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(1 - 17 of 17)
- Title
- SURFACE PLASMON HOSTS FOR INFRARED WAVEGUIDES AND BIOSENSORS, AND PLASMONS IN GOLD-BLACK NANO-STRUCTURED FILMS.
- Creator
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Cleary, Justin, Peale, Robert, University of Central Florida
- Abstract / Description
-
Applications of surface plasmon polaritons (SPPs) have thus far emphasized visible and near-infrared wavelengths. Extension into the long-wave infrared (LWIR) has numerous potential advantages for biosensors and waveguides, which are explored in this work. A surface plasmon resonance (SPR) biosensor that operates deep into the infrared (3-11 µm wavelengths) is potentially capable of biomolecule recognition based on both selective binding and characteristic...
Show moreApplications of surface plasmon polaritons (SPPs) have thus far emphasized visible and near-infrared wavelengths. Extension into the long-wave infrared (LWIR) has numerous potential advantages for biosensors and waveguides, which are explored in this work. A surface plasmon resonance (SPR) biosensor that operates deep into the infrared (3-11 µm wavelengths) is potentially capable of biomolecule recognition based on both selective binding and characteristic vibrational modes. The goal is to operate such sensors at wavelengths where biological analytes are strongly differentiated by their IR absorption spectra and where the refractive index is increased by dispersion, which will provide enhanced selectivity and sensitivity. Potentially useful IR surface plasmon resonances are investigated on lamellar gratings formed from various materials with plasma frequencies in the IR wavelength range including doped semiconductors, semimetals, and conducting polymers. One outcome of this work has been the demonstration of a simple analytic formula for calculating the SPP absorption resonances in the angular reflectance spectra of gratings. It is demonstrated for Ag lamellar gratings in the 6-11 µm wavelength range. The recipe is semi-empirical, requiring knowledge of a surface-impedance modulation amplitude, which is found here by comparison to experiment as a function of the grating groove depth and the wavelength. The optimum groove depth for photon-to-SPP energy conversion was found by experiment and calculation to be ~10-15% of the wavelength. Hemicylindrical prism couplers formed from Si or Ge were investigated as IR surface plasmon couplers for the biosensor application. Strong Fabry-Perot oscillations in the angular reflectance spectra for these high index materials suggest that grating couplers will be more effective for this application in the LWIR. A variety of materials having IR plasma frequencies were investigated due to the tighter SPP mode confinement anticipated in the IR than for traditional noble metals. First doped-Si and metal silicides (Ni, Pd, Pt and Ti) were investigated due to their inherent CMOS compatibility. Rutherford backscattering spectroscopy, x-ray diffraction, scanning electron microscopy, secondary ion mass spectrometry and four point probe measurements complemented the optical characterization by ellipsometry. Calculation of propagation length and mode confinement from measured permittivities demonstrated the suitability for these materials for LWIR SPP applications. Semimetals were also investigated since their plasma frequencies are intermediate between those of doped silicon and metal silicides. The semimetal antimony, with a plasma frequency ~80 times less than that of gold was characterized. Relevant IR surface plasmon properties, including the propagation length and penetration depths for SPP fields, were determined from optical constants measured in the LWIR. Distinct resonances due to SPP generation were observed in angular reflection spectra of Sb lamellar gratings in the wavelength range of 6 to 11 µm. Though the real part of the permittivity is positive in this range, which violates the usual condition for the existence of bound SPP modes, calculations based on experimental permittivity showed that there is little to distinguish bound from unbound SPP modes for this material. The SPP mode decays exponentially away from the surface on both sides of the permittivity sign change. Water is found to broaden the IR plasmon resonances significantly at 9.25 micron wavelength where aqueous extinction is large. Much sharper resonances for water based IR SPR biosensor can be achieved in the 3.5 to 5.5 µm range. Nano-structured Au films (Au-black) were investigated as IR absorbers and possible solar cell enhancers based on surface plasmon resonance. The characteristic length scales of the structured films vary considerably as a function of deposition parameters, but the absorbance is found to be only weakly correlated with these distributions. Structured Au-black with a broad range of cluster length scales appear to be able to support multiple SPP modes with incident light coupling to the corrugated surface as seen by photoelectron emission microscopy (PEEM) and SPR experiments, supporting the hypothesis that Au-black may be a suitable material for plasmon-resonance enhancement solar-cell efficiency over the broad solar spectrum.
Show less - Date Issued
- 2010
- Identifier
- CFE0003231, ucf:48547
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003231
- Title
- RIGOROUS ANALYSIS OF WAVE GUIDING AND DIFFRACTIVE INTEGRATED OPTICAL STRUCTURES.
- Creator
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Greenwell, Andrew, Moharam, M.G., University of Central Florida
- Abstract / Description
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The realization of wavelength scale and sub-wavelength scale fabrication of integrated optical devices has led to a concurrent need for computational design tools that can accurately model electromagnetic phenomena on these length scales. This dissertation describes the physical, analytical, numerical, and software developments utilized for practical implementation of two particular frequency domain design tools: the modal method for multilayer waveguides and one-dimensional lamellar gratings...
Show moreThe realization of wavelength scale and sub-wavelength scale fabrication of integrated optical devices has led to a concurrent need for computational design tools that can accurately model electromagnetic phenomena on these length scales. This dissertation describes the physical, analytical, numerical, and software developments utilized for practical implementation of two particular frequency domain design tools: the modal method for multilayer waveguides and one-dimensional lamellar gratings and the Rigorous Coupled Wave Analysis (RCWA) for 1D, 2D, and 3D periodic optical structures and integrated optical devices. These design tools, including some novel numerical and programming extensions developed during the course of this work, were then applied to investigate the design of a few unique integrated waveguide and grating structures and the associated physical phenomena exploited by those structures. The properties and design of a multilayer, multimode waveguide-grating, guided mode resonance (GMR) filter are investigated. The multilayer, multimode GMR filters studied consist of alternating high and low refractive index layers of various thicknesses with a binary grating etched into the top layer. The separation of spectral wavelength resonances supported by a multimode GMR structure with fixed grating parameters is shown to be controllable from coarse to fine through the use of tightly controlled, but realizable, choices for multiple layer thicknesses in a two material waveguide; effectively performing the simultaneous engineering of the wavelength dispersion for multiple waveguide grating modes. This idea of simultaneous dispersion band tailoring is then used to design a multilayer, multimode GMR filter that possesses broadened angular acceptance for multiple wavelengths incident at a single angle of incidence. The effect of a steady-state linear loss or gain on the wavelength response of a GMR filter is studied. A linear loss added to the primary guiding layer of a GMR filter is shown to produce enhanced resonant absorption of light by the GMR structure. Similarly, linear gain added to the guiding layer is shown to produce enhanced resonant reflection and transmission from a GMR structure with decreased spectral line width. A combination of 2D and 3D modeling is utilized to investigate the properties of an embedded waveguide grating structure used in filtering/reflecting an incident guided mode. For the embedded waveguide grating, 2D modeling suggests the possibility of using low index periodic inclusions to create an embedded grating resonant filter, but the results of 3D RCWA modeling suggest that transverse low index periodic inclusions produce a resonant lossy cavity as opposed to a resonant reflecting mirror. A novel concept for an all-dielectric unidirectional dual grating output coupler is proposed and rigorously analyzed. A multilayer, single-mode, high and graded-index, slab waveguide is placed atop a slightly lower index substrate. The properties of the individual gratings etched into the waveguide's cover/air and substrate/air interfaces are then chosen such that no propagating diffracted orders are present in the device superstrate and only a single order is present outside the structure in the substrate. The concept produces a robust output coupler that requires neither phase-matching of the two gratings nor any resonances in the structure, and is very tolerant to potential errors in fabrication. Up to 96% coupling efficiency from the substrate-side grating is obtained over a wide range of grating properties.
Show less - Date Issued
- 2007
- Identifier
- CFE0001635, ucf:47244
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001635
- Title
- Hybrid integration of second- and third-order highly nonlinear waveguides on silicon substrates.
- Creator
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Camacho Gonzalez, Guillermo Fernando, Fathpour, Sasan, Likamwa, Patrick, Amezcua Correa, Rodrigo, Peale, Robert, University of Central Florida
- Abstract / Description
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In order to extend the capabilities and applications of silicon photonics, other materials and compatible technologies have been developed and integrated on silicon substrates. A particular class of integrable materials are those with high second- and third-order nonlinear optical properties. This work presents contributions made to nonlinear integrated photonics on silicon substrates, including chalcogenide waveguides for over an octave supercontinuum generation, and rib-loaded thin-film...
Show moreIn order to extend the capabilities and applications of silicon photonics, other materials and compatible technologies have been developed and integrated on silicon substrates. A particular class of integrable materials are those with high second- and third-order nonlinear optical properties. This work presents contributions made to nonlinear integrated photonics on silicon substrates, including chalcogenide waveguides for over an octave supercontinuum generation, and rib-loaded thin-film lithium niobate waveguides for highly efficient second-harmonic generation. Through the pursuit of hybrid integration of the two types of waveguides for applications such as on-chip self-referenced optical frequency combs, we have experimentally demonstrated fabrication integrability of chalcogenide and thin-film lithium niobate waveguides in a single chip and a pathway for both second- and third-order nonlinearities occurring therein. Accordingly, design specifications for an efficient nonlinear integrated waveguide are reported, showing over an octave supercontinuum generation and frequency selectivity for second-harmonic generation, enabling potentials of on-chip interferometry techniques for carrier-envelope offset detection, and hence stabilized optical combs.
Show less - Date Issued
- 2019
- Identifier
- CFE0007607, ucf:52560
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007607
- Title
- DISCRETE WAVE PROPAGATION IN QUADRATICALLY NONLINEAR MEDIA.
- Creator
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Iwanow, Robert, Stegeman, George, University of Central Florida
- Abstract / Description
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Discrete models are used in describing various microscopic phenomena in many branches of science, ranging from biology through chemistry to physics. Arrays of evanescently coupled, equally spaced, identical waveguides are prime examples of optical structures in which discrete dynamics can be easily observed and investigated. As a result of discretization, these structures exhibit unique diffraction properties with no analogy in continuous systems. Recently nonlinear discrete optics has...
Show moreDiscrete models are used in describing various microscopic phenomena in many branches of science, ranging from biology through chemistry to physics. Arrays of evanescently coupled, equally spaced, identical waveguides are prime examples of optical structures in which discrete dynamics can be easily observed and investigated. As a result of discretization, these structures exhibit unique diffraction properties with no analogy in continuous systems. Recently nonlinear discrete optics has attracted a growing interest, triggered by the observation of discrete solitons in AlGaAs waveguide arrays reported by Eisenberg et al. in 1998. So far, the following experiments involved systems with third order nonlinearities. In this work, an experimental investigation of discrete nonlinear wave propagation in a second order nonlinear medium is presented. This system deserves particular attention because the nonlinear process involves two or three components at different frequencies mutually locked by a quadratic nonlinearity, and new degrees of freedom enter the dynamical process. In the first part of dissertation, observation of the discrete Talbot effect is reported. In contrast to continuous systems, where Talbot self-imaging effect occurs irrespective of the pattern period, in discrete configurations this process is only possible for a specific set of periodicities. The major part of the dissertation is devoted to the investigation of soliton formation in lithium niobate waveguide arrays with a tunable cascaded quadratic nonlinearity. Soliton species with different topology (unstaggered – all channels in-phase, and staggered – neighboring channels with a pi relative phase difference) are identified in the same array. The stability of the discrete solitons and plane waves (modulational instability) are experimentally investigated. In the last part of the dissertation, a phase-insensitive, ultrafast, all-optical spatial switching and frequency conversion device based on quadratic waveguide array is demonstrated. Spatial routing and wavelength conversion of milliwatt signals is achieved without pulse distortions.
Show less - Date Issued
- 2005
- Identifier
- CFE0000420, ucf:46382
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000420
- Title
- EVALUATION OF THE PHOTO-INDUCED STRUCTURAL MECHANISMS IN CHALCOGENIDE GLASS MATERIALS.
- Creator
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Lopez, Cedric, Richardson, Kathleen, University of Central Florida
- Abstract / Description
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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...
Show moreChalcogenide 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 As-S-Se system has been established. Key structural and optical differences have been observed and quantified between bulk glasses and their corresponding as-deposited films. The importance of annealing and aging of the film material and the impact on photosentivity and long term behavior important to subsequent device stability have been evaluated. Photo-induced structures have been created in the thin films using bandgap cw and sub-bandgap femtosecond laser sources and the exposure conditions and their influence on the post-exposure material properties, have been found to have different limitations and driving mechanisms. These mechanisms largely depend on both structural and/or electronic defects, whether initially present in the chalcogenide material or created upon exposure. These defect processes, largely studied previously in individual binary material systems, have now been shown to be consistently present, but varying in extent, across the ternary glass compositions and exposure conditions examined. We thus establish the varying photo-response of these defects as being the major reason for the optical variations observed. Nonlinear optical material properties, as related to the multiphoton processes used in our exposure studies, have been modeled and a tentative explanation for their variation in the context of composition and method of evaluation is presented.
Show less - Date Issued
- 2004
- Identifier
- CFE0000196, ucf:46177
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000196
- Title
- OPTICAL WAVE PROPAGATION IN DISCRETE WAVEGUIDE ARRAYS.
- Creator
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Hudock, Jared, Christodoulides, Demetrios, University of Central Florida
- Abstract / Description
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The propagation dynamics of light in optical waveguide arrays is characteristic of that encountered in discrete systems. As a result, it is possible to engineer the diffraction properties of such structures, which leads to the ability to control the flow of light in ways that are impossible in continuous media. In this work, a detailed theoretical investigation of both linear and nonlinear optical wave propagation in one- and two-dimensional waveguide lattices is presented. The ability to...
Show moreThe propagation dynamics of light in optical waveguide arrays is characteristic of that encountered in discrete systems. As a result, it is possible to engineer the diffraction properties of such structures, which leads to the ability to control the flow of light in ways that are impossible in continuous media. In this work, a detailed theoretical investigation of both linear and nonlinear optical wave propagation in one- and two-dimensional waveguide lattices is presented. The ability to completely overcome the effects of discrete diffraction through the mutual trapping of two orthogonally polarized coherent beams interacting in Kerr nonlinear arrays of birefringent waveguides is discussed. The existence and stability of such highly localized vector discrete solitons is analyzed and compared to similar scenarios in a single birefringent waveguide. This mutual trapping is also shown to occur within the first few waveguides of a semi-infinite array leading to the existence of vector discrete surface waves. Interfaces between two detuned semi-infinite waveguide arrays or waveguide array heterojunctions and their possible applications are also considered. It is shown that the detuning between the two arrays shifts the dispersion relation of one array with respect to the other. Consequently, these systems provide spatial filtering functions that may prove useful in future all-optical networks. In addition by exploiting the unique diffraction properties of discrete arrays, diffraction compensation can be achieved in a way analogous to dispersion compensation in dispersion managed optical fiber systems. Finally, it is demonstrated that both the linear (diffraction) and nonlinear dynamics of two-dimensional waveguide arrays are significantly more complex and considerably more versatile than their one-dimensional counterparts. As is the case in one-dimensional arrays, the discrete diffraction properties of these two-dimensional lattices can be effectively altered depending on the propagation Bloch k-vector within the first Brillouin zone. In general, this diffraction behavior is anisotropic and as a result, allows the existence of a new class of discrete elliptic solitons in the nonlinear regime. Moreover, such arrays support two-dimensional vector soliton states, and their existence and stability are also thoroughly explored in this work.
Show less - Date Issued
- 2005
- Identifier
- CFE0000833, ucf:46687
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000833
- Title
- Thermal and Waveguide Optimization of Broad Area Quantum Cascade Laser Performance.
- Creator
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Suttinger, Matthew, Lyakh, Arkadiy, Bass, Michael, Vodopyanov, Konstantin, University of Central Florida
- Abstract / Description
-
Quantum Cascade Lasers are a novel source of coherent infrared light, unique in their tunability over the mid-infrared and terahertz range of frequencies. Advances in bandgap engineering and semiconductor processing techniques in recent years have led to the development of highly efficient quantum cascade lasers capable of room temperature operation. Recent work has demonstrated power scaling with broad area quantum cascade lasers by increasing active region width beyond the standard ~10 ?m....
Show moreQuantum Cascade Lasers are a novel source of coherent infrared light, unique in their tunability over the mid-infrared and terahertz range of frequencies. Advances in bandgap engineering and semiconductor processing techniques in recent years have led to the development of highly efficient quantum cascade lasers capable of room temperature operation. Recent work has demonstrated power scaling with broad area quantum cascade lasers by increasing active region width beyond the standard ~10 ?m. Taking into account thermal effects caused by driving a device with electrical power, an experimentally fitted model is developed to predict the optical power output in both pulsed and continuous operation with varying device geometry and minor changes to quantum cascade laser active region design. The effects of the characteristic temperatures of threshold current density and slope efficiency, active region geometry, and doping, on output power are studied in the model. The model is then used to refine the active region design for increased power out in continuous operation for a broad area design. Upon testing the new design, new thermal effects on rollover current density are observed. The model is then refined to reflect the new findings and more accurately predict output power characteristics.
Show less - Date Issued
- 2017
- Identifier
- CFE0007296, ucf:52174
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007296
- Title
- Wavelength scale resonant structures for integrated photonic applications.
- Creator
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Weed, Matthew, Schoenfeld, Winston, Moharam, M., Likamwa, Patrick, Delfyett, Peter, Leuenberger, Michael, University of Central Florida
- Abstract / Description
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An approach to integrated frequency-comb filtering is presented, building from a background in photonic crystal cavity design and fabrication. Previous work in the development of quantum information processing devices through integrated photonic crystals consists of photonic band gap engineering and methods of on-chip photon transfer. This work leads directly to research into coupled-resonator optical waveguides which stands as a basis for the primary line of investigation. These coupled...
Show moreAn approach to integrated frequency-comb filtering is presented, building from a background in photonic crystal cavity design and fabrication. Previous work in the development of quantum information processing devices through integrated photonic crystals consists of photonic band gap engineering and methods of on-chip photon transfer. This work leads directly to research into coupled-resonator optical waveguides which stands as a basis for the primary line of investigation. These coupled cavity systems offer the designer slow light propagation which increases photon lifetime, reduces size limitations toward on-chip integration, and offers enhanced light-matter interaction. A unique resonant structure explained by various numerical models enables comb-like resonant clusters in systems that otherwise have no such regular resonant landscape (e.g. photonic crystal cavities). Through design, simulation, fabrication and test, the work presented here is a thorough validation for the future potential of coupled-resonator filters in frequency comb laser sources.
Show less - Date Issued
- 2013
- Identifier
- CFE0004957, ucf:49568
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004957
- Title
- Silicon photonic devices for optical delay lines and mid infrared applications.
- Creator
-
Khan, Saeed, Fathpour, Sasan, Likamwa, Patrick, Gong, Xun, Delfyett, Peter, Schoenfeld, Winston, University of Central Florida
- Abstract / Description
-
Silicon photonics has been a rapidly growing subfield of integrated optics and optoelectronic in the last decade and is currently considered a mature technology. The main thrust behind the growth is its compatibility with the mature and low-cost microelectronic integrated circuits fabrication process. In recent years, several active and passive photonic devices and circuits have been demonstrated on silicon. Optical delay lines are among important silicon photonic devices, which are essential...
Show moreSilicon photonics has been a rapidly growing subfield of integrated optics and optoelectronic in the last decade and is currently considered a mature technology. The main thrust behind the growth is its compatibility with the mature and low-cost microelectronic integrated circuits fabrication process. In recent years, several active and passive photonic devices and circuits have been demonstrated on silicon. Optical delay lines are among important silicon photonic devices, which are essential for a variety of photonic system applications including optical beam-forming for controlling phased-array antennas, optical communication and networking systems and optical coherence tomography. In this thesis, several types of delay lines based on apodized grating waveguides are proposed and demonstrated. Simulation and experimental results suggest that these novel devices can provide high optical delay and tunability at very high bit rate. While most of silicon photonics research has focused in the near-infrared wavelengths, extending the operating wavelength range of the technology into in the 3(-)5 (&)#181;m, or the mid-wave infrared regime, is a more recent field of research. A key challenge has been that the standard silicon-on-insulator waveguides are not suitable for the mid-infrared, since the material loss of the buried oxide layer becomes substantially high. Here, the silicon-on-sapphire waveguide technology, which can extend silicon's operating wavelength range up to 4.4 (&)#181;m, is investigated. Furthermore, silicon-on-nitride waveguides, boasting a wide transparent range of 1.2(-)6.7 ?m, are demonstrated and characterized for the first time at both mid-infrared (3.39 ?m) and near-infrared (1.55 ?m) wavelengths.
Show less - Date Issued
- 2013
- Identifier
- CFE0005014, ucf:49996
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005014
- Title
- DESIGN AND OPTIMIZATION OF NANOSTRUCTURED OPTICAL FILTERS.
- Creator
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Brown, Jeremiah, Moharam, Jim, University of Central Florida
- Abstract / Description
-
Optical filters encompass a vast array of devices and structures for a wide variety of applications. Generally speaking, an optical filter is some structure that applies a designed amplitude and phase transform to an incident signal. Different classes of filters have vastly divergent characteristics, and one of the challenges in the optical design process is identifying the ideal filter for a given application and optimizing it to obtain a specific response. In particular, it is highly...
Show moreOptical filters encompass a vast array of devices and structures for a wide variety of applications. Generally speaking, an optical filter is some structure that applies a designed amplitude and phase transform to an incident signal. Different classes of filters have vastly divergent characteristics, and one of the challenges in the optical design process is identifying the ideal filter for a given application and optimizing it to obtain a specific response. In particular, it is highly advantageous to obtain a filter that can be seamlessly integrated into an overall device package without requiring exotic fabrication steps, extremely sensitive alignments, or complicated conversions between optical and electrical signals. This dissertation explores three classes of nano-scale optical filters in an effort to obtain different types of dispersive response functions. First, dispersive waveguides are designed using a sub-wavelength periodic structure to transmit a single TE propagating mode with very high second order dispersion. Next, an innovative approach for decoupling waveguide trajectories from Bragg gratings is outlined and used to obtain a uniform second-order dispersion response while minimizing fabrication limitations. Finally, high Q-factor microcavities are coupled into axisymmetric pillar structures that offer extremely high group delay over very narrow transmission bandwidths. While these three novel filters are quite diverse in their operation and target applications, they offer extremely compact structures given the magnitude of the dispersion or group delay they introduce to an incident signal. They are also designed and structured as to be formed on an optical wafer scale using standard integrated circuit fabrication techniques. A number of frequency-domain numerical simulation methods are developed to fully characterize and model each of the different filters. The complete filter response, which includes the dispersion and delay characteristics and optical coupling, is used to evaluate each filter design concept. However, due to the complex nature of the structure geometries and electromagnetic interactions, an iterative optimization approach is required to improve the structure designs and obtain a suitable response. To this end, a Particle Swarm Optimization algorithm is developed and applied to the simulated filter responses to generate optimal filter designs.
Show less - Date Issued
- 2008
- Identifier
- CFE0002502, ucf:47678
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002502
- Title
- FINITE ELEMENT ANALYSIS OF LEFT-HANDED WAVEGUIDES.
- Creator
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Vellakkinar Balasubramaniam, Satish, Wu, Thomas X, University of Central Florida
- Abstract / Description
-
In this work, waveguides with simultaneous negative dielectric permittivity and magnetic permeability, otherwise known as left-handed waveguides, are investigated. An approach of formulating and solving an eigenvalue problem with finite element method resulting in the dispersion relation of the waveguides is adopted in the analysis. Detailed methodology of one-dimensional scalar and two-dimensional vector finite element formulation for the analysis of grounded slab and arbitrary shaped...
Show moreIn this work, waveguides with simultaneous negative dielectric permittivity and magnetic permeability, otherwise known as left-handed waveguides, are investigated. An approach of formulating and solving an eigenvalue problem with finite element method resulting in the dispersion relation of the waveguides is adopted in the analysis. Detailed methodology of one-dimensional scalar and two-dimensional vector finite element formulation for the analysis of grounded slab and arbitrary shaped waveguides is presented. Based on the analysis, for waveguides with conventional media, excellent agreement of results is observed between the finite element approach and the traditional approach. The method is then applied to analyze left-handed waveguides and anomalous dispersion of modes is found. The discontinuity structure of a left-handed waveguide sandwiched between two conventional dielectric slab waveguides is analyzed using mode matching technique and the results are discussed based on the inherent nature of the materials. The scattering characteristics of a parallel plate waveguide partially filled with left-handed and conventional media are also analyzed using finite element method with eigenfunction expansion technique.
Show less - Date Issued
- 2004
- Identifier
- CFE0000296, ucf:46208
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000296
- Title
- Improved system for fabrication and characterization of nanophotonic devices by multi-photon lithography.
- Creator
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Sharma, Rashi, Kuebler, Stephen, Zou, Shengli, Huo, Qun, Beazley, Melanie, Phanstiel, Otto, University of Central Florida
- Abstract / Description
-
A new system for multi-photon lithography (MPL) was developed and used to fabricate three-dimensional (3D) structures with higher aspect ratio, better resolution, improved fidelity, and reduced structural distortion relative to a conventional implementation of MPL.A set of curved waveguides (Rbend = 19 (&)#181;m, and 38 (&)#181;m) and straight waveguides (length = 50 (&)#181;m, Rbend = ?) were fabricated in an epoxide photopolymer and optically characterized using light having a wavelength in...
Show moreA new system for multi-photon lithography (MPL) was developed and used to fabricate three-dimensional (3D) structures with higher aspect ratio, better resolution, improved fidelity, and reduced structural distortion relative to a conventional implementation of MPL.A set of curved waveguides (Rbend = 19 (&)#181;m, and 38 (&)#181;m) and straight waveguides (length = 50 (&)#181;m, Rbend = ?) were fabricated in an epoxide photopolymer and optically characterized using light having a wavelength in vacuum of ?0 = 2.94 (&)#181;m. The optical performance of the waveguides was compared to novel spatially-variant photonic crystals (SVPCs) previously studied in the group. The waveguides were found to guide light with 90% lower efficiency, due to mode leakage. The study provides further evidence that SVPCs operate not through total internal reflection, but rather through self-collimation, as designed.3D uniform-lattice photonic crystals (ULPCs) were fabricated by MPL using a commercial acrylate photopolymer. The ULPCs were optically characterized at ?0 = 1.55 (&)#181;m. A laser beam with adjustable bandwidth was used to measure the self-collimation in the ULPCs. For the low bandwidth beam, vertically polarized light was self-collimated, whereas horizontally polarized light diverged. The transmission efficiency of the ULPCs was also measured as a function of fill factor. The ULPC having a fill factor of 48% exhibited 80% transmission.An etching process was also developed for non-destructively removing Au/Pd coatings that must be deposited onto structures to image them by scanning electron microscopy. The structural and optical integrity of the samples was found to be maintained despite etching. The sputter-coated sample sustained no structural damage when exposed to the ?0 = 1.55 (&)#181;m. However, the metal coating resulted in diminished transmission efficiency due to the high reflection of the 1.55 (&)#181;m beam by the metal coating.
Show less - Date Issued
- 2018
- Identifier
- CFE0007767, ucf:52380
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007767
- Title
- Photon Statistics in Disordered Lattices.
- Creator
-
Kondakci, Hasan, Saleh, Bahaa, Abouraddy, Ayman, Christodoulides, Demetrios, Mucciolo, Eduardo, University of Central Florida
- Abstract / Description
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Propagation of coherent waves through disordered media, whether optical, acoustic, or radio waves, results in a spatially redistributed random intensity pattern known as speckle -- a statistical phenomenon. The subject of this dissertation is the statistics of monochromatic coherent light traversing disordered photonic lattices and its dependence on the disorder class, the level of disorder and the excitation configuration at the input. Throughout the dissertation, two disorder classes are...
Show morePropagation of coherent waves through disordered media, whether optical, acoustic, or radio waves, results in a spatially redistributed random intensity pattern known as speckle -- a statistical phenomenon. The subject of this dissertation is the statistics of monochromatic coherent light traversing disordered photonic lattices and its dependence on the disorder class, the level of disorder and the excitation configuration at the input. Throughout the dissertation, two disorder classes are considered, namely, diagonal and off-diagonal disorders. The latter exhibits disorder-immune chiral symmetry -- the appearance of the eigenmodes in skew-symmetric pairs and the corresponding eigenvalues in opposite signs. When a disordered photonic lattice, an array of evanescently coupled waveguides, is illuminated with an extended coherent optical field, discrete speckle develops. Numerical simulations and analytical modeling reveal that discrete speckle shows a set of surprising features, that are qualitatively indistinguishable in both disorder classes. First, the fingerprint of transverse Anderson localization -- associated with disordered lattices, is exhibited in the narrowing of the spatial coherence function. Second, the transverse coherence length (or speckle grain size) freezes upon propagation. Third, the axial coherence depth is independent of the axial position, thereby resulting in a coherence voxel of fixed volume independently of position.When a single lattice site is coherently excited, I discovered that a thermalization gap emerges for light propagating in disordered lattices endowed with disorder-immune chiral symmetry. In these systems, the span of sub-thermal photon statistics is inaccessible to the input coherent light, which -- once the steady state is reached -- always emerges with super-thermal statistics no matter how small the disorder level. An independent constraint of the input field for the chiral symmetry to be activated and the gap to be observed is formulated. This unique feature enables a new form of photon-statistics interferometry: by exciting two lattice sites with a variable relative phase, as in a traditional two-path interferometer, the excitation-symmetry of the chiral mode pairs is judiciously broken and interferometric control over the photon statistics is exercised, spanning sub-thermal and super-thermal regimes. By considering an ensemble of disorder realizations, this phenomenon is demonstrated experimentally: a deterministic tuning of the intensity fluctuations while the mean intensity remains constant.Finally, I examined the statistics of the emerging light in two different lattice topologies: linear and ring lattices. I showed that the topology dictates the light statistics in the off-diagonal case: for even-sited ring and linear lattices, the electromagnetic field evolves into a single quadrature component, so that the field takes discrete phase values and is non-circular in the complex plane. As a consequence, the statistics become super-thermal. For odd-sited ring lattices, the field becomes random in both quadratures resulting in sub-thermal statistics. However, this effect is suppressed due to the transverse localization of light in lattices with high disorder. In the diagonal case, the lattice topology does not play a role and the transmitted field always acquires random components in both quadratures, hence the phase distribution is uniform in the steady state.
Show less - Date Issued
- 2015
- Identifier
- CFE0005968, ucf:50786
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005968
- Title
- TOWARDS DIRECT WRITING OF 3-D PHOTONIC CIRCUITS USING ULTRAFAST LASERS.
- Creator
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Zoubir, Arnaud, Richardson, Martin, University of Central Florida
- Abstract / Description
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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...
Show moreThe 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, including refractive index profiling and mode analysis. Furthermore, a finite-difference beam propagation method for wave propagation in 3D-waveguides is proposed. The photo-structural modifications underlying the changes in the material optical properties after exposure are investigated. The highly nonlinear processes of the light/matter interaction during the writing process are described using a free electron model. UV/visible absorption spectroscopy, photoluminescence spectroscopy and Raman spectroscopy are used to assess the changes occurring at the atomic level. Finally, the impact of laser direct writing on nonlinear waveguide applications is discussed.
Show less - Date Issued
- 2004
- Identifier
- CFE0000236, ucf:46252
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000236
- Title
- FINITE ELEMENT METHOD MODELING OF ADVANCED ELECTRONIC DEVICES.
- Creator
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Chen, Yupeng, Wu, Thomas, University of Central Florida
- Abstract / Description
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In this dissertation, we use finite element method together with other numerical techniques to study advanced electron devices. We study the radiation properties in electron waveguide structure with multi-step discontinuities and soft wall lateral confinement. Radiation mechanism and conditions are examined by numerical simulation of dispersion relations and transport properties. The study of geometry variations shows its significant impact on the radiation intensity and direction. In...
Show moreIn this dissertation, we use finite element method together with other numerical techniques to study advanced electron devices. We study the radiation properties in electron waveguide structure with multi-step discontinuities and soft wall lateral confinement. Radiation mechanism and conditions are examined by numerical simulation of dispersion relations and transport properties. The study of geometry variations shows its significant impact on the radiation intensity and direction. In particular, the periodic corrugation structure exhibits strong directional radiation. This interesting feature may be useful to design a nano-scale transmitter, a communication device for future nano-scale system. Non-quasi-static effects in AC characteristics of carbon nanotube field-effect transistors are examined by solving a full time-dependent, open-boundary Schrödinger equation. The non-quasi-static characteristics, such as the finite channel charging time, and the dependence of small signal transconductance and gate capacitance on the frequency, are explored. The validity of the widely used quasi-static approximation is examined. The results show that the quasi-static approximation overestimates the transconductance and gate capacitance at high frequencies, but gives a more accurate value for the intrinsic cut-off frequency over a wide range of bias conditions. The influence of metal interconnect resistance on the performance of vertical and lateral power MOSFETs is studied. Vertical MOSFETs in a D2PAK and DirectFET package, and lateral MOSFETs in power IC and flip chip are investigated as the case studies. The impact of various layout patterns and material properties on RDS(on) will provide useful guidelines for practical vertical and lateral power MOSFETs design.
Show less - Date Issued
- 2006
- Identifier
- CFE0001389, ucf:46987
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001389
- Title
- Light-Matter Interactions of Plasmonic Nanostructures.
- Creator
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Reed, Jennifer, Zou, Shengli, Belfield, Kevin, Zhai, Lei, Hernandez, Eloy, Vanstryland, Eric, University of Central Florida
- Abstract / Description
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Light interaction with matter has long been an area of interest throughout history, spanning many fields of study. In recent decades, the investigation of light-matter interactions with nanostructures has become an intense area of research in the field of photonics. Metallic nanostructures, in particular, are of interest due to the interesting properties that arise when interacting with light. The properties are a result of the excitation of surface plasmons which are the collective...
Show moreLight interaction with matter has long been an area of interest throughout history, spanning many fields of study. In recent decades, the investigation of light-matter interactions with nanostructures has become an intense area of research in the field of photonics. Metallic nanostructures, in particular, are of interest due to the interesting properties that arise when interacting with light. The properties are a result of the excitation of surface plasmons which are the collective oscillation of the conduction electrons in the metal. Since the conduction electrons can be thought of as harmonic oscillators, they are quantized in a similar fashion. Just as a photon is a quantum of oscillations of an electromagnetic field, the plasmon is a quantum of electron oscillations of a metal. There are three types of plasmons:1. Bulk plasmons, also called volume plasmons, are longitudinal density fluctuations which propagate through a bulk metal with an eigenfrequency of ?_p called the plasma frequency.2. Localized surface plasmons are non-propagating excitations of the conduction electrons of a metallic nanoparticle coupled to an electromagnetic field. 3. Surface plasmon polaritons are evanescent, dispersive propagating electromagnetic waves formed by a coupled state between a photon and the excitation of the surface plasmons. They propagate along the surface of a metal-dielectric interface with a broad spectrum of eigenfrequencies from ?=0 to ?= ?_p??2. Plasmonics is a subfield of photonics which focuses on the study of surface plasmons and the optical properties that result from light interacting with metal films and nanostructures on the deep subwavelength scale. In this thesis, plasmonic nanostructures are investigated for optical waveguides and other nanophotonic applications through computational simulations primarily base on electrodynamic theory. The theory was formulated by several key figures and established by James Clerk Maxwell after he published a set of relations which describe all classical electromagnetic phenomena, known as Maxwell's equations. Using methods based on Maxwell's equations, the optical properties of metallic nanostructures utilizing surface plasmons is explored. In Chapter 3, light propagation of bright and dark modes of a partially and fully illuminated silver nanorod is investigated for waveguide applications. Then, the origin of the Fano resonance line shape in the scattering spectra of a silver nanorod is investigated. Next, in Chapter 4, the reflection and transmission of a multilayer silver film is simulated to observe the effects of varying the dielectric media between the layers on light propagation. Building on the multilayer film work, metal-insulator-metal waveguides are explored by perforating holes in the bottom layer of a two layer a silver film to investigate the limits of subwavelength light trapping, confinement, and propagation. Lastly, in Chapter 5, the effect of surface plasmons on the propagation direction of electromagnetic wave around a spherical silver nanoparticle which shows an effective negative index of refraction is examined. In addition, light manipulation using a film of silver prisms with an effective negative index of refraction is also investigated. The silver prisms demonstrate polarization selective propagation for waveguide and optical filter applications. These studies provide insight into plasmonic mechanisms utilized to overcome the diffraction limit of light. Through better understanding of how to manipulating light with plasmonic nanostructures, further advancements in nanophotonic technologies for applications such as extremely subwavelength waveguides, sensitive optical detection, optical filters, polarizers, beam splitters, optical data storage devices, high speed data transmission, and integrated subwavelength photonic circuits can be achieved.
Show less - Date Issued
- 2013
- Identifier
- CFE0005049, ucf:49964
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005049
- Title
- Engineering and Application of Ultrafast Laser Pulses and Filamentation in Air.
- Creator
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Barbieri, Nicholas, Richardson, Martin, University of Central Florida
- Abstract / Description
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Continuing advances in laser and photonic technology has seen the development of lasers with increasing power and increasingly short pulsewidths, which have become available over an increasing range of wavelengths. As the availability of laser sources grow, so do their applications. To make better use of this improving technology, understanding and controlling laser propagation in free space is critical, as is understanding the interaction between laser light and matter.The need to better...
Show moreContinuing advances in laser and photonic technology has seen the development of lasers with increasing power and increasingly short pulsewidths, which have become available over an increasing range of wavelengths. As the availability of laser sources grow, so do their applications. To make better use of this improving technology, understanding and controlling laser propagation in free space is critical, as is understanding the interaction between laser light and matter.The need to better control the light obtained from increasingly advanced laser sources leads to the emergence of beam engineering, the systematic understanding and control of light through refractive media and free space. Beam engineering enables control over the beam shape, energy and spectral composition during propagation, which can be achieved through a variety of means. In this dissertation, several methods of beam engineering are investigated. These methods enable improved control over the shape and propagation of laser light. Laser-matter interaction is also investigated, as it provides both a means to control the propagation of pulsed laser light through the atmosphere, and provides a means to generation remote sources of radiation.
Show less - Date Issued
- 2013
- Identifier
- CFE0004650, ucf:49881
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004650
