Abstract

The design of many proposed integrated optical circuits containing elements such as branching networks and device interconnections require complicated low-loss waveguide bends. We report here new experimental results on very low-loss coherently-coupled^1,2 bends in single-mode Ti-diffused LiNbO₃ channel waveguides which in conjunction with further analysis of earlier measurements³ now allow us to establish a set of design rules for these structures. These bends consist of successions of straight, angled waveguide sections which approximate smoothly-curved bends and are particularly useful since they are compatible with conventional photomask pattern generators. The design rules are qualitatively similar to a set previously reported⁴ for bend structures consisting of straight and circular waveguide sections. Losses due to curvature reversals, straight-curved transitions, and curvature alone were considered. It is found in our work that a significant portion of the loss in complicated coherently-coupled bend structures is due to curvature reversal and that the loss of a single coupled 1° abrupt bend can be as low as ≈0.085 dB.

© 1982 Optical Society of America