Electromagnetics and Photonics Commons^™

Remote Sensing Of Hidden Objects, Mark G. Hoelscher, Michael A. Marciniak

AFIT Patents

An apparatus and method are provided for creating an indirect image of an object. The apparatus includes a light source and an imaging system. Light emitted from the light source is reflected by a first non-specular surface toward the object. Light reflected by the object is further reflected by a second non-specular surface toward the imaging system. The imaging system is configured to create the indirect image from the reflected light.

Investigation Of Electromagnetic Velocities And Negative Refraction In A Chiral Metamaterial With Second-Order Material Dispersion Using Spectral Analyses And Dispersive Models, Monish Ranjan Chatterjee, Tarig A. Algadey

Electrical and Computer Engineering Faculty Publications

In recent years, considerable research has been carried out relative to the electromagnetic (EM) propagation and refraction characteristics in metamaterials with emphasis on the origins of negative refractive index.

Negative refractive index may be introduced in metamaterials via different methods; one such is the condition whereby the Poynting vector of the EM wave is in opposition to the group velocity in the material. Alternatively, negative refractive index also occurs when the group and phase velocities in the medium are in opposition. The latter phenomenon has been extensively investigated in the literature, including recent work involving chiral metamaterials with material dispersion …

Optimization-Free Optical Focal Field Engineering Through Reversing The Radiation Pattern From A Uniform Line Source, Yanzhong Yu, Qiwen Zhan

Electro-Optics and Photonics Faculty Publications

A simple and flexible method is presented for the generation of optical focal field with prescribed characteristics. By reversing the field pattern radiated from a uniform line source, for which the electric current is constant along its extent, situated at the focus of a 4Pi focusing system formed by two confocal high-NA objective lenses, the required illumination distribution at the pupil plane for creating optical focal field with desired properties can be obtained. Numerical example shows that an arbitrary length optical needle with extremely high longitudinal polarization purity and consistent transverse size of ~0.36λ over the entire depth of focus …

Analysis And Characterization Of Finite-Size Curved Frequency Selective Surfaces, Francesco Mattiello, Giovanni Leone, Giuseppe Ruvio

Articles

Frequency Selective Surfaces (FSSs) are spatial filters that are largely employed in radomes for radars and antennas where high performance is necessary. FSS can be categorised in terms of their frequency behaviour. Band-pass FSS structures are able to let the electromagnetic wave pass in certain frequency ranges and shield others, which are especially suitable for out-of-band stealth of radomes. The properties of frequency selectiveness of these screens are used at microwave and infrared wavelengths. By tuning the electrical size and geometry of the unit-cell (patch or aperture) different frequency behaviours of the structure are generated. Although their analysis and simulation …

Low Clutter Method For Bistatic Rcs Measurements, Peter J. Collins

AFIT Patents

A bistatic radar measurement system is provided having a radar source configured to produce a radio frequency signal. A transmitting antenna is configured to transmit the radio frequency signal toward a target. A receiving antenna is configured to receive a reflected radio frequency signal from the target. A support system is configured to support the receiving antenna. The support system includes a plurality of low scattering dielectric strings configured to orient the receiving antenna.

Integration Of Antenna Array With Multicrystalline Silicon Solar Cell, Oisin O'Conchubhair, Patrick Mcevoy, Max Ammann

Articles

The integration of a low-profile antenna array with a multicrystalline silicon solar cell capable of powering a low-power wireless sensor at 2.45 GHz is reported. Lattice bus bars on the cell are exploited to minimize antenna shadows from low-profile antennas and transmission lines for a higher output power. The dual inverted-F array improves gain, and beam switching enables the array to sweep a wider coverage angle with larger beamwidths compared to other solar integrated antennas.

Tunable Narrow Band Difference Frequency Thz Wave Generation In Dast Via Dual Seed Ppln Opg, Brian Dolasinski, Peter E. Powers, Joseph W. Haus, Adam Cooney

Electro-Optics and Photonics Faculty Publications

We report a widely tunable narrowband terahertz (THz) source via difference frequency generation (DFG). A narrowband THz source uses the output of dual seeded periodically poled lithium niobate (PPLN) optical parametric generators (OPG) combined in the nonlinear crystal 4-dimthylamino-N-methyl-4-stilbazolium-tosylate (DAST). We demonstrate a seamlessly tunable THZ output that tunes from 1.5 THz to 27 THz with a minimum bandwidth of 3.1 GHz. The effects of dispersive phase matching, two-photon absorption, and polarization were examined and compared to a power emission model that consisted of the current accepted parameters of DAST.

Secure Transmission Of Static And Dynamic Images Via Chaotic Encryption In Acousto-Optic Hybrid Feedback With Profiled Light Beams, Monish Ranjan Chatterjee, Fares S. Almehmadi

Electrical and Computer Engineering Faculty Publications

Secure information encryption via acousto-optic (AO) chaos with profiled optical beams indicates substantially better performance in terms of system robustness. This paper examines encryption of static and time-varying (video) images onto AO chaotic carriers using Gaussian-profile beams with diffracted data numerically generated using transfer functions. The use of profiled beams leads to considerable improvement in the encrypted signal.

While static image encryption exhibits parameter tolerances within about ±10% for uniform optical beams, profiled beams reduce the tolerance to less than 1%, thereby vastly improving both the overall security of the transmitted information as well as the quality of the image …

Role Of Antenna Modes And Field Enhancement In Second Harmonic Generation From Dipole Nanoantennas, Domenico De Ceglia, Maria Antonietta Vincenti, Costantino De Angelis, Andrea Locatelli, Joseph W. Haus, Michael Scalora

Electro-Optics and Photonics Faculty Publications

We study optical second harmonic generation from metallic dipole antennas with narrow gaps. Enhancement of the fundamental-frequency field in the gap region plays a marginal role on conversion efficiency. In the symmetric configuration, i.e., with the gap located at the center of the antenna axis, reducing gap size induces a significant red-shift of the maximum conversion efficiency peak. Either enhancement or inhibition of second-harmonic emission may be observed as gap size is decreased, depending on the antenna mode excited at the harmonic frequency. The second-harmonic signal is extremely sensitive to the asymmetry introduced by gap’s displacements with respect to the …

Electron-Beam Patterning Of Teflon Af For Surface Plasmon Resonance Sensing, Mansoor A. Sultan

Theses and Dissertations--Electrical and Computer Engineering

Variable pressure electron beam etching and lithography for Teflon AF has been demonstrated. The relation between dose and etching depth is tested under high vacuum and water vapor. High resolution structures as small as 75 nm half-pitch have been resolved. Several simulation tools were tested for surface plasmon excitation. Grating based dual mode surface plasmon excitation has been shown numerically and experimentally.

True Linearized Intensity Modulation For Photonic Analog To Digital Conversion Using An Injection-Locked Mode-Locked Laser, Edris Sarailou

Electronic Theses and Dissertations

A true linearized interferometric intensity modulator for pulsed light has been proposed and experimentally presented in this thesis. This has been achieved by introducing a mode-locked laser into one of the arms of a Mach-Zehnder interferometer and injection-locking it to the input light (which is pulsed and periodic). By modulating the injection-locked laser, and combining its output light with the light from the other arm of interferometer in quadrature, one can achieve true linearized intensity modulator. This linearity comes from the arcsine phase response of the injection-locked mode-locked laser (as suggested by steady-state solution of Adler's equation) when it is …

Emi Analysis Of Dvi Link Connectors, Abhishek Patnaik

Masters Theses

"EMI problems are not uncommon in high speed communication systems. As the system clock frequencies increases, so does the challenges in controlling the EMI in such systems. A connector is a very important part of a high speed communication system. Electromagnetic interference (EMI) is found to be tightly correlated to mode conversion: from differential-mode (DM) signals to common-mode (CM) currents and further to antenna-mode (AM) currents on the outside of cables or enclosures. Moreover, in such high speed systems, coupling to an adjacent cable-connector system is not uncommon. It is essential to understand and quantify this coupling path in order …

Modeling And Preliminary Characterization Of Passive, Wireless Temperature Sensors For Harsh Environment Applications Based On Periodic Structures, Diego Ivan Delfin Manriquez

Open Access Theses & Dissertations

Wireless temperature sensing has attained significant attention in recent years due to the increasing need to develop reliable and affordable sensing solutions for energy conversion systems and other harsh environment applications. The development of next generation sensors for energy production processing parameters, such as temperature and pressure, can result in better performance of the system. Particularly, continuous temperature monitoring in energy conversion systems can result in enhancements such as better system integrity, less pollution and higher thermal efficiencies. However, the conditions experienced in these system components hinder the performance of current solutions due to the presence of semi-conductor materials and …

3d Integration With Coaxial Through Silicon Vias, Stephen Adamshick

Legacy Theses & Dissertations (2009 - 2024)

3D integration using through-silicon-vias (TSVs) is gaining considerable attention due to its superior packaging efficiency resulting in higher functionality, improved performance and a reduction in power consumption. In order to implement 3D chip designs with TSV technology, robust TSV electrical models are required. Specifically, due to the increase of signal speeds into the gigahertz (GHz) spectrum, a high frequency electrical characterization best describes TSV behavior.

Experimental Validation Of Metasurface Cloak For Dielectric Cylinder At Mircowave Frequencies, Corey Isaac Garner

Electronic Theses and Dissertations

No abstract provided.

Graphene Based Metamaterials For Terahertz Cloaking And Subwavelength Imaging, Seyedali Forouzmand

Electronic Theses and Dissertations

Graphene is a two-dimensional carbon crystal that became one of the most controversial topics of research in the last few years. The intense interest in graphene stems from recent demonstrations of their potentially revolutionary electromagnetic applications – including negative refraction, subdiffraction imaging, and even invisibility – which have suggested a wide range of new devices for communications, sensing, and biomedicine. In addition, it has been shown that graphene is amenable to unique patterning schemes such as cutting, bending, folding, and fusion that are predicted to lead to interesting properties. A recent proposed application of graphene is in engineering the scattering …

Nanoscale Control Of Gap-Plasmon Enhanced Optical Processes, Chatdanai Lumdee

Electronic Theses and Dissertations

Surface plasmon resonances of metal nanostructures have been studied intensely in recent years. The strong plasmon-mediated electric field enhancement and field confinement well beyond the diffraction limit has been demonstrated to improve the performance of optical devices including ultrasensitive sensors, light emitters, and optical absorbers. A plasmon resonance mode of particular recent interest is the gap plasmon resonance that occurs on closely spaced metallic structures. In contrast to plasmon resonances supported by isolated metal nanostructures, coupled nanostructures provide additional spectral and spatial control over the plasmon resonance response. For example, the resonance frequencies of metal nanoparticle dimers depend strongly on …

Optical Propagation Of Self-Sustaining Wavefronts And Nonlinear Dynamics In Parabolic Multimode Fibers, Matthew Mills

Electronic Theses and Dissertations

The aim of this thesis is to introduce my work which has generally been focused on optical wavefronts that have the unusual property of resisting commonplace phenomena such as diffraction and dispersion. Interestingly, these special beams are found both in linear and nonlinear situations. For example, in the linear regime, localized spatio-temporal waves which resemble the spherical harmonic symmetries of the hydrogen quantum orbitals can simultaneously negotiate both diffractive and dispersive effects. In the nonlinear regime, dressed optical filaments can be arranged to propagate multi-photon produced plasma channels orders of magnitude longer than expected. The first portion of this dissertation …

Towards High-Flux Isolated Attosecond Pulses With A 200 Tw Cpa, Eric Cunningham

Electronic Theses and Dissertations

Attosecond pulses have been developed as a means for investigating phenomena that proceed on the order of the atomic unit of time (24 as). Unfortunately, these extreme ultraviolet (XUV) pulses by themselves contain too few photons to initiate nonlinear dynamics or dress states in an attosecond pump--attosecond probe scheme. As a result, most attosecond experiments thus far have featured complementary near infrared (NIR) femtosecond lasers for instigating electron dynamics. In order to access the benefits of all-attosecond measurements and open attosecond physics to new fields of exploration, the photon flux of these pulses must be increased. One way to boost …

Low Absorption Liquid Crystal Materials For Midwave Infrared, Amy Creekmore

Electronic Theses and Dissertations

Liquid crystal is an amazing class of soft matters with applications spanning from visible, infrared, millimeter wave, to terahertz. In addition to direct-view displays and projection displays, liquid crystal is also widely used in adaptive optics, tunable-focus lens, and laser beam steering. Although the visible region has well developed materials and mixtures for the vast variety of applications, the midwave infrared (MWIR) region of the electromagnetic spectrum invites much development as only a few materials have been developed with these applications in mind. Unlike visible region, the major challenge for mid-wave infrared liquid crystal is inherently large absorption loss. To …