Ali Bahrami

All-optical photonic crystal AND, XOR, and OR logic gates using nonlinear Kerr effect and ring resonators

In this article, two structures are proposed for all-optical AND, XOR, and OR logic gates based on nonlinear photonic crystals. The proposed structures include a Y-junction and ring resonator-based limiters. Two different structures are designed as the limiter in order to produce AND–XOR and AND–OR logic gates. Nonlinear rods of proposed structure have been used in order to create the frequency shift for different values of input power. Finite difference time domain method has been utilized to simulate the performance of proposed logic gates. Simulation results show that the smallest ON–OFF logic-level contrast ratio for the structures proposed for AND–XOR and AND–OR logic gates are 20.29 dB and 16.7 dB, respectively.

All-Optical Multi-Mode Interference Switch Using Non-Linear Directional Coupler as a Passive Phase Shifter

Abstract This article presents an all-optical multi-mode interference switch in which the non-linear directional coupler is utilized to realize a passive phase shifter. The proposed structure can be used either as a 1 × 2 or a 2 × 2 switch, with two inputs applied simultaneously in the latter case. The operation of the device is mainly based on the phase difference of the inputs of the multi-mode interference section. The beam propagation method is used for the design and simulation of the structure. The simulation results approve the low sensitivity on wavelength and fabrication tolerances. The crosstalk of the structure is equal to −31.6 dB.

MMI-Based Simultaneous All-Optical XOR–NAND–OR and XNOR–NOT Multilogic Gate for Phase-Based Signals

We propose a novel design to simultaneously access various optical logic functions from different output ports. Logical values of inputs and outputs are defined in phase and intensity area of light, respectively. The proposed structure is composed of one multimode interference waveguide with the ultrasmall size of 2.5 μm × 21 μm. Three output ports of proposed structure offer XOR, NAND, and OR logic functions. In addition, XNOR and NOT logic gates are realized by considering some changes in the conditions. Beam propagation method has been utilized to accomplish the simulations of light propagation. Simulation results of structure in whole C-band show that the maximum insertion loss is -0.14 dB and the least contrast ratio achieved for XOR, NAND, OR, XNOR, and NOT logic functions are 26, 24.7, 25.9, 26, and 25 dB, respectively.

EIT-based MZ-MMI all-optical switch

We propose a new control structure for all-optical switching in multimode inference (MMI)-based Mach–Zehnder interferometer (MZI) devices. This structure is composed of an MZI doped by three-level nanocrystals for the realization of electromagnetically induced transparency (EIT) in the lower arm. We use two different intensities of control field for two states of the proposed switch. Using a control field in both of the two switching states is necessary, where the EIT region is transparent. By changing the intensity of the control field, the refractive index of the doped region changes, which makes the phase difference between the two arms of the MZI. Hence, the switching operation takes place. Simulation results show that the extinction ratio of the device is −32dB in the worst case.

Design of all-optical simultaneous AND, NAND, OR, and NOR logic gates using phase-based control of three coupled waveguides

In this paper, we present a novel phase-based structure for implementing the all-optical multi-function logic gates. The proposed structure which is composed of three coupled waveguides allows us to simultaneously access OR/NOR and AND/NAND logic functions from different output ports. The phase of middle waveguide plays the role of control tool which defines the logical values of outputs. The output ports can be switched from OR/NOR to AND/NAND logic functions by changing the control phase from 24

Modified-DBR-based semi-omnidirectional multilayer anti-reflection coating for tandem solar cells

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A Novel proposal for DWDM demultiplexer design using resonance cavity in Photonic Crystal structure

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