Electromagnetics and Photonics Commons^™

Evaluation Of The Photo-Induced Structural Mechanisms In Chalcogenide, Cedric Lopez

Electronic Theses and Dissertations

Chalcogenide glasses and their use in a wide range of optical, electronic and memory applications, has created a need for a more thorough understanding of material property variation as a function of composition and in geometries representative of actual devices. This study evaluates compositional dependencies and photo-induced structural mechanisms in As-S-Se chalcogenide glasses. An effective fabrication method for the reproducible processing of bulk chalcogenide materials has been demonstrated and an array of tools developed, for the systematic characterization of the resulting material's physical and optical properties. The influence of compositional variation on the physical properties of 13 glasses within the …

Photonic Band Gap Analysis Using Finite-Difference Frequency-Domain Method, Shangping Guo, Feng Wu, Sacharia Albin

Electrical & Computer Engineering Faculty Publications

A finite-difference frequency-domain (FDFD) method is applied for photonic band gap calculations. The Maxwell’s equations under generalized coordinates are solved for both orthogonal and non-orthogonal lattice geometries. Complete and accurate band gap information is obtained by using this FDFD approach. Numerical results for 2D TE/TM modes in square and triangular lattices are in excellent agreements with results from plane wave method (PWM). The accuracy, convergence and computation time of this method are also discussed.

Monolithic Integration Of Dual Optical Elements On High Power Semicond, Laurent Vaissie

Electronic Theses and Dissertations

This dissertation investigates the monolithic integration of dual optical elements on high power semiconductor lasers for emission around 980nm wavelength. In the proposed configuration, light is coupled out of the AlGaAs/GaAs waveguide by a low reflectivity grating coupler towards the substrate where a second monolithic optical element is integrated to improve the device performance or functionality. A fabrication process based on electron beam lithography and plasma etching was developed to control the grating coupler duty cycle and shape. The near-field intensity profile outcoupled by the grating is modeled using a combination of finite-difference time domain (FDTD) analysis of the nonuniform …

Thermal Management, Beam Control,And Packaging Designs For High Power, Te-Yuan Chung

Electronic Theses and Dissertations

Several novel techniques for controlling, managing and utilizing high power diode lasers are described. Low pressure water spray cooling for a high heat flux system is developed and proven to be an ideal cooling method for high power diode laser arrays. In order to enable better thermal and optical performance of diode laser arrays, a new and simple optical element, the beam control prism, is invented. It provides the ability to accomplish beam shaping and beam tilting at the same time. Several low thermal resistance diode packaging designs using beam control prisms are proposed, studied and produced. Two pump cavity …

Multiple Scattering Of Light In Inhomogeneous Media And Applications, Claudia Mujat

Electronic Theses and Dissertations

Light scattering-based techniques are being developed for non-invasive diagnostics of inhomogeneous media in various fields, such as medicine, biology, and material characterization. However, as most media of interest are highly scattering and have a complex structure, it is difficult to obtain a full analytical solution of the scattering problem without introducing approximations and assumptions about the properties of the system under consideration. Moreover, most of the previous studies deal with idealized scattering situations, rarely encountered in practice. This dissertation provides new analytical, numerical, and experimental solutions to describe subtle effects introduced by the properties of the light sources, and by …

Polarimetric Characterization Of Random Electromagnetic Beams And Applications, Mircea Mujat

Electronic Theses and Dissertations

Polarimetry is one of the principal means of investigating the interaction of light with matter. Theoretical models and experimental techniques are presented in this dissertation for polarimetric characterization of random electromagnetic beams and of signatures of random media in different scattering regimes and configurations. The degree of polarization rather than the full description of the state of polarization is of interest in multiple scattering and free space propagation where the statistical nature and not the deterministic component of light bears the relevant information. A new interferometric technique for determining the degree of polarization by measuring the intensity fluctuations in a …

Quadratic Spatial Soliton Interactions, Ladislav Jankovic

Electronic Theses and Dissertations

Quadratic spatial soliton interactions were investigated in this Dissertation. The first part deals with characterizing the principal features of multi-soliton generation and soliton self-reflection. The second deals with two beam processes leading to soliton interactions and collisions. These subjects were investigated both theoretically and experimentally. The experiments were performed by using potassium niobate (KNBO3) and periodically poled potassium titanyl phosphate (KTP) crystals. These particular crystals were desirable for these experiments because of their large nonlinear coefficients and, more importantly, because the experiments could be performed under non-critical-phase-matching (NCPM) conditions. The single soliton generation measurements, performed on KNBO3 by launching the …

Stable Spatial Solitons In Semiconductor Optical Amplifiers, Erdem Ultanir

Electronic Theses and Dissertations

A spatial soliton is a shape invariant self guided beam of light or a self induced waveguide. Spatial solitons appear as a result of the balance of diffraction and nonlinear focusing in a system. They have been observed in many different conservative media in the last couple of years. Solitons are ubiquitous, because of the probability of using their interactions in optical data processing, communications etc. Up to now due to the power required to generate the solitons, and the response times of the soliton supporting media, these special waves of nature could not penetrate the applications arena. Semiconductors, with …

Dispersion-Managed Breathing-Mode Semiconductor Mode-Locked Ring Laser, Bojan Resan

Electronic Theses and Dissertations

A novel dispersion-managed breathing-mode semiconductor mode-locked ring laser is developed. The "breathing-mode" designation derives from the fact that intracavity pulses are alternately stretched and compressed as they circulate around the ring resonator. The pulses are stretched before entering the semiconductor gain medium to minimize the detrimental strong integrating self-phase modulation and to enable efficient pulse amplification. Subsequently compressed pulses facilitate bleaching the semiconductor saturable absorber. The intracavity pulse compression ratio is higher than 50. Down chirping when compared to up chirping allows broader mode-locked spectra and shorter pulse generation owing to temporal and spectral semiconductor gain dynamics. Pulses as short …

Towards Direct Writing Of 3-D Photonic Circuits Using Ultrafast Lasers, Arnaud Zoubir

Electronic Theses and Dissertations

The advent of ultrafast lasers has enabled micromachining schemes that cannot be achieved by other current techniques. Laser direct writing has emerged as one of the possible routes for fabrication of optical waveguides in transparent materials. In this thesis, the advantages and limitations of this technique are explored. Two extended-cavity ultrafast lasers were built and characterized as the laser sources for this study, with improved performance over existing systems. Waveguides are fabricated in oxide glass, chalcogenide glass, and polymers, these being the three major classes of materials for the telecommunication industry. Standard waveguide metrology is performed on the fabricated waveguides, …

Loss And Dispersion Analysis Of Microstructured Fibers By Finite-Difference Method, Shangping Guo, Feng Wu, Sacharia Albin, Hsiang Tai, Robert S. Rogowski

Electrical & Computer Engineering Faculty Publications

The dispersion and loss in microstructured fibers are studied using a full-vectorial compact-2D finite-difference method in frequency-domain. This method solves a standard eigen-value problem from the Maxwell’s equations directly and obtains complex propagation constants of the modes using anisotropic perfectly matched layers. A dielectric constant averaging technique using Ampere’s law across the curved media interface is presented. Both the real and the imaginary parts of the complex propagation constant can be obtained with a high accuracy and fast convergence. Material loss, dispersion and spurious modes are also discussed.

Examination Of Focused Beam Propagation Through A Finite Non-Reciprocal Planar Chiral Slab Using Complex Fresnel Coefficients And Dual Transforms, Monish Ranjan Chatterjee, Sumit Nema, Partha P. Banerjee

Electrical and Computer Engineering Faculty Publications

Recently, uniform plane wave propagation across a nonchiral-chiral interface was examined via the development of appropriate Fresnel coefficients. In this extension, propagation of focused uniform and profiled beams through a finite, planar nonreciprocal chiral slab is investigated using complex Fresnel coefficients via angular plane wave decomposition and dual transforms.

Revisiting The Fresnel Coefficients For Uniform Plane Wave Propagation Across A Nonchiral, Reciprocal And Chiral, Nonreciprocal Interface, Monish Ranjan Chatterjee, Sumit Nema

Electrical and Computer Engineering Faculty Publications

The problem of EM wave propagation in non-reciprocal chiral media has been studied by several investigators. In a recent approach, a dual-transform technique has been developed to study the problem of such propagation under paraxial and slow-envelope variation conditions.

In this paper, we first outline some of the results obtained using the dual transform technique for arbitrary boundary conditions within the left boundary of a semi-infinite, non-reciprocal chiral medium for a uniform plane wave, and a fundamental Gaussian-profiled beam. Next, we explore the problem of a uniform EM wave incident at an oblique angle at an interface between a reciprocal, …

Wide Angle Achromatic Prism Beam Steering For Infrared Countermeasures Applications, Bradley D. Duncan, Philip J. Bos, Vassili Sergan

Electro-Optics and Photonics Faculty Publications

The design and analysis of achromatic doublet prisms for use in laser beam steering is presented. The geometric relationships describing the maximum steering angle are given, as are discussions of first- and second-order dispersion reduction. Infrared (IR) material alternatives and optimum IR material characteristics for wide-angle achromatic prism beam steering are also investigated. Sixteen materials in 120 different combinations have been examined to date. For midwave IR applications it is shown that the minimum dispersion currently achievable across the full 2 to 5 μm spectrum is 1.7816 mrad at an average maximum steering angle of 45 deg. This is accomplished …

Index-Matched Boundary Techniques For The Elimination Of Acoustical Resonances, Jack H. Parker, Bradley D. Duncan

Electro-Optics and Photonics Faculty Publications

We extend the principle of optical index of refraction to apply the concept of acoustical index for transverse acoustical wave propagation in strings. The relationship between acoustical index and mass density of the acoustic material is developed. With this theoretical link established, classic index-matching techniques are explored at acoustical boundaries. Proper selection of boundary interface segments leads to the elimination of resonant vibrationalmodes that occur in rigidly supported strings, while maintaining the nonresonant vibration response.

Digital Image Processing, Russell C. Hardie, Majeed M. Hayat

Electrical and Computer Engineering Faculty Publications

In recent years, digital images and digital image processing have become part of everyday life. This growth has been primarily fueled by advances in digital computers and the advent and growth of the Internet. Furthermore, commercially available digital cameras, scanners, and other equipment for acquiring, storing, and displaying digital imagery have become very inexpensive and increasingly powerful. An excellent treatment of digital images and digital image processing can be found in Ref. [1]. A digital image is simply a two-dimensional array of finite-precision numerical values called picture elements (or pixels). Thus a digital image is a spatially discrete (or discrete-space) …

Chaotic Free-Space Laser Communication Over Turbulent Channel, N. F. Rulkov, Mikhail Vorontsov, L. Illing

Electro-Optics and Photonics Faculty Publications

The dynamics of errors caused by atmospheric turbulence in a self-synchronizing chaos-based communication system that stably transmits information over a ∼5  km free-space laser link is studied experimentally. Binary information is transmitted using a chaotic sequence of short-term pulses as a carrier. The information signal slightly shifts the chaotic time position of each pulse depending on the information bit. We report the results of an experimental analysis of the atmospheric turbulence in the channel and the impact of turbulence on the bit-error-rate performance of this chaos-based communication system.

Implementation Of A Si/Sic Hybrid Optically Controlled High-Power Switching Device, Prashant Bhadri, Kuntao Ye, Elena A. Guliants, Fred R. Beyette Jr.

Electrical and Computer Engineering Faculty Publications

The ever-increasing performance and economy of operation requirements placed on commercial and military transport aircraft are resulting in very complex systems. As a result, the use of fiber optic component technology has lead to high data throughput, immunity to EMI, reduced certification and maintenance costs and reduced weight features. In particular, in avionic systems, data integrity and high data rates are necessary for stable flight control. Fly-by-Light systems that use optical signals to actuate the flight control surfaces of an aircraft have been suggested as a solution to the EMI problem in avionic systems. Current fly-by-light systems are limited by …

Translation Of 'Balika Badhu: A Selected Anthology Of Bengali Short Stories', Monish Ranjan Chatterjee

Electrical and Computer Engineering Faculty Publications

This project, which began with the desire to render into English a rather long tale by Bimal Kar about five years ago, eventually grew into a considerably more extended compilation of Bengali short stories by 10 of the most well-known practitioners of that art since the heyday of Rabindranath Tagore. The collection is limited in many ways, not the least of which being that no woman writer has been included, and that it contains only a baker's dozen stories (if we count Bonophool's micro-stories collectively as one ) — a number pitifully small considering the vast and prolific field of …

Effect Of Ga Content On Defect States In Cuin1-XGaXSe2 Photovoltaic Devices, Jennifer T. Heath, J. David Cohen, William N. Shafarman, Dongxiang Liao, Angus Rockett

Faculty Publications

Defects in the band gap of CuIn_1-xGa_xSe₂ have been characterized using transient photocapacitance spectroscopy. The measured spectra clearly show response from a band of defects centered around 0.8 eV from the valence band edge as well as an exponential distribution of band tail states. Despite Ga contents ranging from Ga/(In+Ga)=0.0 to 0.8, the defect bandwidth and its position relative to the valence band remain constant. This defect band may act as an important recombination center, contributing to the decrease in device efficiency with increasing Ga content.

The Effect Of Weak Acids Hydrolysis On The Sol-Gel Fabrication Of Silica Thin Film, Abdul Hamid

Student Works (2000-2009)

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Modelling Of Space Charge Effects In The Electrical Discharge Of Nitrogen Gas Laser, Chin Yang Chia

Student Works (2000-2009)

A computer model for the simulation of a nitrogen gas discharge has been built and studied. This model was based on the fluid description of the discharge plasma. The Phoenical SHASTA Flux-Corrected Transport (FCT) algorithm is used for the solution of the fluid equations and its accuracy has been tested. The distribution of the local electrical field was calculated by the Poisson equation. The internal discharge current was calculated by Sato's equation. The motion of the charge particles was taken into account. The electrical discharge behavior was simulated by the circuit equation and solved using the fourth order Runge-Kutta method …

A 0.5 Μm Thick Polysilicon Schottky Diode With Rectification Ratio Of 10^6, Elena A. Guliants, Chunhai Ji, Young J. Song, Wayne A. Anderson

Electrical and Computer Engineering Faculty Publications

Polycrystalline Si films, 0.5-mm thick, were obtained as a result of metal-induced growth by sputtering from a Si target on 25 nm thick Ni prelayers at 525 °C. Silicon grew heteroepitaxially on the NiSi2 layer formed due to the reaction between the sputtered Si atoms and Ni. Schottky diodes were fabricated on the Si films by deposition of a Schottky metal on the front surface of the film while Ni disilicide provided an intimate ohmic contact at the back. A Pd/n-Si diode using an n-Si film annealed for 2 h at 700 °C in forming gas demonstrated a rectification ratio …

Self-Assembly Of Spatially Separated Silicon Structures By Si Heteroepitaxy On Ni Disilicide, Elena A. Guliants, Chunhai Ji, Wayne A. Anderson

Electrical and Computer Engineering Faculty Publications

A nonlithographic approach to produce self-assembled spatially separated Si structures for nanoelectronic applications was developed, employing the metal-induced silicon growth. Densely packed Si whiskers, 500–800 nm thick and up to 2500 nm long, were obtained by magnetron sputtering of Si on a 25 nm thick Ni prelayer at 575 °C. The nucleation of the NiSi2 compound at the Ni–Si interface followed by the Si heteroepitaxy on the lattice-matched NiSi2 is suggested to be the driving force for the whisker formation.

Acceleration Element For Femtosecond Electron Pulse Compression, Bao-Liang Qian, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

An acceleration element is proposed for compressing the electron pulse duration in a femtosecond photoelectron gun. The element is a compact metal cavity with curved-shaped walls. An external voltage is applied to the cavity where a special electric field forms in such a way that the slow electrons in the electron pulse front are accelerated more than the fast electrons, and consequently the electron pulse duration will be compressed. The distribution of the electric field inside the acceleration cavity is analyzed for the geometry of the cavity. The electron dynamics in this acceleration cavity is also investigated numerically. Numerical results …

Electron Pulse Broadening Due To Space Charge Effects In A Photoelectron Gun For Electron Diffraction And Streak Camera Systems, Bao-Liang Qian, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The electron pulse broadening and energy spread, caused by space charge effects, in a photoelectron gun are studied analytically using a fluid model. The model is applicable in both the photocathode-to-mesh region and the postanode electron drift region. It is found that space charge effects in the photocathode-to-mesh region are generally unimportant even for subpicosecond pulses. However, because of the long drift distance, electron pulse broadening due to space charge effects in the drift region is usually significant and could be much larger than the initial electron pulse duration for a subpicosecond electron pulse. Space charge effects can also lead …

Strained Quantum Well Heterostructure : Modeling And Simulation Of 980 Nm Laser, Yew Mun Hung

Student Works (2000-2009)

This thesis concerns the study of a strained quantum well laser diode emitting at wavelength of about 980 nm which is suitable for pumping Er³⁺ doped fiber amplifiers. The concept of a strained quantum well in the design of the active medium of the laser diode is discussed. A model is proposed that incorporates features of the physical structural factors and characteristics of the structure. The theoretical background linked directly to the simulation of the model is to provide calculations and derivations of the optical properties of the modeled structure. Theoretical calculations were made taking into account the variation of …

Laser Intensity Scaling Through Stimulated Scattering In Optical Fibers, Timothy H. Russell

Theses and Dissertations

The influence of stimulated scattering on laser intensity in fiber optic waveguides is examined. Stimulated Brillouin scattering (SBS) in long, multimode optical waveguides is found to generate a Stokes beam that propagates in the fiber LP01 mode. Additionally, the same process is found to combine multiple laser beams into a single spatially coherent source. Limitations in beam cleanup and combining are also investigated to identify ways to overcome them. The last portion of the dissertation theoretically examines suppression of stimulated Raman scattering in fibers to eliminate the restriction this imposes on the power of a fiber laser or amplifier. The …

Microcavity Surface Emitting Laser, Stewart Feld, John P. Loehr, James A. Lott

AFIT Patents

A three-dimensional waveguiding structure for a microcavity surface-emitting laser is described in which native aluminum oxide layers provide control of intracavity waveguiding and the laser optical mode structure of the emitted beam. Microcavity lasers described herein account for the blueshift of the emission wavelength as the laser lateral dimensions are reduced to or below the emission wavelength.

Feedback Correction Of Angular Error In Grating Readout, Monish Ranjan Chatterjee, Sundaram Ramachandran

Electrical and Computer Engineering Faculty Publications

Angular and wavelength READ beam errors in holographic interconnection systems are often a recurrent problem. Several strategies have been proposed to minimize or eliminate such READOUT misalignments.

Some years ago, Chatterjee and co-workers proposed a method involving READ beam wavelength tuning to correct output angular errors. In this paper, we investigate the possibility of using an acousto-optic (A-O) Bragg cell with optoelectronic feedback to dynamically correct the scattered beam for deviations in the incidence direction of the READ beam of a hologram. The concept here is based on an acoustic frequency feedback strategy used recently by Balakshy and Kazaryan for …