Adibi, Ali

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Now showing 1 - 8 of 8
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    Systematic Design of Wide-Bandwidth Photonic Crystal Waveguide Bends With High Transmission and Low Dispersion
    (Georgia Institute of Technology, 2010-06) Askari, Murtaza ; Momeni, Babak ; Soltani, Mohammad ; Adibi, Ali
    We identify factors affecting transmission and dispersive properties of photonic crystal waveguide (PCW) bends, using 2-D simulations and present a method for systematic design of PCW bends to achieve high transmission and low dispersion over large bandwidths. The bends presented here have higher bandwidth and lower dispersion than bends already reported.
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    Large-scale array of small high-Q microdisk resonators for on-chip spectral analysis
    (Georgia Institute of Technology, 2009-10) Soltani, Mohammad ; Li, Qing ; Yegnanarayanan, Siva ; Momeni, Babak ; Eftekhar, Ali Asghar ; Adibi, Ali
    We demonstrate on-chip, large-scale arrays of small high-Q microdisk resonators, suitable for both in-plane coupling and out-of-plane (imaging) spectral analysis devices with high resolution (linewidth < 50pm to 0.5nm), and large FSR (> 50nm).
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    Strong angular dispersion using higher bands of planar silicon photonic crystals
    (Georgia Institute of Technology, 2008-09) Momeni, Babak ; Chamanzar, Maysamreza ; Hosseini, Ehsan Shah ; Askari, Murtaza ; Soltani, Mohammad ; Adibi, Ali
    We present experimental evidence for strong angular dispersion in a planar photonic crystal (PC) structure by properly engineering the modes in the second PC band. We show that by using the second photonic band of a square lattice PC, angular dispersion of 4°/nm can be achieved. We also show that major challenges in designing practical PC devices using second band modes can be addressed by engineering the lattice and adding input/output buffer stages designed to eliminate unwanted effects.
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    Compact wavelength demultiplexing using focusing negative index photonic crystal superprisms
    (Georgia Institute of Technology, 2006-03) Momeni, Babak ; Huang, Jiandong ; Soltani, Mohammad ; Askari, Murtaza ; Mohammadi, Saeed ; Rakhshandehroo, Mohammad ; Adibi, Ali
    Here, we demonstrate a compact photonic crystal wavelength demultiplexing device based on a diffraction compensation scheme with two orders of magnitude performance improvement over the conventional superprism structures reported to date. We show that the main problems of the conventional superprism-based wavelength demultiplexing devices can be overcome by combining the superprism effect with two other main properties of photonic crystals, i.e., negative diffraction and negative refraction. Here, a 4-channel optical demultiplexer with a channel spacing of 8 nm and cross-talk level of better than -6.5 dB is experimentally demonstrated using a 4500 μm² photonic crystal region.
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    Observation of large parity-change-induced dispersion in triangular-lattice photonic crystal waveguides using phase sensitive techniques
    (Georgia Institute of Technology, 2006-02) Huang, Jiandong ; Reinke, Charles M. ; Jafarpour, Aliakbar ; Momeni, Babak ; Soltani, Mohammad ; Adibi, Ali
    We experimentally studied W1 triangular-lattice photonic crystal waveguides (PCWs) fabricated on semiconductor-on-insulator substrates using phase-sensitive lock-in techniques. In addition to the improved signal-to-noise ratio for power transmission measurements, we observed two large group delay peaks at frequencies corresponding to the photonic mode gap and parity changes of Bloch modes inside the PCWs.
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    Nonlinear finite-difference time-domain method for the simulation of anisotropic, chi((2)), and chi((3)) optical effects
    (Georgia Institute of Technology, 2006-01) Reinke, Charles M. ; Jafarpour, Aliakbar ; Momeni, Babak ; Soltani, Mohammad ; Khorasani, Sina ; Adibi, Ali ; Xu, Yong ; Lee, Reginald K.
    A two-dimensional (2-D) finite-difference timedomain (FDTD) code for the study of nonlinear optical phenomena, in which both the slowly varying and the rapidly varying components of the electromagnetic fields are considered, has been developed. The algorithm solves vectorial Maxwell’s equations for all field components and uses the nonlinear constitutive relation in matrix form as the equations required to describe the nonlinear system. The stability of the code is discussed and its effectiveness is demonstrated through the simulations of self-phase modulation (SPM) and second-harmonic generation (SHG). The authors also show that the combination of nonlinear effects with PCs can result in a significant improvement in device size and integrability, using the example of a Mach–Zehnder interferometer (MZI).
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    Investigation of physical mechanisms in coupling photonic crystal waveguiding structures
    (Georgia Institute of Technology, 2004-10) Badieirostami, Majid ; Momeni, Babak ; Soltani, Mohammad ; Adibi, Ali ; Xu, Yong ; Lee, Reginald K.
    We explain the fundamental physical mechanisms involved in coupling triangular lattice photonic crystal waveguides to conventional dielectric slab waveguides. We show that the two waveguides can be efficiently coupled outside the mode gap frequencies. We especially focus on the coupling of the two structures within the mode gap frequencies and show for the first time that the diffraction from the main photonic crystal structure plays an important role on the reflection of power back into the slab waveguide. The practical importance of this effect and possible strategies to modify it are also discussed.
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    General methods for designing single-mode planar photonic crystal waveguides in hexagonal lattice structures
    (Georgia Institute of Technology, 2003-06) Wu, N. ; Javanmard, M. ; Momeni, Babak ; Soltani, Mohammad ; Adibi, Ali ; Xu, Yong ; Lee, Reginald K.
    We systematically investigate and compare general methods of designing single mode photonic crystal waveguides in a two-dimensional hexagonal lattice of air holes in a dielectric material. We apply the rather general methods to dielectric-core hexagonal lattice photonic crystals since they have not been widely explored before. We show that it is possible to obtain single mode guiding in a limited portion of the photonic bandgap of hexagonal lattice structures. We also compare the potentials of different photonic crystal lattices for designing single-mode waveguides and conclude that triangular lattice structures are the best choice.