A complex environment causes strong distortion of the field, inhibiting tasks such as imaging and communications in both the optical and radio-frequency (RF) region. In the optical regime, strong modal dispersion in highly multimode fiber (MMF) results in a scrambled output field in both space (intensity speckles) and time (spectral and temporal speckles). Taking advantage of the pulse shaping technique, spatial and temporal focusing has been achieved in this thesis, offering potential opportunities for nonlinear microscopy and imaging or space-division multiplexed optical communication through MMF. In the RF regime, multipath effect in wireless RF channel gives multiple echoes with random delay and amplitude attenuation at the receiver end. Static channel sounding and compensation with ultra-broadband spread spectrum technique resolves the issue by generating a peaking signal at the receiver, significantly improving the signal-to-noise/interference performance. However, the limited communication speed in the static approach makes it challenging for sounding and compensation in a dynamic channel. Here, we achieve real-time channel sounding and compensation for dynamic wireless multipath channel with 40 micro-seconds refresh rate by using a fast processing field programmable gate array (FPGA) unit, providing potential opportunities for mobile communications in indoor, urban, and other complex environments. Furthermore, by combining broadband photonics and RF radar technologies, a high depth and transverse resolution wide bandwidth (15 GHz) W-band (75 - 110 GHz) photonic monopulse-like radar system for remote target sensing is demonstrated, offering prospects for millimeter wave 3-D sensing and imaging.

<p>Optimization and Machine learning (ML) have emerged as two positively disruptive methodologies and have thus resulted in unprecedented applications in several domains of technology. In recent years, ML has forayed into physical sciences and provided promising outcomes thanks to its ability in representing and generalizing complex functions to reveal underlying relations among variables describing a system. By casting ML as an optimization task, we first focus on its application in solving quantum many-body problems. Leveraging the power of quantum computation, we develop hybrid quantum machine learning protocols and implement benchmark tests to calculate the band structures of two-dimensional materials. We also show how this method can be used to estimate the critical point for a quantum phase transition. One  hurdle in such techniques is related to parameter optimization, wherein to obtain the desired result, the parameters have to be optimized, which can be computationally intensive. For a particular class of problem and a choice of algorithm, we deduce a simple parameter setting rule. This rule is projected as a heuristic and is validated numerically for several problem instances. Finally, by venturing into thermal photonics, a framework that takes advantage of the spectral and spatial information of hyperspectral thermal images to establish a completely passive machine perception, titled HADAR is presented. A conventional deep neural network is developed that utilizes the governing equation of HADAR and its performance in semantic segmentation is demonstrated. Altogether, this report establishes the need for creative algorithms that exploit modern hardware to solve complex problems that were previously deemed unsolvable.</p>

The design of a low cost electronically steered array feed (ESAF) is implemented and tested. The ESAF demonstrated satellite tracking capabilities over four degrees. The system was compared to a commercial low-noise block downconverter (LNBF) and was able to receive the signal over a wider angle than the commercial system. Its signal-to-noise ratio (SNR) performance was poor, but a proof of concept for a low cost ESAF used for tracking is demonstrated. Two compact low profile dual circularly polarized (CP) reflector feed antenna designs are also analyzed. One of the designs is a passive antenna dipole array over an electromagnetic band gap (EBG) surface. It demonstrated high isolation between ports for orthogonal polarizations while also achieving quality dual CP performance. Simulations and measurements are shown for this antenna. The other antenna was a microstrip cross antenna. This antenna demonstrated high gain and quality CP but had a large side lobe and low isolation between ports. A global positioning system (GPS) denied multiple input multiple output (MIMO) radar for unmanned aerial vehicles (UAVs) is simulated and tested in a physical optics scattering model. This model is developed and tested by comparing simulated and analytical results. The radar uses channel matrices generated from the MIMO antenna system. The channel matrices are then used to generate correlation matrices. A matrix distance between actively received correlation matrices to stored correlation matrices is used to estimate the position of the UAV. Simulations demonstrate the ability of the radar algorithm to determine its position when flying along a previously mapped path.

A main challenge in the field of special effects is to create special effects in real time in a way that the user can preview the effect before taking the actual picture or movie sequence. There are many techniques currently used to create computer-simulated special effects, however current techniques in computer graphics do not provide the option for the creation of real-time texture synthesis. Thus, while computer graphics is a powerful tool in the field of special effects, it is neither portable nor does it provide work in real-time capabilities. Real-time special effects may, however, be created optically. Such approach will provide not only real-time image processing at the speed of light but also a preview option allowing the user or the artist to preview the effect on various parts of the object in order to optimize the outcome. The work presented in this dissertation was inspired by the idea of optically created special effects, such as painterly effects, encoded in images captured by photographic or motion picture cameras. As part of the presented work, compact relay optics was assessed, developed, and a working prototype was built. It was concluded that even though compact relay optics can be achieved, further push for compactness and cost-effectiveness was impossible in the paradigm of bulk macro-optics systems. Thus, a paradigm for imaging with multi-aperture micro-optics was proposed and demonstrated for the first time, which constitutes one of the key contributions of this work. This new paradigm was further extended to the most general case of magnifying multi-aperture micro-optical systems. Such paradigm allows an extreme reduction in size of the imaging optics by a factor of about 10 and a reduction in weight by a factor of about 500. Furthermore, an experimental quantification of the feasibility of optically created special effects was completed, and consequently raytracing software was developed, which was later commercialized by SmARTLens(TM). While the art forms created via raytracing were powerful, they did not predict all effects acquired experimentally. Thus, finally, as key contribution of this work, the principles of scalar diffraction theory were applied to optical imaging of extended objects under quasi-monochromatic incoherent illumination in order to provide a path to more accurately model the proposed optical imaging process for special effects obtained in the hardware. The existing theoretical framework was generalized to non-paraxial in- and out-of-focus imaging and results were obtained to verify the generalized framework. In the generalized non-paraxial framework, even the most complex linear systems, without any assumptions for shift invariance, can be modeled and analyzed.

Необходимость в написании программы для расчета рассеянного поля телом вращения возникла в связи с неоднозначностью решения рассеянного поля таких объектов средствами электродинамического моделирования FEKO и Ansoft HFSS. В частности, в HFSS при повороте объекта (конуса) и соответствующем изменении характеристик падающей волны (направления распространения и поляризации) количество сегментов могло меняться более, чем на порядок. Отметим, что в качестве подхода к решению использовался метод физической оптики. Трудности расчета в FEKO вызваны по большей части ресурсами компьютера, а также сложностью последующей трактовки и математической обработки полученных результатов. Программа, описываемая в работе, позволит подойти к решению рассеянного на теле вращения поля более индивидуально и избежать таких неоднозначностей, что могут встречаться при расчетах в пакетах электродинамического моделирования. По результатам рассмотрения ряда задач сделан выбор в пользу метода физической оптики и его численной реализации на базе алгоритмов MATLAB. / The solution of diffraction from perfectly conducting convex solids of revolution is considered. The main aim is obtainment of an optimal approach for diffraction solution from large-scale solids. The implementation of a numerical solution of diffraction with physical optics method using MATLAB is considered. The realized program allows description of the solid of revolution with the analytic form equation of the curve. The possibility of curve description with a few functions defined on disjoint intervals is taken into consideration. The surface meshing with the required value is assured. The measure method of scattering characteristics is touched upon. The experimental results of the solid with three equations of curve are presented. The results of MATLAB modeling are compared with the experimental ones. The upgradability of mathematical modeling algorithms is proposed.

[pt] Este trabalho tem como objetivo aplicar uma técnica de síntese ótica de lentes dielétricas circularmente simétricas, que são iluminadas por uma fonte pontual com diagrama circularmente simétrico. A interface da lente (interface do dielétrico-ar) será modelada utilizando as aproximações da Ótica Geométrica e da Física Ótica. Da Ótica Geométrica, o controle da densidade de potência em campo distante é obtido pela aplicação de conservação de energia no interior dos tubos de raios que emergem do centro de fase da fonte e a determinação da direção dos raios que emergem da superfície do dielétrico é obtida através da aplicação da Lei de Snell para os raios incidentes na interface. Da Física Ótica, é possível obter as correntes elétrica e magnética na superfície externa da lente para determinar o campo radiado na integração dessas correntes pela superfície a partir da suposição de que as dimensões da lente e da curvatura da interface sejam muito maiores que um comprimento de onda no espaço livre. Devido a simetria circular, simplificações na formulação e nos esquemas numéricos para a solução serão apresentadas, resultando em técnica de projeto mais eficientes. A descrição da superfície da interface da lente é obtida através de técnica numérica. / [en] This work aims to apply a technique of optical synthesis of symmetrically circular dielectric lenses, which are illuminated by a point source with a symmetrically circular diagram. The lens interface (dielectric-air interface) will be modeled using the approximations of Geometric Optics and Physical Optics. From Geometric Optics, control of the power density in the far field is obtained by applying energy conservation inside the ray tubes that emerge from the phase center of the source and the determination of the direction of the rays emerging from the dielectric surface is obtained through the application of Snell’s law for the incident rays at the interface. From Physical Optics, it is possible to obtain the electric and magnetic currents on the external surface of the lens to determine the radiated field in the integration of these currents along the surface assuming that the lens dimensions and interface curvature are much larger than a wavelength in free space. Due to circular symmetry, simplifications in formulation and numerical schemes for the solution will be presented, resulting in a more efficient design technique. The description of the lens interface surface is obtained through numerical technique.

In this study, a computer code is developed in MATLAB&reg / to compute the Radar Cross Section (RCS) of arbitrary shaped complex targets by using Physical Optics (PO) and Modified PO. To increase the computational efficiency of the code, a novel fast integration procedure for oscillatory integrals, called Levin&rsquo / s integration, is applied to PO integrals. In order to improve the performance of PO near grazing angles and to model diffraction effects, a method called PO with Modified Surface Normal Vectors is implemented. In this method, new surface normals are defined to model the diffraction mechanism. Secondary scattering mechanisms like multiple scattering and shadowing algorithms are also included into the code to obtain a complete RCS prediction tool. For this purpose, an iterative version of PO is used to account for multiple scattering effects. Indeed, accounting for multiple scattering effects automatically solves the shadowing problem with a minor modification. Therefore, a special code for shadowing problem is not developed. In addition to frequency domain solutions of scattering problems, a waveform analysis of scattered fields in time domain is also comprised into this thesis. Instead of direct time domain methods like Time Domain Physical Optics, a Fourier domain approach is preferred to obtain the time domain expressions of the scattered fields. Frequency and time domain solutions are obtained for some simple shapes and for a complex tank model for differently polarized incident fields. Furthermore, a statistical analysis for the scattered field from the tank model is conducted.

<p>There is growing interest in the use of nanosecond surface dielectric barrier discharge (ns-SDBD) actuators for high-speed (supersonic/hypersonic) flow control. A plasma discharge is created using a nanosecond-duration pulse of several kilovolts, and leads to a rapid heat release and a complex three-dimensional flow field. Past work has been limited to qualitative visualizations such as schlieren imaging, and detailed measurements of the induced flow are required to develop a mechanistic model of the actuator performance. </p><p><br></p><p></p><p>Background-Oriented Schlieren (BOS) is a quantitative variant of schlieren imaging and measures density gradients in a flow field by tracking the apparent distortion of a target dot pattern. The distortion is estimated by cross-correlation, and the density gradients can be integrated spatially to obtain the density field. Owing to the simple setup and ease of use, BOS has been applied widely, and is becoming the preferred density measurement technique. However, there are several unaddressed limitations with potential for improvement, especially for application to complex flow fields such as those induced by plasma actuators. </p><p></p><p>This thesis presents a series of developments aimed at improving the various aspects of the BOS measurement chain to provide an overall improvement in the accuracy, precision, spatial resolution and dynamic range. A brief summary of the contributions are: </p><p>1) a synthetic image generation methodology to perform error and uncertainty analysis for PIV/BOS experiments, </p><p>2) an uncertainty quantification methodology to report local, instantaneous, a-posteriori uncertainty bounds on the density field, by propagating displacement uncertainties through the measurement chain,</p><p>3) an improved displacement uncertainty estimation method using a meta-uncertainty framework whereby uncertainties estimated by different methods are combined based on the sensitivities to image perturbations, </p><p>4) the development of a Weighted Least Squares-based density integration methodology to reduce the sensitivity of the density estimation procedure to measurement noise.</p><p>5) a tracking-based processing algorithm to improve the accuracy, precision and spatial resolution of the measurements, </p><p>6) a theoretical model of the measurement process to demonstrate the effect of density gradients on the position uncertainty, and an uncertainty quantification methodology for tracking-based BOS,</p><p>Then the improvements to BOS are applied to perform a detailed characterization of the flow induced by a filamentary surface plasma discharge to develop a reduced-order model for the length and time scales of the induced flow. The measurements show that the induced flow consists of a hot gas kernel filled with vorticity in a vortex ring that expands and cools over time. A reduced-order model is developed to describe the induced flow and applying the model to the experimental data reveals that the vortex ring's properties govern the time scale associated with the kernel dynamics. The model predictions for the actuator-induced flow length and time scales can guide the choice of filament spacing and pulse frequencies for practical multi-pulse ns-SDBD configurations.</p>

To investigate near-eld contributions for installed antennas, an in-house code iswritten to incorporate near-eld terms in Shooting and Bouncing Rays (SBR). SBRis a method where rays are launched toward an object and scatter using GeometricalOptics (GO). These rays induce currents on the object, from which the totalscattered eld can be found.To gauge the eect of near-eld terms, the in-house code can be set to excludenear-eld terms. Due to this characteristic, the method is named SBR Includingor Excluding Near-eld Terms (SIENT). The SIENT implementation is thoroughlydescribed. To make SIENT more exible, the code works with triangulated meshesof objects. Antennas are represented as near-eld sources, allowing complex antennasto be represented by simple surface currents. Further, some implementedoptimizations of SIENT are shown.To test the implemented method, SIENT is compared to a reference solution andcomparable commercial SBR solvers. It is shown that SIENT compares well to thecommercial options. Further, it is shown that the inclusion of near-eld terms actsas a small correction to the far-eld of the installed antenna. / För att undersöka närfältsbidrag för installerade antenner, har en kod skrivits för‌att ta med närfältstermer i Shooting Bouncing Rays (SBR). SBR är en metod där strålar (”rays”) skjuts mot ett object och sprids via Geometrisk Optik (GO). Dessa strålar inducerar strömmar på objectet, från vilka det totala sprida fältet kan hittas. För att undersöka bidraget från närfältstermer, så kan koden exkludera dessa. På grund av denna karaktär, kallas koden SBR Including or Excluding Near-field Terms (SIENT). Implementationen av SIENT beskrivs utförligt. För att göra SIENT mer flexibel, arbetar SIENT med triangulerade nät av objekt. Antenner representeras av närfältskällor, vilket låter komplexa antenner representeras med enkla yt-strömmar.Implementerade optimeringar av SIENT visas också.För att testa den implementerade metoden, jämförs SIENT med en referenslösning och jämförbara kommerciella SBR-lösare. Det visas att SIENT överensstämmer bra med kommerciella alternativ. Det visas också att närfältstermer agerar som enmindre korrektion till fjärrfältet av den installerade antennen.

<p>Dipole-dipole interactions are ubiquitous fundamental physical phenomena that govern physical effects such as Casimir Forces, van der Waals forces, collective Lamb shifts, cooperative decay, and resonance energy transfer. These interactions are associated with real and virtual photon exchange between the interacting emitters. Such interactions are crucial in realizing quantum memories, novel super-radiant light sources, and light-harvesting devices. Owing to this, the control and modification of dipole-dipole interactions have been a longstanding theme. The electromagnetic environment plays a crucial role in enhancing the range and strength of the interactions. This work focuses on modifying the nanophotonic environment near interacting emitters to enhance dipole-dipole interactions instead of spontaneous emission. To this end, we focus on engineering the nanophotonic environment to enhance the strength and range of dipole-dipole interactions between an ensemble of emitters. We explore ordered and disordered nanophotonic structures. We experimentally demonstrate long-range dipole-dipole interactions mediated by surface lattice resonances in a periodic plasmonic nanoparticle lattice. Further, the modified electromagnetic environment reduces the apparent dimensionality of the interacting system compared to non-resonant in-homogeneous and homogeneous environments. We also develop a spectral domain inverse design technique for the accelerated discovery of disordered metamaterials with unique spectral features. </p> <p>Further, we explore the novel regimes of light localization at near-zero-index in such disordered media. The disordered near-zero-index medium reveals enhanced localization and near-field chirality. This work paves the way to engineer the electromagnetic nanophotonic environment to realize enhanced long-range dipole-dipole interactions.</p>