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We propose a novel approach for efficient tuning of optical properties of a high refractive index subwavelength nanoparticle with a magnetic Mie-type resonance by means of femtosecond laser irradiation. This concept is based on ultrafast photoinjection of dense (10(20) cm(-3)) electron-hole plasma within such nanoparticle, drastically changing its transient dielectric permittivity. This allows manipulation by both electric and magnetic nanoparticle responses, resulting in dramatic changes of its scattering diagram and scattering cross section. We experimentally demonstrate 20% tuning of reflectance of a single silicon nanoparticle by femtosecond laser pulses with wavelength in the vicinity of the magnetic dipole resonance. Such a single-particle nanodevice enables designing of fast and ultracompact optical switchers and modulators.

A novel method for single-step, lithography-free, and large-scale laser writing of nanoparticle-based plasmonic structures has been developed. Changing energy of femtosecond laser pulses and thickness of irradiated gold film, it is possible to vary diameter of the gold nanoparticles, while the distance between them can be varied by laser scanning parameters. This method has an advantage over the most previously demonstrated methods in its simplicity and versatility, while the quality of the structures is good enough for many applications.

The viability of a two-dimensional array of nano-sized pores in a dielectric substrate as an antireflective coating was experimentally proven. Optimization of the pore array's geometrical properties leads to a strong suppression of reflectivity. Reflection from a fused silica substrate was reduced to a minimum of 0.05%, and to less than 1% over the whole visible spectral range. Spatial dispersion in the array of pores enables broadband phase compensation for waves reflected from the coating, allowing for broadband antireflection. An array of nanopores optimized for broadband phase compensation can operate as an antireflective coating in a wider spectral range than is achievable with any homogeneous single-layer ARC.

Using two 20 mm in diameter, 1.4 mm thick, 5 at% doping Yb:YAG ceramic active elements (AEs) we reached 233 mJ at 143 Hz in the output with 70 ns, 30 mJ input pulses. According to our 3D calculations we extracted about half of the stored energy. To our knowledge, this output result is the best among all high repetition rate cryogenic pulse Yb:YAG ceramic thin disk laser systems.

Optical metasurfaces have great potential to form a platform for manipulation of surface waves. A plethora of advanced surface-wave phenomena such as negative refraction, self-collimation and channeling of 2D waves can be realized through on-demand engineering of dispersion properties of a periodic metasurface. In this letter, we report on polarization-resolved measurement of dispersion of plasmon waves supported by an anisotropic metasurface. We demonstrate that a subdiffractive array of strongly coupled resonant plasmonic nanoparticles supports both TE and TM plasmon modes at optical frequencies. With the assistance of numerical simulations we identify dipole and quadrupole dispersion bands. The shape of isofrequency contours of the modes changes drastically with frequency exhibiting nontrivial transformations of their curvature and topology that is confirmed by the experimental data. By revealing polarization degree of freedom for surface waves, our results open new routes for designing planar on-chip devices for surface photonics.

In this paper we study theoretically influence of group 3 and group 5 deposition rates on A3B5 nanowires (NWs) self-catalyzed vapor–liquid–solid (VLS) growth. Our self-consistent approach allows numerical calculation of chemical potential difference of the growth species, group 5 atomic concentration in the droplet and NW elongation rate for two-component system depending on deposition rates. It is found that chemical potential difference tends to saturation with increasing group 5 deposition rate (J 5), while increase of group 3 deposition rate (J 3) leads to its logarithmic growth. Two growth regimes are distinguished depending on relation between the deposition rates: high J 3 and low J 5 leads to adsorption-limited NW growth and in the opposite case nucleation-limited regime occurs. Nanowire elongation rate increases linearly with group 3 deposition rate in nucleation-limited regime. Further increase of the deposition rate leads to saturation of the growth rate in adsorption-limited regime. On the contrary, elongation rate grows linearly with group 5 deposition rate in adsorption-limited regime with slower linear growth in nucleation-limited regime.

Plasmonic nanoparticles coupled with metallic films forming nanometer scale cavities have recently emerged as a powerful tool for enhancement of light-matter interaction. Despite high efficiency for sensing and light emission, such nanocavities exhibit harmful and uncontrolled optical heating which limits the ranges of light intensities and working temperature. In contrast to plasmonic nanoparticles, all-dielectric counterparts possess low Ohmic losses, high temperature stability along with a strong temperature-dependent Raman response. Here, we demonstrate that a silicon nanoparticle coupled with a thin gold film can serve as a multifunctional metal-dielectric (hybrid) nanocavity operating up to 1200 K. Resonant interaction of light with such nanocavity enables molecular sensing, heat-induced molecular events (protein unfolding), and their real-time tracing with a nanoscale thermometry through the monitoring enhanced Raman scattering both from the nanoparticle and analyzed molecules. We model numerically the thermo-optical properties of the hybrid nanocavity and reveal two alternative regimes of operation - with and without strong optical heating while other functionalities are preserved. We believe that the concept of the multifunctional hybrid nanocavities holds great potential for diverse photochemical and photophysical applications.

We proposed a numerical model of the Gunn diode and resonant diode based on a single nitride nanowire. Important model parameters needed for development of the considered devices, namely layers thickness, composition and doping level were evaluated. It has been shown theoretically that the single GaN nanowire based Gunn diode is capable to operate in over 1 THz frequency regime.

We report on emission properties of single-photon sources of visible light, based on InAs/AlGaAs, CdTe/ZnTe, and CdSe/ZnSe quantum dot (QD) heterostructures grown by molecular beam epitaxy. For all types of QDs, the studies performed by micro-photoluminescence and photon correlation spectroscopies demonstrated the single-photon nature of emission with typical values of the second-order correlation function g (2)(0) less than 0.2 and allowed evaluation of sub-microsecond kinetics of blinking governed by local charging effects.

Silicon and aluminium nitrides, commonly used as buffer layers for GaN growth on Si are wide gap insulators, preventing barrier free charge-carrier transport across the heterojunction and limiting the functionality of GaN-on-silicon technology. In this work we explore possibility of direct growth of GaN on Si nano-heterostructures by PA-MBE with use of Ga-nanodroplets as seeds. It is demonstrated that use of seeding layer can result in formation of Y-shaped planar GaN nanoparticles (GaN tripods) along with commonly observed GaN nanowires. Growth mechanism, morphology and structural characterization of GaN/Si nano-heterostructures is discussed.

We investigate electrical characteristics of GaN, GaAs and GaP NWs which are grown with MOCVD and MBE. We developed measurement technique and it allows to determine the required properties of the structures.

Two multi-pass optical schemes of a disk laser amplifier have been proposed. Different variants of both the schemes with the smallest amount of optical elements and a lens in the active element taken into account have been calculated. For 64 passes of radiation through the active element, the average power of ∼50 W with ∼10% optical-to-optical efficiency in a pulse-periodic regime with a repetition rate of 10 kHz and a pulse duration of 2 ns was obtained at the amplifier output. The small signal gain amounted to 200.

Surface electromagnetic waves are characterized by the intrinsic spin-orbit interaction which results in the fascinating spin-momentum locking. Therefore, directional coupling of light to surface waves can be achieved through chiral nanoantennas. Here, we show that dielectric nanoantenna provides chiral response with strong spectral dependence due to the interference of electric and magnetic dipole momenta when placed in the vicinity of the metal-air interface. Remarkably, chiral behaviour in the proposed scheme does not require elliptical polarization of the pump beam or the geometric chirality of the nanoantenna. We show that the proposed ultracompact and simple dielectric nanoantenna allows for both directional launching of surface plasmon polaritons on a thin gold film and their demultiplexing with a high spectral resolution.

We perform complex investigation of the distribution of electromagnetic fields in the vicinity of an array of silver nanoantennas, which can operate as an efficient light trapping structure in the visible spectral range. In theory, this array should support unusual collective modes that possess an advantageous distribution of local electric fields, ensuring both strong field localization beneath nanoantennas and a low level of optical losses inside the metal. Using an aperture-type near-field scanning optical microscope (NSOM), we obtain near-field patterns that show excellent agreement with the NSOM signal, directly reconstructed from rigorous numerical simulations using an approach based on the electromagnetic reciprocity theorem. The agreement between theory and experiment allows us to claim the first-time experimental verification of the existence of collective modes with such properties in an array of silver nanoantennas. The confirmation of this physical phenomenon opens the door to a new class of light-trapping structures for photovoltaics.

Domino modes are highly-confined collectivemodes that were first predicted for a periodic arrangement of metallic parallelepipeds in far-infrared region. The main feature of domino modes is the advantageous distribution of the local electric field, which is concentrated between metallic elements (hot spots), while its penetration depth in metal is much smaller than the skin-depth. Therefore, arrays of non-resonant plasmonic nanoantennas exhibiting domino modes can be employed as broadband light trapping coatings for thin-film solar cells. However, until now in the excitation of such modes was demonstrated only in numerical simulations. Here, we for the first time demonstrate experimentally the excitation of optical domino modes in arrays of non-resonant plasmonic nanoantennas. We characterize the nanoantenna arrays produced by means of electron beam lithography both experimentally using an aperture-type near-field scanning optical microscope and numerically. The proof of domino modes concept for plasmonic arrays of nanoantennas in the visible spectral region opens new pathways for development of low-absorptive structures for effective focusing of light at the nanoscale.

Micro disks and micro rings with various active region and design are studied. Lasing up to 100°C is demonstrated in 2 µm micro rings with InAs/InGaAs quantum dots. A technique for selecting modes in micro disk lasers is presented.

Thin-rod Yb:YAG active element is investigated in the terms of thermal effects, gain, lasing and scalability through the theoretical and experimental analysis. Low temperature, great gain and huge thermal lens are found in the thin rod. Lasing with 6 W average power and 45 % slope efficiency is obtained. Keywords—Yb:YAG, single crystal fiber, thermal effects. Thin-rod Yb:YAG active element (AE) or “single crystal fiber” is a new and perspective geometry for high average and peak power applications [1]. It’s less than 1 mm diameter rod that provides total-internal-reflection pump guiding while signal passes through it free (without any reflections). This AE is ideologically close to the fiber and allows to reach high gain and high average power. But free passing of the amplified signal through the AE allows to increase AE aperture and overcome the main problem of the pulsed fiber lasers – optical breakdown at high peak power. In the work [1] 1 mJ 10 kHz femtosecond amplifier was demonstrated. Fig. 1. Cooling and pumping schemes for the thin-rod AE and the laser cavity geometry. In this work thermal and laser characteristics of the thin-rod Yb:YAG AE with 1 % doping, 1 mm diameter, 1.7 mm length are investigated. Thin-rod AE is made from the Yb:YAG single crystal grown by the Czochralski method. Temperature distribution, thermal-induced phase distortion of laser radiation after double pass through the AE, small signal gain (SSG) and lasing are investigated theoretically and experimentally. Numerical model used for theoretical analysis is described in [2] in details. Cooling and pumping schemes as well as laser cavity geometry are shown at Fig. 1. Calculations and experiments showed that temperature inside the AE is very low that is important for Yb-doped crystals. Temperature increases by 5 0C at 40 W absorbed pump power. Thermal induced phase distortions after double pass through the AE are well approximated by parabola. Thermal lens optical power is high. It reaches 10 1/m at 40 W absorbed pump power. SSG after double pass through the AE reaches value 4 at 36 W absorbed pump power that agrees well with the calculation (Fig. 2 (a)). Using a longer rod with higher pump power and double pass pumping scheme leads to significantly gain increasing. With 3 cm length AE at 270 W absorbed pump power SSG reaches 5*104 whereas temperature remains low (12 0C) but thermal lens becomes huge (70 1/m). Thus strong thermal lensing should be considered as the main problem of thin-rod geometry. This deleterious effect can be decreased by using of the laser materials with weak thermal lensing and by optimization system parameters to reduce thermal lens influence on the signal spot diameter in the AE. Lasing with the 6 W average power and 45 % slope efficiency is achieved (Fig. 2 (b)). The further power scaling was limited by the available pump power. Fig. 2. (a) Measured and calculated small signal gain after double pass through the AE (b) laser output power. So thin-rod amplifiers may be well candidate to scale pulsed fiber lasers up to 100 W average power and 1 mJ energy level. Soon we will start to amplify radiation of the commercially available 300 fs fiber laser to sub-mJ energy level at 100 kHz repetition rate in the thin-rod amplifier.

Thin-disk laser on the basis of the composite Yb:YAG/YAG active element with 30W average power and 50 % slope efficiency is developed. Investigations of thermal effects in active element showed the perfect laser scalability to the kilowatt power range. Keywords—thin-disk laser; Yb:YAG, composite active element, anti-ASE cap, thermal effects Today the average power of thin-disk lasers with one active element (AE) and excellent beam quality is limited at onekilowatt level. The major problems that limit further laser’s scalability are the thermal effects in AE and amplified spontaneous emission (ASE). The perspective way to decrease ASE influence is to use the composite Yb:YAG/YAG AE (Yb:YAG thin disk and YAG thick disk coupled by end faces). It’s used in cryogenic lasers and in edge-pumped wide-aperture lasers but it has never used in ordinary thin-disk laser scheme with end-pumping. In this work thin-disk laser with the composite Yb:YAG/YAG AE is realized for the first time to our knowledge. Thermal effects in AE and power scalability are investigated and 30W average power with 50 % slope efficiency is achieved. Fig. 1. (a) AE Cooling scheme (b) Experimental and calculated thermal induced phase distortion after V-pass through the AE. Dashed gray line – experiment with pump spot diameter (D) = 1.2 mm and pump power (P) = 13 W; solid black line – calculation D = 1.2 mm, P = 13 W; solid gray line – calculation D = 3 mm, P = 82 W; dashed black line – calculation D = 6 mm, P = 328 W. Composite AE is made by the original thermal diffusion bonding method [1]. Laser head with the effective cooling system end multipass pump system is constructed. Cooling scheme is shown at the (Fig. 1 (a)). Heat transfer coefficients between AE and heatsink and between heatsink and water are measured. Temperature distribution, small signal gain and phase distortion of laser radiation after V-pass through the AE are investigated theoretically and experimentally. Numerical model used for theoretical analysis is described in [2] in details. Calculations showed that undoped cap decreases AE maximum temperature in 1.6 times that allows to increase small signal gain. Investigation of phase distortion of laser radiation shows that at any pump power and any pump spot diameter thermal lens are well approximated by parabola and isn’t contains any aberrations (Fig.1 (b)). In addition parabolic thermal lens optical power decreases with the laser power scaling (pump spot diameter increasing with the constant pump intensity). It means that YAG cap removes aberration concerned with pump edges and gives thin-disk lasers the chance to overcome existing power limit. Fig. 2. (a) Output characteristics of the thin-disk laser with Yb:YAG/YAG AE (b) laser photo. Laser with V-shaped multimode resonator is constructed and 30 W average power with 50 % slope efficiency is achieved. In near future it will be scaled to the higher average power.

We review methods and instruments for micromanipulation in electron microscopes. This kind of manipulation allows handling of individual micro- and nanoobjects with nanometer precision. Most known micromanipulation technique in an electron microscope is mechanical (or contact) manipulation. In this case positioning of an object is performed either with a needle-shaped probe tip or with a microgripper attached to a micromanipulator, while the electron microscope serves as an imaging tool. The other possibility is non-contact manipulation which is based on intrinsic features of the electron microscope. For instance an electron beam could charge illuminated objects which may cause their motion resulted from electrostatic interaction. Another feature is generation of electromagnetic field by passing electrons; this causes polarization of the object and therefore its movement. The review consists of four sections. In the first section we describe forces which act on a supported particle under electron beam illumination. Second part is dedicated to mechanical manipulation where we review various commercial and hand-made systems. In particular, we pay special attention to non-standard manipulation techniques (such as automatic manipulation) or investigation of mechanical properties of micro- and nanoobjects (adhesion, hardness, friction) using micromanipulators. The third and forth parts describe electrostatic and electromagnetic manipulation methods, respectively. These methods are much less known and the number of publications related to them is quite limited, therefore we describe each work in details.

The laser pulse amplification was investigated numerically with accounting of temporal and spatial profiles under various pulse parameters. It was shown that using of multi-pass amplifiers allows increasing efficiency and reducing temporal profile distortion.

During thin-disk multipass amplifier with composite Yb:YAG/YAG active element development laser head was constructed, thermal-induced phase distortion were investigated, high small signal gain was achieved and numerical simulation of pulse amplification was performed.

We suggest a new class of hyperbolic metamaterials for THz frequencies based on multilayer graphene structures. We calculate the dielectric permittivity tensor of the effective nonlocal medium with a periodic stack of graphene layers and demonstrate that tuning from elliptic to hyperbolic dispersion can be achieved with an external gate voltage. We reveal that such graphene structures can demonstrate a giant Purcell effect that can be used for boosting the THz emission in semiconductor devices. Tunability of these structures can be enhanced further with an external magnetic field which leads to the unconventional hybridization of the TE and TM polarized waves.

Theoretical and experimental analysis of small signal gain, phase and polarization distortion of laser radiation in end-pumped Yb:YAG thin disk and composite Yb:YAG/YAG active elements is performed at room and cryogenic temperature under non-lasing conditions.

The concept of the thin-tapered-rod Yb:YAG amplifier with waveguide pumping is proposed and implemented. It is shown that such an amplifier demonstrates considerably higher small signal gain and is less affected by thermal effects than the thin-rod ("single-crystal fiber") amplifier. In the developed amplifier, a small signal gain as high as 23 per pass is achieved.

Fabrication and study of specialized single nanowhisker probes are performed for high-precision investigation of elements such as nanospheres and nanorods using the atomic force microscopy. It was found that single nanowhisker probe significantly increases the resolution and contrast of images obtained in the semi-contact mode. Furthermore, the roughness analysis and adhesion forces are investigated in contact mode to comprehensively characterize properties of nanospherical and nanorod electronic structures.

Here, the novel concept of asymmetric metal-dielectric (hybrid) nanoparticles is proposed. The experimental data and the results of numerical simulation of the optical properties of hybrid nanostructures are presented. The change of their optical response after fs- laser modification is shown. The possibility of manipulating Fano resonance in hybrid oligomers by the gold nanoparticles reshaping is demonstrated.

We propose a novel strategy for self-adjusted fabrication of large-scale array of resonant silicon nanoparticles (metasurface) on a thin silicon film. The self-adjusting mechanism is based on the effect of resonant nanogratings formation under intense multishot femtosecond irradiation of a thin silicon film. The resulting metasurfaces allow for generation of ultraviolet laser pulses at a wavelength of 270 nm with conversion efficiency up to 10-6 and high peak (≈100 kW/sm2) and average power (≈1.5 μW). Such high peak power from ultrathin metasurface makes the generated UV pulses applicable in a wide range of applications: precise nanolithography, ultrafast photoexcitation etc.

In this work we study growth of semiconductor GaN nanowires (NWs) on Si(111) substrates by means of molecular beam epitaxy. We demonstrate that the substrate temperature affects both the surface density and growth rate of the synthesized NWs. It was determined that at a fixed flux of nitrogen equal to 1.3 cm3/min the maximum growth rate of NWs is ~ 38 nm/h at a substrate temperature — 800 oC. It was also found that the growth rate of NWs on the substrates treated with the oxide removal procedure is half the growth rate on substrates covered with oxide, while their surface density is twice higher in the first case. In addition we have studied influence of Ga flux on NWs formation.

Far field emission of optically pumped QD microdisk lasers with spherical Si nanoantenna placed on the top surface of microdisk is studied theoretically and experimentally. The interaction of the whispering gallery mode microdisk resonator with properly designed and positioned Si nanospheres results in improvement of light outcoupling and directed emission.

We develop a novel method of core-shell nanoparticles fabrication based on laser ablation of multilayer thin films using femtosecond laser pulses. Transmission electron microscopy proves that the obtained structures have Si and Au separated parts. We theoretically show that the combination of high refractive index dielectric and plasmonic nanoparticles shows possibility of interplay between magnetic optical responses and plasmon resonances. This opens a possibility to manipulate by both scattering power pattern and local optical field enhancement via precise engineering of the core/shell nanoparticles.

We separated AlN/SiC film from Si substrate by chemical etching of the AlN/SiC/Si heterostructure. The film fully repeats the size and geometry of the original sample and separated without destroying. It is demonstrated that a buffer layer of silicon carbide grown by a method of substitution of atoms may have an extensive hollow subsurface structure, which makes it easier to overcome the differences in the coefficients of thermal expansion during the growth of thin films. It is shown that after the separation of the film from the silicon substrate, mechanical stresses therein are almost absent.

We researched electrical characteristics of GaN nanowires (NWs) grown by MOCVD through solid titanium film. The technology of creating the ohmic contacts and MESFET structure on single NWs has been developed. The optimal annealing temperature of contacts has been found and conductivity structure, the free carrier concentration and mobility has been evaluated.

Nanomechanical system (NMS) based on amorphous carbon nanowhiskers localized on the top of tungsten tip were fabricated and investigated. The whiskers were grown in the scanning electron microscope (SEM) chamber using focused electron beam technique. The manipulation of SiO2 and TiO2 nanospheres was provided in SEM by means of dielectrophoretic force. Oscillation trajectories and amplitude-frequency characteristic of the oscillator were visualized at low pressure using a scanning electron microscope. The estimation of mass sensitivity of NMS was conducted.

Electrical properties of single GaN nanowires grown by means of molecular beam epitaxy with N-plasma source were studied. Ohmic contacts connected to single n-type GaN wires were produced by the combination of electron beam lithography, metal vacuum evaporation and rapid thermal annealing technique. The optimal annealing temperature to produce ohmic contacts implemented in the form of Ti/Al/Ti/Au stack has been determined. By means of 2-terminal measurement wiring diagram the conductivity of single NW has been obtained for NWs with different growth parameters. The method of MESFET measurement circuit layout of single GaN nanowires (NWs) has been developed. In accordance with performed numerical calculation, free carriers' concentration and mobility of single NWs could be independently estimated using MESFET structure.

The above question is frequently asked by theorists who are interested in graphene as a model system, especially in context of relativistic quantum physics. We offer an experimental answer by describing electron transport in suspended devices with carrier mobilities of several 10(6) cm(2) V(-1) s(-1) and with the onset of Landau quantization occurring in fields below 5 mT. The observed charge inhomogeneity is as low as ≈10(8) cm(-2), allowing a neutral state with a few charge carriers per entire micrometer-scale device. Above liquid helium temperatures, the electronic properties of such devices are intrinsic, being governed by thermal excitations only. This yields that the Dirac point can be approached within 1 meV, a limit currently set by the remaining charge inhomogeneity. No sign of an insulating state is observed down to 1 K, which establishes the upper limit on a possible bandgap.

A compensation scheme for thermally induced birefringence in Faraday isolators is proposed. With the use of this scheme a 36-fold increase of the isolation degree was attained in experiment. A comparative analysis of the considered scheme and the earlier Faraday isolator schemes with high average radiation power is performed. A method for optimizing the earlier Faraday isolator scheme with birefringence compensation is developed.

We predicted and experimentally studied strong statistical dispersion of thermal lensing and thermally induced depolarization in ceramics. This effect is specific to ceramics and has no analogues either in glasses or in single crystals.

A novel method for single-step, lithography-free, and large-scale laser writing of arrays of metallic (Au) and semiconductor (Si) nanoparticles (nanoresonators) has been developed. Changing energy of femtosecond laser pulses and film thickness it is possible to vary diameter of the nanoparticles, while the distance between them can be varied by laser scanning parameters. This method has an advantage over the most previously demonstrated methods in its simplicity and versatility, while the quality of the structures is good enough for many applications.

It is shown experimentally that the irradiation of thin Al and Au films of thickness 50 to 100 nm on a silicate glass surface by electrons results in effects that differ principally depending on the electron energy. For energies of 5 to 15 keV, the irradiation leads to an increase in the film thickness throughout the irradiated zone and a decrease in the thickness in the surrounding area. For an energy of 25 keV, the irradiation leads to dissolving the Au film in glass in the irradiated zone. The mechanisms of the observed effects are discussed.

High refractive index subwavelength dielectric nanoresonators, which support both electric and magnetic optical resonances, are a promising platform for many nanophotonic applications. However, the resonant properties of the nanoresonators are highly sensitive to defect concentrations. Therefore, to maintain low defect concentrations, it has generally thought inevitable to use crystalline precursor materials for nanoresonator fabrication. Here, we show that it is possible to fabricate crystalline (low-loss) resonant silicon nanoparticles by femtosecond laser ablation from amorphous (high-loss) silicon thin films. The crystallinity of the fabricated nanoparticles is proven by means of Raman spectroscopy and electron transmission microscopy, and their optical resonant properties are studied by means of dark-field optical spectroscopy and discrete-dipole simulations.

Modeling of photovoltaic properties of multi-junction solar cells integrated on a Si substrate with an array of GaN nanowires as a top emitter has been carried out. Very good antireflection properties of the structure are demonstrated theoretically: the calculated reflectance is lower than 3% for both GaN nanowires/Si and GaN nanowires on GaPN/Si cells. According to our simulations, basic GaN nanowires on Si cell with optimised parameters (doping and NWs morphology) provides energy conversion efficiency of 20%. The approach demonstrates high potential of the GaPN(As)-based multi-junction lattice matched with Si solar cells using an array of GaN nanowires as a top emitter.

In this letter we investigate photovoltaic properties of GaN nanowires (NWs) – Si substrate heterostructure obtained by molecular beam epitaxy (MBE). Antireflection properties of the NW array were studied theoretically and experimentally to show an order of magnitude enhancement in antireflection comparing to the pure Si surface (2.5% vs. 33.8%). In order to determine optimal morphology and doping levels of the structure with maximum possible efficiency we simulated it's properties using a finite difference method. The carried out simulation showed that a maximum efficiency should be 20%.

Creation and study of specialized nanowhisker probes with magnetic coating are performed for high-precision imaging of various objects by means of atomic force and magnetic force microscopy. Thin layers of Ni and Co are deposited on the surface of nanowhisker structures to perform visualization of magnetic fields on the sample surface, in particular, structure of pits on a hard disk drive (HDD). It is revealed that probes with nanowhisker structures covered with magnetic coating due to their high aspect ratio demonstrate a higher spatial resolution and contrast of magnetic fields visualization in comparison with standard magnetic probes.

Nanomechanical oscillators (NMO) on the basis of crystalline W (tungsten) microwhiskers and amorphous C (carbon) nanowhiskers localized on the top of W tips are created and studied. Trajectories of single and coupled resonant oscillations are visualized, resonant frequencies and quality factor of NMO are determined. Trajectories of coupled resonant oscillations of NMO are simulated. Calculation results are qualitatively in agreement with the experimental data.