Abstract
Digital encoders are one of the key devices required in optical communication and digital signal processing systems. In this paper, a new photonic crystal structure is used to design all-optical 4 × 2 encoder constructed from GaAs rods with square lattice in the pentane background based on plasmonic effect. Gold rods have also been used at the interface of dielectric rods and lines defect, which create plasmonic properties into the photonic crystal structure. The designed optical device is composed of four input waveguides and two output waveguides with two ring resonators at the resonant wavelength of 1.14 μm with TM polarization. The presented encoder platform has the small size of 19 μm × 33 μm that makes it to integration into compact all-optical processing systems. The encoder operation is simulated and analyzed with numerical finite-difference time-domain (FDTD) method and plane wave expansion (PWE) method. In the proposed structure, we have shown that by selecting the appropriate radius size for the resonant cavities, the desirable wavelength can be obtained. The maximum values of transmission efficiency for the first and second outputs are 82% and 96%, respectively. Resonant cavities are also located in the crystal lattice in such a way that by activating third input, 50% and 48% of the input signal will be obtained in each output ports indicating (1,1) logic state. So the new plasmonic photonic crystal encoder could be future applicable in the field of optical computing.
Highlights
In the future, with the development of high speed and high capacity telecommunication systems, electronic integrated circuits will be replaced by optical integrated circuits
The results of the some works have shown that the use of plasmonic in photonic crystal structures leads to more light trapping in the line defects and less dimension of devices [39,40,41,42]
A digital all optical 4×2 encoder based on 2D plasmonic photonic crystal using novel defective structures was proposed
Summary
With the development of high speed and high capacity telecommunication systems, electronic integrated circuits will be replaced by optical integrated circuits. Mehdizadeh designed a 4-to-2 optical encoder based on photonic crystals with OR gate [28]. The plasmonic nanostructures have unique features of metallic layers on the dielectric elements with the dimension lower than the coupling wavelength[33]. The results of the some works have shown that the use of plasmonic in photonic crystal structures leads to more light trapping in the line defects and less dimension of devices [39,40,41,42]. A lot of researchers have designed all optical encoder based on photonic crystal structure but none of them have used plasmonic effect. A 4×2 encoder based on 2D photonic crystal structure using plasmonic effect in a new defect line architecture is designed for the first time.
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