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Title: PLASMON ENHANCED NEAR-FIELD INTERACTIONS IN SURFACE COUPLED NANOPARTICLE ARRAYS FOR INTEGRATED NANOPHOTONIC DEVICES.
Creator: Ghoshal, Amitabh, Kik, Pieter, University of Central Florida
Abstract / Description: The current thrust towards developing silicon compatible integrated nanophotonic devices is driven by need to overcome critical challenges in electronic circuit technology related to information bandwidth and thermal management. Surface plasmon nanophotonics represents a hybrid technology at the interface of optics and electronics that could address several of the existing challenges. Surface plasmons are electronic charge density waves that can occur at a metal-dielectric interface at...
Show moreThe current thrust towards developing silicon compatible integrated nanophotonic devices is driven by need to overcome critical challenges in electronic circuit technology related to information bandwidth and thermal management. Surface plasmon nanophotonics represents a hybrid technology at the interface of optics and electronics that could address several of the existing challenges. Surface plasmons are electronic charge density waves that can occur at a metal-dielectric interface at optical and infrared frequencies. Numerous plasmon based integrated optical devices such as waveguides, splitters, resonators and multimode interference devices have been developed, however no standard integrated device for coupling light into nanoscale optical circuits exists. In this thesis we experimentally and theoretically investigate the excitation of propagating surface plasmons via resonant metal nanoparticle arrays placed in close proximity to a metal surface. It is shown that this approach can lead to compact plasmon excitation devices. Full-field electromagnetic simulations of the optical illumination of metal nanoparticle arrays near a metal film reveal the presence of individual nanoparticle resonances and collective grating-like resonances related to propagating surface plasmons within the periodic array structure. Strong near-field coupling between the nanoparticle and grating resonances is observed, and is successfully described by a coupled oscillator model. Numerical simulations of the effect of nanoparticle size and shape on the excitation and dissipation of surface plasmons reveal that the optimum particle volume for efficient surface plasmon excitation depends sensitively on the particle shape. This observation is quantitatively explained in terms of the shape-dependent optical cross-section of the nanoparticles. Reflection measurements on nanoparticle arrays fabricated using electron-beam lithography confirm the predicted particle-grating interaction. An unexpected polarization-dependent splitting of the film-mediated collective resonance is successfully attributed to the existence of out-of plane polarization modes of the metal nanoparticles. In order to distinguish between the excitation of propagating surface plasmons and localized nanoparticle plasmons, spectrally resolved leakage radiation measurements are presented. Based on these measurements, a universally applicable method for measuring the wavelength dependent efficiency of coupling free-space radiation into guided surface plasmon modes on thin films is developed. Finally, it is shown that the resonantly enhanced near-field coupling the nanoparticles and the propagating surface plasmons can lead to optimized coupler device dimensions well below 10 microns.
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Date Issued: 2010
Identifier: CFE0003091, ucf:48322
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003091

Title: GRATING COUPLER FOR SURFACE WAVES BASED ON ELECTRICAL DISPLACEMENT CURRENTS.
Creator: Brescia, Jonathan R, Peale, Robert, University of Central Florida
Abstract / Description: Bound electromagnetic surface waves can be excited by free-space waves on a corrugated conduction surface. These electromagnetic surface waves, called surface plasmon polaritons (SPPs), are coupled to a plasma of free charges, which travel together with the wave. We investigated the effect of separating metal corrugations from the smooth metal ground plane with a thin dielectric layer and show that SPPs can be excited via displacement currents. However, the SPP excitation resonances broaden...
Show moreBound electromagnetic surface waves can be excited by free-space waves on a corrugated conduction surface. These electromagnetic surface waves, called surface plasmon polaritons (SPPs), are coupled to a plasma of free charges, which travel together with the wave. We investigated the effect of separating metal corrugations from the smooth metal ground plane with a thin dielectric layer and show that SPPs can be excited via displacement currents. However, the SPP excitation resonances broaden and disappear as the dielectric thickness approaches 1% of the wavelength.
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Date Issued: 2019
Identifier: CFH2000457, ucf:45898
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000457

Title: Novel optical properties of metal nanostructures based on surface plasmons.
Creator: Wang, Haining, Zou, Shengli, Liao, Yi, Kolpashchikov, Dmitry, Gesquiere, Andre, Su, Ming, University of Central Florida
Abstract / Description: Surface plasmons have been attracted extensive interests in recent decades due to the novel properties in nanometer sized dimensions. My work focused on the novel optical properties of metal nanostructures based on surface plasmons using theoretical simulation methods. In the first part, we investigated metal nanofilms and nanorods and demonstrated that extremely low scattering efficiency, high absorption efficiency and propagation with long distance could be obtained by different metal...
Show moreSurface plasmons have been attracted extensive interests in recent decades due to the novel properties in nanometer sized dimensions. My work focused on the novel optical properties of metal nanostructures based on surface plasmons using theoretical simulation methods. In the first part, we investigated metal nanofilms and nanorods and demonstrated that extremely low scattering efficiency, high absorption efficiency and propagation with long distance could be obtained by different metal nanostructures. With a perforated silver film, we demonstrated that an extremely low scattering cross section with an efficiency of less than 1% can be achieved at tunable wavelengths with tunable widths. The resonance wavelength, width, and intensity are influenced by the shape, size and arrangement pattern of the holes, as well as the distance separating the holes along the polarization direction. The extremely low scattering could be used to obtain high absorption efficiency of a two-layer silver nanofilm. Using the discrete dipole approximation method, we achieved enhanced absorption efficiencies, which are close to 100%, at tunable wavelengths in a two-layer silver thin film. The film is composed of a 100 nm thick perforated layer facing the incident light and a 100 nm thick solid layer. Resonance wavelengths are determined by the distances between perforated holes in the first layer as well as the separation between two layers. The resonance wavelengths shift to red with increasing separation distance between two layers or the periodic distance of the hole arrays. Geometries of conical frustum shaped holes in the first layer are critical for the improved absorption efficiencies. When the hole bottom diameter equals the periodic distance and the upper diameter is about one-third of the bottom diameter, close to unit absorption efficiency can be obtained. We examined the electromagnetic wave propagation along a hollow silver nanorod with subwavelength dimensions. The calculations show that light may propagate along the hollow nanorod with growing intensities. The influences of the shape, dimension, and length of the rod on the resonance wavelength and the enhanced local electric field, |E|2, along the rod were investigated. In the second part, a generalized electrodynamics model is proposed to describe the enhancement and quenching of fluorescence signal of a dye molecule placed near a metal nanoparticle (NP). Both the size of the Au NPs and quantum yield of the dye molecule are crucial in determining the emission intensity of the molecule. Changing the size of the metal NP will alter the ratio of the scattering and absorption efficiencies of the metal NP and consequently result in different enhancement or quenching effect to the dye molecule. A dye molecule with a reduced quantum yield indicates that the non-radiative channel is dominant in the decay of the excited dye molecules and the amplification of the radiative decay rate will be easier. In general, the emission intensity will be quenched when the size of metal NP is small and the quantum yield of dye molecule is about unity. A significant enhancement factor will be obtained when the quantum yield of the molecule is small and the particle size is large. When the quantum yield of the dye molecule is less than 10-5, the model is simplified to the surface enhanced Raman scattering equation.
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Date Issued: 2013
Identifier: CFE0004769, ucf:49786
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004769

Title: TERAHERTZ AND SUB-TERAHERTZ TUNABLE RESONANT DETECTORS BASED ON EXCITATION OF TWO DIMENSIONAL PLASMONS IN InGaAs/InP HEMTs.
Creator: Nader Esfahani, Nima, Peale, Robert, Ishigami, Masa, Del Barco, Enrique, Buchwald, Walter, University of Central Florida
Abstract / Description: Plasmons can be generated in the two dimensional electron gas (2DEG) of grating-gated high electron mobility transistors (HEMTs). The grating-gate serves dual purposes, namely to provide the required wavevector to compensate for the momentum mismatch between the free-space radiation and 2D-plasmons, and to tune the 2DEG sheet charge density. Since the plasmon frequency at a given wavevector depends on the sheet charge density, a gate bias can shift the plasmon resonance. In some cases,...
Show morePlasmons can be generated in the two dimensional electron gas (2DEG) of grating-gated high electron mobility transistors (HEMTs). The grating-gate serves dual purposes, namely to provide the required wavevector to compensate for the momentum mismatch between the free-space radiation and 2D-plasmons, and to tune the 2DEG sheet charge density. Since the plasmon frequency at a given wavevector depends on the sheet charge density, a gate bias can shift the plasmon resonance. In some cases, plasmon generation results in a resonant change in channel conductance which allows a properly designed grating-gated HEMT to be used as a voltage-tunable resonant detector or filter. Such devices may find applications as chip-scale tunable detectors in airborne multispectral detection and target tracking.Reported here are investigations of InGaAs/InP-based HEMT devices for potential tunable resonant sub-THz and THz detectors. The HEMTs were fabricated from a commercial double-quantum well HEMT wafer by depositing source, drain, and semi-transparent gate contacts using standard photolithography processes. Devices were fabricated with metalized transmission gratings with multiple periods and duty cycles. For sub-THz devices, grating period and duty cycle were chosen to be 9 ?m and 22%, respectively; while they were chosen to be 0.5 ?m and 80% for the THz device. The gratings were fabricated on top of the gate region with dimensions of 250 ?m (&)#215; 195 ?m.The resonant photoresponse of the larger grating-period HEMT was investigated in the sub-THz frequency range of around 100 GHz. The free space radiation was generated by an ultra-stable Backward Wave Oscillator (BWO) and utilized in either frequency modulation (FM), or amplitude modulation (AM) experiments. The photoresponse was measured at 4K sample temperature as the voltage drop across a load resistor connected to the drain while constant source-drain voltages of different values, VSD, were applied. The dependence of such optoelectrical effect to polarization of the incident light, and applied VSD is studied. The results of AM and FM measurements are compared and found to be in agreement with the calculations of the 2D-plasmon absorption theory, however, a nonlinear behavior is observed in the amplitude and the line-shape of the photoresponse for AM experiments. For detection application, the minimum noise-equivalent-power (NEP) of the detector was determined to be 235 and 113 pW/Hz1/2 for FM and AM experiments, respectively. The maximum responsivity of the detector was also estimated to be ~ 200 V/W for the two experiments. The far-IR transmission spectra of the device with nanometer scale period was measured at 4 K sample temperature for different applied gate voltages to investigate the excitation of 2D-plasmon modes. Such plasmon resonances were observed, but their gate bias dependence agreed poorly with expectations.
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Date Issued: 2014
Identifier: CFE0005386, ucf:50461
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005386

Title: Mid-infrared plasmonics.
Creator: Khalilzadeh Rezaie, Farnood, Peale, Robert, Ishigami, Masa, Schoenfeld, Winston, Buchwald, Walter, Abdolvand, Reza, University of Central Florida
Abstract / Description: This dissertation reports investigations into materials for, and applications of, infrared surface plasmon polaritons (SPP). SPPs are inhomogeneous electromagnetic waves that are bound to the surface of a conductor. Tight confinement of electromagnetic energy, the primary virtue of SPPs for so-called (")plasmonic(") applications, requires plasma frequencies for the conductor near the intended infrared operational frequencies. This requires carrier concentrations that are much less than those...
Show moreThis dissertation reports investigations into materials for, and applications of, infrared surface plasmon polaritons (SPP). SPPs are inhomogeneous electromagnetic waves that are bound to the surface of a conductor. Tight confinement of electromagnetic energy, the primary virtue of SPPs for so-called (")plasmonic(") applications, requires plasma frequencies for the conductor near the intended infrared operational frequencies. This requires carrier concentrations that are much less than those of usual metals such as gold and silver. I have investigated the optical properties and SPP excitation resonances of two materials having infrared plasma frequencies, namely the semimetal bismuth and the transparent conducting fluorine-doped tin-oxide (FTO). The complex permittivity spectra for evaporated films of Bi were found to be distinctly different than earlier reports for crystal or polycrystalline films, and SPP excitation resonances on Bi-coated gratings were found to be disappointingly broad. Permittivity spectra for chemical spray deposited FTO were obtained to long-wave IR wavelengths for the first time, and nano-crystalline FTO-coated silicon lamellar gratings show remarkable conformity. SPP excitation resonances for FTO are more promising than for Bi. Thus, FTO appears to be a promising SPP host for infrared plasmonics, e.g. a planer waveguide plasmonic spectral sensor, whose design was elaborated and investigated as part of my research and which requires SPP-host coating on deep vertical side walls of a trench-like analyte interaction region. Additionally, FTO may serve as a useful conducting oxide for a near-IR plasmonic spectral imager that I have investigated theoretically.
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Date Issued: 2015
Identifier: CFE0006222, ucf:51080
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006222

Title: SURFACE PLASMON HOSTS FOR INFRARED WAVEGUIDES AND BIOSENSORS, AND PLASMONS IN GOLD-BLACK NANO-STRUCTURED FILMS.
Creator: 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 Ã‚Âµm 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 Ã‚Âµm 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 Ã‚Âµm 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 Ã‚Âµm. 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 Ã‚Âµm 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.
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Date Issued: 2010
Identifier: CFE0003231, ucf:48547
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003231

Title: GOLD NANOPARTICLE GENERATION USING IN SITU REDUCTION ON A PHOTORESIST POLYMER SUBSTRATE.
Creator: Clukay, Christopher, Kuebler, Stephen, University of Central Florida
Abstract / Description: This report presents evidence that in-situ reduction of metal ions bound to a cross-linked polymer surface does not always result in nanoparticle formation solely at the interface, as is commonly assumed, but also as much as 40 nm deep within the polymer matrix. Tetrachloroaurate ions were bound using a variety of multi-functional amines to cured films of SU-8 -- a cross-linkable epoxide frequently used for micro- and nanofabrication -- and then treated using one of several reducing agents....
Show moreThis report presents evidence that in-situ reduction of metal ions bound to a cross-linked polymer surface does not always result in nanoparticle formation solely at the interface, as is commonly assumed, but also as much as 40 nm deep within the polymer matrix. Tetrachloroaurate ions were bound using a variety of multi-functional amines to cured films of SU-8 -- a cross-linkable epoxide frequently used for micro- and nanofabrication -- and then treated using one of several reducing agents. The resulting gold-nanoparticle decorated films were examined by X-ray photoelectron spectroscopy and by plan-view and cross-sectional transmission electron microscopy. Reduction using sodium borohydride or sodium citrate generates bands of interspersed particles as much as 40 nm deep within the polymer, suggesting both the Au(III) complex and the reducing agent are capable of penetrating the surface and affecting reduction and formation of nanoparticles within the polymer matrix. It is shown that nanoparticle formation can be confined nearer to the polymer interface by using hydroquinone, a sterically bulkier and less flexible reducing agent, or by reacting the surface in aqueous media with high molecular-weight multifunctional amines, that presumably confine Au(III) nearer to the true interface. These finding have important implications for technologies that apply surface bound nanoparticles, including electroless metallization, catalysis, nano-structure synthesis, and surface enhanced spectroscopy.
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Date Issued: 2011
Identifier: CFH0004091, ucf:44794
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004091

Title: Dynamically Tunable Plasmonic Structural Color.
Creator: Franklin, Daniel, Chanda, Debashis, Peale, Robert, Leuenberger, Michael, Wu, Shintson, University of Central Florida
Abstract / Description: Functional surfaces which can control light across the electromagnetic spectrum are highly desirable. With the aid of advanced modeling and fabrication techniques, researchers have demonstrated surfaces with near arbitrary tailoring of reflected/transmitted amplitude, phase and polarization - the applications for which are diverse as light itself. These systems often comprise of structured metals and dielectrics that, when combined, manifest resonances dependent on structural dimensions. This...
Show moreFunctional surfaces which can control light across the electromagnetic spectrum are highly desirable. With the aid of advanced modeling and fabrication techniques, researchers have demonstrated surfaces with near arbitrary tailoring of reflected/transmitted amplitude, phase and polarization - the applications for which are diverse as light itself. These systems often comprise of structured metals and dielectrics that, when combined, manifest resonances dependent on structural dimensions. This attribute provides a convenient and direct path to arbitrarily engineer the surface's optical characteristics across many electromagnetic regimes. But while many of these plasmonic systems struggle to compete with the efficiency of pre-existing technologies, the ability to tune plamsonic structures post-fabrication is a distinct advantage which may lead to novel devices. In this work, I will summarize fundamental and applied aspects of tunable plasmonic systems as applied to the visible and infrared regimes. I will demonstrate how liquid crystal may be used to dynamically and reversibly tune the plasmonic resonances of metallic surfaces on a millisecond time scale. For the visible, this results in dynamic color-changing surfaces capable of covering the entire RGB color space and which is compatible with active addressing schemes. I will then show the application of these concepts to infrared absorbers through the use of liquid crystal and phase change materials. The later of these devices can find use in infrared data/image encoding, thermal management and camouflage. Together, these works explore the limits of tunable plasmonic systems and the novel devices they might lead to.
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Date Issued: 2018
Identifier: CFE0007001, ucf:52052
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007001

Title: Far-infrared bands in plasmonic metal-insulator-metal absorbers optimized for long wave infrared.
Creator: Evans, Rachel, Peale, Robert, Ishigami, Masahiro, Lyakh, Arkadiy, University of Central Florida
Abstract / Description: Metal(-)insulator(-)metal (MIM) resonant absorbers comprise a conducting ground plane, a thin dielectric, and thin separated metal top-surface structures. Long-wave infrared (LWIR) fundamental absorptions are experimentally shown to be optimized for a ratio of dielectric thickness to top-structure dimension t/l (>) 0.08. The fundamental resonance wavelength is predicted by different analytic standing-wave theories to be ~2nl, where n is the dielectric refractive index. Thus, for the...
Show moreMetal(-)insulator(-)metal (MIM) resonant absorbers comprise a conducting ground plane, a thin dielectric, and thin separated metal top-surface structures. Long-wave infrared (LWIR) fundamental absorptions are experimentally shown to be optimized for a ratio of dielectric thickness to top-structure dimension t/l (>) 0.08. The fundamental resonance wavelength is predicted by different analytic standing-wave theories to be ~2nl, where n is the dielectric refractive index. Thus, for the dielectrics SiO2, AlN, and TiO2, l values of a few microns give fundamentals in the 8-12 micron LWIR wavelength region. Agreement of observed fundamental resonance wavelength with theory is better for t/l (>) ~0.2. Harmonics at shorter wavelengths are always observed, but we show that there are additional resonances in the far-infrared 20-50 micron wavelength range, well beyond the predicted fundamental. These appear to be due to dispersion. They may impact selectivity in spectral sensing applications.
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Date Issued: 2018
Identifier: CFE0007176, ucf:52267
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007176

Title: INFRARED SURFACE PLASMON POLARITONS ON SEMICONDUCTOR, SEMIMETAL AND CONDUCTING POLYMER.
Creator: Shahzad, Monas, Peale, Robert, Heinrich, Helge, Coffey, Kevin, Diaz, Diego, University of Central Florida
Abstract / Description: Conductors with IR (infrared) plasma frequencies are potentially useful hosts of surface plasmon polaritons (SPPs) with subwavelength mode confinement for sensing applications. The underlying aim of this work is to identify such conductors that also have sharp SPP excitation resonances for biosensor applications at infrared (3-11 ?m) wavelengths, where biological analytes are strongly differentiated by their IR absorption spectra. In this work, various materials were investigated such as a...
Show moreConductors with IR (infrared) plasma frequencies are potentially useful hosts of surface plasmon polaritons (SPPs) with subwavelength mode confinement for sensing applications. The underlying aim of this work is to identify such conductors that also have sharp SPP excitation resonances for biosensor applications at infrared (3-11 ?m) wavelengths, where biological analytes are strongly differentiated by their IR absorption spectra. In this work, various materials were investigated such as a heavily doped semiconductor, a semimetal, a conducting polymer and its composite.Heavily doped silicon was investigated by tuning its plasma frequency to the infrared region by heavily doping. The measured complex permittivity spectra for p-type silicon with a carrier concentration of 6 (&)#215; 1019 and 6 (&)#215; 1020 cm-3 show that these materials support SPPs beyond 11 and 6 ?m wavelengths, respectively. SPP generation was observed in angular reflection spectra of doped-silicon gratings. Photon-to-plasmon coupling resonances, a necessary condition for sensing, were demonstrated near 10 ?m wavelength for the heaviest doped, and the observed resonances were confirmed theoretically using analytic calculations. The permittivity spectra were also used to calculate SPP mode heights above the silicon surface and SPP propagation lengths. Reasonable merit criteria applied to these quantities suggest that only the heaviest doped material has sensor potential, and then mainly within the wavelength range of 6 to 10 ?m. The semimetal bismuth (Bi) has an infrared plasmon frequency less than the infrared plasma frequency of noble metals such as gold and silver, which is one order of magnitude lower than their plasma frequencies. The excitation of IR surface plasmons on Bi lamellar gratings in the wavelength range of 3.4 (&)#181;m to 10.6 (&)#181;m was observed. Distinct SPP resonances were observed although the usual condition for bound SPP is not satisfied in this wavelength range because the real part of the permittivity is positive. The excitation of these resonances agrees theoretically with the electromagnetic surface waves called surface polaritons (SPs). The measured permittivity spectra were used to calculate the SP mode heights above the bismuth surface and SP propagation length, which satisfied our criteria for sensors.A conducting polymer and its composite with graphite were also investigated since their plasma frequency may lie in the infrared region. Polyaniline was chemically synthesized and doped with various acids to prepare its salt form. A composite material of polyaniline with colloidal and nano-graphite was also prepared. Optical constants were measured in the long wave infrared region (LWIR) and were used to calculate SPP propagation length and penetration depth. SPP resonance spectra were calculated and suggested that polyaniline and its composite can be used as a host with sufficient mode confinement for IR sensor application.
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Date Issued: 2012
Identifier: CFE0004598, ucf:49215
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004598

Title: Synthesis and Characterization of Antimicrobial Non-Color Forming Silica-Silver Nanocomposite.
Creator: Bazata, Joshua, Santra, Swadeshmukul, Moore, Sean, Jewett, Travis, University of Central Florida
Abstract / Description: Silver has been utilized for its antimicrobial properties for thousands of years in a variety of fields, extending the shelf life of food and water, rendering eating utensils sanitary, and more recently in biomedical applications such as silver based antiseptic creams. While effective as an antimicrobial agent at very low concentrations ((&)#181;g/mL), silver imparts a strong color to objects it is incorporated into, due to its high plasmonic efficiency. The goal of this study was to...
Show moreSilver has been utilized for its antimicrobial properties for thousands of years in a variety of fields, extending the shelf life of food and water, rendering eating utensils sanitary, and more recently in biomedical applications such as silver based antiseptic creams. While effective as an antimicrobial agent at very low concentrations ((&)#181;g/mL), silver imparts a strong color to objects it is incorporated into, due to its high plasmonic efficiency. The goal of this study was to determine if incorporating silver nanoparticles into a silica matrix could reduce or eliminate the plasmonic signal, while retaining the antimicrobial effects of the silver nanoparticles.Citrate capped silver nanoparticles (AgNP) were synthesized using a borohydride reduction method as outlined by Zheng et. al., and incorporated into silica nanoparticles using a method adapted from Fleger et. al. To test the antimicrobial efficacy of these synthesized silica coated silver nanoparticles (SiAgNP), minimum inhibitory concentration testing at three time points, 1, 4, and 8 hours, was carried out against E. coli and S. aureus using broth microdilution and Alamar Blue as an indicator of microbial growth. Efficacy was judged against uncoated AgNP and aqueous silver nitrate (AgNO3) solutions at equivalent Ag concentrations. Silica nanoparticles (SiNP) were utilized as a negative control. Further antimicrobial characterization using a bacterial viability assay revealed a time dependent killing trend in the SiAgNP, suggesting a controlled release of Ag+ from within the silica matrix. Efficacy of the SiAgNP was determined to fall between the most effective antimicrobial form of silver tested, AgNO3, and least effective, AgNP. However, the SiAgNP material exhibited no visible plasmon peak when UV-Visible spectrophotometric readings were taken, as well as remaining colorless when coated onto a ceramic substrate. Zeta potential revealed a high degree of colloidal stability of the SiAgNP. TEM imaging studies were carried out, verifying the presence of Ag within and on the silica nanoparticles, as well as the crystalline structure of the uncoated AgNP. It was determined that coating AgNP synthesized through borohydride reduction with silica through a St(&)#246;ber synthesis mechanism yields a material with enhanced antimicrobial effects compared to AgNP, but with no detectable plasmon signal, effectively producing a non-color forming silver based antimicrobial.
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Date Issued: 2015
Identifier: CFE0006208, ucf:51097
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006208

Title: The cytopathic activity of cholera toxin requires a threshold quantity of cytosolic toxin.
Creator: Bader, Carly, Teter, Kenneth, Zervos, Antonis, Jewett, Travis, Tatulian, Suren, University of Central Florida
Abstract / Description: Cholera toxin (CT), secreted from Vibrio cholerae, causes a massive fluid and electrolyte efflux in the small intestine that results in life-threatening diarrhea and dehydration which impacts 3-5 million people per year. CT is secreted into the intestinal lumen but acts within the cytosol of intestinal epithelial cells. CT is an AB5 toxin that has a catalytic A1 subunit and a cell binding B subunit. CT moves from the cell surface to the endoplasmic reticulum (ER) by retrograde transport. Much...
Show moreCholera toxin (CT), secreted from Vibrio cholerae, causes a massive fluid and electrolyte efflux in the small intestine that results in life-threatening diarrhea and dehydration which impacts 3-5 million people per year. CT is secreted into the intestinal lumen but acts within the cytosol of intestinal epithelial cells. CT is an AB5 toxin that has a catalytic A1 subunit and a cell binding B subunit. CT moves from the cell surface to the endoplasmic reticulum (ER) by retrograde transport. Much of the toxin is transported to the lysosomes for degradation, but a secondary pool of toxin is diverted to the Golgi apparatus and then to the ER. Here the A1 subunit detaches from the rest of the toxin and enters the cytosol. The disordered conformation of free CTA1 facilitates toxin export to the cytosol by activating a quality control mechanism known as ER-associated degradation. The return to a folded structure in the cytosol allows CTA1 to attain an active conformation for modification of its Gs? target through ADP-ribosylation. This modification locks the protein in an active state which stimulates adenylate cyclase and leads to elevated levels of cAMP. A chloride channel located in the apical enterocyte membrane opens in response to signaling events induced by these elevated cAMP levels. The osmotic movement of water into the intestinal lumen that results from the chloride efflux produces the characteristic profuse watery diarrhea that is seen in intoxicated individuals.The current model of intoxication proposes only one molecule of cytosolic toxin is required to affect host cells, making therapeutic treatment nearly impossible. However, based on emerging evidence, we hypothesize a threshold quantity of toxin must be present within the cytosol of the target cell in order to elicit a cytopathic effect. Using the method of surface plasmon resonance along with toxicity assays, I have, for the first time, directly measured the efficiency of toxin delivery to the cytosol and correlated the levels of cytosolic toxin to toxin activity. I have shown CTA1 delivery from the cell surface to the cytosol is an inefficient process with only 2.3 % of the surface bound CTA1 appearing in the cytosol after 2 hours of intoxication. I have also determined and a cytosolic quantity of more than approximately .05ng of cytosolic CTA1 must be reached in order to elicit a cytopathic effect. Furthermore, CTA1 must be continually delivered from the cell surface to the cytosol in order to overcome the constant proteasome-mediated clearance of cytosolic toxin. When toxin delivery to the cytosol was blocked, this allowed the host cell to de-activate Gs?, lower cAMP levels, and recover from intoxication. Our work thus indicates it is possible to treat cholera even after the onset of disease. These findings challenge the idea of irreversible cellular toxicity and open the possibility of post-intoxication treatment options.
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Date Issued: 2013
Identifier: CFE0004810, ucf:49759
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004810

Title: Cascaded plasmon resonances for enhanced nonlinear optical response.
Creator: Toroghi, Seyfollah, Kik, Pieter, Vanstryland, Eric, Kuebler, Stephen, Hagan, David, Belfield, Kevin, University of Central Florida
Abstract / Description: The continued development of integrated photonic devices requires low-power, small volume all-optical modulators. The weak nonlinear optical response of conventional optical materials requires the use of high intensities and large interaction volumes in order to achieve significant light modulation, hindering the miniaturization of all-optical switches and the development of lightweight transmission optics with nonlinear optical response. These challenges may be addressed using plasmonic...
Show moreThe continued development of integrated photonic devices requires low-power, small volume all-optical modulators. The weak nonlinear optical response of conventional optical materials requires the use of high intensities and large interaction volumes in order to achieve significant light modulation, hindering the miniaturization of all-optical switches and the development of lightweight transmission optics with nonlinear optical response. These challenges may be addressed using plasmonic nanostructures due to their unique ability to confine and enhance electric fields in sub-wavelength volumes. The ultrafast nonlinear response of free electrons in such plasmonic structures and the fast thermal nonlinear optical response of metal nanoparticles, as well as the plasmon enhanced nonlinear Kerr-type response of the host material surrounding the nanostructures could allow ultrafast all-optical modulation with low modulation energy. In this thesis, we investigate the linear and nonlinear optical response of engineered effective media containing coupled metallic nanoparticles. The fundamental interactions in systems containing coupled nanoparticles with size, shape, and composition dissimilarity, are evaluated analytically and numerically, and it is demonstrated that under certain conditions the achieved field enhancement factors can exceed the single-particle result by orders of magnitude in a process called cascaded plasmon resonance. It is demonstrated that these conditions can be met in systems containing coupled nanospheres, and in systems containing non-spherical metal nanoparticles that are compatible with common top-down nanofabrication methods such as electron beam lithography and nano-imprint lithography. We show that metamaterials based on such cascaded plasmon resonance structures can produce enhanced nonlinear optical refraction and absorption compared to that of conventional plasmonic nanostructures. Finally, it is demonstrated that the thermal nonlinear optical response of metal nanoparticles can be enhanced in carefully engineered heterogeneous nanoparticle clusters, potentially enabling strong and fast thermal nonlinear optical response in system that can be produced in bulk through chemical synthesis.
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Date Issued: 2014
Identifier: CFE0005556, ucf:50272
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005556

Title: The effect of electron-hole pairs in semiconductor and topological insulator nanostructures on plasmon resonances and photon polarizations.
Creator: Paudel, Hari, Leuenberger, Michael, Rahman, Talat, Saha, Haripada, Gesquiere, Andre, University of Central Florida
Abstract / Description: The generation of electron-hole pairs in materials has great importance. In directbandgap semiconductor materials, the mechanism of radiative recombination of electron-holepairs leads to the emission of photons, which is the basis of Light Emitting Diodes(LEDs). The excitation of electron-hole pairs by absorption of photons is the active processin photodiodes, solar cells, and other semiconductor photodetector devices. In optoelectronicdevices such as optical switches which are based on...
Show moreThe generation of electron-hole pairs in materials has great importance. In directbandgap semiconductor materials, the mechanism of radiative recombination of electron-holepairs leads to the emission of photons, which is the basis of Light Emitting Diodes(LEDs). The excitation of electron-hole pairs by absorption of photons is the active processin photodiodes, solar cells, and other semiconductor photodetector devices. In optoelectronicdevices such as optical switches which are based on transmission and reflection of the photons,electron-hole pairs excitation is a key for the device performance. Diodes and transistorsare also great discoveries in electronics which rely on the generation and recombination ofelectron-hole pairs at p-n junctions. In three-dimensional topological insulators (3D TIs)materials nanostructures excitation of electron-hole pairs can be utilized for the quantummemory, quantum information and quantum teleportation. In two-dimensional (2D) layeredmaterials like graphene, MoS_2, MoSe_2, WS_2 and WSe_2 generation and recombination ofelectron hole pairs is main process at p-n junctions, infrared detectors and sensors.This PhD thesis is concerned with the physics of different types of electron-hole pairsin various materials, such as wide-bandgap semiconductors, 3D topological insulators, andplasmonic excitations in metallic nanostructures. The materials of interest are wide bandgap semiconductors such as TiO_2 , 3D TIs such as Pb_1?xSn_xTe and the 2D layered materials such as MoS_2 and MoO_3. We study the electronic and optical properties in bulk and nanostructures and find applications in the area of semiclassical and quantum information processing. One of the interesting applications we focus in this thesis is shift in surface plasmon resonance due to reduction in index of refraction of surrounding dielectric environment which inturns shifts the wavelength of surface plasmon resonance up to 125 nm for carrier density of10^22/cm^3. Employing this effect, we present a model of a light controlled plasmon switching using a hybrid metal-dielectric heterostructures.In 3D TIs nanostructures, the time reversible spin partners in the valence and conductionband can be coupled by a left and a right handed circular polarization of the light.Such coupling of light with electron-hole pair polarization provides an unique opportunityto utilize 3D TIs in quantum information processing and spintronics devices. We present a model of a 3D TI quantum dot made of spherical core-bulk heterostructure. When a 3D TI QD is embedded inside a cavity, the single-photon Faraday rotation provides the possibility to implement optically mediated quantum teleportation and quantum information processing with 3D TI QDs, where the qubit is defined by either an electron-hole pair, a single electron spin, or a single hole spin in a 3D TI QD.Due to excellent transport properties in single and multiple layers of 2D layeredmaterials, several efforts have demonstrated the possibility to engineer electronic and optoelectronic devices based on MoS_2. In this thesis, we focus on theoretical and experimental study of electrical property and photoluminescence tuning, both in a single-layer of MoS_2.We present theoretical analysis of experimental results from the point of view of stability of MoO_3 defects in MoS_2 single layer and bandstructures calculation. In experiment, the electrical property of a single layer of MoS_2 can be tuned from semiconducting to insulating regime via controlled exposure to oxygen plasma. The quenching of photoluminescence of asingle sheet of MoS_2 has also been observed upon exposure to oxygen plasmas. We calculatethe direct to indirect band gap transitions by going from MoS_2 single sheet to MoO_3 singlesheet during the plasma exposure, which is due to the formation of MoO_3 rich defect domainsinside a MoS_2 sheet.
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Date Issued: 2014
Identifier: CFE0005397, ucf:50454
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005397

Title: Light-Matter Interactions of Plasmonic Nanostructures.
Creator: Reed, Jennifer, Zou, Shengli, Belfield, Kevin, Zhai, Lei, Hernandez, Eloy, Vanstryland, Eric, University of Central Florida
Abstract / Description: 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.
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Date Issued: 2013
Identifier: CFE0005049, ucf:49964
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005049

Title: Optical and Magnetic properties of nanostructures.
Creator: Nayyar, Neha, Rahman, Talat, Stolbov, Sergey, Ishigami, Marsahir, Hernandez, Florencio, University of Central Florida
Abstract / Description: In this thesis, Density Functional Theory and Time-Dependent Density-Functional Theory approaches are applied to study the optical and magnetic properties of several types of nanostructures. In studies of the optical properties we mainly focused on the plasmonic and excitonic effects in pure and transition metal-doped noble metal nanochains and their conglomerates. In the case of pure noble metal chains, it was found that the (collective) plasmon mode is pronounceable when the number of atoms...
Show moreIn this thesis, Density Functional Theory and Time-Dependent Density-Functional Theory approaches are applied to study the optical and magnetic properties of several types of nanostructures. In studies of the optical properties we mainly focused on the plasmonic and excitonic effects in pure and transition metal-doped noble metal nanochains and their conglomerates. In the case of pure noble metal chains, it was found that the (collective) plasmon mode is pronounceable when the number of atoms in the chain is larger than 5. The plasmon energy decreases with further with increasing number of atoms (N) and is almost N-independent when N is larger than 20. In the case of coupled pure chains it was found that the plasmon energy grows as square root of the number of chains, and reaches the visible light energy 1.8eV for the case of three parallel chains. Doping of pure Au chains with transition-metal atoms leads in many cases to formation of additional plasmon peaks close in energy to the undoped chain peak. This peak comes from the local charge oscillations around the potential minima created by the impurity atom. The effect is especially pronounced for Ni-doped chains. In the multiple-chain case, we find an unusual hybridization of the two different (local and collective) plasmon modes. Changing the chain size and chemical composition in the array can be used to tune the absorption properties of nanochains. The case of coupled finite (plasmonic) and infinite (semiconductor, excitonic) chains was also analyzed. We find that one can get significant exciton-plasmon coupling, including hybridized modes and energy transfer between these excitations, in the case of doped chains. The impurity atoms are found to work as attraction centers for excitons. This can be used to transform the exciton energy into local plasmon oscillations with consequent emission at desired point (at which the impurity is located). In a related study the optical properties of single layer MoS2 was analyzed with a focus on the possibility of ultrafast emission, In particular, it was found that the system can emit in femto-second regime under ultrafast laser pulse excitations. Finally, we have studied the magnetic properties of FeRh nanostructures to probe whether there is an antiferromagnetic to ferromagnetic transition as a function of the ratio of Fe and Rh atoms, as in the bulk alloy.. Surprisingly, the ferromagnetic phase is found to be much more stable for these nanostructures as compared to the bulk, which suggests that band-type effects may be responsible for this transition in the bulk, i.e. the transition cannot be described in terms of modification of the Heisenberg model parameters.
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Date Issued: 2014
Identifier: CFE0005221, ucf:50650
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005221

Title: Nanoplasmonics In Two-dimensional Dirac and Three-dimensional Metallic Nanostructure Systems.
Creator: Safaei, Alireza, Chanda, Debashis, Leuenberger, Michael, Mucciolo, Eduardo, Tetard, Laurene, Zhai, Lei, University of Central Florida
Abstract / Description: Surface plasmons are collective oscillation of electrons which are coupled to the incident electric field. Excitation of surface plasmon is a route to engineer the behavior of light in nanometer length scale and amplifying the light-matter interaction. This interaction is an outcome of near-field enhancement close to the metal surface which leads to plasmon damping through radiative decay to outgoing photons and nonradiative decay inside and on the surface of the material to create an...
Show moreSurface plasmons are collective oscillation of electrons which are coupled to the incident electric field. Excitation of surface plasmon is a route to engineer the behavior of light in nanometer length scale and amplifying the light-matter interaction. This interaction is an outcome of near-field enhancement close to the metal surface which leads to plasmon damping through radiative decay to outgoing photons and nonradiative decay inside and on the surface of the material to create an electron-hole pair via interband or intraband Landau damping. Plasmonics in Dirac systems such as graphene show novel features due to massless electrons and holes around the Dirac cones. Linear band structure of Dirac materials in the low-momentum limit gives rise to the unprecedented optical and electrical properties. Electronical tunability of the plasmon resonance frequency through applying a gate voltage, highly confined electric field, and low plasmon damping are the other special propoerties of the Dirac plasmons. In this work, I will summarize the theoretical and experimental aspects of the electrostatical tunable systems made from monolayer graphene working in mid-infrared regime. I will demonstrate how a cavity-coupled nanopatterned graphene excites Dirac plasmons and enhances the light-matter interaction. The resonance frequency of the Dirac plasmons is tunable by applying a gate voltage. I will show how different gate-dielectrics, and the external conditions like the polarization and angle of incident light affect on the optical response of the nanostructure systems. I will then show the application of these nanodevices in infrared detection at room temperature by using plasmon-assisted hot carriers generation. An asymmetric nanopatterned graphene shows a high responsivity at room temperature which is unprecedented. At the end, I will demonstrate the properties of surface plasmons on 3D noble metals and its applications in light-funneling, photodetection, and light-focusing.
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Date Issued: 2019
Identifier: CFE0007904, ucf:52746
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007904

Title: Nanoscale Control of Gap-plasmon Enhanced Optical Processes.
Creator: Lumdee, Chatdanai, Kik, Pieter, Dogariu, Aristide, Kuebler, Stephen, Huo, Qun, University of Central Florida
Abstract / Description: Surface plasmon resonances of metal nanostructures have been studied intensely in recent years. The strong plasmon-mediated electric field enhancement and field confinement well beyond the diffraction limit has been demonstrated to improve the performance of optical devices including ultrasensitive sensors, light emitters, and optical absorbers. A plasmon resonance mode of particular recent interest is the gap plasmon resonance that occurs on closely spaced metallic structures. In contrast to...
Show moreSurface plasmon resonances of metal nanostructures have been studied intensely in recent years. The strong plasmon-mediated electric field enhancement and field confinement well beyond the diffraction limit has been demonstrated to improve the performance of optical devices including ultrasensitive sensors, light emitters, and optical absorbers. A plasmon resonance mode of particular recent interest is the gap plasmon resonance that occurs on closely spaced metallic structures. In contrast to plasmon resonances supported by isolated metal nanostructures, coupled nanostructures provide additional spectral and spatial control over the plasmon resonance response. For example, the resonance frequencies of metal nanoparticle dimers depend strongly on the gap size between the nanoparticles. Gap plasmons can produce local electric field enhancement factors that are several orders of magnitude stronger and more confined than surface plasmon resonances of isolated plasmonic nanospheres. The reliance of gap plasmons on few-nanometer separation between nanostructures makes it difficult to prepare gap-plasmon supporting structures with predictable resonance frequency and field enhancement. A structure that avoids this challenge is the film-coupled nanoparticle (NP). Similar to nanoparticle dimers, a nanoparticle on a supporting metallic film (or NP-on-a-mirror) can offer a strong coupling between the particle and its local environment, in this case the supporting film instead of adjacent nanoparticles, enabling strongly confined gap-plasmon modes. The NP-on-a-mirror geometry has been shown to produce reproducible gap plasmon resonances in a chemically and thermally robust, easy to fabricate structure. In this Thesis, we first present a scheme for controlling the gap plasmon resonance frequency of single gold nanoparticles using aluminum oxide coated metal films. We demonstrate experimentally and numerically that the gap-plasmon resonance of single gold nanoparticles can be tuned throughout the visible range by controlling the aluminum oxide thickness via anodization. In a separate study of Au NP on Al2O3 coated gold films it is shown that the oxide coating improves the stability of the structure under intense laser irradiation. An combined experimental and numerical analysis of the spectral response of Au NP on rough Au films shows that a film roughness of a few nanometer can affect the gap plasmon resonance in the absence of an oxide spacer layer. A photoluminescence study of single gold nanoparticles on an Al2O3 coated gold film shows that the gap-plasmon resonance of this type of plasmonic structure can increase gold photoluminescence by more than four orders of magnitude. Related numerical simulations reveal that the local photoluminescence enhancement of a gold nanoparticle on an Al2O3 coated gold film can be as high as one million near the particle-film junction. Finally, a new plasmonic sensing element was proposed based on our findings in the previous chapters. This proposed hole-in-one structure offers several attractive features including an easily optically accessible gap plasmon mode, while maintaining a relatively simple fabrication method. Taken together, the research presented in this Thesis demonstrates how the resonance frequency, field enhancement, mode polarization, structural stability, and structure reliability can be controlled at the nanoscale. The knowledge gained in the course of this work could lead to further development of nanophotonic devices that utilize extremely confined optical fields and precisely controlled resonance frequencies.
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Date Issued: 2015
Identifier: CFE0005972, ucf:50772
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005972

Title: INTEGRATED OPTICAL SPR (SURFACE PLASMON RESONANCE) SENSOR BASED ON OPTOELECTRONIC PLATFORM.
Creator: Bang, Hyungseok, LiKamWa, Patrick, University of Central Florida
Abstract / Description: Current major demands in SPR sensor development are system miniaturization and throughput improvement. Structuring an array of integrated optical SPR sensor heads on a semiconductor based optoelectronic platform could be a promising solution for those issues, since integrated optical waveguides have highly miniaturized dimension and the optoelectronic platform enables on-chip optical-to-electrical signal conversion. Utilizing a semiconductor based platform to achieve optoelectronic...
Show moreCurrent major demands in SPR sensor development are system miniaturization and throughput improvement. Structuring an array of integrated optical SPR sensor heads on a semiconductor based optoelectronic platform could be a promising solution for those issues, since integrated optical waveguides have highly miniaturized dimension and the optoelectronic platform enables on-chip optical-to-electrical signal conversion. Utilizing a semiconductor based platform to achieve optoelectronic functionality poses requirements to the senor head; the sensor head needs to have reasonably small size while it should have reasonable sensitivity and fabrication tolerance. This research proposes a novel type of SPR sensor head and demonstrates a fabricated device with an array of integrated optical SPR sensor heads endowed with optoelectronic functionality. The novel integrated optical SPR sensor head relies on mode conversion efficiency for its operational principle. The beauty of this type of sensor head is it can produce clear contrast in SPR spectrum with a highly miniaturized and simple structure, in contrast to several-millimeter-scale conventional absorption type or interferometer type sensor heads. The integrated optical SPR sensor with optoelectronic functionality has been realized by structuring a dielectric waveguide based SPR sensor head on a photodetector-integrated semiconductor substrate. A large number of unit sensors have been fabricated on a substrate with a batch fabrication process, which promises a high throughput SPR sensor system or low-priced disposable sensors.
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Date Issued: 2008
Identifier: CFE0002312, ucf:47841
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002312

Title: METAL BLACKS AS SCATTERING CENTERS TO INCREASE THE EFFICIENCY OF THIN FILM SOLAR CELLS.
Creator: Panjwani, Deep, Peale, Robert, University of Central Florida
Abstract / Description: Metal nano particles are investigated as scattering centers on front surface of thin-film solar cells to improve efficiency. The principle is that scattering, which is enhanced near the plasmon resonance frequency of the particle and depends on particle size, increases the effective optical path length of incident light, leading to more light absorption in active layer of thin film solar cell. The particular types of particles investigated here are known as "metal-black", well known as an IR...
Show moreMetal nano particles are investigated as scattering centers on front surface of thin-film solar cells to improve efficiency. The principle is that scattering, which is enhanced near the plasmon resonance frequency of the particle and depends on particle size, increases the effective optical path length of incident light, leading to more light absorption in active layer of thin film solar cell. The particular types of particles investigated here are known as "metal-black", well known as an IR absorber for bolometric infrared detectors. Gold-black was deposited on commercial thin-film solar cells using a thermal evaporator in a nitrogen ambient at pressures of ~1 Torr. We suggest that the broad range of length scales for gold black particles, as quantified by scanning electron microscopy, gives rise to efficient scattering over a broad range of wavelengths across the solar spectrum. The solar cell efficiency was determined both as a function of wavelength and for a solar spectrum produced by a Xe lamp and appropriate filters. Up to 20% increase in short-circuit photocurrent, and a 7% increase in efficiency at the maximum power point, were observed.
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Date Issued: 2011
Identifier: CFE0004047, ucf:49153
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004047

Plasmonics (6)	+ -
Plasmonic (4)	+ -
Surface Plasmon Resonance (3)	+ -
plasmons (3)	+ -
surface plasmon (3)	+ -

Discrete Dipole Approximation (2)	+ -
Infrared (2)	+ -
Optics (2)	+ -
Surface plasmon (2)	+ -
THz (2)	+ -
biosensor (2)	+ -
gold nanoparticles (2)	+ -
infrared (2)	+ -
nanoparticles (2)	+ -
nanophotonics (2)	+ -
plasmon (2)	+ -
waveguides (2)	+ -
2D Layered Materials (1)	+ -
2deg (1)	+ -
Antibacterial studies (1)	+ -
Antimicrobial (1)	+ -
Biosensing (1)	+ -
Biosensors (1)	+ -
Bolometers (1)	+ -
Cascaded Field Enhancement (1)	+ -
Color (1)	+ -
Computational Chemistry (1)	+ -
Conducting polymers (1)	+ -
Continuous metal film (1)	+ -
Coupling mode (1)	+ -

ETD Collection (30)	+ -
Honors Collection (3)	+ -

University of Central Florida (33)	+ -
Peale, Robert (11)	+ -
Chanda, Debashis (6)	+ -
Zou, Shengli (5)	+ -
Kik, Pieter (4)	+ -

Kuebler, Stephen (4)	+ -
Leuenberger, Michael (4)	+ -
Hernandez, Florencio (3)	+ -
Ishigami, Masa (3)	+ -
Schoenfeld, Winston (3)	+ -
Zhai, Lei (3)	+ -
Belfield, Kevin (2)	+ -
Buchwald, Walter (2)	+ -
Coffey, Kevin (2)	+ -
Gesquiere, Andre (2)	+ -
Hagan, David (2)	+ -
Huo, Qun (2)	+ -
Jewett, Travis (2)	+ -
Mucciolo, Eduardo (2)	+ -
Rahman, Talat (2)	+ -
Santra, Swadeshmukul (2)	+ -
Su, Ming (2)	+ -
Vanstryland, Eric (2)	+ -
Abdolvand, Reza (1)	+ -
Abouraddy, Ayman (1)	+ -
Bader, Carly (1)	+ -
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Brescia, Jonathan R (1)	+ -

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