Efficient coupling of hybrid optical waveguide with a sharp bend structure for high integration

Abstract

A hybrid optical waveguide with a \(90^{\circ }\) sharp bend comprising a dielectric straight waveguide, a tapered dielectric strip waveguide, and a microscale metal gap waveguide is proposed, modeled, fabricated, and characterized with the aim of improving the efficiency of light coupling between the dielectric and plasmonic waveguides. The simulation result using the full-vector finite-difference time domain shows a total transmissivity of about 63 % at a wavelength of 1,550 nm. A set of hybrid optical waveguide with a \(90^{\circ }\) bend is fabricated via the two-step photolithography and a metal lift-off process. From the measured result for the characteristics of the fabricated hybrid optical waveguide, the transmission loss was estimated to be about 17 dB, which is in stark contrast with the simulation value. Nevertheless, such a novel coupling scheme may be of potential use in high-density photonic integration applications.