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Rukhlenko I.D.,Monash University | Rukhlenko I.D.,Saint Petersburg National Research University of Information Technologies | Kalavally V.,University of Selangor
Journal of Lightwave Technology | Year: 2014

The strength of Raman interaction between optical fields propagating through a silicon-nanocrystal waveguide is known to significantly differ from that in bulk silicon and silicon-on-insulator waveguides. Here we present the first theoretical study of continuous-wave Raman amplification in silicon-nanocrystal waveguides with improved mode confinement. By calculating numerically the mode-overlap factors and effective refractive indices of the pump and Stokes fields, we analyze how the maximal Stokes intensity and the optimal waveguide length depend on the cross-section parameters of the composite, density of silicon nanocrystals, and input conditions. In particular, we demonstrate that the maximal Stokes intensity peaks at certain waveguide height and volume fraction of silicon nanocrystals for fixed input intensities, and at certain waveguide width for fixed input powers. These features enable simple performance optimization of Raman amplifiers and lasers based on silicon nanocrystals. © 2013 IEEE.

Baimuratov A.S.,Saint Petersburg National Research University of Information Technologies | Turkov V.K.,Saint Petersburg National Research University of Information Technologies | Rukhlenko I.D.,Monash University | Fedorov A.V.,Saint Petersburg National Research University of Information Technologies
Optics Letters | Year: 2012

Nonspherical semiconductor nanocrystals (NCs) may exhibit strongly anisotropic photoluminescence due to the intraband transitions, whose matrix elements depend critically on the envelope wave functions of the confined electrons and holes. We demonstrate that this anisotropy may be used as the basis for a new type of polarization spectroscopy, enabling one to reliably determine the shape and spatial orientation of individual NCs, as well as providing important information on the symmetry of quantum states involved in optical transitions. © 2012 Optical Society of America.

Baimuratov A.S.,Monash University | Rukhlenko I.D.,Monash University | Fedorov A.V.,Saint Petersburg National Research University of Information Technologies
Optics Letters | Year: 2013

Supercrystals made of periodically arranged semiconductor quantum dots (QDs) are promising structures for nano-photonics applications due to almost unlimited degrees of freedom enabling fine tuning of their optical responses. Here we demonstrate broad engineering opportunities associated with the possibility of tailoring the energy bands of excitons in two-dimensional quantum-dot supercrystals through the alteration in the QD arrangement. These opportunities offer an unprecedented control over the optical properties of the supercrystals, which may be used as a versatile material base for advanced photonics devices on the nanoscale. © 2013 Optical Society of America.

Agency: European Commission | Branch: H2020 | Program: RIA | Phase: FETOPEN-01-2016-2017 | Award Amount: 4.58M | Year: 2017

M-Cube aims at changing the paradigm of High-Field MRI and Ultra High-Field antennas to offer a much better insight on the human body and enable earlier detection of diseases. Our main objective is to go beyond the limits of MRI clinical imaging and radically improve spatial and temporal resolutions. The clinical use of High-field MRI scanners is drastically limited due to the lack of homogeneity and to the Specific Absorption Rate (SAR) of the Radio Frequency (RF) fields associated with the magnetic resonance. The major way to tackle and solve these problems consists in increasing the number of active RF antennas, leading to complex and expensive solutions. M-Cube solution relies on innovative systems based upon passive metamaterial structures to avoid multiple active elements. These systems are expected to make High-Field MRI fully diagnostically relevant for physicians. To achieve these expectations, M-Cube consortium will develop a disruptive metamaterial antenna technology. This we will able us to tackle both the lack of homogeneity and SAR barriers. Metamaterials are composite structured manmade materials designed to produce effective properties unavailable in nature (e.g. negative optical index). They allow us to tailor electromagnetic waves at will. Thus, the scientifically ambitious idea is to develop antennas based on this unique ability for whole body coil. This technological breakthrough will be validated by preclinical and clinical tests with healthy volunteers. M-Cube gathers an interdisciplinary consortium composed of academic leaders in the field, eight universities, and two promising SMEs. Physicists, medical doctors and industrial actors will work closely all along the implementation of the project to guarantee the success this novel approach, a patient-centered solution which will pave the way for a more accurate diagnosis in the context of personalized medicine and will enable to detect a disease much earlier that is currently possible.

Agency: European Commission | Branch: H2020 | Program: RIA | Phase: ICT-30-2015 | Award Amount: 9.43M | Year: 2016

The Internet of Things (IoT) brings opportunities for creating new services and products, reducing costs for societies, increasing the service level for the citizens in a number of areas, and changing how services are sold and consumed. Despite these opportunities, current information system architectures create obstacles that must be addressed for leveraging the full potential of IoT. One of the most critical obstacles are the vertical silos that shape todays IoT because they constitute a serious impediment to the creation of cross-domain, cross-platform and cross-organisational applications and services. Those silos also hamper developers from producing new added value across multiple platforms due to the lack of interoperability and openness. bIoTope provides the necessary Standardized Open APIs for enabling horizontal interoperability between silos. Such horizontal interoperability makes it possible to develop Systems of Systems where cross-domain information from platforms, devices and other information sources can be accessed when and as needed. bIoTope-enabled Systems can seamlessly exploit all available information, which makes them smart in the sense that they can take or propose the most appropriate actions depending on the current Users or Objects Context/Situation, and even learn from experience. bIoTope capabilities lay the foundation for open innovation ecosystems where companies can innovate both by the creation of new software components for IoT ecosystems, as well as create new Platforms for Connected Smart Objects with minimal investment. Large-scale pilots implemented in smart cities will provide both social, technical and business proofs-of-concept for such IoT ecosystems. This is feasible because the bIoTope consortium combines unique IoT experience, commercial solution providers and end-users, thus ensuring the high quality and efficiency of the results and implementations.

Govorov A.O.,Ohio University | Zhang H.,Ohio University | Demir H.V.,Bilkent University | Demir H.V.,Nanyang Technological University | And 2 more authors.
Nano Today | Year: 2014

The paper reviews physical concepts related to the collective dynamics of plasmon excitations in metal nanocrystals with a focus on the photogeneration of energetic carriers. Using quantum linear response theory, we analyze the wave function of a plasmon in nanostructures of different sizes. Energetic carriers are efficiently generated in small nanocrystals due to the non-conservation of momentum of electrons in a confined nanoscale system. On the other hand, large nanocrystals and nanostructures, when driven by light, produce a relatively small number of carriers with large excitation energies. Another important factor is the polarization of the exciting light. Most efficient generation and injection of high-energy carriers can be realized when the optically induced electric current is along the smallest dimension of a nanostructure and also normal to its walls and, for efficient injection, the current should be normal to the collecting barrier. Other important properties and limitations: (1) intra-band transitions are preferable for generation of energetic electrons and dominate the absorption for relatively long wavelengths (approximately >600 nm), (2) inter-band transitions efficiently generate energetic holes and (3) the carrier-generation and absorption spectra can be significantly different. The described physical properties of metal nanocrystals are essential for a variety of potential applications utilizing hot plasmonic electrons including optoelectronic signal processing, photodetection, photocatalysis and solar-energy harvesting. © 2014 Elsevier Ltd.

Agency: European Commission | Branch: H2020 | Program: RIA | Phase: FETHPC-1-2014 | Award Amount: 4.12M | Year: 2015

Multiscale phenomena are ubiquitous and they are the key to understanding the complexity of our world. Despite the significant progress achieved through computer simulations over the last decades, we are still limited in our capability to accurately and reliably simulate hierarchies of interacting multiscale physical processes that span a wide range of time and length scales, thus quickly reaching the limits of contemporary high performance computing at the tera- and petascale. Exascale supercomputers promise to lift this limitation, and in this project we will develop multiscale computing algorithms capable of producing high-fidelity scientific results and scalable to exascale computing systems. Our main objective is to develop generic and reusable High Performance Multiscale Computing algorithms that will address the exascale challenges posed by heterogeneous architectures and will enable us to run multiscale applications with extreme data requirements while achieving scalability, robustness, resiliency, and energy efficiency. Our approach is based on generic multiscale computing patterns that allow us to implement customized algorithms to optimise load balancing, data handling, fault tolerance and energy consumption under generic exascale application scenarios. We will realise an experimental execution environment on our pan-European facility, which will be used to measure performance characteristics and develop models that can provide reliable performance predictions for emerging and future exascale architectures. The viability of our approach will be demonstrated by implementing nine grand challenge applications which are exascale-ready and pave the road to unprecedented scientific discoveries. Our ambition is to establish new standards for multiscale computing at exascale, and provision a robust and reliable software technology stack that empowers multiscale modellers to transform computer simulations into predictive science.

Brody D.C.,Brunel University | Brody D.C.,Saint Petersburg National Research University of Information Technologies | Meier D.M.,Brunel University
Physical Review Letters | Year: 2015

The solution to the problem of finding a time-optimal control Hamiltonian to generate a given unitary gate, in an environment in which there exists an uncontrollable ambient Hamiltonian (e.g., a background field), is obtained. In the classical context, finding the time-optimal way to steer a ship in the presence of a background wind or current is known as the Zermelo navigation problem, whose solution can be obtained by working out geodesic curves on a space equipped with a Randers metric. The solution to the quantum Zermelo problem, which is shown here to take a remarkably simple form, is likewise obtained by finding explicit solutions to the geodesic equations of motion associated with a Randers metric on the space of unitary operators. The result reveals that the optimal control in a sense "goes along with the wind." © 2015 American Physical Society.

Malashin R.,Saint Petersburg National Research University of Information Technologies
Journal of Physics: Conference Series | Year: 2014

Matching of digital images is very challenging computer vision problem. The aim of investigation was developing of algorithms for matching real aerial and cosmic photographs. In the proposed methods, images are described locally by scale and rotation invariant descriptors. Reliability and high accuracy of the algorithms has been achieved by combining dense keypoint detector and robust descriptor with complex procedure of outlier elimination. The algorithms are capable of making correct decisions when number of local mismatches is more than 99%. © Published under licence by IOP Publishing Ltd.

Buzdalov M.,Saint Petersburg National Research University of Information Technologies
Proceedings - 2012 11th International Conference on Machine Learning and Applications, ICMLA 2012 | Year: 2012

In this paper, an automated method for generation of tests against inefficient solutions for programming challenge tasks on graph theory is proposed. The method is based on the use of (1+1) evolution strategy and is able to defeat several kinds of inefficient solutions. The proposed method was applied to a task from the Internet problem archive, the Timus Online Judge. © 2012 IEEE.

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