Modal field transforming fiber between dissimilar waveguides

Abstract

A fiber mode matching device between dissimilar optical waveguides is proposed and fabricated. The device has a refractive index profile that varies in the direction of propagation without changing the normalized frequency. We fabricated a single-mode tapered fiber with a rectangular core at one end and a circular core at the other. The modal field transformer is expected to allow highly efficient coupling between dissimilar waveguide devices.