Seminars and Events
Coordinator: Alvaro Blanco
11 July 2017, 12:00 h. Sala de Seminarios, 182
Nanophotonics Research at Sandia: Nano light sources and topological photonics
Ganapathi (Ganesh) Subramania
Semiconductor materials and device sciences, Sandia National Laboratories
Nanophotonic architectures such as photonic crystals and metamaterials have become key players in modern photonics. They offer hitherto unprecedented capabilities combined with great versatility to control various properties of light¬ -propagation, polarization, emission and photon statistics. They have become increasingly important for chipscale photonics. In this talk, I will present research carried out along with my colleagues in this area using photonic crystals and metamaterials at Sandia. In particular, I will provide a broad overview of our work covering three-dimensional photonic crystals operating in the visible, light emission from three-nitride nanowire two-dimensional photonic crystal arrays, metal-dielectric epsilon-near-zero metamaterials at visible wavelengths and non-resonant, broadband ultrasubwavelength light confinement structures. I will follow this overview with two of our more recent efforts. One, is on fabrication and spectroscopy of site-selective III-nitride quantum dots for quantum light sources using photo-electro-chemical etch. This approach for deterministic placement can potentially lead to quantum light sources with deterministic properties, important for quantum information processing. The other is on our efforts on achieving topologically non-trivial photonic structures. Topological photonic structures exhibit one-way scatter-free light transport that can have important applications in optical and quantum communications.
25 April 2017, 11:30 h. Salón de Actos
NETWORKS THEORY: HOW THINGS ARE CONNECTED
Yeshiva University, NY USA
In this seminar I will present some basic ideas of networks’ theory and their areas of current application in different fields of science
In particular I will present some of main theoretical models of networks and of network formation , and I will present some applications to robustness and to spreading and diffusion of processes in networks.
31 January 2017, 12:00 h. Sala de Seminarios, 182
Unveiling Natural Optical Activity of Disordered Media
F. A. Pinheiro
Instituto de Física, Universidade Federal do Rio de Janeiro, Brasil
The concept of chirality, introduced by Lord Kelvin in order to describe geometrical objects that cannot superimposed with their mirror image, is ubiquitous in the natural world. Despite substantial efforts to understand the optical properties of naturally occurring chiral media and to design artificial ones, disordered media remain an overlooked class of chiral systems. Since disordered systems lack centre and plane of mirror symmetry, they should exhibit natural optical activity. However, previous experimental evidence of natural optical activity in random media has never been attributed to the intrinsic chirality of a random system, but rather to alternative explanations, such as surface contamination by unwanted chiral substances.
Here, we demonstrate natural optical activity due to intrinsic geometric chirality in disordered, diffusive scattering systems, consisting of plasmonic resonators. We employ a microscopic electromagnetic wave transport theory, and derive an expression for the rotatory power and the spatial dichroism of a medium consisting of randomly distributed pointlike scatterers. By means of a systematic statistical analysis of natural optical activity in random media, we argue that the standard deviation of both rotatory power and spatial dichroism are strongly dependent on the density of scatterers and the scattering mean free path. We independently confirm our results by full-wave finite element simulations and show that disordered ensembles of plasmonic nanoparticles can exhibit dichroism more than an order of magnitude higher than in helical configurations with the same particle density.