Browsing by Subject "Plasmons (Physics)"
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Item Computer processing of plasmon tomography images(2012-08) Houk, Adam; Grave de Peralta, Luis; Bernussi, Ayrton A.A method to analyze Surface Plasmon Polaritons (SPP) has been commonly used in recent years known as SPP Tomography. This method allows for the creation of back focal plane (BFP) images when thin metals are used for SPP structures. It is the purpose of this paper to discuss the necessary information imparting the knowledge of how one can analyze the BFP images and utilize necessary programming skills in order to create a better method of properly doing this analysis. By allowing creating a Mathematica program that is user friendly those who need to analyze these structures will then have a tool that is useful, which may be more accurate, and quick. A few BFP examples of hexagonal and square lattices are used to test the accuracy of the program that was developed. These structures were fabricated with a known crystal period, and numerical aperture, which allows for calculated comparisons for accuracy. By making this comparison the success of the program is established.Item Optical near-field effects for submicron patterning and plasmonic optical devices(2007) Battula, Arvind Reddy, 1979-; Chen, ShaochenMetallic films with narrow and deep subwavelength gratings or holes having a converging-diverging channel (CDC) can exhibit enhanced transmission resonances for wavelengths larger than the periodicity of the grating or hole. Using the finite element method, it is shown that by varying the gap size at the throat of a CDC, the spectral locations of the transmission resonance bands can be shifted close to each other and have high transmittance in a very narrow energy band. Additionally, the transmission of light can be influenced by the presence of the externally applied magnetic field H. The spectral locations of the transmission peak resonances depend on the magnitude and the direction of H. The transmission peaks have blue-shift with the increase in H. A new multilayer thermal emitter has been analyzed in the visible wavelength range. The proposed emitter has large temporal and spatial coherence extending into the far field. The thermal emitter is made up of a cavity that is surrounded by a thin silver grating having a CDC on one side and a one-dimensional (1D) photonic crystal (PhC) on the other side. The large coherence length is achieved by making use of the coherence properties of the surface waves. Due to the nature of surface waves the new multilayer structure can attain the spectral and directional control of emission with only ppolarization. The resonance condition inside the cavity is extremely sensitive to the wavelength, which would then lead to high emission in a very narrow wavelength band. In addition a new tunable plasmonic crystal (tPLC) was proposed, where the plasmonic or polaritonic mode of a metallic array can be combined with the photonic mode of a hole array in a dielectric slab for achieving negative refraction and still posses an extra degree of freedom for tuning the tPLC as a superlens to operate at different frequencies. The tunability of the single planar tPLC slab is demonstrated numerically for subwavelength imaging (FWHM 0.38[lambda]~ 0.42[lambda]) by just varying the fluid in the hole array, thereby enabling the realization of ultracompact tunable superlens and paving the way for a new class of lens. An aggressive pursuit for decreasing the minimum feature size in high bandgap materials has lead to various challenges in nanofabrication. However, it is difficult to achieve critical dimensions at sub-wavelength scale using traditional optical lithography. A new technique to create submicron patterns on hard-to-machine materials like silicon carbide (SiC) and borosilicate glass with a laser beam is demonstrated. Here the principle of optical near-field enhancement between the spheres and substrate when irradiated by a laser beam has been used for obtaining the patterning.Item Plasmonic nanoparticles for imaging intracellular biomarkers(2007-05) Kumar, Sonia, 1978-; Richards-Kortum, Rebecca, 1964-; Sokolov, Konstantin V. (Associate professor)Molecular optical imaging enables the ability to non-invasively image biological function. When used in conjunction with optical contrast agents, molecular imaging can provide biomarker-specific information with subcellular spatial resolution. Plasmonic nanoparticles are unique optical contrast agents due to the fact that the intensity and peak wavelength of scattering is dependant on interparticle spacing. This distance dependance puts these nanosensors in a position to probe molecular interactions by exploiting contrast between isolated and closely spaced nanoparticles. This dissertation presents the first intracellular molecular imaging platform using multifunctional gold nanoparticles which incorporate both cytosolic delivery and targeting moieties on the same particle. In order to produce robust nanosensors, a novel conjugation strategy was developed involving a heterofunctional linker capable of rigidly attaching various components to the nanoparticle surface. Since most biomarkers of interest are localized intracellularly, the delivery functionality was a key focus. It was achieved using the TAT-HA2 fusion peptide which has been previously shown to enhance both endosomal uptake and subsequent release into the cytosol. The feasibility of these nanoparticles as intracellular sensors was proposed by attempting to image actin rearrangement in live fibroblasts. The assembly of nanoparticles at the leading of motile cells was which was potentially due to actin targeting resulted in a red shift in scattering maxima due to plasmon resonance coupling between particles as well as a dramatic increase in scattering intensity. Although several challenges still exist, the potential for these contrast agents as nanosensors for the presence of proteins implicated in viral carcinogenesis is also introduced.Item Quantum plasmonics(2012-05) Dominguez, Daniel; Grave de Peralta, Luis; Bernussi, Ayrton A.; Holtz, MarkThis work explores the quantum limit of Surface Plasmon Polariton (SPP) generation based on Bohr’s Correspondence Principle, i.e. that the quantum description of a phenomenon must converge to its classical counterpart in the limit of large numbers. Specifically, this work addresses the excitation and detection of single-photon SPPs. This is accomplished by first exploring whether SPPs can be excited using an extremely low intensity pump beam and traditional SPP fluorescence generation in a Kreschmann configuration setup; and then by using Spontaneous Paramedic Down-Conversion (SPDC) as a source of SPP excitation in a gold-gold grating. The detectors used for the experiment are Single Photon Counting Modules (SPCM) that have the ability to detect low intensity light, in the realm of single photons. The granular effect of light is demonstrated by integrating the Hanbury Brown and Twiss experiment into the SPP detection scheme and measuring the degree of second order coherence g(2)(0) of both the SPP excitation beam and the SPP leakage radiation. The results demonstrate that by using beam of single photons as a source of excitation, one can indeed generate single-photon SPP’s whose leakage radiation that remains temporally spaced.Item Study of surface plasmon polaritons (SPPs) propagation through plasmonic crystals(2012-05) Tarigan, Hendra J.; Peralta, Luis G.; Bernussi, Ayrton A.A periodic array of air holes (diameter=200 nm, periodicity=344 nm), which are embedded in a 110 nm PMMA layer (above a 50 nm Au layer) are fabricated to form square lattices, which are called plasmonic crystals. A measuring technique, called SPP Tomography is employed. A linearly polarized He-Ne laser light ( =632.8 nm) and a set of trenches (formed by a composite of PMMA/Au-Air/Au layers) are utilized to excite three Surface Plasmon Polaritons (SPPs) beams that propagate in directions that are perpendicular to the respective sets of trenches. Further, the three SPP beams propagate toward the crystals at 45o and 90o angles of incidence, with reference to the orientation of the sides of the crystal unit cells, respectively. The SPP beam with a 45o angle of incidence continues propagating through the crystals, while the other two SPPs with a 90o angle of incidence are impeded as they start propagating through the crystals. After magnified by a microscope (Nikon Eclipse 300 series), the surface emission (SE) image of the propagating SPP is captured by a CCD camera at a far field. From such a surface image a plot of SPP intensity, I, vs. position, x, is generated constituting an exponentially decaying function. The decay constant of such a function represents the imaginary part, designated as , of the kSPP wave vector allowing us to quantify the propagation length, Lx, of the SPP beam inside and outside the crystal area. The effective index of refraction, neff, and kSPP values inside the crystals are determined theoretically and experimentally. The theory makes use of a filling factor and the bowing factor, . On the other hand, the experimental method employs CCD acquired Fourier Plane (FP) images. The two methods show an excellent agreement in terms of the value of neff inside the crystals, which is equal to 1.07218 confirming the merit and significance of the experimentally acquired Fourier Plane (FP) images. (kSPP inside the crystal can be calculated once neff is determined).Item Sub-wavelength electromagnetic phenomena in plasmonic and polaritonic nanostructures: from optical magnetism to super-resolution(2007-12) Urzhumov, Yaroslav A., 1979-; Shvets, G.Effective medium theory of sub-wavelength metallic, semiconducting and dielectric nanostructures that encompasses their electric, magnetic and magnetoelectric response at optical frequencies is introduced. Theory development is motivated by the recent surge of interest in electromagnetic metamaterials: nanostructured composites with unusual or naturally unavailable electromagnetic properties. Unlike numerous other studies, this work focuses on strongly sub-wavelength (unit cell size a λ/n) structures inasmuch as non-subwavelength composites, in general, cannot be described with effective medium parameters. The theory starts from purely electrostatic description of non-magnetic composites and uses plasmon eigenfunctions as the basis. Magnetism and other retardation phenomena are taken into account as perturbations of electrostatic equations. Theoretic description is validated by experimental data on extraordinary optical transmission through subwavelength hole arrays in crystalline silicon carbide films. It is shown that one of the most amazing applications of optical metamaterials, known as the “superlens”, enables deeply sub-wavelength spatial resolution not limited by Abbe’s resolution of a microscope. Theoretical grounds and designs of proof-of-principle verification experiments for near-field sub-wavelength imaging are presented. Theoretical principles and formulas are applied to the problem of engineering an optical negativeindex metamaterial (NIM) that may be used to improve the near-field superlens. NIM engineering begins with simple two-dimensional examples (cylinder arrays, wire pairs) and advances to more complicated metamaterials (strip-film and strip-wire arrays, tetrahedral clusters). Finally, the concept of liquid negative-index metafluids (NIMF) based on plasmonic nanoclusters is introduced and exemplified using tetrahedral cluster colloids. Clusters of plasmonic nanospheres, known as Artificial Plasmonic Molecules (APM), can be easily fabricated in macroscopic amounts and, depending on their symmetry, may exhibit three-dimensionally isotropic electromagnetic response.