Exploring bistatic scattering modeling for land surface applications using radio spectrum recycling in the Signal of Opportunity Coherent Bistatic Simulator

The potential for high spatio-temporal resolution microwave measurements has urged the adoption of the signals of opportunity (SoOp) passive radar technique for use in remote sensing. Recent trends in particular target highly complex remote sensing problems such as root-zone soil moisture and snow water equivalent. This dissertation explores the continued open-sourcing of the SoOp coherent bistatic scattering model (SCoBi) and its use in soil moisture sensing applications. Starting from ground-based applications, the feasibility of root-zone soil moisture remote sensing is assessed using available SoOp resources below L-band. A modularized, spaceborne model is then developed to simulate land-surface scattering and delay-Doppler maps over the available spectrum of SoOp resources. The simulation tools are intended to provide insights for future spaceborne modeling pursuits

Gratings: Theory and Numeric Applications, Second Revisited Edition

International audienceThe second Edition of the Book contains 13 chapters, written by an international team of specialist in electromagnetic theory, numerical methods for modelling of light diffraction by periodic structures having one-, two-, or three-dimensional periodicity, and aiming numerous applications in many classical domains like optical engineering, spectroscopy, and optical telecommunications, together with newly born fields such as photonics, plasmonics, photovoltaics, metamaterials studies, cloaking, negative refraction, and super-lensing. Each chapter presents in detail a specific theoretical method aiming to a direct numerical application by university and industrial researchers and engineers.In comparison with the First Edition, we have added two more chapters (ch.12 and ch.13), and revised four other chapters (ch.6, ch.7, ch.10, and ch.11

Full Wave 2D Modeling of Scattering and Inverse Scattering for Layered Rough Surfaces with Buried Objects.

Efficient and accurate modeling of electromagnetic scattering from layered rough surfaces with buried objects finds applications ranging from detection of landmines to remote sensing of subsurface soil moisture. In this dissertation, the formulation of a hybrid numerical/analytical solution to electromagnetic scattering from layered rough surfaces is first developed. The solution to scattering from each rough interface is sought independently based on the extended boundary condition method (EBCM), where the scattered fields of each rough interface are expressed as a summation of plane waves and then cast into reflection/transmission matrices. To account for interactions between multiple rough boundaries, the scattering matrix method (SMM) is applied to recursively cascade reflection and transmission matrices of each rough interface and obtain the composite reflection matrix from the overall scattering medium. The validation of this method against the Method of Moments (MoM) and Small Perturbation Method (SPM) will be addressed and the numerical results which investigate the potential of low frequency radar systems in estimating deep soil moisture will be presented. Computational efficiency of the proposed method is also addressed. In order to demonstrate the capability of this method in modeling coherent multiple scattering phenomena, the proposed method has been employed to analyze backscattering enhancement and satellite peaks due to surface plasmon waves from layered rough surfaces. Numerical results which show the appearance of enhanced backscattered peaks and satellite peaks are presented. Following the development of the EBCM/SMM technique, a technique which incorporates a buried object in layered rough surfaces is proposed by employing the T-matrix method and the cylindrical-to-spatial harmonics transformation. Validation and numerical results are provided. Finally, a multi-frequency polarimetric inversion algorithm for the retrieval of subsurface soil properties using VHF/UHF band radar measurements is developed. The top soil dielectric constant is first determined using an L-band inversion algorithm. For the retrieval of subsurface properties, a time-domain inversion technique is employed together with a parameter optimization for the pulse shape of time delay echoes from VHF/UHF band radar observations. Some numerical studies to investigate the accuracy of the proposed inversion technique in presence of errors are shown.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/58459/1/kuoch_1.pd

Sensitivity analysis of 2D photonic band gaps of any rod shape and conductivity using a very fast conical integral equation method

The conical boundary integral equation method has been proposed to calculate the sensitive optical response of 2D photonic band gaps (PBGs), including dielectric, absorbing, and highconductive rods of various shapes working in any wavelength range. It is possible to determine the diffracted field by computing the scattering matrices separately for any grating boundary profile. The computation of the matrices is based on the solution of a 2×2 system of singular integral equations at each interface between two different materials. The advantage of our integral formulation is that the discretization of the integral equations system and the factorization of the discrete matrices, which takes the major computing time, are carried out only once for a boundary. It turned out that a small number of collocation points per boundary combined with a high convergence rate can provide adequate description of the dependence on diffracted energy of very different PBGs illuminated at arbitrary incident and polarization angles. The numerical results presented describe the significant impact of rod shape on diffraction in PBGs supporting polariton-plasmon excitation, particularly in the vicinity of resonances and at high filling ratios. The diffracted energy response calculated vs. array cell geometry parameters was found to vary from a few percent up to a few hundred percent. The influence of other types of anomalies (i.e. waveguide anomalies, cavity modes, Fabry-Perot and Bragg resonances, Rayleigh orders, etc), conductivity, and polarization states on the optical response has been demonstrated

Sensitivity analysis of 2D photonic band gaps of any rod shape and conductivity using a very fast conical integral equation method

The conical boundary integral equation method has been proposedto calculate the sensitive optical response of 2D photonic band gaps (PBGs),including dielectric, absorbing, and high-conductive rods of various shapes working in any wavelength range. It is possible to determine the diffracted field by computing the scattering matrices separately for any gratingboundary profile. The computation of the matrices is based on the solution of a 2 x 2system of singular integral equations at each interface between two different materials. The advantage of our integral formulation is that the discretization of the integral equations system and the factorization of the discrete matrices, which takes the major computing time, are carried out only oncefor a boundary. It turned out that a small number of collocation points per boundary combined with a high convergence rate can provide adequate description of the dependence on diffracted energy of very different PBGs illuminated at arbitrary incident and polarization angles. Thenumerical results presented describe the significant impact of rod shape on diffraction in PBGs supporting polariton-plasmon excitation, particularly in the vicinity of resonances and at high fillingratios. The diffracted energy response calculated vs. array cell geometry parameters was found to vary from a few percent up to a few hundred percent. The influence of other types of anomalies (i.e. waveguide anomalies, cavity modes, Fabry-Perot and Bragg resonances, Rayleigh orders, etc), conductivity, and polarization states on the optical response has been demonstrated

A Novel Experimental Platform for the Study of Near-Field Radiative Transport and Measurements from Thin Dielectric Coatings.

Near-field radiative heat transfer (NFRHT) is an active area of research with implications for heat transfer and thermal management technologies in the future. Previous experiments observed that when the gap-size between a hot surface, the emitter, and a cold one, the receiver, reduces to micrometer dimensions significant enhancements in radiative heat flow between the two surfaces, above the value predicted by Stefan-Boltzman law, are observed. Subsequent theoretical studies supported these results and predicted orders-of-magnitude enhancement in radiative heat flow if the gap-size is further decreased to nanoscale. A range of other interesting phenomena are also predicted for this near-field regime. One of the most intriguing of these theoretical predictions is that pertaining to NFRHT enhancements calculated for nanoscale-thin dielectric coatings. In particular, when the gap-size between the emitter and receiver becomes comparable to film thickness, the enhancements in radiative heat flow are predicted to be as large as those for bulk materials, which can result in heat transfer coefficients that are ~20 times that of far-field values for a gap size of ~20 nm. No experiment has proved the validity of theoretical predictions pertaining to NFRHT enhancement from nanoscale-thin dielectric films. Here, a new experimental platform to perform NFRHT experiments is presented. The platform consists of two major components; a microfabricated resistive picowatt-resolution calorimeter and a six degree-of-freedom nanopositioner that can parallelize two planes with ~6 µrad of resolution. While this platform is designed to eventually perform NFRHT measurements between parallel plates, here it is used to measure enhancements of radiative heat flow between a spherical emitter and thin dielectric receiver with varying thickness. Consequently, for the first time, a dramatic increase in near-field radiative heat transfer from thin dielectric films is observed, which is comparable to that obtained between bulk materials, even for very thin dielectric films (50–100 nm) when the spatial separation between the hot and cold surfaces is comparable to the film thickness. These results are attributed to the spectral characteristics and mode shapes of surface phonon polaritons, which dominate near-field radiative heat transport in polar dielectric thin films.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113485/1/yasharg_1.pd

Probing Radiative Thermal Transport at the Nanoscale.

Thermal radiative emission from a hot to a cold surface plays an important role in many applications, including energy conversion, thermal management, lithography, data storage, and thermal microscopy. While thermal radiation at length scales larger than the dominant wavelength is well understood in terms of Planck’s law and the Stefan-Boltzmann law, near-field thermal radiation is not. With constantly advancing micro- and nanofabrication techniques and ever smaller devices a substantial need for a better and more reliable understanding of the fundamental physics governing nanoscale radiative heat transfer has arisen. Unfortunately, and in stark contrast to the abundance of theoretical and numerical work, there have only been limited experimental efforts and achievements. The central challenge in the field is to accurately and unambiguously characterize radiative heat transport between well-defined surfaces across nanometer distances. The key scientific and technological questions that I have experimentally addressed during my doctoral study include: How does radiative heat transfer between an emitter and a receiver depend on their spatial separation (gap size), and does the radiative heat flux increase by over five orders of magnitude as the gap size is reduced to a few nanometers, as theoretically predicted? Can polar dielectric and metallic thin films support substantial near-field heat flow enhancement? For single-digit nanometer gaps, is the widely used theoretical framework of fluctuational electrodynamics (still) applicable? To address these challenging questions in gap sizes as small as tens of nanometers, we developed a nanopositioning platform to precisely control the gap between a microfabricated emitter device and a suspended receiver/calorimeter device which enables simultaneous measurement of the radiative heat flow across the gap. Further, we employed an atomic force microscope (AFM) in conjunction with stiff custom-fabricated scanning thermal microscopy (SThM) probes to explore the extreme near-field characterized by gaps of a few nanometers. In both approaches, high vacuum, vibration isolation and temperature control are implemented for accurate thermal measurements and for maintaining a stable gap. Finally, we performed state-of-the-art fluctuational electrodynamics-based calculations and analysis to compare theoretical predictions with experimental observations.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/116634/1/baisong_1.pd

Classical and fluctuation-induced electromagnetic interactions in micronscale systems: designer bonding, antibonding, and Casimir forces

Whether intentionally introduced to exert control over particles and macroscopic objects, such as for trapping or cooling, or whether arising from the quantum and thermal fluctuations of charges in otherwise neutral bodies, leading to unwanted stiction between nearby mechanical parts, electromagnetic interactions play a fundamental role in many naturally occurring processes and technologies. In this review, we survey recent progress in the understanding and experimental observation of optomechanical and quantum-fluctuation forces. Although both of these effects arise from exchange of electromagnetic momentum, their dramatically different origins, involving either real or virtual photons, lead to different physical manifestations and design principles. Specifically, we describe recent predictions and measurements of attractive and repulsive optomechanical forces, based on the bonding and antibonding interactions of evanescent waves, as well as predictions of modified and even repulsive Casimir forces between nanostructured bodies. Finally, we discuss the potential impact and interplay of these forces in emerging experimental regimes of micromechanical devices.Comment: Review to appear on the topical issue "Quantum and Hybrid Mechanical Systems" in Annalen der Physi