Dynamic Terahertz Beamforming Based on Magnetically Switchable Hyperbolic Materials

In this work, we introduce a concept to enable dynamic beamforming of terahertz (THz) wavefronts using applied magnetic fields (B). The proposed system exploits the magnetically switchable hyperbolic dispersion of the InSb semiconductor. This phenomenology, combined with diffractive surfaces and magnetic tilting of scattered fields, allows the design of a metasurface that works with either circularly or linearly polarized wavefronts. In particular, we demonstrate numerically that the transmitted beam tilting can be manipulated with the direction and magnitude of B. Numerical results, obtained through the finite element method (FEM), are qualitatively supported by semi-analytical results from the generalized dipole theory. Motivated by potential applications in future Tera-WiFi active links, a proof of concept is conducted for the working frequency f = 300 GHz. The results indicate that the transmitted field can be actively tuned to point in five different directions with beamforming of 45{\deg}, depending on the magnitude and direction of B. In addition to magnetic beamforming, we also demonstrate that our proposal exhibits magnetic circular dichroism (MCD), which can also find applications in magnetically tunable THz isolators for one-way transmission/reflection.Comment: 9 pages, 7 figure

Plasmon polaritons in 1D Cantor-like fractal photonic superlattices containing a left-handed material

ABSTRACT: The propagation of light incident upon a 1D photonic superlattice consisting of successive stacking of alternate layers of a right-handed nondispersive material and a metamaterial, arranged to form a Cantor-like fractal, is considered. Plasmon-polariton excitations are thoroughly investigated within the transfer-matrix approach and shown to strongly depend on the Cantor step number N. More specifically, the number of plasmon-polariton bands corresponds to the number 2N −1 of metamaterial layers within the unit cell

New horizons in near-zero refractive index photonics and hyperbolic metamaterials

The engineering of the spatial and temporal properties of both the electric permittivity and the refractive index of materials is at the core of photonics. When vanishing to zero, those two variables provide new knobs to control light-matter interactions. This perspective aims at providing an overview of the state of the art and the challenges in emerging research areas where the use of near-zero refractive index and hyperbolic metamaterials is pivotal, in particular light and thermal emission, nonlinear optics, sensing applications and time-varying photonics

5to. Congreso Internacional de Ciencia, Tecnología e Innovación para la Sociedad. Memoria académica

El V Congreso Internacional de Ciencia, Tecnología e Innovación para la Sociedad, CITIS 2019, realizado del 6 al 8 de febrero de 2019 y organizado por la Universidad Politécnica Salesiana, ofreció a la comunidad académica nacional e internacional una plataforma de comunicación unificada, dirigida a cubrir los problemas teóricos y prácticos de mayor impacto en la sociedad moderna desde la ingeniería. En esta edición, dedicada a los 25 años de vida de la UPS, los ejes temáticos estuvieron relacionados con la aplicación de la ciencia, el desarrollo tecnológico y la innovación en cinco pilares fundamentales de nuestra sociedad: la industria, la movilidad, la sostenibilidad ambiental, la información y las telecomunicaciones. El comité científico estuvo conformado formado por 48 investigadores procedentes de diez países: España, Reino Unido, Italia, Bélgica, México, Venezuela, Colombia, Brasil, Estados Unidos y Ecuador. Fueron recibidas un centenar de contribuciones, de las cuales 39 fueron aprobadas en forma de ponencias y 15 en formato poster. Estas contribuciones fueron presentadas de forma oral ante toda la comunidad académica que se dio cita en el Congreso, quienes desde el aula magna, el auditorio y la sala de usos múltiples de la Universidad Politécnica Salesiana, cumplieron respetuosamente la responsabilidad de representar a toda la sociedad en la revisión, aceptación y validación del conocimiento nuevo que fue presentado en cada exposición por los investigadores. Paralelo a las sesiones técnicas, el Congreso contó con espacios de presentación de posters científicos y cinco workshops en temáticas de vanguardia que cautivaron la atención de nuestros docentes y estudiantes. También en el marco del evento se impartieron un total de ocho conferencias magistrales en temas tan actuales como la gestión del conocimiento en la universidad-ecosistema, los retos y oportunidades de la industria 4.0, los avances de la investigación básica y aplicada en mecatrónica para el estudio de robots de nueva generación, la optimización en ingeniería con técnicas multi-objetivo, el desarrollo de las redes avanzadas en Latinoamérica y los mundos, la contaminación del aire debido al tránsito vehicular, el radón y los riesgos que representa este gas radiactivo para la salud humana, entre otros

Landé g factor factor in GaAs-Ga1−xAlxAs low-dimensional systems

We have performed a theoretical study of the electron effective Land ¿e g factor in GaAs-(Ga,Al)As cylindrical low-dimensional heterostructures under and axis-parallel ap- plied magnetic field. Numerical calculations of the g factor are performed by using the Ogg-McCombe effective Hamiltonian, which includes non-parabolicity and anisotropy ef- fects for the conduction-band electrons. The low-dimensional heterostructure is assumed to consist of a cylinder of GaAs surrounded by a Ga1¿xAlxAs barrier considering the lim- iting cases of 1D, 2D and 3D confinements. Theoretical results are given as functions of the Al concentration in the Ga1¿xAlxAs barrier, radii, lengths, magnetic fields and applied hydrostatic pressure. We have studied the role played by each of this parameters and the competition between them, finding that the geometrical confinement and Al concentration command the behavior of the electron-effective Land ¿e g|| factor. Present theoretical results are in very good agreement with experimental reports and with previous theoretical results.MaestríaMAGISTER EN CIENCIAS - FÍSIC

Hydrostatic pressure effects on the Landé g∥ factor in GaAs–Ga1−xAlxAs quantum heterostructures under applied magnetic fields

We have performed a theoretical study of the hydrostatic pressure effects on the conduction-electron Landé g∥ factor in GaAs–Ga1−xAlxAs quantum heterostructures (QHs) under the influence of applied magnetic fields. Numerical calculations are performed by using the Ogg–McCombe effective Hamiltonian, which include nonparabolicity and anisotropy effects for the conduction-band electrons. The QHs is assumed to consist of a finite-length cylinder of GaAs surrounded by Ga1−xAlxAs barrier. Theoretical results are given as functions of the radii, lengths, hydrostatic pressure, and applied magnetic fields. We have studied the competition between the geometrical and magnetic confinement versus hydrostatic pressure effects, finding that the geometrical confinement commands the behavior of the g∥ factor. Present theoretical results are in very good agreement with previous experimental and theoretical reports in GaAs–Ga1−xAlxAs heterostructures.Departamento Administrativo de Ciencia, Tecnología e Innovación [CO] Colciencias1106-452-21296Control cuántico de las propiedades electrónicas y de espín en nanoestructuras inorgánicas, orgánicas y biológicasn

Magneto-Optics Effects: New Trends and Future Prospects for Technological Developments

Magneto-optics (MO) is an effervescent research field, with a wide range of potential industrial applications including sensing, theranostics, pharmaceutics, magnetometry, and spectroscopy, among others. This review discusses the historical development, from the discovery of MO effects up to the most recent application trends. In addition to the consolidated fields of magnetoplasmonic sensing and modulation of optical signals, we describe novel MO materials, phenomena, and applications. We also identified the emerging field of all-dielectric magnetophotonics, which hold promise to overcome dissipation from metallic inclusions in plasmonic nanostructures. Moreover, we identified some challenges, such as the need to merge magneto-chiroptical effects with microfluidics technology, for chiral sensing and enantioseparation of drugs in the pharmaceutical industry. Other potential industrial applications are discussed in light of recent research achievements in the available literature

Magneto-Optics Effects: New Trends and Future Prospects for Technological Developments

Magneto-optics (MO) is an effervescent research field, with a wide range of potential industrial applications including sensing, theranostics, pharmaceutics, magnetometry, and spectroscopy, among others. This review discusses the historical development, from the discovery of MO effects up to the most recent application trends. In addition to the consolidated fields of magnetoplasmonic sensing and modulation of optical signals, we describe novel MO materials, phenomena, and applications. We also identified the emerging field of all-dielectric magnetophotonics, which hold promise to overcome dissipation from metallic inclusions in plasmonic nanostructures. Moreover, we identified some challenges, such as the need to merge magneto-chiroptical effects with microfluidics technology, for chiral sensing and enantioseparation of drugs in the pharmaceutical industry. Other potential industrial applications are discussed in light of recent research achievements in the available literature

Temperature and hydrostatic pressure effects on the binding energy of magnetoexcitons bound to ionized-donor impurities in GaAs/AlxGa1−xAs quantum wells

We have studied the quantum confinement, applied hydrostatic pressure, and temperature dependence of the binding energy of a magnetoexciton bound to a ionized-donor impurity in GaAs/Ga1−xAlxAs quantum wells, taking into account the spin-orbit coupling between the (Γv7,Γv8) and (Γc7,Γc8) multiplets, including the Al concentration, temperature, and applied hydrostatic pressure dependence on the electron effective-mass me(P,T,x) and the Landé ge(P,T,x) factor by using the well known five-level k · p theory. We have found that the binding energy Eb increases with the strong geometrical confinement, as well as with the growth-direction applied magnetic field. The presence of the ionized-donor impurity clearly increases the heavy-hole exciton binding energy. The quantum confinement, in part determined by the height of the barrier potential-well, i.e., by the Al concentration and the hydrostatic pressure, contributes to enhance the binding energy. Also, we found that the exciton binding energy increases with temperature due to the different temperature band-gap dependence of the well and barrier regions, which conduces to a net increasing of the potential barrier. Also, we have obtained a good agreement with previous theoretical and experimental findings. We hope the present work must be taken into account for the understanding of experimental reports and for the design of optoelectronic devices with multiple technological purposes.Departamento Administrativo de Ciencia, Tecnología e Innovación [CO] Colciencias1106-452-21296Control cuántico de las propiedades electrónicas y de espín en nanoestructuras inorgánicas, orgánicas y biológicasn