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Gaylord,
Thomas K.
Gaylord,
Thomas K.
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ItemOptimization of sawtooth surfacerelief gratings: effects of substrate refractive index and polarization(Georgia Institute of Technology, 200605) Wu, ShunDer ; 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 surfacerelief gratings (SRGs) is investigated. The global optimum diffraction efficiencies of the −1st forwarddiffracted 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 rightangleface trapezoidal SRGs. It is found that the optimum profiles of rightangleface trapezoidal SRGs have only very slightly increased efficiencies over sawtooth SRGs (0.04% for TE and 0.55% for TM).

ItemOptimization of anisotropically etched silicon surfacerelief gratings for substratemode optical interconnects(Georgia Institute of Technology, 200601) Wu, ShunDer ; Gaylord, Thomas K. ; Maikisch, Jonathan S. ; Glytsis, Elias N.The optimum profiles of rightangleface anisotropically etched silicon surfacerelief gratings illuminated at normal incidence for substratemode optical interconnects are determined for TE, TM, and random linear (RL) polarizations. A simulated annealing algorithm in conjunction with the rigorous coupledwave analysis is used. The optimum diffraction efficiencies of the −1 forwarddiffracted order are 37.3% , 67.1% , and 51.2% for TE, TM, and RLpolarizationoptimized profiles, respectively. Also, the sensitivities to grating thickness, slant angle, and incident angle of the optimized profiles are presented.

ItemThreedimensional convergingdiverging Gaussian beam diffraction by a volume grating(Georgia Institute of Technology, 200507) Wu, ShunDer ; Gaylord, Thomas K. ; Glytsis, Elias N. ; Wu, YuMingThe diffraction characteristics of a volume grating (VG) illuminated by a threedimensional (3D) convergingdiverging Gaussian beam at conical incidence are investigated by applying 3D finitebeam (FB) rigorous coupledwave analysis (RCWA) based on the conventional 3D RCWA in conjunction with twodimensional planewave 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 substratemode optical interconnects) are presented. In general, the diffraction efficiencies of a convergingdiverging spherical Gaussian beam diffracted by both unslanted VGs and slanted VGs increase and approach the centralbeam results as the refractiveindex modulation increases.

ItemAngular sensitivities of volume gratings for substratemode optical interconnects(Georgia Institute of Technology, 200507) Wu, ShunDer ; Gaylord, Thomas K. ; Glytsis, Elias N. ; Wu, YuMingThe angular sensitivities of slanted volume gratings (VGs) illuminated by threedimensional (3D) convergingdiverging spherical Gaussian beams for substratemode optical interconnects in microelectronics are analyzed by application of 3D finitebeam rigorous coupledwave 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 worstcase 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 substratemode 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.

ItemOptimization of finitelength input volume holographic grating couplers illuminated by finitewidth incident beams(Georgia Institute of Technology, 200507) Wu, ShunDer ; Glytsis, Elias N. ; Gaylord, Thomas K.A finite volume holographic grating coupler (VHGC) normally illuminated with various incidentbeam profiles (such as a Gaussian beam, a flat cosinesquared beam, and an exponentialdecay beam) with finite beam widths for input coupling is rigorously analyzed by use of the finitedifference frequencydomain method. The effects of the incidentbeam width, the incidentbeam position, the incidentbeam profile, and the incidentbeam 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 incidentbeam widths, incidentbeam positions, and incidentbeam angles of incidence, but are only weakly dependent on incidentbeam profiles.

ItemSubstrateembedded and flipchipbonded photodetector polymerbased optical interconnects: Analysis, design, and performance(Georgia Institute of Technology, 200310) Glytsis, Elias N. ; Jokerst, Nan Marie ; Villalaz, Ricardo A. ; Cho, SangYeon ; Wu, ShunDer ; Huang, Zhaoran ; Brooke, Martin A. ; Gaylord, Thomas K.The performance of three optoelectronic structures incorporating substrateembedded InPbased 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 opticalquality polymer layers, can be easily integrated into silicon microelectronic substrates for the purpose of implementing potentially lowcost highdatarate chiplevel or substratelevel optical interconnects. The structures are as follows: a) an evanescentcoupling architecture with a substrate embedded photodetector, b) a volumeholographicgrating coupler architecture with a substrateembedded photodetector, and c) a volumeholographicgrating coupler architecture with a flipchipbonded 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 substrateembedded photodetector.