DESIGN OF ALL-OPTICAL LOGIC GATES USING NAND GATE IN PHOTONIC CRYSTAL WAVEGUIDES

Abstract

In this thesis, we have proposed the design of all-optical logic gate using the combination of universal NAND gates. The structure consists of hexagonal arrangement of air holes in silicon having a refractive index of 3.5. The radius of air holes has been taken as 0.3a, where ‘a’ is the lattice constant. The NAND gate has two input ports, one reference port and one output port. Initially, a single NAND gate structure has been optimized with a hole of radius 0.2a at the junction of all the four waveguides of NAND gate. The bends in the NAND gate have been optimized such that there are minimum bend losses. For this purpose six air holes of radius 0.15a have been placed at outer edge of the waveguide and radius of the inner edge hole has been reduced to 0.17a. Further, the optimized NAND gates that are the universal gates have been arranged in a combination such that the combined structure behaves as an all-optical logic gate. The proposed structure exhibits a response period of 6.48ps and bit rate of 0.154 Tb/sec. Thus, we have designed the all-optical logic gate with the help of universal NAND optical logic gate.