Nano and nanostructured materials offer unique physical and chemical properties that differ considerably from their bulk counterparts. For decades, due to their fascinating properties, they have been extensively explored and found to be beneficial in numerous applications. These materials are key components in many cutting-edge optic and photonic technologies, including photovoltaics, waveguides and sensors. In this dissertation, the uses of nano and nanostructured materials for optical applications are investigated in the context of optical limiting, three dimensional displays, and optical sensing. Nanomaterials with nonlinear optical responses are promising candidates for self-activating optical limiters. In the first part of this study, optical limiting properties of unexplored nanomaterials are investigated. A photoacoustic detection technique is developed as an alternative characterization method for studying optical nonlinearities. This was done with an indigenously developed setup for measuring the photoacoustic signals generated from samples excited with a pulse laser. A theoretical model for understanding the experimental observations is presented. In addition, the advantages of this newly developed technique over the existing methods are demonstrated. Blending optical sensitizers with photoconducting polymers and chromophores results in a polymer composite that is able to record a light grating. This composite can be used as recording media in 3D holographic display technology. Here, 2D nano materials, like graphenes, are used as optical sensitizers to improve the response time of a photorefractive polymer. The addition of graphenes to a PATPD/ECZ/7-DCST composite results in a three-fold enhancement in response time and therefore faster recording speed of the medium. The faster build-up time is attributed to better charge generation and mobility due to the presence of graphenes in the composite. Lastly, a facile nanofabrication technique is developed to produce metallic nanostructures with a tunable plasmonic response. The enhancement of the light-matter interactions due to these nanostructures in sensing an analyte is demonstrated.

The general goal of this dissertation is to provide a comprehensive description of the limitations of established theories on bound electronic nonlinearities in direct-gap semiconductors by performing various experiments on wide and narrow bandgap semiconductors along with developing theoretical models. Nondegenerate two-photon absorption (2PA) is studied in several semiconductors showing orders of magnitude enhancement over the degenerate counterpart. In addition, three-photon absorption (3PA) is studied in ZnSe and other semiconductors and a new theory using a Kane 4-band model is developed which fits new data well. Finally, the narrow gap semiconductor InSb is studied with regard to multiphoton absorption, free-carrier nonlinearities and decay mechanisms. The non-degenerate two-photon absorption was investigated in several direct-gap semiconductors with picosecond and femtosecond pulses. Large enhancements in 2PA were demonstrated when employing highly non-degenerate photon pairs and the results were shown to be consistent to a simple 2-parabolic band theory based on a "dressed" state approach. The nonlinear refractive index induced in such configurations was also calculated and possible implications of such extreme behavior are discussed. A large number of measurements of 3PA were taken at multiple wavelengths and in several semiconductors. The subsequent analysis has shown that simple 2-band model calculations (based on either perturbative or tunneling approaches) do not adequately describe the experimental trends. A more comprehensive model, based on Kane’s 4-band theory was developed and we calculate three-photon spectra for zincblende structures within the perturbative iv framework. We have confirmed the results of our calculations performing a series of Z-scans in semiconductors ZnSe and ZnS, yielding complete experimental three-photon spectra. A systematic approach based on using a large variety of pulse durations was needed to quantify the wealth of nonlinear optical processes in InSb, accessible in the mid-infrared range. Femtosecond pulses provided a lower limit to measurements of the instantaneous effects (absorptive and refractive), while picosecond pulses allowed further characterization of the freecarrier effects, including population dynamics in the high density regime (Auger effects). The model developed permitted us to verify the temperature dependence of free-carrier absorption recently predicted, and to successfully model optical limiting data with longer, nanosecond pulses.

Millimeter-wave imaging has gathered attention in recent years for its ability to penetrate clothing, thin layers of soils, and certain construction materials. However, image quality remains a challenge that needs to be addressed. One way of improving image quality is by increasing the dimensions of the collecting aperture. A sparse array can be used to synthesize a larger aperture with a limited set of relatively small detectors. In this research we design, build, and test a test-bed having an active source at 94 GHz and an array of coherent detectors, mounted on arms that extend radially on a rotary table. Using this test bed a circular area with a maximum diameter of 900 mm can be scanned. The signal is down-converted using heterodyne receivers with digital in-phase and quadrature detection. Signal correlation is performed using the digitized data, which is stored for post-processing, electronic focusing, and image reconstruction. Near-field imaging using interferometric reconstructions is achieved using electronic focusing. Imaging tests show the ability of the system to generate imagery of concealed and unconcealed objects at distances between 400 and 700 mm. A study of the effects of redundant and nonredundant configurations on image quality for 4 common detector configurations is presented. In this document we show that an active sparse-aperture imaging system using digital correlators is a viable way to generate millimeter-wave images.

Nonlinear absorption of Indium Antimonide (InSb) has been studied for many years, yet due to the complexity of absorption mechanisms and experimental difficulties in the infrared, this is still a subject of research. Although measurements have been made in the past, a consistent model that worked for both picosecond and nanosecond pulse widths had not been demonstrated. In this project, temperature dependent two-photon (2PA) and free carrier absorption (FCA) spectra of InSb are measured using femtosecond, picosecond, and nanosecond IR sources. The 2PA spectrum is measured at room temperature with femtosecond pulses, and the temperature dependence of 2PA and FCA is measured at 10.6µm using a nanosecond CO2 laser giving results consistent with the temperature dependent measurements at several wavelengths made with a tunable picosecond system. Measurements over this substantial range of pulse widths give results for FCA and 2PA consistent with a recent theoretical model for FCA. While the FCA cross section has been generally accepted in the past to be a constant for the temperatures and wavelengths used in this study, this model predicts that it varies significantly with temperature as well as wavelength. Additionally, the results for 2PA are consistent with the band gap scaling (Eg-3 ) predicted by a simple two parabolic band model. Using nanosecond pulses from a CO2 laser enables the recombination rates to be determined through nonlinear transmittance measurements. Three-photon absorption is also observed in InSb for photon energies below the 2PA band edge. Prior to this work, data on three-photon absorption (3PA) in semiconductors was scarce and most experiments were performed over narrow spectral ranges, v making comparison to the available theoretical models difficult. There was also disagreement between the theoretical results generated by different models, primarily in the spectral behavior. Therefore, we studied the band gap scaling and spectra of 3PA in several semiconductors by the Z-scan technique. The 3PA coefficient is found to vary as (Eg-7 ), as predicted by the scaling rules of simple two parabolic band models. The spectral behavior, which is considerably more complex than for 2PA, is found to agree well with a recently published theory based on a fourband model.

In this dissertation, the prospect of a quantum technology based on a photonic crystal chip hosting a quantum network made of quantum dot spins interacting via single photons is investigated. The mathematical procedure to deal with the Liouville-Von Neumann equation, which describes the time-evolution of the density matrix, was derived for an arbitrary system, giving general equations. Using this theoretical groundwork, a numerical model was then developed to study the spatiotemporal dynamics of entanglement between various qubits produced in a controlled way over the entire quantum network. As a result, an efficient quantum interface was engineered allowing for storage qubits and traveling qubits to exchange information coherently while demonstrating little error and loss in the process; such interface is indispensable for the realization of a functional quantum network. Furthermore, a carefully orchestrated dynamic control over the propagation of the flying qubit showed high-efficiency capability for on-chip single-photon transfer. Using the optimized dispersion properties obtained quantum mechanically as design parameters, a possible physical structure for the photonic crystal chip was constructed using the Plane Wave Expansion and FiniteDifference Time-Domain numerical techniques, exhibiting almost identical transfer efficiencies in terms of normalized energy densities of the classical electromagnetic field. These promising results bring us one step closer to the physical realization of an integrated quantum technology combining both semiconductor quantum dots and subwavelength photonic structures.

A large fleet (in the hundreds) of high quality telescopes are used for tracking and imaging of launch vehicles during ascent from Cape Canaveral Air Force Station and Kennedy Space Center. A maintenance tool has been development for use with these telescopes. The tool requires rankings of telescope condition in terms of the ability to generate useful imagery. It is thus a case of ranking telescope conditions on the basis of the perceptual image quality of their imagery. Perceptual image quality metrics that are well-correlated to observer opinions of image quality have been available for several decades. However, these are quite limited in their applications, not being designed to compare various optical systems. The perceptual correlation of the metrics implies that a constant image quality curve (such as the boundary between two qualitative categories labeled as excellent and good) would have a constant value of the metric. This is not the case if the optical system parameters (such as object distance or aperture diameter) are varied. No published data on such direct variation is available and this dissertation presents an investigation made into the perceptual metric responses as system parameters are varied. This investigation leads to some non-intuitive conclusions. The perceptual metrics are reviewed as well as more common metrics and their inability to perform in the necessary manner for the research of interest. Perceptual test methods are also reviewed, as is the human visual system. iv Image formation theory is presented in a non-traditional form, yielding the surprising result that perceptual image quality is invariant under changes in focal length if the final displayed image remains constant. Experimental results are presented of changes in perceived image quality as aperture diameter is varied. Results are analyzed and shortcomings in the process and metrics are discussed. Using the test results, predictions are made about the form of the metric response to object distance variations, and subsequent testing was conducted to validate the predictions. The utility of the results, limitations of applicability, and the immediate ability to further generalize the results is presented.

Tapered slot antennas (TSAs) have seen considerable application in the millimeter-wave portion of the spectrum. Desirable characteristics of TSAs include symmetric E- and H-plane antenna patterns, and broad non-resonant bandwidths. We investigate extension of TSA operation toward higher frequencies in the thermal infrared (IR), using a metal-oxide-metal diode as the detector. Several different infrared TSA design forms are fabricated using electronbeam lithography and specially developed thin-film processes. The angular antenna patterns of TSA-coupled diodes are measured at 10.6 micrometer wavelength in both E- and H-planes, and are compared to results of finite-element electromagnetic modeling using Ansoft HFSS. Parameter studies are carried out, correlating the geometric and material properties of several TSA design forms to numerical-model results and to measurements. A significant increase in antenna gain is noted for a dielectric-overcoat design. The traveling-wave behavior of the IR TSA structure is investigated using scattering near-field microscopy. The measured near-field data is compared to HFSS results. Suggestions for future research are included

This dissertation details the work has been done on a novel resonant cavity linear interferometric modulator and a direct phase detector with channel filtering capability using injection-locked semiconductor lasers for applications in RF photonics. First, examples of optical systems whose performance can be greatly enhanced by using a linear intensity modulator are presented and existing linearized modulator designs are reviewed. The novel linear interferometric optical intensity modulator based on an injection-locked laser as an arcsine phase modulator is introduced and followed by numerical simulations of the phase and amplitude response of an injection-locked semiconductor laser. The numerical model is then extended to study the effects of the injection ratio, nonlinear cavity response, depth of phase and amplitude modulation on the spur-free dynamic range of a semiconductor resonant cavity linear modulator. Experimental results of the performance of the linear modulator implemented with a multi-mode Fabry-Perot semiconductor laser as the resonant cavity are shown and compared with the theoretical model. The modulator performance using a vertical cavity surface emitting laser as the resonant cavity is investigated as well. Very low Vπ in the order of 1 mV, multi-gigahertz bandwidth (-10 dB bandwidth of 5 GHz) and a spur-free dynamic range of 120 dB.Hz2/3 were measured directly after the modulator. The performance of the modulator in an analog link is experimentally investigated and the results show no degradation of the modulator linearity after a 1 km of SMF. The focus of the work then shifts to applications of an injection-locked semiconductor laser as a direct phase detector and channel filter. This phase detection technique does not iv require a local oscillator. Experimental results showing the detection and channel filtering capability of an injection-locked semiconductor diode laser in a three channel system are shown. The detected electrical signal has a signal-to-noise ratio better than 60 dB/Hz. In chapter 4, the phase noise added by an injection-locked vertical cavity surface emitting laser is studied using a self-heterodyne technique. The results show the dependency of the added phase noise on the injection ratio and detuning frequency. The final chapter outlines the future works on the linear interferometric intensity modulator including integration of the modulator on a semiconductor chip and the design of the modulator for input pulsed light.

The visual content represented on information displays used in training environments prescribe display attributes as brightness, color, contrast, and motion blur, but considerations regarding cognitive processes corresponding to these visual features require further attention in order to optimize the display for training applications. This dissertation describes an empirical study with which information display features, specifically color and motion blur reduction, were investigated to assess their impact in a training scenario involving visual search and threat detection. Presented in this document is a review of the theory and literature describing display technology, its applications to training, and how eye-tracking systems can be used to objectively measure cognitive activity. The experiment required participants to complete a threat identification task, while altering the displays settings beforehand, to assess the utility of the display capabilities. The data obtained led to the conclusion that motion blur had a stronger impact on perceptual load than the addition of color. The increased perceptual load resulted in approximately 8- 10% longer fixation durations for all display conditions and a similar decrease in the number of saccades, but only when motion blur reduction was used. No differences were found in terms of threat location or threat identification accuracy, so it was concluded that the effects of perceptual load were independent of germane cognitive load.

Magnetic resonance imaging (MRI) has become one of the premier non-invasive diagnostic tools, with around 60 million MRI scans applied each year. However, there is a risk of thermal injury due to radiofrequency (RF) induction heating of the tissue and implanted metallic device for the patients with the implanted metallic devices. Especially, MRI of the patients with implanted elongated devices such as pacemakers and deep brain stimulation systems is considered contraindicated. Many efforts, such as determining preferred MRI parameters, modifying magnetic field distribution, designing new structure and exploring new materials, have been made to reduce the induction heating. Improving the MRI-compatibility of implanted metallic devices by modifying the properties of the existing materials would be valuable. To evaluate the temperature rise due to RF induction heating on a metallic implant during MRI procedure, an electromagnetic model and thermal model are studied. The models consider the shape of RF magnetic pulses, interaction of RF pulses with metal plate, thermal conduction inside the metal and the convection at the interface between the metal and the surroundings. Transient temperature variation and effects of heat transfer coefficient, reflectivity and MRI settings on the temperature change are studied. Laser diffusion is applied to some titanium sheets for a preliminary study. An electromagnetic and thermal model is developed to choose the proper diffusant. Pt is the diffusant in this study. An electromagnetic model is also developed based on the principles of inverse problems to calculate the electromagnetic properties of the metals from the measured magnetic transmittance. iv This model is used to determine the reflectivity, dielectric constant and conductivity of treated and as-received Ti sheets. The treated Ti sheets show higher conductivity than the as-received Ti sheets, resulting higher reflectivity. A beam shaping lens system which is designed based on vector diffraction theory is used in laser diffusion. Designing beam shaping lens based on the vector diffraction theory offers improved irradiance profile and new applications such as polarized beam shaping because the polarization nature of laser beams is considered. Laser Pt diffusion are applied on the titanium and tantalum substrates using different laser beam polarizations. The concentration of Pt and oxygen in those substrates are measured using Energy Dispersive X-Ray Spectroscopy (EDS). The magnetic transmittance and conductivity of those substrates are measured as well. The effects of laser beam polarizations on Pt diffusion and the magnetic transmittance and conductivity of those substrates are studied. Treated Ti sheets show lower magnetic transmittance due to the increased conductivity from diffused Pt atoms. On the other hand, treated Ta sheets show higher magnetic transmittance due to reduced conductivity from oxidation. Linearly polarized light can enhance the Pt diffusion because of the excitation of local vibration mode of atoms. Laser Pt diffusion and thermo-treatment were applied on the Ta and MP35N wires. The Pt concentration in laser platinized Ta and MP35N wires was determined using EDS. The ultimate tensile strength, fatigue lives and lead tip heating in real MRI environment of those wires were measured. The lead tip hating of the platinized Ta wires is 42 % less than the as-received Ta wire. The diffused Pt increases the conductivity of Ta wires, resulting in more reflection of magnetic field. In the case of the platinized MP35N wire, the reduction in lead tip heating was only 1 °C v due to low concentration of Pt. The weaker ultimate tensile strength and shorter fatigue lives of laser-treated Ta and MP35N wires may attribute to the oxidation and heating treatment.