Design algorithm for compact low-reflection adiabatic photonic mode converters based on constant coupling

Coupling light between optical components with different waveguide geometries on photonic integrated circuits have become an imperative function for many applications. Herein, we propose an algorithm for the design of low-reflection adiabatic optical components using a constant coupling approach. Low reflectivity is important for optical components that are in close proximity to semiconductor optical amplifiers, where a reflectivity of less than-50 dB is required. We apply the algorithm to a polarization mode converter on the silicon-on-insulator platform, where we reduce the back reflection from-41 dB to-58 dB. We also show the tradeoff between the reduction in the reflected power and the resulting device length.