Day 3 :
Keynote Forum
M A Swillam
The American University in Cairo, Egypt
Keynote: On-chip plasmonic modulator
Time : 09:30-10:00
Biography:
M A Swillam is Received his Ph. D from McMaster University, Hamilton, Canada in 2008. After graduation he worked as post-doctoral fellow in the same group. In October 2009, he joined the photonic group and the institute of optical sciences at the University of Toronto where he works as a research fellow. In September 2011, he joined the Department of Physics, the American university in Cairo (AUC). He authored more than 175 technical papers in highly ranked journals and conferences. He also hold 2 patents, a book, and book chapter in these areas. Dr. Swillam is an editor in few international Journals He is also member of the editorial board of many conferences He is also a senior member of the IEEE Photonic society since 2010. He is the founder and the advisor of the optical society of America and SPIE chapters at the AUC and the vice president of the Egyptian Unit.
Abstract:
Surface plasmon polaritons SPPs are electromagnetic waves generated at the interface between a dielectric and a high electron density material such as metals. The field of manipulating and dealing with such distinguished electromagnetic waves is known as the field of plasmonics. The most significant properties of plasmonics are the ability of confining the electromagnetic energy to beyond the classical diffraction limit, and the enhancement of the electromagnetic fields as for example in the metaldielectric-metal slot. So, plasmonics offer the miniaturization of photonic components to nano-scales that were not possible to achieve using the conventional silicon photonics platform. Since plasmonic components are in the nano-scale, then, plasmonics which enable the integration of the photonic and electronic components on the same chip since they have comparable sizes. Distinct applications based on plasmonics have been successfully produced and studied such as sensors1-3, filters, multiplexers, interferometers, and modulators. The modulator is one of the most significant components in telecommunication devices. Since silicon weak nonlinear electro-optic effects, its modulation ability is very poor. However, plasmonics have shown the ability to integrate high nonlinear electro-optic polymers EOPs with plasmonic components to produce high performance plasmonic modulators4-8. Such modulators have the advantages of high speed operation and minimized device size. In this paper, we introduce an on-chip plasmonic modulator, which is characterized by its high modulation depth, low power consumption, and small footprint. The modulator is based on the ring resonator mechanism the structure is built from a stack of five layers above a SiO2 substrate. The layers are built as Si-EOP-metal-EOP-Si. Upon applying a small voltage across the EOP layers, the EOP changes its refractive index, so the plasmonic mode changes its effective index value, this results in a change of the resonant wavelength/frequency in the ring resonator. Fig.1 shows the shift of the resonant wavelength due to an application of voltage of only 1.3V. This wavelength shift can be understood as a change in level of the transmitted power, thereby can be viewed as optical modulation..
Keynote Forum
P Singha Deo
S N Bose National Centre for Basic Sciences, India
Keynote: Negative partial density of states in mesoscopic systems
Time : 10:00-10:30
Biography:
P Singha Deo did his PhD in 1996 and has remained associated with research and teaching in physics in premier institutions and universities of abroad and in India. He has published more than 50 papers in international journals. He is a Professor at S N Bose Centre, Kolkata since 1999 and successfully guided several PhD theses. He has worked on various issues and problems in mesoscopic physics and correlated systems. Some of his current research topics include quantum devices, quantum capacitance, bosonization in higher dimensions, quantum mechanical scattering phase shift in low dimensions, etc.
Abstract:
Scattering phase shift of an electron in quasi-one-dimensional systems can now be experimentally measured. The experiment has accentuated many theoretical problems. In this study we have addressed these problems using the concept of burgers circuit. In case of scattering in quasi one dimension, the contour PDABQCRS in the first Reimann surface can have subloops like ABQC in fig. Such a sub-loop is very new and novel to quasi one dimension and does not occur in one, two or three dimensions. Observation of such a subloop helps us to prove some results. Whether partial density of states (PDOS) can be negative is still an open problem. On applying the concept of burgers circuit on a closed subloop we can prove its negativity. The proof does not depend on explicit calculations for specific models but uses the topological properties of subloops and is general. Realistic potentials have been shown to generate such subloops and also the fact that such subloops are consistent with the burgers circuit which suggests that such subloops can occur in a large class of mesoscopic systems. It has been also argued that such negative PDOS can have several physical consequences including a mechanism for electron-electron attraction. We can also prove that semiclassical Friedel sum rule can become exact in a purely quantum regime. This can help us to experimentally determine the density of states and hence mesoscopic thermodynamic and transport properties without knowing the exact potential or impurity configuration inside the sample.
- Quantum Physics and High Energy Physics | Superconductivity and Superfluidity | Theoretical and Experimental Study of Soft Matter
Location: Madison
Chair
I Chávez
Instituto de Investigaciones en Materiales, Mexico
Co-Chair
Ranjan Chaudhury
S N Bose National Centre For Basic Sciences, India
Session Introduction
I Chávez
Instituto de Investigaciones en Materiales, Mexico
Title: BCS-Bose crossover extended with hole cooper pairs
Time : 10:50-11:10
Biography:
I Chávez, MS, is a PhD candidate in the Material Sciences and Engineering Research Program at National Autonomous University of Mexico (UNAM). He is assistant professor in the School of Sciences at UNAM. He won 3rd place in the 1st National Journalism Contest 2010, CONACyT, in Mexico with the paper entitled “Noninteger dimensions.”
Abstract:
Applying the generalized Bose-Einstein conden-sation (GBEC)1 theory we extend the BCS-Bose crossover theory by explicitly including hole Cooper pairs (2hCPs). GBEC hinges on three separate new ingredients, it: a) treats CPs as actual bosons which as distinct from BCS pairs which strictly speaking are not bosons; b) includes 2hCPs on an equal footing with two-electron ones (2eCPs); and c) in the resulting ternary ideal boson-fermion (BF) gas natur-ally incorporates BF vertex interactions that drive forma-tion/disintegration processes of CPs. This leads to a phase diagram with two pure phases, one with 2hCPs and the other with 2eCPs, plus a mixed phase with arbitrary proportions of 2eCPs and 2hCPs. The special-case phase when there is perfect symmetry, i.e., with ideal 50-50 proportions between 2eCPs and 2hCPs, gives the usual unextended BCS-Bose crossover. But the extended crossover predicts Tc/TF values (with Tc and TF the critical and the Fermi temperatures) for some well-known conventional superconductors comparing quite well with experiment and, notably, much better than BCS predictions. In turn, these results are compared with theoretical curves associated with the extended crossover for the special case of perfect symmetry holding at n/nf = 1, where n is the total number particle density and nf is the number density of unbound electrons at T = 0. Remarkably, for 50-50 symmetry all extended-crossover results lie below the Bogoliubov et al. upper limit λBCS ≤ ½, where λBCS is the dimensionless BCS coupling constant; this affords corroboration of their limit.
Ranjan Chaudhury
S N Bose National Centre For Basic Sciences, India
Title: Topological excitations in low dimensional magnetic systems
Time : 11:10-11:30
Biography:
Ranjan Chaudhury received his PhD from TIFR (Mumbai, India) in 1988. Thereafter, he held Post-doctoral and Visiting Scientist positions at ICTP (Trieste, Italy), McMaster University (Hamilton, Canada), University of Minnesota (Minneapolis, USA), LEPES-CNRS (Grenoble, France) and BLTP-JINR (Dubna, Russia). He is at present Professor (Associate) at SNBNCBS (Kolkata, India). He has published about 40 papers in several internationally reputed journals and has 20 other scientific publications. He has won several awards and honours including publication of his biography in Marquis Who's Who in the World ( New Jersey, USA 1999 & 2011) , in Marquis Who's Who in Asia (New Jersey, USA 2007) and International Scientist of the Year ( IBC, Cambridge, Great Britain 2007).
Abstract:
The low-dimensional magnetic systems, particularly the quasi-two dimensional ones, are of paramount technological importance in the present times in view of the possible existence of vortices/anti-vortices and merons/anti-merons, characterized as topological excitations. Besides, they provide considerable challenges to condensed matter physicists, both theoreticians and experimentalists for their satisfactory microscopic understanding. In collaboration with other members of my research group, I have investigated the nature of magnetic correlations and spin excitations in layered XY-anisotropic ferromagnetic and anti-ferromagnetic spin ½ systems realized in K2CuF4 and La2CuO4, by a combination of phenomenological and field theoretical techniques. These methodologies include semi-classical Berezinskii-Kosterlitz-Thouless (BKT) phenomenology corresponding to the unbinding of topological excitations and coherent state based effective action approach to identify the topological excitations themselves. Our theoretical works were motivated by the occurrences of prominent “central peak”s in the dynamical structure function in the constant-q scan of the inelastic neutron scattering experiments performed on the above two materials. Our detailed study of the spin dynamics induced by the translational motion of the unbound topological excitations for temperatures above TBKT, supported by the experimental results, brings out the clear possibilities of the emergence of the novel phenomenon of “quantum BKT transition” in the above two systems, with the observed limitations of the conventional semi-classical phenomenology.
Ioan Has
Land Forces Academy, Romania
Title: Initial model of ether describing electromagnetic phenomena, including gravity
Time : 11:30-11:50
Biography:
Ioan Has has completed his license at Technical University of Constructions from Bucharest in 1965, where the Physics course was delivered by prof. Nicolae Barbulescu. He obtained PhD degree in Geotechnical and Foundation field, from TUCB, in 1979. He followed a doctoral Seminar in 1975 at International Mechanics Centre from Udine, Italy. He functioned as Professor at Geotechnical and Foundation Chair from TUCB and at Technical Disciplines Chair from Land Forces Academy, Sibiu. But now works as independent expert in constructions. He published over 110 papers (40 in physics) in reputed journals and participated at about 20 conferences (12 in physics).
Abstract:
This work is based on results obtained in our two previous series of articles. In first series, an error was found in Michelson’s analysis of interferometer experiment. But Einstein relied on it, while developing the SRT, eliminating ether from physics. Our results imply that ether can exist. In second series, we proposed and validated the hypothesis that Coulomb’s law would better describe the reality including ether, by adding other terms to the left/right of actual term in r-2 including a term in –lnr. So, the force existing between two distant dipoles, when computed with completed Coulomb’s law, depends on r-2, as in Newton’s law. Numerically, the two forces were practically equal, resulting that the gravitation consists of dipoles interactions. For ether’s structure, we proposed the HM16 model, in which the constituent etherons are placed in the nodes of a microcrystalline network, and manifesting forces of mutual attraction/rejection. The microparticles (MPs) consist of local zones of ether, where an energy intake induced a state of vibrations/vortexes. The vibrant MPs will transmit fundamental vibrations (FVs) in ether, which have a velocity cF. Stationary FVs do not transmit energy in the infinite ether, but FVs create interaction forces between MPs having electric/magnetic nature, giving gravitation. MP can expel/absorb an elementary special particle, the photon (F), which moves through ether with light speed (c). The Fs constitute electromagnetic waves, which transmit energy in ether. The F photon creates its FVs in ether (dual aspect). Admitting cF>c, cF corresponds to gravitational waves, resulting from dipole interaction between the MPs, given by completed Coulomb’s law. HM16 explains the nature of the electric field as volumetric ε strains and of the magnetic field as distortional γ strains of ether. HM16 also explains the various interactions between EM waves and MPs or collisions between MPs.
Anant Raj
North Carolina State University, USA
Title: Fast zero-point family of methods for computing phonon dispersion
Time : 11:50-12:10
Biography:
Anant Raj received his Undergraduate Degree in Mechanical Engineering from the Indian Institute of Technology, Kanpur in 2010. He received a Master’s degree in Nuclear Engineering from the North Carolina State University, Raleigh in 2013 and continued to pursue a PhD degree under the guidance of Prof Jacob Eapen. During his graduate studies, he was introduced to the fascinating field of materials science and the intricacies of probing materials behavior using statistical mechanics and atomistic simulations. He received his PhD on phonon dynamics and beyond-phonon descriptors for energy transport in materials. He is currently working as a Post-doctoral Research Scholar at the North Carolina State University.
Abstract:
Phonon dispersion curves are important to the analysis of energy transport in semiconductor and insulator materials. Experimentally, they can be determined using neutron/x-ray scattering or Raman spectroscopy techniques that involve the interaction of phonons with different forms of radiation. Theoretically, under harmonic approximation, they can be computed from the dynamical matrix extracted from force constants. Time correlations of dynamic variables in the reciprocal space offer a rich theoretical setting for computing the phonon dispersion curves, particularly for systems with marked anharmonic interactions. Currently, there are two general methods using the time correlation approach. In the first, the phonon dispersion is calculated using the frequencies extracted from the zero time expectation value of the correlation of displacements in the reciprocal space; equipartition of energy between the phonon modes is implicitly assumed. In the second method, the frequencies obtained from the Fourier transform of the time correlation of velocities are used to compute the dispersion of phonon modes. While the equipartition approach is computationally fast, since it requires only the zero time correlations, the assumption of equipartition of energy between the modes can result in tangible errors, especially at lower temperatures. In contrast, the Fourier method is more accurate but requires long correlation times for resolving the frequencies, making this approach computationally expensive. In this work, we present a family of methods to compute the normal mode frequencies from the ratio of the expectation value of the correlation of conjugate variables at zero time. This approach is computationally as fast as the equipartition methods, but is also robust and works even in the absence of equipartition. We present two variants of this approach that are appropriate for use in atomistic simulations. In the first, the phonon dispersion curves are calculated using the ratio of the normal mode amplitudes for velocity and displacement while in the second they are computed analogously from velocity and acceleration. We further elucidate the attractiveness of the second approach entailing velocity and acceleration for systems exhibiting anisotropic and highly anharmonic vibrations. Although the approach involving velocity and displacement is known before, we derive a family of zero-point methods from statistical-mechanical first principles. Finally, we demonstrate the accuracy, efficiency, and robustness of the zero-point methods on model linear chains and graphene using atomistic simulations.
D Schmeltzer
The City University of New York, USA
Title: Weyl semimetals A S -matrix study
Time : 13:00-13:20
Biography:
D Schmeltzer has completed his PhD from TECNION ISRAEL INSTITUTE of TECHNOLOGY HAIFA, IRAEL. He has published more than 120 papers in reputed journals and has been serving as an editorial board member. Hi is completed his B.Sc., in Hebrew University and M.Sc. in Technion, D.Sc. Now he is working a Professor of Theoretical Condensed Matter Physics in the City University of New York, New York, USA.
Abstract:
We study a model for Weyl semimetals using the scattering matrix formalism. We take in account boundary condition. Due to the boundary, the self adjoint condition needs to be checked in order to insure physical solutions. Using the principle of minimal coupling, we identify the electron-photon Hamiltonian. The photoemission intensity is computed using the $S$-matrix formalism. The $S$-matrix is derived using an incoming photon state, and outgoing state of a photoelectron and a hole in the valence band. The photoemission reveals the valence band dispersion $epsilon=pm v k_{y}$ and $^{''}$Fermi arcs $^{''}$. We construct the scattering matrix due to the chiral anomaly and obtain the crossed section for the photon intensity. In the presence of phonon we obtain the scattering matrix for chiral phonons allowing to investigate the Raman scattering.
Taro Toyoda
The University of Electro-Communications, Japan
Title: Photoinduced interfacial electron transfer dynamics of CdSe quantum dots on single crystal rutile TiO2 (001), (110), and (111) surfaces
Time : 13:20-13:40
Biography:
Taro Toyoda has completed his D.Sc. from Tokyo Metroplitan University and Research Associate at National Research Council of Canada. He is a Project Professor of University of Electro-Communications. His research focuses on basic studies of optical properties in semiconductor quantum dots including photoexcited carrier dynamics and their applications to photovoltaic solar cells. He has published more than 200 papers in reputed journals.
Abstract:
Semiconductor quantum dots (QDs) have been studied for their light harvesting capability. Although, a major breakthrough in conversion efficiency of QD-solar cells has yet to be reported. The reason is lack of fundamental understanding of the surface chemistry of QD. For QDs on TiO2, the heterogeneity can be caused by distributions of a number of properties of TiO2 and QDs. Their complecities hinder the understanding of important factors that control the photoinduced interfacial electron transfer (PIET). Herein, we report a stydy of PIET dynamics of CdSe QDs on well characterized single crystal rutile-TiO2 . To characterize the adsorption of CdSe QDs on single crystal rutile-TiO2, we used photoacoustic (PA) spectroscopy. Photoelectron yield (PY) spectroscopy was applied to characterize the valence band maximum of the TiO2 single crystals. The position of VBM for (111) surface is higher than those for the (110) and (001) surfaces. Transient grating (TG) method was applied to study the PIET dynamics. Basically, TG method depends on the refractive index changes due to photoexcited carriers. Pump beam was set at a wavelenght of 500 nm with a pulse width of 150 fs and probe pulse (775 nm) was delayed by an optical delay line (0 - 400 ps). The PIET rate constant of CdSe QDs increases with the increase of free-energy change. The change of the PIET rate constant on the (111) surface is higher than those on the other surfaces, indicating the difference in crystal binding and the overlap of wave fundtions at the QDs/TiO2 interface.
Ke Xia
Beijing Normal University, China
Title: Surface and disorder novel effects on interlayer exchange coupling through magnetic tunnel junctions: Ab initio study
Time : 13:40-14:00
Biography:
Ke Xia has completed his PhD from Nanjing University and Postdoctoral studies from TU Delft and Twente University, Applied Physics department. He is the Head of Department of Physics, BNU China since 2011. He has published more than 80 papers in reputed journals.
Abstract:
Based on first principle study, we present the interlayer exchange coupling (IEC) affected by disorders in two types magnetic tunnel junctions (MTJ) structures: Fe/(MgO, Vacuum)/Fe (001) and Vacuum/Fe/(MgO, Vacuum)/Fe (001). Ferromagnetic coupling amplitude exponentially decrease with the barrier thickness, (surface case, disorder etc.)... We also study the interfacial disorder effects on the IEC through Fe/MgO/Fe(001) and Co0.5Fe0.5/MgO/Co0.5Fe0.5 (001) magnetic tunnel junctions (MTJ). As the sign and IEC amplitude across MgO-based MTJ were not consistent in the literatures, which was attributed to the presence of disorder hinted by local impurities model and supercell total energy analysis. Here, we employ the surface Green’s methods based on TBLMTO to obtain IEC strength, the coherent potential approximation (CPA) method is used to clarify IEC affected by several common types of disorder in MgO based MTJ, such as oxygen vacancy, Boron and Carbon impurities. We found that the character of IEC has strong dependence on the concentration, type and distribution of disorder.
Kevin Storr
Prairie View A&M University, USA
Title: Condensed matter physics at the threshold of the extreme environments of temperature and magnetic fields
Time : 14:00-14:20
Biography:
Kevin Storr earned a Ph.D. in Low Temperature Condensed Matter Physics from the Florida State University at the National High Magnetic Field Laboratory in Tallahassee Florida. He is currently an Associate Professor of Physics at Prairie View A&M University where he mentors undergraduate students in Physics research along with directing the thesis of graduate students. Professor Storr is a member of the Texas Physics Consortium and former faculty senator. Known as the Professor of Value, Dr. Storr conducts colloquia in areas of Value, Leadership, Science and Education and is the director of the newly formed, “Global Value Initiative.” He is a recipient of the International Golden Rule Award The Girma Wolde-Giorgis, Human Conservation Solutionist Award and serves as Special Advisor to the Office of the Ambassador at Large for the Republic of Burundi.
Abstract:
In the area of Condensed Matter, we use extreme environmental conditions of temperature (down to 20 millikelvin) and magnetic field (≤ 45 Tesla) to elucidate and tune the electronic, magnetic and thermal properties of candidate materials using several techniques. Three of our most commonly employed techniques are: electrical transport, magnetic torque cantilever and specific heat. Here we present results from three classes of materials, each studied using similar methods: organic conductors, heavy fermion systems and hybridized graphene. λ-(BETS)2FeCl4 is a quasi, two dimensional, layered, anisotropic organic conductor which has shown three states below liquid helium temperature: an antiferromagnetic-insulator state, metallic state, and a field induced superconducting (FISC) ground states with observed re-entrance. Nd1−xCexCoIn5 is 115 heavy fermion single crystal which exhibits unconventional superconductivity due to being an intermetallic compounds with large electron effective masses. This material can progress from having local moment magnetism to a heavy fermion with the gradual substitution of Nd with Ce. This leads to an adjustment of the availability of 4f electron coupling. Hybridized graphene and hexagonal boron nitride (h-BNC) domains as a disordered 2D electronic system was studied using magnetoelectric transport measurements. It clearly showed show an insulating to a metallic anomalous transition during the cooling process which we modulated with electron and hole-doping. It was concluded that in comparison to other 2D systems, that in h-BNC the transition came about from percolation associated with the metallic graphene and hopping conduction along edge states.
- Poster Presentations
Location: Madison
Session Introduction
Eugene Stephane Mananga
The City University of New York, USA
Title: Equivalence between floquet-magnus and Fer expansions to investigate the dynamics of a spin system in the three-level system
Biography:
Eugene Stephane Mananga is a Faculty Member in the Physics and Chemistry Doctorate Program at the Graduate Center of the City University of New York. He is an Assistant Professor of Physics and Nuclear Medicine at BCC of CUNY, and an Adjunct Professor of Applied Physics at New York University. Eugene completed his PhD in Physics from the Graduate Center of the University of New York, and holds 6 additional graduate degrees and training from various institutions including Harvard University, Massachusetts General Hospital (MGH), and City College of New York. Eugene did his postdoctoral studies in the National High Magnetic Field Laboratory of USA, Harvard Medical School, and Massachusetts General Hospital. Prior to joining Harvard - MGH, Eugene Mananga was an “Ingenieur de Recherche” in the French Atomic Energy Commission and Alternative Energies (CEA-SACLAY).
Abstract:
In this poster, we present the orders to which the Floquet-Magnus expansion (FME) and Fer expansion (FE) are equivalent or different for the three-level system. The third-order calculation is performed of both approaches based on elegant integrations formalism. As the propagator from the FME takes the form of the evolution operator, which removes the constraint of a stroboscopic observation, we appreciated the effects of time-evolution under Hamiltonians with different orders separately. Our work unifies and generalizes existing results of Floquet-Magnus and Fer approaches and delivers illustrations of novel springs that boost previous applications that is based on the classical information. Due to the lack of an unequivocal relationship between the FME and FE, some disagreements between the results produced by these theories will be found, especially in NMR experiments. Our results can find applications in the optimization of NMR spectroscopy, quantum computation, quantum optical control, coherence in optics, and might bear new awareness in fundamental perusals of quantum spin dynamics.
Alexander Shimkevich
NRC Kurchatov Institute, Russia
Title: Introduction in the band theory of liquid dielectrics
Biography:
Alexander Shimkevich has completed his PhD in 1982 from Institute for Physics and Power Engineering (IPPE), DS degree in 1998 from Institute for High Temperature of RAS, and full Professor in 2005. He has been employed by IPPE from 1971 to 2002 and by NRC Kurchatov Institute at present time. Prof. Shimkevich had over forty years of R&D experience in condensed matter physics for application to liquid metal technology and water chemistry of fast and thermal nuclear reactors. He has published more than 200 papers in reviewed journals and is serving as an editorial board member of "Atomic Eneger".
Abstract:
Though the band theory describes an electron population of energy bands on ideal crystal lattices, liquid dielectrics (pure water and molten salts) have the band structure too. It differs from bands in crystals by localization of electrons in "tails" of the allowed bands divided by a band gap. Just the band gap defines physical properties of dielectrics inasmuch as the allowed electronic levels near the bottom of conduction band (donors) and at the top of valence band (acceptors) change these properties. A position of such the impurity level in the band gap of liquid dielectric depends on its atomic concentration but its electron population depends on an electrochemical potential (Fermi level) in the band gap. This potential (as a p-n boundary between the vacant impurity levels and the ones occupied by electrons) becomes the management tool for physical and chemical properties of liquid dielectrics that is carried out by a "thin" shift of Fermi level in the band gap at the expense of an insignificant (<10-5) deviation of the chemical compound composition from the stoichiometric one. This deviation is homogenized in any liquid medium. Controllable shifts of Fermi level in the band gap of ionic and molecular melts as variations of their oxidation-reduction potential (ОRP) are theoretically studied including possibilities for managing their structural, physical and chemical, kinetic and corrosion properties. Correction of these properties by additives and selective extraction of fission products from the aqueous coolant and molten salts by shifting Fermi level are studied too.
M A Swillam
The American University in Cairo, Egypt
Title: Hybrid plasmonic electro-optical ring resonator based modulator based on electrically tuning the ITO’s properties
Biography:
M A Swillam is Received his Ph. D from McMaster University, Hamilton, Canada in 2008. After graduation he worked as post-doctoral fellow in the same group. In October 2009, he joined the photonic group and the institute of optical sciences at the University of Toronto where he works as a research fellow. In September 2011, he was appointed as an assistant professor at the Department of Physics, the American university in Cairo (AUC). He is now an associate professor at the Department of physics at AUC, His research interests include design optimization and fabrication of active and passive nanophotonic and plasmonic devices and systems, silicon photonics, optical interconnects, integrated on- chip optical systems, lab on chip, nano-antenna, metamaterials, and solar cells. The main applications include biomedical systems, energy harvesting, and telecommunications. He authored more than 200 technical papers in highly ranked journals and conferences. He also hold 2 patents, a book, and book chapter in these areas.
Abstract:
This work presents the study and the design of optical ring modulator based on silicon-on-insulator ring resonator topped with silicon dioxide. The input and the output waveguides are separated from the ring resonator by a hybrid plasmonic waveguides in the coupling regions. The power-splitting mechanism is applying the external electric field to the hybrid plasmonic waveguides. The tuning mechanism takes the advantage of changing the refractive index of the modes and attenuating the power. The proposed ring modulator designed to operate under the telecommunication wavelength (1550 nm). A finite difference time domain method with perfect matching layer (PML) absorbing boundary condition is taken up to simulate and analyze the ring modulator. The main operations in digital signal processing are modulation and switching. The growing demand for high capacity signal processing systems made the assimilation of photonic circuitries into electronic circuitries. Optical signal processing systems and components concerned a lot of research. Optical ring resonators are among the fundamental components in optical systems since they can be used as modulators, filters, and sensors. Integrating indium-tin-oxide (ITO) with silicon electro-optic modulator has received enormous attention in the past few years because it’s electrically-induced epsilon-near-zero (ENZ) characteristics. The proposed modulator is based on silicon-on-insulator ring resonator topped with silicon dioxide. The input waveguide and the ring resonator are separated by a hybrid plasmonic waveguide in the coupling region, the same with the ring resonator and the output waveguide. The operation principle of this device is based on coupling the power from input waveguide to the ring resonator to the output waveguide. Tuning the optical power at the output waveguide is through applying electric field to the hybrid plasmonic waveguides, the generated carrier at the ITO layer results in changing the refractive indices of the even and odd modes of the input waveguide and the ring resonator. Moreover, it attenuates the coupling power to the ring resonator.
Daniel Andres Triana Camacho
Industrial University of Santander, Colombia
Title: Python Script in the processing of electrochemical impedance spectroscopy and current transient measurements for the determination of the chemical capacitance
Biography:
Daniel Andres Triana Camacho received the B.S degree in Electronic Engineering from the Technological Units of Santander in 2014, Bucaramanga, Colombia. He is currently Msc. Physics student and researcher at the Science of Biology Materials and Semiconductors CIMBIOS group. His research interests include a design of biomedical devices, condensed matter, data processing, electrochemistry methods, pedagogy models and neural networks.
Abstract:
Big Data is defined in a variety of ways, including a) the search and retrieval of information to make decisions, and b) the science behind the data when these are used to respond any question. On other hand, chemical capacitance (a fundamental thermodynamic quantity related to charge accumulation at an electronic conductor/ionic conductor interface), is conventionally obtained by electrochemical impedance spectroscopy (EIS). Herein, current transients (CT) are proposed as an alternative measurement to determine the chemical capacitance. Thus, we describe a Python script to evaluate whether chemical capacitance can be obtained by CT collected at multiple potentials. The experimental procedure was performed with the redox pair Fe(CN)6 3-/Fe(CN)64-, a model one electron outer sphere process, and applied to the derivation of the chemical capacitance of the redox-activespecies on a Pt electrode. To validate the methodology here proposed is necessary to organize, process, and matching between these two different types of measurements, like so display information in the form of mathematical models, plots and files. Hence, we develop a protocol to analyze and compare a large amount of data irrespective of time scale. Usually, the experimental data for CT and EIS are analyzed independently and in differents ways by computational programs, for instance, repeating the sampling process for different times yields a family of curves named “sampled current-voltammograms”, one for each time scale. In addition, EIS data may be presented in several types of plots (e.g., Bode or Nyquist), which increase the volume of information obtainable from these measurements. Therefore, a getData class was created to get and process the experimental data from CT and EIS measurements. To process the experimental data a Python script was used to instantiate two objects: input and data objects. An input object is a JSON-like object where the file name and the potential for experiment data are defined, thereby JSON object was implemented as a Python dictionary. A data object is the instantiated getData object with the information contained in the data files referenced in the input object. A Python script containing the input and data objects was created to process experimental data of FeIII/FeII redox pair in solution. A total of 64 data files were obtained with NOVA 2.0 software for electrochemistry. Each CT data file contains approximately 15000 experiment numbers, and EIS, 305. With instantiate getData object the capacitance curves against potential from EIS and CT was constructed and compared in an easier way than process data with traditional tools used in electrochemistry. It is concluded that at a specific condition of time scale, the integral of CT and EIS measurements give similar results of capacitance.
- Video Presentations
Location: Madison
Session Introduction
V S Filinov
Joint Institute for High Temperatures of the Russian Academy of Sciences, Russia
Title: Treatment of the ̒ sing problem’ by pair phase space pseudopotential
Biography:
V S Filinov is Doctor Phys&Math. Sc., Prof.. Education: Moscow Power Engineering Institute, M. Sc.degree in Physical Optics, Moscow State University, M. Sc.degree in Mathematics. He is a principal researcher in Joint Institute for High Temperatures Russian Academy of Sciences. He has published more than 200 papers in reputed journals and has been serving as Organizing Committee Member of several International conferences.
Abstract:
The main difficulty for path integral Monte Carlo studies of Fermi systems results from the requirement of antisymmetrization of the density matrix and is known in literature as the ’sign problem’. To overcome this issue the new numerical version of the Wigner approach to quantum mechanics for treatment thermodynamic properties of degenerate systems of fermions has been developed. The new path integral representation of quantum Wigner function in the phase space has been obtained for canonical ensemble. Explicit analytical expression of the Wigner function accounting for Fermi statistical effects by effective pair pseudopotential has been presented. Derived pseudopotential depends on coordinates, momenta and degeneracy parameter of fermions and takes into account coordinate – momentum principle uncertainly. The new quantum Monte-Carlo method for calculations of average values of arbitrary quantum operators has been proposed. To test the developed approach calculations of the momentum distribution function of the degenerate ideal system of Fermi particles has been carried out in a good agreement with analytical Fermi distributions. On other hand the first results on influence of interparticle interaction on momentum distribution functions show appearance of quantum ”tails” in the Fermi distributions.
Peng-Sheng Wei
National Sun Yat-Sen University, Taiwan
Title: Scaling of thermocapillary molten pool shape during laser melting
Biography:
Peng-Sheng Wei received Ph.D. in Mechanical Engineering Department at University of California, Davis, in 1984. He has been a professor in the Department of Mechanical and Electro-Mechanical Engineering of National Sun Yat-Sen University, Kaohsiung, Taiwan, since 1989. Dr. Wei has contributed to advancing the understanding of and to the applications of electron and laser beam, plasma, and resistance welding through theoretical analyses coupled with verification experiments. Investigations also include studies of their thermal and fluid flow processes, and formations of the defects such as humping, rippling, spiking and porosity. Dr. Wei has published more than 80 SCI journal papers, given keynote or invited speeches in international conferences more than 120 times. He is a Fellow of AWS (2007), and a Fellow of ASME (2000). He also received the Outstanding Research Achievement Awards from both the National Science Council (2004), and NSYSU (1991, 2001, 2004), the Outstanding Scholar Research Project Winner Award from National Science Council (2008), the Adams Memorial Membership Award from AWS (2008), the Warren F. Savage Memorial Award from AWS (2012), and the William Irrgang Memorial Award from AWS (2014). He has been the Xi-Wan Chair Professor of NSYSU since 2009, and Invited Distinguished Professor in the Beijing University of Technology, China, during 2015-2017.
Abstract:
The molten pool or fusion zone shape and transport variables affected by thermocapillary force during melting or welding with a distributed energy beam can be scaled as functions of specified working variables. pool. The scaling analysis considers different thicknesses of thermal and momentum boundary layers in different regions in the molten pool. Incident flux is irradiated in the central region of the free surface. The driving force is thermocapillary force balanced by shear stresses in the shear layer below the free surface. The scaling results are found to agree well with experimental data and numerical computations for different Prandtl numbers, as shown in Figure 1. Figures 2 and 3 show that scale analysis of the fusion zone depth and width agree well with numerical computations.
Alex Guskov
Institute of Solid State Physics of RAS, Russia
Title: The decomposition of the solution during phase transition
Biography:
Alex Guskov received a Ph.D. degree in 1982 in Physical Institute of the Russian Academy of Sciences. Then A.Guskov went to work in Institute of Solid State Physycs the Russian Academy of Sciences, investigated the influence of interaction of laser radiation and a solid. Simultaneously he was engaged in application of technological processes in manufacture of electronic devices. Now his research interest focuses on heat mass transfer during the phase transition.
Abstract:
The modern theory of phase transitions cannot explain the results of many experiments of interphase mass transfer. One reason for this is the assumption that during crystallization the solution is in the metastable state. The purpose of this study to show that in many cases the solution during crystallization can be an unstable state. The unstable condition leads to decomposition the solution by spinodal scenario. The unstable solution decomposes continuously in the whole volume in this case. Experimental demonstration of spinodal decomposition of the solution is conducted video shooting process of decomposition of an aqueous solution of bromthymol blue while its crystallization. Locally - configuration thermodynamic model is used to explain the state changes of the solution during the phase transition. Spinodal decomposition of the solution explains the process of formation of a periodic distribution of the eutectic composites. The layer of the unstable solution is localized in front of the unstable interface. The unstable solution decomposes into phases, which have a composition close to the eutectic composition of the solid phases. The period of alternation of these phases is set by the period of instability of the interface. Experiments show that the formation of dendrites in the mushy zone and extremum of the component concentration during steady-state regime of crystallization close to interface also occurs in the spinodal decomposition scenario. Spinodal decay during crystallization solutions can be used for their separation into the eutectic phase.
Peter P Pershukevich
The Institute of Physics of NAS Belarus, Belarus
Title: New light-emitting materials for optical technologies based on complexes with europium
Biography:
Peter P Pershukevich, Victoria A Lapina and Tatiana A Pavich – scientific employees of the Institute of Physics of National Academy of Science of Belarus. Dr.V. Lapina has PhD in chemistry, leading scientific researcher. The main direction of her work is biomedical optics and nanotechnologies. She is authors more than 200 scientific papers, 20 patents. Dr. T. Pavich has PhD in chemistry, senior research scientist, specialist in the synthesis of complex compounds of lanthanides. She is authors more than 100 scientific papers, 3 patents. Dr. P. Pershukevich has PhD in physical and mathematical sciences, deputy head of the scientific center, specialist in spectroscopic research, especially luminescence methods, various radiating materials: porous silicon and porous aluminum, inorganic and organic luminophores activated with lanthanides, and others. He is the author of more than 150 scientific papers, 8 patents.
Abstract:
Complex compounds of lanthanides have been extensively studied for many years and interest in them is increasing due to their unique optical properties and a wide range of applications. With the development of nanotechnology, new opportunities appeared in the development of complex compounds of lanthanides with new properties. Particularly important among them are thermal and radiation stability, volatility in vacuum, photostability, durability, homogeneity, etc. Many methods for modifying lanthanide complex compounds, in particular europium (III), have been described in the literature. In the present work, an attempt has been made for the first time to modify coordination compounds by synthesis of nanostructured supramolecular complexes of europium (III), in which nanodiamonds were used as templates. As the initial coordination compounds, two well-tested multiligand complexes of europium were used: the first with tris(tenoyltrifluoroacetonate) and 1,10-phenanthroline (Eu (TTA)3Phen) (also EuT); the second with bathophenanthroline and NO3 groups (Eu (BPhen)2(NO3)3) (also EuB). The totality of the data obtained by us on electron scanning microscopy, spectral-luminescent characteristics, IR and EPR spectra clearly indicates the formation of new complexes with ND as a result of targeted synthesis. Its physicochemical properties differ significantly from those of the initial coordination compounds. It has been revealed that the advantages of complexes with nanodiamonds are: higher photostability (2-3 times), a spectrum with predominant emission in one narrow band 5D0-7F2 (~ 615 nm), a higher luminescence brightness when excited in the far UV region of the spectrum. New luminescent complexes of lanthanides with ND in the composition of polymer matrices can be used: as luminescent substances in OLED; as active materials for detectors and dosimeters of ionizing radiation; as active laser media.