understand the implications of the cataclastic flow for the exhumation of the crystalline basement in the studied regions. It is shown that granitic plutons undergo appreciable structural transformation at the stages of tectonic reactivation that is significantly separated in time from the moment of formation of plutons as geological bodies. The 3D cataclastic deformation is the main mode of structural reworking of granitic plutons, while the cataclastic flow is the main form of their mobility. Newly recognized slice structures characterize the volumetric deformation of granites.

Raman spectroscopy of nanocrystals in rock

Nanocrystals were detected and identified in rocks by the method of Raman spectroscopy. The experiments showed that the Raman scattering spectra of fine-lamellar arkosic sandstone exhibit bands corresponding to lattice vibrations of anatase, α-quartz, and plagioclase. In all spectra of the rock, the bands are displaced towards high frequencies as compared with their position in spectra of single crystals and widen on the same side. These results show that, in all of the studied places of the sample, the particles of anatase, quartz, and plagioclase have nanometer sizes, namely, of the order of 10 nm in anatase and quartz and about 20 nm in plagioclase. Moreover, in different places of the sample, not only the shape and position of the bands under study but also their intensity vary, the latter being directly proportional to the concentration of nanocrystals.

Nature of electric conductive layers of the upper crust and infrastructure of granites of the Central Tien Shan

We studied the infrastructure of granite massifs of the Central Tien Shan and its correlation with the electric conductive layer of the upper crust, which made possible to reveal new peculiarities of the structure of the granite layer in the region and to clarify the nature of low resistivity layers.

IR spectroscopy of quartz nanocrystals formed during intense crushing of a heterogeneous material (granite)

The spectra of the imaginary part ɛ″(ν) of the permittivity of quartz single crystals and a heterogeneous material, i.e., pseudotachylite, formed during intense crushing of granite in the region of the seismogenic Earth’s crust fault have been calculated from IR reflection spectra. It has been found that all strong bands in the pseudotachylite spectrum ɛ″(ν) correspond to lattice vibrations in quartz nanocrystals. Bands are asymmetrically broadened due to dielectric and phonon confinements. Linear sizes of quartz nanocrystals have been estimated from the broadening as ∼70 nm. The frequency of nanocrystal lattice vibrations is higher than that of the macrocrystal, which is caused by lattice compression. The internal stresses which could cause the observed change in the frequency are ∼200 MPa.