Low crosstalk and high extinction ratio all-optical 4 × 2 encoder based on metal–insulator–metal plasmonic waveguides

Abstract

This paper presents an all-optical 4 × 2 encoder based on metal–insulator–metal (MIM) waveguides, designed for operation across a wide wavelength range of 1–2 μm. The MIM waveguides consist of SiO₂ dielectric strips sandwiched between layers of silver metal. The encoder incorporates a straight waveguide to detect the state of the In₀ input. Additionally, it includes one splitter and two combiners with outputs Out₀ and Out₁ for detecting the states of the In₁, In₂, and In₃ inputs. A key innovation in this work is the distance created between the splitter and combiners, which allows for tuning and improving the encoder output characteristics. The proposed encoder was simulated using the finite-difference time-domain method. It demonstrates a minimum extinction ratio of 11.65 dB and a crosstalk level of − 15.65 dB at a wavelength of 1550 nm. The total footprint of the encoder is less than 8 μm². Our research indicates that a 4 × 2 encoder utilizing MIM waveguides has not been previously reported. Given its straightforward fabrication process, high extinction ratio, and low crosstalk, the suggested encoder is a promising candidate for a wide range of plasmonic communication and signal-processing applications.