Adibi, Ali

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Now showing 1 - 10 of 62
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    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.
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    Multiplex coherent anti-Stokes Raman scattering (MCARS) for chemically sensitive, label-free flow cytometry
    (Georgia Institute of Technology, 2009-12) Camp, Charles Henry, Jr. ; Yegnanarayanan, Siva ; Eftekhar, Ali Asghar ; Sridhar, Hamsa ; Adibi, Ali
    Flow cytometry is an ever-advancing high-throughput multivariate analysis tool that natively provides size and morphological information. To obtain molecular information, however, typically requires the addition of fluorophores, which are limited by spectral overlap, nonspecific binding, available conjugation chemistries, and cellular toxicity. A complementary or alternative, label-free approach to molecular information is through multiplex coherent anti-Stokes Raman scattering (MCARS), which is a coherent, nonlinear optical method that provides a wealth of molecular information by probing the Raman energies within a molecule. In this work, we demonstrate the unique capability of our MCARS flow cytometer to distinguish flowing particles and discuss system performance capabilities and possibilities.
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    A row-action based L₁-minimization approach to robust fluorescent tomography
    (Georgia Institute of Technology, 2009-10) Mohajerani, Pouyan ; Behrooz, Ali ; Eftekhar, Ali A. ; Adibi, Ali
    We present a row-action method based on minimization of the L₁ norm for improving the accuracy of fluorescent tomography in reconstruction of fluorescent objects. The method is validated using a CW system and milk-based phantoms.
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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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    Analysis of telescope arrays based receiver for deep-space optical communications with Mars
    (Georgia Institute of Technology, 2009-10) Hashmi, A. ; Eftekhar, Ali Asghar ; Adibi, Ali ; Amoozegar, Farid
    Telescope arrays receivers are analyzed for deep-space optical communications between Earth and Mars. It is shown that data rates up to 14 M bits/sec are possible when Mars is at the farthest range from the Earth.
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    Athermal operation in polymer-clad silicon microdisk resonators
    (Georgia Institute of Technology, 2009-10) Alipour, Payam ; Hosseini, Ehsan Shah ; Eftekhar, Ali Asghar ; Momeni, Babak ; Adibi, Ali
    We have used a urethane polymer as cladding to reduce the temperature sensitivity of resonance in high-Q silicon microdisk resonators. A two-order-of-magnitude improvement in resonance stability is demonstrated, and effects on the Q-factor are discussed.
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    Sub-microsecond thermal reconfiguration of silicon photonic devices
    (Georgia Institute of Technology, 2009-10) Atabaki, Amir H. ; Eftekhar, Ali A. ; Yegnanarayanan, Siva ; Adibi, Ali
    Using the experimental data we show the possibility of sub-microsecond reconfiguration of silicon photonics microresonators through pulse shaping of micro-heater excitation. Also, a novel heater structure based on small microdisk resonators with sub-hundred-nanosecond reconfiguration speed is proposed and investigated theoretically.
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    Planar photonic crystal microspectrometers in silicon-nitride for the visible range
    (Georgia Institute of Technology, 2009-09) Momeni, Babak ; Hosseini, Ehsan Shah ; Adibi, Ali
    We demonstrate the feasibility of forming a compact integrated photonic spectrometer for operation in the visible wavelength range using the dispersive properties of a planar photonic crystal structure fabricated in silicon nitride. High wavelength resolution and compact device sizes in these spectrometers are enabled by combining superprism effect, negative diffraction effect, and negative refraction effect in a 45° rotated square lattice photonic crystal. Our experimental demonstration shows 1.2 nm wavelength resolution in a 70 µm by 130 µm photonic crystal structure with better performance than alternative structures for on-chip spectroscopy, confirming the unique capability of the proposed approach to realize compact integrated spectrometers.
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    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.
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    45 Degree Polymer Micromirror Integration for Board-Level Three-Dimensional Optical Interconnects
    (Georgia Institute of Technology, 2009-06) Wang, Fengtao ; Liu, Fuhan ; Adibi, Ali
    We introduce here a simple method of integrating 45° total internal reflection micro-mirrors with polymer optical waveguides by an improved tilted beam photolithography on printed circuit boards to provide surface normal light coupling between waveguides and optoelectronic devices for optical interconnects. De-ionized water is used to couple ultraviolet beam through the waveguide core polymer layer at 45° angle during the photo exposure process. This technique is compatible with PCB manufacturing facility and suitable to large panel board-level manufacturing. The mirror slope is controlled accurately (within ±1°) with high repeatability. The insertion loss of an uncoated micro-mirror is measured to be 1.6 dB.