Coupler-apodized Bragg-grating add–drop filter

We demonstrate an apodization technique using tapered coupler gaps in grating-assisted asymmetric couplers, which circumvents the need for tapered waveguide perturbations and enables a higher tolerance to fabrication errors. A high sidelobe suppression ratio of 30 dB has been obtained on the submicrometer silicon-on-insulator platform using a CMOS-compatible photonics process with 193 nm lithography.