Controlling coupling of guided to radiating modes using adiabatic transitions between waveguides of different curvature

A simple method for designing adiabatic transitions between straight and curved waveguides is presented. This method results in lower coupling from guided to radiating modes than conventional methods based on introducing an abrupt offset at the junction point. With the new adiabatic transition design, a decrease of 5 to 10 dB in the low-level radiating light cone is found compared with the traditional method.