Asghar Askarian

In the present work, nonlinear ring resonator based on two-dimensional hexagonal photonic crystal structure is designed for all optical OR and NOR gates in the wavelength range of 1355–2053 nm. The OR and NOR gates are made up of four optical waveguides which are critically coupled to a nonlinear ring resonator. The electric field distribution and photonic band gap characteristic of the proposed gates are solved by Maxwell equations using finite difference time domain and plane wave expansion methods, respectively. Simulation results by finite difference time domain approach show the minimum contrast ratio of 12.04 and 11.81 dB for OR and NOR logic gates, respectively. Also, the minimum delay time is obtained 1 ps for OR and 1.5 ps for NOR logic gates.

In optical processing systems, multiplexer is used to design optical devices such as arithmetic logic unit (ALU) and shift register (SR). Through this paper, we investigate the application of nonlinear photonic crystal ring resonator (PhCRR) based on nonlinear Kerr effect for realizing an all optical 2 × 1 multiplexer. The structure consists of two PhCRRs and five optical waveguides using hexagonal lattice silicon (Si) rods with a background of air. Performance of all optical 2 × 1 multiplexer is replicated with the help of finite difference time domain (FDTD) procedure at a wavelength of 1571 nm, and simulations presented an ultra-compact optical structure with ultra-fast switching speed.

In this work, the authors investigate the new structure of all optical half subtractor in a two dimensional photonic crystal based on wave interference and phase shift keying technique. The suggested structure is designed using 10 optical waveguides and one defect in the basic structure. The numeral methods such as plane wave expansion and finite difference time domain are used to analyze the proposed structure. According to obtained results, the rise and fall times, the working bit rate, the minimum and maximum values of the normalized power at ON and OFF states for output ports are 0.1 ps, 0.05 ps, 5 Tbit/s, 77 and 17%, respectively. According to results, high switching speed, compactness, low power consumption and ultra-fast operation are the main advantages of designed optical half subtractor compared with the previous structures.

Image registration is the process of overlaying two or more images of a specific scene which are captured at different times, from different perspectives or using different sensors. Automatic registration of optical images to SAR images is challenging because of the non-compatibility of radiometric and geometric features. The current study developed a novel feature matching method for automatic optical to SAR image registration that employs feature-guided coherent spatial mapping (FG-CSM). The feature considers a set of assumptive points of optical images and SAR with similar features (using a standard SIFT algorithm). It also removes outlier points from the corresponding assumptive set and estimates the transform. The thin plate spline is used to parameterize the coherent spatial mapping and the problem is solved under a unified maximum-likelihood framework together with an iterative expectation maximization algorithm initialized by a similar feature. Compared to previous methods, the proposed algorithm is able to provide more accurate registration with many outlier points.