An investigation on the cascaded operation of photonic crystal based all optical logic gates and verification of De Morgan’s law

In this paper, a new set of configurations are proposed to implement simple and highly compact photonic crystal based all-optical logic AND and OR gates. These newly designed logic gates operate at the telecommunication wavelength of 1550 nm and consume very low power compared to the existing designs. The basic all-optical logic gates are cascaded to operate as the universal gates NAND and NOR. The various parameters such as response time, contrast ratio and footprint are analyzed and optimized based on structure parameters such as radius and lattice constant. The proposed structures have very low power consumption in the range of 1 μ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu$$\end{document}W with a footprint of 168 μm2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu \mathrm{m}^2$$\end{document} for the AND gate and 150 μm2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu \mathrm{m}^2$$\end{document} for the OR gate respectively. The value of contrast ratio for the proposed AND gate is 8.45 dB. The response time for OR gate is 0.4 ps and that of AND gate is 0.16 ps resulting in bitrates up to 6.25 Tbps. The contrast ratio obtained for the cascaded operation of NAND and NOR gates are 5.29 dB and 5.3 dB respectively. The band gap diagram for the proposed gates are attained using Plane Wave Expansion method and their performance is studied using Finite Difference Time Domain technique. Further, the realization of De Morgan’s law is achieved by cascading the proposed all-optical logic gates and hence verifying the truth tables for the same.