Multiple fiber end fire coupling with single-mode channel waveguides

Abstract

We demonstrate a practical four-port flip chip end fire coupler useful for providing efficient coupling between single-mode fibers and Ti-diffused LiNbO3 channel waveguides. Channel waveguide ends were prepared for coupling by cleavage. With a configuration suitable for multiple fiber coupling, coupling efficiencies up to 47% have been measured for TM polarization. Using micropositioners to align single input and output fibers with respect to the channel waveguide, end fire coupling efficiency was 58% (TM). The effect of waveguide mode mismatch and misalignment on coupling efficiency is investigated. We also observe double refraction and leaky mode propagation with TE polarized input to LiNbO3 channel waveguides running perpendicular to the cleavage plane. With suitably prepared channel waveguides on LiTaO3, these effects are small or absent.