Jala El-Azab

Dispersion Characteristics of Asymmetric Channel Plasmon Polariton Waveguides

A novel asymmetric channel plasmon polaritons (CPPs) is proposed and analyzed. In this paper, the dispersion characteristics of asymmetric two and three-trenched CPPs structures are studied in detail. The suggested asymmetric structures have advantages in terms of propagation length and figure of merit over the symmetric CPP waveguides. In addition, a comparative study of various CPP metals including gold and silver is also presented. It is found that the propagation length and figure of merit of the silver-based structures are better than those of gold-based structures. In addition, the effect of bending on the asymmetric CPP waveguides is investigated. The simulation results are obtained by full-vectorial finite difference method with irregular meshing capabilities and perfectly matched layer boundary conditions.

A Global Study of the Influence of Optical Feedback on a Semiconductor Laser Diode

It is well known that a semiconductor laser diode with optical feedback can show both stable (CW) and unstable (chaotic) modes of behavior. The optical output is governed by three different parameters, namely the injection current, feedback strength and optical feedback delay time. In this work, we present a detailed numerical study of the route to chaos as the feedback strength is varied for a laser diode having arbitrary injection current and external cavity length. The results are presented as a 3D phase diagram where the x-and y-axes correspond to the injection current and optical feedback delay time and the z-axis to feedback strength. This allows a global study of the route to chaos and extends the 2D results obtained by arbitrarily fixing one parameter and allowing the two other to vary.

The impact of changing HNL-DSF parameters on wavelength exchanging

Integrated Fiber (IF) approach for optical signal processing offers significant advantages in both performance and cost when compared to conventional electrical processing. The main problem in optical single processing is to maintain the data in the optical domain without converting it to the electrical domain. Currently, many devices have been proposed for processing the data in the optical domain. The Wavelength Optical Crossbar (WOC), one of the important devices in optical networks, has been developed based on the phenomenon of wavelength exchanging. High-NonLinear Dispersion Shifted Fiber (HNL-DSF) provides a good performance due to the high mixing efficiency. In this paper, we will study the impacts of changing the HNL-DSF parameter on the wavelength exchanging.

Estimation of Articular Cartilage Surface Roughness Using Gray-Level Co-Occurrence Matrix of Laser Speckle Image

The application of He-Ne laser technologies for description of articular cartilage degeneration, one of the most common diseases worldwide, is an innovative usage of these technologies used primarily in material engineering. Plain radiography and magnetic resonance imaging are insufficient to allow the early assessment of the disease. As surface roughness of articular cartilage is an important indicator of articular cartilage degeneration progress, a safe and noncontact technique based on laser speckle image to estimate the surface roughness is provided. This speckle image from the articular cartilage surface, when illuminated by laser beam, gives very important information about the physical properties of the surface. An experimental setup using a low power He-Ne laser and a high-resolution digital camera was implemented to obtain speckle images of ten bovine articular cartilage specimens prepared for different average roughness values. Texture analysis method based on gray-level co-occurrence matrix (GLCM) analyzed on the captured speckle images is used to characterize the surface roughness of the specimens depending on the computation of Haralick’s texture features. In conclusion, this promising method can accurately estimate the surface roughness of articular cartilage even for early signs of degeneration. The method is effective for estimation of average surface roughness values ranging from 0.09 µm to 2.51 µm with an accuracy of 0.03 µm.

A Method for Medical Diagnosis Based on Optical Fluence Rate Distribution at Tissue Surface

Optical differentiation is a promising tool in biomedical diagnosis mainly because of its safety. The optical parameters’ values of biological tissues differ according to the histopathology of the tissue and hence could be used for differentiation. The optical fluence rate distribution on tissue boundaries depends on the optical parameters. So, providing image displays of such distributions can provide a visual means of biomedical diagnosis. In this work, an experimental setup was implemented to measure the spatially-resolved steady state diffuse reflectance and transmittance of native and coagulated chicken liver and native and boiled breast chicken skin at 635 and 808 nm wavelengths laser irradiation. With the measured values, the optical parameters of the samples were calculated in vitro using a combination of modified Kubelka-Munk model and Bouguer-Beer-Lambert law. The estimated optical parameters values were substituted in the diffusion equation to simulate the fluence rate at the tissue surface using the finite element method. Results were verified with Monte-Carlo simulation. The results obtained showed that the diffuse reflectance curves and fluence rate distribution images can provide discrimination tools between different tissue types and hence can be used for biomedical diagnosis.

Mitigation of the effect of parameter mismatch in optical chaotic communications

Since most of chaotic communication systems are based on conventional synchronization, it is necessary to develop a high quality synchronization scheme having less dependence on parameter matching between transmitter and receiver. In this scheme, our objective is to separate chaos generation as well as message encoding/decoding from the transmitter/receiver dynamics. Therefore, we focus on how to maintain synchronization between the transmitter and receiver with minimum distortion and with fewer constraints on parameter mismatch. To check the validity of the system, a message which was introduced at the transmitter was successfully recovered at the receiver end. We expect this scheme to be useful for moderate security requirements as well as in increasing the availability and serviceability of the system. Also it can be used in a one- to multi-point communication system since some parameter mismatch is allowed for the same synchronization performance.

An enhanced OPS architecture with optical buffers

Optical Packet Switching (OPS) is a promising technology to enable next-generation high-speed IP networks. One of the main components in an OPS network is the optical switch architecture that provides the basic functionality of switching packets from input ports to the desired output ports while maintaining data in the optical domain. In asynchronous OPS networks, contention may arise when two or more packets need to be directed to the same output source leading to packet loss and thus lower switching performance. Optical buffering, which is implemented by fiber delay lines (FDLs), is one of the approaches used for resolving contention. In this paper, we focus on the design a new FDL-based switch architecture that resolves packet contention in asynchronous OPS networks and achieves the same performance as that of best known architectures but with a reduced hardware complexity. Our analysis shows that, the proposed architectures possess some interesting properties as compared to existing designs. For example, for the same packet loss level, the proposed architecture requires a number of switch ports less than that used in generic architecture.

Utilization of transversal Pockels effect in intense electric field sensing

In this work, we proposed to implement a controlled high voltage sensor based on transversal Pockels effect. The work is carried out numerically and experimentally using (BGO, Bi4Ge3O12) crystal. and simulation by the Finite Element Method (FEM) for the system is introduced to study different design parameters in order to optimize the design of the system and to find the relation between the electric field intensity within the crystal and the value of the total applied voltage depending on shape of the crystal, the permittivity of the material and the distance between the electrodes. AC high voltages were measured by the system in transversal configuration with a relative error of 3%. Due to the ambiguity of the measurement for values higher than Vπ/2, a numerical solution is proposed, depending on the variation of electrodes separation. Thus the ambiguity is removed and the measurement range is increased.

The use of optical fluence rate distribution for the differentiation of biological tissues

diffuse optical imaging is a recent, safe, non-invasive, functional, and very promising medical imaging technique that employs near infrared light to characterize biological tissue. Absorption and scattering properties of biological tissues give very important information about physiological changes associated with vasculature, cellularity, and oxygen consumption in normal and/or diseased tissue. Obtaining the optical fluence rate distribution is important when constructing the image in diffuse imaging. In this work, the significance of using the fluence rate distribution for differentiating tissue types was investigated. An experimental setup for measuring spatially-resolved steady state diffuse reflectance spectra of breast chicken skin at 660nm laser irradiation was implemented. The measured values were then used to predict the optical parameters of the samples using a combination of a modified Kubelka-Munk method and Bouguer-Beer-Lambert law. These parameters were used with a finite element model to solve the radiative transfer equation to obtain the fluence rate at the sample boundary. The results revealed that the fluence rate distribution of a 660nm laser is significant in differentiating biological tissues.

Accurate relative-phase and time-delay maps all over the emission cone of hyperentangled photon source

High flux of hyperentangled photons entails collecting the two-photon emission over relatively wide extent in frequency and transverse space within which the photon pairs are simultaneously entangled in multiple degrees of freedom. In this paper, we present a numerical approach to determining the spatial-spectral relative-phase and time-delay maps of hyperentangled photons all over the spontaneous parametric down conversion (SPDC) emission cone. We consider the hyperentangled-photons produced by superimposing noncollinear SPDC emissions of two crossed and coherentlypumped nonlinear crystals. We adopt a vectorial representation for all parameters of concern. This enables us to study special settings such as the self-compensation via oblique pump incidence. While rigorous quantum treatment of SPDC emission requires Gaussian state representation, in low-gain regime (like the case of the study), it is well approximated to the first order to superposition of vacuum and two-photon states. The relative phase and time-delay maps are then calculated between the two-photon wavepackets created along symmetrical locations of the crystals. Assuming monochromatic plane-wave pump field, the mutual signal-idler relations like energy conservation and transversemomentum conservation define well one of the two-photon with reference to its conjugate. The weaker conservation of longitudinal momentum (due to relatively thin crystals) allows two-photon emission directions coplanar with the pump beam while spreading around the perfect phase-matching direction. While prior works often adopt first-order approximation, it is shown that the relative-phase map is a very well approximated to a quadratic function in the polar angle of the two-photon emission while negligibly varying with the azimuthal angle.