Person:
Gaylord, Thomas K.

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Publication Search Results

Now showing 1 - 6 of 6
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    Optimization of sawtooth surface-relief gratings: effects of substrate refractive index and polarization
    (Georgia Institute of Technology, 2006-05) Wu, Shun-Der ; Gaylord, Thomas K. ; Glytsis, Elias N.
    The effect of the refractive index of the substrate together with the incident polarization on the optimization of sawtooth surface-relief gratings (SRGs) is investigated. The global optimum diffraction efficiencies of the −1st forward-diffracted order of sawtooth SRGs are 63 .3% occurring at n ₂ =1.47 for TE polarization and 73.8% occurring at n ₂ =2.88 for TM polarization. Incident TE polarization has higher optimum diffraction efficiency than TM polarization for all n ₂ <1.85 . In contrast, TM polarization has higher optimum diffraction efficiency than TE polarization for all n ₂ >1.85 . A polymer (n ₂ =1.5) optimum sawtooth SRG exhibits 62.6% efficiency for TE polarization. A silicon (n ₂ =3.475) optimum sawtooth SRG exhibits 68.6% efficiency for TM polarization. These sawtooth SRGs are compared to right-angle-face trapezoidal SRGs. It is found that the optimum profiles of right-angle-face trapezoidal SRGs have only very slightly increased efficiencies over sawtooth SRGs (0.04% for TE and 0.55% for TM).
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    Optimization of anisotropically etched silicon surface-relief gratings for substrate-mode optical interconnects
    (Georgia Institute of Technology, 2006-01) Wu, Shun-Der ; Gaylord, Thomas K. ; Maikisch, Jonathan S. ; Glytsis, Elias N.
    The optimum profiles of right-angle-face anisotropically etched silicon surface-relief gratings illuminated at normal incidence for substrate-mode optical interconnects are determined for TE, TM, and random linear (RL) polarizations. A simulated annealing algorithm in conjunction with the rigorous coupled-wave analysis is used. The optimum diffraction efficiencies of the −1 forward-diffracted order are 37.3% , 67.1% , and 51.2% for TE-, TM-, and RL-polarization-optimized profiles, respectively. Also, the sensitivities to grating thickness, slant angle, and incident angle of the optimized profiles are presented.
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    Three-dimensional converging-diverging Gaussian beam diffraction by a volume grating
    (Georgia Institute of Technology, 2005-07) Wu, Shun-Der ; Gaylord, Thomas K. ; Glytsis, Elias N. ; Wu, Yu-Ming
    The diffraction characteristics of a volume grating (VG) illuminated by a three-dimensional (3-D) converging-diverging Gaussian beam at conical incidence are investigated by applying 3-D finite-beam (FB) rigorous coupled-wave analysis (RCWA) based on the conventional 3-D RCWA in conjunction with two-dimensional plane-wave decomposition. The Gaussian beam is assumed to have an arbitrary incidence angle, an arbitrary azimuthal angle, and any linear polarization. The two cases with linear polarizations of the central beam of the Gaussian (E _|_ K and H _|_ K) are investigated. The diffraction efficiencies and the diffracted beam profiles for both unslanted VGs and slanted VGs (designed for substrate-mode optical interconnects) are presented. In general, the diffraction efficiencies of a converging-diverging spherical Gaussian beam diffracted by both unslanted VGs and slanted VGs increase and approach the central-beam results as the refractive-index modulation increases.
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    Angular sensitivities of volume gratings for substrate-mode optical interconnects
    (Georgia Institute of Technology, 2005-07) Wu, Shun-Der ; Gaylord, Thomas K. ; Glytsis, Elias N. ; Wu, Yu-Ming
    The angular sensitivities of slanted volume gratings (VGs) illuminated by three-dimensional (3-D) converging-diverging spherical Gaussian beams for substrate-mode optical interconnects in microelectronics are analyzed by application of 3-D finite-beam rigorous coupled-wave analysis. Angular misalignments about the z, y, and x axes that correspond to yaw, pitch, and roll misalignments resulting from manufacturing tolerances of chips are investigated. Two cases of linear polarization of the central beam of the Gaussian are considered: E _|_ K and H _|_ K, where K is the grating vector. From worst-case manufacturing tolerances, the ranges of yaw, pitch, and roll misalignment angles are alpha=±1.17°, beta=±3.04°, and gamma=±3.04°, respectively. Based on these ranges of misalignment angles, the decreases of diffraction efficiencies for slanted VGs that are due to both the yaw and the roll misalignments are relatively small. However, the efficiency of substrate-mode optical interconnects achieved by slanted VGs could be reduced by 61.04% for E _|_ K polarization and by 58.63% for H _|_ K polarization because of the pitch misalignment. Thus the performance of a VG optical interconnect is most sensitive to pitch misalignment.
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    Optimization of finite-length input volume holographic grating couplers illuminated by finite-width incident beams
    (Georgia Institute of Technology, 2005-07) Wu, Shun-Der ; Glytsis, Elias N. ; Gaylord, Thomas K.
    A finite volume holographic grating coupler (VHGC) normally illuminated with various incident-beam profiles (such as a Gaussian beam, a flat cosine-squared beam, and an exponential-decay beam) with finite beam widths for input coupling is rigorously analyzed by use of the finite-difference frequency-domain method. The effects of the incident-beam width, the incident-beam position, the incident-beam profile, and the incident-beam angle of incidence on the input coupling efficiency are investigated. The optimum conditions for input coupling are determined. Both a VHGC embedded in the waveguide film region and a VHGC placed in the waveguide cover region are investigated. For a given finite VHGC, the input coupling efficiencies are strongly dependent on incident-beam widths, incident-beam positions, and incident-beam angles of incidence, but are only weakly dependent on incident-beam profiles.
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    Substrate-embedded and flip-chip-bonded photodetector polymer-based optical interconnects: Analysis, design, and performance
    (Georgia Institute of Technology, 2003-10) Glytsis, Elias N. ; Jokerst, Nan Marie ; Villalaz, Ricardo A. ; Cho, Sang-Yeon ; Wu, Shun-Der ; Huang, Zhaoran ; Brooke, Martin A. ; Gaylord, Thomas K.
    The performance of three optoelectronic structures incorporating substrate-embedded InP-based inverted metal–semiconductor–metal photodetectors and/or volume holographic gratings are analyzed and compared at the primary optical communication wavelengths. These structures, in conjunction with optical-quality polymer layers, can be easily integrated into silicon microelectronic substrates for the purpose of implementing potentially low-cost high-data-rate chip-level or substrate-level optical interconnects. The structures are as follows: a) an evanescent-coupling architecture with a substrate- embedded photodetector, b) a volume-holographic-grating coupler architecture with a substrate-embedded photodetector, and c) a volume-holographic-grating coupler architecture with a flip-chip-bonded photodetector. It is found that the primary characteristic of the evanescent coupling architectures is the efficient performance for both TE and TM polarizations with the disadvantage of exponentially decreasing efficiency with increasing separation between the waveguide film layer and the photodetector layer. On the other hand, the primary characteristic of the volume holographic grating architectures is the possibility of wavelength and polarization selectivity and their independence on the separation between the photodetector layer and the waveguide. Comparison of the analysis with experimental results is also included in the case of the evanescent coupling into a substrate-embedded photodetector.