Salah Obayya - Academia.edu (original) (raw)
Papers by Salah Obayya
Optical and Quantum Electronics
In this paper, an efficient full-vectorial modal analysis based on the rational Chebyshev pseudo-... more In this paper, an efficient full-vectorial modal analysis based on the rational Chebyshev pseudo-spectral method (V-RCPSM) is introduced to analyze 3 dimensional (3D) structures that are invariant along one spatial variable. Such structures are essential in silicon photonics and plasmonics applications where permittivity profiles with high-index contrast need precise treatment of the interface boundary conditions. Besides, such structures are open in general. Hence, good domain truncation is important. Our method handles these challenges via hybrid usage of the domain decomposition technique where the electromagnetic field is expanded in terms of Chebyshev functions in homogeneous regions, while the rational Chebyshev functions are used for semi-infinite homogeneous domains. The boundary conditions are rigorously imposed along the interfaces, a step that maintains the known exponential convergence rate of Chebyshev functions. Chebyshev functions have the ability to capture the corre...
Egyptian Journal of Pure and Applied Science
Optics Communications, 2018
Scientific Reports, 2017
A crystal superlattice structure featuring nonlinear layers with alternating orthogonal optic axe... more A crystal superlattice structure featuring nonlinear layers with alternating orthogonal optic axes interleaved with orthogonal poling directions, is shown to generate high-quality hyperentangled photon pairs via orthogonal quasi-phase-matched spontaneous parametric downconversion. We demonstrate that orthogonal quasi-phase matching (QPM) processes in a single nonlinear domain structure correct phase and group-velocity mismatches concurrently. Compared with the conventional two-orthogonal-crystals source and the double-nonlinearity single-crystal source, the orthogonal QPM superlattice is shown to suppress the spatial and temporal distinguishability of the generated photon pairs by several orders of magnitude, depending on the number of layers. This enhanced all-over-the-cone indistinguishability enables the generation of higher fluxes of photon-pairs by means of the combined use of (a) long nonlinear crystal in noncollinear geometry, (b) low coherence-time pumping and ultra-wide-ban...
Optics express, Jan 24, 2015
In this paper, a new finite element method (FEM) is proposed to analyse time domain wave propagat... more In this paper, a new finite element method (FEM) is proposed to analyse time domain wave propagation in photonic devices. Dissimilar to conventional FEM, efficient "inter-element" matrices are accurately formed through smoothing the field derivatives across element boundaries. In this sense, the new approach is termed "smoothed FEM" (SFETD). For time domain analysis, the propagation is made via the time domain beam propagation method (TD-BPM). Relying on first order elements, our suggested SFETD-BPM enjoys accuracy levels comparable to second-order conventional FEM; thanks to the element smoothing. The proposed method numerical performance is tested through applicating on analysis of a single mode slab waveguide, optical grating structure, and photonic crystal cavity. It is clearly demonstrated that our method is not only accurate but also more computationally efficient (far few run time, and memory requirements) than the conventional FEM approach. The SFETD-BPM ...
IEEE Photonics Journal, 2009
Innovative Materials and Systems for Energy Harvesting Applications
The solar energy is able to supply humanity energy for almost another 1 billion years. Optical na... more The solar energy is able to supply humanity energy for almost another 1 billion years. Optical nano-antennas (ONAs) are an attractive technology for high efficiency, and low-cost solar cells. These devices can be classified to semiconductor nano-wires and metallic nano-antenna. Extensive studies have been carried out on ONAs to investigate their ability to harvest solar energy. Inspired by these studies, the scope of the chapter is to highlight the latest designs of the two main types of ONAs. The metallic nano-antennas are discussed based on the following points: plasmon, modeling, and performance of antenna designs using different configurations and materials. Moreover, the semiconductor nano-wires are studied thoroughly in terms of photonic crystals, antenna design with different patterns, nano-wire forms and materials. Also, the applications of ONAs and their fabrication aspects such as diode challenges are presented in detail. Finally, three novel designs of ONAs are presented ...
Advanced Photonics 2015, 2015
A theoretical study of plasmonic effects in silicon nanostructures is introduced. It is found tha... more A theoretical study of plasmonic effects in silicon nanostructures is introduced. It is found that silicon exhibit metal-like properties at the edge of UV/VIS spectrum allowing silicon nanostructures to support surface plasmon modes.
Journal of the Optical Society of America B, 2015
Optical and Quantum Electronics, 2015
Journal of Lightwave Technology, 2015
Progress In Electromagnetics Research C, 2012
Numerical Simulation of Optoelectronic Devices, 2014, 2014
Numerical Simulation of Optoelectronic Devices, 2014, 2014
Advanced materials (Deerfield Beach, Fla.), Jan 21, 2015
Lead sulfide quantum dots represent an emerging photovoltaic absorber material. While their assoc... more Lead sulfide quantum dots represent an emerging photovoltaic absorber material. While their associated optical qualities are true for the colloidal solution phase, they change upon processing into thin-films. A detailed view to the optical key-parameters during solid film development is presented and the limits and outlooks for this versatile and promising absorber are discussed.
Applications of Photonic Technology 5, 2003
ABSTRACT When a photonic device is directly butt-coupled to a single mode fiber, often there is a... more ABSTRACT When a photonic device is directly butt-coupled to a single mode fiber, often there is a 90% or more optical power loss, due to their highly unequal spot-sizes. Often, by using complex microlenses, the coupling efficiency has been increased, but however at the expense of a sub-micron alignment tolerance requirement, and consequently higher associated cost for a reliable operation. Recently, monolithically integrated devices, mostly using tapered structures, have been reported as useful to modify the spot-size of semiconductor photonic devices, which could assist in the rapid implementation of 'fiber-to-the-home'. In this work, spot-size converters with a tapered core, also using novel uniform directional couplers and MMI structures are discussed. A rigorous numerical approach, based on the full vectorial finite element method, is used to design various types of monolithically integrated spot-size converters for efficient coupling to an optical fiber and results of their performance reported.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
IEEE Photonics Technology Letters, 2014
Numerical Simulation of Optoelectronic Devices, 2014, 2014
Optical and Quantum Electronics, 2013
Optical and Quantum Electronics
In this paper, an efficient full-vectorial modal analysis based on the rational Chebyshev pseudo-... more In this paper, an efficient full-vectorial modal analysis based on the rational Chebyshev pseudo-spectral method (V-RCPSM) is introduced to analyze 3 dimensional (3D) structures that are invariant along one spatial variable. Such structures are essential in silicon photonics and plasmonics applications where permittivity profiles with high-index contrast need precise treatment of the interface boundary conditions. Besides, such structures are open in general. Hence, good domain truncation is important. Our method handles these challenges via hybrid usage of the domain decomposition technique where the electromagnetic field is expanded in terms of Chebyshev functions in homogeneous regions, while the rational Chebyshev functions are used for semi-infinite homogeneous domains. The boundary conditions are rigorously imposed along the interfaces, a step that maintains the known exponential convergence rate of Chebyshev functions. Chebyshev functions have the ability to capture the corre...
Egyptian Journal of Pure and Applied Science
Optics Communications, 2018
Scientific Reports, 2017
A crystal superlattice structure featuring nonlinear layers with alternating orthogonal optic axe... more A crystal superlattice structure featuring nonlinear layers with alternating orthogonal optic axes interleaved with orthogonal poling directions, is shown to generate high-quality hyperentangled photon pairs via orthogonal quasi-phase-matched spontaneous parametric downconversion. We demonstrate that orthogonal quasi-phase matching (QPM) processes in a single nonlinear domain structure correct phase and group-velocity mismatches concurrently. Compared with the conventional two-orthogonal-crystals source and the double-nonlinearity single-crystal source, the orthogonal QPM superlattice is shown to suppress the spatial and temporal distinguishability of the generated photon pairs by several orders of magnitude, depending on the number of layers. This enhanced all-over-the-cone indistinguishability enables the generation of higher fluxes of photon-pairs by means of the combined use of (a) long nonlinear crystal in noncollinear geometry, (b) low coherence-time pumping and ultra-wide-ban...
Optics express, Jan 24, 2015
In this paper, a new finite element method (FEM) is proposed to analyse time domain wave propagat... more In this paper, a new finite element method (FEM) is proposed to analyse time domain wave propagation in photonic devices. Dissimilar to conventional FEM, efficient "inter-element" matrices are accurately formed through smoothing the field derivatives across element boundaries. In this sense, the new approach is termed "smoothed FEM" (SFETD). For time domain analysis, the propagation is made via the time domain beam propagation method (TD-BPM). Relying on first order elements, our suggested SFETD-BPM enjoys accuracy levels comparable to second-order conventional FEM; thanks to the element smoothing. The proposed method numerical performance is tested through applicating on analysis of a single mode slab waveguide, optical grating structure, and photonic crystal cavity. It is clearly demonstrated that our method is not only accurate but also more computationally efficient (far few run time, and memory requirements) than the conventional FEM approach. The SFETD-BPM ...
IEEE Photonics Journal, 2009
Innovative Materials and Systems for Energy Harvesting Applications
The solar energy is able to supply humanity energy for almost another 1 billion years. Optical na... more The solar energy is able to supply humanity energy for almost another 1 billion years. Optical nano-antennas (ONAs) are an attractive technology for high efficiency, and low-cost solar cells. These devices can be classified to semiconductor nano-wires and metallic nano-antenna. Extensive studies have been carried out on ONAs to investigate their ability to harvest solar energy. Inspired by these studies, the scope of the chapter is to highlight the latest designs of the two main types of ONAs. The metallic nano-antennas are discussed based on the following points: plasmon, modeling, and performance of antenna designs using different configurations and materials. Moreover, the semiconductor nano-wires are studied thoroughly in terms of photonic crystals, antenna design with different patterns, nano-wire forms and materials. Also, the applications of ONAs and their fabrication aspects such as diode challenges are presented in detail. Finally, three novel designs of ONAs are presented ...
Advanced Photonics 2015, 2015
A theoretical study of plasmonic effects in silicon nanostructures is introduced. It is found tha... more A theoretical study of plasmonic effects in silicon nanostructures is introduced. It is found that silicon exhibit metal-like properties at the edge of UV/VIS spectrum allowing silicon nanostructures to support surface plasmon modes.
Journal of the Optical Society of America B, 2015
Optical and Quantum Electronics, 2015
Journal of Lightwave Technology, 2015
Progress In Electromagnetics Research C, 2012
Numerical Simulation of Optoelectronic Devices, 2014, 2014
Numerical Simulation of Optoelectronic Devices, 2014, 2014
Advanced materials (Deerfield Beach, Fla.), Jan 21, 2015
Lead sulfide quantum dots represent an emerging photovoltaic absorber material. While their assoc... more Lead sulfide quantum dots represent an emerging photovoltaic absorber material. While their associated optical qualities are true for the colloidal solution phase, they change upon processing into thin-films. A detailed view to the optical key-parameters during solid film development is presented and the limits and outlooks for this versatile and promising absorber are discussed.
Applications of Photonic Technology 5, 2003
ABSTRACT When a photonic device is directly butt-coupled to a single mode fiber, often there is a... more ABSTRACT When a photonic device is directly butt-coupled to a single mode fiber, often there is a 90% or more optical power loss, due to their highly unequal spot-sizes. Often, by using complex microlenses, the coupling efficiency has been increased, but however at the expense of a sub-micron alignment tolerance requirement, and consequently higher associated cost for a reliable operation. Recently, monolithically integrated devices, mostly using tapered structures, have been reported as useful to modify the spot-size of semiconductor photonic devices, which could assist in the rapid implementation of 'fiber-to-the-home'. In this work, spot-size converters with a tapered core, also using novel uniform directional couplers and MMI structures are discussed. A rigorous numerical approach, based on the full vectorial finite element method, is used to design various types of monolithically integrated spot-size converters for efficient coupling to an optical fiber and results of their performance reported.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
IEEE Photonics Technology Letters, 2014
Numerical Simulation of Optoelectronic Devices, 2014, 2014
Optical and Quantum Electronics, 2013