Adibi, Ali

Associated Organization(s)
ArchiveSpace Name Record

Publication Search Results

Now showing 1 - 10 of 14
  • Item
    Quantitative modeling of coupling-induced resonance frequency shift in microring resonators
    (Georgia Institute of Technology, 2009-12) Li, Qing ; Soltani, Mohammad ; Atabaki, Amir Hossein ; Yegnanarayanan, Siva ; Adibi, Ali
    We present a detailed study on the behavior of coupling-induced resonance frequency shift (CIFS) in dielectric microring resonators. CIFS is related to the phase responses of the coupling region of the resonator coupling structure, which are examined for various geometries through rigorous numerical simulations. Based on the simulation results, a model for the phase responses of the coupling structure is presented and verified to agree with the simulation results well, in which the first-order coupled mode theory (CMT) is extended to second order, and the important contributions from the inevitable bent part of practical resonators are included. This model helps increase the understanding of the CIFS behavior and makes the calculation of CIFS for practical applications without full numerical simulations possible.
  • Item
    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).
  • Item
    High quality planar silicon nitride microdisk resonators for integrated photonics in the visible wavelength range
    (Georgia Institute of Technology, 2009-08) Hosseini, Ehsan Shah ; Yegnanarayanan, Siva ; Atabaki, Amir Hossein ; Soltani, Mohammad ; Adibi, Ali
    High quality factor (Q≈3.4×10⁶) microdisk resonators are demonstrated in a Si3N4 on SiO₂ platform at 652–660 nm with integrated in-plane coupling waveguides. Critical coupling to several radial modes is demonstrated using a rib-like structure with a thin Si3N4 layer at the air-substrate interface to improve the coupling.
  • Item
    Design and demonstration of compact, wide bandwidth coupled-resonator filters on a silicon-on-insulator platform
    (Georgia Institute of Technology, 2009-02) Li, Qing ; Soltani, Mohammad ; Yegnanarayanan, Siva ; Adibi, Ali
    We design and fabricate a compact third-order coupled-resonator filter on the silicon-on-insulator platform with focused application for on-chip optical interconnects. The filter shows a large flat bandwidth (3dB 3.3nm), large FSR (~18nm), more than 18dB out-of-band rejection at the drop port and more than 12 dB extinction at the through port, as well as a negligible drop loss (<0.5dB) within a footprint of 0.0004 mm².
  • Item
    Sustained GHz oscillations in ultra-high Q silicon microresonators
    (Georgia Institute of Technology, 2009) Soltani, Mohammad ; Yegnanarayanan, Siva ; Li, Qing ; Atabaki, Amir ; Eftekhar, Ali A. ; Adibi, Ali
    We report the experimental observation of long-sustained GHz electronic oscillations resulting from coupled electron-photon dynamics in ultra-high-Q Si microdisk resonators with CW pumping. Theoretical analysis identifies conditions for steady-state GHz oscillations while suppressing thermal oscillations.
  • Item
    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.
  • Item
    Improvement of thermal properties of ultra-high Q silicon microdisk resonators
    (Georgia Institute of Technology, 2007-12) Soltani, Mohammad ; Li, Qing ; Yegnanarayanan, Siva ; Adibi, Ali
    We present a detailed study of the thermal properties of ultra-high quality factor (Q) microdisk resonators on silicon-on-insulator (SOI) platforms. We show that by preserving the buried oxide layer underneath the Si resonator and by adding a thin Si pedestal layer at the interface between the resonator and the oxide layer we can increase the overall thermal conductivity of the structure while the ultra-high Q property is preserved. This allows higher field intensities inside the resonator which are crucial for nonlinear optics applications.
  • Item
    Ultra-high Q planar silicon microdisk resonators for chip-scale silicon photonics
    (Georgia Institute of Technology, 2007-04) Soltani, Mohammad ; Yegnanarayanan, Siva ; Adibi, Ali
    We report the fabrication and experimental characterization of an ultra-high Q microdisk resonator in a silicon-on-insulator (SOI) platform. We examine the role of the substrate in the performance of such microdisk resonators. While substrate leakage loss has warranted the necessity of substrate undercut structures in the past, we show here that the substrate has a very useful role to play for both passive chip-scale device integration as well as active electronic device integration. Two device architectures for the disk-on-substrate are studied in order to assess the possibility of such an integration of high Q resonators and active components. Using an optimized process for fabrication of such a resonator device, we experimentally demonstrate a Q~3×10 ⁶, corresponding to a propagation loss ~0.16 dB/cm. This, to our knowledge, is the maximum Q observed for silicon microdisk cavities of this size for disk-on-substrate structures. Critical coupling for a resonance mode with an unloaded Q~0.7×10 ⁶ is observed. We also report a detailed comparison of the obtained experimental resonance spectrum with the theoretical and simulation analysis. The issue of waveguide-cavity coupling is investigated in detail and the conditions necessary for the existence or lack of critical coupling is elaborated.
  • Item
    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.
  • Item
    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.