In the present paper, we aim to report an ultra-compact AlGaAsκ(3) photonic crystal structure to realize multifunctional logic responses. The properties of the proposed model are numerically investigated with different physical parameters by the 2D-finite difference time domain (FDTD) method. For this purpose, the effect of the geometrical parameters and dielectric materials, including Si and InSb, in the near-infrared region are studied. To obtain dynamical tunability of the proposed model, the effect of the defects is then utilized. Numerical results show that the proposed devices are able to operate as multifunctional logic devices including an AND gate and a demultiplexer. Moreover, the structure has a compact footprint of 8.85  μm×8.85  μm×100  nm. We expect that this theoretical result leads to remarkable applications in photonic integrated circuits, e.g., optical memory.

2D-FDTD simulation of ultra-compact multifunctional logic gates with nonlinear photonic crystal

In this research, an all-optical half-subtractor is designed and simulated using two-dimensional photonic crystals. First, a photonic crystal structure is created using Si rods in the air context to obtain the optical half-subtractor. Afterward, using point and line defects, two waveguides are created for the input and two waveguides are created for the outputs. A high logical value and a low logical value are defined based on the optical power in each port. The FDTD method is used in the simulation of light propagation in the structure. The simulation results show that the designed half-subtractor has high optical power values for logic “1” and low values for logic “0”. The small size of the designed structure is among the advantages of this structure. Moreover, given that this half-subtractor is devoid of ring resonators, it can be used in high-speed integrated optical circuits. Another advantage of the proposed half-subtractor is that the optical powers in the outputs are similar in the high and low optical states.

A novel design of all optical half-subtractor using a square lattice photonic crystals

Designing and simulation of 3-input majority gate based on two-dimensional photonic crystals

In this paper, a new structure for realizing a one-bit half-adder is proposed based on 2D photonic crystals. The proposed structure consists of 25 × 20 hexagonal lattice silicon rods in an ambient of air. The main advantages of this structure are a proper distinct space between “0” and “1” logical states of outputs, and smooth and stable outputs for a long time. These advantages are found to eliminate the error in identification of logical states (i.e., 0 and 1) at outputs. Working at a 1550-nm wavelength band (the most commonly used wavelength in optical communication known as third window), the simplicity of its structure and also integrable size has made this structure very efficacious for being realized as an all-optical logic gate.

A novel structure for realization of an all-optical, one-bit half-adder based on 2D photonic crystals

Photonic crystals are suitable structures for designing various types of optical logic circuits. In this paper, an all-optical comparator is designed and simulated using two-dimensional photonic crystals. A combination of linear and point defects has been used in the proposed structure. The small number of point defects and the use of simple linear defects make this comparator simple design. One of the important features of this comparator is that it uses two outputs to compare the input bits. A small structure is used for the proposed optical comparator. Also, this structure has a delay time of 0.07 ps, which is due to the very small size of the structure and the use of a small number of defects. The simulation results show that the bit rate for the proposed comparator is 3.33 Tb/s. Therefore, this structure can be suitable for use in high-speed logic circuits.

Ultra-compact terahertz all-optical logic comparator on GaAs photonic crystal platform

In this paper, an ultra-compact structure is presented for realization of all-optical NOT and XOR logic gates which can be compatible with silicon technology. Logic gates are based on two-dimensional photonic crystals, and the lattice constant and the radius of the rods are selected in such a way in order to operate the logic gates at 1550 nm. The proposed structure consists of three waveguides which are connected to each other using a T-shaped junction. This structure is optimized by two nano-resonators and has also two input ports and one output port. For our numerical studies, the plane-wave expansion and finite-difference time-domain methods have been used. The contrast ratios for the proposed all optical NOT and XOR logic gates are respectively 43.40 and 43.38 dB. The response time of the logic gates is 0.37 ps, which in turn creates a data transmission rate of 3.15 Tb/s. Our studies have shown that the NOT-designed logic gate is suitable for the use in optical integrated circuits.

Realization of all-optical NOT and XOR logic gates based on interference effect with high contrast ratio and ultra-compacted size

Using a two-dimensional photonic crystal lattice, a compact and simple structure has been introduced in the present study to construct an all-optical half adder. The designed structure operates under the interference effect. The phase difference has been created in different states by putting the point defects and the difference in the length of the input waveguides. To do analyses, the finite-difference time-domain method and the plane wave expansion have been used. The advantages of this design include the small dimensions, high possibility of construction, compatibility with the silicon-based technology, and equality of the output power in the logic states 0 and 1. The contrast ratio calculated for the port Sum and the port Carry has been equal to 9.3 and 8.22 dB. The response time has been equal to 0.22 ps, generating the data transfer rate of 4.55 Tbps.

Mostafa Sardari

Papers

Realization of all-optical NOT and XOR logic gates based on interference effect with high contrast ratio and ultra-compacted size

Ultra-fast and compact all-optical half adder using 2D photonic crystals