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Of all publications in the section: 15
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Article
Kryzhanovskaya N., Polubavkina Y., Moiseev E. et al. Journal of Applied Physics. 2017. Vol. 121. No. 4. P. 043104.

We present detailed studies of optically pumped InAs/InGaAs quantum dot based racetrack microlasers with 3.5-μm bend radius operating at room temperature. Q factor over 8000 and room temperature threshold power in the mW-range were achieved in the racetrack microlasers with straight section length ranging from 0 to 4 μm. A systematic investigation of the influence of the racetrack straight section length on spatial distribution of optical modes is presented. The microcavity eigenmodes and electromagnetic field distribution calculated by means of three-dimensional numerical simulation demonstrate a good agreement with the experimental results obtained by micro-photoluminescence and scanning near-field optical microscopy. The racetracks demonstrate zigzagging behavior of the modes inside the cavity and the energy switching between the radial maxima in second-order modes. Higher-order modes are found to be suppressed in micro-photoluminescence spectra.

Added: Oct 1, 2020
Article
Khisameeva A., Shchepetilnikov A., Muravev V. et al. Journal of Applied Physics. 2019. Vol. 125. P. 154501-1-154501-5.

The terahertz photoconductivity of 100 μm and 20 μm Hall bars fabricated from narrow AlAs quantum wells (QWs) of different widths is investigated in this paper. The photoresponse is dominated by collective magnetoplasmon excitations within the body of the Hall structure. We observed a radical change of the magnetoplasma spectrum measured precisely for AlAs QWs of widths ranging from 4 nm to 15 nm. We have shown that the observed behavior is a vivid manifestation of valley transition taking place in the two-dimensional electron system. Remarkably, we show that the photoresponse for AlAs QWs with a width of 6 nm features two resonances, indicating simultaneous occupa- tion of strongly anisotropic X xy valleys and isotropic X z valley in the QW plane. Our results pave the way for realizing valley-selective layered heterostructures, with potential applications in valleytronics.

Added: Jun 11, 2019
Article
Тарасов М., Соболев А., Гунбина А. et al. Journal of Applied Physics. 2019. Vol. 125. P. 174501.
Added: Nov 22, 2019
Article
Starikov S. V., Pisarev Vasily V. Journal of Applied Physics. 2015. Vol. 117. P. 135901.

In this work, the femtosecond laser pulse modification of surface is studied for aluminium (Al) and gold (Au) by use of two-temperature atomistic simulation. The results are obtained for various atomistic models with different scales: from pseudo-one-dimensional to full-scale three-dimensional simulation. The surface modification after laser irradiation can be caused by ablation and melting. For low energy laser pulses, the nanoscale ripples may be induced on a surface by melting without laser ablation. In this case, nanoscale changes of the surface are due to a splash of molten metal under temperature gradient. Laser ablation occurs at a higher pulse energy when a crater is formed on the surface. There are essential differences between Al ablation and Au ablation. In the first step of shock-wave induced ablation, swelling and void formation occur for both metals. However, the simulation of ablation in gold shows an additional athermal type of ablation that is associated with electron pressure relaxation. This type of ablation takes place at the surface layer, at a depth of several nanometers, and does not induce swelling.

Added: Apr 5, 2017
Article
Lusche R., Semenov A., Ilin K. et al. Journal of Applied Physics. 2014. Vol. 116. No. 4. P. 043906-1-043906-9.

A thorough spectral study of the intrinsic single-photon detection efficiency in superconducting TaN and NbN nanowires with different widths has been performed. The experiment shows that the cut-off of the intrinsic detection efficiency at near-infrared wavelengths is most likely controlled by the local suppression of the barrier for vortex nucleation around the absorption site. Beyond the cut-off quasi-particle diffusion in combination with spontaneous, thermally activated vortex crossing explains the detection process. For both materials, the reciprocal cut-off wavelength scales linearly with the wire width where the scaling factor agrees with the hot-spot detection model.

Added: Feb 24, 2016
Article
Omelchenko A., Petrov M., Lipovskii A. Journal of Applied Physics. 2011. Vol. 109. P. 094108.

This paper concerns to rigorous analysis of the electrodiffusion problem arising during electric field treatment of glasses and glass metal nanocomposites (e.g. glass poling effect). The strict solution of the carrier drift equations for two type ions differing in mobility and diffusioncoefficient is obtained. This solution allows finding out the duration of space charge buildup and determining the limits of electroneutrality approximation. The rigorous solution demonstrates a good agreement with experimental data. The results of numerical solution are discussed as well.

Added: Sep 17, 2018
Article
Kryzhanovskaya N., Polubavkina Y., Moiseev E. et al. Journal of Applied Physics. 2018. Vol. 124. No. 16. P. 163102.

High-index dielectric (Si) nanoantennas providing outcoupling of light from InAs/Ga(Al)As quantum dot (QD) microdisk lasers have been designed. The spatial distribution of light emitted from optically pumped QD microdisk lasers with a single Si spherical nanoantenna placed on the top surface of the microdisk was studied experimentally by confocal optical microscopy. Dependences of the emission intensity on the size and position of the Si nanoantenna were investigated. It was found that the laser mode to be outcoupled can be selected by choosing the nanosphere position with respect to the mode electromagnetic field maximum. Optimization of the Si nanoantenna parameters resulted in a 23-fold increase of the emission intensity at the location of the Si nanoantenna (whereas the total intensity enhanced 4 times) compared to the emission intensity from the initial microdisk laser without significant deterioration of the resonator quality factor.

Added: Oct 1, 2020
Article
Kryzhanovskaya N., Moiseev E., Zubov F. et al. Journal of Applied Physics. 2019. Vol. 126. No. 6. P. 063107.

The energy-to-data ratio (EDR) was evaluated for quantum-dot based microdisk laser directly modulated without external cooling. The experimental values of EDR decrease with decreasing diameter of the microdisk and reach 1.5 pJ/bit for the smallest diameter under study (10.5 μm). In larger microdisks (with a diameter greater than 20 μm), the EDR varies in proportion to the square of the diameter. If this relationship were true for smaller microdisks as well, an EDR value of about 100 fJ would be achieved with a diameter of 4 μm. The observed deviation of EDR from the quadratic dependence on the diameter is associated with an increase in the threshold current density in smaller devices, which in turn may be caused by the contribution of nonradiative recombination on the microresonator sidewalls formed by deep etching.

Added: Oct 1, 2020
Article
N. V. Kryzhanovskaya, Zhukov A E. Journal of Applied Physics. 2019. Vol. 126. No. 6. P. 063107-1-063107-6.

The energy-to-data ratio (EDR) was evaluated for quantum-dot based microdisk laser directly modulated without external cooling. The experimental values of EDR decrease with decreasing diameter of the microdisk and reach 1.5 pJ/bit for the smallest diameter under study (10.5 μm). In larger microdisks (with a diameter greater than 20 μm), the EDR varies in proportion to the square of the diameter. If this relationship were true for smaller microdisks as well, an EDR value of about 100 fJ would be achieved with a diameter of 4 μm. The observed deviation of EDR from the quadratic dependence on the diameter is associated with an increase in the threshold current density in smaller devices, which in turn may be caused by the contribution of nonradiative recombination on the microresonator sidewalls formed by deep etching.

Added: Feb 10, 2020
Article
Kryzhanovskaya N., Moiseev E., Polubavkina Y. et al. Journal of Applied Physics. 2016. Vol. 120. No. 33. P. 233103.

We report on microdisk lasers based on GaInNAs(Sb)/GaAs(N) quantum well active region. Their characteristics were studied under electrical and optical pumping. Small-sized microdisks (minimal diameter 2.3 μm) with unprotected sidewalls show lasing only at temperatures below 220 K. Sulfide passivation followed by SiNx encapsulation allowed us achieving room temperature lasing at 1270 nm in 3 μm GaInNAs/GaAs microdisk and at 1550 nm in 2.3 μm GaInNAsSb/GaAsN microdisk under optical pumping. Injection microdisk with a diameter of 31 μm based on three GaInNAs/GaAs quantum wells and fabricated without passivation show lasing up to 170 K with a characteristic temperature of T0 = 60 K.

Added: Oct 1, 2020
Article
Norman G., Starikov S., Stegailov V. et al. Journal of Applied Physics. 2012. Vol. 112. No. 013104. P. 1-8.

We show experimentally the possibility of nanostructuring (about 20 nm) of gold surface by picosecond soft x-ray single pulse with low fluence of ~20 mJ/cm2. The nanometer-scale changes of the surface structure are due to the splash of molten gold under fluence gradient of the laser beam. In addition, the ablation process occurs at slightly higher fluence of ~50 mJ/cm2. The atomistic model of ablation is developed which reveals that the low threshold fluence of this process is due to the build-up of the high electron pressure and the comparatively low electron-ion energy relaxation rate in gold. The calculated ablation depths as a function of the irradiation fluence are in good agreement with the experimental data measured for gold surface modification with ultra-short duration soft x-ray and visible lasers.

Added: Mar 24, 2014
Article
Andrey Tyutnev, Vladimir Saenko, Renat Ikhsanov et al. Journal of Applied Physics. 2019. Vol. 126. No. 9. P. 095501(1)-095501(9).

We have investigated radiation-induced conductivity (RIC) in several low mobility common polymers as well as two with excellent charge transport characteristics. Irradiations were pulsed and continuous with constant dose rates from microseconds to seconds. Experiments were done in the small-signal mode at a relatively high electric field. To interpret the results, we performed numerical calculations based on the conventional as well as the modified Rose-Fowler-Vaisberg (RFV) models. Also, to accommodate the time-of-flight and deep trapping effects, we used an analytic formula describing strongly nonequilibrium dispersive transport at high electric fields in the presence of deep trapping. As a result, several long-standing RIC issues have been resolved. A crucial role of pulsed irradiations for polymer parameterization in terms of the RFV model has been demonstrated.

Added: Sep 4, 2019
Article
Gayduchenko I., Kardakova A., Fedorov G. et al. Journal of Applied Physics. 2015. Vol. 118. No. 19. P. 194303-1-194303-9.

Demand for efficient terahertz radiation detectors resulted in intensive study of the asymmetric carbon nanostructures as a possible solution for that problem. It was maintained that photothermoelectric effect under certain conditions results in strong response of such devices to terahertz radiation even at room temperature. In this work, we investigate different mechanisms underlying the response of asymmetric carbon nanotube (CNT) based devices to sub-terahertz and terahertz radiation. Our structures are formed with CNT networks instead of individual CNTs so that effects probed are more generic and not caused by peculiarities of an individual nanoscale object. We conclude that the DC voltage response observed in our structures is not only thermal in origin. So called diode-type response caused by asymmetry of the device IV characteristic turns out to be dominant at room temperature. Quantitative analysis provides further routes for the optimization of the device configuration, which may result in appearance of novel terahertz radiation detectors.

Added: Feb 19, 2016
Article
Caruso R., Massarotti D., Bolginov V. V. et al. Journal of Applied Physics. 2018. Vol. 123. No. 13. P. 133901-1-133901-6.

We test the effect of an external RF field on the switching processes of magnetic Josephson junctions (MJJs) suitable for the realization of fast, scalable cryogenic memories compatible with Single Flux Quantum logic. We show that the combined application of microwaves and magnetic field pulses can improve the performances of the device, increasing the separation between the critical current levels corresponding to logical "0" and "1." The enhancement of the current level separation can be as high as 80% using an optimal set of parameters. We demonstrate that external RF fields can be used as an additional tool to manipulate the memory states, and we expect that this approach may lead to the development of new methods of selecting MJJs and manipulating their states in memory arrays for various applications.

Added: Oct 24, 2018
Article
Ryzhii V., Otsuji T., Ryzhii M. et al. Journal of Applied Physics. 2016. Vol. 120. P. 044501-1 -044501-13.

We consider the carrier transport and plasmonic phenomena in the lateral carbon nanotube (CNT) networks forming the device channel with asymmetric electrodes. One electrode is the Ohmic contact to the CNT network and the other contact is the Schottky contact. These structures can serve as detectors of the terahertz (THz) radiation. We develop the device model for collective response of the lateral CNT networks which comprise a mixture of randomly oriented semiconductor CNTs (s-CNTs) and quasi-metal CNTs (m-CNTs). The proposed model includes the concept of the collective two-dimensional (2D) plasmons in relatively dense networks of randomly oriented CNTs (CNT “felt”) and predicts the detector responsivity spectral characteristics exhibiting sharp resonant peaks at the signal frequencies corresponding to the 2D plasmonic resonances. The detection mechanism is the rectification of the ac current due the nonlinearity of the Schottky contact current-voltage characteristics under the conditions of a strong enhancement of the potential drop at this contact associated with the plasmon excitation. The detector responsivity depends on the fractions of the s- and m-CNTs. The burning of the near-contact regions of the m-CNTs or destruction of these CNTs leads to a marked increase in the responsivity in agreement with our experimental data. The resonant THz detectors with sufficiently dense lateral CNT networks can compete and surpass other THz detectors using plasmonic effects at room temperatures.

Added: Oct 19, 2016