bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improvement of electron beam quality in laser wakefield acceleration by a circularly-polarized laser pulse
Authors: Jain A , Gupta D N 
Published: April 2021

Abstract
Electron acceleration driven by laser wakefield using a laser pulse with circular polarization is studied to generate better-quality electron bunches. In order to inject electrons into the accelerating phase of the plasma wave, a density transition shaped bump is employed. Using particle-in-cell simulations, we demonstrate the influence of laser polarization on the quality of electron bunch. The simulation results (using experimentally achievable parameters) show that the electron bunch with higher peak-energy, narrow energy-spread, and low emittance can be obtained by using a laser pulse with circular polarization as compared to the usually employed linear polarization in a mm-scale length plasma. The results show the improved quality of the electron bunch generated from laser wakefield accelerations. The predicted electron bunch quality may be crucial in developing plasma-based electromagnetic radiation sources.
Quantum Langevin approach for superradiant nanolasers
Authors: Protsenko Igor E , Uskov Alexander V , André Emil C , Mørk Jesper , Wubs Martijn 
Published: April 2021

Abstract
A new approach for analytically solving quantum nonlinear Langevin equations is proposed and applied to calculations of spectra of superradiant lasers where collective effects play an important role. We calculate lasing spectra for arbitrary pump rates and recover well-known results such as the pump dependence of the laser linewidth across the threshold region. We predict new sideband peaks in the spectrum of superradiant lasers with large relaxation oscillations as well as new nonlinear structures in the lasing spectra for weak pump rates. Our approach sheds new light on the importance of population fluctuations in the narrowing of the laser linewidth, in the structure of the lasing spectrum, and in the transition to coherent operation.
Free-electron nanolaser based on graphene plasmons
Authors: Avetissian H K , Avchyan B R , Matevosyan H H , Mkrtchian G F 
Published: April 2021

Abstract
In this paper, a possible way to achieve lasing from the THz to the extreme UV domain due to stimulated scattering of graphene plasmons (GPs) on free electrons is considered. The analytical-quantitative description of the proposed free electron laser scheme is based on a self-consistent set of Maxwell–Vlasov equations. We study the downconversion as well as the upconversion. It is shown that the coherent downconversion of infrared radiation to THz can be achieved using a source of very non-relativistic electrons at the resonant coupling with the GPs. Due to the strongly confined GPs, the upconversion of mid-infrared to extreme UV radiation can be achieved with mildly relativistic electron beams. The latter is a promising mechanism for a tabletop short-wavelength free-electron nanolaser.
Study on higher moments of net-charge multiplicity distributions using a multiphase transport model *
Authors: Huang Ling , Ma Guo-Liang 
Published: April 2021

Abstract
The moments and moment products of conserved charges are believed to be sensitive to critical fluctuations, which have been adopted in determining the QCD critical point. Using a dynamical multiphase transport model, we reproduce the centrality and energy dependences of moments and moment products of net-charge multiplicity distributions in Au+Au collisions, measured by the Beam Energy Scan program at the RHIC. No non-monotonic energy dependence is observed. We infer that the moment products develop during the dynamical evolution of heavy-ion collisions. The observed difference based on the expectation of the Poisson baseline indicates a positive two-particle correlation between positively and negatively charged particles, which can arise from different dynamical processes at different stages. Therefore, to adopt moments and moment products of net-charge multiplicity distributions in determining the QCD critical point of relativistic heavy-ion collisions, it is essential to consider the dynamical evolution.
Recent progress in integrated electro-optic frequency comb generation
Authors: Sun Hao , Khalil Mostafa , Wang Zifei , Chen Lawrence R. 
Published: April 2021

Abstract
Optical frequency combs have emerged as an important tool enabling diverse applications from test-and-measurement, including spectroscopy, metrology, precision distance measurement, sensing, as well as optical and microwave waveform synthesis, signal processing, and communications. Several techniques exist to generate optical frequency combs, such as mode-locked lasers, Kerr micro-resonators, and electro-optic modulation. Important characteristics of optical frequency combs include the number of comb lines, their spacing, spectral shape and/or flatness, and intensity noise. While mode-locked lasers and Kerr micro-resonators can be used to obtain a large number of comb lines compared to electro-optic modulation, the latter provides increased flexibility in tuning the comb spacing. For some applications in optical communications and microwave photonics, a high degree of integration may be more desirable over a very large number of comb lines. In this paper, we review recent progress on integrated electro-optic frequency comb generators, including those based on indium phosphide, lithium niobate, and silicon photonics.
Photonic radio frequency channelizers based on Kerr optical micro-combs
Authors: Tan Mengxi , Xu Xingyuan , Wu Jiayang , Nguyen Thach G. , Chu Sai T. , Little Brent E. , Morandotti Roberto , Mitchell Arnan , Moss David J. 
Published: April 2021

Abstract
We review recent work on broadband RF channelizers based on integrated optical frequency Kerr micro-combs combined with passive micro-ring resonator filters, with microcombs having channel spacings of 200 and 49 GHz. This approach to realizing RF channelizers offers reduced complexity, size, and potential cost for a wide range of applications to microwave signal detection.
Hybrid material integration in silicon photonic integrated circuits
Authors: Chakravarty Swapnajit , Teng Min , Safian Reza , Zhuang Leimeng 
Published: April 2021

Abstract
Hybrid integration of III–V and ferroelectric materials is being broadly adopted to enhance functionalities in silicon photonic integrated circuits (PICs). Bonding and transfer printing have been the popular approaches for integration of III–V gain media with silicon PICs. Similar approaches are also being considered for ferroelectrics to enable larger RF modulation bandwidths, higher linearity, lower optical loss integrated optical modulators on chip. In this paper, we review existing integration strategies of III–V materials and present a route towards hybrid integration of both III–V and ferroelectrics on the same chip. We show that adiabatic transformation of the optical mode between hybrid ferroelectric and silicon sections enables efficient transfer of optical modal energies for maximum overlap of the optical mode with the ferroelectric media, similar to approaches adopted to maximize optical overlap with the gain section, thereby reducing lasing thresholds for hybrid III–V integration with silicon PICs. Preliminary designs are presented to enable a foundry compatible hybrid integration route of diverse functionalities on silicon PICs.
Latest advances in high-performance light sources and optical amplifiers on silicon
Authors: Liu Songtao , Khope Akhilesh 
Published: April 2021

Abstract
Efficient light generation and amplification has long been missing on the silicon platform due to its well-known indirect bandgap nature. Driven by the size, weight, power and cost (SWaP-C) requirements, the desire to fully realize integrated silicon electronic and photonic integrated circuits has greatly pushed the effort of realizing high performance on-chip lasers and amplifiers moving forward. Several approaches have been proposed and demonstrated to address this issue. In this paper, a brief overview of recent progress of the high-performance lasers and amplifiers on Si based on different technology is presented. Representative device demonstrations, including ultra-narrow linewidth III–V/Si lasers, fully integrated III–V/Si/Si3N4 lasers, high-channel count mode locked quantum dot (QD) lasers, and high gain QD amplifiers will be covered.
Monolithic DWDM source with precise channel spacing
Authors: Hou Lianping , Tang Song , Marsh John H. 
Published: April 2021

Abstract
We report a low-cost manufacturing approach for fabricating monolithic multi-wavelength sources for dense wavelength division multiplexing (DWDM) systems that offers high yield and eliminates crystal regrowth and selective area epitaxy steps that are essential in traditional fabrication methods. The source integrates an array of distributed feedback (DFB) lasers with a passive coupler and semiconductor optical amplifier (SOA). Ridge waveguide lasers with sampled Bragg side wall gratings have been integrated using quantum well intermixing to achieve a fully functional four-channel DWDM source with 0.8 nm wavelength spacing and residual errors < 0.13 nm. The output power from the SOA is > 10 mW per channel making the source suitable for use in passive optical networks (PONs). We have also investigated using multisection phase-shifted sampled gratings to both increase the effective grating coupling coefficient and precisely control the channel lasing wavelength spacing. An 8-channel DFB laser array with 100 GHz channel spacing was demonstrated using a sampled grating with two π-phase-shifted sections in each sampling period. The entire array was fabricated by only a single step of electron beam lithography.
Four-wave mixing in silicon-nanocrystal embedded high-index doped silica micro-ring resonator
Authors: Li Yuhua , Wang Xiang , Davidson Roy , Little Brent E. , Chu Sai Tak 
Published: April 2021

Abstract
A nonlinear integrated optical platform that allows the fabrication of waveguide circuits with different material composition, and at small dimensions, offers advantages in terms of field enhancement and increased interaction length, thereby facilitating the observation of nonlinear optics effects at a much lower power level. To enhance the nonlinearity of the conventional waveguide structure, in this work, we propose and demonstrate a microstructured waveguide where silicon rich layer is embedded in the core of the conventional waveguide in order to increase its nonlinearity. By embedding a 20 nm thin film of silicon nanocrystal (Si-nc), we achieve a twofold increase of the nonlinear parameter, γ. The linear relationship between the four-wave mixing conversion efficiency and pump power reveals the negligible nonlinear absorption and small dispersion in the micro-ring resonators. This simple approach of embedding an ultra-thin Si-nc layer into conventional high-index doped silica dramatically increases its nonlinear performance, and could potentially find applications in all-optical processing functions.
High heat removal technique for a lithium neutron generation target used for an accelerator-driven BNCT system
Authors: Yoshihashi S. , Tsuneyoshi T. , Tsuchida K. , Furuzawa D. , Honda S. , Watanabe K. , Yamazaki A. , Tsuji Y. , Hamaji Y. , Tokitani M. , Tamura H. , Sagara A. , Kiyanagi Y. , Uritani A. 
Published: April 2021

Abstract
Accelerator-driven neutron sources have been developed worldwide for boron neutron capture therapy (BNCT) instead of nuclear reactors. Nagoya University is currently developing a compact DC accelerator driven BNCT system using a sealed lithium (Li) target. The target receives a high heat load by a proton beam, and the heat then requires efficient removal. This study developed a high-efficiency heat removal technique that uses V-shaped staggered ribs on the heat removal side of the flow channels. We performed experiments using an electron beam to confirm the technique performance. The results showed double the heat removal performance compared to the smooth surface channel. The value expected to sufficiently remove 6.6 MW/m2 of heat load provided by the proton beam at the Nagoya University neutron source for BNCT.
The persistence of flexible coal in a deeply decarbonizing energy system
Authors: Ding Yongbin , Li Mingquan , Abdulla Ahmed , Shan Rui , Gao Shuo , Jia Guozhu 
Published: April 2021

Abstract
Extensive literature has highlighted the difficulty in operating baseload power plants—especially coal-fired units—in a decarbonized electric power system with a high share of variable renewable energy, with some of it recommending immediate coal phaseouts. However, the coal fleet across China is large and young, making its imminent phaseout unrealistic. Moreover, power system operators and policy makers face other constraints in their pursuit of energy system decarbonization—chief among them the need to achieve high levels of reliability—something coal units could provide. We assess the persistence of coal in a decarbonizing power system under various retrofit scenarios that seek to enhance the flexibility of coal units: after all, energy transitions do not occur in a vacuum and owners of coal power plants will likely pursue innovations to extend the lifetimes and profits of their assets, even as the wider energy transition unfolds. We evaluate the economic and environmental impacts of improving coal power unit flexibility in Jiangsu’s power system under four levels of renewable energy penetration and three scopes of coal flexibility retrofits. Our results show that coal units persist even at very high renewable penetrations, and retrofits help them reduce power system costs, enable renewable energy integration, and marginally cut emissions. Smaller coal units become peaker rather than baseload units, providing the power system with flexibility rather than just energy. Our results show how challenging the low-carbon transition is likely to be without outright phaseouts of coal generation.
Trends of the digital economy development in Russia
Authors: Romanyuk Maria , Sukharnikova Maria , Chekmareva Natalia 
Published: April 2021

Abstract
The article describes the objective prerequisites for the development of digitalization of the Russian economy. The characteristic of foreign and domestic approaches to theoretical and methodological generalization of digitalization processes is given. The article substantiates the current position of Russia in international ICT development ratings, the country’s share in the world market of ICT goods and services, and the degree of dependence on their imports. The analysis of the development of the state policy of Russia in the field of ICT was carried out, strategic goals, priorities and targets for the development of the digital society in Russia until 2030 were named. Analysis of the dynamics of ICT development showed that currently there is a positive trend only for one of the three goals of the National Program “Digital economy of the Russian Federation”, aimed at creating an information and telecommunications infrastructure. The strategic analysis of the Russian economy showed that with high rates of digitalization of social infrastructure and public administration, the contribution of ICT industries to the country’s GDP does not increase. So, according to the Strategy of development of the information society in the Russian Federation until 2030, the state directly regulates the direction of development of information infrastructure, while the introduction of digital technologies in the real sector of the economy is a matter of business initiatives.
A survey on data integrity verification schemes using blockchain technology in Cloud Computing Environment
Authors: Gangadevi K , Renuga Devi R 
Published: April 2021

Abstract
Cloud computing is the delivery of different services for business or any organization to store their data and utilize the various resources over the internet. The resources of cloud computing is storage, software, computing hardware and services. Usefulness of the cloud computing infrastructure is to grant services based on demand to the user. The security is a major concern in the cloud computing that are many modes of securities including accessibility, authentication, data integrity, data recovery and confidentiality. The data integrity is major role in the cloud computing security and storage service. Hence, the data integrity scheme provides the proof the truthfulness of the stored data in the cloud. In this paper, we are conducting a brief survey on data integrity verification schemes for cloud computing based on blockchain technology. The aim of this survey is to enhance the understanding the security issues and discuss the importance of data integrity scheme for outsourced data.
Sagnac interferometer and the quantum nature of gravity
Authors: Marletto Chiara , Vedral Vlatko 
Published: April 2021

Abstract
We use a quantum variant of the Sagnac interferometer to argue for the quantum nature of gravity assuming the equivalence principle, which we formulate in its quantum version. We first present an original derivation of the phase acquired in the conventional Sagnac matter-wave interferometer, within the Hamiltonian formalism. Then we modify the interferometer in two crucial respects. The interfering matter wave is interfered along two different distances from the centre and the interferometer is prepared in a superposition of two different angular velocities. We argue that if the radial and angular degrees of freedom of the matter wave become entangled through this experiment, then, via the equivalence principle, the gravitational field must be non-classical.
Edge states and sublattice imbalance of rectangular graphene nanoflakes
Authors: Yorikawa H 
Published: April 2021

Abstract
The energy states of π-electrons in a rectangular graphene flake with a pair of zigzag edges and a pair of armchair edges were studied using a tight-binding method. It is demonstrated that the known exact solution can be interpreted as the results derived from the analytical solutions for graphene nanoribbons on a brick-type lattice by considering the wavefunctions and sublattice imbalance. Edge states in rectangular graphene flakes with a symmetric structure, whose energies are not exactly zero but approach zero as the size increases, are characterized by discrete allowed modes, whereas the zero-energy state appears in rectangular graphene flakes with an asymmetric structure. By applying the edges states of rectangular graphene flakes, zero-energy states were examined in Y-shaped graphene flakes, which involve the same three zigzag edges as in the triangular graphene flakes. Sublattice imbalance in the model was found to force the edge states, including the undamped mode, into zero energy. Configurations of the allowed modes in the zero-energy state are revealed.
The photoacoustoelectric effect of the SAW amplification in the structure of Graphene-Piezocrystal LiNbO3
Authors: Tynyshtykbaev K B , Insepov Z 
Published: April 2021

Abstract
The work presents and analyzes the results of detecting the photoacoustoelectric effect of surface acoustic waves amplification by illumination of a hybrid graphene-LiNbO3 structure. This SAW photoamplification effect is associated with the appearance of an additional photoacoustoelectric current and a decrease of collisional scattering of photoinduced electrons under the action of the SAW electric field. Possible mechanisms of SAW amplification based on the analysis of modern data are discussed. This SAW photoamplification effect can be used to create optoacoustoelectronic devices on a graphene-piezoelectric structures for collecting, amplifying, and detecting superweak sources of THz-radiation photons.
Controlling the structure and photocatalytic properties of three—dimensional aerogels obtained by simultaneous reduction and self-assembly of BiOI/GO aqueous colloidal dispersions
Authors: Puig Julieta , de Castro Alves Lisandra , García Acevedo Pelayo , Arnosa Prieto Angela , Yáñez Vilar Susana , Teijeiro-Valiño Carmen , Piñeiro Yolanda , Hoppe Cristina E , Rivas José 
Published: April 2021

Abstract
Water pollution affects all living habitats, since it is the most basic element that sustains all life forms and, as an exceptional solvent, it readily makes any compound available for living cells, either nutrients or noxious substances. Elimination of molecular contaminants from water quality is one of the most challenging technical problems that conventional treatments like flocculation and filtration fail short to defeat. Particulate photocatalysts, used to degrade contaminants, have the main drawback of their recovery from the water matrices. The inclusion of photocatalytic nanoparticles (NPs) into a large supporting framework, is presented as an innovative approach aiming to ensure a facile separation from water. To this end, three-dimensional (3D) aerogels with photocatalytic properties were prepared by a simple and scalable method based on the reduction—induced self-assembly of graphene oxide (GO) in the presence of BiOI nanoparticles. With the help of ascorbic acid, as a green reducing agent, partial reduction of GO into reduced graphene oxide (RGO) and self-assembly of both kinds of nanostructures into a porous monolith was achieved. BiOI doped RGO aerogels were further stabilized and morphologically controlled using poly (ethylene glycol) as stabilizer. The photocatalytic performance of these aerogels was evaluated by following the discoloration of methylene blue (MB) solution, under visible light irradiation, showing that structure and dispersion degree of NPs to be fundamental variables. Hence, this methodology is proposed to produce hybrid aerogels with controlled morphology and photocatalytic performance that has the potential to be used in water cleaning procedures.
Art Concept Pluralism Undermines the Definitional Project
Authors: Magnus P D , Mag Uidhir Christy 
Published: April 2021

AbstractThis discussion note addresses Caleb Hazelwood’s ‘Practice-Centered Pluralism and a Disjunctive Theory of Art’. Hazelwood advances a disjunctive definition of art on the basis of an analogy with species concept pluralism in the philosophy of biology. We recognize the analogy between species and art, we applaud attention to practice, and we are bullish on pluralism—but it is a mistake to take these as the basis for a disjunctive definition.