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Full-Text Articles in Physics
Imaging Based Beam Steering For Optical Communication And Lidar Applications, Sajad Saghaye Polkoo
Imaging Based Beam Steering For Optical Communication And Lidar Applications, Sajad Saghaye Polkoo
Electronic Theses and Dissertations, 2020-
Optical beam steering is a key component in any application that requires dynamic (i.e. realtime control) of beam propagation through free-space. Example applications include remote sensing, spectroscopy, laser machining, targeting, Lidar, optical wireless communications (OWC) and more. The pointing control requirements for many of these applications can be met by traditional mechanical steering techniques; however, these solutions tend to be bulky, slow, expensive, power hungry and prone to mechanical failures leading to short component lifetimes. Two emerging applications, Lidar imaging and OWC, truly need improved beam-steering capabilities to flourish and support the advancement of self-driving cars or relieve the congestion …
Control Of Coherence In Attosecond Atomic Ionization, Saad Mehmood
Control Of Coherence In Attosecond Atomic Ionization, Saad Mehmood
Electronic Theses and Dissertations, 2020-
The motion of electrons in atoms, molecules, and in condensed matter unfolds on a time scale from the attosecond (1 as = 10-18 s) to several femtoseconds (1 fs= 10-15 s). The advent of attosecond light pulses has opened the way to the time-resolved study of electronic motion and of ionization processes using pump-probe spectroscopy. In this thesis, we examine three aspects of the ionization dynamics in poly-electronic atoms: i) the coherence of the emerging charged fragments, ii) two-photon ionization pathways, and iii) the reconstruction of photoionization amplitudes from experimental observable. We focus on the role of autoionizing states and …
Computational And Experimental Studies Of Adsorption And Reactions On Molybdenum Nitride And Silica Covered Ruthenium Surfaces, Muhammad Sajid
Computational And Experimental Studies Of Adsorption And Reactions On Molybdenum Nitride And Silica Covered Ruthenium Surfaces, Muhammad Sajid
Electronic Theses and Dissertations, 2020-
Fundamental studies of material surfaces are of continued interest to the development and improvement of many modern technologies, e.g. catalysis, energy efficient electronics, and high-capacity batteries etc. This dissertation targets two distinct sets of molecule-surface interactions relevant to the continued development of structure-property correlations using tools from Density Functional Theory with added verification from ultrahigh vacuum surface-science experiments. These include Haber-Bosch interactions at molybdenum-nitride surfaces and separation-dependent interactions between simple aromatics and Ru(0001) used to model a metal contact of Organic Electronic Devices (OEDs). In the first study, we focus on computational modelling of nitrogen fixation reactions on Mo- and …
Physics And Applications Of Space-Time Wave Packets, Murat Yessenov
Physics And Applications Of Space-Time Wave Packets, Murat Yessenov
Electronic Theses and Dissertations, 2020-
Space-time wave packets (STWP) constitute a broad class of pulsed optical fields that are rigidly transported in linear media without diffraction or dispersion, and are therefore propagation-invariant in absence of optical nonlinearities or waveguiding structures. Such wave packets exhibit unique characteristics, such as controllable group velocities in free space and exotic refractive phenomena. At the root of these behaviors is a fundamental feature underpinning STWP: their spectra are not separable with respect to the spatial and temporal degrees of freedom. Indeed, the spatio-temporal structure is endowed with angular dispersion, in which each spatial frequency is associated with a single prescribed …
Design Of A High-Power Terahertz Emitter Array Using A High-Temperature Superconductor, Ruqayyah Shouk
Design Of A High-Power Terahertz Emitter Array Using A High-Temperature Superconductor, Ruqayyah Shouk
Electronic Theses and Dissertations, 2020-
By applying a dc voltage V across the stack of intrinsic Josephson junctions naturally present in the high-temperature superconductor consisting of two parts bismuth, two parts strontium, one part calcium, two parts copper, and a bit more than eight parts oxygen, several groups have been able to obtain coherent THz emission at output powers in the µW range. In order to enhance the output power well into the mW range suitable for many applications, we have studied a compact design of a stand-alone mesa array with gold layers on the top and bottom of the superconductor. In this design, an …