Electromagnetics and Photonics Commons^™

Surface Plasmon Polaritons And Waveguide Modes At Structured And Inhomogeneous Surfaces, Javier Polanco

Open Access Theses & Dissertations

In chapter 1, properties of a p-polarized surface plasmon polariton are studied, propagating circumferentially around a portion of a cylindrical interface between vacuum and a metal, a situation investigated earlier by M. V. Berry (J. Phys. A: Math. Gen. 8, (1975) 1952). When the metal is convex toward the vacuum this mode is radiative and consequently is attenuated as it propagates on the cylindrical surface. An approximate analytic solution of the dispersion relation for this wave is obtained by an approach different from the one used by Berry, and plots of the real and imaginary parts of its wave number …

Fast-Response Liquid Crystals For Photonic And Display Applications, Jie Sun

Electronic Theses and Dissertations

Liquid crystal devices are attractive for many applications such as information displays, spatial light modulators and adaptive optics, because their optical properties are electrically tunable. However, response time of liquid crystal devices is a serious concern for many applications especially for those who require large phase modulation (≥2π). This is because a thick LC layer is usually needed to achieve a large phase shift while the response time of a nematic LC is highly determined by the cell gap.

Optically Induced Forces In Scanning Probe Microscopy, Dana Kohlgraf-Owens

Electronic Theses and Dissertations

The focus of this dissertation is the study of measuring light not by energy transfer as is done with a standard photodetector such as a photographic film or charged coupled device, but rather by the forces which the light exerts on matter. In this manner we are able to replace or complement standard photodetector-based light detection techniques. One key attribute of force detection is that it permits the measurement of light over a very large range of frequencies including those which are difficult to access with standard photodetectors, such as the far IR and THz. The dissertation addresses the specific …

High Flux Isolated Attosecond Pulse Generation, Yi Wu

Electronic Theses and Dissertations

This thesis outlines the high intensity tabletop attosecond extreme ultraviolet laser source at the Institute for the Frontier of Attosecond Science and Technology Laboratory. First, a unique Ti:Sapphire chirped pulse amplifier laser system that delivers 14 fs pulses with 300 mJ energy at a 10 Hz repetition rate was designed and built. The broadband spectrum extending from 700 nm to 900 nm was obtained by seeding a two stage Ti:Sapphire chirped pulse power amplifier with mJ-level white light pulses from a gas filled hollow core fiber. It is the highest energy level ever achieved by a broadband pulse in a …

Peak Power Scaling Of Nanosecond Pulses In Thulium Based Fiber Lasers, Christian Gaida

Electronic Theses and Dissertations

Thulium based fiber lasers represent a promising alternative for pulse energy scaling and high peak power generation with ytterbium based systems at 1µm. Advantages of thulium arise from the operation at longer wavelengths and a large gain bandwidth (1.8-2.1µm). Nonlinear effects, such as self phase modulation, stimulated Raman scattering and stimulated Brillouin scattering generally limit peak power scaling in fiber lasers. The longer wavelength of thulium fiber lasers and large mode field areas can significantly increase the nonlinear thresholds. Compared to 1µm systems, thulium fiber lasers enable single mode guidance for two times larger mode field diameter in step index …

Time Domain Simulation Of Novel Photovoltaic Materials, Haejun Chung

Open Access Theses

Thin-film silicon-based solar cells have operated far from the Shockley- Queisser limit in all experiments to date. Novel light-trapping structures, however, may help address this limitation. Finite-difference time domain simulation methods offer the potential to accurately determine the light-trapping potential of arbitrary dielectric structures, but suffer from materials modeling problems. In this thesis, existing dispersion models for novel photovoltaic materials will be reviewed, and a novel dispersion model, known as the quadratic complex rational function (QCRF), will be proposed. It has the advantage of accurately fitting experimental semiconductor dielectric values over a wide bandwidth in a numerically stable fashion. Applying …

The Design And Evaluation Of A 5.8 Ghz Laptop-Based Radar System, Kevin Chi-Ming Teng

Open Access Theses

This project involves design and analysis of a 5.8 GHz laptop-based radar system. The radar system measures Doppler, ranging and forming Synthetic Aperture Radar (SAR) images utilizing Matlab software provided from MIT Open Courseware and performs data acquisition and signal processing. The main purpose of this work is to bring new perspective to the existing radar project by increasing the ISM band frequency from 2.4 GHz to 5.8 GHz and to carry out a series of experiments on the implementation of the radar kit. Demonstrating the radar at higher operating frequency is capable of providing accurate data results in Doppler, …

Surface Plasmonic Lens Driven Photoelectron Source For Multi-Beam Applications, Heon Joon Choi

Legacy Theses & Dissertations (2009 - 2024)

Surface plasmon polariton (SPP) assisted photoelectron source array is proposed for use in distributed multiple electron beam lithography applications. Individual source is composed of a metal/dielectric surface structure with concentric circular grooves of subwavelength width surrounding a sub-wavelength aperture. Such optical power concentrators, called "plasmonic lenses", collect light incident over a broad area by converting it to surface electromagnetic waves, specifically SPP's, through diffraction by the sub-wavelength grooves surrounding the aperture. Through constructive interference of the generated SPPs between neighboring grooves, controlled by the periodicity of the grooves, high optical power densities can be achieved at the center of the …

Graphics Processing Unit Acceleration Of Computational Electromagnetic Methods, Matthew Joseph Inman

Electronic Theses and Dissertations

The use of Graphical Processing Units (GPU's) for scientific applications has been evolving and expanding for the decade. GPU's provide an alternative to the CPU in the creation and execution of the numerical codes that are often relied upon in to perform simulations in computational electromagnetics. While originally designed purely to display graphics on the users monitor, GPU's today are essentially powerful floating point co-processors that can be programmed not only to render complex graphics, but also perform the complex mathematical calculations often encountered in scientific computing. Currently the GPU's being produced often contain hundreds of separate cores able to …

Study Of N Incorporation In Insb On Gaas By Molecular Beam Epitaxy For Long Wavelength Infrared Devices, Nimai Chand Patra

Dissertations

The distinguishing features of dilute nitride III-V semiconductors lie in the large simultaneous reduction in the band gap and lattice parameter when N is incorporated in small amounts in an otherwise wide band gap III-V material. In particular, N incorporation in InSb is attracting great attention due to its potential applications in the long wavelength infrared (LWIR) applications. However, the relatively small atomic size of N with respect to Sb makes the growth of good quality InSbN layers challenging with effective N incorporation. In this dissertation we present a correlation of the molecular beam epitaxial growth parameters on the type …

Growth And Characterization Of Zno Based Semiconductor Materials And Devices, Ming Wei

Electronic Theses and Dissertations

Wide band gap semiconductors such as MgxZn1-xO represent an excellent choice for making optical photodetectors and emitters operating in the UV spectral region. High crystal and optical quality MgxZn1-xO thin films were grown epitaxially on c-plane sapphire substrates by plasma-assisted Molecular Beam Epitaxy. ZnO thin films with high crystalline quality, low defect and dislocation densities, and sub-nanometer surface roughness were achieved by applying a low temperature nucleation layer. The critical growth conditions were discussed to obtain a high quality film: the sequence of Zn and O sources for initial growth of nucleation layer, growth temperatures for both ZnO nucleation and …

Injection Locking Of Semiconductor Mode-Locked Lasers For Long-Term Stability Of Widely Tunable Frequency Combs, Charles Williams

Electronic Theses and Dissertations

Harmonically mode-locked semiconductor lasers with external ring cavities offer high repetition rate pulse trains while maintaining low optical linewidth via long cavity storage times. Single frequency injection locking generates widely-spaced and tunable frequency combs from these harmonically mode-locked lasers, while stabilizing the optical frequencies. The output is stabilized long-term with the help of a feedback loop utilizing either a novel technique based on Pound-Drever-Hall stabilization or by polarization spectroscopy. Error signals of both techniques are simulated and compared to experimentally obtained signals. Frequency combs spaced by 2.5 GHz and ~10 GHz are generated, with demonstrated optical sidemode suppression of unwanted …

Mesoscale Light-Matter Interactions, Kyle Douglass

Electronic Theses and Dissertations

Mesoscale optical phenomena occur when light interacts with a number of different types of materials, such as biological and chemical systems and fabricated nanostructures. As a framework, mesoscale optics unifies the interpretations of the interaction of light with complex media when the outcome depends significantly upon the scale of the interaction. Most importantly, it guides the process of designing an optical sensing technique by focusing on the nature and amount of information that can be extracted from a measurement. Different aspects of mesoscale optics are addressed in this dissertation which led to the solution of a number of problems in …

Fabrication Of Metallic Antenna Arrays Using Nanoimprint Lithography, Yu-Wei Lin

Electronic Theses and Dissertations

This Thesis describes the development of a cost-effective process for patterning nanoscale metal antenna arrays. Soft ultraviolet (UV) Nanoimprint Lithography (NIL) into bilayer resist was chosen since it enables repeatable large-scale replication of nanoscale patterns with good lift-off properties using a simple low-cost process. Nanofabrication often involves the use of Electron Beam Lithography (EBL) which enables the definition of nanoscale patterns on small sample regions, typically < 1 mm 2 . However its sequential nature makes the large scale production of nanostructured substrates using EBL cost-prohibitive. NIL is a pattern replication method that can reproduce nanoscale patterns in a parallel fashion, allowing the low-cost and rapid production of a large number of nanopatterned samples based on a single nanostructured master mold. Standard NIL replicates patterns by pressing a nanostructured hard mold into a soft resist layer on a substrate resulting in exposed substrate regions, followed by an optional Reactive Ion Etching (RIE) step and the subsequent deposition of e.g. metal onto the exposed substrate area. However, non-vertical sidewalls of the features in the resist layer resulting from an imperfect hard mold, from reflow of the resist layer, or from isotropic etching in the RIE step iii may cause imperfect lift-off. To overcome this problem, a bilayer resist method can be used. Using stacked resist layers with different etch rates, undercut structures can be obtained after the RIE step, allowing for easy lift-off even when using a mold with non-vertical sidewalls. Experiments were carried out using a nanostructured negative SiO2 master mold. Various material combinations and processing methods were explored. The negative master mold was transferred to a positive soft mold, leaving the original master mold unaltered. The soft mold consisted of a 5 m thick top Poly(methyl methacrylate) (PMMA), or Polyvinyl alcohol (PVA) layer, a 1.5 mm thick Polydimethylsiloxane (PDMS) buffer layer, and a glass supporting substrate. The soft mold was pressed into a bilayer of 300 nm PMMA and 350 nm of silicon based UV-curable resist that was spin-coated onto a glass slide, and cured using UV radiation. The imprinted patterns were etched using RIE, exposing the substrate, followed by metal deposition and lift-off. The experiments show that the use of soft molds enables successful pattern transfer even in the presence of small dust particles between the mold and the resist layer. Feature sizes down to 280 nm were replicated successfully

Volume Phase Masks In Photo-Thermo-Refractive Glass, Marc Segall

Electronic Theses and Dissertations

In many applications such as beam shaping, mode conversion, and phase encoding it is necessary to alter the spatial phase profile of a beam via a phase mask. Conventional techniques to accomplish this either involve surface relief profiling in thin films such as PMMA or refractive index modulation in bulk photorefractive crystals such as lithium niobate. These materials have been used extensively for the past several decades and perform admirably in low power conditions. However, in high power systems these materials will be destroyed, requiring a new means of producing phase masks. In this dissertation a method for producing robust …

Phase-Locking Stability Of A Quasi-Single-Cycle Pulse, Nathan Bodnar

Electronic Theses and Dissertations

There is increasing interest in the generation of very short laser pulses, even down to attosecond (10-18 s) durations. Laser systems with femtosecond pulse durations are needed for these applications. For many of these applications, positioning of the maximum electric field within the pulse envelope can affect the outcome. The peak of the electric field relative to the peak of the pulse is called the Carrier Envelope Phase (CEP). Controlling the position of the electric field becomes more important when pulse duration approaches single-cycle. This thesis focuses on the stabilization of a quasi-single-cycle laser facility. Improvements to this already-established laser …

Mode-Division Multiplexed Transmission In Few-Mode Fibers, Neng Bai

Electronic Theses and Dissertations

As a promising candidate to break the single-mode fiber capacity limit, mode-division multiplexing (MDM) explores the spatial dimension to increase transmission capacity in fiberoptic communication. Two linear impairments, namely loss and multimode interference, present fundamental challenges to implementing MDM. In this dissertation, techniques to resolve these two issues are presented. To de-multiplex signals subject to multimode interference in MDM, Multiple-InputMultiple-Output (MIMO) processing using adaptive frequency-domain equalization (FDE) is proposed and investigated. Both simulations and experiments validate that FDE can reduce the algorithmic complexity significantly in comparison with the conventional time-domain equalization (TDE) while achieving similar performance as TDE. To further …

Development Of Thulium Fiber Lasers For High Average Power And High Peak Power Operation, Robert Sims

Electronic Theses and Dissertations

High power thulium fiber lasers are useful for a number of applications in both continuous-wave and pulsed operating regimes. The use of thulium as a dopant has recently gained interest due to its large bandwidth, possibility of high efficiency, possibility of high power and long wavelength ~1.8 – 2.1 μm. The longer emission wavelength of Tm-doped fiber lasers compared to Yb- and/or Er-doped fiber lasers creates the possibility for higher peak power operation due to the larger nonlinear thresholds and reduced nonlinear phase accumulation. One primary interest in Tm-doped fiber lasers has been to scale to high average powers; however, …

A Tunable Electromagnetic Band-Gap Microstrip Filter, Greg A. Lancaster

Master's Theses

In high frequency design, harmonic suppression is a persistent struggle. Non-linear devices such as switches and amplifiers produce unwanted harmonics which may interfere with other frequency bands. Filtering is a widely accepted solution, however there are various shortcomings involved. Suppressing multiple harmonics, if desired, with traditional lumped element and distributed component band-stop filters requires using multiple filters. These topologies are not easily made tunable either. A new filter topology is investigated called Electromagnetic Band-Gap (EBG) structures.

EBG structures have recently gained the interest of microwave designers due to their periodic nature which prohibits the propagation of certain frequency bands. EBG …

Absorptive And Refractive Optical Nonlinearities In Organic Molecules And Semiconductors, Davorin Peceli

Electronic Theses and Dissertations

The main purpose of this dissertation to investigate photophysical properties, third order nonlinearity and free carrier absorption and refraction in organic materials and semiconductors. Special emphasis of this dissertation is on characterization techniques of molecules with enhanced intersystem crossing rate and study of different approaches of increasing triplet quantum yield in organic molecules. Both linear and nonlinear characterization methods are described. Linear spectroscopic characterization includes absorption, fluorescence, quantum yield, anisotropy, and singletoxygen generation measurements. Nonlinear characterization, performed by picosecond and femtosecond laser systems (single and double pump-probe and Z-scan measurements), includes measurements of the triplet quantum yields, excited-state absorption, two-photon …