Gaylord, Thomas K.

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Now showing 1 - 10 of 37
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    Accurate cross-sectional stress profiling of optical fibers
    (Georgia Institute of Technology, 2009-09) Hutsel, Michael R. ; Ingle, Reeve ; Gaylord, Thomas K.
    A novel technique for determining two-dimensional, cross-sectional stress distributions in optical fibers and fiber-based devices is presented. Use of the Brace-Kohler compensator technique and a polarization microscope for the measurement of retardation
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    Conditions for primitive-lattice-vector-direction equal contrasts in four-beam-interference lithography
    (Georgia Institute of Technology, 2009-08) Stay, Justin L. ; Gaylord, Thomas K.
    Four distinct conditions for primitive-lattice-vector-direction equal contrasts in four-beam interference are introduced and described. By maximizing the absolute contrast subject to an equal contrast condition, lithographically useful interference patterns are found. Each condition is described in terms of the corresponding constraints on the plane wave wave vectors, polarizations, and intensities. The resulting locations of global intensity maxima, minima, and saddle points are presented. Subordinate conditions for unity absolute contrast are also developed. Three lattices are treated for each condition: simple cubic, face-centered cubic, and body-centered cubic.
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    Long-term analog-to-digital conversion development by short-term photonic crystal development
    (Georgia Institute of Technology, 2009-07-14) Gaylord, Thomas K. ; Kilby, Gregory R.
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    Contrast in four-beam-interference lithography
    (Georgia Institute of Technology, 2008-07) Stay, Justin L. ; Gaylord, Thomas K.
    Specific configurations of four linearly polarized, monochromatic plane waves have previously been shown to be capable of producing interference patterns exhibiting the symmetries inherent in all 14 Bravais lattices. We present (1) the range of possible absolute contrasts, (2) the conditions for unity absolute contrast, and (3) the types of interference patterns possible for configurations of four beams interference that satisfy the uniform contrast condition. Results are presented for three Bravais lattice structures: Base- and face-centered cubic and simple cubic.
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    Three-beam-interference lithography: contrast and crystallography
    (Georgia Institute of Technology, 2008-06) Stay, Justin L. ; Gaylord, Thomas K.
    Specific configurations of three linearly polarized, monochromatic plane waves have previously been shown to be capable of producing interference patterns exhibiting symmetry inherent in 5 of the 17 plane groups. Starting with the general expression for N linearly polarized waves, three-beam interference is examined in detail. The totality of all possible sets of constraints for producing the five plane groups is presented. In addition, two uniform contrast conditions are identified and discussed. Further, it is shown that when either of the uniform contrast conditions is applied and the absolute contrast is maximized, unity absolute contrast is achievable.
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    Algorithm performance in the determination of the refractive-index profile of optical fibers
    (Georgia Institute of Technology, 2008-02) Hutsel, Michael R. ; Montarou, Carole C. ; Dachevski, Alexei I. ; Gaylord, Thomas K.
    Three algorithms for computing the refractive-index profile of azimuthally symmetric optical fibers via the inverse Abel transform are compared to determine their relative accuracies. Appropriate values of algorithm parameters are also determined. The direct differentiation algorithm, the iterative algorithm, and the Fourier algorithm are used to calculate the refractive-index profile from simulated measurements of the phase shift of light transmitted transversely through the fiber. The rms error in the calculated index profile is used to quantify the accuracy of each algorithm. The Fourier algorithm is typically the most accurate of the three.
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    Induced-dipole-electric-field contribution of atomic chains and atomic planes to the refractive index and birefringence of nanoscale crystalline dielectrics
    (Georgia Institute of Technology, 2007-09) Gaylord, Thomas K. ; Chang, Yin-Jung
    The induced-dipole-electric-field contribution to the refractive index at any location within a nanometer-scale dielectric is quantified by summing the electronic dipole contributions due to all the surrounding atoms in the dielectric. Using a tetragonal lattice and varying the ratio of lattice constants illustrates the important limiting chainlike and planelike behaviors. Strong polarizing effects and thus high refractive indices occur for an electric field applied along the length of a chain of atoms or applied in a planar direction to a plane of atoms. In contrast, a strong depolarizing effect and thus low refractive indices occur for an electric field applied normal to a chain of atoms or applied normal to a plane of atoms. Birefringence is increased or decreased by the simultaneous presence or absence of polarizing and depolarizing effects.
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    Optimum parallel-face slanted surface-relief gratings
    (Georgia Institute of Technology, 2007-06) Maikisch, Jonathan S. ; Gaylord, Thomas K.
    Using a combination of rigorous coupled-wave analysis and simulated annealing, parallel-face slanted surface-relief gratings (PFSSRGs) are optimized. For substrate-mode optical interconnects, profiles are presented for both polymer and silicon PFSSRGs for both TE and TM polarizations at normal incidence with grating periods designed to give a 45° output angle in the negative-first forward-diffracted order. The resulting diffraction efficiencies range from 70% to 99%, with a majority of the optimized profiles yielding over 90%. Optimized polymer profiles for TE and TM polarizations exhibit similar high diffraction efficiencies, but the TM profiles generally require greater groove depths. Silicon profiles optimized for TM polarization have greater diffraction efficiencies than those for TE polarization. Profiles that can feasibly be fabricated are identified, and sensitivities to groove depth, filling factor, slant angle, and incident angle are shown to be modest.
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    Attenuation in waveguides on FR-4 boards due to periodic substrate undulations
    (Georgia Institute of Technology, 2007-04) Chang, Yin-Jung ; Gaylord, Thomas K. ; Chang, Gee-Kung
    The guided-mode attenuation associated with optical-interconnect-polymer waveguides fabricated on FR-4 printed-circuit boards is quantified. The rigorous transmission-line network approach is used and the FR-4 substrate is treated as a long-period substrate grating. A quantitative metric for an appropriate matrix truncation is presented. The peaks of attenuation are shown to occur near the Bragg conditions that characterize the leaky-wave stop bands. For a typical 400 µm period FR-4 substrate with an 8 µm corrugation depth, a buffer layer thickness of about 40 µm is found to be needed to make the attenuation negligibly small.
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    Board-level optical-to-electrical signal distribution at 10 Gb/s
    (Georgia Institute of Technology, 2006-09) Chang, Yin-Jung ; Guidotti, Daniel ; Wan, Lixi ; Gaylord, Thomas K. ; Chang, Gee-Kung
    An opto/electrical prototype for on-board optical-to-electrical signal broadcasting operating at 10 Gb/s per channel over an interconnect distance of 10 cm is demonstrated. An improved 1 4 multimode interference (MMI) splitter at 1550 nm with linearly tapered output facet is heterogeneously integrated with four p-i-n photodetectors (PDs) on a silicon (Si) bench. The Si bench itself is hybrid integrated onto an FR-4 printed-circuit board with four receiver channels. A novel fabrication/integration approach demonstrates the simultaneous alignment between the four waveguides and the four PDs during the MMI fabrication process. The entire system is fully functional at 10 Gb/s.