Sidelobe suppression in grating-assisted wavelength-selective couplers

This study proposes and implements an analysis of sidelobe suppression by means of a tapered duty ratio in a phase-matched grating for a vertical codirectional coupler. With a truncated Gaussian taper assumed, the results of this study show that a cross-talk level of lower than -40 dB in a channel spacing of 5 nm is feasible with a 1-mm coupling length at 830 nm. The results also reveal that 20 intervals are sufficient to allow a quantized taper to attain highly suppressed sidelobes.