Design improvement of nanophotonic combinational logic device for Tbps signal processing

Plasmonic circuits offer a promising solution to the miniaturization and diffraction-limit challenges of photonic devices. In this work, a Nano-ring Dielectric–Metal–Dielectric (DMD) plasmonic waveguide is proposed to design, simulate, and implement seven all-optical combinational logic functions at a wavelength of 1,550 nm using a single compact architecture. The implemented functions include a half-adder, full-adder, half-subtractor, full-subtractor, multiplexer, demultiplexer, and comparator. The proposed circuits were modeled and analyzed using COMSOL Multiphysics based on the Finite Element Method (FEM). The design offers several advantages, including ultra-compact dimensions of 400 nm × 840 nm, low response time, high transmission efficiency, and operation at terabit-per-second data rates. A logic threshold of 0.4 was used to distinguish between logic states 0 and 1. Device performance was evaluated using 20 parameters, with particular emphasis on transmission (T), contrast ratio (CR), modulation depth (MD), and insertion loss (IL). Simulation results demonstrate excellent performance, achieving a maximum transmission efficiency of 205 %, a maximum bit rate of 33.714 Tbps, and a response time as low as 44.5 fs. In addition, most combinational logic functions exhibit a modulation depth of approximately 99.8 %, highlighting the suitability of the proposed structure for future nanophotonic integrated circuits and high-speed optical signal processing applications.