MZ-MMI-based all-optical switch using nonlinear coupled waveguides

We propose an all-optical switch (AOS) based on Mach-Zehnder (MZ) and Multi-mode interference (MMI) using nonlinear closely coupled waveguides. The device operates by switching between two states of coupled waveguides. In first state the refractive index of waveguides are same and light field will completely couple to nonlinear waveguide in half length of coupler and will back in the second half. We will have π phase difference in this procedure and the input field will appear in Bar-state output. In the second state the refractive index of nonlinear waveguide increase with high intensity control field. In this case, we have lower coupling and change in phase. But, we choose the best refractive index change to obtain the phase change of multiple of 2π necessary for Cross-state in output. The beam propagation method is used to simulate the device operation.     

Sulfamic acid:An efficient,cost-effective and green catalyst for crossed-aldol condensation of ketones with aromatic aldehydes under solvent-free

Aromatic aldehydes undergo crossed-aldol condensation with ketones in the presence of catalytic amount of sulfamic acid(SA) to afford the correspondingα,β-unsaturated aldol products under solvent-free conditions in good to high yields at 45-80℃.     

Analysis of a Micro-Optomechatronic Force Sensor

Abstract

The purpose of this article is to study the dynamic behavior and modal analysis of a micro-optomechatronic device with primary applications to force sensing and optical attenuation/coupling. The system consists of two initially aligned micro-cantilevers with a narrow gap between them. The light beam enters to the first waveguide and, after propagation along it, couples to second waveguide through the mentioned narrow gap. The externally static or dynamic applied force on the first micro-cantilever deflects it and results in reduced optical coupling between the two waveguides. Changes in this factor are measured to give the properties of the applied force.     

Optimum Compensator Positioning to Reduce Four-Wave Mixing in Wavelength Division Multiplexing Optical Communication Systems Using Dispersion-Managed Fibers

Abstract

The impact of the compensator's location along the optical fiber on a variation of four-wave mixing power penalty is investigated theoretically and numerically for dispersion-managed fibers in wavelength division multiplexing systems. The power penalty is analyzed for fibers with different attenuation coefficients and lengths, and the optimum positions for the compensator along the fiber is discussed in cases of both dispersion compensation of each fiber section between two amplifiers and whole-compensation.     

Thermodynamics of Near-Extremal Solutions of Einstein-Maxwell-Scalar Theory

In this paper, we consider a class of near-extremal solutions of Einstein-Maxwell-scalar theory with electric charge and power law scaling, and study thermodynamics of the theory. By using the universality of the shear viscosity to entropy ratio we fix parameters of the theory and compute entropy, specific heat, free energy, total energy and partition function.     

Preconditined semilinear stochastic singular and hypersingular integral equations

In this paper, three classes of preconditioners are proposed for solving some stochastic integral equations with the weakly singular kernel and the hypersingular kernel. The first and the second class of preconditioners are based on circulant operators, but the third class of preconditioners is based on iterative substructuring. It is proved that substructuring preconditioners can be better than other preconditioners. Also, the spaces of solutions are discussed such that the solutions of these equations are smooth, therefore, we give special Banach spaces for these integral equations. Finally, numerical results which support our theories are presented     

Utilizing interband and intraband processes in QD-SOAs for controlling the light velocity

Physical processes in semiconductor optical amplifiers (SOAs) are discussed for the purpose of controlling the velocity of light. For all-optical networking applications, control of velocity of light at bandwidths greater than 100 Gb/s is required. Using interband and ultra-fast intraband nonlinear processes, including spectral hole burning and carrier heating, present in SOAs enables the control of optical signals ranging from 1 GHz to larger than 1 THz. The rate equations for intraband effects are derived and utilized to control optical signals at THz bandwidth. Both optical and electrical control of phase shifts is obtained. An advance bandwidth product of 10 is achieved by utilizing intraband effects in QD-SOA.     

An all-optical switch/photodetection at 1550 nm,based on a micro-ring resonator array

In this paper, a photodetector based on InGaAs micro-ring resonator array with 5 μm radius, in telecommunication wavelength region has been investigated. Then for the first time to our knowledge, with the change of refractive index due to optical nonlinear effects (such as: Kerr effect, two photon absorption, free carrier dispersion and free carrier absorption), an all-optical switch, based on pump-probe configuration using this photodetector have been proposed. So, the suggested device, will introduce a dual functionality that is important from view point of economically purposes and in term of integration. By numerically solving the light propagation equations, with FDTD and Crank–Nicolson methods, in addition to steady state and transient response, also we have found the frequency response, in both configurations. With increasing reverse bias voltage, and optimizing the free carrier transportation from absorption region, switching frequency can be increased up to 200 GHz. Also by optimal choosing of parameters such as the number of rings and spaces between two adjacent rings and so on, the box-like spectral response of photodetector with high efficiency is achievable.     

Spatial Characteristics of Superconductors and a 3D Hall Microscope for Their Analysis

Technical Physics - Based on Hall probes, a scanning microscope with a survey area of 5 × 5 mm has been developed and used for high-spatial-resolution and sensitivity measurements of the...     

Stereoselective Synthesis of Functionalized 1,3-Dienes in Water

An efficient synthesis of functionalized 1,3‐dienes via one‐pot reactions between dialkyl acetylenedicarboxylates?, 1,3‐dicarbonyl compounds and secondary amines in ?water as the solvent is described. The mild reaction condition high yields and the ?new products are advantages of our method.