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In a future society with limited access to fossil fuels, technologies for efficient on demand delivery of renewable energy are highly desirable. In this regard, methods that allow for solar energy storage and on demand solar driven energy generation are particularly relevant since the sun is the most abundant energy source.
Disorder and chaos are ubiquitous phenomena that are mostly unwanted in applications. On the contrary, they can be exploited to create a new technology. In this talk I will summarize my research in this field, discussing chaotic energy harvesting, nonlinear stochastic resonance and complex nanolasers.
Thermal processes play an essential role in the production and processing of countless industrial and consumer products. Narrow bandwidth near infrared (NIR) light allows contactless transfer of energy with a high power per area that can be tailored to the needs of the application. With arrays of VCSELs (Vertical-Cavity Surface Emitting Laser diodes), NIR emitters can be realized that provide heat...
The objective of this tutorial is to discuss ultimate opto-electronic device limitations while highlighting recent advances and solutions to overcome them for two key devices at the nanoscale; namely lasers and electro-optic modulators.
In this paper we present novel techniques to redesign materials of interior virtual scenes. Users would need to provide no more than one example image which has desirable color distribution. Our system modifies the materials of the scene so that the rendering result would similar to the color style of the example image. We first extend ISODATA clustering algorithm to retrieve representative viewpoints...
We evaluated a data set consisting of 38 different materials — threats and non-threats — to determine whether there are signatures detectable in CT systems equipped with energy-resolving photon-counting detectors that would help the detection task. Data with such detectors was collected in a lab setup using a Compton spectrometer and simple transmission measurements through samples of known material...
Solar cells based on II–VI semiconductors are among the leading candidates for low-cost photovoltaic conversion of solar energy due to their high absorption coefficients and therefore the low material consumption for their production. To understand the basics of photovoltaic (PV) cells, several types of simulation software are available. This work reports on the analysis of Zinc Telluride (ZnTe) thin...
In this work, an approach of realizing fiber-based near infrared bandpass filter with parasitic bandgaps suppression is proposed. By doping the core of an all-solid photonic bandgap fiber with lower refractive index material, single-mode light is confined in the main bandgap centered at 1.0 μm wavelength region. Light guiding in higher order bandgaps is suppressed due to the coupling of light to the...
Optical bandwidth of photonic multiple quantum well structure is analytically computed subject to the polarized incidence of electromagnetic wave on the structure. Both p-polarization (TE mode) and s-polarization (TM mode) are considered to observe the tuning of bandwidth by suitable variation of structural parameters. Semiconductor heterostructure is considered as material system for simulation purpose,...
Monte Carlo estimation of the giant-dipole-resonance (GRN) photoneutrons inside the Elekta Precise LINAC head (emitting a 15 MV photon beam) were performed using the MCNP6 (general-purpose Monte Carlo N-Particle code, version 6). Each component of LINAC head geometry and materials were modelled in detail using the given manufacturer information. Primary photons generate photoneutrons and its transport...
Energy resolved photon-counting detectors could achieve more than one spectral measurement. The goal of this study is to investigate, with experiment, the ability to decompose five materials using energy discriminating detectors and multiple discriminant analysis (MDA). A small field-of-view multi-energy CT system was built. Linear attenuation coefficient was considered as features of multiple energy...
A double-layer W/Bi sheet is proposed for a X-ray radiation protection at the energy range of 70 keV to 90 keV. Comparison of X-ray transmission intensity between simulation and measurement results is presented. Transmission intensity of X-rays with various incident angles is observed. This designed W/Bi sheet, only 0.14 mm thick, provides the same X-ray protection properties as the standard 0.50...
We observe large enhancement of nondegenerate two-photon absorption compared to the degenerate case. We use this to sensitively detect and image mid-IR light with simple uncooled photodiodes. The enhancement also applies to 2-photon emission and gain.
We report stopped-light nanolasing in active planar plasmonic waveguides at near-infrared frequencies. Studying its spatial, temporal and spectral signatures we reveal that, in the absence of cavity-induced feedback, the subwavelength lasing mode forms dynamically as a phased-locked superposition of quasi dispersion-free waveguide modes. This mechanism proves remarkably robust against surface roughness...
Biomedical imaging has become one of the most relied-upon tools in health-care for diagnosis and treatment of human diseases. The evolution of medical imaging from plain radiography (radioisotope imaging), to x-ray imaging, to computer-assisted tomography (CAT scans), to ultrasound imaging, and to magnetic resonance imaging (MRI) has led to revolutionary improvements in the quality of healthcare available...
Image in nuclear medicine represents a primordial material in diagnostics and quantitative studies. However, its quality is influenced by factors such as attenuation, scatter and partial volume effects. In the present work we are interested in investigating quantitatively the scatter effect on the spatial resolution and the energy spectrum using the Monte Carlo simulation.
InxGa1−xN/GaN quantum dot intermediate band solar cell (QD-IBSC) is a promising candidate for the purpose of efficiency improvement of solar cells. In this work, the influences of interdot distance, quantum dot size and indium content of InxGa1−xN/GaN QD-IBSC on the position and width of the intermediate bands are investigated by solving Schrödinger equation using Kronig-Penney model. Finally the...
We report single-photon emission from electrically driven site-controlled InGaN/GaN dot-in-nanowires, fabricated from a planar single InGaN quantum well LED using a top-down approach. Each dot-in-nanowire's formation site, diameter, height and material compositions were precisely controlled.
We design a novel core-shell nanocone structure that allows full absorption of sunlight in an iron oxide photoanode. The photocurrent approaches 12.5mA/cm2 within an iron oxide thickness of 20nm, verified by full-field electromagnetic simulation.
We examine numerically and experimentally photonic band-gaps in liquid-like two dimensional photonic materials. Subwavelength dielectric rods and holes are randomly placed with Monte Carlo simulations, fabricated on silicon-on-insulator chips, and measured in near infrared wavelengths.
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