7th International School and Conference "Saint-Petersburg OPEN 2020" on Optoelectronics, Photonics, Engineering and Nanostructures was held on April 27 - 30, 2020. The Organizer of the conference is the Alferov Federal State Budgetary Institution of Higher Education and Science Saint Petersburg National Research Academic University of the Russian Academy of Sciences. Initially, the School and Conference was supposed to be held in full-time format at the Alferov Academic University (Saint-Petersburg, Russia), as it happened in the past. However, due to the restrictions imposed by the city authorities on holding mass events due to the threat of the spread of the COVID-19 infection, the conference committees decided to move the conference to the online format. The conference consisted of poster reports presented by the participants and online oral presentations by invited speakers. Posters and video reports of the participants were posted on the conference website. Invited speakers made their presentations online. During their speeches, participants could discuss and ask questions in the chat. The School and Conference included a series of invited talks given by leading professors with the aim to introduce young scientists with actual problems and major advances in physics and technology.

Proceedings of the SPIE PHOTONICS EUROPE Conference on Biophotonics in Point-of-Care, 6-10 April 2020, Online Only, France. Proc. SPIE volume 11361

The goal of this International Roadmap for Devices and Systems (IRDS) chapter is to survey, catalog, and assess the status of technologies in the areas of cryogenic electronics and quantum information processing. Application drivers are identified for sufficiently developed technologies and application needs are mapped as a function of time against projected capabilities to identify challenges requiring research and development effort. Cryogenic electronics (also referred to as low-temperature electronics or cold electronics) is defined by operation at cryogenic temperatures (below −150 °C or 123.15 K) and includes devices and circuits made from a variety of materials including insulators, conductors, semiconductors, superconductors, or topological materials. Existing and emerging applications are driving development of novel cryogenic electronic technologies. Information processing refers to the input, transmission, storage, manipulation or processing, and output of data. Information processing systems to accomplish a specific function, in general, require several different interactive layers of technology. A top-down list of these layers begins with the required application or system function, leading to system architecture, micro- or nano-architecture, circuits, devices, and materials. A fundamental unit of information (e.g., a bit) is represented by a computational state variable, for example, the position of a bead in the ancient abacus calculator or the voltage (or charge) state of a node capacitance in CMOS logic. A binary computational state variable serves as the foundation for von Neumann computational system architectures that dominated conventional computing. Quantum information processing is different in that it uses qubits, two-state quantum-mechanical systems that can be in coherent superpositions of both states at the same time, which can have computational advantages. Measurement of a qubit in a given basis causes it to collapse to one of the basis states. Technology categories covered in this report include: • Superconductor electronics (SCE) • Cryogenic semiconductor electronics (Cryo-Semi) • Quantum information processing (QIP)

Continuing miniaturization of electronic devices, together with the quickly growing number of nanotechnological applications, demands a profound understanding of the underlying physics. Most of the fundamental problems of modern condensed matter physics involve various aspects of quantum transport and fluctuation phenomena at the nanoscale. In nanostructures, electrons are usually confined to a limited volume and interact with each other and lattice ions, simultaneously suffering multiple scattering events on impurities, barriers, surface imperfections, and other defects. Electron interaction with other degrees of freedom generally yields two major consequences, quantum dissipation and quantum decoherence. In other words, electrons can lose their energy and ability for quantum interference even at very low temperatures. These two different, but related, processes are at the heart of all quantum phenomena discussed in this book.This book presents copious details to facilitate the understanding of the basic physics behind a result and the learning to technically reproduce the result without delving into extra literature. The book subtly balances the description of theoretical methods and techniques and the display of the rich landscape of the physical phenomena that can be accessed by these methods. It is useful for a broad readership ranging from master's and PhD students to postdocs and senior researchers.

The materials of The International Scientific – Practical Conference is presented below.

The Conference reflects the modern state of innovation in education, science, industry and social-economic sphere, from the standpoint of introducing new information technologies.

It is interesting for a wide range of researchers, teachers, graduate students and professionals in the field of innovation and information technologies.

Anomalous behavior of spin stiffness is revealed in ZnO-based two-dimensional electron systems (2DESs) with strong Coulomb interaction and Wigner-Seitz parameter r_s > 6. The spin stiffness is extracted directly from the quadratic k-dispersion of spin excitons at ν = 1 probed by inelastic light scattering. The resulting values are found to be dramatically rescaled compared to the case of weakly interacting 2DESs—spin stiffness turned out to be of the order of the cyclotron energy with the effective mass of Fermi-liquid quasiparticles. This result is also confirmed by the exact diagonalization simulations.

Spaser nanoparticles, with ultranarrow spectral line width, small size and good biocompatibility, offer a bright prospect as potential biological probes. Sadly, over 10 years since the first demonstration, how the structure components determine their optical performance has not been clarified. Here the effects of gain layer thickness and dye emitter density on the lasing behavior and photostability of spaser nanoparticles are theoretically and experimentally addressed. Results show that for a 16 nm gold-core cavity, gain layer of 10–15 nm is adequate to maximize the spaser emission. For this type of nanoparticle–spaser system, the minimal number of dye emitters per particle, referred to as “dye threshold”, is also vital to spasing action besides the “pump threshold” of laser power. Moreover, dye emitter distribution within the gain layer could be another approach to further improve spaser performance. These contributions give us an opportunity to profoundly understand the physical essence of spaser nanoparticles and to optimize their performance for further biology application.

The fluorescence-based methods of single-molecule optical detection have opened up unprecedented possibilities for imaging, monitoring, and sensing at a single-molecule level. However, single-molecule detection methods are very slow, making them practically inapplicable. In this paper, we show how to overcome this key limitation using the expanded laser spot, laser excitation in a nonfluorescent spectral window of biomolecules, and more binding fluorescent molecules on a biomolecule that increases the detection volume and the number of collected photons. We demonstrate advantages of the developed approach unreachable by any other technique using detection of single cardiac troponin-T molecules: (i) 1000-fold faster than by known approaches, (ii) real-time imaging of single troponin-T molecules dissolved in human blood serum, (iii) measurement of troponin-T concentration with a clinically important sensitivity of about 1 pg/mL. The developed approach can be used for ultrafast, ultrasensitive detection, monitoring, and real-time imaging of other biomolecules as well as of larger objects including pathogenic viruses and bacteria.

We offer and demonstrate a new type of plasmonic metasurface for sensorics and surface-enhanced Raman spectroscopy (SERS) spectroscopy, characterized by a wide spectral range of sensitivity from 450 nm to 850 nm. The metasurface is formed by Ag nanoparticles of different sizes. The metasurface has clear anisotropy formed by the Ag nanoparticles’ size-dependent plasmonic resonances. The resonant wavelength of the metasurface is linearly changed in one direction on a metasurface realizing a wavelength to space conversion and remains the same in the other direction. The metasurface has advantages for use in different applications of optical microscopy and SERS diagnostics, since it simultaneously provides a strong optical signal amplification of up to 4×107 as well as a wavelength to space conversion with a 10 nm spectral resolution. We show the fabrication of the anisotropic plasmonic metasurface by the use of a robust approach based on Ag nanoparticle self-assembly during a molecular-beam-epitaxy growth process. We demonstrate an application of the metasurface for the fluorescence detection of low concentrations of dye molecules (Cy-7.5) and the surface-enhanced Raman spectroscopy of an organic molecular monolayer (Alq3).

In this paper we present measurements and comparison of SPP propagation length at the practically important telecom wavelength (1560 nm) as well as in the near-infrared and visible spectral ranges. The measurements were carried out for plane SPP waves excited on Ag film surface using optical microscopy of SPP waves in the far field. We also demonstrate the possibility of visualization of a SPP waves propagation using multiphoton induced photoluminescence in silver.  

Tensile strain is a promising tool for the creation and manipulation of magnetic solitonic textures in chiral helimagnets via tunable control of magnetic anisotropy and Dzyaloshinskii-Moriya interaction. Here, by using in situ resonant small-angle x-ray scattering, we demonstrate that skyrmion and chiral soliton lattices can be achieved as metastable states in FeGe lamella as distinct states under tensile strain and magnetic fields in various orientations with respect to the deformation. The small-angle scattering data can be well accounted for in the framework of the analytical model for a soliton lattice. By using the experimental results and analytical theory, the unwinding of metastable skyrmions in a perpendicular magnetic field as shown by a small-angle scattering experiment was analyzed via micromagnetic simulation.

Disorder-induced broadening of optical vibrational eigenmodes in nanoparticles of nonpolar crystals is studied numerically. The methods previously used to treat the phonons in defectless particles are adjusted for numerical evaluation of the disordered problem. Imperfections in the forms of Gaussian and binary disorders as well as surface irregularities are investigated thoroughly in a wide range of impurity concentrations and disorder strengths. For dilute and weak pointlike impurities the regimes of separated and overlapped phonon levels are obtained and the behavior of the linewidth predicted analytically is confirmed; the crossover scale falls into the actual range of several nanometers. These notions survive for strong dilute impurities, as well. Regimes and crossovers predicted by the analytical approach are checked and identified, and the minor discrepancies are discussed. We mention a few of them: slower than in analytics increasing of the linewidth with the phonon quantum number for weak disorder and only a qualitative agreement between analytics and numerics for the resonant broadening in strong dilute disorder. The novel phenomena discovered numerically are the “mesoscopic smearing” of the distribution function in the ensemble of identical disordered particles, an inflection of the linewidth dependence on the impurity concentration for light “dense” binary impurities, and a position-dependent capability of a strong impurity to catch the phonon. It is shown that surface irregularities contribute to the phonon linewidth less than the volume disorder, and their rates reveal faster decay with increasing of the particle size. It is argued that the results of the present research are applicable also for quantum dots and short quantum wires.

Microscopic description of Raman spectra in nanopowders of nonpolar crystals is accomplished by developing the theory of disorder-induced broadening of optical vibrational eigenmodes. Analytical treatment of this problem is performed, and line shape and width are determined as functions of phonon quantum numbers, nanoparticle shape, size, and the strength of disorder. The results are found to be strongly dependent on whether the broadened line is separated from or overlaps other lines of the spectrum. Three models of disorder, i.e., weak pointlike impurities, weak smooth random potential, and strong rare impurities, are investigated in detail. The possibility of forming the phonon-impurity bound state is also studied.

Based on the quantum-mechanical theory of electron transfer (ET), the parameter was proposed to describe the electrochemical activity of doped graphenes. The parameter is calculated using the density of states (DOS), local density of state (LDOS) values, which are in turn obtained from the density functional theory (DFT) calculations and reorganization energies of redox system. DOS describes the contribution of the electronic structure of the electrode to the ET process, while the LDOS describes the electron density contribution of the atoms at some distance from the surface electrode. Reorganization energy corresponds to the restriction of solvation shell and bonds in redox system due to ET process. The overall contribution of these parameters enables a comprehensive assessment of the activity that is acceptable for semi-quantitative analysis. Calculations have shown that the proposed activity parameter correlates well with the calculated ET rate constants. Theoretical study of the oxygen reduction reaction (ORR) on graphene doped with p-elements in the framework of quantum-mechanical theory showed that ET activity decreases in the series P-Gr > S-Gr > N-Gr > B-Gr > O-Gr > Gr. According to our estimates, the mixed or adiabatic regime of ET is probably observed on doped graphenes for all steps of ORR. Using N- and B-graphenes as an example and activity parameter, the influence of the applied potential and the atomic fraction of the doped element on the ET activity are studied.