Insights from a systematic study of crosstalk in adiabatic couplers

We investigate how the performance of an adiabatic coupler depends on the detailed coupler properties. After verifying the accuracy of an analytic expression for the fraction of energy that is not coupled into the desired waveguide (i.e., the crosstalk), we consider how the center and the ends of adiabatic couplers contribute to the total crosstalk. We find that for short coupler lengths the center dominates, whereas for longer devices the two ends dominate.