Design and Analysis of a Novel Air Gap–Based Semi-elliptical Nanoplasmonic Coupler

Abstract

Efficient coupling of light between the dielectric waveguide and plasmonic waveguide has been investigated theoretically in three dimensions. An air gap-based novel nanoplasmonic semi-elliptical structure of silicon (Si) is used as a coupler, which connects these waveguides. Finite integration technique (FIT) has been deployed for the investigation. Theoretical coupling efficiency of ∼85% at optical communication wavelength (1.55 μm) has been achieved through numerical simulations. The dependency of coupling efficiency has been investigated by varying the curvature of the semi-elliptical coupler, the air gap width between the two waveguides and the width of the air gap of silver-air-silver waveguide, and an optimal dimension of the proposed structure has been determined. A number of performance parameters like coupling efficiency, reflection coefficient, return loss, and voltage standing wave ratio (VSWR) have been analyzed with the obtained optimal dimensions. Broad range of operating frequency, tolerance to coupler thickness, angular, and air gap misalignment, and excellent agreement to a demonstrated experimental coupler has made the proposed coupler distinctive.