Abstract

The application of integrated optical devices in many communication or signal processing systems will require efficient coupling between single­mode optical fibers and channel waveguides. Although high coupling efficiencies have been predicted, their realization in a practical configuration has remained elusive, primarily due to the extremely stringent alignment tolerances involved. In this presentation, we will report an improved version of the Si V-groove/flip-chip coupler,¹ in which tapered alignment fibers² are used to achieve precise vertical positioning of the coupling fibers. We have found this approach to routinely provide near theoretical (> 70%) coupling efficiencies between single-mode fibers and Ti diffused LiNbO₃ channel waveguides. The coupler is compact, can be made rigid, and allows for simultaneous multiple coupling on a single chip. Finally by choosing propagation directions along the LiNbO₃ major axes, we avoid anisotropic effects³ and achieve coupling efficiences and propagation losses essentially independent of input optical polarization.

© 1980 Optical Society of America