Title

Department of Electronics,
Engineering Institute of Technology,
University of Delhi South Campus,
India

“Analytical Analysis, Characterization and Simulation of Advanced MOSFET Design for Improved SCE Suppression, Hot Carrier Reliability and Analog Performance”

Analytical analysis and characterization of advanced MOSFET design has been discussed based on the improved short-channel effects and the hot carrier reliability for the analog circuit applications. The control of short channel effects and the impact of high substrate doping has been considered while designing a new structure to show the   superiority over the conventional structures. Various issues like the control of series source/drain resistance, junction capacitance and carrier transport efficiency etc. have also been discussed in detail. In MOSFET scaling issues like high gate leakage current, enhanced channel mobility and carrier transport efficiency has also been included in the analysis.

“Correlations between nanostructure and light-emitting properties in InGaN/GaN epitaxial heterostructures”

In the first part of this talk I will present the results of an experimental investigation of light emitting nano-structured epitaxial layers based on indium gallium nitride (InxGa1-xN/GaN). This group III-nitride ternary semiconductor alloy system is used as the active layer in a new class of solid state optoelectronic devices, including light emitting diodes (LEDs) and laser diodes (LDs), under development to operate in the visible and ultraviolet regions of the lectromagnetic spectrum. The issues of accurate measurement of the InN mole fraction (x), the influence of composition, strain and morphological features in the structural and optical properties will be addressed, as well as the controversial topic of phase segregation in InxGa1-xN samples grown by metal organic chemical vapour deposition (MOCVD). The approach taken to gain an insight regarding this material system was to integrate information provided by several complementary structural and optical characterization techniques, specifically: 1) advanced structural characterization by atomic force microscopy (AFM), canning/transmission electron microscopy (SEM/TEM), X-ray diffraction (XRD) and Rutherford Backscattering spectrometry (RBS); 2) Optical characterisation at complementary length scales by photoluminescence (PL), and athodoluminescence (CL) spectroscopy and confocal microscopy/spectroscopy.
Based on the results obtained, simple interpretation models to describe the structural and optical features are proposed, with a particular emphasis on the establishment of direct correlations between both. It is concluded that icroscopic strain and morphology-related phenomena are crucial to interpret the experimental results [1]. On the second part of the talk I will present a novel approach to design hybrid heterostructures that incorporate colloidal nanocrystals (NCs) into nitride MQWs. The laboratory and stage for our strategy is provided by the spontaneous formation of intrinsic nanoscale defects (Inverted Hexagonal Pits) in indium-containing III-nitride heterostructures. Our results show that it possible to spatially confine nanoparticles prepared by wet chemical synthesis, or sets of distinct nanoparticles within those IHPs, at engineered depths and spacings, in order to create frameworks of spatially localized functional nano-objects. The proof-of-concept experiments were performed using the interfacial capillarity force present during the evaporation of the nanocrystals suspension. Control of the number of nanoparticles in each IHP and of the lateral inter-particle separation provides an experimental platform for multiple interaction studies and the investigation of the intrinsic properties of individual nanocrystals [2]. The wide variety of resulting nanostructure assemblies controlled on top of an efficient light emitting heterostructure present new challenges and interesting opportunities to study light-mater coupling and “exotic” heterostructures hardly possible to obtain by other means.

“LIGO (Laser Interferometer Gravitational-Wave Observatory): How can optics be used to listen to gravitational waves?”

The goal of LIGO, the Laser Interferometer Gravitational-Wave Observatory, is to detect and study gravitational waves of astrophysical origin. Achieving this goal will mark the opening of a new window on the universe, with the promise of new physics and astrophysics. LIGO, a joint Caltech-MIT project supported by the National Science Foundation, operates three multi-kilometer optical nterferometers at two widely separated sites in the United States. The initial LIGO detectors were designed to be sensitive to gravitational waves in the frequency band 40-7000 Hz, and capable of detecting a gravitational wave strain amplitude as small as 10-21. I will report on recent improvements (known as Enhanced LIGO) that are currently being implemented and commissioned on two LIGO interferometers. My seminar will focus on results on the Pre-Stabilized Lasers, emitting 35 W of single frequency 1064 nm light,and on the Input Optics, including the mode cleaner and the high power Faraday isolator

“Ultra-small and ultra-fast all-optical devices based on advanced technologies
of photonic crystal and quantum dot”

We have developed ultra-small and ultra-fast all-optical devices, i.e., a symmetric
Mach-Zehnder type all-optical switch (PC-SMZ) and an optical digital flip-flop device (PC-FF) [1]. These devices are based on nanophotonic technologies of GaAs-based two-dimensional (2D) photonic crystal (PC) waveguides and InAs quantum dots (QDs). The 2D-PC waveguides in a GaAs slab suspended in air (air-bridge structure) provide nano-scale optical circuits due to their strong optical confinement. The QD embedded in the PC waveguides plays the role of a phase-shifter with its optical nonlinearity. In the 1st phase of our work, ultra-fast (~20ps) and ultra-low energy (~100 fJ) switching has been demonstrated using the PC-SMZ, as shown in Fig. 1. We have recently achieved repetitive perations of the PC-SMZ with 40GHz pumping pulse [2]. In the 2nd phase, the concept of the PC-FF based on the dual PC-SMZs for providing a latch function has been proposed for a future ultra-fast optical digital processor. One of the priority subjects is to establish a new design method, i.e., topology optimization method of the 2DPC waveguide with wide/flat bandwidth, high transmittance and low reflectivity [3]. Another one is to develop a technique for selective-area growth of QDs with a metal-mask/MBE method for high-density and highly uniform QDs with different absorption wavelengths in different areas [4]. A successful fabrication of PC-FF has been achieved, as shown in Fig. 2. These developments will pave the way for innovative all-optical integrated devices based on PCs and QDs, which can provide optical digital signal processing required in the future photonic network.

Faculty Candidate
Dr. Tilo Reinert

Faculty of Physics and Geosciences
University of Leipzig, Germany

“From Micro- to Nanoprobes Applications of High Energy Focused Ion Beams in the Life Sciences”

High energy focused ion beams, known as nuclear microprobes, are widely used as a versatile analytical tool in a broad range of scientific fields which spans from material sciences to life sciences. One of its main applications is the elemental analysis with excellent quantitative accuracy at detection limits in the range of parts per million combined with spatial resolutions down to about one micron. Thus, a nuclear microprobe is well suited for trace element analysis in biomedical research. I will present selected applications in neurosciences; i) a comprehensive study on the iron homeostasis of neurons that exhibit a reduced vulnerability to degeneration, ii) a high resolution trace element analysis of neuromelanin – a pigment that aroused suspicion as a contributing factor to neuronal damage in Parkinson’s disease, and iii) a study on the zinc levels in the hippocampus of opiate abusers. These examples shall also point out the quest for a steady improvement of microprobe performances resulting in a nanoprobe. The efforts for the Leipzig high energy focused ion beam are shortly summarized.
Finally, a prospective application of proton beam writing in network neuroscience is given. For the study of neuronal circuits multi electrode arrays are used to record neuronal activity. Therefore, a confined cell growth of single neurons on the electrodes is desired which additionally provides predefined pathways for axonal connections. Here, the technique of proton beam writing is a promising approach.

Faculty Candidate
Dr. Cyril Hnatovasy

OZ Optics Ltd.
Ottawa, Canada

“Femtosecond light-induced nanoscale architectures for photonics and biosensing applications”

Traditionally, it has been assumed that optical fabrication techniques are restricted by the diffraction limit of the light used. Using novel ultrahigh resolution diagnostics we have demonstrated that when glass is irradiated with a series of focused linearly polarized femtosecond (1 fs = 10-15 s) laser pulses, a periodic array of planar nanocracks can be created around the focal region. These sub-wavelength architectures are the finest optically produced structural changes inside a pure transparent material. Interestingly, when the polarization direction of the femtosecond light is changed, old nanocracks are erased and simultaneously replaced with new ones whose orientation is solely determined by the polarization of the rewrite pulses. The erasure-rewriting cycle can be repeated thousands of times with little degradation in the quality of a newly recorded nanocrack array. The high degree of all-optical control over the light-induced nanoscale architectures reshapes the frontier of laser microfabrication and opens a new avenue for exciting applications in 3-D rewritable data storage for harsh environments (survives 1100ºC), embedded micro-optic arrays for interconnection and synthesis of light beams, microfluidics, and nanopatterning surfaces for biosensing.

Faculty Candidate
Dr. Farida Selim

“Study of Wide Band-Gap Semiconductors by Antimatter”

Outside high energy physics facilities, positron is the only antimatter that can be created in a laboratory. It provides an interesting research tool in fundamental and applied physics. Positron and its bound state with an electron “postronium” have been very useful to study atomic interactions and test quantum theories. In the area of materials science and semiconductors, it has been developed to a powerful tool for materials characterization and defect studies.  In this talk, after a quick overview I will show how accelerators and ion beams can be used to enhance defect spectroscopy in semiconductors by antimatter techniques. Then I will present my research in the area of study of new wide band gap semiconductors for optoelectronics and spintronics by means of positron annihilation, optical spectroscopy, and other techniques.

Faculty Candidate
Dr. Hedi Mattoussi

US Naval Research Laboratory,
Optical Sciences Division,
Washington, DC 20375

“CONJUGATION OF PHOTONIC QUANTUM DOTS TO BIO-REACTIVE MOLECULES: A Cross-Disciplinary Investigation Whereby Physics and Chemistry Tackle Biological Problems in Protein Tracking and Live Cell Imaging”

Inorganic nanocrystals have a large fraction of their atoms arrayed on their surfaces, and they are capped with bi-functional ligands to promote their compatibility with the surrounding environments (e.g., solvents or polymer matrices).  This makes their properties sensitive to that environment.  Semiconductor QDs, in particular, exhibit photoemission that can be highly sensitive to potential interactions with proximal dyes and metal complexes, via resonance energy transfer or charge transfer mechanism.  We have developed approaches based on non-covalent self-assembly to conjugate a variety of biomolecules to CdSe-ZnS core-shell QDs rendered water-soluble using multifunctional modular ligands.  We start with a description of the ligand design we have developed to cap QDs (as well as Au nanoparticles) and promote their transfer to aqueous media, along with the conjugation of these nanoparticles to proteins and peptides.  We then describe the use of peptides/proteins as bridges between CdSe-ZnS QDs and fluorescent dyes, Au nanoparticles and redox active metal complexes.  These configurations promote QD PL quenching via either energy transfer from QDs to Au-NPs or charge transfer between redox complexes and QDs.  For QD-Au-NP pairs the quenching was found to extend over distances beyond those allowed by conventional Förster resonance energy transfer.  We will discuss the use of these materials to design sensing assemblies that are specific for target proteins and small molecules in vitro.  We will also describe the use of QD-conjugates to image intracellular compartments.

Faculty Candidate
Dr.Ilya Grigorenko

Los Alamos National Laboratory,
New Mexico

“Discovery of nanodevices with the help of quantum design: can we write down the recipe if we are given a cake?”

Quantum optimal design of nanostructured materials is a modern approach aimed to reproduce the desired physical properties through the control of their electronic  eigenenergies and eigenfunctions. This can be achieved by an iterative optimization of the effective electron trapping potential. By using techniques based on linear response theories and efficient optimization procedures we provide optimized designs for some particular applications, such as single molecule detectors and energy storage in nanocapacitors. We have demonstrated that optimal design can improve the target functionality (e.g., the detector sensitivity) up to three orders of magnitude.

Faculty Candidate
Yuri V. Rostovtsev

“Coherent Control of Nonlinear Optics”

Using quantum coherent effects provides means to control nonlinear optical processes in various media. We predict several new effects: for example, forward Brillouin scattering and enhancement and control of coherent generation in the backward direction by applying only forward propagating fields. The applications range from development of hyper-dispersive materials, improvement of spatial resolution beyond diffraction limit to generation of squeezed and entangled light.

Dr. Shuping Wang

Department of Engineering Technology
University of North Texas
Denton, Texas

“Wavelength Division Multiplexing (WDM) in Fiber-Optic Communications”

WDM has been identified as one of the most promising technologies to meet the demand of dramatically increasing transmission capacity. The presentation will introduce the current technologies on the WDM system, sub-systems, and components. Theory and experimental results on Mux/DeMux, VMux, channel blockers, and channel monitors will be presented.

Dr. José Sánchez-Dehesa

Wave Phenomena Group
Polytechnic University of Valencia,
Spain

“Sound control by metafluids based on sonic crystals”

I will report on the behavior of periodic distributions of solid (or fluid) cylinders embedded in a nonviscous fluid (or gas) in the regime of large wavelengths (homogenization). Sonic crystals represent, in this limit, a class of acoustic metamaterials or metafluids whose acoustical properties can be tailored with practically no limitations. We have demonstrated that combination of two different solid materials in the lattice allows obtaining metafluids with a perfect matching of impedances with the surrounding background. We have also shown that anisotropic metamaterials are possible by using non-isotropic lattices.  These types of materials are candidates to achieve the recently proposed acoustic cloaking.

“Genetic information and conductivity of DNA molecules”

DNA molecule is an example of a complex natural system with intriguing properties. Genetic information is stored in the DNA segments called exon. These coding segments are separated by long non-coding regions called introns. It is still unclear, what is the biological role of the introns. In this talk I will explain why these two regions of DNA have very different conducting properties. Namely, the exons may exhibit metallic behavior but the introns are insulators.

“Astronomy at UNT”

Ron DiIulio, director of the astronomy labs and planetarium, will present an informal program describing several new facilities and programs that are coming on line at UNT. There will be a presentation describing the new multi-narrowband wavelength solar observatory, and the programs that are to be developed in association with its commission. Also, the UNT planetarium has recently completed a major upgrade with the installation of a Digistar III full-color projection system, the latest generation in digital projection technology.  To illustrate the technology, “Secrets of the Sun” will present an informative view of the latest discoveries in solar studies. Also, the Monroe Robotic Observatory will be the site from which a new program will be conducted by Dr. Ohad Shemmer.  The research will concentrate on exoplanet studies. Graduate students are currently being recruited for this program.

Dr. Usha Philipose

Department of Physics
University of North Texas
Denton, Texas

“Semiconductor Nanoscale Devices: Hope or Hype?”

One-dimensional nanostructures exhibit unique properties intrinsically associated with their low dimensionality and the quantum confinement effect. This talk will provide an overview of my research activities into their synthesis and characterization. In the first part of this talk, I will discuss the Vapor-Liquid-Solid growth mechanism for the synthesis of semiconductor nanowires of different compositions and sizes. Results of measurements on single nanowires showing unique properties of light emission and carrier transport will be presented. The effectiveness of these nanostructures for potential applications as photodetectors, spintronic devices and as efficient light emitting devices will be outlined. We will also look at a few challenges that need to be overcome before the "vision" of building devices starting at the atomic level can be fully realized.

Dr. Ohad Shemmer

Department of Physics
University of North Texas
Denton, Texas

“Multiwavelength Insights into the Nature of Weak Emission-Line Quasars at High Redshift”

The Sloan Digital Sky Survey has recently discovered 50 quasars at z=2.7-5.9 with weak or undetectable high-ionization emission lines in their UV spectra (WLQs). We present multiwavelength spectroscopic observations that enabled us to gain insights into the nature of these remarkable sources. We find that WLQs are unlikely to be dust-obscured quasars, broad-absorption line quasars, or high-redshift galaxies with apparent quasar-like luminosities due to gravitational lensing amplification. Additional monitoring data suggests that the weakness of the lines in WLQs cannot be explained by microlensing that amplifies the continuum relative to the emission lines in ordinary quasars. We also argue against the idea that WLQs are the long-sought high-redshift BL Lacertae objects. Instead, we suggest that WLQs are quasars with extremely high accretion rates that suppress the formation of the high-ionization emission lines. We discuss X-ray and near-infrared observations required to test this scenario with implications for emission line formation and the accretion process in active galactic nuclei.