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Selective area epitaxial growth of III–V and III–N nanostructures and nanowires was proven efficient for synthesis of scalable and highly ordered electronic and optoelectronic nanomaterials on dissimilar substrates. Here, we present experimental data and a supporting model showing that the heights of GaN nanowires obtained by selective area growth on a-AlxOystripes in SiNxmask are spatially inhomogeneous, with noticeably higher nanowires at the edge of the stripes compared to the middle region. Careful investigation of all stages of the nanowire formation process, including nucleation of GaN islands of different density and size and the nanowire growth itself, allows us to identify surface diffusion of Ga adatoms from the mask into the stripes as the origin of the observed inhomogeneity. The height inhomogeneity strongly depends on the width of the stripe. The model fits very well the whole set of the observed phenomena, including the nucleation time, density, and size of GaN islands and height profiles of GaN nanowires versus the position across the stripe for different stripe widths. On a general note, these findings demonstrate that nucleation and growth kinetics in selective area epitaxy depends on the size of the pattern, which makes it very different from growth on the equivalent planar layers.

The fundamental mode of a conical refraction resonator, i.e., an optical cavity where light experiences conical refraction (CR) from a biaxial crystal, is experimentally demonstrated in the plano-concave cavity configuration. We have discovered that the fundamental CR mode is characterized by the polarization and intensity structures of CR beams between the plane mirror and CR crystal, and it resembles the fundamental Gaussian mode with homogeneous polarization between the crystal and concave mirror. We theoretically explained this fundamental CR mode using the dual cone model and symmetry of the CR phenomenon and confirmed this explanation by numerical simulations.

GaAs nanowire (NW) arrays were grown on Si substrates by selective-area molecular beam epitaxy (MBE) using the self-assisted vapor-liquid-solid (VLS) method. In the self-assisted VLS method, the GaAs NW diameter is determined by the size of a Ga droplet at the top of the NW. Absorption of the solar spectrum for photovoltaic devices is optimum with a GaAs NW diameter of ∼170 nm, requiring a Ga droplet during the growth of a similar size. Control of the Ga droplet size, and therefore the NW diameter, is demonstrated by controlling the V/III flux ratio during the MBE growth. A V/III flux ratio near unity rapidly increased the Ga droplet volume during the NW growth, thereby creating an inverse-tapered (funnel-shaped) NW morphology. Numerical simulations indicated that the inverse-tapered NW showed strong broadband absorption of the solar spectrum due to the absorption of consecutively longer wavelengths toward the base of the NW.

Generation of the second harmonic of semiconductor laser radiation in the IR range (980-1140 nm) in ridge waveguides with a large refractive index step, formed in periodically poled nonlinear LiNbO3 crystals, is demonstrated. Ridge waveguides have been prepared by precise cutting using a diamond microsaw. Spectral dependences of the SHG power and intensity distributions in the near field of second harmonic and pump radiations have been measured. The results obtained indicate good prospects of designing tunable laser radiation sources in the visible range due to the SHG in ridge waveguides formed in periodically poled nonlinear crystals under semiconductor laser pumping.

We present a semiconductor disk laser (SDL) emitting at the wavelength of 1.3 μm. The active region of the SDL comprises InAs quantum dots (QDs) that are embedded into InGaAs quantum wells (QWs). An output power over 200 mW is obtained at 15°C, which represents the highest output power reported from QD-based SDLs in this wavelength range. The results demonstrate the feasibility of QD-based gain media for fabricating SDLs emitting at 1.3 μm.

We present a compact, all-room-temperature continuous-wave laser source in the visible spectral region between 574 and 647 nm by frequency doubling of a broadly tunable InAs/GaAs quantum-dot external-cavity diode laser in a periodically poled potassium titanyl phosphate crystal containing three waveguides with different cross-sectional areas (4×4, 3×5, and 2  μm×6  μm). The influence of a waveguide’s design on tunability, output power, and mode distribution of second-harmonic generated light, as well as possibilities to increase the conversion efficiency via an optimization of a waveguide’s cross-sectional area, was systematically investigated. A maximum output power of 12.04 mW with a conversion efficiency of 10.29% at 605.6 nm was demonstrated in the wider waveguide with the cross-sectional area of 4  μm×4  μm.

We study the peculiarities of the formation of Bessel beams in semiconductor lasers with a high propagation parameter M2. It is shown that the propagation distance of the Bessel beam is determined by the divergence of the quasi-Gaussian beam with high M2 rather than the geometric parameters of the optical scheme. It is demonstrated that technologically inevitable rounding of the axicon tip leads to a significant increase in the transverse dimension of the central part of the Bessel beam near the axicon.

We present an overview of recent advances in generation of non-diffracting (Bessel) beams from surface-emitting lasers, such as electrically and optically pumped VECSELs, and discuss their applications in optical trapping/tweezing and manipulation of micromachines. Our experiments on VECSEL-generated watt power level Bessel beams with central lobe diameters of a few to tens micrometers suggest that the semiconductor surface-emitting lasers are the best candidates for replacement of gas and solid-state counterparts for power-demanding applications in optical manipulation.

We report on demonstration of non-diffracting (Bessel) beams from Electrically Pumped Vertical External Cavity Surface Emitting Lasers (EP-VECSELs), with output powers ranging up to hundreds of milliwatts and central lobe diameters of 10-100 m with propagation lengths up to few tens of centimeters. To our knowledge, this is the best result for Bessel beams generated from semiconductor light sources and is comparable to that achievable from vibronic lasers.

This paper describes the results of a histological study of the internal organs of the plaicePleuronectes obscurusfrom a polluted part of Amurskii Bay, Sea of Japan. A variety of histomorphological alterations were found in the gills and liver, while the kidney and spleen were affected to a lesser degree. The most frequent lesions in gills were edemas of gill lamellae, epithelial detachments, fusions of the secondary lamellae, hypertrophies and hyperplasias of respiratory cells, pigment accumulations, the presence of parasites, increased quantities of mucous cells, lymphocyte infiltrations, and disturbances of blood circulation. Characteristic morphological changes in the liver were lipid and hydropic dystrophy, pigment accumulation, and the presence of regenerative and necrotic foci. Telangiectasia, globate filaments, and xenomas were found in the gills ofP. obscurusfor the first time. These morphological alterations appear to be a result of the chronic effect of pollution in Amurskii Bay.

The special features resulting from the photon drag of intraband photoconductivity carriers in variable-gap semiconductors with intrinsic type conductivity and a forbidden-gap width which varies linearly with distance are considered theoretically. An analysis is made of the dependence of the photoconductivity on the gradient of the forbidden-gap width for different surface recombination rates and sample thicknesses. It is shown that a spatial inhomogeneity of the band structure in semiconductors enables their photoconductivity to be substantially increased, especially in the case of thick samples.

In this paper the characteristics of the helical instability in a semiconductor plate in which the width of the forbidden band varies linearly over the thickness are studied theoretically. The dependences of the threshold product of the external fields and the wave vector which arise at the threshold of instability of the disturbances on the gradient of the width of the forbidden band and the orientations of the external electric and magnetic fields are calculated. It is shown that nonuniformity of the band structure can result in a lower excitation threshold of instability than in the case of a homogeneous-band semiconductor.

Features of current transfer in variable band-gap structures with impurity and intrinsic conductivities are investigated using numerical modelling. It is shown that in impurity-variable band-gap structures, the flow of current is accompanied by distributed injection and extraction phenomena which lead to the formation of nonlinear and asymmetrical current-voltage characteristics. In the case of variable band-gap structures with intrinsic conductivity, the redistribution of the carriers is only slight, and the current-voltage characteristic is close to ohmic.

Manganese has a significant influence on the structure formation and properties of 20GL steel. With a content of more than 0.6% manganese promotes the formation of a lamellar bainitic structure consisting of ferrite and microzones of residual austenite or products of its decomposition. In individual cases these microzones may be competely isolated from one another but more frequently, apparently, they form a branched skeleton of ferrite grains. Such a microstructure of heterogenized ferrite grains provides a marked effect of microcomposition strengthening of steel.

A compact high-power yellow–green continuous wave (CW) laser source based on second-harmonic generation (SHG) in a 5% MgO doped periodically poled congruent lithium niobate (PPLN) waveguide crystal pumped by a quantum-dot fiber Bragg grating (QD-FBG) laser diode is demonstrated. A frequency-doubled power of 90.11 mW at the wavelength of 560.68 nm with a conversion efficiency of 52.4% is reported. To the best of our knowledge, this represents the highest output power and conversion efficiency achieved to date in this spectral region from a diode-pumped PPLN waveguide crystal, which could prove extremely valuable for the deployment of such a source in a wide range of biomedical applications.

A compact picosecond all-room-temperature orange-to-red tunable laser source in the spectral region between 600 and 627 nm is demonstrated. The tunable radiation is obtained by second-harmonic generation in a periodically poled potassium titanyl phosphate (PPKTP) multimode waveguide using a tunable quantum-dot external-cavity mode-locked laser. The maximum second-harmonic output peak power of 3.91 mW at 613 nm is achieved for 85.94 mW of launched pump peak power at 1226 nm, resulting in conversion efficiency of 4.55%.

Abstract A specimen of the cubed snailfish, Liparis tessellatus was captured in Peter the Great Bay, Sea of Japan. The capture of L. tessellatus from this area a century after the first record is evidence that at present this species still inhabits Peter the Great Bay.