Coupling methods in prospective single-mode fiber integrated optics systems: A progress report

Publisher Website
Google Scholar
Abstract
A review of the research progress on the coupling of fibers to fibers, fibers to thin-film waveguides, and thin-film waveguides to thin-film waveguides is presented here. In general, the direct excitation method is preferred for the coupling of two fibers, with efficiency larger than 90%. The direct excitation method is also preferred for the coupling of two thin-film waveguides and thin-film waveguides to fibers where the two component waveguides have vastly different refractive indices. The coupling efficiency depends on matching the field pattern of component waveguides. The laser source to fiber launching is done mostly by direct excitation. The evanescent field coupling method is preferred for the coupling of two thin-film waveguides that have close refractive index profiles, with efficiency larger than 70%.