Pashaie, Ramin

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  • Publication
    Optical Realization of the Retinal Ganglion Receptive Fields in Electron-Trapping Material Thin Film
    (2006-04-01) Pashaie, Ramin; Farhat, Nabil H
    Optical control of the electron-trapping material is used to model the retinal ganglion cell’s receptive field. Using this approach all the retinal image processing can be done on the surface of a thin film of this material.
  • Publication
    Optical Realization of Bio-inspired Spiking Neurons In Electron Trapping Material Thin
    (2007-10-27) Pashaie, Ramin; Farhat, Nabil H.
    A thin film of electron-trapping material (ETM), when combined with suitable optical bistability, is considered as medium for optical implementation of bio-inspired neural nets. The optical mechanism of ETM under blue light and NIR exposure has the inherent ability at the material level to mimic the crucial components of the stylized Hodgkin-Huxley model of biological neuron. Combining this unique property with high resolution capability of ETM, a dense network of bio-inspired neurons can be realized in a thin film of this infrared stimulable storage phosphore. The work presented here, when combined with suitable optical bistability and optical interconnectivity, has the potential of producing an artificial nonlinear excitable medium analogue to cortical tissue.
  • Publication
    Dynamics of electron-trapping materials under blue light and near infrared exposure: an improved model
    (2007-08-13) Pashaie, Ramin; Farhat, Nabil H
    Dynamics of electron-trapping materials (ETMs) is investigated. Based on experimental observations, evolution of the ETM's luminescence is mathematically modeled by a nonlinear differential equation. This improved model can predict dynamics of ETM under blue light and near-infrared (NIR) exposures during charging, discharging, simultaneous illumination, and in the equilibrium state. The equilibrium-state luminescence of ETM is used to realize a highly nonlinear optical device with potential applications in nonlinear optical signal processing.
  • Publication
    An analytic model for the dynamics of electron trapping materials with applications in nonlinear optical signal processing
    (2008-01-01) Pashaie, Ramin; Farhat, Nabil H
    In this paper the optical mechanism and dynamics of electron trapping material under simultaneous illumination with two wavelengths is investigated. Our analytical model proves that the equilibrium state luminescence of such a material can be controlled to produce highly nonlinear behavior with potential applications in nonlinear optical signal processing and optical realization of nonlinear dynamical systems. Combining this new approach with state-of-the-art fast spatial light modulators and CCD cameras that can precisely control and measure exposure, large arrays of nonlinear processing elements can be accommodated in a thin film of this material.
  • Publication
    Realization of Receptive Fields with Excitatory and Inhibitory Responses on Equilibrium-State Luminescence of Electron Trapping Material Thin Film
    (2007-06-01) Pashaie, Ramin; Farhat, Nabil H
    Our theoretical modelings and experimental observations illustrate that the equilibrium-state luminescence of electron-trapping materials (ETMs) can be controlled to produce either excitatory or inhibitory responses to the same optical stimulus. Because of this property, ETMs have a unique potential in optical realization of neurobiologically based parallel computations. As a classic example, we have controlled the equilibrium-state luminescence of a thin film of this stimulable storage phosphor to make it behave similarly to the receptive fields of sensory neurons in the mammalian visual system, which are responsible for early visual processing.
  • Publication
    Self-Organization in a Parametrically Coupled Logistic Map Network: A Model for Information Processing in the Visual Cortex
    (2009-03-31) Pashaie, Ramin; Farhat, Nabil H
    In this paper, a new model seeking to emulate the way the visual cortex processes information and interacts with subcortical areas to produce higher level brain functions is described. We developed a macroscopic approach that incorporates salient attributes of the cortex based on combining tools of nonlinear dynamics, information theory, and the known organizational and anatomical features of cortex. Justifications for this approach and demonstration of its effectiveness are presented. We also demonstrate certain capabilities of this model in producing efficient sparse representations and providing the cortical computational maps.
  • Publication
    Fourier Decomposition Analysis af Anisotropic Inhomogeneous Dielectric Waveguide Structures
    (2007-08-01) Pashaie, Ramin
    In this paper we extend the Fourier decomposition method to compute both propagation constants and the corresponding electromagnetic field distributions of guided waves in millimeter-wave and integrated optical structures. Our approach is based on field Fourier expansions of a pair of wave equations which have been derived to handle inhomogeneous mediums with diagonalized permittivity and permeability tensors. The tensors are represented either by a grid of homogeneous rectangles or by distribution functions defined over rectangular domains. Using the Fourier expansion, partial differential equations are converted to a matrix eigenvalue problem that correctly models this class of dielectric structures. Finally numerical results are presented for various channel waveguides and are compared with those of other literatures to validate our formulation.